Size‐Dependent Room Temperature Oxidation of Tin Particles

Using transmission electron microscopy, the size‐dependent room temperature oxidation of tin nanoparticles is studied. The oxide that forms during room temperature oxidation of Sn particles is amorphous SnO, and it retains this stoichiometry and structure over extended time periods. From the investigation of arrays of Sn nanoparticles with broad size distribution, under identical conditions, the Sn oxide thickness is evaluated as a function of size and oxidation time. The oxide thickness depends strongly on the size of the Sn nanoparticles, which is in excellent agreement with predictions for a Mott–Cabrera model corrected for a non‐uniform electric field. The results demonstrate the accelerated oxidation kinetics of nanoscale particles with high curvature, due to the amplified electric field at the interface to a continuously shrinking metal core.     

Microstructure evolution of room-temperature-sputtered ITO films suitable for silicon heterojunction solar cells

Thickness influence on structural, optical and electrical properties of sputtered indium tin oxide (ITO) with thickness ranging from 60 up to 430 nm films has been studied. At the increase of the film thickness crystallinity degree and grain size increased, whereas tensile structural distortion as well as resistivity decreased. It was observed that a microstructure evolution takes place: the initial amorphous layer evolved in polycrystalline phase, with a grain–subgrain surface morphology. Carrier concentration increased at the increase of the film thickness and a general relationship between electrical characteristics and structural distortion has been found. In thinner films larger tensile distortion allowed to include larger amount of interstitial O and/or Sn atoms in the lattice. An appreciable impact of the thickness was also observed on electro-optical properties in terms of changes in energy gap, resistivity and optical absorption. Silicon heterojunction solar cells have been produced and J_sc as high as 33.0 mA/cm² has been obtained.     

Enthalpy Relaxation Study of Poly(Vinyl Chloride) Films Based on the Time-Temperature Superposition Principle

Abstract

In the enthalpy relaxation of poly(vinyl chloride), a decrease in enthalpy upon the isothermal ageing was measured using the differential scanning calorimetry method as a function of ageing time (t_A) and ageing temperature. The range of the ageing temperature was from 56?°C (T_g ? 25?°C) to 72?°C (T_g ? 9?°C) where T_g denotes the glass transition temperature. The limiting value of the decrease in enthalpy was determined by applying a stretched exponential function to the measured enthalpy data. The relaxation function (?) was derived from the measured enthalpy and the construction of a master curve was tried by shifting the ? ? t_A curves of the respective ageing temperatures horizontally. Although there was no agreement between the shift factors (a_T) and the relaxation times of the ? ? t_A curves, the superposition was successfully constructed and the a_T values obtained for the poly(vinyl chloride) sample were found to be comparable to those reported for viscoelastic experiments over a broad temperature range above and below T_g carried out for different polymers. The origin of the decrease in enthalpy was briefly discussed in terms of the chain dynamics in the isothermal condition.     

多相双金属Pt-Sn/γ-Al2O3催化的胺N-烷基化反应合成仲胺和叔胺

基于借氢策略、醇为烷基化试剂的胺的N-烷基化反应是合成胺类化合物的绿色途径.在无外加氢源条件下,多相双金属Pt-Sn/γ-Al2O3催化剂可高效催化醇为烷基化试剂的伯(仲)胺的N-烷基化反应合成仲(叔)胺,反应副产物为水与极少量亚胺.催化体系的底物适应性好,目标产物收率高;催化剂可以循环使用,具有潜在的工业化应用前景.     

