Claims
- 1. A reaction injection molding process for preparing a sintered, silicon nitride-containing ceramic article comprising:
- (1) injecting into a heated mold a fluid, nondilatant mixture comprising (a) at least 40% by volume of a powder mixture of (i) from about 20 wt. % to about 98 wt. % silicon nitride, (ii) from about 0.5 wt. % to about 20 wt. % of a silicate glass-forming sintering aid, and (iii) from about 0.001 wt. % to about 80 wt. % of a high metal content transition metal silicide or a transition metal or metal compound that forms a high metal content silicide with silicon nitride under the conditions defined in steps (2) or (3), and (b) a curable silicon nitride precursor binder that is a liquid below its curing temperature, to cure the binder and produce a hardened molded article,
- (2) heating the hardened mol suitable atmosphere to a temperature sufficient to convert the cured binder to a silicon nitride-containing ceramic, and
- (3) sintering the article by (i) heating at a temperature of 1300.degree. to 1800.degree. C. until a silicate glass forms, and (ii) further heating at a temperature of 1300.degree. to 1800.degree. C. under a vacuum until oxygen is removed from the silicate glass and the glass crystallizes.
- 2. The process of claim 1 wherein the silicon nitride precursor is a polysilazane.
- 3. The process of claim 1 wherein the silicon nitride precursor is a polyureasilazane.
- 4. The process of claim 1 wherein the silicon nitride precursor is an oligomer.
- 5. The process of claim 1 wherein the silicon nitride precursor contains sites of organounsaturation.
- 6. The process of claim 5 wherein said sites of organounsaturation are vinyl groups bonded to silicon.
- 7. The process of claim 5 wherein the nondilatant mixture further comprises a free radical initiator, and curing is effected by a free radical-initiated chemical polymerization or crosslinking through the sites of organounsaturation.
- 8. The process of claim 1 wherein the metal silicide is present in an amount of 0.001% to 1%.
- 9. The process of claim 1 wherein the metal silicide is present in an amount of 0.001% to about 40%.
- 10. The process of claim 1 wherein the sintering aid is a combination of aluminum oxide and yttrium oxide.
- 11. The process of claim 1 wherein the high metal content silicide is a silicide of Fe, Ru, Os, Co, Rh, Ir, Ni, Pd or Pt.
- 12. The process of claim 11 wherein the high metal content silicide is a silicide of Co, Rh or Ir.
- 13. The process of claim 1 wherein the nondilatant mixture is injected at a temperature of less than about 80.degree. C.
- 14. The process of claim 13 wherein the temperature is less than about 60.degree. C.
- 15. The process of claim 1 wherein the nondilatant mixture further comprises a dispersant.
Parent Case Info
This application is a continuation-in-part of Ser. No. 07/675,010 filed Mar. 26, 1991, now abandoned.
US Referenced Citations (15)
Foreign Referenced Citations (3)
Number |
Date |
Country |
3007384 |
Sep 1980 |
DEX |
63-201058 |
Aug 1988 |
JPX |
WO8807505 |
Oct 1988 |
WOX |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
675010 |
Mar 1991 |
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