Evolution of chemistry and morphology during the carbonization and combustion of rice husk

Both fine carbon/silica and pure silica powders can be obtained by carbonization and combustion of rice husk under non-isothermal conditions, and the products can be used for preparation of high-quality ceramic materials. Studies on the morphology, chemical and physical characteristics of products were carried out by N₂-adsorptionmeter, SEM, XRD, FTIR, ICP-MS and EA. Results indicate that decreasing the heating rate increased the specific surface area, pore volume and pore diameter. At a heating rate of 5 °C/min, the specific surface areas of both the carbon/silica and pure silica powders were 261 and 235 m²/g, and the average pore diameters were 2.2 and 5.4 nm, respectively. The products obtained from various heating rates were all amorphous. Thermogravimetric analysis was employed to study the reaction characteristics during carbonization or combustion, indicating that decomposition process of rice husk could be divided into three temperature zones. This results of the study can also provide the important information on the recovery of biomass material from rice husk.     

基于B/S的资料信息管理系统的设计和实现

该文介绍了基于B/S资料信息管理系统的设计和开发,重点阐述了资料信息管理系统的开发设计的难点和要点,同时提供了部分数据库表信息和代码。     

基于PHP和Ajax技术的在线网页闹铃的设计与实现

该文简单介绍了B/S网络应用开发架构,详细阐述了网页闹铃功能设计,并对原理进行了详细的讲解,对功能做了进一步的实现,展示了运行效果。     

Localized swelling of Fe-Cr-Ni alloy rollers in high-temperature applications

Localized swelling has been observed in 24Cr-24Ni-Nb steel transportation rollers used in the normalizing furnace of a plate mill after prolonged service at high temperature. Due to high localized thermal and mechanical stresses, the chromia layer formed on the roller surface ruptures, exposing the roller substrate to furnace oxygen. Oxidation of second-phase carbides results in the formation of carbon monoxide at very high partial pressure. This leads to formation of voids, leading in turn to localized swelling of the roller material.     

Thermophysical properties of a Ti–44%Al–8%Nb–1%B alloy in the solid and molten states

The families of titanium aluminide intermetallic alloys have attractive high temperature mechanical properties which make them potential candidate materials for a wide range of applications, particularly in the aeronautic and automobile sectors. The development of appropriate manufacturing techniques is an essential stage in the engineering exploitation of these materials, e.g., Induction Skull Melting is one of the techniques which needs to be optimised for the casting of titanium aluminides. Research is underway to develop a computer model of this process but data are required for the key thermophysical properties. Pulse-heating techniques have been used to measure properties for the Ti–44Al–8Nb–1B system. Rectangular samples have been prepared and are resistively heated as part of a fast capacitor discharge circuit. Time-resolved measurements with sub-μs resolution of currents through the specimen were made with a Pearson probe current monitor using the induction principle. Voltages across the specimen were determined with knife-edge contacts and voltage dividers, and radiance temperatures of the sample were measured with a pyrometer. These measurements allow the calculation of specific heat and dependencies between enthalpy, electrical resistivity and temperature of the alloy up into the liquid phase. Data for thermal diffusivity have been obtained by using the Wiedeman–Franz relation. The results are compared with those obtained using DSC and the four-probe method to measure the temperature dependence of the resistivity.     

镁合金废料的回收

在镁合金零部件生产过程中，特别是在压力铸造生产中，产生出来的废料以及使用后报废的镁合金零件逐渐增多。出于成本和环境因素的考虑，必须对这与日俱增的镁合金废料进行有效回收。本文以生产占90％的镁合金零部件压力铸造为主线，介绍镁合金废料回收的经济分析，镁合金废料的来源和分类、现行回收技术的现状及发展趋势。并介绍香港生产力促进局和重庆硕龙科技公司最近研究开发的一种新型镁合金废料现场精炼回收系统。     

The influence of sulphate-reducing bacteria biofilm on the corrosion of stainless steel AISI 316

This work investigates microbially-influenced corrosion (MIC) of stainless steel AISI 316 by two sulphate-reducing bacteria, Desulfovibrio desulfuricans and a local marine isolate. The biofilm and pit morphology that developed with time were analyzed using atomic force microscopy (AFM). Electrochemical impedance spectroscopy (EIS) results were interpreted with an equivalent circuit to model the physicoelectric characteristics of the electrode/biofilm/solution interface. D. desulfuricans formed one biofilm layer on the metal surface, while the marine isolate formed two layers: a biofilm layer and a ferrous sulfide deposit layer. AFM images corroborated results from the EIS modeling which showed biofilm attachment and subsequent detachment over time.     

Influence of chromium on the local structure and morphology of ferric oxyhydroxides

The extended X-ray absorption fine structure (EXAFS) method and transmission electron microscopy (TEM) have been used for characterizing the local structure and morphology of ferric oxyhydroxides, α-FeOOH and γ-FeOOH, with and without chromium. These ferric oxyhydroxide powders were prepared from aqueous solutions containing iron and chromium ions. Radial structural functions for iron obtained by Fe K edge EXAFS spectra showed that the linkage of structural units formed by FeO₆ octahedra in γ-FeOOH is distorted by chromium addition, while such distortion in α-FeOOH is not clearly detected. On the other hand, Cr K edge EXAFS spectra showed that the local structure around chromium does not necessarily correspond to the local structure around of iron, which is observed by Fe K edge EXAFS spectra. This suggests that the structural units containing iron and chromium are heterogeneously distributed in these ferric oxyhydroxides. The local structural information was discussed coupled with morphological features of these ferric oxyhydroxides observed by TEM.     

时效对接触线用Cu-Ag-Cr合金性能的影响

分析了固溶温度、时效及时效前冷变形量对Cu - 0 1 %Ag - 0 1 %Cr接触线用合金性能的影响 ,结果表明 :经 870℃固溶、 40 %～ 5 0 %冷变形及 480℃× 1 5h时效处理后 ,合金可获得良好的综合性能。     

Temperature Dependence of the Magnetocrystalline Anisotropy in Nd_2Co_(14)B Compound

Easy and hard magnetization curves of Nd_2Co_(14)B compound have been measured withextracting-sample-magnetometer(μ_0H_(max)=6T)at 10～300 K.Magnetic anisotropy constants K_1 and K_2have been determined by fitting the hard magnetization curves,in which only K_1 ,K_2 and misalignment anglehave been taken as fitting parameters.The values of K_1 and K_2 at 4.2 K were derived by extrapolation.Anisotropy coefficients,x_2~° and x_4~°were derived from the anisotropy constants.The anisotropy constant K_2increases rapidly with increasing temperature when TT_(sr).The temperature depen-dence of the magnetic anisotropy coefficient x_2~° was fitted with the formula.The anisotropy coefficients x_2~°can be well described by the tenth-power law from 4.2 K to T_(sr)and by the sixth-power law from T_(sr_ to 300 K.