EP0087888A2
Expired / Lapsed
EP
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Method of forming ceramic materials and ceramic products, and ceramic materials and ceramic products formed thereby
Assignee: ZF International UK Ltd
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Filing: 1983-02-17
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Granted: —
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Expires: 2003-02-17
Abstract
Abstract A method of producing a dense ceramic product comprises the steps of mixing a ceramic powder containing a major proportion of an alpha-phase substituted silicon nitride obeying the formula M x (Si,Al) 12 (O.N) 16 , where x is not greater than 2 and M is a modifying cation (e.g. yttrium, calcium, lithium, magnesium, cerium) with at least one nitride of silicon and/or alumina wherein the alumina represents not more than 10% by weight of the mixture; and sintering the mixture in a non-oxidising atmosphere at a temperature of 1700°C to 1900°C so as to produce (1) a dense ceramic product consisting essentially of beta-phase substituted silicon nitride having the general formula Si 6-2 Al 2 -N 8-2 O 2 , where z is greater than zero and not greater than 1.5, and 0.05% wt to 20% wt of a further phase containing said modifying cation M, or (2) a dense ceramic product consisting essentially of said beta-phase substituted silicon nitride a 0.05% wt to 90% wt of an alpha-phase substituted silicon nitride obeying said formula M x (Si,Al) 12 (O,N) 16 and a minor amount of a further phase containing said modifying cation M. The ceramic powder is preferably produced by effecting a first stage nitriding by heating a powder mixture comprising silicon, aluminium alumina and an oxide or nitride of a modifying cation in a nitriding atmosphere at a temperature below the melting point of aluminium until said first stage nitriding is substantially complete; effecting a second stage nitriding by heating the first stage nitrided mixture at a temperature below the melting point of silicon whilst maintaining a nitriding atmosphere until the second stage nitriding is substantially complete whereby a friable material is produced; and subsequently sintering the comminuted friable product at a temperature between 1650°C and 1900°C whilst maintaining a non-oxidising atmosphere to obtain a friable ceramic material including more than 50% by weight of an alpha-phase substituted silicon nitride obeying the formula M x (Si,Al) 12 (O,N) 16 . where x is not greater than 1 and M is the modifying cation, or a friable ceramic material including greater than 50% by weight of a mixture of said alpha-phase substituted silicon nitride and a beta-phase substituted silicon nitride of the formula Si 6-2 Al,N 8 2 O 2 , where z is greater than zero and not greater than 1.5.
Inventors
- 👤 Edwin Granville Dr. Butler
- 👤 Andrew Dr. Szweda
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 10:41
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/597
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
185 words
A method of producing a dense ceramic product comprising the steps of mixing a ceramic powder containing a major proportion of an alpha-phase substituted silicon nitride obeying the formula M x (Si,Al) 12 (0,N) 161 where x is not greater than 2 and M is a modifying cation with at least one nitride of silicon and/or alumina wherein the alumina represents not more than 10% by weight of the mixture; and sintering the mixture in a non-oxidising atmosphere at a temperature of 1700°C to 1900°C so as to produce (1) a dense ceramic product consisting essentially of beta-phase substituted silicon nitride having the general formula Si 6-z Al z N 8-z O z , where z is greater than zero and not greater than 1.5, and a minor amount of a further phase containing said modifying cation M, or (2) a dense ceramic product consisting essentially of said beta-phase substituted silicon nitride, a controlled amount of an alpha-phase substituted silicon nitride obeying said formula M x (S i ,Al) 12 (O,N) 16 and a minor amount of a further phase containing said modifying cation M.
Claim 2
Independent Claim
185 words
A method of producing a dense ceramic product comprising the steps of mixing a ceramic powder containing a major proportion of an alpha-phase substituted silicon nitride obeying the formula M x (Si,Al) 12 (0,N) 161 where x is not greater than 2 and M is a modifying cation with at least one nitride of silicon and/or alumina wherein the alumina represents not more than 10% by weight of the mixture; and sintering the mixture in a non-oxidising atmosphere at a temperature of 1700°C to 1900°C so as to produce (1) a dense ceramic product consisting essentially of beta-phase substituted silicon nitride having the general formula Si 6-z Al z N 8-z O z , where z is greater than zero and not greater than 1.5, and a minor amount of a further phase containing said modifying cation M, or (2) a dense ceramic product consisting essentially of said beta-phase substituted silicon nitride, a controlled amount of an alpha-phase substituted silicon nitride obeying said formula M x (S i ,Al) 12 (O,N) 16 and a minor amount of a further phase containing said modifying cation M.
