摘要:

THE ROYAL SOCIETY OF CHEMISTRY Journal of Materials Chemistry Scientific Editor Staff Editor Professor Anthony R. West Mrs. Janet M. Leader Department of Chemistry The Royal Society of Chemistry University of Aberdeen Thomas Graham House Meston Walk Science Park Aberdeen AB9 2UE, UK Cambridge CB4 4WF, UK Assistant Editor: Mrs. F. J. O'Carroll Editorial Secretary: Miss D. J. Halls Graphics Designer: Ms. C. Taylor- Reid Materials Chemistry Editorial Board Anthony R. West (Aberdeen) (Chairman) Peter G. Bruce (St. Andrews) H. Monty Frey (Reading) C. Richard A. Catlow (London) John W. Goodby (Hull) David A. Dunmur (Sheffield) Brian J. Tighe (Aston) Jean Etourneau (Bordeaux) Allan E. Underhill (Bangor) Wendy R. Flavell (UMIST) John D.Wright (Canterbury) ~~~~~~~~ ~ ~ ~ ~ ~ ~~ ~ ~ ~ ~ ~ ~ ~~~~~ Internationa I Advisory Ed itoria I Board M. A. Alario-Franco (Madrid, Spain) A. J. Leadbetter (Daresbury, UK) K. Bechgaard (Copenhagen, Denmark) J. S. Miller (Wilmington, DE, USA) J. D. Birchall (Runcorn, UK) P. S. Nicholson (Hamilton, Canada) D. Bloor (Durham, UK) M. Nygren (Stockholm, Sweden) A. K. Cheetham (Santa Barbara, USA) V. Percec (Cleveland, OH, USA) E. Chiellini (Pisa, Italy) N. Plate (Moscow, Russia) P. Day (London, UK) C. N. R. Rao (Bangalore, India) B. Dunn (Los Angeles, USA) M. Ratner (Evanston, IL, USA) W. J. Feast (Durham, UK) J. Rouxel (Nantes, France) A. Fukuda (Tokyo, Japan) R. Roy (University Park, PA, USA) D. Gatteschi (Florence, Italy) J.L. Serrano (Zaragoza, Spain) J. B. Goodenough (Austin, TX, USA) J. N. Sherwood (Glasgow, UK) A. C. Griffin (Hattiesburg, USA) J. Simon (Paris, France) S-i. Hirano (Nagoya, Japan) J. F. Stoddart (Birmingham, UK) P. Hodge (Manchester, UK) S. Takahashi (Osaka, Japan) H. lnokuchi (Okazaki, Japan) G. J. T. Tiddy (Bebington and Salford, W. Jeitschko (Munster, Germany) UK) 0. Kahn (Orsay, France) Yu. D. Tretyakov (Moscow, Russia) M. Lahav (Rehovot, Israel) J. W. White (Canberra, Australia) R. Xu (Changchun, China) Journal of Materials Chemistry (ISSN 9959-9428) is published monthly by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, UK. All orders accompanied with payment should be sent directly to The Royal Society of Chemistry, Turpin Distribution Services Ltd., Blackhorse Road, Letchworth, Herts SG6 1 HN, UK.NB Turpin Distribution Services Ltd., distributors, is wholly owned by The Royal Society of Chemistry. 1994 Annual subscription rate EC (inc. UK) f381.00, USA $718.00, Canada €431 .OO (plus GST), Rest of World f410.00. Customers should make payments by cheque in sterling payable on a UK clearing bank or in US dollars payable on a US clearing bank. Air freight and mailing in the USA by Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003. USA POSTMASTER: send address changes to Journal of Materials Chemistrx Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003. Second Class postage paid at Jamaica, NY 11 431.All other dispatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outside Europe. PRINTED IN THE UK. @ The Royal Society of Chemistry, 1994. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form, or by any means, electronic, mechanical, photographic, recording, or otherwise, without the prior permission of the publishers. Professor A. R. West, Scientific Editor Mrs. J. M. Leader, Staff Editor Tel.: Aberdeen (0224) 27291 8 Tel.: Cambridge (0223) 420066 Fax: (0224) 272938 E-Mail (INTERNET): Telex: 73458 UNIABN G RSCl @RSC.ORG Fax: (0223) 420247 or 423623 Telex: 818293 ROYAL G Advertisement sales: Tel. + 44 (0)71-287 3091; Fax +44 (0)71-494 11 34 INFORMATION FOR AUTHORS The Royal Society of Chemistry welcomes submission of manuscripts intended for pub- lication in two forms, Articles and Materials Chemistry Communications.These should describe original work of high quality dealing with the synthesis, structures, properties and applications of materials, particularly those associated with advanced technology. Articles Full papers contain original scientific work that has not been published previously. How- ever, work that has appeared in print in a short form such as a Materials Chemistry Com- munication is normally acceptable. Four copies of Articles including a top copy with figures etc. should be sent to The Editor, Journal of Materials Chemistry, The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB44WF.UK. Materials Chemistry Communications Materials Chemistry Communications contain novel scientific work in short form and of such importance that rapid publication is war-ranted. The total length is rigorously restric- ted to two pages of the double-column A4 format. The manuscript will be returned for reduction if this length is exceeded. For a Communication consisting entirely of text and ten references, with no figures, equations or tables, this corresponds to approximately 1600 words plus an abstract of up to 40 words. Submission of a Materials Chemistry Com- munication can be made either to The Editor, Journal of Materials Chemistry, The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, UK, or via a member of the Inter- national Advisory Editorial Board.In the latter case, the top copy of the manuscript includ- ing any figures etc., together with the name of the person to whom the Communication is being submitted, should be sent simul-taneously to the Editor at the Cambridge address. Authors may wish to contact the Board member to ensure that he is available to arrange review of the manuscript within reasonable time. In order to avoid delay in publication, proofs of Communications are not sent to authors unless this is specifically requested. Full details of the form of manuscripts for Articles and Materials Chemistry Communi- cations, conditions for acceptance etc. are given in issue number one of Journal of Materials Chemistry published in January of each year, or may be obtained from the Staff Editor. There is no page charge for papers published, in Journal of Materials Chemistry. Fifty reprints are supplied free of charge. Any author who is publishing in Journal of Materials Chemistry is entitled to a free copy of the issue in which the paper appears.

ISSN:0959-9428    

DOI:10.1039/JM99404FX009

出版商:RSC    

年代:1994

数据来源: RSC

ISSN:0959-9428    

DOI:10.1039/JM99404BX011

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

ISSN 0959-9428 JMACEP(3) 367-499 (1994) Journal of Materials Chemistry Synthesis, structures, properties and applications of materials, particularly those associated with advanced technology The first seven papers in this issue were submitted in association with the 1st International Conference on Materials Chemistry held in Aberdeen in July 1993. CONTENTS 367 Nanocomposite materials: Polyaniline-intercalated layered double hydroxides T. Challier and R. C. T. Slade 373 Composite materials based on Ti and Ru oxides M. I. Ivanovskaya, V. V. Romanovskaya and G. A. Branitsky 3 79 Preparation and characterization of imidazole-metal complexes and evaluation of cured epoxy networks J. M. Barton, G. J. Buist, I. Hamerton, B. J. Howlin, J. R. Jones and S. Liu 385 Kinetic and simulation studies of linear epoxy systems I.P. Aspin, J. M. Barton, G. J. Buist, A. S. Deazle, I. Hamerton, B. .1. Howlin and J. R.Jones 389 Pyrochlore-like compounds derived from antimonic acid A. J. G. Zarbin and 0.L. Alves 393 Silicon-germanium films for photomasking applications C-W. Liu, J. A. Cairns, R.A. G. Gibson, A. C. Hourd, B. Lawrenson and C. F. Leece 399 Synthesis of QMD and QD polyorganosiloxanes from tetrakis( trimethylsi1oxy)silane and palabora vermiculite J. E. Connell, D. ap Kendrick, G. Marks, J. R. Parsonage, M. J. K. Thomas and E. A. Vidgeon 407 High-purity WO, Sol-gel coatings: Synthesis and characterization L. Armelao, R. Bertoncello, G. Granozzi, G. Depaoli, E. Tondello and G. Battaglin 413 Thermal expansion of hot isostatically pressed hydroxyapatite 0.Babushkin, T.Lindback, A. Holmgren, J. Li and L. Hermansson 417 Influence of ionic substitution on the magnetic behaviour of Y2Cu,0, Q. Su, X.Cao and H. Wang 42 1 Mixed oxides of SbV as catalysts for the oxidative coupling of methane P. D. Battle, S. W. Carr, F. A. Copplestone and R. S. Mellen 429 Semiflexible liquid-crystalline polyesters based on twin bis( p-oxybenzoyl) units Part 1.-Effect of spacer length on mesomorphic behaviour G. Galli, E. Chiellini, M. Laus, A. S. Angeloni and M. C. Bignozzi 437 Semiflexible liquid-crystalline polyesters based on twin bis(p-oxybenzoyl) units Part 2.-Effect of molar mass on mesomorphic behaviour M. Laus, A. S. Angeloni, A. Spagna, G. Galli and E. Chiellini 445 Synthesis and crystal structure of Li,NaTa,O,, J.Grins, L. Baiios, D. C. Sinclair and A. R. West 449 Mesophasic helical structures with high twisting power in optically active 3-methyladipic acid bis esters A. Yoshizawa and I. Nishiyama 457 Polymorphism and crystal chemistry of Li,,,Ga,,,GeO,, an Li3P04 Analogue A. D. Robertson and A. R.West 463 Crystal structure of the ternary siiicide U,RuSi,: A new ordered version of the hexagonal A1B2-type structure R.Pottgen, P. Gravereau, B. Darriet, B. Chevalier, E. Hickey and J. Etourneau 469 Selection of appropriate systems for flux growth of single-crystal YBa,Cu,O,-, C. Chen, J. W. Hodby, Y. Hu and B. M. Wanklyn 475 Quaternary uranium copper oxides: The structure and properties of UBa,CuO, M. D. Marcos and J.P. Attfield 479 Mesomorphic complexes of silver trifluoromethanesulfonate and silver dodecylsulfate with 2-and 3-fluoro-4-alkoxy-4-stilbazoles D. W. Bruce and S. A. Hudson 487 Surface studies of polyethylene modified by flame treatment E. Sheng, I. Sutherland, D. M. Brewis, R.J. Heath and R. H. Bradley 491 Controlled combustion synthesis and properties of fine-particle NASICON materials N. A. Dhas and K. C. Patil 499 Book Reviews Van Grieken; Sundholm 1 Cumulative Author Index 1994 11 Conference Diary Note: Where an asterisk appears against the name of one or more authors, it is included with the authors’ approval to indicate that correspondence may be addressed to this person. COPIES OF CITED ARTICLES The Royal Society of Chemistry Library can usually supply copies of cited articles. For further details contact: The Library, Royal Society of Chemistry, Burlington House, Piccadilly, London W1V OBN, UK. Tel: +44 (0)71-437 8656, Fax: +44 (0)71-287 9798, Telecom Gold 84: BUR210, Electronic Mailbox (Internet) LIBRARY@RSC.ORG. If the material is not available from the Society’s Library, the staff will be pleased to advise on its availability from other sources. Please note that copies are not available from the RSC at Thomas Graham House, Cambridge.

