JP2642429B2 - Silicon nitride sintered body and method for producing the same - Google Patents
Silicon nitride sintered body and method for producing the sameInfo
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- JP2642429B2 JP2642429B2 JP63199709A JP19970988A JP2642429B2 JP 2642429 B2 JP2642429 B2 JP 2642429B2 JP 63199709 A JP63199709 A JP 63199709A JP 19970988 A JP19970988 A JP 19970988A JP 2642429 B2 JP2642429 B2 JP 2642429B2
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Description
（産業上の利用分野） 本発明は、自動車，機械装置，化学装置，宇宙航空機
器などの幅広い分野において使用される各種構造部品の
素材として利用でき、特に優れた高温強度を有するファ
インセラミックス部材を得るのに好適な窒化珪素質焼結
体およびその製造方法に関するものである。 （従来の技術） 窒化珪素を主成分とする窒化珪素質焼結体は、常温お
よび高温で化学的に安定であり、高い機械的強度を有し
ているため、軸受などの摺動部材，ターボチャージャー
ローターなどのエンジン部材として好適な材料である。 しかし、窒化珪素はこれ単独では焼結が困難であるた
め、通常の場合には、窒化珪素にMgO,Al2O3,Y2O3などの
焼結助剤を多量に添加して焼成する方法が用いられてい
る（この種の窒化珪素質焼結体の製造方法としては、特
開昭49−63710号，特開昭54−15916号，特開昭60−1378
73号などに開示された多くのものがある。）。 （発明が解決しようとする課題） しかしながら、上述したように、窒化珪素にMgO,Al2O
3,Y2O3などの焼結助剤を多量に添加して焼成することに
より得られた従来の窒化珪素質焼結体においては、焼結
体中の粒界に低融点のガラス相を有しているため、この
焼結体を素材とする各種構造部品の耐クリープ特性，高
温強度，耐酸化性などの高温特性が低下するという課題
があった。 （発明の目的） 本発明は、上記したような従来の課題に着目してなさ
れたもので、常温のみならずとくに高温における強度特
性に優れており、高温において強度低下の少ない窒化珪
素質焼結体を提供することを目的としている。INDUSTRIAL APPLICABILITY The present invention relates to a fine ceramic member which can be used as a material for various structural parts used in a wide range of fields such as automobiles, mechanical devices, chemical devices, and aerospace equipment, and which has particularly excellent high-temperature strength. The present invention relates to a silicon nitride based sintered body suitable for obtaining and a method for producing the same. (Prior Art) A silicon nitride-based sintered body containing silicon nitride as a main component is chemically stable at normal and high temperatures and has high mechanical strength. It is a suitable material for an engine member such as a charger rotor. However, since silicon nitride alone is difficult to sinter, it is usually fired by adding a large amount of a sintering aid such as MgO, Al 2 O 3 , Y 2 O 3 to silicon nitride. A method of producing such a silicon nitride sintered body is disclosed in JP-A-49-63710, JP-A-54-15916, and JP-A-60-1378.
There are many such as disclosed in No. 73. ). (Problems to be Solved by the Invention) However, as described above, MgO, Al 2 O
3 , In a conventional silicon nitride sintered body obtained by adding a large amount of a sintering aid such as Y 2 O 3 and firing, a low melting point glass phase is formed at the grain boundaries in the sintered body. Therefore, there has been a problem that high-temperature characteristics such as creep resistance, high-temperature strength, and oxidation resistance of various structural components using the sintered body as a material are deteriorated. (Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and has excellent strength characteristics not only at normal temperature but also particularly at high temperature, and has a small decrease in strength at high temperature. It is intended to provide the body.
