Study on the calciothermic reduction of titanium and rare eath metals and the recycle of calcium.

用饱和的钙蒸气直接还原二氧化钛可以得到低氧含量的钛，因为它可以在一定程度上消除氧与固溶体中金属的亲和力。在任何从钛的氧化物中精炼钛的讨论中，都必须了解氧在钛固溶体中的热力学稳定性。然而，钛中的氧具有很高的稳定性，普通的气体平衡法或使用固体电解质的电动势方法不适用于活度测量。因此，在本研究中，钛金属在1173-1573K的闭式钢弹中，在饱和的钙蒸气和氧化钙的共存下平衡，淬火并分析氧气。在1173K和1573K时，平衡气体浓度分别为300和900质量ppm。得到了β-Ti相场中氧势、温度和成分之间的关系：1/2ln(&lt；p_(0_2)&gt；/101325Pa.)=ln(%O)+12.1-71900 T1173-1573K，(%O)&lt；0.15质量%尝试在1273K用饱和钙蒸气还原&lt；(S)+Ca(G)=Ti(S)+CaO(S)。还原产物的电子显微镜显示，还原的钛颗粒被固相反应产物CaO完全包围。还原阶段还原速率变得很低，此时氧化物的分解几乎停止，而Ti-O固溶体开始还原。

Titanium with low oxygen content has been expected to be obtainable by direct reduction of titanium dioxide with saturated calcium vapor, because it can remove the oxygen to the extent to which it is able to overcome the affinity of the oxygen for the metal in the solid solution range.A knowledge of the thermodynamic stability of oxygen in the Ti-O solid solution is indispensable in any discussion of the refining of titanium from its oxide. Oxygen in titanium has, however, high stability that ordinary gas equilibration or EMF method using solid electrolyte is not applicable to activity measurement. In this investigation, titanium metal was, therefore, equilibrated under coexistance of saturated calcium vapor and calcium oxide in closed bombs of steel at temperatures between 1173 and 1573 K, quenched and analysed for oxygen. The equilibrium gas concentrations were 300 and 900 mass ppm at 1173 and 1573 K, respectively. The data were then used to derive the relationship among oxygen potential, temperature and composition in the beta -Ti phase field:1/2 ln( <p_(0_2)> /101325Pa)=ln(%O) + 12.1-71900 T 1173-1573 K, (%O)<0.15 mass%Attempts were made to produce titanium by reducing <TiO_2> powders with saturated calcium vapors at 1273 K according to<TiO_2> (s) + Ca(g) = Ti(s) + CaO(s).Electron micrographs of the reduction products showed that the reduced titanium particles were completly surrounded with the solid reaction product, CaO. The reduction rate become very low at the reduction stage at which the decomposition of oxide almost ceased and the deoxidation of the Ti-O solid solution began to take place.