An interpretation on the origin of the specular reflectance change caused by the submonolayer formation of foreign metals on some precious metal electrodes

The optical properties of foreign metal submonolayers formed on Au, Ag, Cu, Pt and Pd electrodes through the underpotential deposition have been investigated by specular reflectivity measurement. Based on the spectral characteristics, 14 adsorbate-substrate systems were classified into 2 groups. The first group, involving Bi on Au, Cu on Au, Pb on Au, Tl on Au, Tl on Ag and Cd on Cu, is characterized by the similarity of the optical properties of the adsorbed metal in the submonolayer to those of bulk metal. The first monolayer was found to form through several submonolayer stages, in which the optical constants are slightly different from each other. In the second group, involving Cd on Au, In on Au, Sn on Au, Ag on Pt, Bi on Pt, Cu on Pt, Pb on Pt and Bi on Pd, the spectra of submonolayer observed experimentally differ from those calculated with the assumption that the optical properties of adatom and substrate are the same as those of corresponding bulk metal. The difference in the work functions between adsorbate and substrate materials in this group is larger than those in the first group.From these findings, some considerations were made to interpret the origin of the specular reflectance change due to the presence of metal adlayer on the electrode surface. The results allow a tentative conclusion that the reflectivity change is predominantly attributed to the optical properties of the adsorbed submonolayer, but at the same time the work function of the substrate and the interband transition in visible should also be taken into consideration.     

颜料色浆的选择对外墙涂料耐候性的影响

探讨色浆的选择对外墙涂料色漆耐候性的影响因素。重点讨论色浆类型的选择对性能的影响,同一种颜色用不同的复合色浆对耐候性的影响,色浆与调色基础漆配方设计对耐候性的影响以及墙面基材对保色性的影响。     

聚丙烯酰胺在黑土上的吸附解吸特性研究

采用静态吸附法研究了聚丙烯酰胺在黑土上的吸附行为,考查了不同吸附时间对土壤吸附量的影响,得出了聚丙烯酰胺在土壤上的吸附等温线。并且研究了聚丙烯酰胺在黑土上的解吸行为,探讨了振荡时间、液固质量比、温度、pH值对黑土中聚丙烯酰胺解吸的影响。结果表明,聚丙烯酰胺在黑土上的吸附等温线符合Langmu ir吸附模式,饱和吸附质量比为1.17 mg/g,聚丙烯酰胺在土壤上有很强的吸附亲合力,在实验条件下,最大解吸量仅为总量的25%。     

热镀锌板的镀层成分对其表面电泳漆膜抗石击腐蚀性能的影响

研究了热镀锌板的镀层成分对其表面电泳漆膜抗石击腐蚀性能的影响。结果表明,经过合金化退火得到的GA板镀层中含有一定量的Fe,镀层较未经合金化退火的GI板硬。GA板镀层表面疏松多孔,电泳漆膜能够充满其缝隙或凹陷之处,固化后在界面区产生了类似勾键作用的机械作用力。因此,GA板与电泳漆膜的附着力优于GI板,石击处的扩蚀速率小于GI板。     

水合氧化铝阻燃EPDM/PP的性能研究

用氧指数测定和力学性能测定方法研究了水合氧化铝 ( ATH)的用量及粒径对共混物性能的影响。结果表明 ATH对 EPDM/ PP有一定的阻燃作用和消烟作用 ,但使其拉伸强度和断裂伸长率降低。随其用量增加和粒径变小 ,阻燃效果提高 ;粒径对阻燃性能的影响随用量增大影响也增大。少量使用 ATH时 ,粒径对拉伸强度影响不大 ,但对断裂伸长率影响明显 ;随用量增大 ,粒径对拉伸强度和断裂伸长率的影响也增大。     

Effect of the gypsum state in industrial cements on the action of superplasticizers

The reduction in mixing water of the concrete, caused by the addition of a superplasticizer, depends also on the type of cement used. Superplasticizer based on naphthalene sulfonated polymer acts much more effectively on cement containing gypsum dihydrate than on that containing calcium sulfate hemihydrate. Moreover, an improvement of the superplasticizer quality caused by ultrafiltration of the polymer, is more effective on the cement containing gypsum than on that with hemihydrate.     

High performance liquid chromatography of oxygenated cholesterols and related compounds

Twenty-four oxygenated cholesterols and structurally related compounds were analyzed by high performance liquid chromatography with silicic acid column and various mobile phases. Hexane–propanol was superior to hexane/tetrahydrofuran and hexane/ethyl acetate for the separation of oxygenated cholesterols. The retention volumes of oxygenated cholesterols depended on the characteristics of the substituting group, its position of substitution, as well as its orientation. The effect of various functional groups at different positions on cholesterol molecules, in general order of decreasing retention volumes, were: hydroxy on the ring, carbonyl on the ring, epoxy on the ring, hydroxy on the side chain, and carbonyl on the side chain. Synergistic effect of multiple hydroxyl substitutions on cholesterol was observed.     