ISSN:0959-9428    

DOI:10.1039/JM99404FP027

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

Cumulative Author Index 1994 Abrahams I., 185 Akimoto H., 61 Aksay I. A., 353 Ah-Adib Z., 1 Aliev A. E., 35 Alves 0. L., 389 Angeloni A. S., 429, 437 ap Kendrick D., 39') Arai K., 275 Armelao L., 407 Armigliato A., 361 Arnold Jr. F. E., 105 Asaka N., 291 Aspin 1. P., 385 Attfield J. P., 475 Auroux A., 125 Azuma K., 139 Baba A., 51 Babu G. P., 331 Babushkin O., 413 Bach S., 133 Bachir S., 139 Badwal S. P. S., 2C7 Baetzold R. C., 290 Baffier N., 133 Baiios L., 445 Barton J. M., 379, 385 Battaglin G., 407 Battle P. D., 421 Bautista F. M., 31 1 Bertoncello R., 407 Chevalier B., 463 Chiellini E., 429, 437 Ciacchi F. T., 257 Coles G. S. V., 23 Connell J. E., 399 Conroy M., 1 Conway L. J., 337 Cook M. J., 209 Cook S. L., 81 Copplestone F. A., 421 Darriet B., 463 Davidson I.M. T., 13 Davies A,, 113 Deazle A. S., 385 del Arc0 M., 47 Dennison S., 41 Depaoli G., 407 Dhas N. A., 491 Diamond D., 145, 217 Drabik M., 265, 271 Drennan J., 245 Eda K., 205 Eldred W. K., 305 Ellis A. M., 13 Etourneau J., 463 Fitzmaurice J. C., 285 Fleming R. J., 87 Fraoua K., 305 Frialova M., 271 Fujimoto T., 61 Fukuda A., 237 Galikova f,., 265, 271 Hodby J. W., 469 Hodge P., 1 Holmes P. A., 365 Holmgren A,, 413 Hourd A. C., 393 Howlin B. J., 379, 385 Hu Y., 469 Hudson M. J., 99, 113 Hudson S. A., 479 Hughes A. E., 257 Huxham I. M., 253 Imanishi N., 19 Imayoshi K., 19 Inada H., 171 Islam M. S., 299 Isoda S., 291 Isozaki T., 237 Ivanovskaya M. I., 373 Jimenez R., 5 Jimenez-Lopez A., 179 Jones D. J., 189 Jones J. R., 379, 385 Jung K., 161 Kassabov S., 153 Katsoulis D.E., 337 Kawamura I., 237 Kennedy B. J., 87 King T., 1 Klissurski D., 153 Knowles J. C., 185 Kobayashi T., 291 Lund A., 223 Macklin W. J., 113 Mahgoub A. S., 223 Maireles-Torres P., 179, 189 Malet P., 47 Marcos M. D., 475 Marinas J. M., 311 Marks G., 399 Matsuda H., 51 Maza-Rodriguez J., 179 McCarrick M., 217 McGhee L., 29, 119 McMeekin S. G., 29, 119 Mellen R. S., 421 Metcalfe K., 331 Mills G. P., 13 Morpurgo S., 197 Murray K. S., 87 Nakano H., 171 Neal G. S., 245 Neat R. J., 113 Nicol I,, 29 Nishiyama I., 449 Nomura R., 51 Nomura S., 171 Ohnishi K., 171 Ohta K., 61 Olivera-Pastor P., 179 Pareti L., 361 Parkin I. P., 279, 285 Parsonage J. R., 399 Patil K. C., 491 Sheng E., 487 Sheridan P., 161 Sherrington D. C., 229, 253 Shimokawatoko T., 51 Shirota Y., 171 Simon M., 305 Sinclair D.C., 445 Slade R. C. T., Smart S. P., 35 Smith E. G., 331 Smith J. M., 337 Smith M. E., 245 Snetivy D., 55 Solzi M, 361 Sotani N., 205 Spagna A., 437 Styring P., 71 Su Q., 417 Suckut C., 5 Sundholm F., 499 Sutherland I., 487 Suzuki Y., 237 Swindell J., 229 Taga T., 291 Takano M., 19 Takeda Y., 19 Takezoe H., 237 Tetley L., 253 Thomas M. J. K., 399 Thomson J. B., 167 Thorne A. J., 209 265, 367 Beveridge M., 119 Galli G., 429, 437 Kohmoto T., 205 Pennington M., 13 Tian M., 327 Bigi S., 361 Bignozzi M. C., 429 Bond S. E., 23 Bradley R. H., 487 Branitsky G. A., .;73 Brewis D. M., 48' Britt S., 161 Brock T., 229 Bruce D. W., 479 Bruce P. G., 167 Bryant G. C., 209 Buist G. J., 379, 385 Cairns J. A., 393 Campelo J. M., 311 Caneschi A., 319 Cao X., 417 Carlino S., 99 Carr S.W., 421 Carrazan S. R. G. 47 Cassagneau T., 189 Cervini R., 87 Challier T., 367 Chehimi M. M., 305 Ganguli P., 331 Garcia A., 3 11 Gatteschi D., 319 Gee M. B., 337 Gibson R. A. G., 393 Gil-Llambias F-J., 47 Glomm B., 55 Goodby J. W., 71 Granozzi G., 407 Gravereau P., 463 Grins J., 445 Guo Z., 327 Hamerton I., 379, 385 Harris F. W., 105 Harris K. D. M., 35 Harris S. J., 145, 217 Haslam S. D., 209 Hatayama F., 205 Heath R. J., 487 Hector A. L., 279 Hermansson L., 413 Hickey E., 463 Higuchi A., 171 Hirose N., 9 Kossanyi J., 139 KouyatC D., 139 KriStofik M., 271 Kubono K., 291 Kubranova M., 265 Kunitomo M., 205 Kuwano J., 9 Lahti P. M., 161 Landee C., 161 Laus M., 429, 437 Lawrenson B., 393 Leece C. F., 393 Lefebvre F., 125 Le Goff P., 133 le Lirzin A., 319 Li J., 413 Lightfoot P., 167 Lindback T., 413 Lindgren M., 223 Little F.J., 167 Liu C-W., 393 Liu S., 379 Liu-Cai F. X., 125 Pereira-Ramos J-P., 133 Perez-Jimenez C., 145 Porta P., 197 Pottgen R., 463 Povey I. M., 13 Predieri G., 361 Raynor J. B., 13 Rhomari M., 189 Richards B. C., 81 Richardson R. M., 209 Rives V., 47 Robertson A. D., 457 Robertson M. I., 29, 119 Rockliffe J. W., 331 Rodriguez-Castellbn E., 179 Romanovskaya V. V., 373 Ronfard-Haret J-C., 139 Ross A., 119 Rowatt B., 253 Rowley A. T., 285 Roziere J., 189 Russell D. K., 13 Ryan T. G., 209 Sano S., 275 Tondello E., 407 Torres-Martinez L. M., 5 Trigg M. B., 245 Urbana M. R., 311 Uzunova E., 153 Vancso G. J., 55 Van Grieken R, 499 Vidgeon E. A,, 399 Wang H., 417 Wanklyn B.M., 469 Watts J. F., 305 Wen J., 327 Wessels P. L., 71 West A. R., West D., 1 Williams G., 23 Winfield J. M., 29, 119 Workman A. D., 13 Yamamoto I., 61 Yamamoto O., 19 Yang H., 55 Yogo T., 353 Yoshizawa A., 449 5, 445, 457 Chen C., 469 Chen Q., 327 Hitchman M. L., 81 Hix G. B., 189 Lo Jacono M., 197 Loubser G., 71 Saydam S., 13 Shamlian S. H., 81 Yu H., 327 Zarbin A. J. G., 389 Cheng S. Z. D., 105 Hobson R. J., 113 Luna D., 311 Shen D., 105 Zhang W-r., 161 i Conference Diary 1994 March 13-16 Third European Federation of Corrosion Workshop on Microbial Corrosion Estoril, Portugal Cesar Sequeira, Instituto Superior TBcnico, Av. Rovisco Pais, 1096 Lisboa Codex, Portugal or A. K. Tiller, Corrosion Centre, 23 Grosvenor Gardens, Kingston upon Thames KT2 5BE, UK or D.Thierry, Swedish Corrosion Insitute, Roslagsvagen 101, Hus 25, S-10405 Stockholm, Sweden March 13-18 1994 ACS National Spring Meeting San Diego, USA ACS International Activities Office, 1155 16th St. NW, Washington DC 20036, USA March 28-30 The British Liquid Crystal Society -9th Annual Conference Hull, England Dr M Hird or Professor J W Goodby, School of Chemistry, The University of Hull, Hull HU6 7RX, UK Fax: 44-482-466410 April 5-8 8th High Temperature Materials Conference (HTMC VIII) Vienna, Austria Professor K L Komarek, Institut fur Anorganische Chemie der Universitat Wien, WahringerstraSe 42, A-1090, Wien, Austria Tel: +43(222)-345-424; Fax: +43(222)-310-4597 April 5-9 20th Annual Meeting: Society for Biomaterials Boston, USA Rosealee M.Lee, Executive Director, Society for Biomaterials, 6518 Walker Street, Suite 215, Minneapolis? MN 55426-4215, USA. Tel: 612-927-8108; Fax: 612-927-8127. April 11-13 Microscopy of Composite Materials 11 Oxford, UK The Royal Microscopical Society, 37/38 St Clements, Oxford OX4 lAJ, UK April 11-14 Deformation, Yield and Fracture of Polymers Cambridge, UK Mrs Debbie Schorer, Conference Department (C406), The Institute of Materials, 1Carlton House Terrace, London SWlY 5DB, United Kingdom Tel: 071-839-4071; Fax: 071-839-3576 April 24-28 The American Ceramic Society Annual Meeting Indianapolis, USA Meetings Secretary, The American Ceramic Society Inc., 757 Brooksedge Plaza Drive, Westerville, Ohio 43081-6136, USA Tel: 614-890-4700; Fax: 614-899-6109 April 25-29 International Conference on Metallurgical Coatings and Thin Films (ICMCTF-94) San Diego, USA ICMCTF-94, Dale C.McIntyre, Sandia National Laboratories -New Mexico Advanced Materials Laboratory, 1001 University Boulevard SE, Suite 100, Albuquerque, NM 87106, USA May 15-20 Seventh International Meeting on Lithium Batteries Boston, USA Dr H. Frank Gibbard, Duracell Inc., New Products and Technology Division, Duracell Worldwide Technology Center, 37A Street, Needham, MA 02194, USA May 24-27 EMRS 1994 Spring Meeting Strasbourg, France P. Siffert, EMRS, BP 20, 67037 Strasbourg Cedex 2, France. Tel: (33188 10 6543; Fax: (33)88 10 6293. June 11-16 Inorganic Chemistry: Surface Organometallic Chemistry, Molecular Materials and Catalysis Davos, Switzerland Dr Josip Hendekovic, European Science Foundation, 1quai Lezay-Marnesia, 67080 Strasbourg Cedex, France.Tel: (33188 76 7135; Fax: (33)88 36 6987 June 13-16 Science and Technology of Pigment Dispersion Luzern, Switzerland Dr A V Patsis, Institute for Materials Science, State University of New York, New Platz, NY 12561, USA Fax: 914-255-0978 June 14-17 Workshop on Polymer Blends and Alloys Luzern, Switzerland Dr A V Patsis, Institute for Materials Science, State University of New York, New Paltz, Ny12561, USA Fax: 914-255-0978 June 20-22 16th International Conference on Advances in the Stabilization and Controlled Degradation of Polymers Luzern, Switzerland Dr A V Patsis, Institute for Materials Science, State University of New York, New Paltz, NY 12561, USA Fax: 914-255-0978 June 22-24 TMS 1994 Electronic Materials Conference Colorado, USA Tim Sands, Department of Materials Science and Mineral Engineering, Hearst Mining Building, University of California, Berkeley, CA 94720, USA Tel: 510-642-2347; Fax: 5 10-642-9164 June 29-July 4 8th CIMTEC: Forum on New Materials and World Ceramics Congress Florence, Italy 8th CIMTEC, PO Box 174, 48018 Faenza, Italy Tel: +546-22461, + 546-664143; Fax: +546-66-3362 11 July 3-8 15th International Liquid Crystal Conference Budapest, Hungary Professor Lajos Bata, Research Inst for Solid State Physics of the Hungarian Academy of Sciences, Liquid Crystal Department, H-1525 Budapest, PO Box 49, Hungary Tel: 36-1-169-9499; Fax: 36-1-169-5380 July 3-8 First European Conference on Synchrotron Radiation in Materials Science Chester, UK Professor G N Greaves, SERC Daresbury Laboratory, Warrington WA4 4AD, UK Tel: +44(0)925-603335; Fax: +44(0)925-603174 July 4-8 First Euroconference -Ceramic Oxygen Ion Conductors and Their Technological Applications Lake Windermere, UK Ms M Peacock, Conference Department (C435), The Institute of Materials, 1Carlton House Terrace, London SW1Y 5DB Tel: +44 (0)71 235 1391; Fax: +44 (0)71823 1638 July 4-8 20th International Conference on Organic Coatings Science & Technology Athens, Greece Dr A V Patsis, Institute for Materials Science, State University of New York, New Paltz, NY 12561, USA Fax: 94-255-0978 July 4-9 Materials and Mechanisms of SuperconductivityIHigh Tc.Grenoble, France M Cyrot, CNRS, 25 Avenue des Martyrs, 38042 Grenoble, Cedex, France July 6-8 Silicon-Containing Polymers Canterbuy, UK Dr R G Jones, Centre for Materials Research, Chemical Laboratory, University of Kent, Canterbury, Kent CT2 7NH, UK Tel: +44 (227) 764-000 ext. 3544; Fax: +44 (227) 475-475 July 6-11 Reactivity in Organized Microstructures: New Materials Mont Sainte Odile, France Dr Josip Hendekovic, European Science Foundation, 1quai Lezay-Marnesia, 67080 Strasbourg Cedex, France. Tel: (33188 76 7135; Fax: (33188 36 6987. July 11-12 Meeting of the Tetrapyrrole Discussion Group on Chemistry and Biochemistry of Tetrapyrroles London, UK Ray Bonnett or Martin Warren, Queen Mary & Westfield College, Mile End Road, London El 4NS Fax: 071-975-5500 July 11-15 35th International Symposium on Macromolecules: MACROAKRON '94 Akron, Ohio, USA Macroakron '94, Cathy Manus-Gray, Symposium Coordinator, Institute of Polymer Science, The University of Akron, Akron, OH 44325-3909, USA July 19-2% International Conference on Excitonic Processes in Condensed Matters Darwin, Australia Dr J Singh, Faculty of Science, Northern Territory University, PO Box 40146, Casuarina, NT 0811, Australia July 24-29 30th International Conference on Coordination Chemistry Kyoto, Japan Professor H Ohtaki, Laboratories of Coordination Chemistry, Institute for Molecular Science, Myodaiji-cho, Okazaki 444, Japan July 25-29 35th Microsymposium on Macromolecules Prague, Czech Republic 35th Microsymposium, PMM Secretariat, do Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic July 25-29 International Conference on Synthetic Metals Seoul, Korea Dr C Y Kim KIST, PO Box 131, Cheongryang Seoul 130-650, Korea Fax: 82-2-965-3852 August 1-5 2nd International Conference on f-Elements Helsinki, Finland Professor L Niinisto, ICFE-2, Conference Chairman, Helsinki University of Technology, Department of Chemical Engineering, Kemistintie 1, FIN-02150 Espoo, Finland Fax: +358-0-462-373 August 2-6 Fourth Asian Conference on Solid State Ionics Kuala Lumpur Secretary, Fourth Asian Conference on Solid State Ionics, do Department of Physics, Faculty of Physical and Applied Sciences, Universiti Kebangsaan Malaysia, 43600 Bangi, Malaysia August 11-16 Supramolecular Chemistry: 100Years Schloss-Schlussel Prinzip Mainz, Germany Dr Josip Hendekovic, European Science Foundation, 1quai Lezay-Marnesia, 67080 Strasbourg, France.Tel:(33)88 76 7135; Fax:(33)88 36 6987. August 2 1-26 1994 ACS National Autumn Meeting Washington DC, USA ACS International Activities Office, 1155 16th St. NW, Washington DC 20036, USA August 28- ECM 16, European Crystallographic Meeting September 2 Dresden, Germany Professor P Paufler, Fachbereich Physik, Teknische Universitaet Dresden, Mommsenstrasse 13, D-0-8027 Dresden, Germany Tel: 3378; Fax: 37-51-463-7109 September 4-7 Second European East West Workshop on Chemistry and Energy Sintra, Portugal Cesar Sequeira, Instituto Superior Tecnico, Av.Rovisco Pais, 1096 Lisboa Codex, Portugal. September 5-7 Electroceramics lV,International Conference on Electronic Ceramics & Applications Aachen, Germany Professor Dr Raker Waser, Institut fiir Werkstoffe der Elektrotechnik, RWTH Aachen, D-52056 Aachen, Germany ... 111 September 5-9 European ESR Meeting on Recent Advances and Applications to Organic and Bioorganic Materials Paris, France Dr Bernard Catoire, GARPE, do ITF-Lyon, BP 60, F-69132 Ecully, France Tel: 78 33 34 55; Fax: 78 43 39 66 September 5-9 6th International Symposium. Scientific Bases for the Preparation of Heterogeneous Catalysts Louvain-la-Neuve, Belgium Dr G.Poncelet, Unit6 de Catalyse et Chimie des Matkriaux Divisks, Place Croix du Sud, 2 boite 17, 1348 Louvain-la- Neuve, Belgium September 6-9 International Conference on Liquid Crystal Polymers Beijing, China Professor Xibai Qiu, Chinese Chemical Society, PO Box 2709, Beijing 100080, China September 7-9 Recent Developments in Degradation and Stabilization of Polymers: Polymer Degradation Discussion Group Brighton, UK Dr NC Billingham, School of Chemistry and Molecular Sciences, University of Sussex, Brighton, BN1 9QJ, UK. Tel: 0273 678313; E-mail: N.Billingham@sussex.ac.uk September 11-14 Ceramic Processing Science and Technology Friedrichshafen (Bodensee), Federal Republic of Germany Deutsche Keramische Gesellschaft e.V., Frankfurter Strasse 196, D 5000 Koln 90, Federal Republic of Germany September 11-14 11th European Conference on Biomaterials Pisa, Italy Professor Paolo Giusti, 11th European Conference on Biomaterials, Dipartimento di Ingegneria Chimica, Chimica Industriale e Scienza dei Materiali Via Diotisalvi, 2-56126, Pisa Italy September 11-17 1st Euroconference on Solid State Ionics Ionian Sea, Greece Professor Dr W Weppner, Christian Albrechts University, Chair for Sensors and Solid State Ionics, Kaiserstr 2, D- 24098 Eel, Germany September 25-30 International Conference on Molecular Electronics and Biocomputing Goa, India Dr Ratna S Phadke, Scientific Secretary for ISMEBC '94, Chemical Physics Group, Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400 005, INDIA Tel: +91 (22)-215-2971; Fax: +91 (22)-215-2110 October 2-6 66th Annual Meeting of the Society of Rheology Philadelphia, PA, USA Norman Wagner, Dept.Chemical Eng., University of Delaware, Newark, DE 19716 Tel: (302) 831-8079; Fax: (302) 831-10 October 10-12 3rd International Symposium on Structural and Functional Gradient Materials Lausanne, Switzerland FGM '94, Swiss Federal Institute of Technology of Lausanne, Materials Department, LMM, CH-1015 Lausanne, Switzerland Tel: (+41) 21 693 29 15/50; Fax: (+41) 21 693 46 64 October 24-25 International Polypropylene Conference London, UK Ms M Peacock, Conference Department (C446), The Institute of Materials, 1Carlton House Terrace, London SWlY 5DB, UK October 24-28 Post-doctoral Course on Degradation and Stabilization of Polymeric Materials Clermont-Ferrand, France Prof.J. Lemaire, Laboratoire de Photchimie, URA CNRS 433, Universite Blaise Pascal, 63177 Aubiere Cedex, France. November 14-19 Ionizing Radiation and Polymers Guadeloupe, France Ing. Alain LeMoel, SRSIM/LPI, CEA CEN Saclay, Batiment 466, F-91191 Gif Sur Yvette Cedex. Tel: (33) 16908 5485; Fax: (33) 16908 9600. December 19-22 1994 International Conference on Electronic Materials (ICEM'94) & 1994 IuMRsInternational Conference in Asia (IUMRS-ICA) Hsinchu, Taiwan C/o Materials Research Laboratories, ITRI, Conference Department, IUMRS-ICEM/ICA'94, Bldg 77, 195 Chung-hsing Rd, Sec. 4, Chutung, Hsinchu, 3105, Taiwan, ROC. Tel: +886-354420064, 886-35-916801; Fax: 886-35-820247, 886-35-820262; E-mail: 740366@MRL.ITRI.ORG.TW ConferenceDiary 1995 August 19-25 Clays and Clay Materials Science Leuven, Belgium Professor P Grobet, Secretary Euroclay '95, Centrum voor Oppervlaktechemie en Katalyse, K U Leuven, K Mercierlaan 92, B-3001 Heverlee, Belgium December loth International Conference on Solid State Ionics Singapore €3 V R Chowdari, Department of Physics, National University of Singapore, Singapore -0511 iv

