低温等离子体化学法制备纳米级TiO2超细粉末

采用改进的低温等离子体化学法,用无水TiCl_4在氧气氛中,制备了小于10nm非晶TiO_2超细粉末,通过XRD、TEM、TG-DTA和XPS等手段分析了反应条件对产物形态、粒径大小和组成的影响,研究了热处理条件与TiO_2晶化、晶型转变之间的关系,高于200℃时非晶TiO_2转化成具有锐钛矿结构的晶态。此外,还初步讨论了TiO_2超细粉末形成过程的动力学和电子辐照效应。     

基于Intranet的火电厂水汽化学过程监控系统

介绍了一种基于Intranet技术的火电厂水汽化学过程监控系统的组成原理、功能特点和控制策略，系统成本低、维护方便、操作简单、适应性强、可靠性高，具有很好的通用性，对于火电厂水汽化学过程的监控有较高的推广价值。     

化学反应产物振动态分布的计算程序

使用半经典微扰和无限级突然近似方法计算产物振动态分布的程序，程序用ＦＯＲＴＲＡＮ语言编写，只要输入一个化学反应产物的振动态量子数，就可得到产物中此态的分配比例。     

Physical and tribological properties of diamond films grown in argoncarbon plasmas

Nanocrystalline diamond films have been deposited using a microwave plasma consisting of argon, 2–10% hydrogen and a carbon precursor such as C₆₀ or CH₄. It was found that it is possible to grow the diamond phase with both carbon precursors, although the hydrogen concentration in the plasma was 1–2 orders of magnitude lower than normally required in the absence of the argon. Auger electron spectroscopy, X-ray diffraction measurements and transmission electron microscopy indicate the films are predominantly composed of diamond. Surface roughness, as determined by atomic force microscopy and scanning electron microscopy indicate the nanocrystalline films grown in low hydrogen content plasmas are exceptionally smooth (30–50 nm rms) to thicknesses of 10 m. The smooth nanocrystalline films result in low friction coefficients (μ = 0.04–0.06) and low average wear rates as determined by ball-on-disk measurements.     

硼砂碳解反应过程的模拟和监控

本文探讨了硼砂碳解化学反应的机理,提出了在线计算碳解率和对反应时间进行优化计算的方法,并开发了相应的微机监控系统.该监控系统在现场进行了调试运行,它能实现3个回路控制及反应时间优化等功能.     

Distribution of chemical constituents in the plant parts of six tropical-origin forage grasses at early anthesis

The distribution of chemical constituents in the plant parts of six tropical forage grasses at early anthesis was studied. The forage grasses were guinea grass Panicum maximum (Jacq.); angleton grass Dichanthium aristatum (Poir.); gamba grass Andropogon gayanus (Kunth); buffel grass Cenchrus ciliaris (L.); birdwood grass Cenchrus setigerus (Vahl.); and rhodes grass Chloris gayana (Kunth.). Apart from ether extract, which generally decreased from the inflorescence down to the basal culm, and crude fibre, which increased from the inflorescence down to the basal culm, no clear gradient of constituents within the plants could be established for any of the forage grass species.     

Yttrium aluminum garnet powders by nitrate decomposition and nitrate–urea solution combustion reactions—a comparative study

