Electronic structures and optical properties for Ag-N-codoped ZnO nanotubes

The structural and electronic/optical properties of pure and Ag-N-codoped (8,0) ZnO nanotubes have been studied using first-principles calculations in the framework of the local spin density approximation. The configurations for Zn atoms replaced by Ag atoms are p-type semiconductor materials, and the bandgap increases when N atoms are doped into ZnO nanotube configurations. The optical studies based on dielectric function and reflectivity indicate that new transition peaks in the visible light range are observed, which can be ascribed to the Ag and N doping. Furthermore, there is a red shift observed with the increase of N concentration.     

Vitrification of a waste water flocculate from a petroleum catalyst manufacturer

Chemical and mineral compositions of a waste water flocculate generated in a manufacturer producing fluidized-bed catalytic cracking catalysts were analyzed. The flocculate was then calcined at 1200–1350 °C. X-ray diffraction analysis results indicate that the flocculate can be directly vitrified at 1350 °C without the addition of any other ingredients. The density and chemical durability of the directly vitrified product are comparable with commercial soda-lime-silicate glasses. However, the viscosity of directly vitrified glass melt was very high. Thus, the refining and shaping of the glass melt were difficult. With the addition of minerals such as limestone, dolomite and fluorite, workable glasses could be formed. The influence of MgO on the structure and properties of the obtained glasses is discussed. Results show that the density and hardness of the glass increase with the increase of MgO, whereas the chemical durability, transition and crystallization temperatures decrease. The present study provides a general way to utilize waste water flocculates in glass production.     

Influence of sintering temperature on dielectric properties and crystal structure of corundum-structured Mg4Ta2O9 ceramics at microwave frequencies

Microwave dielectric properties of corundum-structured Mg₄Ta₂O₉ ceramics were investigated as a function of sintering temperatures by an aqueous sol–gel process. Crystal structure and microstructure were examined by X-ray diffraction (XRD) technique and field emission scanning electron microscopy (FE-SEM). Sintering characteristics and microwave dielectric properties of Mg₄Ta₂O₉ ceramics were studied as a function of sintering temperature from 1250 °C to 1450 °C. With increasing sintering temperature, the density, ε_r and Qf values increased, saturating at 1300 °C with excellent microwave properties of ε_r=11.9, Qf=195,000 GHz and τ_f=?47 ppm/°C. Evaluation of dielectric properties of Mg₄Ta₂O₉ ceramics were also analyzed by means of first principle calculation method and ionic polarizability theory.     

Iridium-catalyzed aerobic oxidation of alkylarenes with excellent turnover numbers

A highly efficient catalyst system has been developed for the aerobic oxidation of alkylarenes under solvent free conditions. The combination of iridium complex, nitrogen ligand and iodobenzene was found to be crucial for catalytic activity. Excellent turnover numbers were achieved for the preparation of benzoic acids and aryl ketones. This finding may provide useful clues for improving commercially important oxidation processes.     

小班制讲授《物理化学》课的几点体会

目前,我国高校普遍存在课堂教学的班级规模偏大,影响到教学质量的提高。小班制教学,是高校本科教学改革的重要内容之一,是实施素质教育的具体方法。文章结合近几年的教学实践,从提问、讲课和自学讨论三个方面介绍在小班制《物理化学》课程教学一些体会。     

Heating mechanism of spark plasma sintering

According to the plasma sintering process and our theoretical calculation, we analyzed the heating mechanism of spark plasma sintering (SPS). It is proposed that the sintering temperature of conductive materials rises faster mainly due to the contribution of the direct current (DC) component in pulse current, current skin effect and eddy current in the mould and blank, Joule's heat generated by eddy current in grains, small heat capacity of the heated system and direct-contact heating. For non-conductive materials, the similar reasons can be found except for the heat effect of eddy current. By analyzing the heating mechanism of SPS, it is concluded that the temperature on the surface of a conductive green body should be higher than that on the inner surface of the die, whereas the opposite case holds for a non-conductive blank, that has already been verified by Nagae et al. [Journal of the Japan Society of Powder and Powder Metallurgy 44 (1997) 945–950] and by Sumi et al. [Journal of the Japan Society of Powder and Powder Metallurgy 45 (1998) 153–157].     

改性硅酸盐水泥浆体的耐水性

研究了磷铝酸盐水泥（phosphoaluminate cement,PALc）改性的硅酸盐水泥（portland cement,PC）浆体的耐水性及其耐水机理。以胶砂力学强度、净浆耐水性指数、Ca^2＋及[AlO4]^5-的溶出浓度3项指标评价了浆体的耐水性。结果表明：质量分数为3％～5％PALC改性的PC样品经水浸蚀1,90d后的耐水性指数较PC的分别提高了66．7％和60．8％。改性PC样品水浸蚀1,90d的抗压强度较PC的分别提高了90．1％和64．5％。改性PC样品浸水1,90d Ca^2＋溶出浓度分别为PC的67．9％和66．4％,[AlO4]^5-溶出浓度分别为PC的49．10％和50．2％。与PC样品比较,PALC改性PC样品的耐水性提高主要是由于形成了更为稳定的水化产物。而且水化产物凝胶相增多,Ca（OH）2量减低;浆体溶液的ζ电位低以及小于30nm孔的体积增大。     

硫酸根离子对CaO-Al2O3-P2O5-SiO2体系耐水性的影响

研究了硫酸根离子对CaO-Al2O3-P2O5-SiO2体系耐水性的影响,通过XRD、SEM及孔结构分析手段对其耐水性机理进行分析。结果表明:在CaO-Al2O3-P2O5-SiO2体系中掺入适量的硫酸根离子,不会改变其主要水化产物的组成。浸水180d后,掺石膏的试件211S的耐水性指数较未掺石膏的试件211提高10.2%,劈裂强度提高6.7%,Ca2 、[AlO4]5-离子溶出浓度分别下降11.59%、7.2%,211S具有优异的孔结构。掺入硫酸根离子可以明显的提高该体系的后期强度和耐水性。     

Effect of MgO on the composition and properties of alite-sulphoaluminate cement

The effect of MgO on the composition and properties of alite-sulphoaluminate cement clinker with commercial-grade raw materials such as limestone, clay, gypsum and fly ash as starting materials has been investigated in order to confirm results previously obtained with pure raw materials. The experiment results confirm that the addition of MgO at about 2-5% can improve the burnability of raw meal, promote the absorption of free lime and the formation of C₃S and C₄A₃S¯. In addition, it is shown that this can also increase the strength development of the cement and shorten the setting time. When the content of MgO reaches about 8%, the strength of the cement decreases slightly and the setting time is extended.     

有机化合物及聚合物的计算机辅助红外光谱法鉴定

建立了计算机辅助红外光谱法鉴定有机化合物及聚合物的新方法,介绍了计算有机化合物和聚合物的一些经验公式。程序设计首先收集、整理常用聚合物、有机添加剂和有机小分子的红外光谱数据,然后提取反映该物质特征的吸收峰数据,制作ACCESS数据库,利用VisualBasicDAO数据链接方式,根据查询要求动态链接数据库,利用要求查询的聚合物特性,经过经验公式的算法翻译,生成SQL查询语句进行查询。