Microporous mullite aggregates were prepared from bauxite by dry pressing and firing at 1 700 ℃ for 3 h with corn starch,PMMA microspheres or rice husk powder as the porogenic agent.The effects of some porogenic agents and their additions(mass fraction of 0,5％,10％,15％and 20％,respectively)on the properties of the microporous mullite aggregates were analyzed by XRD,SEM and Image-Pro Plus software.The results show that the comprehensive performance of the sample with 10％rice husk powder is the best:the closed porosity is 7.1％;the bulk density is 2.63 g·cm-3;the compressive strength is 122 MPa;the median pore size is 15.16 μm;aandtthe thermal conductivity at 500 ℃ is 2.30 W·m-1·K-1.

以铝矾土矿为原料,以玉米淀粉、聚甲基丙烯酸甲酯微球或稻壳粉为造孔剂,采用干压成型后经1700℃保温3 h制备了微孔莫来石骨料.用XRD、SEM借助Image-Pro Plus软件分析了造孔剂种类和添加量(质量分数分别为0、5％、10％、15％、20％)对微孔莫来石骨料性能的影响.结果表明:添加10％(w)稻壳粉的莫来石骨料的综合性能最佳,其闭气孔率为5.6％,体积密度为2.63 g·cm-3,耐压强度为148 MPa,中值孔径为15.16μm,500℃时的热导率为2.30 W·m-1·K-1.

The effect of CeO2 on sintering and conductivity properties of MgO-CaO materials was investigated. The results show that the densification of MgO-CaO materials is appreciably promoted by adding a small amount of CeO2 owing to the substitution and solution between CeO2 and CaO, which enlarge the vacancy concentration and reduce the diffusion activation energy of Ca2+, thus accelerating the diffusion of Ca2+. During the sintering process, with the grain growth of MgO and CaO as well as the migration of grain boundary, pores between MgO and CaO grains gradually decrease while pores in MgO grains gradually increase and no pores are observed in the CaO grains. The conductivity property of MgO-CaO materials is improved by modification of the microstructure of CaO owing to the enlargement of the carrier concentration by forming Ca2+ vacancies.

Microwave assisted combustion can be regarded as an effective and economic method for preparation of some inorganic functional materials. In this paper, nanocrystalline MgAl2O4 spinel powders were prepared with the mixture of magnesium nitrate, aluminum nitrate and urea as fuel. Morphology structure of the powders and particle size distribution were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), Thermo-Gravimetric/Differential Thermal Analyzer (TG/DTA), respectively. Microwave processing generates a mass of uniform heat in a short time. The gas created during the combustion improves the dispersion of the power and accelerates the formation of the nano crystalline. It is shown that nano crystalline MgAl2O4 spineling powders of narrow particle size distribution and completely crystallized can be prepared when the power is 640 W. Sinter can promote the grain growth of MgAl2O4 spinel. When sintered at 1500 degrees C, the grain has exhibited octahedral structure.