Precursors for yttrium aluminum garnet (Y₃Al₅O₁₂—YAG) were synthesized by simple decomposition of concentrated aqueous solution of nitrates and combustion of concentrated aqueous solution of nitrates with urea on a heater. The precursor formed by the former reaction was granules of agglomerated powder while that from the latter reaction was a voluminous and porous sponge-like mass. Both precursors were ground to powders and subjected to detailed thermogravimetric–differential thermal analysis and X-ray diffraction studies. The precursor from the simple decomposition of nitrates exhibited a total loss in weight of about 18% in stages (25 to 300 °C and 300 to 600 °C) accompanied by endotherms—characterized as processes of dehydration of absorbed moisture and decomposition of residual nitrates, respectively. The as formed precursor and that heated to 820 °C were amorphous. Crystallization to YAG phase occurred from an amorphous oxide characterized by an exotherm above 820 °C with no loss of weight. The precursor from nitrate–urea combustion reaction was found to exhibit a weight loss of 2.5% accompanied by a shallow endotherm in the range of 25 to 300 °C—characterized as the process of dehydration of absorbed moisture. No further weight loss or heat effect was noticed, confirming it to be chemically pure YAG. This as formed precursor was found to be crystalline YAG. The difference in chemical composition of the precursors formed by these two reactions is attributed to the difference in the actual reaction temperatures during their formation—lower reaction temperature for the endothermic decomposition of nitrates and higher reaction temperature for the exothermic combustion associated with the formation of a bright flame. The morphology of the precursor powder formed by the former reaction exhibited only cracks while that of the precursor from the latter reaction exhibited pores and voids. The precursor from the former reaction was calcined at 1100 °C to form into chemically pure YAG. Zeta potential variation with pH for the aqueous suspensions of the crystalline YAG powders from both the reactions exhibited a maximum value in the range of 40 to 50 mV around a pH of 4, indicating stability of these dispersions towards coagulation at this pH. Particle size distribution of wet ground powders (slurries with 20%, v/v, solid at a pH of 4) showed that the powder from combustion reaction could be formed into a finer size than that from simple nitrate decomposition, indicating the agglomerates of combustion reaction were softer.     

Porothermoelasticity for swelling shales

Optimization of drilling fluid parameters such as mud weight, salt concentration, and temperature is essential to alleviating instability problems when drilling through shale sections, particularly in high-pressure and high-temperature environments. Under these conditions, selection of suitable mud parameters can benefit from analyses that consider significant thermal and chemo–mechanical processes involved in shale–drilling fluid interactions. A non-isothermal poroelastic theory suitable for shales is presented herein. Phenomena related to thermal and chemical osmosis are considered by extending the theory of porothermoelasticity to chemically active rocks. The modified pore pressure and stresses around a borehole in shale are obtained by solving the porothermoelastic field equations in generalized plane strain. Application of the solution to a typical field operational situation has demonstrated that thermal osmosis can significantly impact formation pore pressure, thereby reducing stability. Furthermore, analyses based on the new porothermoelastic formulation for shales suggest that mud temperature should be optimized in order to maximize the efficacy of chemical osmosis in stabilizing the borehole.     

Chemical sensing by an electrical oscillator: Detection and quantification of cationic surfactants

A new chemical sensing system using an electrical oscillator has been developed. This sensing system measures the electrical ‘non-linearity’ at the surface of an electrode immersed in a test solution: a sinusoidal voltage is applied to the electrode and the higher harmonics of the output current are obtained by Fourier transformation. This sensing system has been used to detect and quantify surfactant molecules in solutions. The relative intensity P₂/P₁ of the peaks of the second (P₂) and first (P₁) harmonics in the output current was found to be linearly correlated with the logarithms of the concentrations of cationic surfactants such as cetylpyridium bromide (CPB) and cetyl-N,N,N-trimethylammonium bromide (CTAB), but not with those of the anionic surfactant sodium dodecyl sulfate (SDS) or the neutral surfactant Triton X-100. The reproducibility of this sensing system was shown to be excellent.     

Chemical Conversion Film of Mischmetal on Zinc Deposit

ＣｈｅｍｉｃａｌＣｏｎｖｅｒｓｉｏｎＦｉｌｍｏｆＭｉｓｃｈｍｅｔａｌｏｎＺｉｎｃＤｅｐｏｓｉｔＷａｎｇＪｉｋｕｉ（王济奎）（ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＣｈｅｍｉｓｔｒｙ，ＮａｎｊｉｎｇＵｎｉｖｅｒｓｉｔｙｏｆＣｈｅｍｉｃａｌＴｅｃｈｎｏｌ...