US5221526A — Production of silicon carbide whiskers using a se…

Claim 1

Independent Claim 132 words

A process for making silicon carbide whiskers which comprises heating in a substantially nonoxidizing atmosphere a mixture of (1) a particulate form of carbon, (2) a silicon component selected from the group consisting of silica, hydrated silica and a source of silica, (3) a boron component, and (4) a seeding component comprising (a) an element selected from the group consisting of the rare earths, Group IA, Group IB, Group VB, Group VIB, Group VIIb, and Group VIII of the Periodic Table of Elements, or (b) a compound containing said element at temperatures sufficient to induce a reaction between carbon and silica in said mixture to form silicon carbide whiskers and controlling a size and shape of silicon carbide whiskers produced by the process by selecting a particulate size of the seeding component.

Claim 2

Dependent Claim 132 words

A process for making silicon carbide whiskers which comprises heating in a substantially nonoxidizing atmosphere a mixture of (1) a particulate form of carbon, (2) a silicon component selected from the group consisting of silica, hydrated silica and a source of silica, (3) a boron component, and (4) a seeding component comprising (a) an element selected from the group consisting of the rare earths, Group IA, Group IB, Group VB, Group VIB, Group VIIb, and Group VIII of the Periodic Table of Elements, or (b) a compound containing said element at temperatures sufficient to induce a reaction between carbon and silica in said mixture to form silicon carbide whiskers and controlling a size and shape of silicon carbide whiskers produced by the process by selecting a particulate size of the seeding component.

Claim 3

Dependent Claim 29 words

A process as defined by claim 1 wherein said particulate form of carbon is selected from the group consisting of activated carbon, carbon black, petroleum coke and graphite powder.

Claim 4

Dependent Claim 31 words

A process as defined by claim 1 further comprising the step of controlling the size and shape of the produced silicon carbide whiskers by selecting a concentration of the boron component.

Claim 5

Dependent Claim 25 words

A process as defined in claim 1 wherein said particulate form of carbon has a weight average particle size between about 1 and 1,000 nanometers.

Claim 6

Dependent Claim 25 words

A process as defined by claim 1 wherein said silicon component is silica selected from the group consisting of fumed silica and silica glass powder.

Claim 7

Dependent Claim 16 words

A process as defined by claim 1 wherein said silicon component is a source of silica.

Claim 8

Dependent Claim 28 words

A process as defined by claim 1 wherein said silicon component is a hydrated silica selected from the group consisting of silicic acid, silica sols and silica gels.

Claim 9

Dependent Claim 14 words

A process as defined by claim 3 wherein said silicon component is fumed silica.

Claim 10

Dependent Claim 25 words

A process as defined by claim 1 wherein said boron component is selected from the group consisting of boron oxide, boric acid and organoboron compounds.

Claim 11

Dependent Claim 14 words

A process as defined by claim 8 wherein said boron component is boron oxide.

Claim 12

Dependent Claim 37 words

A process as defined by claim 1 wherein said seeding component comprises an element selected from the group consisting of potassium, rubidium, neodymium, vanadium, chromium, manganese, iron, cobalt, nickel and copper, or a compound containing said element.

Claim 13

Dependent Claim 30 words

A process as defined by claim 10 wherein said seeding component comprises an element selected from the group consisting of cobalt, nickel, and iron, or a compound containing said element.

Claim 14

Dependent Claim 14 words

A process as defined by claim 10 wherein said seeding component is cobalt metal.

Claim 15

Dependent Claim 22 words

A process as defined by claim 1 wherein the mole ratio of boron-to-silicon in said mixture is between about 0.15 and 1.0.

Claim 16

Dependent Claim 41 words

A process as defined by claim 1 wherein a sufficient amount of said seeding component is present in said mixture such that the mole ratio of said element to the silicon in said mixture is between about 0.001 and about 0.20.

Claim 17

Dependent Claim 17 words

A process as defined by claim 15 wherein said mole ratio is between about 0.01 and 0.20.

Claim 18

Dependent Claim 18 words

A process as defined by claim 1 wherein said seeding component is in the form of a metal.

Claim 19

Dependent Claim 47 words

A process as defined by claim 1 wherein said seeding component is a compound in the form of an oxalate, a carbonate, a silicide, a carbide, a sulfide, a nitrate, a nitride, an oxide, a boride, a silicate, a sulfate, a phosphide, a phosphate or a halide.

Claim 20

Dependent Claim 24 words

A process as defined by claim 1 wherein the weight average particle size of said seeding component is between about 0.10 and 200 microns.

Claim 21

Dependent Claim 19 words

A process as defined by claim 1 wherein said mixture is heated at a temperature above about 1300° C.

Claim 22

Dependent Claim 36 words

A process as defined by claim 1 wherein said mixture of said particulate form of carbon, said silicon component, said boron component, and said seeding component is subjected to a vacuum prior to said heating step.

Claim 23

Dependent Claim 117 words

A process for producing silicon carbide whiskers which comprises: (a) forming a mixture of carbon black, silica, boron oxide, and a seeding component comprising an element selected from the group consisting of cobalt, nickel, and iron, or a compound of said element; (b) heating said mixture in a substantially nonoxidizing atmosphere at temperatures sufficiently above about 1300° C. to induce the reaction of carbon with silica to form silicon carbide whiskers; (c) controlling a size and shape of silicon carbide whiskers produced by the process by selecting seeding component having a weight average particle size between about 0.10 and about 3.0 microns; and (d) recovering a product containing silicon carbide whiskers having the controlled size and shape.

