Optimization and scale-up studies of the SiF4-Na reaction have continued. The dependence of the reaction initiation time and of the efficiency of the reaction on Na particle size and reactor temperature has been studied. Close to 100% utilization of Na has been obtained, and formation of by-product fluosilicate has been decreased to below 10 per cent. A SiF4-Na reactor has been built to scale up the reaction by a factor of about 4 and is now being tested. A scaled-up melting system has been built and successfully used to separate Si from kilogram quantities of Si-NaF mixtures. Support studies of the volatili¬zation of NaF performed in a smaller melting system indicated minimal loss of NaF as vapor at 1410 C. The wetting of graphite was also investigated to de¬termine the constituents of the NaF phase which promote good wetting.
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