（課題を解決するための手段） 本発明は、窒化珪素を主成分とする窒化珪素質焼結体
において、２種以上の周期表III a族元素の酸化物を酸
化物換算で１重量％以上４重量％以下含み且つ焼結体中
の酸素含有量が１重量％以下であり、かさ密度が理論密
度の95％以上であり、より望ましくは窒化珪素および焼
結助剤を構成する元素以外の元素の総量が0.5重量％以
下である窒化珪素質焼結体の構成としたことを特徴とし
ており、このような窒化珪素質焼結体を製造するにあた
っては、珪素粉末と酸化物換算で合計で１重量％以上４
重量％以下の２種以上の周期表III a族元素の酸化物を
混合して成形した成形体に窒素雰囲気中で1500℃以下の
温度で珪素残存率が２〜20重量％となる窒化処理を施し
たのち、１気圧以上の窒素雰囲気中で1800〜2200℃の温
度で酸素含有量が１重量％以下で且つかさ密度が理論密
度の95％以上となるまで焼成を行う窒化珪素質焼結体の
製造方法の構成としたことを特徴としており、上記の構
成を前述した従来の課題を解決するための手段としたも
のである。 本発明に係る窒化珪素質焼結体は、上記したように、
２種以上の周期表III a族元素の酸化物を酸化物換算で
１重量％以上４重量％以下含み且つ焼結体中の酸素含有
量が１重量％以下であり、かさ密度が理論密度の95％以
上であることを特徴としているものであるが、この焼結
体中の酸素の存在は、出発原料である珪素粉末中の不純
物シリカ（SiO2）およびこれに添加する酸化物系焼結助
剤に起因する。 そこで、窒化珪素質焼結体中の酸素含有量に着目して
高温特性の向上について種々の検討を積重ねた結果、２
種以上の周期表III a族元素の酸化物を酸化物換算で１
重量％以上４重量％以下含むものにおいて焼結体中の酸
素含有量を１重量％以下とし、焼結体のかさ密度を理論
密度の95％以上とすることによって、耐クリープ特性，
高温強度，耐熱性，耐酸化性などの高温特性に優れた窒
化珪素質焼結体が得られることを新規に発明した。 また、本発明に係る窒化珪素質焼結体においては、窒
化珪素および酸化物系焼結助剤を構成する元素、すなわ
ちSi,Nおよび焼結助剤元素（例えば、周期表III a族元
素）,O以外の元素の総量が0.5重量％以下であるように
することが、高温特性のより一層の向上にとってより望
ましい。ただし、炭化珪素やウイスカなどの窒化珪素と
反応しない物質は焼結体中に0.5重量％を超えて含まれ
ていても差支えない。 本発明に係る窒化珪素質焼結体では、上記した焼結体
中の酸化物含有量，酸素含有量およびかさ密度の条件が
満足されるならば、出発原料，焼結助剤，混合，成形，
焼成などの製造方法に係る条件については、特に問わな
いものであるが、製造方法の一例を述べるならば、前述
したように、珪素粉末と酸化物換算で合計で１重量％以
上４重量％以下の２種以上の周期表III a族元素の酸化
物を混合して成形した成形体に窒素雰囲気中で1500℃以
下の温度で珪素残存率が２〜20重量％となる窒化処理を
施したのち、１気圧以上の窒素雰囲気中で1800〜2200℃
の温度で酸素含有量が１重量％以下で且つかさ密度が理
論密度の95％以上となるまで焼成を行う製造方法を採用
することができる。 ここに述べた製造方法において、出発原料は珪素粉末
と周期表III a族元素の酸化物である。 これらのうち、珪素粉末は、それに含まれる酸素含有
量は少ない方が望ましいが、最初に珪素粉末中に含まれ
ていた酸素は後に行われる窒化処理および焼成時におい
て珪素の酸化物として飛散する部分があるので、出発原
料である珪素粉末中の酸素含有量はとくに限定されず、
より望ましくは４重量％以下のものを用いるのがよい。 他方、同じく出発原料となる酸化物を構成する周期表
III a族元素としては、Sc,Y,ランタノイド（原子番号57
〜71），アクチノイド（原子番号89〜103）などがある
が、通常の場合にはこれらのうちY,La,Nd,Smなどが価
格、入手性あるいは取扱い性の都合などにより使用され
やすい。 そして、珪素粉末に対する上記２種以上の周期表III
a族元素の酸化物の添加量は、焼結体中の酸素含有量が
１重量％以下として高温特性の低下をなくすことができ
るように、上記２種以上の合計で４重量％以下であるよ
うにする。また、焼結助剤の性質から言って当然のこと
ではあるが、この酸化物の量が少なすぎると粒界相の量
が少なくなって破壊靭性が低下する。 かくして、最終焼結体中の酸素含有量が１重量％以下
となるように出発原料である珪素粉末および酸化物の混
合組成を決定し、より望ましくは、Si,III a族元素,O,N
