US4356136A
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Method of densifying an article formed of reaction bonded silicon nitride
Assignee: Ceradyne Inc
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Filing: 1980-08-29
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Granted: 1982-10-26
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Expires: 2000-08-29
Abstract
Abstract A method of densifying an article formed of reaction bonded silicon nitride is disclosed. The reaction bonded silicon nitride article is packed in a packing mixture consisting of silicon nitride powder and a densification aid. The reaction bonded silicon nitride article and packing powder are sujected to a positive, low pressure nitrogen gas treatment while being heated to a treatment temperature and for a treatment time to cause any open porosity originally found in the reaction bonded silicon nitride article to be substantially closed. Thereafter, the reaction bonded silicon nitride article and packing powder are subjected to a positive high pressure nitrogen gas treatment while being heated to a treatment temperature and for a treatment time to cause a sintering of the reaction bonded silicon nitride article whereby the strength of the reaction bonded silicon nitride article is increased.
Inventors
- 👤 John A. Mangels
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 10:13
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593; C04B35/5935
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
185 words
A method of densifying an article formed of reaction bonded silicon nitride, which method comprises the steps of: packing the reaction bonded silicon nitride article in a packing mixture consisting of silicon nitride powder and a densification aid; subjecting the reaction bonded silicon nitride article and packing powder to a positive, low pressure nitrogen gas treatment at a pressure up to about 100 psi nitrogen pressure, while heating the reaction bonded silicon nitride article, packing powder and nitrogen gas to a treatment temperature and for a treatment time to cause any open porosity originally found in the reaction bonded silicon nitride article to be substantially closed; and thereafter subjecting the reaction bonded silicon nitride article and packing powder to a positive, high pressure nitrogen gas treatment at a pressure in the range from about 300 psi to about 1500 psi, while heating the reaction bonded silicon nitride article, packing powder and nitrogen gas to a treatment temperature and for a treatment time to cause a sintering of the reaction bonded silicon nitride article whereby the strength of the reaction bonded silicon nitride article is increased.
Claim 2
Independent Claim
185 words
A method of densifying an article formed of reaction bonded silicon nitride, which method comprises the steps of: packing the reaction bonded silicon nitride article in a packing mixture consisting of silicon nitride powder and a densification aid; subjecting the reaction bonded silicon nitride article and packing powder to a positive, low pressure nitrogen gas treatment at a pressure up to about 100 psi nitrogen pressure, while heating the reaction bonded silicon nitride article, packing powder and nitrogen gas to a treatment temperature and for a treatment time to cause any open porosity originally found in the reaction bonded silicon nitride article to be substantially closed; and thereafter subjecting the reaction bonded silicon nitride article and packing powder to a positive, high pressure nitrogen gas treatment at a pressure in the range from about 300 psi to about 1500 psi, while heating the reaction bonded silicon nitride article, packing powder and nitrogen gas to a treatment temperature and for a treatment time to cause a sintering of the reaction bonded silicon nitride article whereby the strength of the reaction bonded silicon nitride article is increased.
Claim 3
Dependent Claim
25 words
The method of claim 1, wherein said densification aid is selected from the group consisting of magnesium oxide, yttrium oxide, cerium oxide and zirconium oxide.
Claim 4
Independent Claim
31 words
The method of claims 1 or 2, wherein said packing mixture consists of from 4 to 20% by weight of said densification aid, the balance consisting essentially of silicon nitride powder.
Claim 5
Dependent Claim
37 words
The method of claim 1, wherein prior to packing the reaction bonded silicon nitride article in said packing mixture ths silicon nitride article is impregnated with the same densification aid which is used in said packing mixture.
Claim 6
Independent Claim
109 words
The method of claims 1, 2 or 4 wherein the densification aid is yttrium oxide, and wherein said low pressure nitrogen gas treatment is carried out a a pressure not greatly in excess of one atmosphere of nitrogen gas, with said treatment temperature not greatly in excess of 1875° C., and with said treatment time not greatly in excess of six hours; and wherein said high pressure nitrogen gas treatment is carried out at a pressure not greatly in excess of 20 atmospheres of nitrogen gas, with said treatment temperature not greatly in excess of 1925° C., and with said treatment time not greatly in excess of four hours.
Claim 7
Independent Claim
212 words
A method of densifying an article formed of reaction bonded silicon nitride, which method comprises the steps of: incorporating a densification aid into a reaction bonded silicon nitride article; enclosing the reaction bonded silicon nitride article in a chamber also containing a packing mixture consisting of silicon nitride powder and powder the same as the densification aid incorporated into the reaction bonded silicon nitride article; subjecting the reaction bonded silicon nitride article and packing mixture to a positive, low pressure nitrogen gas treatment at a pressure up to about 100 psi nitrogen pressure while heating the reaction bonded silicon nitride article, packing mixture and nitrogen gas to a treatment temperature and for a treatment time to cause any open porosity originally found in the reaction bonded silicon nitride article to be substantially closed; and thereafter subjecting the reaction bonded silicon nitride article and packing mixture to a positive, high pressure nitrogen gas treatment at a pressure in the range from about 300 psi to about 1500 psi, while heating the reaction bonded silicon nitride article, packing mixture and nitrogen gas to a treatment temperature and for a treatment time to cause a sintering of the reaction bonded silicon nitride article whereby the strength of the reaction bonded silicon nitride article is increased.
