US4775393A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Autogenous attrition grinding
Assignee: Stemcor Corp
•
Filing: 1986-05-30
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Granted: 1988-10-04
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Expires: 2006-05-30
Abstract
Abstract A method for grinding silicon carbide to a submicron powder which comprises grinding a silicon carbide feed material having an average particle size of between 1 and 200 microns in a liquid slurry in a contamination free high energy autogenous attrition mill in the presence of silicon carbide media for a sufficient time to obtain a specific surface area of at least 5 m 2 /g and preferably at least 9 m 2 /g. The media is of high purity and has an average particle size of less than 4 mm and preferably less than 2.5 mm. The ground material is then further treated so that the average particle size is less than one micron and so that greater than 97 numerical percent of the particles of the finished powder is smaller than 5 microns. The invention includes the finished powder.
Inventors
- 👤 Wolfgang D. G. Boecker
- 👤 Tadeusz M. Korzekwa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 01:12
CPC Classifications
C; C01; C01B; C01B32/00; C01B32/90; C01B32/914; C01B32/956; B; B02; B02C; B02C17/00; B02C17/14; B02C17/16; B02C17/18; B02C17/20; C04; C04B; C04B35/00; C04B35/515; C04B35/56; C04B35/565
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
115 words
A method which comprises (a) grinding a silicon carbide feed material having an average particle size of between 1 and 200 microns in a liquid slurry in a contamination free high energy autogenous attrition mill in the presence of silicon carbide media for a sufficient time to obtain a specific surface area of at least 5 m 2 /g, said media being of high purity and having an average particle size of less than 4 mm, and (b) further treating the resulting ground material so that the average particle size is less than 1 micron and so that greater than 97 numerical percent of the particles of the finished powder is smaller than 5 microns.
Claim 2
Independent Claim
115 words
A method which comprises (a) grinding a silicon carbide feed material having an average particle size of between 1 and 200 microns in a liquid slurry in a contamination free high energy autogenous attrition mill in the presence of silicon carbide media for a sufficient time to obtain a specific surface area of at least 5 m 2 /g, said media being of high purity and having an average particle size of less than 4 mm, and (b) further treating the resulting ground material so that the average particle size is less than 1 micron and so that greater than 97 numerical percent of the particles of the finished powder is smaller than 5 microns.
Claim 3
Dependent Claim
35 words
The method of claim 1 wherein in step (a) at least 90 numerical percent of the powder particles is reduced to a size below one micron and the feed material and media are the same.
Claim 4
Dependent Claim
27 words
The method of claim 1 wherein the treating in step (b) results in greater than 98.5 numerical percent of the powder particles being smaller than 5 microns.
Claim 5
Dependent Claim
27 words
The method of claim 1 wherein the ground material from step (a) is further treated by vibratory grinding to further grind the larger particles of the material.
Claim 6
Dependent Claim
56 words
The method of claim 4 wherein the vibratory grinding occurs for from 2 to 8 hours in a vibrational mill containing silicon carbide cylindrical pellets, said pellets having a maximum dimension of from about 0.5 to 5 centimeters and wherein the diameter of the cylinder is from 0.3 to 4 times the length of the cylinder.
Claim 7
Dependent Claim
25 words
The method of claim 1 wherein the ground material from step (a) is further treated by sedimentation from a liquid to remove larger size particles.
Claim 8
Dependent Claim
20 words
The method of claim 1 wherein the finished powder has an average particle size of from 0.5 to 0.9 microns.
Claim 9
Dependent Claim
32 words
The method of claim 1 wherein the internal surface of the mill and agitator within the mill are coated with an abrasion resistant material selected from polyurethane, natural rubber and synthetic rubber.
Claim 10
Dependent Claim
23 words
The method of claim 1 wherein the liquid is water and the slurry contains from about 30 to about 65 weight percent solids.
Claim 11
Dependent Claim
15 words
The method of claim 1 wherein the grinding occurs for from 2 to 10 hours.
Claim 12
Dependent Claim
20 words
The method of claim 1 wherein heat developed during grinding is removed by circulating the slurry through a heat exchanger.
Claim 13
Dependent Claim
18 words
The method of claim 8 wherein the tip speed of the agitator is above 7.5 meters per second.
Claim 14
Dependent Claim
16 words
The method of claim 1 wherein the feed powder contains less than 800 ppm metal impurities.
Claim 15
Dependent Claim
10 words
The method of claim 1 wherein the liquid comprises water.
Claim 16
Dependent Claim
24 words
The method of claim 14 wherein the liquid comprises HF in a sufficient concentration to result in a pH of from 3 to 4.
Claim 17
Dependent Claim
55 words
A silicon carbide powder having an average particle size smaller than 1 micron, greater than 97 numerical percent of the particle being smaller than 5 microns, a surface area greater than 9 m 2 /g, and a packing density of greater than 1.84 g/cc at 15,000 psi in the presence of 3.4% polyethylene glycol 200.
Claim 18
Dependent Claim
55 words
A silicon carbide powder having an average particle size smaller than 1 micron, greater than 97 numerical percent of the particle being smaller than 5 microns, a surface area greater than 9 m 2 /g, and a packing density of greater than 1.84 g/cc at 15,000 psi in the presence of 3.4% polyethylene glycol 200.
Claim 19
Dependent Claim
22 words
The powder of claim 1 wherein the finished silicon carbide powder is at least as pure as the silicon carbide feed powder.
Claim 20
Dependent Claim
25 words
The finished silicon carbide powder manufactured in accordance with the method of claim 17 wherein the finished powder contains less than 800 ppm metal impurities.
Claim 21
Dependent Claim
25 words
The powder of claim 16 wherein the packing density is greater than 1.86 g/cc at 15,000 psi in the presence of 3.4% polyethylene glycol 200.
Claim 22
Dependent Claim
21 words
The finished powder of claim 18 wherein the powder contains less than 10 ppm boron and less than 100 ppm aluminum.
Claim 23
Dependent Claim
18 words
The powder of claim 16 wherein the powder has a surface area greater than 10 m 2 /g.
Claim 24
Dependent Claim
19 words
The powder of claim 21 wherein the powder has a surface area between 11 and 13 m 2 /g.
Claim 25
Dependent Claim
21 words
The powder of claim 16 wherein the compaction, at 15,000 psi in 3.4% polyethylene glycol 200, is greater than 1.86 g/cc.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-10-04 | 1992-04-04 | 1992-10-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-10-04 | 1996-04-04 | 1996-10-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-10-04 | 2000-04-04 | 2000-10-04 | $7700.00 | Window Closed / Lapsed |