ISSN:0023-4753    

DOI:10.1002/crat.19750100902

出版商:WILEY‐VCH Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractThe details of well developed schlieren textures have been observed at smectic C and B modifications. In these textures whole numbered point singularities occur and inversion walls with strong similarities to nematic schlieren textures. It is shown that the occurrence of smectic schlieren textures is due to suppositions derived theoretically by Nehring and Saupe. These suppositions are: tilted structure and plane layers with the layers parallel to the supporting glass slides.In smectic B inversion walls occur which allow to conclude on variable tilt angles of the structure.

ISSN:0023-4753    

DOI:10.1002/crat.19750100903

出版商:WILEY‐VCH Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractThe convolution molecule method by Hoppe and Paulus yields sometimes several solutions for the orientation of the molecule. For the selection of the correct orientation a special kind ofRvalue (meanRvalue) can give valuable information.

ISSN:0023-4753    

DOI:10.1002/crat.19750100904

出版商:WILEY‐VCH Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractN‐Methyl‐piperidinium‐acet‐para‐brom‐anilid‐jodid kristallisiert in der triklinen Raumgruppe P1mit zwei Formeleinheiten C14H20N2OBrJ und zwei H2O‐Molekülen in der Elementarzelle. Die Gitterkonstanten sinda= 8,950 Å,b= 14,721 Å,c= 7,440 Å, α = 80,19°, β = 112,57° und γ = 106,82°. Mit Hilfe der Röntgenkristallstrukturanalyse wurden die Molekülstruktur der Verbindung bestimmt und die Wechselwirkungen zwischen den Molekülen im Kristall erforscht. Insbesondere wurde der Einfluß des im Kristall eingelagerten Wassers auf

ISSN:0023-4753    

DOI:10.1002/crat.19750100905

出版商:WILEY‐VCH Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractPresent paper deals with the preparation of V2O5single crystals, both pure and doped with Mg, Mn, and Fe respectively, by the method of zone melting. To verify the quality of crystals, measurements of electric conductivity were carried out in the direction perpendicular to cleavage plane (010). The results have shown that the prepared crystals are suitable for further investigation of physical properties.

ISSN:0023-4753    

DOI:10.1002/crat.19750100906

出版商:WILEY‐VCH Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractIn this paper the growth of AlxGa1–xAs layers with nearly constant composition along their thickness is described. By means of electroluminescence and cathodoluminescence measurements recombination mechanisms connected with the presence of Si are discussed. The aging behaviour of the light emitting diodes is supposed to depend on the AlAs content of the layers and to be connected with the diffusion of acceptors in the p‐n junction reg

ISSN:0023-4753    

DOI:10.1002/crat.19750100907

出版商:WILEY‐VCH Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractEs wird die Zugfestigkeit aus der Gasphase erhaltener und mit Platin dotierter Si‐Whisker untersucht. Der Bruchmechanismus der Whisker wird untersucht, verschiedenen Modelle werden betrachtet und in Abhängigkeit vom Dotierungsgrad ihre Anwendbarkeit diskutie

ISSN:0023-4753    

DOI:10.1002/crat.19750100908

出版商:WILEY‐VCH Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractDie mittlere quadratische Auslenkung der Atome im Al1–xGaxAs Mischkristall (x = 0,16) wurde bestimmt durch die Messung der integralen Reflexintensitäten von polykristallinem Material bei Zimmertemperatur. Die röntgenografische Debye‐Temperatur des Mischkristalls wurde ermittelt. Die mittlere quadratische Auslenkung der Al‐Atome ist kleiner als die der Ga/As‐Atome im Misc

ISSN:0023-4753    

DOI:10.1002/crat.19750100909

出版商:WILEY‐VCH Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractThe precipitation of basic nickel carbonate hydrates was studied from nickel sulphate solutions (concentrations 0.05 M to 1 M) at 96°C, by addition of sodium carbonate, bicarbonate‐carbonate and bicarbonate solutions. Precipitate compositions were determined by chemical analysis, thermogravimetric analysis, differential calorimetry and i.r. spectrophotometry; approximate final crystallite sizes and numbers were estimated from combined sedimentation and porosity measurements on precipitate aggregates.Nucleation, and then crystal growth, started after some ‘criticalpH’pH= 7.05 to 7.67 (at CO3−−/Ni++ratio = 0.08–0.12); the solutionpH then remained constant (until the CO3−−/Ni++ratio = 0.8) and then rose to some final value. Nucleus numbers, and thence final crystallite numbers, decreased with increasing bicarbonate content of the precipitating solution and decreasingpH.Precipitate compositions did not vary significantly with reacting ion concentrations but the Ni(OH)2/NiCO3ratios decreased from 2 to 1.4 with decreasingpH: thermal analysis and i.r. spectrophotometry confirmed that the final precipitates were mixtures of olated nickel carbonates and not nickel carbonate‐nickel hydroxide mixtures.Final crystallite sizes of the precipitates from 1 M solutions varied approximately from 0.095 to 0.14 micron, for

ISSN:0023-4753    

DOI:10.1002/crat.19750100910

出版商:WILEY‐VCH Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractThe precipitation of barium strontium, calcium, magnesium, zinc, cadmium and lead, manganese, cobalt, nickel and copper 8‐quinolinolates (‘oxinates’) was studied from equivalent solutions, atpHs from 4.5 to 10, by optical microscopy: the metal cation and overall ‘oxinate’ with ‘oxine’ concentrations were varied from 0.0002 to 0.020 M (while the mean metal oxinate concentrations varied from 10−7to 0.001 M). Crystal growth started after induction periods; the precipitations were heterogeneously nucleated at low supersaturations and homogeneously nucleated at medium to high supersaturations. The final precipitate crystal numbers depended on the number of nuclei formed during the induction periods. Crystal numbers at medium to high supersaturations increased with increasing initial metal oxinate concentration according to the relation,The final crystal lengths in this supersaturation range then decreased (from maximum values) with increasing initial mean metal oxinate concentration according to the relation,For precipitation from solutions of any concentration at anypH, smaller crystals were generally obtained in the precipitates from solutions of the metal oxinate of l

ISSN:0023-4753    

DOI:10.1002/crat.19750100911

出版商:WILEY‐VCH Verlag    

年代:1975

数据来源: WILEY