Claim 8
Independent Claim
212 words
A method of densifying an article formed of reaction bonded silicon nitride, which method comprises the steps of: incorporating a densification aid into a reaction bonded silicon nitride article; enclosing the reaction bonded silicon nitride article in a chamber also containing a packing mixture consisting of silicon nitride powder and powder the same as the densification aid incorporated into the reaction bonded silicon nitride article; subjecting the reaction bonded silicon nitride article and packing mixture to a positive, low pressure nitrogen gas treatment at a pressure up to about 100 psi nitrogen pressure while heating the reaction bonded silicon nitride article, packing mixture and nitrogen gas to a treatment temperature and for a treatment time to cause any open porosity originally found in the reaction bonded silicon nitride article to be substantially closed; and thereafter subjecting the reaction bonded silicon nitride article and packing mixture to a positive, high pressure nitrogen gas treatment at a pressure in the range from about 300 psi to about 1500 psi, while heating the reaction bonded silicon nitride article, packing mixture and nitrogen gas to a treatment temperature and for a treatment time to cause a sintering of the reaction bonded silicon nitride article whereby the strength of the reaction bonded silicon nitride article is increased.
Claim 9
Dependent Claim
38 words
The method of claim 6, wherein the reaction bonded silicon nitride article is made by a method wherein starting materials for the article are injection molded and the densification aid is included as one of the starting materials.
Claim 10
Dependent Claim
38 words
The method of claim 6, wherein the reaction bonded silicon nitride article is made by a method wherein starting materials for the article are slip cast and the densification aid is included as one of the starting materials.
Claim 11
Dependent Claim
45 words
The method of claim 6, wherein the reaction bonded silicon nitride article is made by a method wherein the shape of the article is formed in a slip cast operation and the densification aid is incorporated in the article after formation, but before nitriding thereof.
Claim 12
Independent Claim
25 words
The method of claims 6, 7, 8 or 9, wherein the mixture contained in the chamber is packed about the reaction bonded silicon nitride article.
Claim 13
Independent Claim
110 words
The method of claims 6, 7, 8 or 9 wherein the densification aid is yttrium oxide, and wherein said low pressure nitrogen gas treatment is carried out at a pressure not greatly in excess of one atmosphere of nitrogen gas, with said treatment temperature not greatly in excess of 1875° C., and with said treatment time not greatly in excess of six hours; and wherein said high pressure nitrogen gas treatment is carried out at a pressure not greatly in excess of 20 atmospheres of nitrogen gas, with said treatment temperature not greatly in excess of 1925° C., and with said treatment time not greatly in excess of four hours.
Claim 14
Independent Claim
254 words
A method of densifying an article formed of reaction bonded silicon nitride, which method comprises the steps of: incorporating a yttrium oxide densification aid into a reaction bonded silicon nitride article; packing the reaction bonded silicon nitride article in a packing mixture consisting of silicon nitride power and power the same as the densification aid incorporated into the reaction bonded silicon nitride article; subjecting the reaction bonded silicon nitride article and packing powder to a positive, low pressure nitrogen gas treatment at a pressure in a range from a positive nitrogen gas pressure to about 100 psi, while heating the reaction bonded silicon nitride article, packing powder and nitrogen gas to a treatment temperature in a range from about 1825° C. to about 1875° C., and for a treatment time from about one-half hour to about six hours to cause any open porosity originally found in the reaction bonded silicon nitride article to be substantially closed; and thereafter subjecting the reaction bonded silicon nitride article and packing powder to a positive, high pressure nitrogen gas treatment at a pressure in a range from about 300 psi to about 1500 psi, while heating the reaction bonded silicon nitride article, packing powder and nitrogen gas to a treatment temperature in a range from about 1875° C. to about 2000° C., and for a treatment time from about one-half hour to about four hours to cause a sintering of the reaction bonded silicon nitride article whereby the strength of the reaction bonded silicon nitride article is increased.
Claim 15
Independent Claim
254 words
A method of densifying an article formed of reaction bonded silicon nitride, which method comprises the steps of: incorporating a yttrium oxide densification aid into a reaction bonded silicon nitride article; packing the reaction bonded silicon nitride article in a packing mixture consisting of silicon nitride power and power the same as the densification aid incorporated into the reaction bonded silicon nitride article; subjecting the reaction bonded silicon nitride article and packing powder to a positive, low pressure nitrogen gas treatment at a pressure in a range from a positive nitrogen gas pressure to about 100 psi, while heating the reaction bonded silicon nitride article, packing powder and nitrogen gas to a treatment temperature in a range from about 1825° C. to about 1875° C., and for a treatment time from about one-half hour to about six hours to cause any open porosity originally found in the reaction bonded silicon nitride article to be substantially closed; and thereafter subjecting the reaction bonded silicon nitride article and packing powder to a positive, high pressure nitrogen gas treatment at a pressure in a range from about 300 psi to about 1500 psi, while heating the reaction bonded silicon nitride article, packing powder and nitrogen gas to a treatment temperature in a range from about 1875° C. to about 2000° C., and for a treatment time from about one-half hour to about four hours to cause a sintering of the reaction bonded silicon nitride article whereby the strength of the reaction bonded silicon nitride article is increased.
Claim 16
Dependent Claim
38 words
The method of claim 12, wherein the reaction bonded silicon nitride article is made by a method wherein starting materials for the article are injection molded and the densification aid is included as one of the starting materials.
Claim 17
Dependent Claim
38 words
The method of claim 12, wherein the reaction bonded silicon nitride article is made by a method wherein starting materials for the article are slip cast and the densification aid is included as one of the starting materials.
Claim 18
Dependent Claim
45 words
The method of claim 12, wherein the reaction bonded silicon nitride article is made by a method wherein the shape of the article is formed in a slip cast operation and the densification aid is incorporated in the article after formation but before nitriding thereof.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-10-25 | 1986-04-26 | 1986-10-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-10-25 | 1990-04-26 | 1990-10-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-10-25 | 1994-04-26 | 1994-10-26 | $7700.00 | Window Closed / Lapsed |