JPH0555444B2 - - Google Patents
Info
- Publication number
- JPH0555444B2 JPH0555444B2 JP63277360A JP27736088A JPH0555444B2 JP H0555444 B2 JPH0555444 B2 JP H0555444B2 JP 63277360 A JP63277360 A JP 63277360A JP 27736088 A JP27736088 A JP 27736088A JP H0555444 B2 JPH0555444 B2 JP H0555444B2
- Authority
- JP
- Japan
- Prior art keywords
- powder
- silicon nitride
- less
- oxygen
- weight
- 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 - Lifetime
Links
- 239000000843 powder Substances 0.000 claims description 63
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 28
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 27
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 24
- 239000001301 oxygen Substances 0.000 claims description 24
- 229910052760 oxygen Inorganic materials 0.000 claims description 24
- 239000002245 particle Substances 0.000 claims description 22
- 238000000034 method Methods 0.000 description 16
- 238000005245 sintering Methods 0.000 description 12
- 239000013078 crystal Substances 0.000 description 8
- 238000005452 bending Methods 0.000 description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 229910052710 silicon Inorganic materials 0.000 description 5
- 239000010703 silicon Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000005121 nitriding Methods 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000000280 densification Methods 0.000 description 2
- RAABOESOVLLHRU-UHFFFAOYSA-N diazene Chemical compound N=N RAABOESOVLLHRU-UHFFFAOYSA-N 0.000 description 2
- 229910000071 diazene Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- -1 silicon halide Chemical class 0.000 description 2
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000006298 dechlorination reaction Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 150000003949 imides Chemical class 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 1
- 238000013001 point bending Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000005049 silicon tetrachloride Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/0602—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with two or more other elements chosen from metals, silicon or boron
Description
〔産業上の利用分野〕
本発明は、高温強度の大きな焼結体を製造する
ことができる窒化ケイ素粉末に関する。
窒化ケイ素は、高温構造材料としてガスタービ
ン部材、ノズル、軸受等に利用されている。
〔従来の技術〕
従来、窒化ケイ素粉末の製法としては、(1)金属
ケイ素直接窒化法、(2)シリカ還元窒化法、(3)ハロ
ゲン化ケイ素法が知られている。これらの方法で
つくられる粉末は、製造履歴が異なるためか、金
属不純物量や酸素量或いは粒径、比表面積が同程
度であつても、粉末の焼結性や焼結後の焼結体の
特性例えば曲げ強度に大きな違いがある。
一般的には、(1)の方法で製造された粉末は易焼
結性であるが高温曲げ強度が低い、(2)の方法の粉
末は難焼結性であるが高温曲げ強度が高い、(3)の
方法の粉末は中間的な性能を示すといわれてい
る。
酸素量については、(1)の方法の粉末は粉砕工程
を経るため通常全酸素量が２重量％を超える場合
が多く少なくても1.5重量％はある。(1)の方法で
不純物除去のために酸処理等の工程を通すと全酸
素量は低減するがそれでも1.0重量％未満にする
ことは難しい。一方、(2)の方法の粉末でも、原料
としてシリカ粉末を用いるためにシリカの残留が
あり、全酸素量は２重量％を超えるのが普通であ
る。
以上の粉末が現状入手可能なものである。当然
のことながら、粉末の焼結性及び焼結体特性には
