US5401450A
Expired / Lapsed
US
⏱️ 0.0 years remaining
β-silicon nitride sintered body and method of producing same
Assignee: Nissan Motor Co Ltd
•
Filing: 1992-12-18
•
Granted: 1995-03-28
•
Expires: 2012-12-18
Abstract
Abstract A high strength and toughness beta -silicon nitride sintered body suitable for the material of a variety of structural parts. The sintered body contains beta -silicon nitride (Si3N4) in an amount not less than 95% by weight of total silicon nitride; oxygen in a total amount not more than 3% by weight of the sintered body; and columnar grains each of which has a diameter not less than 5 mu m and an aspect ratio not less than 5, the columnar grains being in an amount not less than 0.5% by volume of total of raw materials in the sintered body; the sintered body having a bulk density not less than 96% of a theoretical density. Such a sintered body is produced by a method comprising the following steps in the sequence set forth: preparing powder of a starting material including beta -silicon nitride in an amount not less than 80% by weight of the starting material; adding oxide of at least one element selected from the group IIIa of the periodic table of elements in an amount ranging from 0.2% to 6% by weight (as a sintering assistant) to the starting material powder to form a mixture powder; compacting the mixture powder to form a compact; firing the compact under a nitrogen gas pressure ranging from 1 to 500 atm. at a temperature ranging from 1700 DEG to 2100 DEG C. to form the sintered body; and continuing the firing step until a bulk density of the sintered body reaches a value not less than 96% of a theoretical density of the sintered body.
Inventors
- 👤 Mamoru Mitomo
- 👤 Naoto Hirosaki
- 👤 Motohide Ando
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 11:30
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593; C04B35/5935
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
310 words
A method of producing a β-silicon nitride sintered body, comprising the following steps in the sequence set forth: preparing powder of a starting material including β-silicon nitride in an amount not less than 80% by weight of the starting material; adding oxide of at least one element selected from the group IIIa of the periodic table of elements in an amount ranging from 0.2% to 6% by weight to the starting material powder to form a mixture powder; compacting said mixture powder to form a compact; firing said compact under a nitrogen gas pressure ranging from 1 to 500 atm, at a temperature ranging from 1700° to 2100° C. to form the sintered body; and continuing the firing step until a bulk density of the sintered body reaches a value not less than 96% of a theoretical density of the sintered body; wherein said starting material powder includes a first β-silicon nitride powder in an amount ranging from 80 to 98% by weight, and a second β-silicon nitride powder in an amount ranging from 2 to 20% by weight, said first β-silicon nitride powder including α-silicon nitride and β-silicon nitride which is in an amount not less than 95% by weight, said silicon nitride powder containing particles having a particle diameter not larger than 0.7 μm, in an amount not less than 90% by weight of total particles, said first β-silicon nitride powder having a means particle diameter not larger than 0.5 μm, said second β-silicon nitride powder including α-silicon nitride powder and β-silicon nitride powder which is in an amount not less than 95% by weight, said silicon nitride powder containing particles having an aspect ratio ranging from 2 to 10 and a shorter axis diameter ranging from 0.5 to 5 μm, in an amount not less than 70% by weight of total of said second β-silicon nitride powder.