银纳米晶对铒镱共掺的TeO2-WO3-La2O3微晶玻璃发光性能的影响

通过熔融退火的方法以及热处理技术制备得到含有Er₂WO₆,La₂WO₆晶体的TeO₂-WO₃-La₂O₃-Er₂O₃-Yb₂O₃微晶玻璃,该玻璃具有优异的上转换发光性能。结果表明,在含银纳米晶的碲酸盐微晶玻璃中,银纳米晶和微晶的析出情况与银纳米晶的引入方式和热处理温度有关。经过390℃下15 min的热处理后,AgCl和AgNO₃共掺的碲酸盐微晶玻璃比单掺AgCl或AgNO₃的碲酸盐微晶玻璃具有更高的发光强度。银纳米晶与微晶的引入可协同提高碲酸盐玻璃的上转换发光性。     

SYNERGISTIC MODIFICATION OF EPDM AND CROSSLINKING AGENT IN IMMISCIBLE BLENDS OF POLYVINYL CHLORIDE WITH LOW DENSITY POLYETHYLENE

The synergism of ethylene-propylene-diene monomer copolymer （EPDM） and dicumyl peroxide （DCP, a crosslinking agent） in low density polyethylene （LDPE）/poly（vinyl chloride） （PVC） blends was investigated. When EDPM and DCP are added to the blends simultaneously, the tensile properties could be improved significantly, especially for the blends with LDPE matrix. For example, incorporation of 10/1 （mass ratio） EPDM/DCP improves the tensile strength of the LDPE/PVC （mass ratio 80/20） blend from 7.9 MPa to 8.5 MPa and the elongation at break from 25% to 503%. Results from selective extraction, phase-contrast microscopy and thermal analysis reveal that the improvement in the tensile properties of the blends with LDPE matrix is principally due to the formation of a fine crosslinking network of the LDPE and EPDM phase. The outstanding modification effect of EPDM is explained by its dual functions： molecular entanglement with LDPE and the enhanced efficiency of DCP in the blends.     

Book Review

Abstract

A Guide to Organophosphorus Chemistry, by Louis D. Quin, an internationally recognized authority, published by John Wiley and Sons (http://www.wiley.com/chemistry) ISBN 0-471-31824-8, $94.95, 394pp.

Aminophosphonic and Aminophosphinic Acids: Chemistry and Biological Activity. Editors: Valery P. Kukhar (Ukrainian Academy of Sciences) and Harry R Hudson (University of North London). Published by John Wiley and Sons Ltd., Chichester, UK, on 31 March, 2000. ISBN 0 471-89149-5, 175.00 Pounds sterling, 634 pages.

Phosphorus Ylides. Chemistry and Application in Organic Synthesis, by Oleg I. Kolodiazhnyi. Published by Wiley-VCH, 1999, ISBN 3-527-29531-3, 220SF, 555 pages.     

Synthesis and Characterization of Dichlorotin(IV)trithiophosphates and Their Adducts with Nitrogen Donor Bases

Abstract

Dichlorotin(IV)trithiophosphates [(RO)P(S)S ₂ ]SnCl ₂ were prepared by the reaction of methanolic solution of SnCl ₄ and dipotassium salt of trithiophosphates in a 1:1 molar ratio and their adducts [(RO)P(S)S ₂ ]SnCl _2.N ₂ C ₁₂ H ₈ and [(RO)P(S)S ₂ ]SnCl _2.N ₂ C ₁₀ H ₈ were prepared by the reaction of methanolic solution of [(RO)P(S)S ₂ ]SnCl ₂ and N-donor bases in a 1:1 molar ratio. These newly synthesised derivatives have been characterized by elemental analysis; molecular weight measurements; and IR, ¹³ C, ³¹ p and ¹¹⁹ Sn NMR spectral studies. Coordination number of four and six was suggested for dichlorotin (IV)trithiophosphates and their adducts with N-donor bases respectively.     

The Synthesis and 31P NMR Spectral Studies of Cyclophosphazenes

A modified method for preparing large-scale quantities of pure hexachlorocyclophosphazene (N₃P₃Cl₆) and octachlorocyclotetraphosphazene (N₄P₄Cl₈), phosphorus pentachloride with ammonium chloride, in the presence of zinc chloride, has been developed. The time of the reaction and the quantities of the catalyst are also studied. It is found that the optimum reaction time is 1.5 h and by-products are remarkably reduced by addition of 10% zinc chloride. As indicated by the ³¹ P NMR spectra, the synthesis and separation of cyclophosphazenes can be accomplished in moderate yield of tetramer (39%) and good yield of trimer (83%).