以外の元素の量が0.5重量％以下となるようにする。た
だし、前述したように、炭化珪素やウイスカなどの窒化
珪素と反応しない物質は焼結体中に0.5重量％を超えて
含まれても差支えない。 次に、出発原料である珪素粉末と周期表III a族元素
の酸化物とを混合したのち成形するに際しては、例え
ば、金型プレス成形，ラバープレス成形，射出成形な
ど、通常のセラミックスの成形方法が、目的とする成形
部材の形状等にあわせて選択されるが、特に限定されな
い。 次いで、この成形体に対しては窒素雰囲気中で1500℃
以下の温度で珪素残存率が２〜20重量％となる窒化処理
を施すことによって窒化処理体を得る。この窒化処理に
おいては、珪素と窒素とが反応して窒化珪素が生成す
る。 このとき、酸素含有量をさらに低減させる一手法とし
て、この窒化処理において珪素の窒化を完全に行わず、
窒化処理体中に珪素を残留させる方法を採用することが
望ましく、この場合の珪素の残存率は２〜20重量％とな
るようにすることがとくに望ましい。つまり、珪素の残
存率が２重量％よりも少ないときには酸素含有量の低減
効果が小さく、20重量％を超えると次工程の焼成時に珪
素が溶融するので望ましくなく、珪素が適度に残存して
いる窒化処理体を次工程で焼成すると、 SiO2＋Si→2SiO（ガス） の反応によりSiOが蒸発するため、焼結体中の酸素含有
量が低減したものとなる。 次に、窒化処理を施したあとは、１気圧以上の窒素雰
囲気中で1800〜2200℃の温度でかさ密度が理論密度の95
％以上となるまで焼成を行うが、このとき、雰囲気圧力
が１気圧よりも低いと窒化珪素の分解が激しくなり、緻
密な焼結体が得られなくなるので好ましくない。この窒
化珪素の分解を抑えるのに必要な雰囲気圧力は焼成温度
によって決まり、高温ほど高い圧力が必要となる。ま
た、焼成温度が1800℃よりも低いと十分な量の液相が生
成しないため十分に緻密化せず、2200℃よりも高いと粒
成長が激しくなるため強度が低下するので好ましくな
い。そしてこの焼成は、焼結体中の酸素含有量が１重量
％以下で且つ焼結体のかさ密度が理論密度の95％以上で
ある緻密な焼結体が得られるまで行う。 そして、ここで例示した製造方法により得られた窒化
珪素質焼結体は、酸素含有量が１重量％以下であり、か
さ密度が理論密度の95％以上であって、耐クリープ特
性，高温強度，耐熱性，耐酸化性などの高温特性に著し
く優れたものとなっている。 （発明の作用） 本発明においては、高温における強度低下の防止、高
温特性の改善に、焼結体中の酸素含有量を規制すること
が有効であることを見出し、酸化物系助剤の添加量を特
定すると共にその他の酸素源を少なくすることによって
焼結体中の酸素含有量が少なくなるようにし、出発原料
中の酸素量を少なくしたことによる焼結性の低下は焼結
条件の考慮によって補い、酸素含有量が１重量％以下で
且つかさ密度が理論密度の95％以上となるまで焼成を行
うことによって本発明の目的を達成するものとなる。 （実施例） 実施例１ 平均粒径が20μm,酸素含有量が0.5重量％である珪素
粉末に、1.6重量％の酸化イットリウム（Y2O3）および
1.6重量％の酸化ネオジム（Nd2O3）を添加してエタノー
ル中で24時間ボールミル混合を行い、乾燥した後、20MP
aの圧力で金型成形したあと200MPaの圧力でラバープレ
ス成形して、６×６×50mmの成形体を作製した。 次いで、この成形体を第１図に示す窒化処理スケジュ
ールにより、１気圧の窒素ガス雰囲気下で加熱して窒化
処理を行うことによって、密度2.45g/cm3の窒化処理体
を得た。この窒化処理体中の珪素残存率は5.0重量％で
あった。 次に、この窒化処理体を100気圧の窒素ガス圧下にお
いて2000℃で４時間焼成して焼結体を得た。ここで得ら
れた焼結体の組成は第２表に示すものであってそのかさ
密度は3.18g/cm3であり、これは理論密度（3.23g/cm3）
の98.5％であった。また、焼結体中の酸素含有量は0.80
重量％であった。 ここで得られた焼結体を３×４×40mmの形状にダイヤ
モンドホイールで研削加工し、室温および1400℃で、ス
パン30mmの３点曲げ試験を行った。この結果、５本の平
均値は室温で680MPa,1400℃で650MPaと高温において強
度が低下しない高温特性の優れた焼結体であることが確
められた。 なお、実施例１の内容を第１表および第２表にまとめ
て示す。 比較例１ 平均粒径が１μm,酸素含有量が1.5重量％である窒化
