粉煤灰合成堇青石微晶玻璃的性能研究

介绍以粉煤灰为主要原料代替传统的矿物原料，在化学计量比点成功地合成了堇青石微晶玻璃。XRD结果表明，堇青石为微晶玻璃的主晶相，且最优合成条件为1270℃下保温4h。电子探针结果表明，堇青石晶粒细小且弥散于玻璃相中。堇青石微晶玻璃抗热震性能受堇青石相含量、视孔隙率、烧成制度等多方面因素的影响，该陶瓷热震次数最多达到26次。与传统矿物合成的堇青石陶瓷相比，其综合性能仍存在差距。     

Enhancing strength of high-porous cordierite ceramics by mechanochemical activation of the charge

Effects of a preliminary mechanochemical activation of a cordierite charge prepared from of natural raw materials on the strength of high-porosity articles obtained by the method of polymeric-matrix duplication have been studied. It has been shown by the methods of differential thermal analysis, electron-microprobe analysis, and infrared spectroscopy that in an aqueous medium with additives of Trilon B the beginning of the synthesis of cordierite can be fixed already in the course of mechanical activation and that during dry processing using titanium carbide the first to be formed is rutile, which reacts with the kaolinite. It is shown that the introduction of Trilon B upon the activation of the charge in an aqueous medium ensures a steady increase in strength with a satisfactory quality of the cordierite produced and that the addition of titanium carbide intensifies the process of the cordierite synthesis and ensures a considerable growth of the strength of the highly porous permeable cordierite ceramics.     

Electrophysical properties of aion-containing ceramics

A study was mode of the dielectric characteristics of γ-AlON and ceramics containing a certain amount of AlON. It was found that ceramics which contain γ-AlON and have an impurity content below 8 vol. % have more stable dielectric properties. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(408), pp. 8–12, July–August, 1999.     

Electrical properties of Valonia ventricosa

The cytoplasmic electrical potential and membrane resistance of mature cells of Valonia ventricosa have been measured by inserting a microelectrode concentric with another electrode into the vacuole of the cell. The cytoplasmic region was investigated by advancing the microelectrode into the cell wall from the vascuolar side. The results revealed a unique region where the vascuolar electric potential and membrane resistance changed in a simultaneous single step to values close to zero. The measured potential always remained positive immediately after the step. At no time was a highly negative potential region encountered. Further penetration of the microelectrode revealed a low resistance negative potential region of --12.6 +/- 1.1 mV associated with the cell wall. Experiments were also carried out on aplanospores of V. ventricosa to compare mature and immature cells. The chemical composition of the vacuolar and protoplasmic phases of mature cells was determined. The results agreed with previous results except that the C1- ion content of the protoplasm was significantly higher at 381 +/- 20 mmoles/liter (H2O). It was concluded that mature cells of Valonia are significantly different from immature cells in that no highly negative potential cytoplasmic region was found in mature cells. It was considered that the measured step change in electric potential and membrane resistance occurred at the plasmalemma and that the tonoplast was a region of very low resistance. The implications of these findings in terms of models of ion transport into Valonia are discussed.     

堇青石-铁氧体基红外辐射非晶节能涂层的制备与性能

采用等离子喷涂技术在普碳钢表面制备堇青石-铁氧体基红外辐射非晶节能涂层。采用扫描电镜、X射线衍射分析复合红外粉末及其涂层的形貌、物相组成与结构,采用红外光谱仪测定涂层的辐射率,采用划痕法测定涂层与基体的结合力,采用水冷法检测涂层的抗热震性能。研究结果表明:在普碳钢表面制备的堇青石-铁氧体基红外辐射非晶涂层呈层状堆积结构,孔隙率低,与基体的结合力为一级,与传统刷涂工艺制备的涂层相比,等离子喷涂制备的涂层具有更优良的抗热震性能,且制备的红外辐射非晶涂层在3~5μm波段具有较高的红外辐射率,为0.8,在8~10μm波段更是高达0.94。     

Ga掺杂ZnO陶瓷的电子导电性与NTC热敏特性

为开发新型电阻负温度系数(negative temperature coefficient,NTC)热敏陶瓷材料,采用湿化学法制备Ga掺杂ZnO(GZO)陶瓷Zn_(1-x)Ga_xO(x分别为0.005,0.01,0.02,0.03,0.04和0.05)。利用X射线衍射分析材料的相组成,用扫描电镜观察陶瓷的微观结构,通过电阻-温度曲线和交流阻抗谱研究GZO陶瓷的电子导电性和温度敏感特性。结果表明,GZO陶瓷材料具有六方纤锌矿晶体结构;Ga掺杂能明显改善ZnO的电子导电性,GZO陶瓷的电阻率随温度升高呈指数关系降低,呈现优异的NTC特性。Zn_(1-x)Ga_xO陶瓷的NTC材料常数为4 196~5 975 K。其电子导电性和NTC性质由呈现半导体性质的晶粒效应和热激活导电的晶界效应共同贡献。     

钨/氟改性氧化铜陶瓷的导电性质与热敏特性

为了探索开发具有电阻负温度系数(NTC)的新型热敏陶瓷材料,采用湿化学方法合成和制备了W/F掺杂改性的CuO基陶瓷(Cu_1-yW_yO:F_x,x为0.01~0.07,y为0~0.006)。利用X-射线衍射、扫描电子显微镜、电阻-温度测试及电化学交流阻抗等手段对所制备的陶瓷材料的物相组成、微观组织、导电性质及电阻-温度特性进行了测试分析。结果表明,掺杂F能在较大范围内调节CuO陶瓷体的室温电阻率,W/F共掺CuO陶瓷具有优异的NTC特性,适当的W/F掺杂能获得NTC材料常数达5084 K。W/F共掺CuO陶瓷的电子导电性和NTC特性由材料的晶粒（块体）效应和晶界效应共同贡献而成;陶瓷材料的导电模型包含半导体材料的能带理论导电机制和热激活电子跃迁导电模型。      

AlN-W-CNTs复合陶瓷的微波衰减研究

以AlN、CNTs和W粉为原料,采用放电等离子烧结技术,在1 700℃、30 MPa的工艺条件下制备了AlN/W/CNTs复合陶瓷。采用扫描电镜、能谱分析仪、安捷伦LCR自动测试仪等对复合陶瓷的微观组织、介电常数、微波损耗进行了表征,研究了影响复合陶瓷微波损耗性能的因素。结果表明,高能球磨混粉能有效的改善CNTs在基体中的分散均匀性;W含量的增加能有效促进复合陶瓷的烧结致密化;随着CNTs含量的增加,材料的介电损耗降低,介电常数增加;CNTs含量在1%体积分数,1 MHz以下的损耗角正切tanδ≥0.04。     

Electrical properties of cobalt molybdate-base composites

Translated from Poroshkovaya Metallurgiya, No. 6(318), pp. 62–65, June, 1989.     

Electrical and thermal properties of niobium-base cermets

Conclusions Corundum-niobium cermets have temperature of transition into the superconducting state of 6–7°K at metal contents in excess of 20 vol.% and 1–2°K at metal contents of less than 20 vol.%. The volume electrical resistivity of these cermets before the transition into the superconducting state is determined by their metal concentration; it is equal to 1 -m at metal contents of less than 20 vol., and < 10^–2 -m at metal contents of more than 20 vol.%. Studies combining determinations of thermal conductivity and electrical resistivity enable an objective assessment to be obtained of the structure of these materials. The materials investigated were found to have a continuous ceramic phase.Translated from Poroshkovaya Metallurgiya, No. 11(203), pp. 63–65, November, 1979.     

Morphological characteristics of mechanochemically synthesized Fe/Ti composites

The joint mechanical activation of chemically interacting iron and titanium has been studied by X-ray diffraction and atomic force microscopy. It is shown that chemically interacting metals Fe and Ti do not form any intermetallic compounds or solid solutions upon intense mechanical activation in a high-energy planetary mill. The products of mechanical activation are Fe/Ti mechanocomposites, in which titanium is distributed over the iron grain surface. An increase in the mechanical activation time leads to the agglomeration of powders and the formation of particles with a wide size range (5–25 μm). The iron crystallite sizes and the level of microstresses are reduced, indicating a decrease in the particle strength.