Claims
- 1. A method for preparing single-crystal diamond of high isotopic purity having a thermal conductivity of at least 31.5 watts/cm..degree.K. at 300.degree. K. which comprises the steps of:
- (A) preparing diamond consisting of isotopically pure carbon-12 or carbon-13 by depositing diamond on a substrate by chemical vapor deposition from a low pressure gas mixture consisting of isotopically pure carbon-12 or carbon-13 as a source of hydrocarbon, said deposited diamond being isotopically pure and having thermal conductivity of at least 12; and comminuting said deposited diamond to grit diamond;
- (B) converting said grit diamond to single crystal diamond by diffusion under high pressure through a metallic catalyst-solvent material to a region containing a diamond seed crystal.
- 2. A method according to claim 1 wherein the carbon in the hydrocarbon is carbon-12.
- 3. A method according to claim 1 wherein the carbon in the hydrocarbon is at least 99.2% isotopically pure.
- 4. A method according to claim 3 wherein the diamond of step A is prepared by chemical vapor deposition.
- 5. A method according to claim 4 wherein the equipment employed in step A is constructed of materials substantially incapable of dissolving carbon.
- 6. A method according to claim 4 wherein step A is conducted at a filament temperature of at least 2000.degree. C., a substrate temperature in the range of 900.degree.-1000.degree. C. and a pressure of about 10 torr.
- 7. A method according to claim 6 wherein the filaments are of tungsten and the substrate is molybdenum.
- 8. A method according to claim 5 wherein the carbon in the hydrocarbon is at least 99.9% isotopically pure.
- 9. A method according to claim 8 wherein the catalyst-solvent material employed in step B is an iron-aluminum mixture.
- 10. A method according to claim 9 wherein a negative temperature gradient is maintained in step B between the material being converted and the deposition region.
- 11. A method according to claim 10 wherein the catalyst-solvent material employed in step B is a mixture of 95% iron and 5% aluminum by weight.
- 12. A method according to claim 11 wherein the temperature gradient is about 50.degree. C.
- 13. A method according to claim 10 wherein the pressure in step B is in the range of 50,000-60,000 atmospheres and the temperature is in the range of about 1300.degree.-1500.degree. C.
- 14. A method according to claim 13 wherein the seed crystal is single-crystal diamond of normal isotopic distribution.
- 15. A method according to claim 14 wherein the portion of the product diamond attributable to the seed crystal is removed by polishing.
Parent Case Info
This is a continuation of Ser. No. 07/798,063 filed on Oct. 28, 1991, now abandoned, which is a continuation of Ser. No. 07/536,371 filed on Jun. 11, 1990, now abandoned, which is a continuation-in-part of Ser. No. 07/448,469 filed on Dec. 11, 1989 also abandoned.
US Referenced Citations (7)
Foreign Referenced Citations (5)
Number |
Date |
Country |
206820 |
Jun 1986 |
EPX |
58-110494 |
Jul 1983 |
JPX |
60-112699 |
Jun 1985 |
JPX |
60-118694 |
Jun 1985 |
JPX |
60-121271 |
Jun 1985 |
JPX |
Non-Patent Literature Citations (4)
Entry |
Stromberg et al. "Sintering of Diamond at 1800.degree. C.-1900.degree. C. and 60-65 KBar", American Ceramic Bulletin, vol. 49, No. 12, (1970) pp. 1030-1032. |
Clancy, The Cardinal of the Kremlin, (Barkley Books, Copyright Jul. 1988), pp. 112-113. |
Davies, Diamond (Bristol England: Adam Hilger Ltd.), 1989, p. 138. |
Seitz, "Isotopic Enhancement of Thermal Conductivity and Damage Thresholds in Diamond"Papers given Feb. 6, 1987, at Lincoln Laboratories. |
Continuations (2)
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Number |
Date |
Country |
Parent |
798063 |
Oct 1991 |
|
Parent |
536371 |
Jun 1990 |
|
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
448469 |
Dec 1989 |
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