# US 5,202,105 A · Method for making hexagonal silicon carbide platelets with the addition of a growth additive

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 5,202,105 A
- Document ID: US5202105A
- Status: Granted
- Kind: A
- Application number: 07/548,044
- Filed: 1990-07-05
- Granted: 1993-04-13
- Earliest claimed: 1986-08-22
- Assignees: Stemcor Corporation
- Inventors: Wolfgang D. G. Boecker; Stephen Chwastiak; Tadeusz M. Korzekwa; Sai-Kwing Lau
- Web page: https://patentgrep.com/patent/US5202105A

## CPC

- C30B 25/00: Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- C01B 32/956: Silicon carbide
- C04B 35/117: Composites
- C04B 35/565: based on silicon carbide
- C04B 35/62655: {Drying, e.g. freeze-drying, spray-drying, microwave or supercritical drying}
- C04B 35/645: Pressure sintering
- C04B 35/80: Fibres, filaments, whiskers, platelets, or the like
- C04B 38/0074: {expressed as porosity percentage}
- C22C 1/1021: {the preform being ceramic}
- C22C 1/1036: {starting from a melt}
- C22C 29/065: {based on SiC}
- C30B 29/60: characterised by shape
- B22F 2999/00: Aspects linked to processes or compositions used in powder metallurgy
- C01P 2004/03: obtained by SEM
- C01P 2004/22: with a polygonal circumferential shape
- C01P 2004/54: Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
- C01P 2004/61: Micrometer sized, i.e. from 1-100 micrometer
- C01P 2004/62: Submicrometer sized, i.e. from 0.1-1 micrometer
- C01P 2004/64: Nanometer sized, i.e. from 1-100 nanometer
- C04B 2235/3206: Magnesium oxides or oxide-forming salts thereof
- C04B 2235/3217: Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
- C04B 2235/3821: Boron carbides
- C04B 2235/383: Alpha silicon carbide
- C04B 2235/3834: Beta silicon carbide
- C04B 2235/421: Boron
- C04B 2235/48: Organic compounds becoming part of a ceramic after heat treatment, e.g. carbonising phenol resins
- C04B 2235/5292: Flakes, platelets or plates
- C04B 2235/5296: with a defined aspect ratio, e.g. indicating sphericity
- C04B 2235/5427: millimeter or submillimeter sized, i.e. larger than 0,1 mm
- C04B 2235/5436: micrometer sized, i.e. from 1 to 100 micron
- C04B 2235/5445: submicron sized, i.e. from 0,1 to 1 micron
- C04B 2235/5463: Particle size distributions
- C04B 2235/608: Green bodies or pre-forms with well-defined density
- C04B 2235/6567: Treatment time
- C04B 2235/668: Pressureless sintering
- C04B 2235/77: Density
- C04B 2235/95: Products characterised by their size, e.g. microceramics
- C22C 29/067: {comprising a particular metallic binder}
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

Crystalline silicon carbide wherein at least 90 weight percent of the silicon carbide is formed from a plurality of hexagonal crystal lattices wherein at least 80 weight percent of the crystals formed from the lattices contain at least a portion of opposing parallel base faces separated by a distance of from 0.5 to 20 microns. The crystals may be in the form of separate particles, e.g. separate platelets, or may comprise an intergrown structure. The crystalline silicon carbide of the invention is produced by heating a porous alpha silicon carbide precursor composition comprising silicon and carbon in intimate contact to a temperature of from 2100.degree. C. to 2500.degree. C. in a non-reactive atmosphere. The materials are high performance materials finding use in reinforcing, high temperature thermal insulating, improvement of thermal shock resistance, and modification of electrical properties.

## Claims

### Claim 1

A method of forming separate platelets of alpha silicon carbide comprising heating fine beta silicon carbide powder in an inert gas, nitrogen gas, or vacuum to a temperature of at least about 2150.degree. C. and not greater than 2400.degree. C. in the presence of vapor phase boron, aluminum, or mixtures thereof for at least 15 minutes to effect conversion of substantially all of the beta silicon carbide powder into single crystal platelets of alpha silicon carbide.

### Claim 2 (depends on 1)

The method of claim 1 wherein the beta silicon carbide is heated in an atmosphere having an aluminum or boron vapor pressure sufficient to generate material transfer from the atmosphere into the SiC resulting in a solid solution of at least 300 parts per million boron or aluminum or mixtures thereof in the silicon carbide.

### Claim 3 (depends on 1)

The method according to claim 1 wherein the fine beta silicon carbide powder is blended with a powder containing boron, aluminum, or mixtures thereof in amount sufficient to yield from 0.3 to 3.5 percent of combined boron and aluminum by weight of silicon in the beta silicon carbide.