Preparation of SiC whiskers
AssigneeGreat Lakes Carbon Corporation
InventorsOttis J. Horne, Jr., Lloyd I. Grindstaff
Life of this patent
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Abstract
Organic fibers are oxidized, ground and blended with a source of silica. Heat treatment of the blend in the range of 1400.degree. to 1700.degree. C. results in the formation of SiC whiskers. Various fibers including PAN, pitch and rayon which can be processed to form carbon and/or graphite fibers can be used as the carbon source. Ashed rice hulls as the source of silica are blended with the chopped fiber to form the SiC whiskers.
Claims16
A process for the manufacture of SiC whiskers comprising the steps of:
- (1) Selecting an organic fiber from the group consisting of polymers, copolymers, and terpolymers of acrylonitrile oxidized in air at a temperature from 200.degree. to 400.degree. C.;
- (2) Grinding or chopping the fiber obtained in step 1 to form a short fiber of approximately 10 to 100.mu. length;
- (3) Mixing the ground fiber obtained above with amorphous SiO.sub.2 ;
- (4) Placing the mixture obtained above in a furnace and increasing the temperature to a carbide-forming temperature within the range of of 1400.degree. to 1800.degree. C. in a non-oxidizing atmosphere;
- (5) When the temperature reaches said carbide-forming temperature, maintaining the mixture at that temperature in an atmosphere of inert gas for a period of 1 to 4 hours;
- and
- (6) Removing the product from the furnace.
A process for the manufacture of SiC whiskers comprising the steps of:
- (1) Carbonizing alpha-cellulose in nitrogen, for about one hour at 400.degree. to 700.degree. C.;
- (2) Mixing about 55 parts by wt. carbonized alphacellulose with about 45 parts by wt. amorphous SiO.sub.2 obtained by ashing rice hulls at a temperature from 400.degree. to 700.degree. C.;
- (3) Placing the mixture in an inert atmosphere of argon;
- and
- (4) Rapidly heating the mixture at about 100.degree. C. rise per minute to a carbide-forming temperature within the range of 1400.degree. to 1800.degree. C., and maintaining the mixture at that temperature under said inert atmosphere of argon for approximately one hour.
A process for the manufacture of SiC whiskers comprised of:
- (1) Ashing rice hulls at a temperature from about 400.degree. to 700.degree. C. to form amorphous SiO.sub.2 ;
- (2) Mixing the ash with ground fibers from 10 to 100.mu. in length selected from the group consisting of polyacrylonitrile fibers oxidized in air at 200.degree. to 400.degree. C., carbonized polyacrylonitrile fibers, graphitized polyacrylonitrile fibers, graphitized viscose rayon, carbonized mesophase petroleum pitch fibers, and fibrous alpha-cellulose carbonized in a nonoxidizing atmosphere;
- (3) Placing the mixture obtained in an inert atmosphere of argon;
- (4) Increasing the temperature at a rate of from 100.degree. C. to 200.degree. C. per minute from ambient to a carbide-forming temperature between 1400.degree. C. and 1800.degree. C., holding the mixture at that temperature in argon for a period of approximately one hour to form SiC whiskers;
- and
- (5) Removing the product from the heating chamber.
Dependencies are inferred from the claim text.