SILICON-CALCIUM BASED REDUCTION OF RARE EARTH OXIDES

The United State department of energy is encouraging developing processes to (1) expand technology development beyond producing salable rare earth oxides from coal based resources, ultimately producing rare earth metals for use in intermediate and/or final products, commercial and/or defense related equipment; and (2) advance technology beyond the current state-of-the-art which utilizes metallothermic high temperature reduction with very strong reductants such as calcium or lanthanum, or high temperature fused salt electrowinning. An important fundamental limitation of the conventional metallothermic reduction of rare earth oxides to produce rare earth metals is the slow rate of reduction. Adding Silicon powder into a calcio-thermic reaction will improve reduction kinetics, yield, as well as product purity. The main objectives of this Phase I program is to demonstrate the proposed calcium-silicon reductant system that will alleviate limitations of conventional calcio-thermic reduction of rare earth oxides, thus produce rare earth metal in an efficient and economical way. In this program, starting from commercially purchased Nd2O3, Sm2O3 (or Eu2O3), and Ho2O3 (or Er2O3) powders (all constituents of domestic coal), we will develop a new process to produce Nd, Sm (or Eu) and Ho (Er) metals in high purity using a Ca-Si reductant system. The final rare earth metals will be produced either from condensation of their vapors (Sm or Eu) or the segregation of Nd and Ho (or Er) from Si. Our novel approach of rare earth oxides reduction will provide an economical path to produce the desired rare earth metals with high purity with a good yield. It will also enable utilization of two types of industrial wastes, namely coal ashes and silicon kerf loss. We, along with our industrial partners, will commercialization this technology in Phase II and III.