珪素粉末に、1.0重量％の酸化イットリウム（Y2O3）お
よび1.0重量％の酸化ネオジム（Nd2O3）を添加してエタ
ノール中で24時間ボールミル混合を行い、乾燥した後、
20MPaの圧力で金型成形したあと200MPaの圧力でラバー
プレス成形して、６×６×50mmの成形体を作製した。 次に、この成形体を100気圧の窒素ガス圧下において2
000℃で４時間焼成して焼結体を得た。ここで得られた
焼結体の組成は第２表に示すものであってそのかさ密度
は3.12g/cm3であり、これは理論密度（3.22g/cm3）の9
6.9％であった。また、焼結体中の酸素含有量は1.68重
量％であった。 ここで得られた焼結体を３×４×40mmの形状にダイヤ
モンドホイールで研削加工し、室温および1400℃で、ス
パン30mmの３点曲げ試験を行った。この結果、５本の平
均値は室温で550MPa,1400℃で230MPaと高温において強
度が著しく低下していることが確められた。 なお、比較例１の内容を第１表および第２表にまとめ
て示す。 実施例2,3,4,5 平均粒径が20μm,酸素含有量が0.5重量％である珪素
粉末に、第１表の実施例2,3,4,5の各欄に示す酸化物系
焼結助剤を添加してエタノール中で24時間ボールミル混
合を行い、乾燥した後、20MPaの圧力で金型成形したあ
と200MPaの圧力でラバープレス成形して、６×６×50mm
の各成形体を作製した。 次いで、各成形体を第１図に示す窒化処理スケジュー
ルにより、１気圧の窒素ガス雰囲気下で加熱して窒化処
理を行うことにより窒化処理体を得た。ここで得られた
各窒化処理体中の珪素残存率は、同じく第１表の実施例
2,3,4,5の各欄に示す値であった。 次に、各窒化処理体を50気圧の窒素ガス圧下において
1900℃で４時間焼成して各焼結体を得た。ここで得られ
た各焼結体の組成および理論密度に対するかさ密度の比
は第２表の実施例2,3,4,5の各欄に示す値となってお
り、いずれも95％以上に緻密化しているものであった。
また、各焼結体中の酸素含有量は同じく第２表の実施例
2,3,4,5の各欄に示すとおりいずれも1.0重量％以下であ
った。 ここで得られた各焼結体を３×４×40mmの形状にダイ
ヤモンドホイールで研削加工し、室温および1400℃で、
スパン30mmの３点曲げ試験を行った。この結果は同じく
第２表の実施例2,3,4,5の各欄に示すように、室温での
強度が高いだけでなく、とくに高温において強度が低下
しない高温特性の優れた焼結体であることが確められ
た。 比較例2,3,4 平均粒径が20μm,酸素含有量が0.5重量％である珪素
粉末に、第１表の比較例2,3,4の各欄に示す酸化物系焼
結助剤を添加してエタノール中で24時間ボールミル混合
を行い、乾燥した後、20MPaの圧力で金型成形したあと2
00MPaの圧力でラバープレス成形して、６×６×50mmの
各成形体を作製した。 次いで、各成形体を第１図に示す窒化処理スケジュー
ルにより、１気圧の窒素ガス雰囲気下で加熱して窒化処
理を行うことにより窒化処理体を得た。ここで得られた
各窒化処理体中の珪素残存率は、同じく第１表の比較例
2,3,4の各欄に示す値であった。 次に、各窒化処理体を50気圧の窒素ガス圧下において
1900℃で４時間焼成して各焼結体を得た。ここで得られ
た各焼結体の組成および理論密度に対するかさ密度の比
は第２表の比較例2,3,4の各欄に示す値となっており、
いずれも緻密化しているものであった。また、各焼結体
中の酸素含有量は同じく第２表の比較例2,3,4の各欄に
示すとおりいずれも1.0重量％を超えるものであった。 ここで得られた各焼結体を３×４×40mmの形状にダイ
ヤモンドホイールで研削加工し、室温および1400℃で、
スパン30mmの３点曲げ試験を行った。この結果は同じく
第２表の比較例2,3,4の各欄に示すように、室温での強
度は高い値を示しているものの、焼結体中の酸素含有量
が多いため高温での強度低下が激しくなり、とくに周期
表III a族以外の元素の酸化物であるAl2O3を添加した比
較例４において高温での強度低下の著しいことが確めら