Claim 2
Independent Claim
310 words
A method of producing a β-silicon nitride sintered body, comprising the following steps in the sequence set forth: preparing powder of a starting material including β-silicon nitride in an amount not less than 80% by weight of the starting material; adding oxide of at least one element selected from the group IIIa of the periodic table of elements in an amount ranging from 0.2% to 6% by weight to the starting material powder to form a mixture powder; compacting said mixture powder to form a compact; firing said compact under a nitrogen gas pressure ranging from 1 to 500 atm, at a temperature ranging from 1700° to 2100° C. to form the sintered body; and continuing the firing step until a bulk density of the sintered body reaches a value not less than 96% of a theoretical density of the sintered body; wherein said starting material powder includes a first β-silicon nitride powder in an amount ranging from 80 to 98% by weight, and a second β-silicon nitride powder in an amount ranging from 2 to 20% by weight, said first β-silicon nitride powder including α-silicon nitride and β-silicon nitride which is in an amount not less than 95% by weight, said silicon nitride powder containing particles having a particle diameter not larger than 0.7 μm, in an amount not less than 90% by weight of total particles, said first β-silicon nitride powder having a means particle diameter not larger than 0.5 μm, said second β-silicon nitride powder including α-silicon nitride powder and β-silicon nitride powder which is in an amount not less than 95% by weight, said silicon nitride powder containing particles having an aspect ratio ranging from 2 to 10 and a shorter axis diameter ranging from 0.5 to 5 μm, in an amount not less than 70% by weight of total of said second β-silicon nitride powder.
Claim 3
Independent Claim
287 words
A method of producing a β-silicon nitride sintered body, comprising the following steps in the sequence set forth below: preparing a mixture powder by mixing a first β-silicon nitride powder in an amount ranging from 80 to 98% by weight, and a second β-silicon nitride powder in an amount ranging from 2 to 20% by weight, said first β-silicon nitride powder including α-silicon nitride and β-silicon nitride which is in an amount not less than 95% by weight, said first β-silicon nitride powder containing particles having a particle diameter not larger than 0.7 μm, in an amount not less than 90% by weight of total particles, said first β-silicon nitride powder having a mean particle diameter not larger than 0.5 μm, said second β-silicon nitride powder including α-silicon nitride powder and β-silicon nitride powder which is in an amount not less than 95% by weight, said silicon nitride powder containing particles having an aspect ratio ranging from 2 to 10 and a diameter ranging from 0.5 to 5 μm, in an amount not less than 70% by weight of total of said second β-silicon nitride powder; adding to the mixture powder at least one selected from the group consisting of CaO, MgO, Al 2 O 3 and oxides of elements of the group IIIa of the periodic table of elements, in an amount ranging from 0.2 to 15% by weight of the mixture; compacting the mixture powder to form a compact; and firing the compact at a temperature ranging from 1600° to 2100° C. until the β-silicon nitride sintered body have columnar grains each of which has a diameter not less than 3 μm, in an amount not less than 5% by volume of the sintered body.
Claim 4
Independent Claim
287 words
A method of producing a β-silicon nitride sintered body, comprising the following steps in the sequence set forth below: preparing a mixture powder by mixing a first β-silicon nitride powder in an amount ranging from 80 to 98% by weight, and a second β-silicon nitride powder in an amount ranging from 2 to 20% by weight, said first β-silicon nitride powder including α-silicon nitride and β-silicon nitride which is in an amount not less than 95% by weight, said first β-silicon nitride powder containing particles having a particle diameter not larger than 0.7 μm, in an amount not less than 90% by weight of total particles, said first β-silicon nitride powder having a mean particle diameter not larger than 0.5 μm, said second β-silicon nitride powder including α-silicon nitride powder and β-silicon nitride powder which is in an amount not less than 95% by weight, said silicon nitride powder containing particles having an aspect ratio ranging from 2 to 10 and a diameter ranging from 0.5 to 5 μm, in an amount not less than 70% by weight of total of said second β-silicon nitride powder; adding to the mixture powder at least one selected from the group consisting of CaO, MgO, Al 2 O 3 and oxides of elements of the group IIIa of the periodic table of elements, in an amount ranging from 0.2 to 15% by weight of the mixture; compacting the mixture powder to form a compact; and firing the compact at a temperature ranging from 1600° to 2100° C. until the β-silicon nitride sintered body have columnar grains each of which has a diameter not less than 3 μm, in an amount not less than 5% by volume of the sintered body.
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) | 1998-03-27 | 1998-09-26 | 1999-03-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-03-27 | 2002-09-26 | 2003-03-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-03-27 | 2006-09-26 | 2007-03-28 | $7700.00 | Window Closed / Lapsed |