Effect of the addition of ultrafine aluminum powders on the rheological properties and burning rate of energetic condensed systems

The effect of small additives (1.25–5.00%) of ultrafine aluminum powders (UFAP) on the rheology and combustion of model four-component energetic condensed systems is studied. It is found that the addition of UFAP decreases the temperature of HMX decomposition. Small additives of UFAP increase the burning rate of model energetic condensed systems and decrease the exponent ν in the burning rate law without deteriorating the rheological characteristics of the model propellants. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 1, pp. 54–59, January–February, 2007.     

Surface nanocrystalline Si structure and its surface passivation for highly efficient black Si solar cells

19.5% conversion efficiency crystalline silicon (Si) solar cells having simple structure without antireflection coating have been fabricated using the surface structure chemical transfer method which produces a nanocrystalline Si layer simply by contacting catalytic platinum with Si wafers in hydrogen peroxide plus hydrofluoric acid solutions. The reflectivity becomes less than 3% after the surface structure chemical transfer method due to formation of black Si. Deposition of phosphosilicate glass and heat treatment at 925 °C performed for formation of pn‐junction effectively passivate the nanocrystalline Si surface. With this phosphosilicate glass passivation plus the hydrogen treatment at 400 °C, the internal quantum efficiency is greatly improved and reaches 81% at a wavelength of 400 nm. Analysis of ellipsometry data shows that incident light with wavelength shorter than 400 nm is almost completely absorbed by the nanocrystalline Si layer. The high internal quantum efficiency for short wavelength light is attributed to effective surface passivation and the nanocrystalline Si layer band‐gap energy which decreases with the distance from the top of the network structure of the nanocrystalline Si layer. Copyright © 2017 John Wiley & Sons, Ltd.     

Minimizing the surface effect of PDMS–glass microchip on polymerase chain reaction by dynamic polymer passivation

Polydimethyl siloxane (PDMS)–glass microchip has a very strong surface effect on polymerase chain reaction (PCR), leading to a very poor PCR yield. In the work reported here, practical dynamic passivation of surfaces of PDMS–glass microchip using polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP) was achieved using a conventional thermocycler. The passivation procedure was cost‐effective and easy to conduct. The effects of polymer molecular weight and polymer concentration on tube PCR efficiency were investigated primarily to prescreen out suitable polymers and polymer concentrations in the PCR mixture. The result from tube PCR indicated that both PEG and PVP could affect the performance of Taq polymerase. A final concentration of 0.025% (w/v) or 0.4% (w/v) polymer in the PCR mixture can enhance the tube PCR, while 1% (w/v) polymer was found to inhibit the reaction. PEG was more effective in tube PCR, although PVP performed better in chip PCR. Instead of employing the polymer directly in the PCR mixture, i.e. the conventional in situ passivation approach, another approach of dynamic passivation by pre‐injecting polymers into the microchip achieved better performance. The efficiency of pre‐passivation was found to follow the order: PVP10000>PVP55000, PEG8000> PEG10000>PEG400. After pre‐passivation with PVP10000, PVP55000 and PEG8000, the PCR efficiency can recover to 93%, 86% and 83%, respectively, of that obtained from tube PCR. Copyright © 2006 Society of Chemical Industry     

电镀锌钝化处理耐蚀效果的电化学评估

采用线性极化电阻、开路电位及阳极极化曲线等电化学方法,评估了锌镀层经3种不同钝化液处理后在w=1%的NaCl溶液中的耐蚀性。结果表明,3种电化学方法测得的钝化膜耐蚀性与中性盐雾试验的结果相符,能够用于快速有效地评价电镀锌钝化处理的耐腐蚀效果。     

Oxidation of Inconel 718 in Air at High Temperatures

Experiments were conducted with Inconel 718 at high temperatures to evaluate the rate of oxidation of the material over as wide a temperature range as possible, as well as to determine the high-temperature failure limit of the material. Samples of Inconel 718 were inserted into preheated furnaces at temperatures ranging from 973 to 1620 K and oxidized in air for varying periods of time. After being oxidized in air at a constant temperature for the prescribed time and then being allowed to cool, the samples were reweighed to determine their mass gain due to the uptake of oxygen. From these mass-gain measurements, it was possible to identify three regimes of oxidation for Inconel 718: a low-temperature regime in which the samples behaved as if passivated after an initial period of transient oxidation, an intermediate-temperature regime in which the rate of oxidation was limited by diffusion and exhibited a constant parabolic rate dependence, and a high-temperature regime in which material deformation and damage accompanied an accelerated oxidation rate above the parabolic regime.     

