Patent US4640902A successfully refreshed from Google Patents.
US4640902A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Low thermal conductivity Si3 N4 /ZrO2 composite ceramics
Assignee: Boeing North American Inc
•
Filing: 1985-05-31
•
Granted: 1987-02-03
•
Expires: 2005-05-31
Abstract
Abstract Improved Si 3 N 4 /ZrO 2 composite ceramics are described, having low thermal conductivity and which are substantially free of surface spalling and material degradation. Such composites are produced by incorporating an additive, e.g. MgO, CaO or Y 2 O 3 , preferably Y 2 O 3 , in suitable molar proporations based on ZrO 2 , and sintering the mixture with Si 3 N 4 . In a preferred embodiment a powder mixture of 70% Si 3 N 4 and 30% ZrO 2 , by volume, and containing 6.6 mole percent Y 2 O 3 based on ZrO 2 , is formed and is sintered to produce a composite ceramic. The Y 2 O 3 is preferably pre-reacted with the ZrO 2 to form a solid solution. A sintering aid, preferably Al 2 O 3 , e.g. in an amount of about 2 to about 4%, by weight of the total mixture, can be added to permit production of the Si 3 N 4 /ZrO 2 composite by pressureless sintering.
Inventors
- 👤 Fred F. Lange
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 22:39
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/01; C04B35/48; C04B35/486; C04B35/593
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
79 words
A composition for producing low thermal conductivity and high fracture toughness Si 3 N 4 /ZrO 2 composite ceramics substantially free of Zr-oxynitride by sintering, which comprises a mixture of about 50 to about 80% Si 3 N 4 , 20 to about 50% ZrO 2 (by volume), and Y 2 O 3 as additive in an amount from about 3 to about 7 mole % based on ZrO 2 , sufficient to prevent formation of Zr-oxynitride during sintering.
Claim 2
Dependent Claim
79 words
A composition for producing low thermal conductivity and high fracture toughness Si 3 N 4 /ZrO 2 composite ceramics substantially free of Zr-oxynitride by sintering, which comprises a mixture of about 50 to about 80% Si 3 N 4 , 20 to about 50% ZrO 2 (by volume), and Y 2 O 3 as additive in an amount from about 3 to about 7 mole % based on ZrO 2 , sufficient to prevent formation of Zr-oxynitride during sintering.
Claim 3
Dependent Claim
22 words
The composition of claim 1, said ZrO 2 and Y 2 O 3 being present in the form of a solid solution.
Claim 4
Dependent Claim
20 words
The composition of claim 1, including a sintering aid in an amount sufficient to permit pressureless sintering of said mixture.
Claim 5
Dependent Claim
28 words
The composition of claim 3, said sintering aid being Al 2 O 3 in an amount of about 1 to about 8% by weight of the total mixture.
Claim 6
Dependent Claim
50 words
The composition of claim 4, said ZrO 2 and Y 2 O 3 being pre-reacted to form a solid solution, and including Al 2 O 3 as sintering aid in an amount of about 2 to about 4% by weight of the mixture, to permit pressureless sintering of said mixture.
Claim 7
Dependent Claim
26 words
The composition of claim 3, including MgO or CaO as sintering aid in an amount of about 1 to about 8% by weight of the mixture.
Claim 8
Dependent Claim
51 words
A low thermal conductivity and high fracture toughness Si 3 N 4 /ZrO 2 composite substantially free of Zr-oxynitride and produced by sintering the composition of claim 1, said composite containing the tetragonal ZrO 2 structure and having a fracture toughness such that the composite is substantially free of surface spalling.
Claim 9
Dependent Claim
28 words
A low thermal conductivity and high fracture toughness Si 3 N 4 /ZrO 2 composite substantially free of Zr-oxynitride and produced by sintering the composition of claim 2.
Claim 10
Dependent Claim
28 words
A low thermal conductivity and high fracture toughness Si 3 N 4 /ZrO 2 composite substantially free of Zr-oxynitride and produced by sintering the composition of claim 4.
Claim 11
Dependent Claim
51 words
A low thermal conductivity and high fracture toughness Si 3 N 4 /ZrO 2 composite substantially free of Zr-oxynitride and produced by sintering the composition of claim 5, said composition containing the tetragonal ZrO 2 structure and having a fracture toughness such that the composite is substantially free of surface spalling.
Claim 12
Dependent Claim
153 words
A composition for producing low thermal conductivity and high fracture toughness Si 3 N 4 /ZrO 2 composite ceramic substantially free of Zr-oxynitride, by sintering, which comprises in volume % a mixture of about 50 to 80% Si 3 N 4 , 20 to 50% ZrO 2 and an additive selected from the group consisting of Y 2 O 3 , MgO, CaO, TiO 2 and the oxides of the rare earth elements 58-71 of the periodic Table, and mixtures thereof, said additive being present in an amount based on ZrO 2 , from about 3 to about 7 mole % for Y 2 O 3 , from about 5 to about 18 mole % for MgO or CaO from about 15 to about 35 mole % for TiO 2 and from about 9 to about 20 mole % for oxides of rare earth elements, sufficient to prevent formation of Zr-oxynitride during sintering.
Claim 13
Dependent Claim
153 words
A composition for producing low thermal conductivity and high fracture toughness Si 3 N 4 /ZrO 2 composite ceramic substantially free of Zr-oxynitride, by sintering, which comprises in volume % a mixture of about 50 to 80% Si 3 N 4 , 20 to 50% ZrO 2 and an additive selected from the group consisting of Y 2 O 3 , MgO, CaO, TiO 2 and the oxides of the rare earth elements 58-71 of the periodic Table, and mixtures thereof, said additive being present in an amount based on ZrO 2 , from about 3 to about 7 mole % for Y 2 O 3 , from about 5 to about 18 mole % for MgO or CaO from about 15 to about 35 mole % for TiO 2 and from about 9 to about 20 mole % for oxides of rare earth elements, sufficient to prevent formation of Zr-oxynitride during sintering.
Claim 14
Dependent Claim
20 words
The composition of claim 11, including a sintering aid in an amount sufficient to permit pressureless sintering of said mixture.
Claim 15
Dependent Claim
87 words
A process for producing low thermal conductivity and high fracture toughness Si 3 N 4 /ZrO 2 composite ceramic substantially free of Zr-oxynitride which comprises forming a powder mixture of about 50 to 80% Si 3 N 4 , 20 to 50% ZrO 2 (by volume) and Y 2 O 3 , and sintering said mixture, said Y 2 O 3 being present in an amount from about 3 to about 7 mole %, based on ZrO 2 , sufficient to prevent formation of Zr-oxynitride during sintering.
Claim 16
Dependent Claim
87 words
A process for producing low thermal conductivity and high fracture toughness Si 3 N 4 /ZrO 2 composite ceramic substantially free of Zr-oxynitride which comprises forming a powder mixture of about 50 to 80% Si 3 N 4 , 20 to 50% ZrO 2 (by volume) and Y 2 O 3 , and sintering said mixture, said Y 2 O 3 being present in an amount from about 3 to about 7 mole %, based on ZrO 2 , sufficient to prevent formation of Zr-oxynitride during sintering.
Claim 17
Dependent Claim
62 words
The process of claim 13, including forming an aqueous dispersion of said Si 3 N 4 , forming an aqueous dispersion of said ZrO 2 containing said Y 2 O 3 , mixing said dispersions to form a single slurry, filtering said single slurry, drying the resulting filtered powder, and sintering said powder to form a sintered composite substantially free of Zr-oxynitride.
Claim 18
Dependent Claim
20 words
The process of claim 13, said ZrO 2 and Y 2 O 3 being pre-reacted to form a solid solution.
Claim 19
Dependent Claim
22 words
The process of claim 13, said mixture including a sintering aid in an amount sufficient to permit pressureless sintering of said mixture.
Claim 20
Dependent Claim
28 words
The process of claim 16, said sintering aid being Al 2 O 3 in an amount of about 1 to about 8% by weight of the total mixture.
Claim 21
Dependent Claim
115 words
The process of claim 17, including forming an aqueous dispersion of said Si 3 N 4 , forming an aqueous dispersion of said ZrO 2 containing said Y 2 O 3 , and forming an aqueous dispersion of said Al 2 O 3 , adjusting the pH of each of said aqueous dispersions to provide uniform suspensions, floccing said dispersions to prevent mass segregation, mixing the aqueous dispersions to provide the aforementioned proportions of Si 3 N 4 , ZrO 2 , Y 2 O 3 and Al 2 O 3 , filtering the resulting single slurry, drying the composite powder residue, and sintering said powder to form a sintered composite substantially free of Zr-oxynitride.
References Cited (Backward Citations)
US4304576A
Cited
US4316964A
Cited
JPS57205374A
Cited
US4511525A
Cited
US4506024A
Cited
JPS59131579A
Cited
EP0117936A1
Cited
JPS59152254A
Cited
US4525464A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-02-02 | 1990-08-04 | 1991-02-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-02-02 | 1994-08-04 | 1995-02-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-02-02 | 1998-08-04 | 1999-02-03 | $7700.00 | Window Closed / Lapsed |