三聚磷酸二氢铝对氨气的吸附动力学研究

在真空干燥器中,加入一定量待测气体的水溶液,保持真空干燥器中待测气体浓度恒定。利用此装置研究了氨气浓度、三聚磷酸二氢铝吸附大气和水蒸气后,对三聚磷酸二氢铝吸附氨气动力学的影响。结果表明,三聚磷酸二氢铝吸附氨气,可用一级动力学方程和Elovich动力学方程模型描述;氨水浓度对吸附量和平衡吸附时间有显著影响;三聚磷酸二氢铝吸附空气后,对吸附量和平衡吸附时间无影响;三聚磷酸二氢铝吸附水蒸气后,对吸附量和平衡吸附时间均有影响。     

Hydration of the surface of pure sulphur covered with n-alkanes

This paper presents the results of an investigation of the kinetics of adsorption and desorption of water on the surface of pure sulphur covered with n-alkanes. Changes of thermodynamic functions depending on adsorption values, as well as activation energy of water molecules were determined. On the basis of these results the effect of n-alkanes on the thickness of water layers formed on modified sulphur samples was shown. The mechanism of water adsorption here gives much information on the mode of molecule bonding on the sulphur surface.     

Electrocatalysts on supports—I. Electrochemical and adsorptive properties of platinum microdeposits on inert supports

Adsorptive and electrocatalytic properties of platinum microdeposits on high-melting metals (Ti, Ta, Zr and Nb) and gold have been studied. It has been found that hydrogen adsorption on such microdeposits is characterized by some lower mean bond energy. Hydrogen spillover has been observed on the samples of high-melting metals, however, its intensity is less than for samples of carbon materials with platinum microdeposits. The rate of cathodic hydrogen evolution on the microdeposits is higher than on massive platinum and increases as the particle sizes of microdeposits decrease. The properties of microdeposits in terms of hydrogen adsorption and evolution have been the same for samples of all examined metals both in the initial state and after being oxidized in air at temperatures of 550–650 K. Oxygen adsorption on the microdeposits has been characterized by a slightly elevated bond energy and has exceeded that on massive platinum. The rate of oxygen ionization on the microdeposits has been much less than on massive platinum due to almost complete conversion of the microdeposits into PtO. The rate of formic acid oxidation on platinum microdeposits only slightly depends on the potential and is governed by the rate of chemisorption. The exchange current of the redox reaction Fe³⁺ + e ? Fe²⁺ on platinum microdeposits on gold exceeds that on pure platinum and increases as the mean particle size of the microdeposits decreases. The features of the microdeposits found are explained by the assumption of their electronic interaction with support.     

Deactivation of the metal and acidic functions for Pt, Pt-Sn and Pt-Sn-K using physically mixed catalysts

The effect of K addition on the amount and dispersion of carbon deposition on metal sites and support sites was investigated on a physical mixture for hexane dehydrogenation. TPO, BET and ESR experiments were used for characterization. The K addition significantly decreases catalyst deactivation involving the amount of coke deposits and the density of carbon radicals on the metal and support sites because of ensemble and electronic effects, especially on the metal sites. Coke on the metal sites associated with carbonaceous species rich in hydrogen is less polymerized than coke on the support sites, corresponding to a more graphitic-like carbon.     

甲酸在钛基纳米多孔网状铂电极上的电化学氧化

将水热法和电解过程相结合，制备出一种新型的钛基纳米多孔网状铂电极(nanoPt)，它具有特殊的网络状结构及巨大的表面积. 循环伏安曲线表明,在碱性溶液中，甲酸在nanoPt上的氧化电流密度远远大于在多晶Pt上的电流密度，其氧化峰电流几乎是后者的100倍；恒电位电解时，甲酸在nanoPt上的氧化电流开始时随时间的增加而增加，随后达到稳定，其稳定电流也明显高于多晶Pt；在nanoPt上甲酸的非线性现象出现的电流密度范围要比在多晶铂上的宽. 多次循环扫描和长时间电解实验表明. 这种钛基nanoPt结构稳定，催化剂颗粒不易脱落，有可能作为一种新型的燃料电池阳极材料而得到应用.     

Ammoximation of ketones on titanium silicalite. A study of the reaction byproducts

In the new EniChem process cyclohexanone oxime is directly synthesized by ammoximation of cyclohexanone with ammonia and hydrogen peroxide on titanium silicalite catalyst. The ammoximation reaction is suitable for the synthesis of several oximes by reaction of the corresponding ketones with ammonia and hydrogen peroxide on titanium silicalite. New results on ketones ammoximation and on reaction byproducts are reported. The effect of some reaction parameters on the oxime yield and on byproducts formation is discussed.     