ISSN:0959-9428    

DOI:10.1039/JM99404BP029

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

J. MATER. CHEM., 1994, 4(3), 367-371 Nanocomposite Materials: Polyaniline-intercalated Layered Double Hydroxides Thierry Challier and Robert C. T. Slade* Department of Chemistry, University of Exeter, Stocker Road, Exeter, UK EX4 4QD Open lamellar systems such as layered double hydroxides (LDHs) can be used to generate new intercalation compounds. We report the synthesis of nanocomposite materials consisting of organopolymer molecules encapsulated between ultra-thin mixed-metal hydroxide sheets which are propped apart by spacers [terephthalate or hexacyanoferrate(ti) ions acting as pillars]. The oxidising host matrixes [Cu;?,,C<+(OH)J [(C6H,-l ,4-(C02),),2, .nH,O] and [Cu~?,AI~' (0H)J -[(Fe(CN),);, .nH,O] were used as hosts for the interlamellar oxidative polymerisation of aniline.The materials were prepared using chimie douce pathways and characterised by conventional physical techniques (XRD, FTIR, TG, DTA), which indicated the presence of polyaniline molecules and the retention of the host framework after incorporation of the organopolymer. Layered double hydroxides (LDHs) form a complementary 45 min at room temperature, of an aqueous terephthalate [or solution to a mixture of the di- class to the conventional cationic clays and related lamellar hexacyanoferrate(~~)]-NaOH systems (e.g. smectite clays, phosphates and phosphonates of and tri-valent nitrate salts. The slurries were divided into tetravalent metals). The structure of these compounds is three equal portions and stirred overnight at room tempera- common to a large number of minerals (e.g.pyroaurite) and ture, 60 "C and under reflux, respectively. The products were synthetic phases for which the composition can be described recovered by centrifugation, washed several times with deion- ized water and dried in an oven at 60 or 120 "C. The Cu":M3+ by the general formula [Mf~x,M~+(OH)2]1ayer* [A:, nH201interlayer(M2+=Mg, Co, Ni, Cu, etc., M3+=Al, Cr, Fe, etc., A =C1, CO,, NO,, etc.).Positively charged brucite- type layers are separated by mobile gallery counter-anions AY-and water molecules loosely bound to the hydroxy groups.' The mineral hydrotalcite Mg,A1,(OH),,C03 -4H20 is a representative LDH, and an extensive description of the synthesis, the properties (anion exchange capacity, conduc- tivity) and the potential applications of related materials has recently been published.2 The controlled intercalation of spa- cers (pillars) in the interlamellar gaps of these anionic clay: has been demonstrated and laminates with typical 9-10 A gallery height have been synthesized using terephthalate, silicate or polyoxometalate anions.>" Such host lattices with nanometre-sized interlayer spacings offer the possibility of preparing new organo-inorganic composite materials with specific mechanical, thermal and chemical properties.The encapsulation of macromolecules with the potential to be conductive (e.g.polymer electrolytes, conjugated polymers) has been successfully achieved in a wide range of layered solids such as montmorillonite, vanadium pentaoxide, iron oxide chloride and copper-exchanged phosphates.12-18 The majority of these intercalation materials have been prepared using chimie douce methods (e.g.electron-transfer processes) which allow retention of the two-dimensional host lattice. This paper reports the intercalative polycondensation of ani-line in swollen hydrotalcite-like compounds containing intra- sheet oxidant Cu2 centres. A combination of physical tech- + niques (XRD, TG, DTA and FTIR) has been used to character- ise the lamellar intercalation products. Experimental Synthesisof the Swollen Precursors: Terephthalate-Cun-Cp and Hexacyanoferrate (II)-CU"-A~"' Systems The method of synthesis of CU:,+,,Cr;+(OH),(C,H,-1,4-(C02),)$ * nH20 (TA/Cu/Cr LDH, TA =terephthalate dianion) and Cu:,',,Al~+(OH),(Fe(CN),)4,;, nH20 [CF/Cu!AI LDH, CF =hexacyanoferrate(r1) anion] followed closely the one-step reaction described by Drezdon.' The compounds were precipitated by slow addition, over ca.molar ratio used in the preparation was 2 for all the samples and the final solution pHs were typically between 7 and 9, higher values lead to the presence of crystalline by-products Cu(OH), and/or CuO, which were easily detected by X-ray diffraction. The yields of the blue TA/Cu/Cr LDHs ;and the brown CF/Cu/Al LDHs were ca. 90%. Elemental composi- tions found for TA/Cu/Cr LDH and CF/Cu/Al LDH prepared and dried at 60°C were: Cu, 27.5%; Cr, 14.6%; C, 13.0%; H, 2.7%; N, <0.1% and Cu, 28.1%; Al, 6.5%; Fe.8.9%; C, 9.8%; H, 2.6%; N, 11.0%, respectively. (Theoretical values calculated for CU,C~~(OH),,(C,H,-~,~-(CO~)~)~3H20 (A4= 682.63 g mol-I), Cu, 27.9%; Cr, 15.2%; C, 14.1%; H, 2.9%; and Cu3.5A12(OH)8(Fe(CN)6)l,25.5H20(M=?67.18 g mol-I), Cu, 28.9%; Al, 7.0%; Fe, 9.1%; C, 11.7%; H, 2.3%; N, 13.7%). Synthesis of the Aniline-intercalated LDHs The dried materials (0.5 g of TA/Cu/Cr LDHs and C€'/Cu/Al LDHs) were refluxed for 24 h in 50 cm3 of pure aniline. Black solids were separated from dark solutions by centrifugation, washed with acetone, methanol and DMSO and finally dried overnight at 60 "C. Characterisation Powder X-ray diffraction (XRD) patterns were recorded on a Philips diffractometer (PW 1050 gonjometer) using nickel- filtered Cu-Ka radiation (2= 1.54178 A).Samples were step- scanned from 3 to 60" of 20 with a step size of 0.05' and a dwell time of 4 s. Differential thermal analysis (DTA, calcined alumina as reference) and thermogravimetry (TG) were simul- taneously performed in static air on a Stanton Redcroft STA781 analyser with a heating rate of 5°C min-l. Sample powders (ca. 3 mg) were placed in a platinum crucible and heated to 800 "C. Fourier-transform infrared (FTIR) spectra of samples dispersed in dry KBr pellets were taken between 4000 and 500 cm-' on a Nicolet Magna-IR 550 spectrometer. Microanalysis of metals, C, H and N was performed by Butterworth Laboratories Ltd., UK. Results and Discussion Terephthalate/Cu/CrLDHs XRD patterns obtained for TA/Cu/Cr LDHs are presented in Fig.1. The profiles, recorded for several samples obtained with different ageing and drying temperatures, show broad and asymmetric diffraction lines characteristic of hydrotalcite-like compounds with a poor level of crystallisation. Successive orders of (001) reflections were generally observed and were used to calculate the basal d-spacing corresponding to the interlayer distance. Assuming a brucite-type layer thickness of 4.8 A19 and the aromatic rings oriented perpendicularly to the sheets, the d-spacing expected fqr the terephthalate pillared compounds should be at least 12 A.2oThe coprecipitation of TA/Cu/Cr LDHs gave materials containing a mixture ?f phases with interlamellar distances of 14.1, 10.5 and 9:8 A.The phase with the larger d-spacing (phase I, d= 14.1 A) is the major product in the materials prepared at 20 or 60°C (samples 1 and 2 in Fig. 1). For the samples erepared at higher temperatures or dried at 120"C, the 14.1 A reflection broadens and its intensity decreases, indicating that !he phase I tends to disappear while the phases at 10.5 and 9.8 A become the main products. It is well known that the hydration state of LDHs and subsequently the size of the interlayer decreases when the drying temperature increases. It follows from XRD results that water molecules, likely to be hydrogen bonded to carboxylate groups, contribute with the terephthalate anions to the interlayer thickness of the 'wet' materials.The phases with a d-spacing smaller than the 'theoretical' value can be explained by the existence of strong interactions between the counter anions and the hydroxide layers, as already observed in carbonate-containing LDHs.*' Furthermore, terephthalate anions inclined to the layers could also be consistent with the observation of low d-spacings. No carbonate or nitrate LDH phases were detected in the compoupds, as indicated by the absence of reflections at 7.8 and 8.8 A, respectively.2Thermal analysis revealed an identical behaviour for all the samples and typical TG and DTA graphs are given in Fig. 2. The water loss begins as soon as heating is applied and two stages are observed below 240-260°C. They correspond to the elimination of residual surface water and interlamellar water molecules.The total water amounts estimated from the TG ,,I I 1'0 15 20 25 30 35 2Bldeglees FiQ 1 XRD profiles of TA/Cu/Cr LDHs (basal spacings indicated in A). Synthesis (TI)and drying (T,)temperatures: (a) TI =20 "C, T, =60 "C; (b) TI =60 "C, =60 "C; (c) Ti = 100"C, =60 "C; (d) =20 "C, T,= 120"C; (e) = 100"C, T2= 120"C J. MATER. CHEM., 1994, VOL. 4 C :: Fig. 2 Typical DTA (-) and TG (+ ) profiles of TA/Cu/Cr LDH [sample (a) of Fig. 11 results were ca. 16 and 12% for the samples dried at 60 and 120"C, respectively. The next two steps (between 260 and ca. 450°C) result from the dehydroxylation of the layers and the decomposition of the terephthalate anions. Two intense exo-thermic peaks are associated with the loss in air of two different types of C,H,-1,4-(C0,)2 anions.The approximate formula of TA/Cu/Cr LDHs compatible with both thermal and chemical analysis was Cu3Cr2(0H),,TA * nH20,the value of y1 depending on the drying temperature and ranging roughly from 2 to 4. Fig. 3 gives the FTIR spectrum recorded for the sample prepared at 20°C and dried at 60°C. Similar spectra were obtained for all other materials. The intense band with a maximum at ca. 3400 cm-' is assigned to the antisymmetric and symmetric OH stretchings of water and hydroxy groups. The broadness of the band (3700-2500cm-') implies the presence of hydrogen bonds between lattice water and the anions located in the interlayer. The strong absorptions at 1578 and 1383cm-I are characteristic of the COY groups and correspond to the antisymmetric and symmetric stretch-ings, respectively. The difference between the two frequencies (191 cm-l) is close to the value expected for a bridging carboxylate group.22The 1500-500 cm-' region contains the ring modes and the CH bendings of the organic species (vC-c=1509, 834 cm-', 6CH,in plane= 1156, 1018cm-', SCH,out-of plane =894 cm-') and the lattice modes.Hexacyanoferrate(II)/ Cu/ A1 LDHs Powder XRD patterns collected for CF/Cu/Al LDHs are given in Fig. 4. As observed in the case of terephthalate-pillared materials, products with different d-spacings were obtained according to the ageing and the drying temperatures. i7u I 40 30 4000 3500 3000 2500 2000 1500 1000 500 wavenumber/cm-' Fig.3 Typical FTIR spectrum of TA/Cu/Cr LDH [sample (a) of Fig.11 J. MATER. CHEM., 1994, VOL. 4 Fig,4 XRD profiles of CF/Cu/Al LDHs (basal spacings indicated in A). Synthesis (q)and drying (T,) temperatures: (a)T,=20°C, T,=60 -C; (b) TI =60 3C, T,=60 "C; (c) TI=100"C, T2=60 "C; (d) TI=20 -c,T2= 120"C; (e) & =100"C, & =120 T However, in all cases XRD profiles showed broad peaks which indicate a disordered stacking of the layers representative of hydrotalcite-lik: structures. A pure phase with a basal d-spacing of 9.8 A was prepared at 20 "C. The corresponding galleryo height, ca. 5.0 A, is slightly smaller than the value of ca. 6 A previously reported for the dry Fe(CN),-Mg-A1 material obtained by anion exchange of the corresponding nitrate LDH.3*23The solids synthesised at higher temperature and dried at 60 "C (samples 2 and 3 of Fig.4) contain another lamellar phase underscored by an additional set of:(001) reflections in the XRD patterns (d= 13.4, 6.6, 4.4, 3.3 A). No contamination with NO, or CO, LDHs was found at that stage. Thermal analysis indicated a multi-staged weight loss and the absence of well defined intermediate plateaux (Fig. 5). Between room temperature and 180°C weight losses of ca. 11% (two steps) and 5% (one step) associated with the dehydration are observed for the samples dried at 60 and 120"C, respectively. Above 180°C and up to 250"C, two stages were ascribed to the dehydroxylation of the layers and the decomposition of the [Fe(CN)6)4- ions.The latter phenomenon was accompanied by an intense exothermic event. The weight uptake (ca. 1%) which takes place up to 500 "C indicated the formation of metal oxides following the destruction of the lattice. Judging from the results of 5 30-v) 0i 20-E-4'li ,200' '300 '400' '500' '600 700 '80077°C the thermal decomposition and the chemical analysis, a possible formula for the pure phase would be Cu,,,Al,(OH),( Fe(CN),),.,, * 5H@. IR spectroscopy con-firmed the presence of the [Fe(CN)6I4- anion, as indicated by the sharp and intense band at 2100cm-' assigned to C-N antisymmetric stretching (Fig. 6). The frequency does not differ from the values reported in the literature for several octahedral cyano complexes.22 The broad band in the 3600-3000 cm-' region was attributed to antisymmetric and symmetric stretching of OH groups and corresponding bend- ing modes were observed at 1620 and 1020cm-1 for water and bridging hydroxy groups.v(A1-0), v( Cu-(1) and v(Cu-OH) were 678, 589 and 508 cm-l, respectively. The band at 1383 cm-' is diagnostic of the presence of NO; and/or Cog- ions which probably reside in the int,erlayer gaps. The intensity of this band was variable but no correlation was found between the amount of nitrate and/or carbonate and the synthesis temperature. Intercalation of Aniline in TA/Cu/Cr LDH and CF/Cu/ A1 LDH XRD profiles recorded after reaction with aniline were com- pared to the patterns of the original terephthalate and cyanide- based materials (called hereafter precursors).No differences were detected when the mixtures LDH/aniline were treated at room temperature, indicating that intercalation bad not occurred. Under reflux, different behaviours were ohtained depending on the ageing and the drying temperature' of the precursor. The clearest results were obtained with the LDHs prepared at room temperature and dried at 120°C [(d) in Fig. 1 and 41. The diffractograms of the intercalates are presented in Fig. 7. Intercalation of aniline resulted in swelling of the starting materials and new phases were identified with a basal spacing of 13.3 and 13.5A for TA/Cu/Cr LDH and CF/Fu/Al LDH, respectively.The average gallery height of 8.6 A is compatible with the incorporation of aniline molecules with aromatic rings oriented perpendicularly to the layers. Pure phases with this interlayer distance have been syn- thesised, but mixed-phase products must be discussed. Generally, starting materials were partially intercalated even using different host:aniline ratios or longer reaction time. The new phases are characterised by a single diffraction line, with the peaks assignable to the precursors also remaining Evidence for the polymerisation of aniline was provided by IR spectroscopy and the organopolymers were characterised using diagnostic frequencies reported in the literature. The base form of polyaniline (PANI) can be described by the general formula { [-(C,H,)-NH-(C,H,)-NH-] l-x [-(C,H4)-N = (C6H4)=N-lxIn, where the value x (O<x <1) defines the 30 [V(CN)I I "' 1' ' wavenumber/cm-' Fig.5 Typical DTA (-) and TG (+) profiles of CF/Cu/Al LDH Fig.6 Typical FTIR spectrum of CF/Cu/Al LDH [sample (a)of [sample (a) of Fig. 41 Fig. 41 J. MATER. CHEM., 1994, VOL. 4 5 10 15 20 25 30 35 40 I-11.8 A I 10 15 20 25 30 35 40 28/degrees Fig.7 XRD profiles of compounds obtained after reactioq with aniline and respective precursors (basal spacings indicated in A): (a)TA/Cu/Cr LDH, (b)aniline/TA/Cu/Cr LDH, (c) CF/Cu/Al LDH, (d) aniline/CF/Cu/Al LDH oxidation state of the polymer.24 Shacklette et reported recently a detailed study of the various conductive and non- conductive forms of PANI: the IR spectrum of the amine form (x=0), named leuco-emeraldine, exhibits generally four absorptions at ca.1600 (weak), 1500 (strong), 1290 (medium) and 820 (weak) cm-' assigned to ring-breathing modes, a phenyl-nitrogen mode and an out-of-plane CH bending mode, respectively. Deprotonation of the backbone leads to the appearance of quinoid units [-N =(C,H,) =N-] and the poly- mer with amine:imine 1:l composition is referred to as the emeraldine form, easily differentiated from the pure amine polymer by the increase of the 1600cm-' band intensity. Therefore the ratio of the peak magnitudes at 1600 and 1500cm-' can give a good qualitative indication of the oxidation state of the polymer.Charged species (polymer salts) are characterised by a diagnostic broad band at 1150 cm-' due to the vibrations of oxidised regions. Two fine bands in the ranges 770-730 and 710-630 cm-' are character- istic of five adjacent ring hydrogens and can be used as key bands to determine the presence of short oligomers. In this work, IR spectroscopy indicated the absence of monomers in the intercalates, as diagnostic frequencies of free and pro- tonated aniline26 [v,,(NH,) =3520-3450 cm-', v,(NH,) = 3420-3350 cm-', combination band at 2650 cm-l for -NH:] were not detected. Representative spectra of aniline-intercalated LDHs are presented in Fig. 8. The IR spectrum of aniline-TA/Cu/Cr LDH exhibits all the bands observed for the swollen precursor, and additional strong bands at 1487 and 1299 cm-' are the fingerprint of polyaniline (Table 1).The polymer form cannot be identified without ambiguity as the intense v,,(CO;) absorption prevents any investigation in the region 1600-1550 cm-'. The new vibrations detected at 1591, 1482 and 1295cm-' in the spectrum of aniline-Fig. 8 Typical FTIR spectra of aniline-intercalated LDHs (a) aniline/TA/Cu/Cr LDH, (b) aniline/CF/Cu/Al LDH. Key bands of polyaniline are marked with an asterisk Table 1 Additional IR frequencies observed for aniline-intercalated LDHs aniline/ aniline/ TA/Cu/Cr LDH CF/Cu/Al LDH assignment ~~ 1591 ring mode of 1487 1482 ring mode quinoid structures 1299 1295 phenyl-nitrogen mode v(CN) 1216 1209 1:4 substitution 6c-H in plane 1 1165 1 :4 substitution 6~-Hin plane 1 873 2 adjacent H atoms 6~-Hout of plane 808 2 adjacent H atoms ~C-Hout of plane 752 5 adjacent H atoms ~C-Hout of plane 696 696 591 5 adjacent H atoms 6c-H out of plane aromatic ring deformation 510 506 aromatic ring deformation CF/Cu/Al LDH suggest that the emeraldine base form has been obtained.However, in comparison with bulk polyaniline, the phenyl ring and the phenyl-nitrogen modes are slightly shifted to lower frequencies, indicating that the polymer vibrations are hindered by the lamellar framework. Furthermore, the presence of the sharp medium bands at 696 and 752 cm-l shows that short-chain oligomers are likely to have been synthesised.The intensity of the bands assigned to the spacers, 1583 and 1391 cm-' and 2089cm-' for the terephthalate and the hexacyanoferrate(r1). respectively, J. MATER. CHEM., 1994, VOL. 4 decreases significantly upon intercalation of aniline and indi- cates a diminution in the amount of anionic species and, consequently, in the positive charge of the brucite layers. This observation points out that an electron-transfer reaction between the aniline monomers and the metal-containing sheets has occurred, leading to partial reduction of the Cu2+ sites. Further investigations are in progress to determine the oxi- dation state of the metals, copper in particular, after the reaction with aniline. Thermal analysis revealed a similar behaviour for both aniline-intercalated TA/Cu/Cr LDH and CF/Cu/Al LDH.A gradual weight loss corresponding to ca. 10% occurs close to 290°C followed by a fast weight loss (40-45%) associated with an intense exothermic peak with maximum at ca. 300 "C and ending at ca. 500°C. The first loss is assigned to the dehydration of the compounds (adsorbed and residual interla- mellar water) and partial dehydroxylation of the layers. FTIR spectra were recorded for the compounds immediately after the exothermic process. In the case of the aniline/TA/Cu/Cr system the presence of terephthalate anions were clearly identified, as indicated by medium bands at 1571 and 1400cm-', whereas no cyanide modes were detected in the spectrum of the aniline/CF/Cu/Al system.For both calcined products the absence of the diagnostic phenyl-nitrogen mode at ca. 1300cm-' permits assignment of the exothermic phenomenon as the degradation of polyaniline in air. The poor stability of the organic chains confirmed the synthesis of oligomers of low molecular weight. Conclusions This study has led to the single-step synthesis of lamellar double hydroxides containing intralamellar copper cations and voluminous pillaring counterions such as terephthalate and hexacyanoferrate(i1). Powder XRD has indicated the existence of multi-phase systems made up of turbostratic disordered layers. The possibility of preparing single phases has not been ruled out and is currently being investigated. The oxidant character of Cu2+ has subsequently been used to induce oxidative polymerisation of aniline in the interlayer galleries of pillared hosts; the consequent redox intercalation of the emeraldine form of polyaniliye (PANI) results in an increased interlayer spacing (to 13.5 A).These results demonstrate the accessibility of the interlamel- lar region in these pillared materials, and also demonstrate that inorganic/organic nanocomposite materials can be pre- pared from pillared solids derived from basic parents (which themselves contain macrocationic layers and exchangeable interlayer anions). We thank the Commission of the European Communities for supporting this research under the Brite-Euram programme. The authors thank Julian Cook and Stephane Golhen for practical assistance.References 1 R. Allmann and H. P. Jepsen, Neues Jarhb. Mineral., Monatsh., 1969,12, 544. 2 F. Cavani, F. Trifiro and A. Vaccari, Catal. Today, 1991,lI, 173. 3 F. A. P. Cavalcanti, A. Schutz and P. Biloen, Preparation of Catalysts IV, ed. B. Delmon, P. Grange, P. A. Jacobs and G. Poncelet, Elsevier, Amsterdam, 1987, p. 165. 4 A. Schutz and P. Biloen, J. Solid State Chem., 1987,68,360. 5 M. A. Drezdzon, Inorg. Chem., 1988,27,4628. 6 T. Kwon and T. J. Pinnavaia, Chem. Muter., 1989,1, 381. 7 T. Kwon, G. A. Tsigdinos and T. J. Pinnavaia, J. Am. Cheim. Soc., 1988,110,3653. 8 K. Chibwe and W. Jones, Chem. Muter., 1989,1,489. 9 J. Wang, Y. Tian, R-C. Wang, J. L. Colon and A. Clearfield,Muter. Res. SOC. Symp. Proc., 1991,233, 63.10 A. Bhattacharyya and D. B. Hall, Inorg. Chem., 1992,31,1869. 11 J. Wang, Y. Tian, R-C. Wang and A. Clearfield, Chem. Muter., 1992, 4, 1276. 12 P. Cloos, A. Moreale, C. Broers and C. Badot, Clay Miner., 1979, 14, 307. 13 T. C. Chang, S. Y.Ho and K. J. Chao, J. Chinese Chem. Scnc, 1992, 39, 209. 14 M. G. Kanatzidis, C. G. Wu, H. 0.Marcy and C. R. Kannewurf, J. Am. Chem. Soc., 1989,111,4139. 15 M. G. Kanatzidis, C. G. Wu, H. 0. Marcy, D. C. DeGroot, C. R. Kannewurf, A. Kostikas and V. Papaefthymiou, Adu. Muter., 1990,2, 364. 16 D. J. Jones, R. El Mejjad and J. Roziere, Supramolecular Architecture: Synthetic Control in Thin Films and Sohds, ed. T. Bein, ACS Symp. Ser., 1992,vol. 499, p. 220. 17 B. Bonnet, R. El Mejjad, M. H. Herzog, D. J. Jones and J. Woziere, Muter. Sci. Forum, 1992,91-93,177. 18 P. Maireles-Torres, P. Olivera-Pastor, E. Rodriguez Castellon and A. Jimenez Lopez, J. Inclusion Phenom. Mol. Recog Chem., 1992, 14, 327. 19 S. Miyata, Clays Clay Miner., 1975,23, 369. 20 Handbook of Chemistry and Physics, ed D. R. Lide, CR(: Press, Boca Raton, 1992-1993. 21 D. L. Bish, Bull. Miner., 1980,103, 170. 22 K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, Wiley, Chichester, 4th edn., 1986. 23 S. Kikkawa and M. Koizumi, Muter. Res. Bull., 1982, 17, 191. 24 G. E. Asturias, A. G. Macdiarmid, R. P. Mccall and A. J. Epstein, Synth. Met., 1989,29, E157. 25 L. W. Shacklette, J. F. Wolf, S. Gould and R. H. Baughman, J. Chem. Phys., 1988,88,3955. 26 G. Socrates, Infrared Characteristic Group Frequencies Wiley, Chichester, 1980. Paper 3/04211A; Received 19th July, 1993

