High pressure superabrasive particle synthesis
View Patent ↗An improved method for controlling nucleation sites during superabrasive particle synthesis can provide high quality industrial superabrasive particles with high yield and a narrow size distribution. The synthesis method can include forming a particulate crystal growth layer by mixing a raw material and a catalyst material and then placing the crystalline seeds in a predetermined pattern in the growth layer. Preferably, seeds can be substantially surrounded by catalyst material. The growth precursor can be maintained at a temperature and pressure at which the superabrasive crystal is thermodynamically stable for a time sufficient for a desired degree of growth. The crystalline seeds can be placed in a predetermined pattern using a template, a transfer sheet, vacuum chuck or similar techniques. The superabrasive particles grown using the described methods typically have a high yield of high quality industrial particles and a narrow distribution of particle sizes.
1. A method for controlling nucleation sites during superabrasive particle synthesis, comprising the steps of:
a) forming a particulate crystal growth layer, including a substantially homogeneous mixture of raw material and catalyst material;
b) placing crystalline seeds in a predetermined pattern at least partially in the particulate crystal growth layer to form a growth precursor; and
c) heating and pressing the growth precursor to a temperature and pressure sufficient for growth of superabrasive particles to produce grown superabrasive particles;
wherein the step of placing crystalline seeds includes the steps of:
a) placing a template having a pattern of apertures upon a surface of the crystal growth layer, each of said apertures being configured to receive a single crystalline seed;
b) filling the apertures of said template with the crystalline seeds; and
c) pressing said crystalline seeds at least partially into the crystal growth layer; or
wherein the step of placing crystalline seeds includes the steps of:
d) providing a transfer sheet having an adhesive layer thereon;
e) placing a template having a pattern of apertures upon the adhesive layer, each of said apertures being configured to receive a single crystalline seed;
f) filling the apertures of said template with the crystalline seeds;
g) placing the transfer sheet against a surface of the crystal growth layer; and
h) pressing said crystalline seeds at least partially into the crystal growth layer; or
wherein the step of placing crystalline seeds includes the steps of:
i) providing a vacuum chuck configured with a pattern of apertures;
j) pulling a vacuum through the apertures and engaging a single crystalline seed in each aperture;
k) depositing the crystalline seeds on a surface of the crystal growth layer such that the crystalline seeds are arranged in a predetermined pattern corresponding to the pattern of apertures; and
l) pressing said crystalline seeds at least partially into the crystal growth layer.
2. The method of claim 1 , wherein said particulate crystal growth layer consists essentially of raw material and catalyst material.
3. The method of claim 1 , wherein the superabrasive particle is diamond and the raw material is a carbon source.
4. The method of claim 3 , wherein said catalyst material is a member selected from the group consisting of Fe, Ni, Co, Mn, Cr, and alloys thereof.
5. The method of claim 4 , wherein said catalyst material is an Fe—Ni alloy having about 65 wt % Fe and about 35 wt % Ni.
6. The method of claim 3 , wherein said carbon source is graphite.
7. The method of claim 6 , wherein said graphite has a degree of graphitization of greater than 0.50.
8. The method of claim 7 , wherein said graphite has a degree of graphitization of from about 0.75 to about 1.
9. The method of claim 1 , wherein the superabrasive particle is cubic boron nitride and the raw material is a hexagonal boron nitride source.
10. The method of claim 9 , wherein the catalyst material is a member selected from the group consisting of alkali, alkali earth metal, and compounds thereof.
11. The method of claim 1 , wherein the crystalline seed is a member selected from the group consisting of diamond seed, cBN seed, SiC seed, and combinations thereof.
12. The method of claim 1 , wherein the crystalline seeds are coated with a catalyst coating.
13. The method of claim 12 , wherein said catalyst coating is a catalyst metal selected from the group consisting of iron, nickel, cobalt, and alloys thereof.
14. The method of claim 1 , wherein the step of placing crystalline seeds substantially surrounds each crystalline seed with catalyst material and raw material.
15. The method of claim 1 , further comprising the steps of repeating the steps of forming layers and placing crystalline seeds at least one additional time to form a multi-layered growth precursor.
16. The method of claim 1 , wherein the predetermined pattern places crystalline seeds a distance of from about 400 μm to about 900 μm apart.