れた。 (Means for Solving the Problems) The present invention provides a silicon nitride-based sintered body containing silicon nitride as a main component, wherein at least 1% by weight of oxides of Group IIIa elements in the periodic table is converted to oxides. 4% by weight or less and the oxygen content in the sintered body is 1% by weight or less, and the bulk density is 95% or more of the theoretical density, more preferably silicon nitride and elements other than those constituting the sintering aid. It is characterized in that the silicon nitride-based sintered body has a configuration in which the total amount of elements is 0.5% by weight or less. In manufacturing such a silicon nitride-based sintered body, a total of silicon powder and oxide in terms of oxide is used. 1% by weight or more 4
In a nitrogen atmosphere, a nitriding treatment is carried out in a nitrogen atmosphere at a temperature of 1500 ° C. or less at a temperature of 1500 ° C. or less so that the silicon residual ratio becomes 2 to 20% by weight. Silicon nitride sintered body that is fired in a nitrogen atmosphere of 1 atm or more at a temperature of 1800 to 2200 ° C. until the oxygen content is 1% by weight or less and the bulk density becomes 95% or more of the theoretical density. The present invention is characterized in that the above-mentioned configuration is used as means for solving the above-mentioned conventional problems. The silicon nitride sintered body according to the present invention, as described above,
The sintered body contains two or more oxides of Group IIIa elements in an amount of 1% by weight or more and 4% by weight or less in terms of oxides, the oxygen content in the sintered body is 1% by weight or less, and the bulk density is the theoretical density. Although it is characterized by being 95% or more, the presence of oxygen in this sintered body is due to the impurity silica (SiO 2 ) in the silicon powder as a starting material and the oxide-based sintering added thereto. Due to auxiliaries. Therefore, various studies were conducted on the improvement of high-temperature characteristics by focusing on the oxygen content in the silicon nitride sintered body.
