Silicon preparation and purity from the reaction of sodium with silicon tetrafluoride and silicon tetrachloride: a thermochemical study
Thermochemical equilibrium computations for the preparation of silicon (Si) by the reaction between sodium (Na), either liquid or vapor, with silicon tetrafluoride (SiF/sub 4/) and silicon tetrachloride (SiCl/sub 4/) are presented. Computations indicate that SiF/sub 4/ reacts with either liquid or gaseous Na to produce temperatures sufficiently high to form molten Si. Liquid Na reacts with SiF/sub 4/ to produce substantially higher Si yields than does the free combustion reaction with Na vapor; however, the Na vapor/SiF/sub 4/ reaction, if temperature-constrained at the Si melting point, produces an expected Si yield close to 100%. A stoichiometric mixture of liquid Na and SiCl/sub 4/ vapor reacts to produce liquid Si, gaseous sodium chloride (NaCl), and a small concentration of Si subhalides. Gaseous Na, however, reacts with SiCl/sub 4/ to form entirely gaseous reaction products and a high yield of Si (liquid) but subhalide concentrations are greater than when liquid Na is used. The reactions of a number of impurity elements in Na, during the course of the Na-Si halide reaction, have been described. Of those considered, only calcium (Ca), magnesium (Mg), phosphorus (P), and strontium (Sr) are expected to co-exist to any extent in Na vapor and none is expected to be in the Si products if excess Si halide is used in the Na-Si halide reactions.
- Research Organization:
- Jet Propulsion Lab., Pasadena, CA (USA)
- OSTI ID:
- 5579314
- Report Number(s):
- DOE/JPL-1012-19
- Country of Publication:
- United States
- Language:
- English
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140501* -- Solar Energy Conversion-- Photovoltaic Conversion
36 MATERIALS SCIENCE
360601 -- Other Materials-- Preparation & Manufacture
ALKALI METALS
CHEMICAL COMPOSITION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
COMPUTER CALCULATIONS
DATA
DATA FORMS
ELEMENTS
EQUILIBRIUM
FLUIDS
FLUORIDES
FLUORINE COMPOUNDS
GASES
GRAPHS
HALIDES
HALOGEN COMPOUNDS
IMPURITIES
INFORMATION
KINETICS
METALS
NUMERICAL DATA
PHYSICAL PROPERTIES
PRODUCTION
PURIFICATION
REACTION KINETICS
SEMIMETALS
SILICON
SILICON CHLORIDES
SILICON COMPOUNDS
SILICON FLUORIDES
SODIUM
THEORETICAL DATA
THERMODYNAMIC PROPERTIES
VAPORS