Claim 3
Independent Claim
362 words
A method of manufacturing a ceramic product comprising the steps of effecting a first stage nitriding by heating a powder mixture comprising silicon, aluminium, alumina and an oxide or nitride of a modifying cation in a nitriding atmosphere at a temperature below the melting point of aluminium until said first stage nitriding is substantially complete; effecting a second stage nitriding by heating the first stage nitrided mixture at a temperature below the melting point of silicon whilst maintaining a nitriding atmosphere until the second stage nitriding is substantially complete whereby a friable material is produced; comminuting the friable material thus produced; subsequently sintering the comminuted friable product at a temperature between 1650°C and 1900°C whilst maintaining a non-oxidising atmosphere to obtain a friable ceramic material including more than 50% by volume of an alpha-phase substituted silicon nitride obeying the formula Mx (Si,Al) 12 (0,N) 161 where x is not greater than 2 and M is the modifying cation, or a friable ceramic material including greater than 50% by volume of a mixture of said alpha-phase substituted silicon nitride and a beta-phase substituted silicon nitride of the formula Si 6 _ z Al z N 8-z O z , where z is greater than zero and not greater than 1.5; mixing a ceramic powder formed of said friable ceramic material with a nitride of silicon and/or alumina wherein the alumina represents not more than 10% by weight of the mixture; and sintering the mixture in a non-oxidising atmosphere at a temperature of 1700°C to 1900°C for at least 10 minutes at 1900 0 C so as to produce (1) a dense ceramic product consisting essentially of beta-phase substituted silicon nitride having the general formula Si 6-z Al z N 8-z O z , where z is greater than zero and not greater than 1.5, and a minor amount of a further phase containing said modifying cation M, or (2) a dense ceramic product consisting essentially of said beta-phase substituted silicon nitride, a controlled amount of an alpha-phase substituted silicon nitride obeying said formula M x (Si,Al) 12 (O,N) 16 , and a minor amount of a further phase containing said modifying cation M.
Claim 4
Independent Claim
362 words
A method of manufacturing a ceramic product comprising the steps of effecting a first stage nitriding by heating a powder mixture comprising silicon, aluminium, alumina and an oxide or nitride of a modifying cation in a nitriding atmosphere at a temperature below the melting point of aluminium until said first stage nitriding is substantially complete; effecting a second stage nitriding by heating the first stage nitrided mixture at a temperature below the melting point of silicon whilst maintaining a nitriding atmosphere until the second stage nitriding is substantially complete whereby a friable material is produced; comminuting the friable material thus produced; subsequently sintering the comminuted friable product at a temperature between 1650°C and 1900°C whilst maintaining a non-oxidising atmosphere to obtain a friable ceramic material including more than 50% by volume of an alpha-phase substituted silicon nitride obeying the formula Mx (Si,Al) 12 (0,N) 161 where x is not greater than 2 and M is the modifying cation, or a friable ceramic material including greater than 50% by volume of a mixture of said alpha-phase substituted silicon nitride and a beta-phase substituted silicon nitride of the formula Si 6 _ z Al z N 8-z O z , where z is greater than zero and not greater than 1.5; mixing a ceramic powder formed of said friable ceramic material with a nitride of silicon and/or alumina wherein the alumina represents not more than 10% by weight of the mixture; and sintering the mixture in a non-oxidising atmosphere at a temperature of 1700°C to 1900°C for at least 10 minutes at 1900 0 C so as to produce (1) a dense ceramic product consisting essentially of beta-phase substituted silicon nitride having the general formula Si 6-z Al z N 8-z O z , where z is greater than zero and not greater than 1.5, and a minor amount of a further phase containing said modifying cation M, or (2) a dense ceramic product consisting essentially of said beta-phase substituted silicon nitride, a controlled amount of an alpha-phase substituted silicon nitride obeying said formula M x (Si,Al) 12 (O,N) 16 , and a minor amount of a further phase containing said modifying cation M.
Claim 5
Dependent Claim
20 words
A method as claimed in claim 1 or 2, wherein the modifying cation is yttrium, calcium, lithium, magnesium or cerium.
Claim 6
Dependent Claim
29 words
A method as claimed in claim 1 or 2, wherein the dense ceramic product (2) contains 0.05% wt.to 90% wt. of said alpha-phase substituted silicon nitride obeying the formula
Claim 9
Dependent Claim
29 words
A method as claimed in claim 1 or 2, wherein said ceramic material (1) or dense ceramic product (2) contains 0.05% wt. to 20% wt. of said further phase.
Claim 10
Dependent Claim
30 words
A method as claimed in claim 1 or 2, in which the alumina content of the mixture containing said ceramic powder is less than or equal to 7.5X by weight.
Claim 11
Dependent Claim
27 words
A method as claimed in claim 1 or 2, in which said ceramic powder represents 5 to 96.5% by weight of the mixture containing said ceramic powder.
Claim 12
Dependent Claim
76 words
A method as claimed in claim 1 or 2, in which said ceramic powder is present in an amount of less than 30% by weight of the mixture containing said ceramic powder and at least one glass forming metal oxide selected from yttrium oxide, calcium oxide, lithium oxide, cerium oxide, rare earth oxides and oxides of the lanthanide series, magnesium oxide, manganese oxide, and iron oxide is also included in the mixture containing said ceramic powder.