ISSN:0959-9428    

DOI:10.1039/JM9940400367

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

J. MATER. CHEM., 1994, 4(3), 373-377 Composite Materials based on Ti and Ru Oxides M. I. Ivanovskaya, V. V. Romanovskaya and G. A. Branitsky Scientific and Research Institute for Physical and Chemical Problems of Belarus State University, 7 4 Leningradskaya Street, 220080 Minsk, Belarus The interaction and the electronic state of the components in the Ru0,-TiO, film system, obtained by the sol-gel method from poly(buty1 titanate) and ruthenium chloride, are considered. After the films had been heat-treated in air at 770 K a composite oxide film was formed, which is mostly a phase of solid solution of TiOP in RuO,. Further annealing of the film in H, led to deterioration of the solid solution and partial reduction of both components, Ti4+ and Ru4+ ions. Within the reduced system ruthenium in oxidation states 0-VIII was identified by XPS.Titanium appeared in the form of non-stoichiometric Tino%-, oxides, mostly Ti,O,, but Ti0 and Ti,O are also possible. Ru0,-TiO, films can serve as effective anodes for some electrochemical processes, in particular, in the manufacture of chlorine and in the production of highly stable and selective catalysts for thermocatalytic sensors, which are designed for detecting reducing gases. As catalysts in thermocatalytic sen- sors, Ru02-Ti02 and anode coatings offer some advantages over palladium and platinum. The reduced Ru-Ti02 systems on supports (Al,O,, SiO,) are attractive as catalysts for many reactions: Fischer-Tropsch, oxidation, isomerization and others.The characteristic of such film catalysts is that active components are concentrated in the pre-surface layer of the support granules, thus a decrease in ruthenium concentration is achieved.' This study is concerned with the formation of the RuO,-TiO, film under joint thermal decomposition of poly( butyl titanate) (PBT) and ruthenium chloride and the electronic state of ruthenium and titanium in these systems after oxidation and reduction. Experimental We investigated Ru02-Ti0, film systems, deposited over quartz substrates and over a porous support of 2-3 mm spherical y-Al,O, granules. In order to form the films, a solution of PBT and ruthenium chloride in isopropyl alcohol-ethanol was deposited over the quartz substrates or y-A1203 granules. Commercial RuC1,.3H2O and PBT [empiri- cal formula Ti01.4(OC4H9)1,2] were used as starting materials.The concentration and volume of the solution were selected such that TiO,:RuO, =2.5 and a film thickness of 150 nm was obtained while the Ru and TiO, contents were 0.3% and 0.6% (by weight), respectively, of the total weight of the support. After they had been dried in air at 350-370K the PBT films containing ruthenium were annealed in air for 2 h at 773 K, this temperature being attained after heating for 1h. The annealing temperature was chosen taking into account the results of differential thermal analysis (DTA). DTA was performed with an OD-102 differential thermal analyser in a static air atmosphere with a heating rate of 10K min-' within the 273-973 K temperature range.The precipitates obtained after evaporation in air at 353-373 K of the solvent from the solution, comprised PBT and ruthenium chloride in the same ratio as in the initial films. Reduction of the samples was performed at 723 K for 3 h at heating rate of 30 K min-' and a cooling rate of 2 K min-'. The particle size and structural and phase transformations in the films were determined by means of transmission electron microscopy (TEM) (EM-100CX microscope). For TEM stud- ies the RuO,(Ru)-TiO, films were removed from the quartz substrates and A120, granules with HF solution. Electron diffraction data were obtained (HZG diffractometer, Cu-Ka radiation, Ni-filter). For the purpose of XRD studies a thin layer of RuO,(Ru)-TiO, film was peeled off the Al,O, granules, resulting in a decrease of the Al,03 line intensities that interfere with the analysis of phase compositions of titanium and ruthenium oxide structures.X-Ray photoelectron spectra (XPS) were recorded directly from the catalyst granule surface prior to and after reduction and after bombardment of the surface with Ar' ions to a depth of 0.10-0.15 pm. Secondary-ion mass spectra (SIMS) of the reduced samples were recorded at the same time. An LAS-300 'Riber' spectrometer using A1-Ka radiation was utilized for recording these spectra. EXAFS measurements were performed with a double-crystal X-ray spectrometer. A double monoblock Si( 11 1) crystal was used as the monochromator.Analyses of EXAFS data were carried out as described in ref. 2. Results and Discussion According to DTA data the thermal decomposition of PBT takes place in several stages [Fig. l(a)]. As the temperature is increased, removal of the residues of organic solvents and Q I Fig. 1 DTA and TG for (a) PBT and (b)PBT +RuCl.nH,O powders; heating rate 10 K min-' J. MATER. CHEM., 1994, VOL. 4 water takes place (543 K), followed by removal of hydroxy groups (663 K) and TiO, phase crystallization (788 K). When RuC1, is added to PBT the pyrolysis of PBT is intensified, leading to completion of TiO, crystallization at a lower (by 150K) temperature than during pyrolysis of PBT on its own [Fig. l(b)]. It follows from DTA data that in the pyrolysis of PBT-RuC1, the formation of titanium and ruthenium oxide is observed within the same temperature range (588-733 K).Ruthenium chloride is oxidized in air at 623 K., When a PBT film, deposited over a quartz substrate, is annealed in air (770 K, 4h) a continuous crystalline TiO, film with 5-20 nm grains is formed [Fig. 2(a)]. In order to obtain the particle size distribution the dimensions of at least 1000 particles on three different TiO, film areas were determined. Note that the particle size distribution in the films under investigation was satisfactorily reproducible. By means of XRD, two structural modifications in the TiO, film (rutile and anatase) were detected. Annealing PBT films containing added ruthenium chloride under similar conditions resulted in a crystalline film, com- posed of ununiformly sized particles.Unlike TiOz films, which are characterized by a narrow range of particle dimensions, Ru0,-TiO, films contain particles ranging from 5 to 80nm [Fig. 2(b)]. An electron micrograph of such a film is shown in Fig. 3(a). In the XRD pattern of such a film RuO, reflections predominate, while rutile and anatase reflections (TiO,) are weak. Heat treatment in H, at 473 K (for 3 h) does not alter the Ti0, film structure and phase composition. Increasing the temperature to 723 K does not result in any noticeable changes either. However long-term heating in H, at 723 K leads to the appearance of a single signal of low intensity, which can be assigned to the Ti407 phase.Annealing the RuO,-TiO, films in an H2 atmosphere results in substantial changes in dispersity of the particles: large crystallites split into small grains, forming films with particles an average size of 7 nm [Fig. 2(c)]. An electron micrograph of an RuO,-TiO, film reduced in H, at 723 K is shown in Fig. 3(b). Note that the large grains observed in the pattern 601 n 40120 I iI. ,I h?f. 40-::I 40 201 I L=L--LL20 40 60 80 100 particle sizehm Fig. 2 Particle-size distribution of (a) TiO,, (b) Ti0,-RuO, after treatment in air at 770 K for 4 h and (c) TI02-Ru0, after treatment in air at 770 K for 4 h, then in H, at 720 K for 3 h Fig. 3 Electron micrographs of RuO,( Ru)-TiO, thin films after treatment (a) in air at 770 K for 4 h; (b) in air at 770 K for 4 h then in Hz at 720 K for 3 h are really composed of small particles which are very well discriminated when viewed by an electron microscope. The phase composition of the film changes simultaneously with the dispersity during treatment with H,.Diffraction patterns show signals that can be attributed to TiO, (rutile) and partially reduced oxides of the type Ti,Oz,- l(n =4, 6, 8, 9) and, possibly, Ti0 and Ti,O. In this case TiO, peaks are higher in intensity than those of RuO,. The metallic ruthenium phase was detected by electron diffraction in Ru02-Ti02 after it had been reduced in H, at 723 K for 3 h; however, RuO, also remained. Thus, according to electron diffraction data, complete reduction of RuO, into Ru is not observed even after a long period (3 h) of reduction in H, at high tempera- ture (723 K). However, in the Ru0,-TiO, system, unlike undoped TiO,, a deeper reduction of TiOz takes place in an H, atmosphere: more Ti3+ ions are formed and these participate in Tin02n-1, Ti2+, Tif (TiO, Ti20) non-stoichiometric oxides. The reduced films of Ru0,-TiO, incorporate the phases RuO,, TiO, (rutile), Ru and Ti,,02fl-1.Because of the broad lines in the diffraction patterns and superposition of various phases, as well as the low precision of the TEM method, it was not possible to state for certain that a solid solution of TiO, in RuO, had formed in the J. MATER. CHEM., 1994, VOL. 4 Ru0,-TiO, films.However, the very much greater peak intensity of RuO, than that of TiO, with a high content of the latter in the film, may indicate the formation of a solid solution of Ti0, in RuO,. The changes in dispersity and phase composition that occur in the reduction atmosphere may also prove the existence of a solid solution of TiO, in RuO, and of decomposition thereof under H,, followed by formation of a new structural phase. The formation of a solid solution of TiO, in RuO, in the process of joint pyrolysis of PBT and ruthenium chloride confirm the results of the XRD study of Ru0,-TiO, films deposited over y-A1203 (Table 1). The values of the interplanar distance, d, obtained for Ru0,-TiO, samples annealed in air, are slightly higher than those in the RuO, unit cell (P/4mnm).In this case no intense TiO, peaks are present in the XRD. The parameters of the RuO, unit cell, measured by the ASTM method, are as follows: u =4.490 A, c =3.106 A. The samples studied !ad the following uyit-cell parameters: a =4.496 f0.002 A, c = 3.118 0.003 A. Thus, the presence in XRD patterns of intense of RuO, peaks without any TiO, peaks, along with slightly expanded dimensions of the RuO, unit cell allow us to infer the formation of a solid solution of TiO, in RuO,. An XRD study of RUO,-TIO,~,~showed only rutile-type oxide peaks with 28 values intermediate between those of RuO, and TiO,, showing that these oxides must form a solid solution. The TiO, peak cannot be lost due to high dispersity. According to TEM data, Ti0, particles have dimensions sufficient to diffract X-rays and electrons.When the Ti0, phase is present in an Ru0,-TiO, film it is easily detected by TEM and XRD. Thus, using TEM we have established that only a thin surface layer is in the TiO, (rutile) phase. This is affirmed by XPS data for an un-reduced sample of Ru02-TiO, (Fig. 4). XPS spectra of such an Ru0,-TiO, sample show Ti 2p,,, and Ti 2p,,, peaks with binding energy (E)of 458.5 and 464.2 eV, corresponding to Ti4+ in TiO,. In this case the XPS spectrum has hardly any peaks corresponding to Ru 3p3,, with an E value characteristic for Ru4+ in RuO, [Fig. 4(u)]. The highest-intensity line with E=462.5 eV in the XPS spectrum could correspond to the Ru2+ state.However, in view of the results given above, this line could also be attributed to the Ru4+ state in the solid solution of RuO, in TiO,. The intensity of this line increased slightly after the surface had been sputtered with Ar' ions, indicating that the Table 1 Ru0,-TiO, XRD data annealed at 773 K for 4 h in air 3.1821 0.0042 3.1700 25 RuO, 110 2.5632 0.0035 2.5500 25 RuOz 101 1.6897 0.0014 1.6850 16 RuO, 211 annealed at 773 K for 4 h in air and at 723 K for 3 h in H,3.3811 0.0044 3.3800 8 Ti,O,, -In 120 (Ti,%)3.1537 0.0040 3.1700 8.5 Ru02,(Ru0,) 110 2.7867 0.0039 2.8010 2 T1,O, 022 2.4405 0.0032 2.42.30 2 Ti,Oz,-l 024 (Ti&)2.3508 0.0030 2.3430 27 Ru 100 2.1456 0.0024 2.1420 4 Ru 002 2.0627 0.0021 2.0560 42 Ru 101 1.3546 0.0009 1.3530 2 Ru 110 1.2243 0.0007 1.2189 14.5 Ru 103 1.1448 0.0005 1.1434 14 Ru 112 "n=4-9.Ru6+ R u2+ Rue+ Ru4+ Ru" \, *...'i'... %'--.\..I I. 474 466 458 450 binding energy, EdeV Fig. 4 Ti 2p and Ru 3p,,, XPS spectra of Ti02-Ru0, (-1 treated (a)in air at 770 K for 4 h; (b) in air at 770 K for 4 h then in H,at 720K for 3 h. Dashed lines represent the effects of argon-ion bombardment. Dotted lines represent the separation of the spectrum into Ru- and Ti-components thickness of the TiO, film on the surface of the Ru0,-Ti02 solid solution phase is small. After reduction of the film in H,, Ru and Ti,O, phases were detec!ed (Table 1). A single line of low intensiity with d=3.1537 A is close to the RuO, line of maximum intensity (d=3.1700 A).A decrease in d can be attributed to the formation of partially reduced oxide RuO, (x=0.5, 1, 1.5). No data are available in the literature on the unit-cell param- eters for such ruthenium oxides (Ru2O, RuO, Ru203). Partial reduction of both Ru4+ and Ti4+ under H, is probable, accompanied by decomposition of the solid solution structure. XPS data indicate the formation of RuO, and TiO,. From an analysis of the complex peak in the XPS spectrum of the reduced sample of Ru0,-TiO, [Fig. 4(b)] it follows that titanium and ruthenium are present in different valence states. Low-intensity lines with E =455.3, 457.1 and 458.5 eV can be attributed to Ti2+, Ti3+ and Ti4+ states in oxides, respe~tively.~ In the Ru 3p3/, XPS spectrum we can identify lines corre- sponding to various valence states of ruthenium, from Ruo to RuS+. Owing to superposition of signals from different states it is not possible to estimate quantitative state ratios of titanium and ruthenium.After bombardment of the surface with Ar+ ions, the intensity of the peak corresponding to highly oxidized ruthenium states (Rus+, Ru6+) decreases, while the intensity of the peaks for Ruo and partially reduced ruthenium ions (Ru2+, Ru') increases. The Ru8+ and Ru6+ states are probably surface-bound. XPS peaks with high E values (470 eV and above) may be considered to be the main satellites of the Ru 3p3/, peak.' In SIMS (Fig.5), besides Ru', Ti', RuO' and TiO+ clusters, which are normally found for Ru and Ti oxides, we also found RuOTi+ and RuTi' clusters.The presence of RuOTi' clusters in SIMS confirms the existence of a solid solution in the Ru0,-TiO, system, while the presence of RuTi+ clusters illustrates the possibility of formation of Ru-Ti J. MATER. CHEM., 1994, VOL. 4 mlz Fig. 5 SIMS spectrum (fragment) of RuO2-TiO, intermetallic species in the reduction atmosphere, indicative of strong electronic interaction between ruthenium and titanium, and thus of a strong mutual influence upon each other's state within the Ru0,-TiO, system. The presence of RuOAl' and RuAl+ clusters may be the result of a strong metal-support interaction (SMSI) between ruthenium and Al,03.' This interaction could provide an obstacle to reduction of ruthenium ions to the metal and could promote the formation of highly dispersed ruthenium particles. In the SIMS spectrum there are also low-intensity lines corresponding to TiOAl+ and TiAl+ clusters.The presence of such clusters in SIMS implies the interaction of titanium ions with the support (A1203). The results of the EXAFS study of the Ru02-Ti0,/y-A1,0, sample, treated in air, showed that oxygen and ruthenium form a local structure around Ru. A long oscillation [Fig. 6(a), (b)] is characteristic of heavy backscatterers like Ru.~ Interatomic distances (R)in Fourier transforms of Ru0,-TiO, are referred to Ru-0 and Ru-Ru bonds in RuO, [Fig. 6(c)]. However, values of R and the amplitude (I) for the Ru02-Ti0,1y-A1,0, sample display certain differences from 4 6 8 10 12 14 2468 k IA-' (R-s)IA Fig.6 EXAFS oscillations (a), (b) and the associated Fourier transform (c), (d)of RuO,(Ru)-TiO,/A1,0, after treatment: (a), (c) in air at 770 K for 4 h; (b),(d) in air at 770 K for 4 h then in H, at 720 K for 3 h those for the Ru02/y-Al,0, sample (the reference sample, obtained by impregnating the support with RuC1, solution without adding PBT and processed under identical conditions; Table 2). These structural changes point to reformation of an RuO, array, caused by the introduction of titanium ions in the process of formation of the solid-solution structure. In the Fourier transform of the reduced Ru--TiO, film only one high-intensity peak is present [Fig.6(d)].The interatomic distance (RRu-RRu) obtained from EXAFS is 2.58 Jr0.02 A, which is less than the interatomic Ry-Ru distance in the bulk metal" (RRu--Ru =2.68-2.70 A). A decrease in interatomic distance is a characteristic feature of the formation of metallic clusters. Conclusions By means of joint thermal decomposition of PBT and ruthenium chloride at 773 K, RuO,-TiO, films were obtained which have an Ru0,-based solid-solution structure with Ru02:Ti02=0.3. DTA data indicate that crystallization of TiO, from PBT and RuO, from RuC1, takes place within the same temperature interval and promotes formation of a solid solution. In the presence of ruthenium, the processes of pyrolysis of PBT and crystallization of TiO, are accelerated, while the temperature of the polymorphic transformation of anatase into rutile is decreased.Partial reduction of both Ru4+ and Ti4+ accompanied by decomposition of the Ru02-TiO, solid-solution structure takes place in an H2 atmosphere at 473-723 K. In this case an effect of Ru and Ti upon the electronic states of each other is observed. The reduction of Ti4+ in the Ru0,-TiO, system occurs more readily, while reduction of Ru4+ is hampered. Table 2 Structural parameters of supported Ru02--Ti02 and RuO, after treatment in air Ru0,-TiO, RuO, Rlk Ib R/k 2.02 0.50 2.00 2.96 0.22 2.96 3.60 0.27 3.48 4.59 0.14 4.50 5.42 0.09 5.42 'Error, f0.02 A.bError, *20%. Ib assignment ~ 0.40 Ru-0 ( RuO,) 0.20 Ru-RU (RuO,) 0.35 Ru-Ru (RuO,) 0.08 Ru- RU ( RuO,) 0.12 Ru-RU (RuO,) J.MATER. CHEM., 1994, VOL. 4 Owing to the strong mutual influence of the components in the Ru0,-TiO, system ruthenium in oxidation states from Ru' to Ru8+ and partially reduced Ti states Ti2+ and Ti3+ are stabilized. As a result of the high-temperature reduction of Ru0,-TiO, films under H,, finely dispersed ruthenium particles are formed and these preserve high dispersity after a long duration in a reducing atmosphere at high temperature (720 K). Highly dispersed ruthenium particles obtained in this way have the features of metallic clusters: decreased interatomic distance in comparison to the bulk metal and strong interaction with titanium oxides and oxygen in the air.The authors are grateful to Prof. V. V. Sviridov for valuable discussions and editing of the text. The financial support of this work by the Belarus Fundamental Research Fund is also gratefully acknowledged. References 1 M. I. Ivanovskaya, V. V. Romanovskaya and G. A. Branitsky, Dokl. Acad. Sci. Belarus, 1992,36, 140. 2 D. 1. Kochubey, Yu. A. Babanov and K. I. Zamaraev, X-Ray Spectral Method of Amorphous Bodies Structure Study, Nauka, Novosibirsk, 1988. P. G. J. Koopman, A. P. G. Kieboom and H. van Bekkum, Red. Trat.. Chim. Pays-Bas, 1983,102,429. J. Augustynski, L. Balsenc and J. Hinden, J. Electrochem. Soc., 1978,125,1093. K. Kameyama, S. Shohij, S. Onoue, K. Nishimura, K. Yahikozawa and Y. Takasu, J. Electrochem. Soc., 1993, 140, 1034. 6 T. Sheng, X. Guoxing and W. Hongli, J. Catal., 1988, 111, 136. 7 Practical Surface Analysis by Auger and X-ray Phot !,electron Spectroscopy, ed. D. Briggs and M. P. Seach, Mir, MOSCOW, 1987, p. 147. 8 S. J. Tauter, S. C. Fung and R. L. Garten, J. Am. Chem. Soc., 1978,100,170. 9 T. Mizushima, K. Toji, Y. Udagdwa and A. Ueno, J. Am. Chem. Soc., 1990, 112, 7889. 10 K. Asakura, N. Kosugi, Y. Iwasawa and H. Kuroda, in Proc. Inr. Conf. EXAFS and Near Edge Structure Ill, Stanford, CA, Springer Proc. Phys., 1984, p. 190. Paper 3/04254E; Received 20th July, 1993

