Calcium thermic production of rare metal and intermetallic powders

Abstract

This paper analyzes the thermodynamic and kinetic environment for calcium thermic production of rare metal and intermetallic powders and the status of this method among other thermal reduction methods. The discussion of thermodynamic processes focuses on gas phase equilibrium. A close consideration is given not only to binary metal-calcium systems but also to three- and multi-component systems. The role of such auxiliary substances as calcium hydride and calcium chloride is discussed. It is shown that, when the final product includes intermetallides of rare metals, calcium can even be used for the reduction of oxides of metals that are more sensitive to oxygen than calcium. There are cases when the presence of calcium chloride during reduction leads to a lower equilibrium content of oxygen in the reduced rare metal than during calcium reduction. The paper describes thermal reduction flow charts and the process equipment. This review is meant for Russian researchers and experts engaged in research and development of the calcium thermic techniques for powder metal and alloy production.