Claim 13
Dependent Claim
35 words
A mixture as claimed in claim 8, in which said at least one glass forming metal oxide is included in an amount of less than 10% by weight of the mixture containing said ceramic powder.
Claim 14
Independent Claim
30 words
A method as claimed in any preceding claim, in which the silicon nitride is present in an amount up to 75% by weight of the mixture containing said ceramic powder.
Claim 15
Dependent Claim
30 words
A method as claimed in claim 10, in which the silicon nitride is present in an amount between 5% and 75% by weight of the mixture containing said ceramic powder.
Claim 16
Independent Claim
21 words
A method as claimed in any preceding claim, in which the product after cooling is reheated to devitrify the glass phase.
Claim 17
Dependent Claim
22 words
A method as claimed in claim 12, in which the reheating temperature is not greater than 1400°C to devitrify the glass phase.
Claim 18
Independent Claim
203 words
A method of manufacturing a ceramic material comprising the steps of effecting a first stage nitriding by heating a powder mixture comprising silicon, aluminium, alumina and an oxide or nitride of a modifying cation in a nitriding atmosphere at a temperature below the melting point of aluminium until said first stage nitriding is substantially complete; effecting a second stage nitriding by heating the first stage nitrided mixture at a temperature below the melting point of silicon whilst maintaining a nitriding atmosphere until the second stage nitriding is substantially complete whereby a friable material is produced; and subsequently sintering the comminuted friable product at a temperature between 1650°C and 1900°C whilst maintaining a non-oxidising atmosphere to obtain a friable ceramic material including more than 50% by weight of an alpha-phase substituted silicon nitride obeying the formula M x (Si,Al) 12 (O,N) 16' where x is not greater than 2 and M is the modifying cation, or a friable ceramic material including greater than 50% by weight of a mixture of said alpha-phase substituted silicon nitride and a beta-phase substituted silicon nitride of the formula Si 6-z Al z N 8-z O z , where z is greater than zero and not greater than 1.5.
Claim 19
Independent Claim
203 words
A method of manufacturing a ceramic material comprising the steps of effecting a first stage nitriding by heating a powder mixture comprising silicon, aluminium, alumina and an oxide or nitride of a modifying cation in a nitriding atmosphere at a temperature below the melting point of aluminium until said first stage nitriding is substantially complete; effecting a second stage nitriding by heating the first stage nitrided mixture at a temperature below the melting point of silicon whilst maintaining a nitriding atmosphere until the second stage nitriding is substantially complete whereby a friable material is produced; and subsequently sintering the comminuted friable product at a temperature between 1650°C and 1900°C whilst maintaining a non-oxidising atmosphere to obtain a friable ceramic material including more than 50% by weight of an alpha-phase substituted silicon nitride obeying the formula M x (Si,Al) 12 (O,N) 16' where x is not greater than 2 and M is the modifying cation, or a friable ceramic material including greater than 50% by weight of a mixture of said alpha-phase substituted silicon nitride and a beta-phase substituted silicon nitride of the formula Si 6-z Al z N 8-z O z , where z is greater than zero and not greater than 1.5.
Claim 20
Dependent Claim
19 words
A method as claimed in claim 14, in which said modifying cation is yttrium, calcium, lithium, magnesium or cerium.
Claim 21
Dependent Claim
36 words
A method according to claim 14 or 15, in which the sintering is conducted at a temperature of the order of 1820°C and the alpha-phase substituted silicon nitride occupies more than 90% of the friable product.
Claim 22
Dependent Claim
46 words
A method according to claim 14,15 or 16, in which the sintering is conducted at a temperature of the order of 1820°C and for a time of the order of 5 hours wherein the alpha-phase substituted silicon nitride occupies more than 95% of the friable product.
Claim 23
Independent Claim
29 words
A method according to claims 14 to 17, in which the modifying cation is calcium and the elements in the powder mixture are substantially balanced according to the formula
Claim 24
Independent Claim
31 words
A method according to any of claims 14 to 17, in which the mofifying cation is calcium and the elements in the powder mixture are substantially balanced according to the formula
Claim 25
Independent Claim
32 words
A method according to any of claims 14 to 17, in which the modifying cation element is lithium and the elements in the powder mixture are substantially balanced according to the formula
Claim 26
Independent Claim
33 words
A method according to any one of claims 14 to 17, in which the modifying cation element is yttrium and the elements in the powder mixture are substantially balanced according to the formula
Claim 27
Independent Claim
44 words
A method according to any one of claims 14 to 17 in which the modifying cation element is yttrium and the elements in the powder mixture are substantially balanced according to the formula Y 0.6 Si 9.2 Al 2.8 O 1.1 N 14.9 .
References Cited (Backward Citations)
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