Diamond grains, method for making same and mixture comprising same

Patent metadata

Field	Value
Publication number	US-10047455-B2
Application number	US-201314646256-A
Country	US
Kind code	B2
Filing date	Dec 10, 2013
Priority date	Dec 12, 2012
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

A method of providing well-shaped diamond grains of at most about 100 microns in size. The method includes providing a synthesis assembly comprising a source of carbon material, a plurality of seed grains on which diamond material can crystallize, and solvent-catalyst material for promoting the crystallization of the diamond grains, and subjecting the synthesis assembly to a condition for growing the diamond grains. The synthesis condition is maintained long enough for at least about half of the carbon material to be converted into the diamond grains.

First claim

The invention claimed is:

1. A method of providing a plurality of euhedral diamond grains having a mean size of greater than 5 microns and at most 100 microns, the method including:
providing a synthesis assembly comprising:
a source of carbon material,
a plurality of seed grains on which diamond material can crystallise, and solvent-catalyst material for promoting the crystallisation of the diamond grains;

subjecting the synthesis assembly to a synthesis condition by means of an ultra-high pressure furnace, at which synthesis condition the pressure and temperature are such that the solvent-catalyst material is molten, diamond material can crystallise on the seed grains, and spontaneous nucleation of diamond grains does not occur;
the synthesis assembly being arranged such that carbon comprised in the source can migrate through the solvent-catalyst material and crystallise as diamond material on the seed grains at the synthesis condition;
the synthesis condition being maintained for a synthesis period sufficient for at least 50 percent of the carbon material comprised in the source to be converted into the plurality of diamond grains;
the number of seed grains and the amount of carbon material comprised in the source being selected such that the synthesis condition can be maintained by the ultra-high pressure furnace for the synthesis period;
reducing the pressure and temperature, and
recovering the plurality of diamond grains from the synthesis assembly,
and further comprising subjecting the synthesis assembly to a load and heat cycle comprising three stages, the first stage including applying load onto the synthesis assembly such that the pressure therein is increased at ambient temperature to a first pressure in the range of 1 gigapascal to 5 gigpascals; the second stage including applying heat to the synthesis assembly such that the solvent-catalyst material melts; and the third stage including increasing the load such that the pressure in the synthesis assembly is increased to at least 5.5 gigapascals and achieving the synthesis condition.

2. A method as claimed in claim 1 , in which the amount of carbon material comprised in the source, the number of seed grains and the synthesis period are selected such that all the carbon material comprised in the source is exhausted by the end of the synthesis period.

3. A method as claimed in claim 1 , in which the mean size range of the diamond grains is at least 10 microns and at most 50 microns and in which the seed grains comprise diamond material and have a mean size of at least 0.5 micron and at most 5 microns.

4. A method as claimed in claim 1 , in which the solvent-catalyst material comprises metal material and the ratio of the mass of the solvent-catalyst material to the mass of the carbon source comprised in the synthesis assembly is at least about 3 and at most about 10.

5. A method as claimed in claim 1 , including providing a capsule assembly comprising a buffer assembly and the synthesis assembly, the buffer assembly being free of seed grains; in which the buffer assembly and the synthesis assembly are configured and constituted such that the ultra-high pressure furnace is capable of maintaining the synthesis condition for the synthesis period.

6. A method as claimed in claim 5 , in which the capsule assembly comprises a barrier structure for preventing substantial transfer of material between the synthesis assembly and the buffer assembly at the synthesis condition.

7. A method as claimed in claim 5 , in which the solvent-catalyst material comprises metal material and the buffer assembly comprises the carbon material; the ratio of the mass of the solvent-catalyst material to the combined mass of the carbon material in the capsule assembly being at least 1 and at most 3.

8. A method as claimed in claim 1 , in which the pressure, in the third stage, is at least 5.5 gigapascals and at most 5.9 gigapascals.

9. A method as claimed in claim 1 , in which the solvent-catalyst material comprises iron and nickel.

10. A method as claimed in claim 1 , in which the synthesis assembly comprises a compact synthesis body, which comprises the carbon material for the source, the seed grains and the solvent-catalyst material.

11. A method as claimed in claim 1 , including processing the plurality of diamond grains to select a plurality of selected diamond grains.

12. A method as claimed in claim 11 , including depositing material onto the surfaces of the selected diamond grains to provide microstructures attached to the selected diamond grains.

13. A method as claimed in claim 12 , in which the material is capable of reacting with carbon to form carbide compound material.

14. A method as claimed in claim 12 , in which the microstructure comprises titanium carbide.

15. A method as claimed in claim 11 , including combining a plurality of the selected diamond grains with bond material for a tool or with precursor material for bond material for a tool, to provide a mixture.

Assignees

• Element Six Abrasives Sa
• Element Six Ltd

Inventors

• Nzama Mhlonishwa Cyprian
• Thomson Dale Anthony
• Munday Mark Gregory

Classifications

• B01J2203/062

  Diamond · CPC title

• B01J2203/0655

  Diamond · CPC title

• C30B29/04 Primary

  Diamond · CPC title

• B24D18/0009

  using moulds or presses · CPC title

• C01P2004/61

  Micrometer sized, i.e. from 1-100 micrometer · CPC title