粉体酸素量の影響があるのは勿論であるが、その
他に比表面積、結晶性、粒子形状、粒度（微粉）
等様々の粉体特性がからみあつており、前記各製
法の粉末特性が粉体特性にどのように関係してい
るかは殆んどわかつていないのが現状である。
特公昭61−43311号公報には、窒化ケイ素粉末
の酸素量と高温曲げ強度との関係が記載されてい
る。この発明は、窒化ケイ素粉末の酸素量を少な
くし高温強度に優れた焼結体を提案しているが、
常圧焼結体の高温曲げ強度をさらに向上させるた
めに粉末の粒度構成特に微粉量をどのようにすべ
きかについては言及していない。
〔発明が解決しようとする課題〕
本発明者らは以上の点について種々検討した結
果、窒化ケイ素粉末の酸素量、比表面積、平均粒
子径及び微粉量が特定範囲にある場合に、常圧焼
結によつても著しい高温強度の改善が可能となる
ことを見い出し本発明を完成した。
〔課題を解決するための手段〕
すなわち、本発明は酸素0.7重量％以下、比表
面積６m2／ｇ以上であり平均粒子径が1μｍ以下
でしかも0.2μｍ以下の微粉が７体積％以下である
ことを特徴とする窒化ケイ素粉末である。
以下、さらに詳しく説明すると、本発明におけ
る窒化ケイ素粉末の酸素は0.7重量％以下好まし
くは0.5重量％以下である。酸素を0.7重量％以下
に限定したのは、それよりも多いと焼結の際に生
じるα−β転移が低温から起こりやすくなり、更
には焼結助剤が形成する粒界相の量が多くなるの
で、窒化ケイ素の溶解性が変化し充分に成長した
アスペクト比の高いβ柱状晶を得ることが困難と
なるからである。また、比表面積を６m2／ｇ以上
に限定したのはそれ未満では焼結しにくく緻密化
不足となるためである。しかしながら、20m2／ｇ
以上の高比表面積になると焼結性はよいが、予備
成型が難しく、焼結収縮が大きい等の欠点が現わ
れるようになる。好ましい比表面積は８〜12m2／
ｇである。
酸素0.7重量％以下、比表面積６m2／ｇ以上の
条件を備えていても焼結体の高温強度が向上しな
いことがある。この原因の１つに、低酸素、低比
表面積に影響すると考えられる密度不足による高
温強度低下を予想したので、このような低酸素、
低比表面積の粉末でも焼結しやすい焼結助剤を用
いてさらに検討を進めたところ、窒化ケイ素粉末
の粒度、特に平均粒子径と微粉量が焼結性及び焼
結体の高温強度に強い影響を及ぼしていることが
わかつた。この点について、定量的な把握を行な
うために、本発明者らは酸素0.7重量％以下、比
表面積６m2／ｇ以上で、平均粒子径及び微粉量の
異なる窒化ケイ素粉末を意図的に種々調整し、そ
の焼結性と焼結体特性を評価した結果、平均粒子
径が1μｍ以下且つ0.2μｍ以下の微粉が７体積％以
下にある窒化ケイ素粉末は焼結性と焼結体の高温
強度が著しくよくなることを見い出したものであ
る。
すなわち、本発明において、窒化ケイ素粉末の
平均粒子径を1μｍ以下に限定したのは、それを
超えると、焼結助剤例えば酸化イツトリウム、酸
化マグネシウム、酸化アルミニウム等と窒化ケイ
素粉末中に含まれる酸素との反応により生じる複
合酸化物への窒化ケイ素の溶解度の低下が起こり
充分に緻密化しなくなるからである。
好ましい平均粒子径は0.8μｍ以下である。ま
た、平均粒子径が1μｍ以下であつても0.2μｍ以下
の微粉量が多くあつては高温強度の発現は認めら
れなかつた。これについて、焼結体の組織と微粉
量との関係を調べてみると、微粉が多くなるにつ
れて焼結体中のβ−柱状晶のアスペクト比が小さ
くなることがわかつた。この原因については、微
粉が多くなるとα−窒化ケイ素の溶解析出におけ
る核の数が多くなり焼結体中のβ−柱状晶のアス
ペクト比が小さくなつたためと理解した。すなわ
ち、高温強度発現にはβ−柱状晶のアスペクト比
が重要な役割を果しており、0.2μｍ以下の微粉
（恐らくは酸素を多く含んだ窒化ケイ素と考えら
れる）がそのβ−柱状晶のアスペクト比に大きく
影響していることを本発明者らは見い出したもの
である。
すなわち、本発明において、0.2μｍ以下の微粉
の含有量を７体積％以下に限定したのは、それを
超えると著しくβ−柱状晶のアスペクト比が小さ
くなり高温強度が低下するからである。微粉は出
来るだけ少ない方が好ましいといえる。なお、
0.2μｍの粒度を選定したのは、現在の測定法の限
界及び管理上の問題からであり、実際は0.1μｍ以
下の超微粉が影響を及ぼしていることも十分に考
えられる。
また、α分率については溶解析出によるβ−柱
状晶が問題となるので無視することはできない
が、従来から、いわれているようなα分率90％以
上なければ高温強度が発現しないというのではな
く65％程度でも十分に高温強度の改善が認められ
た。
本発明の窒化ケイ素粉末の製造方法については
特に限定はないが、酸素、生成粉末の粒度、比表
面積等の特性を自由に調製することができるハロ
ゲン化ケイ素法が最も適している。例えば、種と
してα分率60〜97％で比表面積18m2／ｇ程度の窒
化ケイ素粉末を生成する窒化ケイ素粉末100重量
部あたり７〜12重量部を中間体イミドに添加し、
酸素分圧を10-5atm以下に調節し、温度1500〜
1600℃の条件で結晶化することにより製造するこ
とができる。
また、Siの直接窒化法の粉末であれば例えば電
気化学株式会社製窒化ケイ素粉末「SN−G2」を
窒素雰囲気下で1500〜1750℃で熱処理し分級する
ことにより製造することができる。
〔実施例〕
以下、実施例と比較例をあげてさらに具体的に
説明する。
実施例１〜14、比較例１〜６
四塩化ケイ素とアンモニアをモル比１：６で、
200℃以下の温度で反応させシリコンジイミドと
塩化アンモニウムからなる中間体を合成した。し
かる後、種粉として、α分率が異なる比表面積18
m2／ｇの窒化ケイ素を添加量を変えて添加し、窒
化ケイ素ルツボ内にて窒素ガス流通下500℃に保
持し脱塩化アンモニウム処理を行なつた。
その後、1500℃以上の温度に昇温し、シリコン
ジイミドを分解して窒化ケイ素粉末とするが、そ
の際、種粉の種類（α分率）及び生成窒化ケイ素
100重量部に対する種の添加量（重量部）及び分
解時の雰囲気中の酸素分圧を変化させて、α分
率、比表面積、酸素及び粒度（平均粒子径と微粉
量）の異なる粉末を製造した。第１表にそれらの
粉末特性を示す。
また、電気化学株式会社製窒化ケイ素粉末
［SN−G2］を高温で熱処理する際、その熱処理
温度、加熱時間を変化させて、α分率、比表面
積、酸素及び粒度（平均粒子径、微粉量）の異な
る粉末を製造した。第２表にそれらの粉末特性を
示す。
第１〜２表の各種特性をもつ窒化ケイ素粉末
100重量部に焼結助剤として、Y2O3：Al2O3の重
量比が５：２である混合物を７重量部添加混合
し、3t／cm2の圧力でラバープレス成形した後温度
1800℃×４時間焼結した。得られた焼結体Ａの
JIS Ｒ−1601に従う1200℃における３点曲げ強度
の測定結果を第３表に示す。
また、焼結助剤として、MgO：Al2O3：Y2O3
の重量比が２：５：２である混合物を９重量部添
加し、焼結条件を温度1700℃で４時間としたこと
以外は同様に焼結した。得られた焼結体Ｂの曲げ
強度の測定結果を同じく第３表に示す。
なお、第１表、第２表に示した測定値は次の方
法によつた。
(1) 酸素（重量％）：LECO社製TC−136型Ｏ／
Ｎ同時分析計による。
(2) 比表面積（m2／ｇ）：湯浅アイオニクス社製
のカンターソーブJrBET1点法による。
(3) 粒度（μｍ）：堀場製作所社製CAPA−700に
よる。
(4) α分率（％）：理学電機社製のガイガーフラ
ツクスRAD−Ｂ型のＸ線回折による。
[Industrial Application Field] The present invention relates to a silicon nitride powder that can produce a sintered body with high high-temperature strength. Silicon nitride is used as a high-temperature structural material in gas turbine components, nozzles, bearings, and the like. [Prior Art] Conventionally, as methods for producing silicon nitride powder, (1) metal silicon direct nitriding method, (2) silica reduction nitriding method, and (3) silicon halide method are known. Perhaps because the powders produced by these methods have different manufacturing histories, even if the amount of metal impurities, the amount of oxygen, the particle size, and the specific surface area are similar, the sinterability of the powder and the sintered body after sintering are different. There are large differences in properties such as bending strength. Generally, the powder produced by method (1) is easily sinterable but has low high temperature bending strength, and the powder produced by method (2) is difficult to sinter but has high high temperature bending strength. The powder obtained by method (3) is said to exhibit intermediate performance. Regarding the amount of oxygen, since the powder produced by method (1) undergoes a pulverization process, the total oxygen amount usually exceeds 2% by weight, often at least 1.5% by weight. In method (1), the total amount of oxygen can be reduced by passing through a process such as acid treatment to remove impurities, but it is still difficult to reduce it to less than 1.0% by weight. On the other hand, even in the powder obtained by method (2), since silica powder is used as a raw material, there is residual silica, and the total oxygen content usually exceeds 2% by weight. The above powders are currently available. Of course, the sinterability of the powder and the characteristics of the sintered body are affected by the amount of oxygen in the powder, but there are also other factors such as specific surface area, crystallinity, particle shape, and particle size (fine powder).