More than one kind of Periodic Table III
By setting the oxygen content in the sintered body to 1% by weight or less and the bulk density of the sintered body to 95% or more of the theoretical density in those containing from 4% by weight to 4% by weight,
It has been newly invented that a silicon nitride based sintered body having excellent high temperature properties such as high temperature strength, heat resistance and oxidation resistance can be obtained. Further, in the silicon nitride-based sintered body according to the present invention, elements constituting silicon nitride and an oxide-based sintering aid, that is, Si, N and a sintering aid element (for example, Group IIIa element of the periodic table) It is more desirable for the total amount of elements other than O and O to be 0.5% by weight or less for further improvement in high-temperature characteristics. However, substances that do not react with silicon nitride, such as silicon carbide and whiskers, may be contained in the sintered body in an amount exceeding 0.5% by weight. In the silicon nitride based sintered body according to the present invention, the starting material, sintering aid, mixing, and molding are performed as long as the conditions of the oxide content, oxygen content, and bulk density in the sintered body are satisfied. ,
Conditions relating to the manufacturing method such as firing are not particularly limited. However, if an example of the manufacturing method is described, as described above, a total of 1% by weight to 4% by weight in terms of silicon powder and oxide is used. The molded body formed by mixing and mixing two or more kinds of oxides of Group IIIa elements in the periodic table is subjected to a nitriding treatment in a nitrogen atmosphere at a temperature of 1500 ° C. or less at a silicon residual ratio of 2 to 20% by weight. 1800-2200 ℃ in nitrogen atmosphere of 1 atm or more
At this temperature, a production method can be employed in which firing is performed until the oxygen content is 1% by weight or less and the bulk density becomes 95% or more of the theoretical density. In the production method described herein, the starting materials are silicon powder and an oxide of a Group IIIa element in the periodic table. Of these, silicon powder desirably has a low oxygen content, but the oxygen initially contained in the silicon powder is scattered as silicon oxide during the subsequent nitriding and firing. Therefore, the oxygen content in the starting material silicon powder is not particularly limited,
It is more preferable to use one having a content of 4% by weight or less. On the other hand, the periodic table that also constitutes the starting material oxide
III As Group a elements, Sc, Y, lanthanoids (atomic number 57
To 71) and actinoids (atomic numbers 89 to 103). Of these, Y, La, Nd, Sm and the like are usually easily used due to the price, availability, handling convenience, and the like. And the above-mentioned two or more kinds of periodic table III for silicon powder
The addition amount of the oxide of the group a element is 4% by weight or less in total of the two or more kinds so that the oxygen content in the sintered body is 1% by weight or less and deterioration of high-temperature characteristics can be prevented. To do. Also, as a matter of course, from the nature of the sintering aid, if the amount of this oxide is too small, the amount of the grain boundary phase will decrease, and the fracture toughness will decrease. Thus, the mixed composition of the silicon powder and the oxide as starting materials is determined so that the oxygen content in the final sintered body is 1% by weight or less. More preferably, the Si, IIIa group element, O, N
The amount of other elements is set to 0.5% by weight or less. However, as described above, substances that do not react with silicon nitride, such as silicon carbide and whiskers, may be contained in the sintered body in an amount exceeding 0.5% by weight. Next, when the silicon powder as a starting material is mixed with an oxide of a Group IIIa element of the periodic table and then molded, for example, a conventional ceramic molding method such as die press molding, rubber press molding, or injection molding is used. Is selected according to the desired shape of the molded member, but is not particularly limited. Next, the molded body is heated at 1500 ° C. in a nitrogen atmosphere.
A nitriding treatment is performed at the following temperature so that the residual silicon ratio becomes 2 to 20% by weight to obtain a nitriding body. In this nitriding treatment, silicon reacts with nitrogen to produce silicon nitride. At this time, as one method for further reducing the oxygen content, in this nitriding treatment, silicon is not completely nitrided,
It is desirable to adopt a method of leaving silicon in the nitrided body, and in this case, it is particularly desirable that the residual ratio of silicon be 2 to 20% by weight. In other words, when the residual ratio of silicon is less than 2% by weight, the effect of reducing the oxygen content is small, and when it exceeds 20% by weight, silicon melts at the time of firing in the next step. When the nitrided body is fired in the next step, the SiO 2 evaporates due to the reaction of SiO 2 + Si → 2SiO (gas), so that the oxygen content in the sintered body is reduced. Next, after the nitriding treatment, the bulk density is 95% of the theoretical density at a temperature of 1800 to 2200 ° C. in a nitrogen atmosphere of 1 atm or more.
