摘要:

AbstractA semiempirical PM3 quantum computational method has been used to generate the electronic and optimized geometrical structure of SWNT of zigzag and armchair types. We shed light on the electronic structures of SWNT with various diameters and lengths of the tube. Particularly, the calculated HOMO, LUMO and band‐gap of SWNT are not monotonic but exhibit a well‐defined oscillation, which depends on the tubular diameter and the tubular length. Calculated HOMO, LUMO and band‐gap of the zigzag SWNTs have oscillated with tubular diameter as they contain an odd or even number of benzenoids in the circular plane of the carbon nanotube. The zigzag SWNTs with an odd number of benzenoids have a higher band‐gap than those of SWNTs with an even number of benzenoids in the circular plane of the carbon nanotube. Calculated results also reveal that the tubular length in the zigzag SWNTs influences the band‐gaps very little. For the armchair SWNT, calculated HOMO, LUMO and band‐gap contained the oscillate depending on the number of carbon sections in the tubular length axis. Their repeat sections are 3n‐1, 3nand 3n+1. The armchair SWNT with 3n+1 sections has a high band‐gap while the SWNTs with 3n‐1 sections have a low band‐gap. The tubular diameters of armchair SWNT influence the HOMO, LUMO and b

ISSN:0009-4536    

DOI:10.1002/jccs.200300132

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractDensities have been measured for the CsCl‐saccharide (D‐glucose, D‐fructose)‐water systems at 298.15 K. These data were used to calculate the apparent molar volume of CsCl (Vφ,E) and the saccharides (Vφ,S), and the infinite dilution apparent molar volumeVφ,E0andVφ,S0in the studied solutions. In addition, the standard transfer volume ΔtVφ,E0of CsCl from water to aqueous saccharides solutions, and ΔtVφ,S0of saccharides from water to CsCl solutions have been evaluated and discussed using the structural interaction model. The volumetric interaction parameters for CsCl with saccharide in water were obtained and analyzed by the group additivity principle and the stereochemistry of the sacch

ISSN:0009-4536    

DOI:10.1002/jccs.200300133

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractA simple pencil and paper method to calculate the forces acting on individual atoms in a molecule, due to the electrons in the different populated molecular orbitals, has been developed within the Extended Hückel formalism. The method is applied to study the torsional stability around a single bond of some simple molecules. The results show good agreement with the experimental evidence of stable conformers

ISSN:0009-4536    

DOI:10.1002/jccs.200300134

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractThe reactions of norbornene polymerization were catalyzed by Pd(CH3CN)4(BF4)2(1), AIBN (2), and [{(2,6‐C6H3(iPr)2)N=C(Me)}2Pd(Me)(CH3CN)][BF4] (3) without using methylalumoxane (MAO). These poly(norbornene)s are readily soluble in organic solvents such as toluene, dichloromethane and tetrahydrofuran.According to the NMR data, the end group of PNA resulting from the AIBN process is found from THF. The PNT resulting from the catalyst (1) shows bi‐models of GPC bands (Mn= 4236 and 66317), two glass transition temperatures (Tg= 72.7 and 201.5 °C), as well as two decomposition temperatures (Td = 337 and 460

ISSN:0009-4536    

DOI:10.1002/jccs.200300135

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractThe insertion reaction of CS2with Mg(NR2)2(R= Et,iPr), MgR′2(R′= Et, Ph) and R″MgBr (R″=iPr, Ph) respectively lead solid products, Mg(S2CNR2)2(THF)n(1: R= Et, n=2;2: R=iPr, n=1), Mg(S2C′R)2(THF)2(3: ′R= Et,4: ′R= Ph), BrMg(S2C″R) (THF)3(5: ″R=iPr,6: ″R= Ph) in which the inserted carbon disulfides act as terminal chelating ligands. These compounds were characterized with1H,13C NMR, IR spectroscopy, mass spectrometry, elemental analyses, and X

ISSN:0009-4536    

DOI:10.1002/jccs.200300136

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractReaction of an alkyne‐bridged dicobalt complex, [Co2(CO)6(μ‐Me3SiC=Cpy)]4, with bis(diphenylphosphino)methylene (DPPM) or bis(diphenylphosphino)ethylene (DPPE) in THF at 55 °C yielded a DPPM or DPPE doubly bridged dicobalt compound, [{μ‐P,P‐PPh2CH2PPh2}Co2(CO)4(μ‐Me3SiC=Cpy)]5or [{μ‐P,P‐PPh2CH2CH2PPh2}Co2(CO)4(μ‐Me3SiC≡Cpy)]6. Compound5and6were characterized by spectroscopic means as well as X‐ray crysta

ISSN:0009-4536    

DOI:10.1002/jccs.200300137

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractWeight‐loss tests and electrochemical techniques are used to study the inhibition of BTA and Na2MoO4either individually or in different combinations for carbon steel in boiling 10.24 mol/L LiBr solution containing 0.07 mol/L LiOH. The result indicates the corrosion of carbon steel is effectively inhibited when BTA or Na2MoO4is added to the solution individually. The adsorptions of BTA or Na2MoO4on carbon steel surfaces can be well fitted to a Langmuir adsorption isotherm. The free energy of adsorption of BTA and Na2MoO4are −45.07 kJ/mol and −40.69 kJ/mol, respectively. The corrosion rate is decreased to the minimal value, which is 8.39 μm/y, when 7.28 × 10−4mol/L Na2MoO4and 8.39 × 10−4mol/L BTA are added to a 10.24 mol/L LiBr solution containing 0.07 mol/L LiOH. The inhibition mechanism of the above mixed inhibitors results from the complemental effect of the compact inner layer film composed of Fe‐BTA and the absorbed MoO42−in small quantity of the active site and the outer layer. The passive film of the coordination compound and the adsorbed MoO42−prevent Br−from absorbing and effectively decrease the corro

ISSN:0009-4536    

DOI:10.1002/jccs.200300138

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractLithiophorite consists of alternatively stacked MnO6octahedral sheets and LiAl2(OH)6octahedral sheets. Its applications in laboratories and industries have been hindered by sophisticated operation procedures, long reaction time, or impurities existing in the final product. We proposed a fast and simple method, mixing birnessite, aluminate and lithium hydroxide together (designated it as the BAL method) in high alkaline conditions (pH>13), and treating it hydrothermally at 423 K for 6 hours to prepare pure lithiophorite. A specific reaction between lithium cations and aluminate anions plays as a key role in the BAL method. Due to this specific reaction, LixAln(OH)m+zcomplexed cations can form and penetrate into interlayers of birnessite to replace sodium cations. In high alkaline conditions (pH>12), LixAln(OH)m+zcomplexed cations become smaller and are soluble. Thus, the higher alkaline LixAln(OH)m+zcomplexed cations can penetrate into interlayers of birnessite at a higher rate. Furthermore, impurities, such as lithium intercalated gibbsite (LIG), aluminum oxyhydroxides and aluminum hydroxides are not stable in high alkaline conditions. Consequently, pure lithiophorite can be easily obtained within 6 hours in high alkaline conditions.

ISSN:0009-4536    

DOI:10.1002/jccs.200300139

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractThe present work aims at studying the antiwear, antiseize and antioxidising properties of anode‐shielding corrosion inhibitors. The physicochemical properties of the inhibitors and those of the operation‐conservation motor oils modified with them were determined. It was found that these inhibitors improve the antiwear, antiseize and antioxidising properties of the motor oils obtained. Real‐life experiments were carried out with a four‐stroke four‐cylinder engine (“Skoda” Czech Republic) mounted on a 30‐ton fishing barge which uses diesel fuel containing up to 1,4% sulphur. The antiwear and antioxidising properties of the oils obtained were determined, and a probable action mechanism of the complex corrosion inhibitor

ISSN:0009-4536    

DOI:10.1002/jccs.200300140

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractElectrochemical behavior of an ITO/TiO2electrode both under ultraviolet (UV) illumination and in the dark was investigated using the methods of cyclic voltammetry and ac impedance spectroscopy. A new oxidative peak is observed at 0.15 V when the TiO2electrode was illuminated by UV light for a certain time. The peak current and the anodic photocurrent increased with the increase of UV light intensity. It is assumed that the new peak belonging to the oxidation of Ti3+, which was formed on the electrode surface during the UV illumination. It is also found that the apparent resistance was decreased but the capacitance was increased when the TiO2electrode was illuminated by UV light according to the measurement results of ac impedance. Based on the results in this paper, it was directly proved that Ti3+was actually formed when the electrode was irradiated by UV light.

ISSN:0009-4536    

DOI:10.1002/jccs.200300141

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY