JPS631273B2 - - Google Patents
Info
- Publication number
- JPS631273B2 JPS631273B2 JP57149382A JP14938282A JPS631273B2 JP S631273 B2 JPS631273 B2 JP S631273B2 JP 57149382 A JP57149382 A JP 57149382A JP 14938282 A JP14938282 A JP 14938282A JP S631273 B2 JPS631273 B2 JP S631273B2
- Authority
- JP
- Japan
- Prior art keywords
- sintering
- atmosphere
- powder
- stage
- sintered body
- 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.)
- Expired
Links
- 238000005245 sintering Methods 0.000 claims description 40
- 239000000843 powder Substances 0.000 claims description 25
- 238000000034 method Methods 0.000 claims description 24
- 239000012298 atmosphere Substances 0.000 claims description 17
- 239000007789 gas Substances 0.000 claims description 7
- 238000000354 decomposition reaction Methods 0.000 claims description 6
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 5
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 239000001301 oxygen Substances 0.000 claims description 3
- 238000000280 densification Methods 0.000 claims description 2
- 238000001704 evaporation Methods 0.000 claims description 2
- 230000008020 evaporation Effects 0.000 claims 1
- 230000000630 rising effect Effects 0.000 claims 1
- 239000000126 substance Substances 0.000 description 6
- 239000000919 ceramic Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052574 oxide ceramic Inorganic materials 0.000 description 1
- 239000011224 oxide ceramic Substances 0.000 description 1
- 238000009700 powder processing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
Description
【発明の詳細な説明】
(イ) 技術の背景
この発明は高温強度が高く、高密度を有する窒
化けい素焼結体を得るための窒化けい素の焼結方
法に関するものである。
最近セラミツクス材料、特に耐熱性材料として
のセラミツクスの開発が盛んに行われており、な
かでも高温において安定な耐熱性物質である共有
結合性化合物、特に窒化けい素（Si3N4）が非常
にすぐれた材料であることが知られている。
一般にセラミツクスは、原料セラミツクス粉末
を成形焼結して使用されるものであるが、Si3N4
の場合は、一般の酸化物セラミツクスと異なり、
難焼結性物質であるため、単独組成たとえば
Si3N4の粉末のみを焼結しても緻密な焼結体を得
ることは困難である。
このためSi3N4粉末の場合などにはMgO、
Al2O3、Y2O3、CeO2、BeOなどの酸化物粉末を
焼結助剤として添加して焼結することが行われて
いる。
しかしてこのような焼結助剤を加えたSi3N3粉
末を使用して通常行われているプレス成形をして
真空あるいは常圧で加熱焼結する方法は、焼結コ
ストが低く工業的に有用ではあるが、Si3N4焼結
体に微孔がそのまま残存するので高密度の焼結体
を得ることは困難である。
これに対して、高温下で加圧しながら焼結する
ホツトプレス法は、より緻密な焼結体を得ること
はできるが、高温において強度低下が生ずる欠点
があり、また焼結コストが高くつくという難点が
ある。
この高温における強度低下は、焼結助剤の添加
によりSi3N4の粉末界面に低融点物質が生成する
ことによるものであると考えられ、焼結助剤を使
用する場合は不可避である。
さらに焼結助剤の混合割合を減少し、あるいは
焼結助剤を添加せずに高圧ガス雰囲気中で焼結し
たり、爆発成型などで粉末に瞬間的に高圧を加え
て粉砕したのち、焼結するなどの方法が試みられ
ているが、何れの方法も焼結コストが高く、また
高温強度の低下現象が残る欠点があり、工業的な
方法として成功していない。
本発明者らは上記の点に鑑みて焼結助剤を用い
ながら高温強度、高密度のSi3N4焼結体を得る
Si3N4粉末の焼結法について、Si3N4粉末をプレ
ス成形したのち、真空、減圧あるいは加圧などの
各種の雰囲気および温度など焼結条件を変化させ
て焼結を行つて試験を繰返した結果、この発明に
至つたものである。
(ロ) 発明の開示
即ち、本発明は、焼結助剤を添加したSi3N4粉
末を成形体を焼結するに際し、焼結時の昇温過程
を同一焼結炉内で、
（第１段階）
真空雰囲気または還元性減圧雰囲気下で、成形
体粉末に吸着している酸素または水分等を蒸発ま
たは分解除去する工程
（第２段階）
Iatm（atmosphere、気圧、以下同じ）以下の
N2分圧を有する減圧雰囲気で粉末成形体表面の
酸化膜を除去しながら焼結する工程
（第３段階）
1atm以上のN2分圧を有する加圧雰囲気で焼結
を進行させる工程
（第４段階）
1000atm以上のN2またはArまたはArとN2の混
合ガス加圧雰囲気でさらに焼結体をち密化する工
程の４段階で行うことを特徴とするもので、これ
によつて高密度、高強度で、高温での強度劣化の
少いSi3N4焼結体が得られるのである。
本発明の方法において、第１段階は、原料とな
るSi3N4粉末や焼結助剤粉末から、もしくは粉末
処理工程で含有または吸着する酸素、水分または
有機物等の焼結阻害物もしくは、焼結体中に残留
し、焼結体特性を劣化させる物質を除去しようと
するものであり、真空または還元性雰囲気で行わ
れる。処理温度範囲は、上記有害物質の除去効果
とSi3N4粉末や焼結助剤粉末が分解しないという
観点から室温から1100℃の範囲で行うことが好ま
しい。
また第２段階は、成形体を構成するSi3N4粉末
表面の酸化物を除去しつつ焼結を進行させる工程
であり、この工程では液相が発生し、ち密化が開
始するので、雰囲気圧力としては減圧とし、焼結
体中に雰囲気ガスまたは、被焼結体から発生する
ガスがトラツプされることによる空孔の残留を防
がなければならない。雰囲気ガスとしては、被焼
結体の分解を抑えるためにN2分圧を必要とし、
また粉末表面の酸化物除去効果を高めるため、
H2またはCOガス分圧を加えることが有効であ
る。処理温度としては、800〜1700℃の範囲で行
うことが好ましい。800℃以下の温度では酸化物
除去効果が期待できない。また1700℃以上での減
圧処理は、Si3N4粉末の分解を促進するので好ま
しくない。
第３段階は本来の焼結過程であり、したがつて
Si3N4の分解を抑制しつつ焼結を進行させるため
1atm以上のN2分圧を有する加圧雰囲気を必要と
する。処理温度は用いる焼結助剤の種類によつて
も異なるが一般に1500〜2000℃の範囲に入る。
第４段階は、第３段階までの過程で残留する空
孔を除去し、焼結体をち密化するための1000atm
以上の雰囲気圧力で熱間静圧する工程である。一
般には1000atm以上の圧力下での熱間静圧処理は
Ar雰囲気で行わているが、Si3N4焼結体の処理で
はN2雰囲気中またはN2とArの混合ガス雰囲気で
行うのがSi3N4の分解を抑えるためには好まし
い。温度は1600〜2000℃の範囲が効果的である。
以上示した様に本発明によれば、同一炉体内
で、気中に取り出すことなく連続的に、成形体
粉末に吸着している有害物の除去する工程、成
形体粉末表面の酸化膜を除去しつつ焼結する工
程、加圧N2雰囲気でSi3N4の分解を抑えつつ焼
結を進行させる工程、焼結体に含まれる空孔を
高圧雰囲気で除去し、焼結体をち密化する工程を
行うことができ、高純度、高密度、高強度で、高
温での強度特性劣化の少ない焼結体を得ることが
できる。
実施例
Si3N489wt％、Al2O37％、Y2O34％の粉末混合
物を試験片形状に型押成形し、下記条件にて焼結
した焼結体を研削後、曲げ強度を測定した結果を
第１表に示す。
【表】DETAILED DESCRIPTION OF THE INVENTION (a) Background of the Technology The present invention relates to a method for sintering silicon nitride to obtain a silicon nitride sintered body having high high-temperature strength and high density. Recently, the development of ceramic materials, especially ceramics as heat-resistant materials, has been actively conducted. Among them, covalent compounds, especially silicon nitride (Si 3 N 4 ), which are heat-resistant substances that are stable at high temperatures, are very popular. It is known to be an excellent material. Ceramics are generally used by molding and sintering raw ceramic powder, but Si 3 N 4
In the case of , unlike general oxide ceramics,
Because it is a difficult-to-sinter material, individual compositions such as
Even if only Si 3 N 4 powder is sintered, it is difficult to obtain a dense sintered body. Therefore, in the case of Si 3 N 4 powder, MgO,
Sintering is carried out by adding oxide powder such as Al 2 O 3 , Y 2 O 3 , CeO 2 , BeO, etc. as a sintering aid. However, the conventional method of press forming Si 3 N 3 powder containing a sintering aid and then heating and sintering it in vacuum or normal pressure is low in sintering cost and industrially viable. However, since micropores remain in the Si 3 N 4 sintered body, it is difficult to obtain a high-density sintered body. On the other hand, the hot press method, in which sintering is carried out under pressure at high temperatures, can produce a more dense sintered body, but it has the drawbacks of a decrease in strength at high temperatures and high sintering costs. There is. This decrease in strength at high temperatures is thought to be due to the formation of low melting point substances at the Si 3 N 4 powder interface due to the addition of the sintering aid, and is unavoidable when a sintering aid is used. Furthermore, the mixing ratio of the sintering aid may be reduced, or the powder may be sintered in a high-pressure gas atmosphere without the addition of a sintering aid, or the powder may be pulverized by instantaneously applying high pressure using explosive molding, etc., and then sintered. Methods such as sintering have been attempted, but all of these methods have the drawbacks of high sintering costs and a reduction in high-temperature strength, and have not been successful as industrial methods. In view of the above points, the present inventors obtained a Si 3 N 4 sintered body with high temperature strength and high density while using a sintering aid.
Regarding the sintering method of Si 3 N 4 powder, we conducted tests by press-forming Si 3 N 4 powder and then sintering it under various sintering conditions such as vacuum, reduced pressure, or pressurization, and various sintering conditions such as temperature. As a result of repeated efforts, this invention was achieved. (b) Disclosure of the Invention In other words, the present invention provides that, when sintering a compact of Si 3 N 4 powder to which a sintering aid has been added, the temperature raising process during sintering is carried out in the same sintering furnace. Step 1) A process of evaporating or decomposing oxygen or moisture adsorbed to the compact powder in a vacuum atmosphere or reducing reduced pressure atmosphere (Step 2)
A process of sintering while removing the oxide film on the surface of the powder compact in a reduced pressure atmosphere with a partial pressure of N 2 (third stage) A process of proceeding with sintering in a pressurized atmosphere with a partial pressure of N 2 of 1 atm or more (the third stage) 4 steps) This method is characterized by the process of further densifying the sintered body in a pressurized atmosphere of N 2 or Ar or a mixture of Ar and N 2 at 1000 atm or more, which results in high density. , a Si 3 N 4 sintered body with high strength and little deterioration in strength at high temperatures can be obtained. In the method of the present invention, the first step is to remove sintering inhibitors such as oxygen, moisture, or organic substances contained or adsorbed from the raw material Si 3 N 4 powder or sintering aid powder or during the powder processing step. The purpose is to remove substances that remain in the sintered body and deteriorate the properties of the sintered body, and is carried out in a vacuum or in a reducing atmosphere. The treatment temperature range is preferably from room temperature to 1100° C. from the viewpoint of the effect of removing the above-mentioned harmful substances and preventing the Si 3 N 4 powder and sintering aid powder from decomposing. The second stage is a process in which sintering progresses while removing oxides on the surface of the Si 3 N 4 powder that makes up the compact. In this process, a liquid phase is generated and densification begins, so the atmosphere is The pressure must be reduced to prevent pores from remaining in the sintered body due to trapping of atmospheric gas or gas generated from the sintered body. As the atmospheric gas, a partial pressure of N2 is required to suppress the decomposition of the sintered body.
In addition, to enhance the effect of removing oxides from the powder surface,
Applying a partial pressure of H2 or CO gas is effective. The treatment temperature is preferably in the range of 800 to 1700°C. Oxide removal effects cannot be expected at temperatures below 800°C. Further, reduced pressure treatment at 1700° C. or higher is not preferable because it promotes decomposition of the Si 3 N 4 powder. The third stage is the actual sintering process and therefore
To advance sintering while suppressing the decomposition of Si 3 N 4
Requires a pressurized atmosphere with a N2 partial pressure of 1 atm or more. Although the treatment temperature varies depending on the type of sintering aid used, it is generally in the range of 1500 to 2000°C. The fourth stage is 1000 atm to remove the pores remaining in the process up to the third stage and densify the sintered body.
This is a step of applying hot static pressure at the above atmospheric pressure. Generally, hot static pressure treatment under pressure of 1000atm or more is
Although the treatment is carried out in an Ar atmosphere, in order to suppress the decomposition of Si 3 N 4 , it is preferable to carry out the treatment in an N 2 atmosphere or a mixed gas atmosphere of N 2 and Ar when processing a Si 3 N 4 sintered body. A temperature range of 1600 to 2000°C is effective. As described above, according to the present invention, there is a process of continuously removing harmful substances adsorbed to the compact powder in the same furnace body without taking it out into the air, and removing an oxide film on the surface of the compact powder. The process of sintering while suppressing the decomposition of Si 3 N 4 in a pressurized N 2 atmosphere, the process of removing the pores contained in the sintered body in a high-pressure atmosphere, and making the sintered body dense. A sintered body with high purity, high density, high strength, and little deterioration of strength properties at high temperatures can be obtained. Example A powder mixture of 89 wt% Si 3 N 4 , 7% Al 2 O 3 , and 4% Y 2 O 3 was pressed into the shape of a test piece, and the sintered body was sintered under the following conditions. After grinding, the sintered body was bent. The results of measuring the strength are shown in Table 1. 【table】
Claims (1)
を焼結するに際し、昇温過程において同一焼結炉
内で、 （第１段階） 真空雰囲気または還元性減圧雰囲気下で成形体
中に吸着している酸素または水分等を室温から
1100℃まで蒸発または分解除去する工程 （第２段階） Iatm以下のN2分圧を有する減圧雰囲気で粉末
成形体表面の酸化膜を除去しながら800〜1700℃
の範囲で焼結させる工程 （第３段階） Iatm以上のN2分圧を有する加圧雰囲気で1500
〜2000℃の範囲で焼結を進行させる工程 （第４段階） 1000atm以上のN2またはArまたはArとN2の混
合ガス加圧雰囲気で1600〜2000℃の範囲でさらに
焼結体を緻密化する工程の４段階を経ることを特
徴とする窒化けい素の焼結方法。[Claims] 1. When sintering a green compact of silicon nitride powder to which a sintering aid has been added, in the same sintering furnace during the temperature rising process, (first stage) a vacuum atmosphere or reducing pressure Removes oxygen, moisture, etc. adsorbed in the molded product under an atmosphere from room temperature.
Evaporation or decomposition removal process to 1100℃ (second stage) 800 to 1700℃ while removing the oxide film on the surface of the powder compact in a reduced pressure atmosphere with N2 partial pressure below Iatm
Sintering process (third stage) in a pressurized atmosphere with a N2 partial pressure of more than Iatm 1500
The process of proceeding with sintering in the range of ~2000℃ (4th stage) Further densification of the sintered body in the range of 1600~2000℃ in a pressurized atmosphere of N 2 or Ar or a mixed gas of Ar and N 2 at 1000 atm or more A method for sintering silicon nitride, which is characterized by passing through four steps.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57149382A JPS5939769A (en) | 1982-08-28 | 1982-08-28 | Method of sintering silicon nitride |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57149382A JPS5939769A (en) | 1982-08-28 | 1982-08-28 | Method of sintering silicon nitride |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5939769A JPS5939769A (en) | 1984-03-05 |
| JPS631273B2 true JPS631273B2 (en) | 1988-01-12 |
Family
ID=15473902
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP57149382A Granted JPS5939769A (en) | 1982-08-28 | 1982-08-28 | Method of sintering silicon nitride |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5939769A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4892848A (en) * | 1985-07-30 | 1990-01-09 | Kyocera Corporation | Silicon nitride sintered body and process for preparation thereof |
| JPS63206358A (en) * | 1987-02-20 | 1988-08-25 | 日本碍子株式会社 | Manufacture of silicon nitride sintered body |
| JPH01290561A (en) * | 1988-05-18 | 1989-11-22 | Nippon Cement Co Ltd | Production of silicon nitride-based ceramic sintered body |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53102320A (en) * | 1977-01-03 | 1978-09-06 | Gen Electric | Silicon nitride sintered articles and manufacture thereof |
| JPS55116675A (en) * | 1979-02-27 | 1980-09-08 | Ngk Insulators Ltd | Manufacture of silicon nitride sintered body |
| JPS57106574A (en) * | 1980-12-19 | 1982-07-02 | Kobe Steel Ltd | Method of sintering silicon nitride |
-
1982
- 1982-08-28 JP JP57149382A patent/JPS5939769A/en active Granted
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53102320A (en) * | 1977-01-03 | 1978-09-06 | Gen Electric | Silicon nitride sintered articles and manufacture thereof |
| JPS55116675A (en) * | 1979-02-27 | 1980-09-08 | Ngk Insulators Ltd | Manufacture of silicon nitride sintered body |
| JPS57106574A (en) * | 1980-12-19 | 1982-07-02 | Kobe Steel Ltd | Method of sintering silicon nitride |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5939769A (en) | 1984-03-05 |
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