%. At this time, if the atmospheric pressure is lower than 1 atm, the decomposition of silicon nitride becomes severe and a dense sintered body cannot be obtained, which is not preferable. The atmospheric pressure required to suppress the decomposition of silicon nitride is determined by the firing temperature, and the higher the temperature, the higher the pressure. On the other hand, if the firing temperature is lower than 1800 ° C., a sufficient amount of the liquid phase is not generated, so that sufficient densification is not achieved. This firing is performed until a dense sintered body having an oxygen content of 1% by weight or less and a bulk density of 95% or more of the theoretical density is obtained. The silicon nitride sintered body obtained by the manufacturing method exemplified here has an oxygen content of 1% by weight or less, a bulk density of 95% or more of the theoretical density, a creep resistance property, and a high temperature strength. It has remarkably excellent high temperature characteristics such as heat resistance, oxidation resistance and the like. (Effect of the Invention) In the present invention, it has been found that it is effective to control the oxygen content in the sintered body to prevent a decrease in strength at high temperatures and to improve high-temperature characteristics. Reduce the oxygen content in the sintered body by specifying the amount and reducing the amount of other oxygen sources, and consider the sintering conditions by reducing the amount of oxygen in the starting material. The object of the present invention is achieved by performing calcination until the oxygen content is 1% by weight or less and the bulk density becomes 95% or more of the theoretical density. Example 1 Example 1 1.6% by weight of yttrium oxide (Y 2 O 3 ) was added to silicon powder having an average particle size of 20 μm and an oxygen content of 0.5% by weight.
After adding 1.6% by weight of neodymium oxide (Nd 2 O 3 ) and performing ball mill mixing in ethanol for 24 hours, and drying,
Molding was performed at a pressure of a, and then rubber press molding was performed at a pressure of 200 MPa to produce a molded body of 6 × 6 × 50 mm. Next, the compact was heated under a nitrogen gas atmosphere at 1 atm according to the nitriding treatment schedule shown in FIG. 1 to perform a nitriding treatment, thereby obtaining a nitrided body having a density of 2.45 g / cm 3 . The residual silicon ratio in this nitrided product was 5.0% by weight. Next, the nitrided body was fired at 2000 ° C. for 4 hours under a nitrogen gas pressure of 100 atm to obtain a sintered body. Here the composition of the obtained sintered body thereof bulk density there is shown in Table 2 is 3.18 g / cm 3, which is the theoretical density (3.23g / cm 3)
98.5% of the total. The oxygen content in the sintered body was 0.80
% By weight. The sintered body obtained here was ground by a diamond wheel into a shape of 3 × 4 × 40 mm and subjected to a three-point bending test with a span of 30 mm at room temperature and 1400 ° C. As a result, it was confirmed that the average value of the five samples was 680 MPa at room temperature and 650 MPa at 1400 ° C., indicating that the sintered body was excellent in high-temperature characteristics and did not decrease in strength at high temperatures. Table 1 and Table 2 summarize the contents of Example 1. Comparative Example 1 1.0% by weight of yttrium oxide (Y 2 O 3 ) and 1.0% by weight of neodymium oxide (Nd 2 O 3 ) were added to silicon nitride powder having an average particle size of 1 μm and an oxygen content of 1.5% by weight. Performed ball mill mixing in ethanol for 24 hours, dried,
Molding was performed at a pressure of 20 MPa, and then rubber press molding was performed at a pressure of 200 MPa to produce a molded body of 6 × 6 × 50 mm. Next, the molded body was subjected to nitrogen gas pressure of 100 atm.
It was fired at 000 ° C. for 4 hours to obtain a sintered body. Its bulk density composition of the sintered body obtained herein, there is shown in Table 2 is 3.12 g / cm 3, which is the theoretical density of (3.22g / cm 3) 9
It was 6.9%. Further, the oxygen content in the sintered body was 1.68% by weight. The sintered body obtained here was ground by a diamond wheel into a shape of 3 × 4 × 40 mm and subjected to a three-point bending test with a span of 30 mm at room temperature and 1400 ° C. As a result, it was confirmed that the average value of the five wires was 550 MPa at room temperature and 230 MPa at 1400 ° C., indicating that the strength was significantly reduced at high temperatures. The contents of Comparative Example 1 are summarized in Tables 1 and 2. Examples 2, 3, 4, 5 Oxide-based powders shown in the columns of Examples 2, 3, 4, and 5 in Table 1 were added to silicon powder having an average particle size of 20 µm and an oxygen content of 0.5% by weight. After adding a binder and mixing in a ball mill in ethanol for 24 hours, drying, molding in a mold at a pressure of 20 MPa, followed by rubber press molding at a pressure of 200 MPa, 6 × 6 × 50 mm
Were produced. Next, each compact was heated under a nitrogen gas atmosphere at 1 atm according to the nitridation treatment schedule shown in FIG. The silicon residual ratio in each of the nitrided bodies obtained here is the same as in Example 1 in Table 1.
