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81.
钼还原过程相变化研究 总被引:5,自引:0,他引:5
采用钼酸铵直接氢还原及钼酸铵先焙解然后再分段氢还原两种不同的还原方法进行了钼粉还原。通过X射线衍射方法分析了两种工艺还原过程中的反应序列及相变化规律,并讨论了不稳定相Mo4O11对于钼粉还原过程的影响。 相似文献
82.
碳热还原法制备氮化硅粉体的反应过程分析 总被引:15,自引:0,他引:15
对以碳热还原法制备氮化硅粉体的SiO2-C-N2系统进行化学反应热力学和动力学的分析,从而发现在氮气氛不足的条件下,这一系统的反应产物将由氮化硅变为碳化硅;在氮气充足的情况下,随着温度的升高,生成物中碳化硅的量也会逐步增加,这一分析结果通过实验得到了验证。 相似文献
83.
采用粉末冶金技术制备出车辆发动机涡轮增压器用自润滑止推板,研究了材料的基体强化、组织结构和摩擦磨损特性,分析了装机台架综合考核数据,并且与国际上同类产品进行比较,结果表明:该材料综合性能优于国际上同类产品,现已投入工业化生产和批量使用。 相似文献
84.
粉末布法制备SiC/Ti基复合材料 总被引:2,自引:0,他引:2
用粉末布法制备了低成本SiC/Ti基复合材料.结果表明,采用合适的轧制参数即可容易地获得厚度合适、均匀的粉末布;热失重分析和热解残余物分析指出用来制备粉末布的有机粘结剂的去除过程分成两个阶段,合理除气后,基本没有残余物.使用真空热压工艺制备的SiC/Ti基复合材料,纤维分布基本均匀,纤维与基体的界面结合良好. 相似文献
85.
86.
Angela Altomare Carmelo Giacovazzo Anna Grazia Giuseppina Moliterni Rosanna Rizzi 《Journal of research of the National Institute of Standards and Technology》2004,109(1):125-132
The ab-initio crystal structure solution by powder diffraction data requires great efforts because of the collapse of the experimental information onto the one dimensional 2θ axis of the pattern. Different strategies will be described aiming at improving the process of extraction of the integrated intensities from the experimental pattern in order to make more straightforward the structure solution process by direct methods. Particular attention will be devoted to the EXPO program. Some of its performance will be analysed and results will be shown. 相似文献
87.
Unconrolled agglomeration of particles and adhesion of the particulate mass to wall surfaces are common severe problems in many drying operations. This paper reviews the mechanisms of interparticle and particle-surface attraction as well as the theory and the existing tests for characterising powders in terms of internal strength, wall friction and adhesion. The usefulness of the information obtained from these tests in dryer design and operation is critically reviewed. The importance of powder stickiness in various types of dryers is discussed and established methods of combating the problem are presented Recommendations an made for further research in the area of powder cohesion and adhesion. 相似文献
88.
巴利新(原苏联)是世界知名的粉末冶金学家。1938年他提出的压制方程ln p=—AV+B仍为美国1984年出版的《金属手册》第九版第七卷‘粉末冶金’所引用。早在70年代,巴利新就根据他提出的一系列新理论,提出一个新的压制或固结方程式组α=~2z,f=F(,α),p=pαf,但除原苏联外,该方程鲜为人知。鉴于此,本文作者对巴利新60年代以来发表的一系列关于粉末冶金理论的论著进行了整理,现扼要地予以阐述,这对我国粉末冶金理论的研究或许是有益的。 相似文献
89.
The effect of reducing the reactor air pressure on the morphology of spray dried magnesium sulphate powders is investigated, experimentally. A reactor, capable of drying and pyrolyzing solution sprays at low pressures, is designed and manufactured. A vibrating mesh nebulizer is employed to generate the spray. Four different pressures, starting from 60 Torr to the atmospheric pressure, and two different reactor air temperatures of 130°C and 420°C, are considered. In addition, two different concentrations of magnesium sulphate solutions are tested. The results are explained based on the effect of reactor air pressure on the droplet evaporation rate. 相似文献
90.
Dental amalgams are based on a broad spectrum of materials differing in their chemical composition, metallurgical treatment, and in the way the initial alloys powders are prepared. In addition to their chemical composition, amalgams based on various powders differ in both their microstructure and the amount of mercury needed for preparation. All these facts may affect electrochemical processes occurring during their interaction with oral fluids, and also mercury release. While verifying the effect of the technology used for the preparation of the high‐copper ternary alloy powder on the properties of resulting amalgams, this study aimed at the mechanism of their interaction with a model saliva solution as well as mercury release was included. Measurements were done in a model saliva solution using standard electrochemical methods and exposition measurements. The interaction of individual types of amalgams with artificial saliva did not reveal any significant differences. The free corrosion potential of all these amalgams in an aerated solution settled in the range of values in which tin oxidation, resulting in a layer of insoluble corrosion producsts, turned out to be the dominant anodic process. The rate of mercury release was the lowest for amalgams based on a gas‐atomized alloy. The highest rate of mercury release, and also its dependence on time, was exhibited by lathe‐cut powder based amalgam. In addition to different volume fraction of the Ag‐Hg phase and the level of its tin alloying, this different behaviour may be explained by differences in the rate at which a layer of tin corrosion products acting as a barrier to mercury release is formed. 相似文献