Zinc-phthalocyaninetetraphosphonic acid as a novel transparent-conducting-oxide passivation for organic photovoltaic devices

A novel monolayer chemical passivation improving the surface electronic properties of indium-tin oxide (ITO), used as an electrode in organic solar cells (OSC), is reported. Deposition of zinc-phthalocyaninetetraphosphonic acid on ITO substrates, from a water solution, creates a chemically bound organic monolayer passivation, which improves the charge transfer through the ITO/zinc-phthalocyanine (ZnPc) interface in ZnPc/C₆₀ OSC. Current–voltage measurements on devices produced on such substrates show improved serial and parallel resistances as well as fill factor, compared to OSC on non-passivated substrates. The use of this novel passivation for electrodes allows to dispose off the additional conventional PEDOT:PSS buffer layer.     

镀锌层银盐黑色钝化故障处理

给出了镀锌层银盐黑色钝化的工艺流程及配方,介绍了钝化液中各组分的作用。分析了钝化过程中的常见故障及解决方法,提出了钝化时的注意事项。     

Influence of Si<Subscript>3</Subscript>N<Subscript>4</Subscript> passivation on surface trapping in SiC metal-semiconductor field-effect transistors

The SiC metal-semiconductor field-effect transistors (MESFETs) have been reported to have current instability and strong dispersion caused by trapping phenomena at the surface and in the substrate, which degrade direct-current (DC) and radio-frequency (RF) performance. This paper illustrates the change in electrical characteristics of SiC MESFETs after Si₃N₄ passivation. Because of a reduction of surface trapping effects, Si₃N₄ passivation can diminish current collapse under pulsed DC conditions, increasing the RF power performance. The reduction of surface trapping effects is verified by the change in the ratio of the drain current to the gate current under pinch-off conditions.     

Interfacial reactions of chalcopyrite in ammonia–ammonium chloride solution

The interfacial reactions of chalcopyrite in ammonia–ammonium chloride solution were investigated. The chalcopyrite surface was examined by scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) techniques. It was found that interfacial passivation layers of chalcopyrite were formed from an iron oxide layer on top of a copper sulfide layer overlaying the bulk chalcopyrite, whereas CuFe_1–xS₂ or copper sulfides were formed via the preferential dissolution of Fe. The copper sulfide layer formed a new passivation layer, whereas the iron oxide layer peeled off spontaneously and partially from the chalcopyrite surface. The state of the copper sulfide layer was discussed after being deduced from the appearance of S^2–, S^2?₂, S^2?_n, S⁰ and SO^2?₄. A mechanism for the oxidation and passivation of chalcopyrite under different pH values and redox potentials was proposed. Accordingly, a model of the interfacial reaction on the chalcopyrite surface was constructed using a three-step reaction pathway, which demonstrated the formation and transformation of passivation layers under the present experimental conditions.     

无铬复合钝化膜的微观组织结构及耐腐蚀性能

目的解决热镀锌钢板表面六价铬钝化工艺所产生的环境污染问题。方法以钼酸铵、纳米硅溶胶、单宁酸、硅烷偶联剂KH151和KH792为主要原料配制新型环保的无铬复合钝化液,在镀锌板表面制备钝化膜。采用扫描电子显微镜(SEM)、能谱仪(EDS)和X射线光电子能谱仪(XPS)分析无铬复合钝化膜表面的微观形貌、元素组成和化学成分,用电化学工作站测试Mo元素对镀锌板耐蚀性的影响,使用中性盐雾实验研究不同皮模量时膜层的耐蚀性。结果无铬复合钝化膜中的Mo元素可以抑制微裂纹的产生和发展,阻挡腐蚀性介质向金属基体扩散,提高复合硅烷膜的电阻。复合钝化膜的电化学交流阻抗比硅烷钝化膜提高了1.6倍,与六价铬钝化膜接近,可以有效抑制腐蚀电化学反应的发生,降低反应速度,提高膜层的耐蚀性。皮膜量为892 mg/m2时,膜层的腐蚀面积为0,耐蚀性达到六价铬钝化膜水平;皮膜量为1252 mg/m2时,耐蚀性能优异。结论制备的无铬复合钝化膜结合了硅烷钝化膜和钼酸盐钝化膜两方面的优点,提高了膜层的致密性和结合性,膜层耐腐蚀性接近/达到了六价铬钝化的效果。