# US 5,702,997 A · Process for making crack-free silicon carbide diffusion components

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- Number: US 5,702,997 A
- Document ID: US5702997A
- Status: Granted
- Kind: A
- Application number: 08/725,717
- Filed: 1996-10-04
- Granted: 1997-12-30
- Earliest claimed: 1996-10-04
- Assignees: Saint-Gobain/Norton Industrial Ceramics Corporation
- Inventors: Stephen Dynan; Jack Shindle; John Vayda
- Web page: https://patentgrep.com/patent/US5702997A

## CPC

- C04B 35/565: based on silicon carbide
- C04B 35/573: obtained by reaction sintering {or recrystallisation}
- C04B 35/6263: {characterised by their solids loadings, i.e. the percentage of solids}
- C04B 35/63424: {Polyacrylates; Polymethacrylates}
- C04B 2235/3418: Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint
- C04B 2235/3826: Silicon carbides
- C04B 2235/422: Carbon
- C04B 2235/425: Graphite
- C04B 2235/5409: expressed by specific surface values
- 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 2235/5472: Bimodal, multi-modal or multi-fraction
- C04B 2235/6027: Slip casting
- C04B 2235/608: Green bodies or pre-forms with well-defined density
- C04B 2235/61: Mechanical properties, e.g. fracture toughness, hardness, Young's modulus or strength
- C04B 2235/656: characterised by specific heating conditions during heat treatment
- C04B 2235/6562: Heating rate
- C04B 2235/6581: Total pressure below 1 atmosphere, e.g. vacuum
- C04B 2235/77: Density
- C04B 2235/96: Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- 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

## Abstract

This invention relates to a method for producing a crack-free sintered silicon carbide body, comprising the steps of: a) providing a raw powder batch comprising: i) at least 40 w/o fine grain fraction having a particle size of less than 10 microns, the fine grain fraction comprising silicon carbide, ii) at least 40 w/o coarse grain fraction having a particle size of at least 30 microns, the coarse grain fraction comprising silicon carbide and less than 0.10 w/o free carbon, the raw batch having a total silica content of at least 0.5 w/o, the raw batch having a total silicon carbide content of at least 96 w/o, b) forming the raw batch into a green body, and c) recrystallizing the green body to provide a recrystallized silicon carbide body having a density of between 2.0 g/cc and 2.8 g/cc.

## Claims

### Claim 1

A method for producing a crack-flee sintered silicon carbide body, comprising the steps of:
a) providing a raw powder batch comprising:
i) at least 40 w/o fine grain fraction having a particle size of less than 10 microns, the fine grain fraction comprising silicon carbide,
ii) at least 40 w/o coarse grain fraction having a particle size of at least 30 microns, the coarse grain fraction comprising silicon carbide and less than 0.10 w/o free carbon,
the raw batch having a total silica content of at least 0.5 w/o,
the raw batch having a total silicon carbide content of at least 96 w/o,
b) forming the raw batch into a green body, and
c) recrystallizing the green body to provide a recrystallized silicon carbide body having a density of between 2.0 g/cc and 2.8 g/cc.

### Claim 2 (depends on 1)

The method of claim 1 wherein the coarse grain fraction comprises no more than 0.06 w/o free carbon.

### Claim 3 (depends on 1)

The method of claim 1 wherein the coarse grain fraction comprises no more than 0.02 w/o free carbon.

### Claim 4 (depends on 1)

The method of claim 1 wherein the coarse grain fraction comprises no more than 0.01 w/o free carbon.

### Claim 5 (depends on 1)

The method of claim 1 wherein the raw batch comprises between 45 w/o and 55 w/o fine fraction.

### Claim 6 (depends on 5)

The method of claim 5 wherein at least 80 w/o of the fine grain fraction has a particle size of between 0.4 and 8 um.

### Claim 7 (depends on 6)

The method of claim 6 wherein the average particle size of the fine grain fraction is between 1 and 4 um.

### Claim 8 (depends on 1)

The method of claim 1 wherein the raw batch comprises between 45 w/o and 55 w/o coarse fraction.

### Claim 9 (depends on 8)

The method of claim 8 wherein at least 80 w/o of the coarse grain fraction has a particle size of between 65 and 150 um.

### Claim 10 (depends on 1)

The method of claim 1 wherein at least 96 w/o of the fine grain fraction is silicon carbide.

### Claim 11 (depends on 10)

The method of claim 10 wherein between about 1.0 w/o and 3 w/o of the fine grain fraction is silica.

### Claim 12 (depends on 11)

The method of claim 11 wherein between 1.5 w/o and 2.5 w/o of the fine grain fraction is silica.

### Claim 13 (depends on 1)

The method of claim 1 wherein at least 96 w/o of the coarse grain fraction is silicon carbide.

### Claim 14 (depends on 13)

The method of claim 13 wherein between about 0.01 w/o and 0.3 w/o of the coarse grain fraction is silica.

### Claim 15

A raw batch comprising:
i) at least 40 w/o fine grain fraction having a particle size of less than 10 microns, the fine grain fraction comprising silicon carbide,
ii) at least 40 w/o coarse grain fraction having a particle size of at least 30 microns, the coarse grain fraction comprising silicon carbide and less than 0.10 w/o free carbon,
the raw batch having a total silica content of at least 0.5 w/o,
the raw batch having a total silicon carbide content of at least 96 w/o.

### Claim 16 (depends on 15)

The raw batch of claim 15 wherein the coarse grain fraction comprises less than 0.06 w/o free carbon.

### Claim 17 (depends on 15)

The raw batch of claim 15 wherein the coarse fraction comprises no more than 0.02 w/o free carbon.

### Claim 18 (depends on 15)

The raw batch of claim 15 wherein the coarse fraction comprises no more than 0.01 w/o free carbon.

### Claim 19 (depends on 15)

The raw batch of claim 15 wherein the raw batch comprises between 45 w/o and 55 w/o fine fraction.

### Claim 20 (depends on 19)

The raw batch of claim 19 wherein at least 80 w/o of the fine fraction has a particle size of between 0.4 and 8 um.

### Claim 21 (depends on 20)

The raw batch of claim 20 wherein the average particle size of the fine fraction is between 1 and 4 um.

### Claim 22 (depends on 15)

The raw batch of claim 15 wherein the raw batch comprises between 45 w/o and 55 w/o coarse fraction.

### Claim 23 (depends on 22)

The raw batch of claim 22 wherein at least 80 w/o of the coarse fraction has a particle size of between 65 and 150 um.

### Claim 24 (depends on 15)

The raw batch of claim 15 wherein at least 96 w/o of the fine fraction is silicon carbide.

### Claim 25 (depends on 24)

The raw batch of claim 24 wherein between about 1.0 w/o and 3 w/o of the fine fraction is silica.

### Claim 26 (depends on 25)

The raw batch of claim 25 wherein between 1.5 w/o and 2.5 w/o of the fine fraction is silica.

### Claim 27 (depends on 15)

The raw batch of claim 15 wherein at least 96 w/o of the coarse fraction is silicon carbide.

### Claim 28 (depends on 27)

The raw batch of claim 27 wherein between about 0.01 w/o and 0.3 w/o of the coarse fraction is silica.