单液滴撞击超疏水冷表面的反弹及破碎行为

对直径2.8 mm的液滴撞击冷表面的动态行为进行快速可视化观测，对比研究单液滴撞击普通冷表面以及超疏水冷表面的动力学特性，同时对初始撞击速度以及冷表面温度对液滴动态演化行为的影响进行了对比分析。实验结果表明：与液滴撞击普通冷表面（温度-25~-5℃）发生瞬时冻结沉积相比，液滴撞击超疏水冷表面时均未发生冻结，而且伴随铺展、回缩、反弹以及破碎行为；撞击速度越大，普通冷表面上液滴铺展因子越大，而且液滴越易冻结。液滴低速（We≤76）撞击超疏水冷表面会发生反弹现象，但速度对液滴最大铺展时间无影响；液滴高速（We≥115）撞击超疏水冷表面后会产生明显液指，而且破碎为多组卫星液滴。此外，冷表面温度仅影响液滴反弹高度，对液滴最大铺展因子以及液滴铺展时间影响较小。结果表明超疏水表面可显著抑制液滴撞击冷表面的瞬时冻结沉积。     

Site Structure Sensitivity Differences for Dissociation of Diatomic Molecules

A review on the analysis based on our recent theoretical results on the site specific activation of CO, N₂ and NO on corrugated Ru surface is presented. We discuss the issues such as what should be the configuration of the active site for the optimum dissociation of the diatomic molecules?, How is the barrier dependent on the structure of the reaction path?, Whether the further steps involved in the reaction sequence dependent on the activation of the diatomic molecules?     

预分解窑生产中碱对熟料质量的影响

报告了国内某大型现代干法水泥厂预分解窑生产中碱对熟料质量的影响,这种影响导致熟料安定性不良,后期强度降低,对高碱熟料的岩相分析发现,碱对熟料矿物,特别是阿利特开貌具有明显影响,从保证熟料质量的角度提出了熟料中碱的限量标准。     

纤维水膜极板表面颗粒沉积脱落特性

以极板表面荷电颗粒电子传递及离子定向迁移为基础,对纤维极板表面沉积颗粒粒径分布、粉尘层堆积形貌、颗粒沉积脱落过程及关键影响因素等进行了研究,并与金属极板进行对比。结果表明：静电场同一位置处（取样点15）,纤维极板表面沉积颗粒物的粒度（6.900 μm）小于金属极板（9.018 μm）,纤维水膜极板对颗粒物的捕集效率更高;与金属极板不同,纤维水膜极板表面粉尘层堆积形貌与电晕电流密度分布无明显关联性。荷电颗粒是以纤维束凸出处为沉积中心,沉积并聚集成球或链珠状,粉尘层厚薄随机且分布松散;纤维极板液体表面浸润和内部扩散,减小了纤维极板表面与粉尘层间静电力,增大了粉尘层内颗粒间黏结力;流动曳力、液桥力、静电力、重力是纤维极板控制粉尘层脱落的关键因素。     

Modern carbon fibres from polyacrylonitrile (PAN)-polyheteroaromatics with preferred orientation

This contribution presents the mechanical data of high performance carbon fibres currently available on the market, based on experimental studies on stabilization and pyrolysis of PAN (SAF) from Courtaulds. The effects of stabilization and carbonization temperatures on the properties as well as on the ultra- and crystalline structures of the fibres are shown in more detail.     

Coke Formation on Pt?CSn/Al2O3 Catalyst in Propane Dehydrogenation: Coke Characterization and Kinetic Study

The influences of gas compositions on the rates of coke formation over a Pt?CSn/Al₂O₃ catalyst are studied. The coke formed on the catalyst is characterized by thermal gravimetric analysis, IR spectroscopy, Raman spectroscopy and elemental analysis. Two kinds of coke are identified from the TPO profiles and assigned to the coke on the metal and the coke on the support, respectively. The coke formed on the metal is softer (containing more hydrogen) than that formed on the support. The rate of coke formation on the metal is weakly dependent on the propylene and hydrogen pressures but increasing with the propane pressure, while the rate of coke formation on the support is increasing with the propane and propylene pressures and decreasing with the hydrogen pressure. Based on the kinetic analysis, a mechanism for the coke formation on the Pt?CSn/Al₂O₃ catalyst is proposed, and the dimerization of adsorbed C₃H₆ is identified to be the kinetic relevant step for coke formation on the metal.     

汽车空调行业ODS替代品的需求与预测

本文对中国汽车空调行业随轿车工业的发展而迅速发展及汽车空调CFC-12替代计划的实施做了简单的介绍,并就汽车空调ODS淘汰过程中的替代品HFC-134a和润滑油的变化进行了分析和需求量的预测。