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1. (US5851943) Ceramic production process
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique
We claim:
1. A process for the production of O'--SiAlON from silicon metal, nitrogen, and clay, the process comprising heating a component mixture comprising the silicon metal and the clay in a flowing nitrogen atmosphere to a temperature sufficient to react the components to form O'--SiAlON and wherein the clay participates in the reaction as a source of aluminum and silicon.
2. The process according to claim 1 wherein the clay is the sole source of aluminium.
3. The process according to claim 1 comprising dehydroxylating the clay and mixing the dehydroxylated clay with the silicon metal and heating the component mixture under a flowing nitrogen atmosphere to a temperature sufficient to react the mixture to form O'--SiAlON.
4. The process according to claim 1 further comprising the addition of silica.
5. The process according to claim 1 wherein the clay is a hydrated layer aluminosilicate mineral.
6. The process according to claim 1 wherein the clay is a kaolin, montmorillonite, pyrophyllite, bentonite or halloysite clay.
7. The process according to claim 1 wherein the clay is dehydroxylated by precalcining and the dehydroxylated clay is mixed with the silicon metal and heated in the flowing nitrogen atmosphere.
8. The process according to claim 1 wherein the clay is dehydroxylated by heating the clay to a temperature between about 500° C. and about 800° C. and the dehydroxylated clay is mixed with the silicon metal and heated in the flowing nitrogen atmosphere.
9. The process according to claim 1 wherein the component mixture is present as fine powders.
10. The process according to claim 1 wherein the clay is present in an amount of between about 5% and about 60% by weight.
11. The process according to claim 1 wherein the clay is present in an amount of between about 20% and about 60% by weight.
12. The process according to claim 1, the component mixture including by weight, about 20% to about 50% clay, 0% to about 25% silica and about 40% to about 60% silicon metal.
13. The process according to claim 1, the component mixture including about 30% to about 40% clay, about 10% to about 20% silica, and about 40% to about 55% silicon metal.
14. The process according to claim 1 wherein the flowing nitrogen atmosphere comprises ≤0.5% oxygen and ≤0.5% water vapor.
15. The process according to claim 1 wherein the flowing nitrogen atmosphere comprises ≤10 ppm O 2 and ≤25 ppm water vapor.
16. The process according to claim 1 wherein the mixture is heated to between about 1100° C. and about 1900° C.
17. The process according to claim 1 wherein the mixture is heated at a rate between about 0.2° C. and about 10° C. per minute.
18. The process according to claim 17 wherein the heating rate is between about 2° C. and about 5° C. per minute.
19. The process according to claim 1 wherein the component mixture is held at the temperature for between about 4 and about 60 hours.
20. The process according to claim 1 wherein additive compounds are included to enhance the reaction and/or to promote sintering.
21. The process according to claim 20 wherein additive compounds selected from Y 2 O 3, Fe 3 O 4, ZrO 2, ZrSiO 4, MgO and β-SiAlON are included to enhance the reaction and/or to promote sintering.
22. The process according to claim 1 further comprising the addition of a ceramic material to produce a composite ceramic including O'--SiAlON.
23. The process according to claim 1 wherein ceramic material selected from silicon carbide (SiC), alumina (Al 2 O 3), silicon nitride (Si 3 N 4), SiAlON, zirconia (ZrO 2), zircon (ZrSiO 4) and silica (SiO 2) is added to produce a composite ceramic including O'--SiAlON.
24. The process according to claim 1 wherein a ceramic material coarser than the other mixture components which react to form the O'--SiAlON is added to produce a composite ceramic including O'--SiAlON.
25. The process according to claim 1 wherein up to about 75% by weight of the mixture of a ceramic material is added to produce a composite ceramic including O'--SiAlON.
26. The process according to claim 1 wherein additional ceramic material is present in an amount of between about 40% and about 70% by weight of the mixture.
27. A process for the production of O'--SiAlON from a component mixture comprising, by weight, 40%-60% silicon metal, 20%-45% clay, and 10%-25% silica, the process comprising the steps of:
(a) dehydroxylating the clay prior to inclusion in the component mixture;
(b) heating the component mixture at a rate of 1° C. to 6° C. per minute, to a temperature of between about 1300° C. to 1900° C. under a flowing nitrogen atmosphere having ≤0.5% oxygen and ≤0.5% water vapor;
(c) holding the temperature between 1300° C. and 1900° C. for up to 12 hours; and
(d) recovering O'--SiAlON.
28. A process for the production of a composite ceramic material including O'--SiAlON from a mixture of components comprising a ceramic material, and an O'--SiAlON forming combination of silicon metal, clay and nitrogen wherein the process comprises heating the ceramic material, silicon metal and clay in a flowing nitrogen atmosphere to a temperature sufficient to form the O'--SiAlON composite ceramic and wherein the clay is a source of aluminum and silicon.
29. The process according to claim 28 wherein the O'--SiAlON forming combination further comprises silica.
30. The process according to claim 28 wherein the clay is the sole source of aluminium for the production of O'--SiAlON.
31. The process according to claim 29 wherein the ceramic material is selected from silicon carbide (SiC), alumina (Al 2 O 3), silicon nitride (Si 3 N 4), SiAlON, zirconia (ZrO 2), zircon (ZrSiO 4) and silica (SiO 2).
32. A process for the production of a composite ceramic including O'--SiAlON from a mixture of components comprising, by weight, up to 75% of a ceramic material and 2.5% or more of an O'--SiAlON forming mixture, wherein the O'--SiAlON forming mixture comprises, by weight, 40%-60% silicon metal, 20%-45% clay, and 10%-25% silica, the process comprising the steps of:
(a) heating the component mixture at a rate of between about 1° C. to 6° C. per minute, to a temperature of between substantially 1300° C. to 1900° C. under a flowing N 2 atmosphere having ≤0.5% oxygen and ≤0.5% water vapor;
(b) holding the temperature between 1300° C. and 1900° C. for up to 12 hours; and
(c) recovering the composite ceramic.