ISSN:0959-9428    

DOI:10.1039/JM9940400373

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

J. MATER. CHEM., 1994, 4(3), 379-384 379 Preparation and Characterization of Imidazole-Metal Complexes and Evaluation of Cured Epoxy Networks John M. Barton: Gabriel J. Buist,b Ian Hamerfon,** Brendan J. Howlin,b John R. Jones* and Shuyuan Lid a Materials and Structures Department, Defence Research Agency (Aerospace Division) RAE, Farnborough, Hampshire, UK GU14 6TD b Department of Chemistry, University of Surrey, Guildford, Surrey, UK GU2 5XH A series of copper complexes of epoxy-imidazole adducts have been prepared and characterized by 'H nuclear magnetic resonance (NMR) spectroscopy. Differential scanning calorimetry (DSC) was employed to investigate the thermal behaviour of the curing agents and to investigate the medium-term storage stability of a one-pot composition of a commercial epoxy resin when mixed with the complexes. The cure onset temperatures of the mixtures containing copper complexes are ca.2040°C higher than those of the parent epoxy-imidazole adducts and the decrease of cure onset temperatures in the early stages of storage (up to 100 h) is less. The latent nature and improved storage stability of mixtures containing the copper complex were clearly demonstrated and confirmed by the viscosity bahaviour of the catalysed mixtures of the commercial epoxy resins MY720 and MY750. 'H NMR and electron paramagnetic resonance (EPR) spectroscopy were employed to monitor the thermal decomposition of the copper(i1) complexes, which were found to decompose at 120-1 30 "C and exist in equilibrium. Glass fibre-reinforced composite samples were prepared using a commercial epoxy resin cured with the complexes and their physico-mechanical properties were evaluated.Owing to their extreme versatility, epoxy resins are used extensively in industrial applications in which they are required to cure quickly and be readily formulated as one- pot compositions (i.e. the epoxide and catalyst are stored as a mixture rather than as two separate materials that have to be mixed prior to use). This in turn means that the composition must have a stability of at least several months at ambient temperature. Imidazoles are used as epoxy curing agents owing to their fast catalytic action and also the fine mechanical properties which they produce in the cured resin.Some imidazoles are highly effective epoxy curing agents,' and recent have demonstrated that epoxy resins cured with imidazoles can have superior physical properties (e.g. better heat resistance, lower tensile elongation, a higher modu- lus and a wider range of cure temperatures) than amine-cured resulting in their wide usage in the electronics industry as moulding and sealing compounds. Imidazoles are added to epoxy systems to catalyse the homopolymerization of epoxide groups (polyetherification), but unmodified imidaz- oles have low stability when mixed with epoxies (curing occurs slowly at room temperature) making them unsuitable for use in one-pot compositions. Much work has been carried out on stabilizing imidazoles for use as latent epoxy curing agents and one approach involves the preparation of metal-imidazole complexes.435 Transition metals have been used to prepare such complexes and these have exhibited good stability at room temperature and a rapid cure at elevated temperatures.Most metal-imid- azole complexes are crystalline materials with very low solubility in common epoxides.6 Solubility of the curing agent in the epoxide is very desirable because heterogenous dispersions are liable to settle out or agglomerate during storage. It is also useful to be able to form a solution containing both the epoxide and curing agent for the manufacture of pre-impregnated fibre composite materials (prepregs). Barton found6 that both the 1: 1 (1) and 2: 1 (2) adducts of phenyl glycidyl ether (PGE) and 2-ethyl-4-methylimidazole (EMI) could be cornplexed with a variety of metal salts and, in most cases, these complexes were soluble in epoxides and organic solvents.MoreoICer, the complexes were relatively unreactive at room temperature, but effective curing agents at higher temperatures. The structures of these copper(I1) complexes (denoted lc and 2c accordingly) are shown in Fig. 1. Poncipe prepared7 a range of epoxy-imidazole adducts, then complexed these adducts with metal salts and studied the co-reaction using UV spectroscopy. He found that there was a temperature-dependent induction period to the first- order reaction and that the nature of the metal ion was important in determining the length of this induction period (and hence the stability of the complex).The order Cu" >Ni" >Co" was observed for M( 1: 1),(N03l2 and M(1:1)4Cl, (M =transition metal) at a range of temperatures (which was in agreement with the order of stability predicted from the spectrochemical series).' The 1:1 adduct (I), like other imidazaoles,' coordinates to the metal through the pyridine-type tertiary nitrogen and it is the lone pair on this nitrogen which also attacks the epoxide. Complexation pre- vents the occurrence of the reaction, but when removed from the complex (lc) the 1:1 adduct (1) will react (Fig. 2). It would appear that at a given temperature, a particular com- plex has a definite lifetime during which it is stable and no reaction occurs; after this period the complex begins to break down and reaction is then able to occur.Increasxng the temperature decreases the stability of the complex and, hence, decreases the length of the induction period, until a tempera- ture is reached at which breakdown of the complex is almost instantaneous and no induction period is seen. The choice of copper as the most stable metal complex was prompted by the results of Poncipe's work. This study investigates the thermal properties of the adducts and complex mixtures in the presence of commercial epoxy systems, and in particular their storage stability. In this way it is hoped to demonstrate the usefulness of the novel cdtalysts in applications where a one-pot epoxy formulation is desirable.Aspects of the kinetic parameters associated with curing of the epoxy monomers with these catalysts and the use of high-temperature NMR as a means of monitoring currng are outlined elsewhere.lO,ll l4 J. MATER. CHEM., 1994, VOL. 4 r C CUCI, bH3aIL lc r C 1 OH i CuCI, 0-ih CH21 2c Fig. 1 Structures and ‘H NMR designations for the copper(r1) complexes lc and 2c dCH3[“;-CH2-CH-CHz-Ni; ?H : CUcIz YH2 CH3 4 lc 1 dCH3p, b-N~N:-cH,-cH-adduct formation 1 +epoxy3or4 ring-opened intermediate 5 0-1 FH-yH2dCH3 ?yyp, ACH3 ____t-NyN+-CH, -CH-CHZ-CH-k2 -N~N+-CH, -CH-polyetherification5 +epoxy3or4 and network formation Fig. 2 Structures of the compounds employed in this study and the proposed mechanism of curing J.MATER. CHEM., 1994, VOL. 4 Experimental Sample Preparation Preparation ofthe 1:1 Adduct (1) To a stirred, refluxing solution of EM1 (5.5 g, 0.05 mol) in toluene (50 ml) was added, during the course of 1 h, a solution of PGE (7.5 g, 0.1 mol) in toluene (25 ml). The mixture was refluxed for a further 2 h and then decolorized using charcoal. The product was precipitated and washed with several por- tions of 40-60 light petroleum, and dried in a vacuum oven at 40 "C to yield 10.2 g (78%) of a dark yellow liquid. The adduct was purified by column chromatography using a silica stationary phase and 4 : 1 chloroform-methanol as the eluent (analysis by TLC using the same eluent revealed a single spot, Rf=0.6, at 254 nm).After elution, the solvent was removed under vacuum and the product dried in uucuo at 40°C. The final product was characterized by 'H NMR (proton desig- nations refer to Fig. 1). 6, (300 MHz, CDCl,, ppm from TMS) 1.21-1.26 (3H, t, J=7.5 Hz, Ha), 2.12-2.19 (3H, d, J=20 Hz, Hc), 2.64-2.66 (2H, q, J=3.6Hz, Hb), 3.89-4.09 (5H, c.m., He,f,g), 6.59 (IH, S, Hd), 6.66-7.01 (2H, c.m., Hh,j), 7.26-7.32 ( lH, d, J =8.4 Hz, Hi). The preparation was subsequently repeated to produce ca. 300 g of the desired product. Prepurntion of the 2: 1 Adduct (2) To a stirred, refluxing solution of EM1 (5.5 g, 0.05 mol) in toluene (50 ml) was added, during the course of 2 h, a solution of PGE (1.5 g, 0.1 mol) in toluene (20 ml).The mixture was refluxed for a further hour, decolorized using charcoal and allowed to cool to room temperature. The product was precipitated and washed with several portions of 40-60 light petroleum, and dried in a vacuum oven at 40°C to yield 16.1 g (78%) of a dark yellow liquid. The adduct was purified by column chromatography using a silica stationary phase and 4 :1 chloroform-methanol as the eluent (analysis by TLC using 4.5 :1 chloroform-methanol revealed a single spot, R,= 0.85, at 254 nm). After elution, the solvent was removed under vacuum and the product dried in uucuo at 40°C. The final product was characterized by 'H NMR (proton designations refer to Fig. 1). 6, (300 MHz, CDCl,, ppm from TMS) 1.20-1.28 (3H, t, J=7.7 Hz, Ha), 2.12-2.18 (3H, d, J=17.9 Hz, H,), 2.63-2.67 (2H, q, J=5.5 Hz, Hb), 3.45-4.17 (5H, c.m., He,f,g),6.58 (IH, S, Hd), 6.66-6.98 (2H, c.m., Hh,j), 7.24-7.32 (lH, d, J =8.6 Hz, Hi).The preparation was subsequently repeated to produce ca. 200 g of the desired product. Preparation of the Metal Complexes of the EMI-PGE Adducts (lc and 2c) The metal complexes were all prepared using the same basic method. To a solution of CuC12.2H20 (0.85 g, 0.005 mol) was added a solution of the 1:1 adduct of PGE and EM1 (4.65 g, 0.04 mol) in absolute ethanol (10 ml). The mixture was heated gently, with stirring, for ca. 1 h. The solution was gravity filtered and the volume of the filtrate reduced on a rotary evaporator. The complex was precipitated from solution by the addition of diethyl ether and then washed thoroughly with further portions of the same.The complexes were dried in uucuo at 40°C to yield 3.87 g (70%) of the product as a brittle green glass. Apparatus 'H NMR spectra were obtained in CDC1, and C2H,]DMS0 at a range of temperatures using a Bruker AC-300 NMR spectrometer operating at 300.15 MHz. I5N NMR spectra were obtained in acetone at 25°C on the same instrument, but at 30.4 MHz. EPR spectra were obtained with DMSO as solvent at 25-90°C using a JEOL REIX EPR spectrometer operating at X-band frequencies. DSC was performed using a Du Pont 910 calorimeter interfaced with a Du Pont 9900 computer/thermal analyser. Samples of 8 f1 mg were accurately weighed into open, uncoated aluminium DSC pans.Routine DSC scans at 10 K min-' were performed from 30 to 350°C to observe the thermal properties of each of the blends. Viscometric measurements were made on the commercial epoxy-curing agent mixtures using a Brookfield viscometer operating at a range of temperatures and at a fixed shear rate of 64 Hz. Results and Discussion 'H NMR, 15NNMR and EPR Spectroscopy The 'H NMR spectra of the complexes exhibit marked changes over those of the parent adducts. In all cases, the complexation with the copper(I1) salt produced a broadening of the signals as a result of the paramagnetic effect of copper(I1). Upon coordination, the formation of a dative covalent bond between the lone pair on the pyridinyl nitrogen atom in 1 and the d2sp3 hybrid orbital on the copper atom results in a deshielding effect as the electron density is drawn away from the ring.The net result of this effect is to shift the imidazole protons (see Fig. 1) downfield. Fig. 3 shows the 'H NMR spectra for the 1 overlaid with those of the correspond- ing copper(I1) complex (lc). I5N NMR spectra were obtained for the parent imidazole (EMI) and 1. In the case of EMI, two peaks were observed at -165.1 and -176.5 ppm. Four peaks were observed for 1 (Fig. 4), indicating that adduct formation had occurred at either nitrogen to give two 1:1 adduct isomers (although presumably the steric hindrance afforded by the methyl group makes the adjacent site less accessible). The thermal stability of the complexes was studied in DMSO by recording the 'H NMR spectrum and progressively raising the temperature of the experiment.Initially the spec- trum obtained at ambient temperature (Fig. 3) displayed poor resolution, but the signals of interest at 6.6, 2.64-2.66 and 2.12-2.19 ppm (corresponding to Hd, Hb and H, in Fig. 1) rI 1 I 10.0 8.0 6.0 4.0 2.0 0.0 6 Fig. 3 300.15 MHz 'H NMR spectra (in CDCl, at 25 "C) of the (a) 1 and (b) lc J. MATER. CHEM., 1994, VOL. 4 Fig. 4 30.4 MHz 15NNMR spectrum (in acetone at 25 "C) of 1 can be seen clearly; the signal resolution improved with increasing temperature. At 120-130 "C lc appeared to undergo decomposition with the appearance of signals at 6.45-6.56, 2.64 and 2.08-2.16 ppm, corresponding to Hd, H, and H, (these changes were accompanied by a change in the colour of the DMSO solution of the complex from emerald green to brown).A parallel study carried out on these samples using EPR analysis at 25 and 90 "C indicated that the copper in the dissociated complex still existed in the Cu2+ oxidation state (rather than having undergone oxidation). When it had been kept at ambient temperature for 11days, the same sample was again scanned at 25 "Cusing 'H NMR. While the signals displayed the same poor resolution as before, the reappearance of peaks at 2.38 and 1.28 ppm (corresponding to H, and Ha) suggests that the complex had reformed to some extent (appearing to exist as an equilibrium mixture). Unfortunately, it was not possible to isolate pure crystals of either metal complex to allow a crystal determination using single-crystal X-ray diffraction techniques.As a result, the exact geometry of the metal complexes remains unsolved, although earlier work by Poncipe7 using diffuse reflectance spectroscopy on the complexes as powders indicated that they exist in octahedral form. DSC Study of Ambient-temperature Storage Stability In order to ascertain the utility of the complexes as one-pot epoxy compositions, it was of paramount importance to measure the medium-term storage stability at ambient tem- perature of, e.g., 3 when mixed with the complexes. In order to do this, DSC was employed to determine the glass-transition temperature of the uncured material and the onset of the thermal cure exotherm after progressive ambient-temperature storage.In order to achieve this the samples were stored at ambient temperature underneath inverted Petri dishes and at intervals samples were withdrawn and scanned from -70 to 280°C at 10K min-' under nitrogen (40ml min-l). The results were obtained in the form of plots of exothermic heat flow against temperature. From the plots, the glass-transition temperatures before the cure were observed as the onset of a characteristic endothermic transition (Fig. 5), and the onset of the thermal curing reactions were observed as the start of the exothermic peak due to the cure (Fig. 5). The change in Tgwith time is a useful measure of storage stability; an increase in Tgindicates early reaction leading to solidification of the stored mixture, when Tgreaches ambient temperature. After a period of ca.50 h the adduct displayed a marked increase in Tg(of ca. 20-40 "C) over the correspond- ing complex. The onset temperature for the adduct mixture decreased at a faster rate and to a greater degree in the early stages of storage, up to 100h, than the copper complex mixture. Furthermore, the cure onset temperatures of the copper complex mixtures are raised by ca. 20-50 "C, indicating -20 9 .\ -0 5 e-c . /. --20 y" --40 0 200 400 600 800 1000 storage time/h Fig. 5 Glass-transition temperature (-) and cure onset temperature (---) us. storage time for 1 (0)and lc (a) the latent nature and improved storage stability of the copper complex over the parent imidazole.Viscometric Study of the Effect of Adducts and Complexes as Catalysts The viscosity behaviour of the catalysed mixtures of the commercial epoxy resins 3 and 4 is depicted in Fig. 6, in which the latent nature of the complexes over the parent imidazole adducts is clearly demonstrated. Mixing 4 with 5 wt% of 1 led to an increase in viscosity of the resin mixture (which is initially ca. 5 CPat 100OC) after a period of ca. 5-10 min. In contrast, the corresponding copper(I1) complex (lc) causes the same increase in viscosity to occur after ca. 50min. The same commercial resin (4) exhibits similar vis- cosity profiles when catalysed with the 2: 1 adduct (2) and corresponding complex (2c), although these curing agents consistently display a lower reactivity.Similar behaviour is also observed (Fig. 6) for the second commercial epoxy system under study (3), although the reduced reactivity of this system required a higher temperature to effect curing within a reasonable timescale. Thermal Polymerization Properties of the Catalysed Epoxy Systems Prior to this study, a number of workers had published thermal investigations of imidazole-curing of epoxy resins. Heise and Martin carried o~t'~,'~ a DSC study of the behav- t i Fig. 6 Viscosity behaviour (fixed shear rate of 64 Hz) at 100"C for MY720 catalysed with 1 (O),lc (H),2 (A) and 2c (A):and at 100"C for MY750 catalysed with 1 (0),lc (@), 2 (0) and 2c ( +) J.MATER. CHEM., 1994, VOL. 4 383 Table 1 Thermal properties of catalysed epoxy resin systems from DSC measurements - 0.4W g-' curing agent T,/"C T'/"C T,/"C T3/OC TJC AHo/J g-' L i ' \ MY750 1 130 153 241 301 - 357 lc 160 197 258 307 - 428 2 150 176 246 319 - 375 2c 160 178 250 310 - 355 2c* 147 166 244 280 - 294 MY720 1 80 116 158 277 - 634 lc 130 163 231 277 - 612 2 85 115 163 239 285 548 2c 125 160 183 222 280 564 All measurements made on mixtures containing 5 wt% curing agent (except 2c* containing 7.5 wt%) using DSC at a heating rate of 10 K min-' under nitrogen. To, Onset temperature of polyn terization enthalpy; T,, nth peak maximum (i.e.TI =lowest-temperature exother- mic peak); AHo, overall polymerization enthalpy (J g-' of epoxy monomer).4-50 160 lk0 260 2iO 300 $50 TI"C Fig.7 DSC thermograms (scans at 10K min-' under nitrogen) for 3 catalysed with (a)1 and (b)lc iour of highly pure diglycidyl ether of Bisphenol A (BADGE), when catalysed with a variety of imidazoles at differing concentrations (0.5-100 mol% imidazole). They found that the thermal properties of the network were strongly dependent on the imidazole concentration. At high imidazole concen- trations (250 mol%), the adduct reaction consumed most of the epoxide groups to form adducts. As the imidazole concen- tration was decreased, Tg increased because fewer adducts were formed and more epoxide groups were available for chain growth and cross-linking.In their DSC study12,13 the OH-adduct reaction appeared at low imidazole concentrations as a shoulder on the main exotherm (and amounted to ca. 5% of the total heat of the curing reaction). In the present study, the commercial epoxy systems MY750 and MY720 were both catalysed with 5 wt% of each of the blends 1, 2, lc and 2c and a lOK rnin-' DSC scan was obtained for each of the blends during the polymerizations. Each of the thermograms are complex, often displaying several exothermic peaks, so rather than attempting to quantify each transition, the enthalpy for the entire polymerization range was calculated (Table 1). In all cases, the effect of catalysing the epoxy system with the copper(11) complexes (lc) and (2c) is to retard the onset of polymerization. As expected, the tetrafunctional monomer 4 was markedly more reactive than the difunctional 3 (undergoing an onset of polymerization ca.50°C lower in the case of the adduct, 1, and 30°C lower in the case of the complex, lc). From Table 1, the DSC results appear to be more complex than those found by Heise and Martir~'~,'~and Jisova.14 Consequently we decided to employ alternative methods of kinetic analysis (i.e. 'H NMR and FTIR spectroscopy) and these are dealt with elsewhere.lO,ll Conclusions Upon complexation of the PGE-EM1 adducts with CuCl, the 'H NMR spectra of the copper(i1) complexes exhibited broadened signals, while the imidazole protons were shifted downfield.The cure onset temperature of the copper(I1) complex mixture increases at a slower rate and to a lesser degree in the early stages of storage, up to 100 h, relative to the parent epoxy-imidazole mixture. Furthermore, the cure onset tem- peratures of the copper complex mixtures are raised by ca. 20-50 "C. After a period of ca. 50 h the adduct displays a marked increase in T, (of ca. 20-40 "C over the corresponding complex, indicating the latent nature and improved storage stability of the copper complex over the parent epoxy-imidazole adduct. The complex mixtures consistently display a greater degree of latency, and a faster rate of viscosity increase at gelation over the parent imidazoles when analysed for their dynamic viscosity in an epoxy mixture.The DSC thermograms of each of the catalytic mixtures (containing both adducts and complexes) were complex, often displaying several exothermic peaks. The effect of catalysing the epoxy system with the copper(I1) complexes lc and 2c was to retard the onset of polymerization. The tetrafunctional monomer 4 was markedly more reactive than the difunctional 3 (undergoing an onset of polymerization ca. 50°C lower in the case of 1 and 30°C lower in the case of the complex, lc. The work of Shuyuan Liu was generously supported by The Royal Society. The authors wish to thank the Materials and Structures Department, Defence Research Agency (Aerospace Division) RAE, Farnborough for the kind use of their thermal analysis facilities. The commercial epoxy monomers were kindly donated by Mr.Ian Gurnell and Mrs. Debbie Stone of Ciba-Geigy (UK) Duxford, Cambridgeshire, UK. We also thank Dr. Graham Webb and Professor Les Sutcliffe (Department of Chemistry, University of Surrey) for. helpful discussions concerning I5N NMR and EPR assignments. References W. R. Ashcroft, in Chemistry and Technology of Epoxy Resins, ed. B. Ellis, Blackie Academic and Professional, London, 1993, pp. 58, 59. M. Ito, H. Hata and K. Kamagata, J. AppI. Polyrn. Sci., 1987, 33, 1843. R. J. Jackson, A. M. Pigneri and E. C. Gaigoci, SAMPI' J., 1987, 23, 16. R. Dowbenko, W. H. Chang and C. C. Anderson, US. Pat. 3,677,978 (1972). R. Dowbenko, C. C. Anderson and W. H. Chang, Ind. Eiig. Chem. Prod. Res. Deu., 1971, 10, 344. J. M. Barton, Defence Research Agency (Aerospace Division) RAE, Farnborough, unpublished results. C. Ponciple, Ph.D. Thesis. University of Surrey, 1985. 384 J. MATER. CHEM., 1994, VOL. 4 8 H. Irving and R. J. P. Williams, J. Chem. Soc., 1953, 3192. 12 M. S. Heise and G. C. Martin, Macromolecules, 1989,22,99. 9 R. J. Sundberg and R. B. Martin, Chem. Rev., 1974,74,471. 13 M. S. Heise and G. C. Martin, J. Appf.Polpm. Sci., 1990,39, 721. 10 J. M. Barton, G. J. Buist, I. Hamerton, B. J. Howlin, J. R. Jones 14 V. Jisova, J. Appl. Pofym.Sci., 1987,34, 2547. and S. Liu, manuscript in preparation. 11 J. M. Barton, G. J. Buist, I. Hamerton, B. J. Howlin, J. R. Jones and S. Liu, Polym. Commun., submitted. Paper 3104294D; Received 21st July, 1993

ISSN:0959-9428    

DOI:10.1039/JM9940400379

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

J. MATER. CHEM., 1994, 4( 3), 385-388 Kinetic and Simulation Studies of Linear Epoxy Systems Ian P. Aspin,” John M. Barton,” Gabriel J. Buist,” Adrian S. Deazle,” Ian Hamerton,” Brendan J. Howlin*” and John R. Jonesa” Department of Chemistry, University of Surrey, Guildford, Surrey, UK GU2 5XH Materials and Structures Department, Defence Research Agency (Aerospace Division) RAE, Farnborough, Hampshire, UK GU74 6TD The kinetics and mechanism of the reaction between Bisphenol-A phenylglycidylether (BADGE) and 1,2-dianilinoethane (DAE) has been studied by a radiochemical method using tritium as the label and also by gel permeation chromatography (GPC). In parallel with these studies molecular simulation has been used to build models of the linear polymers formed, and their physical and mechanical properties have been calculated. Cast resin samples of the polymer have been produced for experimental determination of the physical and mechanical properties and the results of these determi- nations have been compared with the calculated values.These were found to be in reasonable agreement. Epoxy resins have a long history dating back to the 1950s’ and find widespread use in high-performance materials, adhesives, coatings and in the electronics industry. This in turn has led to an increasing appreciation of the need for fundamental research to be undertaken into resin synthesis, curing systems, properties of cured products, methods for their characterization and the mechanisms of epoxy resin cure.It is important to understand the factors influencing the cure and processing of epoxy resins, and to improve our predictive capability. A knowledge of the kinetics and mechanism of cure is accessible through the rate constants for the reaction and these in turn can be fed into cure processing schedules.2 Conventional high-performance liquid chromatography (HPLC) would seem to be an appropriate means for monitor- ing the appearance of oligomeric species during cure, but the effectiveness is reduced due to the non-quantitative nature of UV detection (unless the intermediates are synthesized and analysed in this manner). Radio-HPLC [a highly versatile method developed3 at the University of Surrey which allows one to measure, through the radioactivity, the concentrations of the reactants, intermediate(s) and product(s) as a function of time] provides a quantitative method for this detection, and the situation is further simplified by considering solely the amine (and subsequent amine-containing species).A kin- etic model has been developed4 which enables the consumption/production of species in the model systems to be monitored with respect to time. The rate constants for the individual steps are available from the fit of the experimental data to the calculated model. The use of this model should enable the use of better kinetic models in cure processing. A convenient starting point for the latter area is a study of amine-epoxide reactions and, in the case of the reaction of PGE and aniline to yield an aniline-(PGE), ‘trimer’, the experimental data have shown that the intermediate and product catalyse the reaction through involvement of the hydroxy group, which is produced upon opening the oxirane ring.Furthermore, the reaction was seen to be affected by trace amounts of water, and we have reported rate constants4 for the reaction of PGE catalysed by amines previously. The PGE-aniline model system is essentially half of a commercial epoxy system. Hence, the logical extension of this work was to study systems that can form linear polymers, but do not have the added complication of cross-linking. A further area of interest is the development of computer models to predict the physical and mechanical properties of the cured product. Hence, we report here our computational studies on the linear system and a comparison of this data with experimentally determined values.This serves as a vali- dation of the methods used and indicates their future potential in cross-linked systems. A full characterization of the system involves a number of complimentary characterization techniques’ both chemical (e.g. radio-labelling, GPC) and computational (e.g. kinetic, simulation studies). The results for this system are reported here as part of our continuing research effort to understand the mechanism of epoxy cure. Experimental Sample Preparation The DAE (Aldrich) and BADGE (Shell as Epon 828) were both recrystallized from chloroform before use. Radio-labelling of Amine Samples The DAE was labelled using catalytic hydrogen exchange based on the method of Jones and co-workers.6 Purity and location of labels was assessed using 3H NMR. Samples prepared in this way were then diluted with unlabelled DAE and used without further purification.Apparatus ‘H and 3H NMR spectra were obtained in CDCl, at 25°C using a Bruker AC-300 NMR spectrometer operating at 300 and 320 MHz, respectively. Radio-HPLC was performed on DAE-BADGE reaction samples made up as acetone solutions using a tetrahydrofuran (THF)-water (containing 1YOtrifluoroacetic acid, TFA) gradi- ent elution (varying between 40:60 and 70:30 in order to effect separation, depending on the length of the oligomsr). The system comprised a Spectraphysics SP-8700 solvent gradient pump, Nuclear Enterprises Isoflo 1 radio-detector and a Spherisorb ODs5 12.5 cm reversed-phase column.Data were collected and analysed by an Apple IIe computer operating an NE radiochromatography program (ISOMESS 2000). All experiments were conducted at room temperature at a flow rate of 1 ml min-’. Kinetic fits were performed on the data using the in-house program KINET version 3.1.4 GPC was performed using a Waters system comprising a 510 pump, 490 UV detector operating at 254nm and two columns: Polymer Laboratories PLgel 3p mixed-E ,,and a Waters p-STYRAGEL column with pore size lo4A. The eluent was dichloromethane-methanol(95:5)at a flow rate of 1ml min-’. The data were collected and analysed using a Waters Data Module.The GPC was first calibrated using BADGE NH-NH I I DAE linear epoxy repeat unil (dimer) Fig. 1 Structures of species studied in the course of this work narrow weight range polystyrene samples, and later using known epoxy standards. Conformational Analysis Conformational analysis of DAE-BADGE oligomers was performed on a Silicon Graphics 4D20 using the program POLYGRAF version 3 (Molecular Simulations, Inc.). Mechanical properties were also determined using the mechanical properties module in POLYGRAF. An atomistic model where n=2 (Fig. 1) was used for the mechanical simulation. A periodic boundary condition was used to simulate the bulk properties of the oligomer. Determination of Mechanical Properties Samples of DAE-BADGE oligomers were cast as thin sheets and cured using the following schedule: degassed at 50 "C for 30 min in a vacuum oven, a further 30 min at 100"C and then the liquid was syringed into a mould and placed in an oven at 100 "C for 12 h. The mechanical properties (e.g.Young's, bulk and shear moduli) of the machined samples were deter- mined using an Instron universal testing apparatus at room temperature (crosshead speed 0.1 mm min-'). Results Conformational Analysis The flexibility of the chain was investigated by carrying out conformational searches around the dihedral angles q51 and 42(Fig. 1)using a soft search in 10" steps. The plot of and b2 against energy appears in Fig. 2 and a two-dimensional projection of this is represented in Fig.3. Radio-HPLC A typical chromatogram showing the separation of the peaks is shown in Fig. 4. The plot clearly shows peaks for each of the amine-containing species produced during the course of the reaction. A computer fit of the data, produced from this experiment, is given in Fig. 5 and the rate constants determined for the reaction are k, =0.07 l2 mol -2 h -', k, =0.15 l2 rnolp2 h-' and k2=0.13 l2 mol-2 h-', k,=0.125 l2 mol-2 h-l and k4=0.25 l2 rnolp2h-' where k, refers to the amine-catalysed initiation step, k, refers to the formation of the J. MATER. CHEM., 1994, VOL. 4 Fig. 2 Conformational plot of us. 4, (the ether linkage) of the linear epoxy chain Fig. 3 Two-dimensional conformational projection of dl us.#, (the ether linkage) of the linear epoxy chain tlmin Fig. 4 A typical radio-HPLC chromatogram showing optimal peak separation (THF-H,O, containing 1YOTFA, gradient elution varying between 40:60 and 70:30, flow rate 1ml min-l). 1, Amine; 2, amine-epoxide dimer; 3, epoxy-ended trimer J. MATER. CHEM., 1994, VOL. 4 10 20 30 40 50 60 t/h Fig. 5 Typical computer fit (KTNET version 3.1) of the radio-HPLC data produced from the BADGE-DAE (16:l molar ratio) reaction. k/12 mol-2 s-l: k,, 4.167; k,, 3.611; k,, 1.944; k3, 3.472; k4, 6.944 dimer, k, refers to the formation of the epoxy-ended trimer, k, refers to the water-catalysed formation of the dimer and k, to the water-catalysed formation of the trimer. Gel Permeation Chromatography Fig.6 depicts a stacked plot of the GPC profiles of BADGE-DAE reaction samples taken over a timescale of 4 h. The formation of higher oligomers and consumption of mon- omers can be clearly seen. The observed broadening in the latter chromatograms (polydispersity increased from 1.46 at t=O to 5.03 at t=96 h) is obviously due to formation of polymeric material. Simulation of Mechanical Properties The computed elastic constants of the system are given in Table 1 and these are compared with the experimental deter- minations of the actual Young's modulus, bulk modulus, shear modulus, Poisson's ratio and the Lam6 constant, 1.Estimated standard deviations for these values are given where possible. A further comparison is apparent from this table with the QSPR (quantitative structure-property relationship) results for these constants calculated by the method of van Kre~elen.~ Discussion Conformational Analysis The full investigation of the conformational flexibility has been submitted for publication separately,8 but it is appro- priate to observe that the conformational minima of these plots indicate that the preferred dihedral angles for 4, and 42 are+90" and+ 180".This has importance for the confor- mations adopted by the atomistic models used for the calcu- lation of the mechanical properties as shown in Tablc 1. Radio-HPLC The use of conventional kinetic treatments to provide the rate constants is not feasible in these systems because of the autocatalytic nature of the reactions.Consequently the rate equations cannot be manually integrated and it is necessary to use computer methods to perform this task. The profile of the peaks in the initial stages of reaction is very similar to that of the PGE-aniline system, vindicating its use as a suitable model of polymer formation. It is reasonable therefore to assume that similar chemical reactions are taking place in the initial stages of the reaction. Using this assumprion the data can be fitted to the current rate model program to derive comparative rate constants for the reactions. Obviousiy, how- ever, at later stages of cure there are many more species being formed and this is indicated in Fig. 7. A complete treatment of these data depends on the full characterization of these higher species and modification of the rate equations and software, and work is currently underway to address this.It is interesting to note that from the derived rate constants the k,/k, ratio for this system is close to unity. In other studies this ratio has been found to be closer to 0.5.9 Indeed, in our previous study of the aniline-PGE system the ratio was found to be 0.43.6The separation of the reactive nitrogen aloms by the ethane bridge effectively removes any influence that the first BADGE moiety to have been added may have on the addition of the second. Hence there is no electronic or steric effect on the reactivity at either nitrogen atom and the addition Fig. 6 GPC profiles [dichloromethane-methanol (95:5) at a flow rate of 1ml min-', UV 254 nm] of BADGE-DAE (1:l molar ratio) reaction samples taken over a timescale of 4 h J.MATER. CHEM., 1994, VOL. 4 Table 1 Comparison of computed and actual measured elastic constants of the BADGE-DAE polymer system" Young's modulus bulk modulus, shear modulus, Poisson ratio, Lame constant, E/GPa BIGPa G/GPa 1' I/GPa calc.' 5.84 (2.4) 5.36 (2.68) 2.05 (0.91) 0.37 (0.09) 6.19 (2.94) expt.' 3.84 (0.34) 4.61 (0.12) 1.41 (0.17) 0.36 (0.01) 3.667 (0.004) QSPR~ 4.15 4.32 1.36 0.36 3.29 ~~~ a Standard deviations in parentheses. bCalculated from POLYGRAF mechanical simulation. 'Experimentally determined. Quantitative structure property relationships (calculated from group contributions).of the second BADGE molecule is as equally favourable as the first. In the aniline-PGE system mentioned earlier the second PGE unit has to add to a nitrogen atom that already has one PGE molecule attached to it. Preliminary molecular orbital calculations performed under COSMIC" indicate that electronically there is little reason why the addition of a second PGE unit should not be as fast as the first. This raises the likelihood that steric hindrance is the factor affecting reactivity in this system. GPC In Fig. 6 it can be seen that after only approximately 4 h of reaction peaks are discernible for degrees of polymerization up to n =4 (polymer repeat units). Minor peaks can also be detected for both the amine-terminated and epoxy-terminated linear trimers. Simulation of Mechanical Properties The version of POLYGRAF used for this simulation is limited to 1000 atoms in a periodic system.For a fully atomistic model where n =40, then it would be necessary to model 3240 atoms and this would be beyond the scope of the program. Therefore, the mechanical properties were calculated using the Weber et al." method to give an 'infinite' chain (e.g. n =a).As M, for the polymer is directly related to the mech- anical properties in which we are interested, there is likely to be some discrepancy between the results determined from the simulation and the actual experimental determination. This is reflected in the larger standard deviations given on the model data.The predicted discrepancy between simulation and experimental data arises from: (i) the small number of atoms present in the periodic boundary box (hence the model displays a slight anisotropy when mechanical properties are determined); (ii) the lengths of polymer chains built in the model are infinite rather than the distribution of finite chain lengths found in the real system; (iii) finally, the model makes no allowance for defects present in the sample. However, it can be seen from Table 1 that the results are actually in reasonable agreement, indicating that it is possible to obtain comparative information from limited models such as these. Conclusions This work indicates that the use of kinetic and computer modelling of epoxy cure reactions can yield complementary information on the structure, mechanisms and expected bulk properties.This is encouraging for it highlights the possible future use of computer simulation to design novel materials with specified, desirable properties. It also provides a funda- mental understanding of the cure reactions involved with epoxy resin systems and may have implications for the industrial processing/use of commercial polymers. 3100, 80 i w1 I1 tlrn in Fig. 7 Typical radio-HPLC chromatogram depicting from the later stages of a BADGE-DAE reaction involving a higher amine concen- tration showing a number of reaction intermediates (conditions as for Fig.4). 1, Amine, A; 2, amine-epoxide dimer, AE; 3, epoxy-ended trimer, EAE; the remaining assignments are yet to be confirmed; 4, AEA or cyclic (AE),?; 5, (AE),; 6, cyclic (AE),?; 7.E(AE),; 8, (AE),; 9, E(AE),; 10, (AE), The work of Mr. Adrian Deazle and Dr. Ian Aspin was generously supported by The Procurement Agency, Ministry of Defence (grant 2064/102/A) and SERC (grant GR/H27786), respectively. The authors thank the Materials and Structures Department, Defence Research Agency (Aerospace Division) RAE, Farnborough for the kind use of their thermal analysis facilities and Dr. Martin Clegg (DRA) for GPC measurements. We would also like to thank Dr. S. Ramdas (BP Research Centre, Sunbury) for access to computing facilities. References 1 Chemistry and Technology of Epoxy Resins, ed. B. Ellis, Blackie Academic and Professional, London, 1993,and references therein.2 J. M. Vergnaud and J. Bouzon, Cure of Thermosetting Resins: Modelling and Experiments, Springer-Verlag, London, 1992, and references therein. 3 G. J. Buist, A. J. Hagger, J. R. Jones, J. M. Barton and W. W. Wright, Polym. Commun., 1988,29, 5. 4 G. J. Buist, A. J. Hagger, B. J. Howlin, J. R. Jones, M. J. Parker, J. M. Barton and W. W. Wright, Comput. Chem., 1993,17,257. 5 Polymer Characterization, ed. B. J. Hunt and M. I. James, Blackie Academic and Professional, London, 1993,and references therein. 6 G. J. Buist, A. J. Hagger, B. J. Howlin, J. R. Jones, M. J. Parker, J. M. Barton and W. W. Wright, Polyrn. Comrnun., 1990,31,265. 7 Properties of Polymers: Their Estimation and Correlation with Chemical Structure, ed. D. W. Van Krevelen, Elsevier, Oxford, 2nd edn., 1972, and references therein. 8 J. M. Barton, G. J. Buist, A. S. Deazle, I. Hamerton, B. J. Howlin and J. R. Jones, Polymer, in the press. 9 L. Dusek and S. Lunak, J. Polym. Sci., (Polqm. Symp.) 1975, 53,44. 10 J. G. Vinter, A. Davis and M. R. Suanders, J. Comput. Aided Mol. Design, 1987,1, 31. 11 T. A. Weber and E. Helfand, J. Chem. Phys., 1979,71,4760. Paper 3104296K; Received 21st July, 1993

