Abstract A method wherein a quartz tube is charged with chunks of metallurgical grade silicon and/or a mixture of such chunks and high purity quartz sand, and impurities from a class including aluminum, boron, and the like, as well as certain transition metals including nickel, iron, manganese and the like. The tube is then evacuated and heated to a temperature within a range of 800° C. to 1400° C., whereupon a stream of gas comprising a reactant, such as silicon tetrafluoride, continuously is delivered at low pressures through the charge for causing a metathetical reaction of impurities of the silicon and the reactant to occur for forming a volatile halide and leaving a residue of silicon of an improved purity. Additionally, the reactant may include carbon monoxide gas, whereby impurites such as iron and nickel react therewith to form volatile carbonyls.
Inventors
👤 with respect to an invention by Frosch Robert A. Administrator of the National Aeronautics and Space Administration
👤 William M. Ingle
👤 Stephen W. Thompson
👤 Robert E. Chaney
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-11-01 07:33
CPC Classifications
C; C01; C01B; C01B33/00; C01B33/02; C01B33/037
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
133 words
In a method of purifying metallurgical grade silicon, the steps comprising: A. charging a quartz tube with chunks of metallurgical grade silicon containing impurities consisting essentially of aluminum and boron; B. heating the silicon to a temperature within a range of 800° C. to 1350° C. in vacuo; C. continuously passing through said chunks a stream of reactant gas at 0.1 torr to one atmosphere consisting essentially of silicon tetrafluoride to effect a metathetical reaction of aluminum and boron impurities of the silicon with the silicon tetrafluoride with AlF 3 and BF 3 being formed and leaving a residue of silicon of improved impurity; and wherein the AlF 3 formed reacts with the surface of the quartz tube to form silicon tetrafluoride and aluminum oxide which deposits as a coating on said surface.
Claim 2
Dependent Claim
133 words
In a method of purifying metallurgical grade silicon, the steps comprising: A. charging a quartz tube with chunks of metallurgical grade silicon containing impurities consisting essentially of aluminum and boron; B. heating the silicon to a temperature within a range of 800° C. to 1350° C. in vacuo; C. continuously passing through said chunks a stream of reactant gas at 0.1 torr to one atmosphere consisting essentially of silicon tetrafluoride to effect a metathetical reaction of aluminum and boron impurities of the silicon with the silicon tetrafluoride with AlF 3 and BF 3 being formed and leaving a residue of silicon of improved impurity; and wherein the AlF 3 formed reacts with the surface of the quartz tube to form silicon tetrafluoride and aluminum oxide which deposits as a coating on said surface.
Claim 3
Dependent Claim
35 words
The method of claim 1 wherein the chunks are of a size within a range of 0.1-10 mm, and the reactant gas is passed through said chunks for a period of four to twenty hours.
Claim 4
Dependent Claim
24 words
The method of claim 2 wherein the quartz tube is characterized by an inside diameter of 1-4 inches and a length of 24-36 inches.
Claim 5
Dependent Claim
34 words
The method of claim 2 wherein the impurities further contain nickel and the reactant gas further contains carbon monoxide and wherein the carbon monoxide reacts with the nickel to form volatile Ni(CO) 4 .