Various powder properties such as these are intertwined with each other, and it is currently unclear how the powder properties of each of the above-mentioned manufacturing methods are related to the powder properties. Japanese Patent Publication No. 61-43311 describes the relationship between the oxygen content of silicon nitride powder and high temperature bending strength. This invention proposes a sintered body with excellent high-temperature strength by reducing the amount of oxygen in silicon nitride powder.
There is no mention of how the particle size structure of the powder, particularly the amount of fine powder, should be adjusted in order to further improve the high-temperature bending strength of the pressureless sintered body. [Problems to be Solved by the Invention] As a result of various studies on the above points, the present inventors found that when the oxygen content, specific surface area, average particle size, and fine powder amount of silicon nitride powder are within specific ranges, atmospheric pressure sintering is possible. The present invention was completed by discovering that high-temperature strength can be significantly improved by binding. [Means for Solving the Problems] In other words, the present invention requires that the oxygen content be 0.7% by weight or less, the specific surface area be 6 m 2 /g or more, the average particle size be 1 μm or less, and the amount of fine powder of 0.2 μm or less be 7% by volume or less. It is a silicon nitride powder characterized by: To explain in more detail below, the silicon nitride powder in the present invention has an oxygen content of 0.7% by weight or less, preferably 0.5% by weight or less. The reason why oxygen is limited to 0.7% by weight or less is that if it is more than that, the α-β transition that occurs during sintering will occur more easily at low temperatures, and furthermore, the amount of grain boundary phase formed by the sintering aid will increase. This is because the solubility of silicon nitride changes and it becomes difficult to obtain sufficiently grown β columnar crystals with a high aspect ratio. Further, the specific surface area is limited to 6 m 2 /g or more because if it is less than that, it will be difficult to sinter and result in insufficient densification. However, 20m 2 /g
When the specific surface area is higher than the above, sinterability is good, but disadvantages such as difficulty in preforming and large sintering shrinkage appear. The preferred specific surface area is 8 to 12 m 2 /
It is g. Even if the conditions are such that the oxygen content is 0.7% by weight or less and the specific surface area is 6 m 2 /g or more, the high temperature strength of the sintered body may not be improved. We predicted that one of the causes of this would be a decrease in high-temperature strength due to insufficient density, which is thought to affect low oxygen and low specific surface area.
