Claims
- 1. A process for producing aluminum nitride powder made up of unagglomerated particles of less than about 2 microns in size having a size distribution suitable for sintering, which process comprises mixing by a dry mixing procedure and then reacting particles of gamma alumina, or a precursor thereof, of less than 1 micron in size with a stoichiometrical excess of a finely divided impure form of carbon containing iron in the presence of nitrogen, or a precursor which provides nitrogen in the reaction conditions, first at a temperature in the range of 1550.degree. to 1700.degree. C. for a period of between 1 and 6 hours and then at a temperature in the range of 1750.degree. to 1850.degree. C. for a period of 1 to 4 hours, followed by cooling said reaction mixture, and reheating to a temperature in the range of 500.degree. to 700.degree. C. in an oxygen-containing atmosphere, and maintaining the temperature until excess unreacted carbon is removed.
- 2. A process according to claim 1 wherein said carbon contains the following impurities in the following amounts:
- ______________________________________Impurity % by weight______________________________________Sulphur 2 to 6Iron 0.16 to 0.40Silicon 0.1 to 0.40Total Ash <0.1 to 1.______________________________________
- 3. A process according to claim 1 wherein said carbon is petroleum coke.
- 4. A process according to claim 1 wherein said carbon is in the form of particles having a size less than about 45 microns in diameter.
- 5. A process according to claim 1 wherein said carbon is in the form of particles having a size of less than about 1 micron in diameter.
- 6. A process according to claim 1 wherein said precursor of gamma alumina is selected from the group consisting of flash activated aluminum hydrate and hydrolysis products of aluminum organic compounds.
- 7. A process according to claim 1 wherein said alumina or precursor thereof is in the form of particles having a size of 10 to 400 nanometers.
- 8. A process according to claim 1 wherein said alumina or precursor thereof is in the form of particles having a size of 10 to 100 nanometers.
- 9. A process according to claim 1 wherein said alumina or precursor thereof is in the form of particles having a size of 10 to 30 nanometers.
- 10. A process according to claim 1 wherein said particles of alumina or precursor and said particles of carbon are mixed to substantial homogeneity prior to reacting said particles.
- 11. A process according to claim 1 wherein the weight ratio of alumina:carbon is 100:36-42.
- 12. A process according to claim 1 wherein the reaction is carried out at the first temperature for a period of 1 to 4 hours.
- 13. A process according to claim 1 wherein the reaction is carried out at said second temperature for a period of 1 to 2 hours.
- 14. A process according to claim 1 carried out in the absence of materials other than said alumina or precursor, said carbon and said nitrogen or precursor.
- 15. A process according to claim 1 wherein said reheating is carried out for a period of 1 to 2 hours.
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of applicants' copending application Ser. No. 725,348 filed Jul. 3, 1991, abandoned.
US Referenced Citations (6)
Foreign Referenced Citations (6)
Number |
Date |
Country |
0308116 |
Mar 1989 |
EPX |
0353052 |
Jul 1989 |
EPX |
0371771 |
Jun 1990 |
EPX |
2-96709 |
Dec 1990 |
JPX |
WO9118845 |
Dec 1991 |
WOX |
WO9119027 |
Dec 1991 |
WOX |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
725348 |
Jul 1991 |
|