Claim 24

Dependent Claim 117 words

A process for producing silicon carbide whiskers which comprises: (a) forming a mixture of carbon black, silica, boron oxide, and a seeding component comprising an element selected from the group consisting of cobalt, nickel, and iron, or a compound of said element; (b) heating said mixture in a substantially nonoxidizing atmosphere at temperatures sufficiently above about 1300° C. to induce the reaction of carbon with silica to form silicon carbide whiskers; (c) controlling a size and shape of silicon carbide whiskers produced by the process by selecting seeding component having a weight average particle size between about 0.10 and about 3.0 microns; and (d) recovering a product containing silicon carbide whiskers having the controlled size and shape.

Claim 25

Dependent Claim 45 words

A process as defined by claim 22 further comprising the step of controlling the size and shape of the produced silicon by adjusting a concentration of boron in said mixture, a mole ratio of boron-to-silicon in said mixture being between about 0.20 and about 0.90.

Claim 26

Dependent Claim 40 words

A process as defined by claim 23 wherein a sufficient amount of said seeding component is present in said mixture such that the mole ratio of said element to the silicon in said mixture is between about 0.01 and 0.15.

Claim 27

Dependent Claim 13 words

A process as defined by claim 24 wherein said silica is fumed silica.

Claim 28

Dependent Claim 14 words

A process as defined by claim 25 wherein said seeding component is cobalt metal.

Claim 29

Dependent Claim 24 words

A process as defined by claim 26 wherein the weight average particle size of said carbon black is between about 5 and 100 nanometers.

Claim 30

Dependent Claim 24 words

A process as defined by claim 27 wherein the weight average particle size of said cobalt metal is between about 0.5 and 2.0 microns.

Claim 31

Dependent Claim 22 words

A process as defined by claim 28 wherein the mole ratio of carbon-to-silicon in said mixture is between about 2.5 and 5.0.

Claim 32

Dependent Claim 22 words

A process as defined by claim 29 wherein said mixture is heated at a temperature between about 1500° C. and 1800° C.

Claim 33

Dependent Claim 25 words

A process as defined by claim 30 wherein greater than about 50 weight percent of the whiskers in said recovered product have a curly shape.

Claim 34

Dependent Claim 116 words

A process for producing silicon carbide which comprises: (a) forming a mixture of carbon black, silica, boron oxide, and a seeding component comprising an element selected from the group consisting of cobalt, nickel, and iron, or a compound containing said element; (b) heating said mixture in a substantially nonoxidizing atmosphere at temperatures sufficiently above about 1300° C. to induce the reaction of carbon with silica to form silicon carbide whiskers; (c) controlling a size and shape of silicon carbide whiskers produced by the process by selecting seeding component having a weight average particle size between about 3.0 and about 200 microns; and (d) recovering a product containing silicon carbide whiskers having the controlled size and shape.

Claim 35

Dependent Claim 116 words

A process for producing silicon carbide which comprises: (a) forming a mixture of carbon black, silica, boron oxide, and a seeding component comprising an element selected from the group consisting of cobalt, nickel, and iron, or a compound containing said element; (b) heating said mixture in a substantially nonoxidizing atmosphere at temperatures sufficiently above about 1300° C. to induce the reaction of carbon with silica to form silicon carbide whiskers; (c) controlling a size and shape of silicon carbide whiskers produced by the process by selecting seeding component having a weight average particle size between about 3.0 and about 200 microns; and (d) recovering a product containing silicon carbide whiskers having the controlled size and shape.

Claim 36

Dependent Claim 45 words

A process as defined by claim 32 further comprising the step of controlling the size and shape of the produced silicon by adjusting a concentration of boron in said mixture, a mole ratio of boron-to-silicon in said mixture being between about 0.35 and about 1.0.

Claim 37

Dependent Claim 39 words

A process as defined by claim 33 wherein a sufficient amount of said seeding component is present in said mixture such that the mole ratio of said element to silicon in said mixture is between about 0.01 and 0.15.

Claim 38

Dependent Claim 24 words

A process as defined by claim 34 wherein the weight average particle size of said seeding component is between about 5.0 and 100 microns.

Claim 39

Dependent Claim 13 words

A process as defined by claim 35 wherein said silica is fumed silica.

Claim 40

Dependent Claim 14 words

A process as defined by claim 36 wherein said seeding component is cobalt metal.

Claim 41

Dependent Claim 21 words

A process as defined by claim 37 wherein the carbon-to-silicon mole ratio in said mixture is between about 2.5 and 5.0.

Claim 42

Dependent Claim 24 words

A process as defined by claim 38 wherein the weight average particle size of said carbon black is between about 5 and 100 nanometers

Claim 43

Dependent Claim 26 words

A process as defined by claim 39 wherein greater than about 80 weight percent of the whiskers in said recovered product have a relatively straight shape.

Claim 44

Dependent Claim 15 words

A process as defined by claim 6 wherein said source of silica is a silane.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1996-06-21	1996-12-21	1997-06-22	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2000-06-21	2000-12-21	2001-06-22	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2004-06-21	2004-12-21	2005-06-22	$7700.00	Window Closed / Lapsed

Production of silicon carbide whiskers using a seeding component to determine shape and size of whiskers

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag