GB2195661A - Sintered silicon nitride based ceramic - Google Patents
Sintered silicon nitride based ceramic Download PDFInfo
- Publication number
- GB2195661A GB2195661A GB08624135A GB8624135A GB2195661A GB 2195661 A GB2195661 A GB 2195661A GB 08624135 A GB08624135 A GB 08624135A GB 8624135 A GB8624135 A GB 8624135A GB 2195661 A GB2195661 A GB 2195661A
- Authority
- GB
- United Kingdom
- Prior art keywords
- sintering
- silicon nitride
- alumina
- yttria
- powder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 40
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 40
- 239000000919 ceramic Substances 0.000 title claims description 11
- 238000005245 sintering Methods 0.000 claims abstract description 38
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 25
- 239000000203 mixture Substances 0.000 claims abstract description 25
- 239000000843 powder Substances 0.000 claims abstract description 21
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 claims abstract description 15
- RUDFQVOCFDJEEF-UHFFFAOYSA-N yttrium(III) oxide Inorganic materials [O-2].[O-2].[O-2].[Y+3].[Y+3] RUDFQVOCFDJEEF-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000000463 material Substances 0.000 claims abstract description 12
- 238000000034 method Methods 0.000 claims abstract description 12
- 229910010293 ceramic material Inorganic materials 0.000 claims abstract description 9
- 238000001272 pressureless sintering Methods 0.000 claims abstract description 7
- 238000006243 chemical reaction Methods 0.000 claims abstract description 5
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 6
- 238000007792 addition Methods 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 6
- 239000000395 magnesium oxide Substances 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- 230000002411 adverse Effects 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 238000003825 pressing Methods 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- 239000010703 silicon Substances 0.000 claims description 4
- 229910052582 BN Inorganic materials 0.000 claims description 2
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 2
- 238000000498 ball milling Methods 0.000 claims description 2
- 230000015556 catabolic process Effects 0.000 claims description 2
- 238000006731 degradation reaction Methods 0.000 claims description 2
- 238000010494 dissociation reaction Methods 0.000 claims description 2
- 230000005593 dissociations Effects 0.000 claims description 2
- 230000000694 effects Effects 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 claims description 2
- 238000000462 isostatic pressing Methods 0.000 claims description 2
- 239000011812 mixed powder Substances 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims description 2
- 239000000377 silicon dioxide Substances 0.000 claims description 2
- 239000011863 silicon-based powder Substances 0.000 claims description 2
- 238000000280 densification Methods 0.000 abstract 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Ceramic Products (AREA)
Abstract
Ceramic material based on silicon nitride is described employing an oxide mixture as a sintering aid to provide densification at normal temperatures by the pressureless sintering technique. The composition of the sintered material comprises 6 to 12 wt% yttria, 1 to 4 wt% alumina, 1 to 4 wt% chromia and balance silicon nitride. The material may be produced by the sintering of a powder mixture containing silicon nitride or by the reaction bonding process as an intermediate step.
Description
SPECIFICATION
Ceramics
The present invention relates to the production of silicon nitride ceramics and particularly to additions which improve the sintering behaviour of silicon nitride.
In order to achieve sintering of bodies produced from silicon nitride powders other oxides are usually added as sintering aids. Mixtures of yttria and alumina are well known in this regard and have been used to produce almost fully dense silicon nitride. One technique used for sintering silicon nitride powders is often referred to as pressureless sintering where the gas atmosphere in the sintering furnace is at approximately ambient or one atmosphere. To achieve high density an alumina content in the range 4 to 6 wt% is typically required. Such high levels of alumina are disadvantageous in that the high temperature properties of the resulting sintered silicon nitride are adversely affected. To lessen the adverse effect of the alumina on the high temperature properties the level of alumina additions may be reduced.However, at lower levels of alumina addition it is necessary to increase the sintering temperature to achieve a comparable final density. Because of the increased sintering temperature it then becomes necessary to increase the pressure of the gas atmosphere in which the silicon nitride is sintered to prevent or minimise dissociation of the material. This requires much more costly equipment capable of maintaining relatively high gas pressures at very high sintering temperatures.
An alternative known sintering aid used for pressureless sintering is based on the mixture 10% yttria-2% magnesia-2% chromia. This produces high density silicon nitride. The magnesia, however, tends to be lost from the material due to the high temperature during sintering. Loss of magnesia may be partly compensated for by embedding the ceramic part being sintered in a magnesia containing powder bed. In practice this method is inconvenient and messy and eventually leads to costly furnace degradation.
It has now been found that the above disadvantages may be overcome by the use of a new composition of oxides used as a sintering aid.
According to the present invention a ceramic composition comprises 6 to 12 wt% yttria, 1 to 4 wt% alumina, 1 to 4 wt% chromia and balance silicon nitride.
It has been found that silicon nitride having good high temperature properties and a density greater than 98% theoretical may be produced by pressureless sintering without the need of sintering aids in the powder bed surrounding the ceramic during sintering. The basis of a powder bed used when sintering silicon nitride may typically include 50% boron nitride, 45% silicon nitride and 5% silica.
In order that the present invention may be more fully understood an example will now be given by way of illustration only.
Silicon nitride powder of typically 2-3 micron particle size was mixed with 10 wt% yttria, 2 wt% alumina and 2 wt% chromia by ball milling in PROPAN-2-OL alcohol. The mixture was then dried, sieved and compacted by isostatic pressing at 25,000 p.s.i. The compact was then sintered in 1 atmosphere of nitrogen at 1800 C for 5 hours.
The resulting sintered material had a density of approximately 3,25 gm/cc.
Instead of starting with silicon nitride powder as described above the well-known reaction bonding method may be employed. Silicon powder may be mixed with the sintering aids and prior to final sintering an intermediate stage of heating the compacted powder mixture in nitrogen at temperatures up to 1420"C for many hours to convert the silicon to silicon nitride is used.
1. A ceramic material composition comprising 6 to 12 wt% yttria, 1 to 4 wt% alumina, 1 to 4 wt% chromia and balance silicon nitride.
2. A ceramic material composition according to Claim 1 comprising 10 wt% yttria, 2 wt% alumina, 2 wt% chromia and balance silicon nitride.
3. A process for the production of a ceramic material comprising the steps of mixing a powder having the composition 6 to 12 wt% yttria, 1 to 4 wt% alumina, 1 to 4 wt% chromia and balance silicon nitride, pressing the mixed powder to form a compact and then sintering the compact to densify the material.
4. A process for the production of a ceramic material comprising the steps of mixing a powder having the composition 6 to 12 wt% yttria, 1 to 4 wt% alumina, 1 to 4 wt% chromia and balance silicon, pressing the mixed composition to form a compact, performing a reaction bonding treatment on the pressed compact and then sintering to densify the material.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (4)
1. A ceramic material composition comprising 6 to 12 wt% yttria, 1 to 4 wt% alumina, 1 to 4 wt% chromia and balance silicon nitride.
2. A ceramic material composition according to Claim 1 comprising 10 wt% yttria, 2 wt% alumina, 2 wt% chromia and balance silicon nitride.
3. A process for the production of a ceramic material comprising the steps of mixing a powder having the composition 6 to 12 wt% yttria, 1 to 4 wt% alumina, 1 to 4 wt% chromia and balance silicon nitride, pressing the mixed powder to form a compact and then sintering the compact to densify the material.
4. A process for the production of a ceramic material comprising the steps of mixing a powder having the composition 6 to 12 wt% yttria, 1 to 4 wt% alumina, 1 to 4 wt% chromia and balance silicon, pressing the mixed composition to form a compact, performing a reaction bonding treatment on the pressed compact and then sintering to densify the material.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8624135A GB2195661B (en) | 1986-10-08 | 1986-10-08 | Ceramics |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8624135A GB2195661B (en) | 1986-10-08 | 1986-10-08 | Ceramics |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8624135D0 GB8624135D0 (en) | 1986-11-12 |
| GB2195661A true GB2195661A (en) | 1988-04-13 |
| GB2195661B GB2195661B (en) | 1990-01-10 |
Family
ID=10605429
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8624135A Expired - Fee Related GB2195661B (en) | 1986-10-08 | 1986-10-08 | Ceramics |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2195661B (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1406571A (en) * | 1972-10-24 | 1975-09-17 | Toyoda Chuo Kenkyusho Kk | Method for producing a sintered silicon mitride base ceramic and said ceramic product |
-
1986
- 1986-10-08 GB GB8624135A patent/GB2195661B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1406571A (en) * | 1972-10-24 | 1975-09-17 | Toyoda Chuo Kenkyusho Kk | Method for producing a sintered silicon mitride base ceramic and said ceramic product |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8624135D0 (en) | 1986-11-12 |
| GB2195661B (en) | 1990-01-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19921008 |