Further investigation using a sintering aid that makes it easy to sinter even powders with low specific surface areas revealed that the particle size of silicon nitride powder, especially the average particle size and amount of fine particles, are strong in sinterability and high-temperature strength of the sintered body. It turned out that it was having an impact. In order to quantitatively understand this point, the present inventors intentionally prepared various silicon nitride powders with oxygen content of 0.7% by weight or less, specific surface area of 6m 2 /g or more, and different average particle diameters and fine powder amounts. However, as a result of evaluating the sinterability and properties of the sintered compact, silicon nitride powder with an average particle size of 1 μm or less and 7% by volume or less of fine powder of 0.2 μm or less has good sinterability and high-temperature strength of the sintered compact. We have found that it is significantly better. That is, in the present invention, the average particle diameter of the silicon nitride powder is limited to 1 μm or less because, if the average particle diameter exceeds 1 μm, sintering aids such as yttrium oxide, magnesium oxide, aluminum oxide, etc. and oxygen contained in the silicon nitride powder This is because the solubility of silicon nitride in the composite oxide produced by the reaction with the composite oxide decreases, resulting in insufficient densification. The preferred average particle diameter is 0.8 μm or less. Furthermore, even if the average particle diameter was 1 μm or less, no development of high temperature strength was observed when the amount of fine powder of 0.2 μm or less was large. Regarding this, when the relationship between the structure of the sintered body and the amount of fine powder was investigated, it was found that as the amount of fine powder increased, the aspect ratio of the β-columnar crystals in the sintered body became smaller. The reason for this was understood to be that as the amount of fine powder increased, the number of nuclei in the elution and precipitation of α-silicon nitride increased and the aspect ratio of β-columnar crystals in the sintered body became smaller. In other words, the aspect ratio of the β-columnar crystals plays an important role in the development of high-temperature strength, and fine powder of 0.2 μm or less (probably silicon nitride containing a lot of oxygen) has the aspect ratio of the β-columnar crystals. The present inventors have discovered that this has a large influence. That is, in the present invention, the content of fine powder of 0.2 μm or less is limited to 7% by volume or less because if it exceeds this, the aspect ratio of the β-columnar crystals becomes significantly small and the high temperature strength decreases. It can be said that it is preferable that the amount of fine powder is as small as possible. In addition,
The particle size of 0.2 μm was selected because of the limitations of current measurement methods and management issues, and it is quite possible that ultrafine powder of 0.1 μm or less actually has an effect. In addition, the α fraction cannot be ignored because β-columnar crystals due to solution precipitation are a problem, but it is conventionally said that high-temperature strength will not develop unless the α fraction is 90% or more. However, a sufficient improvement in high-temperature strength was observed even at around 65%. Although there are no particular limitations on the method for producing the silicon nitride powder of the present invention, the silicon halide method is most suitable because it allows the characteristics such as oxygen, particle size, and specific surface area of the produced powder to be freely adjusted. For example, adding 7 to 12 parts by weight per 100 parts by weight of silicon nitride powder to produce silicon nitride powder with an α fraction of 60 to 97% and a specific surface area of about 18 m 2 /g as a seed to the intermediate imide,
Adjust the oxygen partial pressure to 10 -5 atm or less, and keep the temperature from 1500 to
It can be produced by crystallizing at 1600°C. In addition, if it is a powder obtained by direct nitriding of Si, it can be produced, for example, by heat treating silicon nitride powder "SN-G2" manufactured by Denki Kagaku Co., Ltd. at 1500 to 1750° C. in a nitrogen atmosphere and classifying it. [Example] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. Examples 1 to 14, Comparative Examples 1 to 6 Silicon tetrachloride and ammonia at a molar ratio of 1:6,
An intermediate consisting of silicon diimide and ammonium chloride was synthesized by reacting at a temperature below 200℃. After that, as a seed powder, specific surface areas with different α fractions18
m 2 /g of silicon nitride was added in varying amounts, and the mixture was kept at 500° C. under nitrogen gas flow in a silicon nitride crucible to perform ammonium dechlorination treatment. After that, the temperature is raised to 1500℃ or higher to decompose the silicon diimide and make it into silicon nitride powder.At this time, the type of seed powder (α fraction)
Powders with different α fractions, specific surface areas, oxygen, and particle sizes (average particle diameter and amount of fine powder) are produced by changing the amount of seeds added (parts by weight) relative to 100 parts by weight and the oxygen partial pressure in the atmosphere during decomposition. did. Table 1 shows their powder properties. In addition, when heat-treating silicon nitride powder [SN-G2] manufactured by Denki Kagaku Co., Ltd. at high temperature, the heat treatment temperature and heating time were changed to determine the α fraction, specific surface area, oxygen, and particle size (average particle diameter, amount of fine powder). ) different powders were produced. Table 2 shows their powder properties. Silicon nitride powder with various properties listed in Tables 1 and 2
7 parts by weight of a mixture with a weight ratio of Y 2 O 3 :Al 2 O 3 of 5:2 was added to 100 parts by weight as a sintering aid, and the mixture was rubber press molded at a pressure of 3 t/cm 2 and then the temperature was increased.
Sintering was performed at 1800°C for 4 hours. The obtained sintered body A
Table 3 shows the measurement results of three-point bending strength at 1200°C according to JIS R-1601. In addition, as a sintering aid, MgO:Al 2 O 3 : Y 2 O 3
Sintering was carried out in the same manner, except that 9 parts by weight of a mixture having a weight ratio of 2:5:2 was added, and the sintering conditions were changed to a temperature of 1700° C. for 4 hours. The measurement results of the bending strength of the obtained sintered body B are also shown in Table 3. The measured values shown in Tables 1 and 2 were determined by the following method. (1) Oxygen (wt%): TC-136 type O/manufactured by LECO
By N simultaneous analyzer. (2) Specific surface area (m 2 /g): Based on the Cantersorb JrBET 1-point method manufactured by Yuasa Ionics. (3) Particle size (μm): Based on CAPA-700 manufactured by Horiba, Ltd. (4) α fraction (%): Based on X-ray diffraction using Geiger flux RAD-B manufactured by Rigaku Corporation.
【表】【table】
【表】【table】
【表】【table】
本発明の窒化ケイ素粉末は、焼結性に優れ、得
られた常圧焼結体の高温曲げ強度は800MPa以上
にすることも可能である。これは焼結体のβ−柱
状晶の発生とその成長に関係する粉体特性を制御
した結果によるものである。
The silicon nitride powder of the present invention has excellent sinterability, and the high-temperature bending strength of the pressureless sintered body obtained can be 800 MPa or more. This is the result of controlling the powder properties related to the generation and growth of β-columnar crystals in the sintered body.
Claims (1)
であり、平均粒子径が1μｍ以下でしかも0.2μｍ以
下の微粉が７体積％以下であることを特徴とする
窒化ケイ素粉末。1. A silicon nitride powder characterized by having oxygen of 0.7% by weight or less, a specific surface area of 6 m 2 /g or more, and 7% by volume or less of fine powder having an average particle size of 1 μm or less and 0.2 μm or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63277360A JPH02124709A (en) | 1988-11-04 | 1988-11-04 | Silicon nitride powder |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63277360A JPH02124709A (en) | 1988-11-04 | 1988-11-04 | Silicon nitride powder |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02124709A JPH02124709A (en) | 1990-05-14 |
| JPH0555444B2 true JPH0555444B2 (en) | 1993-08-17 |
Family
ID=17582441
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63277360A Granted JPH02124709A (en) | 1988-11-04 | 1988-11-04 | Silicon nitride powder |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02124709A (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01197307A (en) * | 1988-02-03 | 1989-08-09 | Japan Metals & Chem Co Ltd | Silicon nitride fine powder having a low oxygen content and its production |
-
1988
- 1988-11-04 JP JP63277360A patent/JPH02124709A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01197307A (en) * | 1988-02-03 | 1989-08-09 | Japan Metals & Chem Co Ltd | Silicon nitride fine powder having a low oxygen content and its production |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02124709A (en) | 1990-05-14 |
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