Methods of fabricating polycrystalline diamond by carbon pumping and polycrystalline diamond products

1. A method of fabricating polycrystalline diamond, comprising:

(i) providing a plurality of diamond crystals and a metal-solvent catalyst;

(ii) subjecting the plurality of diamond crystals and the metal-solvent catalyst to a first pressure-temperature condition during which carbon is dissolved in the metal-solvent catalyst and the metal-solvent catalyst is at least partially liquefied;

(iii) after act (ii), subjecting the plurality of diamond crystals and the metal-solvent catalyst to a second pressure-temperature condition at which diamond is stable, wherein carbon has a lower solubility in the metal-solvent catalyst at the second pressure-temperature condition than at the first pressure-temperature condition; and

(iv) after act (iii), subjecting the plurality of diamond crystals and the metal-solvent catalyst to a third pressure-temperature condition during which carbon is dissolved in the metal-solvent catalyst.

2. The method of claim 1 , further comprising:

after act (iv), subjecting the plurality of diamond crystals and the metal-solvent catalyst to a fourth pressure-temperature condition at which diamond is stable, wherein carbon has a lower solubility in the metal-solvent catalyst at the fourth pressure-temperature condition than at the first and third pressure-temperature conditions.

3. The method of claim 1 wherein a first temperature of the first pressure-temperature condition and a third temperature of the third pressure-temperature condition are each greater than a second temperature of the second pressure-temperature condition.

4. The method of claim 1 wherein the first pressure-temperature condition is the substantially the same or different than the third pressure-temperature condition.

5. The method of claim 1 wherein a second pressure of the second pressure-temperature condition is greater than a first pressure of the first pressure-temperature condition and a third pressure of the third pressure-temperature condition.

6. The method of claim 1 wherein at least one of the first or the third pressure-temperature conditions is a graphite-stable pressure-temperature condition.

7. The method of claim 1 wherein at least one of the first or the third pressure-temperature conditions is a diamond-stable pressure-temperature condition.

8. The method of claim 1 , further comprising:

changing from the first pressure-temperature condition to the second pressure-temperature condition by decreasing the temperature while maintaining the pressure substantially constant; and

changing from the second pressure-temperature condition to the third pressure-temperature condition by increasing the temperature while maintaining the pressure substantially constant.

9. The method of claim 1 wherein providing a plurality of diamond crystals and a metal-solvent catalyst comprises mixing a non-diamond carbon source with the plurality of diamond crystals.

10. The method of claim 9 wherein the non-diamond carbon source is selected from the group consisting of graphite particles, fullerenes, metastable shells of ultra-dispersed diamond particles, and combinations thereof.

11. The method of claim 9 , further comprising:

wherein subjecting the plurality of diamond crystals and the metal-solvent catalyst to a first pressure-temperature condition during which carbon is dissolved in the metal-solvent catalyst comprises subjecting the plurality of diamond crystals, the metal-solvent catalyst, and the non-diamond carbon source to the first pressure-temperature condition during which a portion of at least the non-diamond carbon source is dissolved in the metal-solvent catalyst;

wherein subjecting the plurality of diamond crystals and the metal-solvent catalyst to a second pressure-temperature condition at which diamond is stable comprises subjecting the plurality of diamond crystals, the metal-solvent catalyst, and un-dissolved non-diamond carbon source to the second pressure-temperature condition;

wherein subjecting the plurality of diamond crystals and the metal-solvent catalyst to a third pressure-temperature condition during which carbon is dissolved in the metal-solvent catalyst comprises subjecting the metal-solvent catalyst, the plurality of diamond crystals, and the un-dissolved non-diamond carbon source to the third pressure-temperature condition during which at least a portion of the un-dissolved non-diamond carbon source is dissolved in the metal-solvent catalyst; and

after act (iv), subjecting the plurality of diamond crystals and the metal-solvent catalyst to a fourth pressure-temperature condition at which diamond is stable.

12. The method of claim 1 wherein the polycrystalline diamond exhibits increased diamond-to-diamond bond density compared to if the plurality of diamond crystals were sintered in the presence of the metal-solvent catalyst only at the second pressure-temperature condition.

13. The method of claim 1 wherein the metal-solvent catalyst is in the form of metal-solvent catalyst particles mixed with the plurality of diamond crystals.

14. The method of claim 1 wherein providing a plurality of diamond crystals and a metal-solvent catalyst comprises positioning the plurality of diamond crystals adjacent to a layer including the metal-solvent catalyst.

15. The method of claim 1 wherein providing a plurality of diamond crystals and a metal-solvent catalyst comprises positioning the plurality of diamond crystals adjacent to a substrate that includes the metal-solvent catalyst therein.

16. The method of claim 15 wherein subjecting the plurality of diamond crystals and the metal-solvent catalyst to a first pressure-temperature condition during which carbon is dissolved in the metal-solvent catalyst comprises infiltrating the plurality of diamond crystals with the metal-solvent catalyst from the substrate.

17. The method of claim 1 wherein the metal-solvent catalyst is selected from the group consisting of iron, nickel, cobalt, and alloys thereof.