ISSN:0959-9428    

DOI:10.1039/JM9940400385

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

J. MATER. CHEM., 1994, 4(3), 389-392 Pyrochlore-like Compounds derived from Antimonic Acid Aldo Jose Gorgatti Zarbin and Oswaldo Luiz Alves* Laboratorio de Quimica do Estado Solido, lnstituto de Quimica-UNICAMP, Caixa Postal 6754, CEP 73087-970, Campinas, Sa"o Paulo, Brazil Highly crystalline antimonic acid, H2Sb20,.1 .5H,O (CAA) with a pyrochlore-like structure has been ion-exchanged with Fe3+ and Cd2+ to form H,.,Feo.22Sb206*l .5H20 (CAA/Fe) and Ho~73Cd,,3,Sb206.1 .5H20 (CAA/Cd) phases. Thermal decomposition of these phases was studied by XRD, FTIR, TG, DSC and SEM. The final products, obtained by the thermal treatment of CAA/Fe and CAA/Cd at 11 00 "C, for 2 h, were FeSbO, and Cd2Sb207-,, respectively. The chemical homogeneity and phase purity for these compounds, and the temperature and time for reactions indicate that the use of adequate precursors has advantages, in comparison to conventional solid-solid methods involving mixtures of oxides.The search for compounds for which thermal decomposition leads to the formation of reactive or ceramic powders with technological applications, such as catalysts, semiconductors and magnetic materials, has received great attention.',2 Generally, the use of precursors has advantages over the solid-solid reaction method, in terms of temperature, time and chemical and phase purities. In this paper we investigate the possibility for FeSb04 and Cd2Sb207-compounds, which are, respectively, a catalyst for selective alkene 0xidation~3~ and a semiconductor ceramic with potential application as a gas ~ensor.~ In both cases, the powder preparation for oxides by conventional solid-state reaction requires high temperatures (ca.1100 "C) and long processing times (1-2 days).46 A precursor method can be considered if at least two cations can be atomistically distributed through a polymer7 or a particular crystal structure. In this way, the ion-exchange ( H+/Mn+) properties of crystalline hydrated oxides can lead to an interesting route for mixed-cation oxides. This paper reports the use of a pyrochlore-like phase of antimonic acid, H2Sb206.1.5H20, for the formation of ceramic oxide powders containing Fe3+ and Cd2+ as the second cation. The thermal decomposition of the ion-exchanged phases, in the range 1OO-110OoC, was monitored by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spec- troscopy and scanning electron microscopy (SEM) techniques. Experimental Materials Antimony(Ir1) oxide, hydrogen peroxide solution, hydrated cadmium and iron(Ii1) nitrates, all from Merck, were used without further purification.Preparation of Crystalline Antimonic Acid (CAA) The method of synthesis of CAA was similar to that reported by Ozawa et a/.*. H,Oz (60 cm3; 31% m/m) was added to 0.04 mol of solid Sb203. The suspension was stirred vigorously for 30 h at 65 "C. After cooling to ambient temperature, the solid was separated by centrifugation and washed successively with deionized water until pH 7 was obtained. CAA was dried at 40°C under dynamic vacuum for 8 h and stored in a desiccator.Ion Exchange 100 cm3 of a 5 x lop2mol dmP3 solution of Cd(N03),-4H20 or Fe(N03),.9H,0 in nitric acid (1 x mol drnp3) was added to 1 g (2.7 mmol) of CAA. The suspension wa., stirred for various temperatures and times to achieve maximum loading. This was achieved at a 60°C temperature and times of 24 and 168 h for Cd2+ and Fe3+, respectively. The solids were separated, dried and stored in a similar way as dtxribed for CAA. Chemical Characterization The antimony, iron and cadmium determination in the ion- exchanged solids and supernatant solution were performed by flame atomic absorption using a Zeiss model FMD3 spectrometer. The H amount released after the ion-exchange + was also measured. Heat Treatment The heat treatment of the samples (0.3 g) was carried out in a furnace at temperatures varying from 100 to 1100 'C over a period of 2 h in ambient atmosphere.Then, the ,samples were cooled and stored in a desiccator. Physical Measurements Thermogravimetry (TG) and differential scanning calorimetry (DSC) curves were obtained on a Du Pont model 1090 DSC/TGA system at a heating rate of 5 'C min-' under nitrogen flux. XRD patterns were obtained using a Shimadzu. model XD-3A diffractometer utilizing Ni filters and Cu-Kx radiation with 30 kV and 20 mA, at a 2 "C min-l scan rate. Thc room- temperature measurements were carried out with the sample spread on a conventional glass sample holder. Powder silicon reflections were used for 20 calibration.Infrared spectra were recorded in the 4000-400 cm-region using Fluorolube or Nujol dispersions between alkali-metal halide windows and KBr pellets, on a Perkin-Elmer 1600 Fourier Transform Spectrometer. SEM photomicrographs were obtained on a JEOl, model JSM T-300 microscope, using the technique of coaling the dispersed samples with gold. Results and Discussion Composition, Structure and Thermal Behaviour of the Ion-exchanged Phases The antimonic acid X-ray pattern (Fig. 1)is typical of a cubic pyrochlore-like structure' and shows that the solid is well crystallized. The chemical analysis is consistent with the J. MATER. CHEM., 1994, VOL. 4 10 20 30 40 50 60 28/degrees Fig.1 XRD patterns for (a) CAA, (b)CAA/Cd and (c) CAA/Fe H,Sb,06.1.5H,0 formula. In Table 1 the composition and some characteristics of the ion-exchanged solids are presented. As can be seen in Table 1, The H+(H30f)was partially exchanged by Cd2+ and Fe3+, in contrast to Ag+ and Pb2+, whose exchanges are stoichiometric." These marked differ- ences can be associated with the selectivity of CAA towards these ions. Generally, the selectivity shows a dependence on crystallinity degree for this type of ion exchanger." The XRD patterns of CAA exchanged with Cd2+ (CAA/Cd) and Fe3+ (CAA/Fe) shown in Fig. l(b) and l(c), respectively, do not show marked differences in peak positions. This result could be taken as evidence that no structural changes occur in the pyrochlore network by the presence of the metallic cations.On the other hand, the peaks associated with the Miller indices for which the sum h +k +I is an odd number show an intensity decrease upon exchange. The latter feature has been explained in terms of a destructive interference of certain reflections caused by the presence of metallic ions in defined sites of the cubic pyrochlore-like structure.12 Similar behaviour was observed for H, -,Ag,Sb,O,nH,O phases where there exists an unequivocal dependence of the intensity decrease with the x va1~es.l~ Fig.2 illustrates the TG curves for CAA, CAA/Fe and CAA/Cd, which consist of a practically continuous 10-15% weight loss, for temperatures below 850 "C. Thermal decompo- sition of non-exchanged hydrated antimonic acid with differ- ent degrees of crystallization has been reported previously.14-16 The following steps can be proposed for the CAA prepared in this work: (i) loss of adsorbed and structural water in the 60-280 "C range yielding anhydrous H,Sb,06; (ii) loss of water and molecular oxygen (280-600 "C) as a result of the partial reduction of SbV to Sb"' with the formation of Sb6013 (Sb:"SbT0,3); and, finally, (iii) release of molecular oxygen caused by another reduction of the SbV, producing Sb,O, (Sb"'SbvO,) that is subsequently converted to Sb203 (> 1000 "C).It is important to remark that these stages are Table 1 Composition and main characteristics of ion-exchanged CAA phases ion-exchange ion loading (mequiv.Mfl+/ (M"+) composition colour g CAA) Fe3+ H,,,,Fe,,,,Sb2O6~1.5H2O brown 1.79 Cd2+ H0.73Cd0.635Sb206-1 .5H20 white 3.44 0 200 400 600 800 1000 T/"C Fig. 2 TG curves for (a) CAA, (b)CAA/Fe and (c) CAA/Cd not separate, they occur as overlapping stages. The TG curve profiles for CAA/Fe and CAA/Cd are similar to those of non- exchanged CAA; however, differences can be observed in the weight loss, mainly after step (ii). The abrupt event at tempera- tures up to 900°C was ascribed to the sublimation of Sb,03. The DSC traces (Fig. 3) show at least a similar shape for temperatures below 350 "C. For higher temperatures, the exothermic and endothermic events are related to the nature of the new phases formed.The CAA IR spectrum shows the typical broad bands in the 3400-3000 cm-I region, associated with the OH stretching of water and H30+ perturbed by hydrogen bonds; a weak band at 1660cm-l (water OH, deformation); a shoulder at ca. 1750 cm-' (H30+ deformation) and two others bands in the 780 and 450cm-' regions, attributed to the Sb-0 stretching and a combination of Sb-0 stretching and SbO, deformation, respectively. The last two bands are characteristic of pyrochlore-like structure^.'^-^^ In relation to CAA, the IR spectra of CAA/Fe and CAA/Cd show significant profile changes in the OH stretching region as a consequence of hydrogen-bond modifications. The other bands presented decreasing wavenumber shifts (<15 cm-') and widths. The last feature is particularly observable for the Sb-0 stretching band that exhibits a noticeable sensitivity to the ion-exchange loading.0 a 200 400 600 77°C Fig. 3 DSC curves for (a) CAA, (b)CAA/Fe and (c) CAA/Cd J. MATER. CHEM., 1994, VOL. 4 Thermal Decomposition CA A/Fe Phase The CAAiFe XRD patterns for the heat-treated samples at different temperatures are shown in Fig. 4. It can be seen from the patterns that the pyrochlore structure remains stable until 700°C. For higher temperatures new peaks are observed indicating the existence of a mixture containing Sb204 and FeSbO, phase^.^ At 1100 OC all the Sb204 phase is converted to Sb,O,, which sublimes, to leave only FeSbO, remaining. The FeSb0, can be indexed as a tetragonal rutile-type accord- ing to ref.19. SEM investigation of this evolution revealed, for the heat- treated sample at 1000°C, the presence of two morphologies (Fig. 5): plate-like crystallites with particle size of ca. 80 pm and aggregates of small particles (<2 pm). In fact, considering that at 1100°C only the first is observed, we can assign it to the FeSb0, phase. Fig. 6 shows the infrared spectra (1300-400 cm-l) as a function of thermal treatment. The bands near 750 and 450 cm-l undergo changes only for temperatures higher than 800°C in agreement with the XRD results. The new bands and/or splittings observed at 1000 "C are due to vibrations involving antimony and oxygen at different sites. At this temperature the powder is constituted of Sb204 and FeSbO,.The spectrum of the heat-treated sample at 1100°C is in agreement with published data for the FeSb0,20 and corrobor- ates the XRD and SEM results. Finally, it is important to remark that FeSb0, is an important catalyst for selective alkene oxidation and its performance is significantly increased if the powder is mixed with Sb204.334 This is exactly the case when CAA/Fe is heat- treated at 900 "C for 2 h. 10 20 30 40 50 60 28ldegrees Fig. 4 XRD patterns for CAA/Fe heat-treated for 2 h at (a) 100, (b)700, (c) 800, (d) 900, (e) 1000 and (f)1100°C. 0 =FeSbO, 391 Fig. 5 SEM micrograph for the sample CAA/Fe heat-trcated at 1000"C wavenum berkm-' Fig.6 IR spectra for the sample CAA/Fe heat-treated for 2 h at (a) 100, (b) 800, (c) 1000 and (d) 1100°C.Spectra (c) and id) were obtained by the KBr pellet method CAA/Cd Phase The XRD patterns for CAA/Cd samples at various stages of the heat-treatment are presented in Fig. 7. Similar to the CAA/Fe case, the results suggest that until nearly 80Ci"C the pyrochlore-like structure is maintained. However, for the heat- treated sample at 900°C new peaks were observed th& have their intensity maxima at 1000°C and which disappear at 1100"C. According to Castro et these new reflections were attributed to the presence of a CdSb,O6 phase. Therefore, at 900 and 1000°C we have a phase mixing where one of the mixture components is CdSb206. The elemental analysis of the powder originated from the 1100 "C heat-treatments is consistent with the Cd2Sb20, -x composition.Additnonally, the XRD data are in agreement with a pyrochlore-likc struc- ture, as previously reported.22 The SEM micrographs also revealed marked morphology changes for the differenr stages of heat treatment. The CdSb206 phase appears as indented 10 20 30 40 50 60 2fYdegrees Fig. 7 XRD patterns for CAA/Cd heat-treated for 2 h at (a) 100, (h)400, (c) 600, (d) 800, (e)900 (f) 1000 and (g) 1100 "C. 0 =CdSb,O, Fig. 8 SEM micrograph of the sample CAA/Cd heat-treated at 1000'C rod shape crystallites with sizes that vary by ca. 5-10 pm (Fig. 8), whereas a porous mass, composed of small crystals (< 1 pm), was observed for Cd2Sb20,-,. At 1100°C only the latter was observed.Infrared spectra for the samples treated at temperatures higher than 900 "C present very weak transmission (< 20%) in the range 4000-800 cm-'. This behaviour could be related to the semiconducting nature of these powder^.^,^ For tem- peratures lower than 900 "C the infrared spectra are similar to that for the CAA/Cd non-heat-treated sample. In this case, the use of a CAA/Cd precursor leads to the J. MATER. CHEM., 1994, VOL. 4 obtention of semiconducting ceramic powders at lower tem- peratures than the one used in the solid-solid reaction involv- ing CdO, Sb203and Sb20,.5,6321 Conclusions The present results indicate that the thermal decomposition of ion-exchanged CAA with Fe3+ and Cd2+ permits the use of new routes for the preparation of certain materials that are classically obtained by heating a mixture of oxides.We can remark on some important advantages arising from this method: (i) normally, the temperature and time reaction are less than for conventional methods (solid-solid reaction); (ii) the phases are formed from a single compound (CAA ion- exchanged), and not from a mixture of different reagents (this point eliminates problems with the reactivity of the solids, grinding, crystal habit, etc); (iii) obtention of the final products with great chemical homogeneity and phase purity. An extension of this method to other ion-exchangeable hydrated metal oxides, and studies on the correlations between loading, precursor structure type and properties of final products are under investigation in this laboratory.The authors would like to thank Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) and Fundo de Apoio ao Ensino e Pesquisa da UNICAMP (FAEP) for the fellowship to A.J.G.Z. References 1 P. A. Lessing, Ceram. Bull., 1989,68, 1002. 2 N. G. Error and H. U. Anderson, Muter. Res. Soc. Symp. Proc., 1986,73, 571. 3 M. Carbucicchio, G. Centi and F. Trifiro, J. Catal., 1985,91, 85. 4 G. I. Straguzzi, K. B. Bischoff, T. A. Koch and G. C. A. Schuit, J. Catal., 1987, 104,47. L. Biao-Rong, J. Am. Ceram. Soc., 1988,71, C-78-C-81. B. R. Li and J. L. Zhang, J. Muter. Sci.Lett., 1990,9, 109. M. Pechini, US.Pat., 3 330 697, July 11, 1967. Y. Ozawa, N. Miura, N. Yamazoe and T.Seyama, Chem. Lett., 1982, 1741. 9 W. A. England, M. G. Cross, A. Hamnet, P. J. Eisman and J. B. Goodenough, Solid State Ionics, 1980, 1,231. 10 V. A. Burmistrov, Y. M. Ryabishev, A. I. Sheykman and N. I. Hmon'kina, Izu. Akad. Nauk SSSR, Neorg. Muter., 1991, 27, 50. 11 F. A. Belinskaya and E. A. Militsina, Usp. Khim.. 1980,49, 1904. 12 V. A. Burmistrov, D. G. Kleschev, V. N. Konev and R. N. Pletnev, Zh. Neorg. Khim., 1985,30, 1959. 13 A. J. G. Zarbin, J. M. Sasaki, L. Cardoso and 0. L. Alves, in preparation. 14 D. J. Stewart, 0.Knop and C. Ayasse, Can. J. Chum., 1972,50,690. 15 M. Abe and K. Sudoh, Bull. Chem. SOC.Jpn., 1982,55,615. 16 C. Forano and J. P. Besse, Eur. J. Solid State Inorg. Chern., 1988, 25, 141. 17 M. T. Vandenborre and E. Husson, J. Solid State Chem., 1984. 53, 239. 18 M. T. Vandenborre, E. Husson and J. L. Fourquet, Spectrochirn. Acta, Part A, 1982,38,997. 19 F. J. Berry, J. G. Holden and M. H. Loretto, J. Chem. Soc. Furaduy Trans. 1, 1987,83,615. 20 C. Rocchiccioli-Deltcheff, T. Duprius, R. Frank, M. Harmelin and C. Wadier, C. R. Acad. Sci.Ser. B., 1970, 571. 21 H. Castro, 1. Rashes, M. C. Sanches-Martos and P. Garcia- Casado, Powder DifSr., 1988,3(4), 219. 22 A. J. G. Zarbin and 0.L. Alves, J. Muter. Sci. Lk'tt., in the press. Paper 3/04345B; Received 21st July, 1993

