Production of SiC whiskers
AssigneeGreat Lakes Carbon Corporation
InventorsOttis J. Horne, Jr., David E. Ramsey, Jr.
Life of this patent
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Abstract
Silicon carbide whiskers useful for reinforcement of metals are manufactured from SiO.sub.2 and carbon. Rice hulls are ashed in air at approximately 620.degree. C. to obtain amorphous SiO.sub.2, which is then blended with fine particle size carbon. The mixture is rapidly heated under CO atmosphere to 1500.degree. C., and when the temperature reaches that point the CO atmosphere is flushed with argon, the SiC whiskers forming in the argon atmosphere. The product is purified by ashing in air to remove excess carbon and/or washed with HF to remove unreacted SiO.sub.2.
Claims11
A process for the manufacture of .beta.-silicon carbide whiskers of about 0.5 to 1.5.mu. in diameter and 10 to 50.mu. length comprising the steps of:
- (1) Ashing rice hulls in air at 400.degree. to 700.degree. C. to obtain amorphous SiO.sub.2 ;
- (2) Mixing finely powdered carbonaceous powder selected from the group consisting of the carbonized residue from heating rice hulls in nitrogen at temperatures between 400.degree. and 700.degree. C. and calcined petroleum coke with the SiO.sub.2 obtained in Step 1;
- (3) Heating the above mixture in CO at 1 atmosphere pressure;
- (4) When the above mixture reaches a carbide-forming temperature within the range of 1400.degree. to 1600.degree. C., flushing the container rapidly with an inert gas;
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- (5) Maintaining a flow of inert gas for a time sufficient to form SiC whiskers.
A process for the production of .beta.-SiC whiskers of 0.5 to 1.5.mu. diameter and 10 to 50.mu. in length comprising the steps of:
- (1) Ashing a portion of rice hulls in air at about 620.degree. C.;
- (2) Mixing the ash thus obtained with a particulate source of carbon selected from the group consisting of rice hulls carbonized in nitrogen for one hour at about 550.degree. C., and 100 mesh ground calcined petroleum coke, in a ratio of approximately 55% ash to 45% carbon source by wt.;
- (3) Placing the mixture thus formed in a furnace;
- (4) Replacing the furnace atmosphere with CO;
- (5) Heating said mixture to about 1500.degree. C. at a rate of temperature increase of at least 100.degree. C. per minute;
- (6) Replacing the CO atmosphere with argon when the temperature of said mixture reaches 1500.degree. C.;
- (7) Maintaining said mixture at 1500.degree. C. in said argon atmosphere for about one hour.
Dependencies are inferred from the claim text.