High pressure superabrasive particle synthesis
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 raw material layer, forming a particulate catalyst layer adjacent the raw material layer, and placing crystalline seeds in a predetermined pattern at least partially in the catalyst layer or raw material layer to form a growth precursor. Alternatively, the raw material and catalyst material can be mixed to form a particulate crystal growth layer 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 raw material layer including a raw material;
b) forming a particulate catalyst layer adjacent the raw material layer to form a crystal growth layer, said particulate catalyst layer including a catalyst material; and
c) placing crystalline seeds in a predetermined pattern at least partially in at least one of the catalyst layer and the raw material layer to form a growth precursor.
2 . The method of claim 1 , wherein said catalyst layer consists essentially of 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 step of placing crystalline seeds includes placing the crystalline seeds in the raw material layer and the crystalline seeds are coated with a catalyst coating.
13 . The method of claim 12 , wherein said raw material layer is a particulate source layer.
14 . 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.
15 . The method of claim 1 , wherein the step of placing crystalline seeds include placing the crystalline seeds in the catalyst layer.
16 . The method of claim 1 , wherein the step of placing crystalline seeds substantially surrounds each crystalline seed with catalyst material.
17 . The method of claim 16 , wherein the step of placing crystalline seeds further comprises pressing the crystalline seeds partially into the catalyst layer and then forming a second catalyst layer on the catalyst layer such that each crystalline seed is substantially surrounded by catalyst material.
18 . The method of claim 16 , wherein the step of placing crystalline seeds further comprises pressing the crystalline seeds completely into the catalyst layer such that each crystalline seed is substantially surrounded by catalyst material.
19 . 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.
20 . The method of claim 1 , further comprising the step of heating and pressing the growth precursor to a temperature and pressure sufficient for growth of superabrasive particles to produce grown superabrasive particles.
21 . The method of claim 20 , wherein the temperature is from about 1000° C. to about 1300° C. and the pressure is from about 4 to about 7 GPa.
22 . The method of claim 20 , wherein the temperature is from about 10° C. to about 200° C. above a melting point of the catalyst.
23 . The method of claim 20 , wherein said crystalline seeds have an average diameter from about 0.05 to about 0.2 times an average diameter of the grown superabrasive particles.
24 . The method of claim 1 , wherein said crystalline seeds are from about 30 μm to about 500 μm in diameter.
25 . The method of claim 1 , wherein the predetermined pattern places crystalline seeds a distance of from about 400 μm to about 900 μm apart.
26 . The method of claim 25 , wherein the superabrasive particles have a particle size from about 100 μm to about 2 mm.
27 . The method of claim 26 , wherein the superabrasive particles have a particle size from about 210 μm to about 1 mm.
28 . A growth precursor, comprising at least one crystal growth layer having a raw material layer and a particulate catalyst layer, said catalyst layer having a plurality of crystalline seeds placed in a predetermined pattern.
29 . The precursor of claim 28 , comprising from 3 to 10 crystal growth layers.
30 . The precursor of claim 28 , wherein said raw material is a carbon source.
31 . The precursor of claim 30 , wherein said catalyst material is a member selected from the group consisting of Fe, Ni, Co, Mn, Cr, and alloys thereof.
32 . The precursor of claim 30 , wherein said carbon source comprises graphite having a degree of graphitization of greater than 0.50.
33 . The precursor of claim 28 , wherein said raw material is a hexagonal boron nitride source.
34 . The precursor of claim 33 , wherein said catalyst material is a member selected from the group consisting of alkali, alkali earth metal, and compounds thereof.
35 . The precursor of claim 28 , wherein the crystalline seed is a member selected from the group consisting of diamond seed, cBN seed, SiC seed, and combinations thereof.