ISSN:0959-9428    

DOI:10.1039/JM9940400389

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

J. MATER. CHEM., 1994, 4( 3), 393-397 Silicon-Germanium Films for Photomasking Applications Chi-Wing Liu,* James A. Cairns, Roderick A. G. Gibson, Andrew C. Hourd, Brian Lawrenson and Charles F. Leecet Department of Applied Physics and Electronic and Manufacturing Engineering, University of Dundee, Dundee, UK DDI 4HN Si-Ge films have been deposited by RF co-sputtering and have been compared to Cr films for use as opaque materials on photornasks. One of the potential attractions of Si-Ge is its ability to be patterned by dry etch, anisotropic processing. Optical absorption coefficients were measured from 347 to 820 nm using a modified spectrophotometer. The absorption coefficient of Si-Ge films (containing 32.6% Ge) was 1.5x 1O5 cm-' whereas the 'standard' Cr gave 5.6 x lo5crn-'.A simple scratch test was used to compare the adhesion of the films to fused silica substrates. Specially fabricated cantilevers were used to study interfacial stress between films and substrates. Cr and Si-Ge with similar thicknesses exhibited tensile and compressive stress, respectively. These observations have confirmed the potential of Si-Ge as a photomask opaque. Most modern integrated circuits are manufactured by the use of photomasks to define the circuit pattern to be transferred to the wafer. As integrated circuits continue to become ever more complex, the materials requirements of modern photo- masks become increasingly demanding. Every photomask is unique and must be free from physical defects, even down to sub-micrometre dimensions.These requirements impose a strict specification on all the materials and processes used in their manufacture, which starts from a highly polished fused silica substrate coated with a thin (100nm) layer of chromium, followed by a layer of organic resist. The latter is subjected to high-resolution radiation, using, for example, a focused electron beam, which changes its chemical nature, thereby allowing it to be removed selectively to reveal an exposed chromium layer. This, in turn, is removed by a liquid dissolu- tion process. The resultant chromium-patterned fused silica is then used to make integrated circuits by passing ultraviolet light through its clear areas to expose a resist-coated wafer. Each of the steps described above has the potential for departure from the strict specification required. As integrated circuits increase in complexity, the control of the dimensions provided by the chromium photomask becomes critical, and highlights the limitations of using chromium as a photomask opaque.For example, the process of removing chromium involves wet etching, which is an isotropic (non-directional) process. This can cause lateral etching of the chromium, leading to loss in definition of critical pattern features. Furthermore, there is a significant stress between the chro- mium film and the underlying fused silica, which can cause distortion of the photomask, and hence the final image. The stress also leads to uncertainty in the ability of sub-micrometre chromium features to retain adhesion to the fused silica, especially during the vigorous cleaning to which the photo- mask is ultimately subjected.Although chromium can be dry etched (an anisotropic or unidirectional process) to give the desired features, with little or no lateral etching, this requires the use of chlorine-containing process gases, which are extremely corrosive and environmentally undesirable. Therefore there is a strong motivation to identify a new opaque material to replace chromium. This should be opaque to deep UV, exhibit good adhesion to fused silica with minimum interfacial stress, and be capable of being patterned by dry etch processing. In addition, it should exhibit ideally an absorbance >3 at 7 Present address: Compugraphics International Limited, Eastfield Industrial Estate, Glenrothes, Fife, UK KY7 4NT.633 nm (corresponding to an optical absorption cotrfficient, a=7 x lo5cm-l) in order to be compatible with existing inspection and alignment systems. It is well known that silicon (Si) can be processed by dry etching to produce patterns with good edge and feature profiles. However, its absorbance at 633 nm is not high enough to meet the optical requirement detailed above. This can be overcome by introducing other elements into silicon during its deposition onto the fused silica substrates. Germanium was chosen because it has good optical absorption and is chemically compatible with Si. In addition, it exhibits similar etching characteristics.The importance of this approach is apparent from the considerable activity in the patent litera- ture.' Previous work by Kao et aL2 has shown that the incorporation of Ge into Si can cause a significant increase in the absorption coefficient. This was done by placing a known area of Si segments onto a Ge wafer target.3 The Si-Ge films were deposited onto optically flat glass substrates by RF sputtering in a gaseous mixture of argon-5% hydrogen at a pressure of 6 mTorr, with the result that hydrogen was incorporated into the substrates. In the present investigation, films of Si-Ge were produced by RF co-sputtering from separate Si and Ge targets, in the absence of hydrogen. Experimental The fused silica substrates were cleaned using a neutral detergent (TeePol, BDH) followed by rinsing with deionised water and immersion in isopropyl alcohol in an ultrasonic bath for 10 min.They were then dried in nitrogen and finally heated to 90 "C in air for 30 min, before being cooled, ready for use. Si-Ge films were deposited onto the fused silica substrates, using an RF co-sputtering unit (RF Applications Ltd.). The substrates were secured to a water-cooled turntable nkounted above the sputtering targets (Fig. 1).Argon gas, at a pressure of 60 mTorr, was fed constantly at 20 sccmt into the chamber during deposition. The sputtering targets were first sputter cleaned in an argon atmosphere to remove oxide. Throughout this process, shutters were used to protect the fused silica from contamination.During deposition of Si-Ge films, the magnetron sources were at the following powers: 100W for Ge, 150 W for Si. This resulted in an overall deposition rate of 10 nm min-'. -f Standardcm3 min-'. I J. MATER. CHEM., 1994, VOL. 4 water-cooled turntable Fig. 1 Preparation of Si-Ge films by RF co-sputtering Optical measurements of the samples were performed over the range 347-820 nm, using an optical spectrometer (PYE Unicam). This instrument was modified to perform both transmission and reflection measurements. The optical absorp- tion coefficient, SI was calculated from 100-R 1 =In (7)-a dcm -1 where T and R are the percentage transmission and reflectivity, respectively, and d is the alloy thickness measured by surface profilometry (DEKTAK, Sloan Technology Corporation).A chrome blank (type AR3, Hoya Corporation) from which the resist had been removed to reveal a continuous film of chromium, was also measured as a representative comparison of a standard photomask. The adhesion behaviour of the films was investigated by a simple purpose-built scratch test device, shown schematically in Fig. 2. This accommodated the substrates under test mounted on an alignment table incorporating two micro- meters. A load was applied to a diamond stylus perpendicular to the substrate. The substrate was moved against the station- ary stylus by means of the micrometers and examined by optical microscopy. The applied load was increased in small steps until the Si-Ge or chromium films began to lose adhesion.A novel method of observing the interfacial stress between the opaque layer and the underlying fused silica was performed by using cantilevers of SiO, fabricated on an Si wafer by photolithography4 (Fig. 3). Reactive ion etching (RIE) of the Si-Ge films was performed in a custom-built etcher (RF Applications Ltd.) using a CF4-5% 0, gas mixture. load mond counterbalanceIlls substrate microme Fig. 2 Simple purpose-built scratch test device Fig. 3 Specially fabricated cantilevers with zero stress Results and Discussion Deposition of Si-Ge Films Samples of Si, Ge and Si-Ge were produced. The pressure in the chamber had a significant effect on their uniformities, e.g.the non-uniform area of the sputter films was clearly visible on square substrates with dimension of 7.6 cm side, at sputter- ing pressures below 30 mTorr. Above 30 mTorr, the non-uniformity was much less pronounced, being seen as an array of interference fringes. Visibility of these fringes could be enhanced by depositing a layer of chromium onto the fused silica prior to Si-Ge sputtering. Satisfactory uniformity was obtained only at pressures of 60mTorr (and above), but higher pressures carry the disadvantage of low deposition rate. For this reason 60mTorr was adopted as the standard sputtering pressure. Deposition rates of Si, Ge and Si-Ge, at various powers are shown in Fig. 4. The film thicknesses of samples produced at different power settings are all directly proportional to the deposition time.As expected, the depos- ition rate increases as the sputtering power is increased. The deposition rate of Si is 22% higher than that of Ge, for the same power (100 W). The Ge composition in the Si-Ge films at a given power ratio could be estimated from the deposition rates of Si and Ge. For example, when the power ratio is 150:100, the deposition rates of Si and Ge are 6.28 and 3.03 nm min-', respectively, resulting in the Ge composition of the film being 32.6%. This has been confirmed by electron- induced X-ray analysis (EDX). Optical Absorption Coefficients The transmission and reflectivity of sputtered Si, Si-Ge and chromium (from a standard photomask) were measured and t c --.E UJ a,c x0 ._s 0 10 20 30 40 50 60 70 deposition time/min Fig.4 Deposition rates: (a) Si (100 W), (b)Si (1 50 W), (c)Ge (100 W), (d)Si-Ge(150W:lOOW) J. MATER. CHEM., 1994, VOL. 4 their optical absorption coefficients plotted on a linear scale against wavelength as shown in Fig. 5(a). Fig. 5(b)shows the optical absorption coefficient plotted logarithmically against photon energy. The standard chromium (Cr) and sputtered Si have the highest and the lowest absorption coefficients, respectively. The Si and Si-Ge are capable of absorbing deep UV radiation used during fabrication of circuit devices, but neither may be compatible with existing inspection and align- ment systems, which requires absorption coefficients of ca.7 x lo5cm-I for films 100 nm thick. The absorption coefficient of Si-Ge films (containing 32.6% Ge) is 1.5 x lo5cm-I whereas the standard Cr gives 5.6 x lo5cm-l. By increasing the Ge content in Si-Ge films, higher absorption coefficients can be achieved; however, initial chemical stability tests suggest that Ge-rich films are highly soluble in aluminium etch solution (a mixture of nitric, acetic and orthophosphoric acids) and certain alkaline chemicals. This could damage the Si-Ge films during photomask or integrated circuit pro- duction should such etches be encountered during processing. However, as a dry (anisotropic) etch process is to be used, vertical walls and thus good pattern definitions should be possible in thicker films of Si-Ge, allowing the absorbance to be increased by this means. Interaction between deposited Films and Fused Silica Substrates The simple scratch test involved moving a coated substrate against a diamond stylus and measuring the load applied to the stylus when loss of adhesion occurred. The load needed to remove 100nm of Cr (defined as 100%) was compared with that necessary to remove various thicknesses of Si-Ge.For Si-Ge layers of similar thickness to Cr, 80% of the load was required. This increased to 99% as the Si-Ge thickness was reduced to 50 nm. However, films having three times the a Cr 6 4 2 SiGe\ Cr thickness exhibited extremely low adhesion to the sub- strates. The resultant scratch tests on standard Cr and Si-Ge films are shown in Fig.6 and 7, respectively. The Cr shows a well defined scratch track which seems to have been ‘scooped’ up by the diamond stylus without any evidence of flaking of the coating. For Si-Ge of a similar thickness, flaking of the film is evident and the scratch track is not smooth and well defined. The flaking is thought to be due to lower elastic strain energy in the Si-Ge films: instead of a continuous film being peeled, a ‘hammering’ effect is induced in the stylus which shatters the film into small fragments; therefbre the direction of the scratch is altered by the recoil of the stylus and the resulting scratch track is not straight and smooth. In order to observe interfacial compatibility between deposited films and fused silica substrates, specially fabricated cantilevers were used., Fig. 8 and 9 show a comparison of the behaviour exhibited by Cr and Si-Ge films of similar th tckness.In the former case, the pronounced upward bending of the cantilever demonstrates significant tensile stress, whereas in the latter case the cantilevers show only a small downward movement, indicative of modest compressive stress. Etching Behaviour of Si-Ge Films Si-Ge films coated with photoresist were patterned by using photolithography and reactively ion etched using CF,-5% O2at 70 mTorr, 50 W and 60 sccm. The etch rate was 200 nm Fig. 6 Simple scratch test on 100 nm thick Cr showing well defined -\scratch track 0 I I I Si 1 1.5 2 2.5 3 3.5 4 photoenergy/eV Fig.5 (a) Optical absorption coefficients (linear) as a function of wavelength. (b) Optical absorption coefficients (logarithmic) as a Fig. 7 Scratch test on 96 nm thick Si-Ge showing poorly defined function of photon energy. scratch track J. MATER. CHEM., 1994, VOL. 4 Fig.8 Upward bending produced by the tensile stress between Cr and the SiOz cantilevers Fig. 9 Downward bending of cantilevers of deposited Si-Ge on SO,, showing modest compressive stress min-'. Etch depths were recorded by means of a Dektak profilometer. In order to observe the edge profiles of etched Si-Ge, samples were prepared in a similar manner to that used for the films described above but on an Si wafer substrate rather than on fused silica.The testing patterns could be cleaved cleanly along the wafer crystalline planes to reveal their cross- sections. A thin layer of gold was then evaporated onto the wafer to dissipate charging effect when the sample was examined under a scanning electron microscope (SEM). Preparation of Cr edge profiles was performed by a similar method except that wet etching was used to define the pattern. Fig. 10 shows the resultant edge profile of the wet-etched Cr (an isotropic process). This process attacks the Cr layer equally in all directions and results in undercut of the resist protecting the Cr with consequent narrowing of the features. Fig. 11 shows a sharp and well defined edge profile produced by RIE of Si-Ge. The process can be seen to cause etching significantly faster in the vertical direction than in the hori- zontal, in accordance with the anistropic nature of the RIE technique.Discussion Si-Ge films have the potential to replace Cr as a photomask opaque. However, a number of aspects of this material may require further improvements and investigations in order to Fig. 10 Edge profile of wet-etched Cr (isotropic process) Fig. 11 Edge profile produced by RIE of Si-Ge (anisotropic process) satisfy the requirements of current photomask manufacturers and users fully. Optical, physical and chemical experiments need to be carried out on the influence of Ge composition on Si-Ge films. In addition, the measurements involving chemical solu- bility and the strain gauge cantilevers should be quantified.An optimum Ge composition should be established so that the Si-Ge films have maximum optical absorption coefficients at 633 nm, the wavelength used in inspection and alignment systems, while maintaining chemical resistance to metal and organic etches. It is well known that the hydrogen incorporated into amorphous Si and Ge films can alter the distribution of defect states, and change the optical gap. This can reduce the interfacial stress when Si-Ge is deposited onto the fused silica substrates, but the optical gap will have a tendency to increase, thus reducing opacity of the film. Note that when reactive ion etching of Si-Ge was performed in the presence of poly(butene sulfone) (PBS), a widely used electron beam resist, poor selectivity was observed between the two.However, this situation can be improved by exposure of PBS to oxygen5 or nitrogen6 plasmas. Conclusions This study has confirmed the potential attractions of Si-Ge as a photomask opaque. However, it has highlighted also a number of features which require further investigation. J. MATER. CHEM., 1994, VOL. 4 397 The work has been supported under the Joint European Sub- micron Silicon Initiative (JESSI) to whom the authors are grateful. Thanks are also due to N. Holmes, Compugraphics International Ltd., for his constructive comments on this manuscript and to the Electron Microscopy Group in Dundee 2 3 4 5 6 K. C. Kao, R. D. McLeod, C. H. Leung, H. C. Card and H. Watanabe, J.Phys. D, 1983,16,1801. H. Watanabe and K. C. Kao, J. Vucuum SOC., Jpn., 1981,24,417. R. Keatch and B. Lawrenson, this conference. W. M. Mansfield, J. Am. Chem. SOC., 1987,346,317. W. A. Loong and H. W. Chang, Electronics Lett., 1991,21. 541. University for their assistance in measuring film compositions. Paper 3/04293F; Received 21st July, 1993 References 1 W. I. Lehrer, US Put., 3,830,686, 1974; D. B. Fraser, US Patent No. 3,975,252, 1976; Fuji Photo Film Co. Ltd., Br. Put. 1,481,623, 1977.

ISSN:0959-9428    

DOI:10.1039/JM9940400393

出版商:RSC    

年代:1994

数据来源: RSC