Claims
- 1. A method of sintering alumina based ceramics, comprising the steps of:a. forming a selected alumina ceramic powder into a workpiece; b. applying microwave energy to the formed workpiece in a hydrogen atmosphere at atmospheric pressure until the workpiece is transparent.
- 2. The method of the claim 1, wherein the alumina ceramic is of Al2O3 composition and has a corundum crystal structure.
- 3. The method of claim 1, wherein the alumina ceramic has the Al2O3 or magneto-plumbite crystal structure.
- 4. The method of claim 1, wherein the alumina-ceramic has the composition of MgO.(1-3) Al2O3 and structure of spinel.
- 5. The method of claim 1, wherein the microwave energy is applied at between about 0.915 GHz and about 2.45 GHz, inclusive.
- 6. The method of claim 1, wherein the composition and structure of the transparent workpiece are those of sapphire and further comprising the step of applying microwave energy a second time until the workpiece forms a single crystal.
- 7. The method of claim 6, wherein the second microwave energy is different than the first microwave energy.
- 8. The method of claim 6, wherein the second microwave energy is the same as the first the microwave energy.
- 9. A system for sintering an alumina ceramic workpiece comprising:a. a chamber adapted to retain an alumina ceramic workpiece; b. an insulation layer lining at least a portion of the chamber; c. a temperature measuring instrument adapted to measure the temperature of a workpiece within the chamber; d. a port into the chamber for the supply of hydrogen to the chamber; and e. a source of microwave energy adapted to subject the workpiece to microwave energy in a hydrogen atmosphere at atmospheric pressure until the workpiece is transparent.
- 10. The system of claim 9, further comprising a mount adapted to support the workpiece.
- 11. The system of claim 9, wherein the mount is made of refractory ceramic.
- 12. The system of claim 9, wherein the source of microwave energy provides microwave energy to the workpiece at 0.915 GHz to 2.45 GHz inclusive.
Parent Case Info
This application claims the benefit of U.S. Provisional Application No. 60/222,845 filed Aug. 4, 2000, titled “Sintering of polycrystalline alumina to translucency using microwave sintering, for lighting applications and gems”.
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/US01/24171 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO03/01179 |
2/13/2003 |
WO |
A |
US Referenced Citations (7)
Foreign Referenced Citations (1)
Number |
Date |
Country |
7-187760 |
Jul 1995 |
JP |
Non-Patent Literature Citations (1)
Entry |
Cheng et al., Fabricating Transparent Ceramics by Microwave Sintering; Am. Ceramic Soc. Bull. vol. 79, No. 9, pp. 71-74 (2000). |
Provisional Applications (1)
|
Number |
Date |
Country |
|
60/222845 |
Aug 2000 |
US |