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Preparation of high-purity silicon using thermite reactions. Final report, October 1, 1979-November 30, 1980

Technical Report ·
OSTI ID:6430084
;
The preparation of silicon by metallothermic reduction of sodium fluosilicate (Na/sub 2/SiF/sub 6/) and silicon tetrafluoride (SiF/sub 4/) using magnesium and sodium was evaluated. Reduction of Na/sub 2/SiF/sub 6/ with magnesium gave a product containing 35 to 42 wt % magnesium. The impurities from the Na/sub 2/SiF/sub 6/ were found to concentrate in the silicon alloy produced. Reduction with sodium yielded finely divided silicon in a salt matrix. The reduction of SiF/sub 4/ produced by the thermal dissociation of Na/sub 2/SiF/sub 6/ was then investigated. With magnesium as reductant, no thermal booster was required but the product was again a silicon-magnesium alloy. Five kilograms of silicon from the reduction of SiF/sub 4/ and subsequent arc casting were sent to ARCO Solar, Inc. for evaluation as a starting material for solar cell fabrication. A small quantity of silicon comparable in purity to that produced from the silane process was also prepared by the sodium reduction of SiF/sub 4/. A preliminary cost analysis of producing 225 kg of silicon per day by the metallothermic reduction of SiF/sub 4/ with sodium was also prepared.
Research Organization:
Ames Lab., IA (USA)
OSTI ID:
6430084
Report Number(s):
IS-4762; ON: DE81023616
Country of Publication:
United States
Language:
English

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Related Subjects

14 SOLAR ENERGY
140501 -- Solar Energy Conversion-- Photovoltaic Conversion
36 MATERIALS SCIENCE
360101* -- Metals & Alloys-- Preparation & Fabrication
ALKALI METALS
ALKALINE EARTH METALS
ALUMINIUM
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COST
DIRECT ENERGY CONVERTERS
ELEMENTS
EQUIPMENT
FABRICATION
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
IMPURITIES
MAGNESIUM
METALS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
REDUCTION
SEMIMETALS
SILICON
SILICON COMPOUNDS
SILICON FLUORIDES
SILICON SOLAR CELLS
SODIUM
SOLAR CELLS
SOLAR EQUIPMENT
SYNTHESIS