The values were shown in the columns 2, 3, 4, and 5. Next, each nitrided body is placed under a nitrogen gas pressure of 50 atm.
Each sintered body was obtained by firing at 1900 ° C. for 4 hours. The ratio of the bulk density to the composition and the theoretical density of each sintered body obtained here is the value shown in each column of Examples 2, 3, 4, and 5 in Table 2, and all of them are 95% or more. It was a dense one.
Also, the oxygen content in each sintered body is the same as in Example 2 in Table 2.
As shown in the columns 2, 3, 4, and 5, all were 1.0% by weight or less. Each sintered body obtained here was ground to a shape of 3 × 4 × 40 mm with a diamond wheel, and at room temperature and 1400 ° C.,
A three-point bending test with a span of 30 mm was performed. As shown in the columns of Examples 2, 3, 4, and 5 in Table 2, the results show that the sintered body not only has a high strength at room temperature but also has excellent high-temperature characteristics in which the strength does not decrease particularly at high temperatures. Was confirmed. Comparative Examples 2, 3, and 4 Oxide-based sintering aids shown in each column of Comparative Examples 2, 3, and 4 in Table 1 were added to a silicon powder having an average particle size of 20 μm and an oxygen content of 0.5% by weight. After adding and mixing in a ball mill for 24 hours in ethanol, drying, and then molding at a pressure of 20 MPa, 2
Rubber press molding was performed under a pressure of 00 MPa to produce each molded body of 6 × 6 × 50 mm. Next, each compact was heated under a nitrogen gas atmosphere at 1 atm according to the nitridation treatment schedule shown in FIG. The silicon residual ratio in each nitrided body obtained here is the same as in Comparative Example 1 in Table 1.
The values shown in the respective columns 2, 3, and 4. Next, each nitrided body is placed under a nitrogen gas pressure of 50 atm.
Each sintered body was obtained by firing at 1900 ° C. for 4 hours. The ratio of the bulk density to the composition and theoretical density of each sintered body obtained here is the value shown in each column of Comparative Examples 2, 3, and 4 in Table 2.
All were dense. Further, the oxygen content in each sintered body also exceeded 1.0% by weight, as shown in each column of Comparative Examples 2, 3, and 4 in Table 2. Each sintered body obtained here was ground to a shape of 3 × 4 × 40 mm with a diamond wheel, and at room temperature and 1400 ° C.,
A three-point bending test with a span of 30 mm was performed. As shown in the columns of Comparative Examples 2, 3, and 4 in Table 2, the results show that although the strength at room temperature shows a high value, the oxygen content in the sintered body is large, It was confirmed that the strength was drastically lowered, and particularly in Comparative Example 4 in which Al 2 O 3 which was an oxide of an element other than Group IIIa was added, the strength was significantly lowered at a high temperature.
以上説明してきたように、本発明に係る窒化珪素質焼
結体およびその製造方法によれば、焼結体中に２種以上
の周期表III a族元素の酸化物を酸化物換算で１重量％
以上４重量％以下含み且つ焼結体中の酸素含有量が１重
量％以下、かさ密度が理論密度の95％以上の窒化珪素質
焼結体となっているものであるから、焼結性が良好であ
って、常温強度に優れているのみならず、高温における
強度の低下が著しく少なく、耐クリープ特性，高温強
度，耐熱性，耐酸化性などの高温特性に優れたファイン
セラミックス材料であり、高温で使用される各種構造部
品の素材として好適なものであり、これら各種構造部品
の軽量化に大きく貢献するものであるという非常に優れ
た効果がもたらされる。As described above, according to the silicon nitride-based sintered body and the method of manufacturing the same according to the present invention, two or more oxides of Group IIIa elements in the periodic table are contained in the sintered body in an amount of 1 wt. %
This is a silicon nitride-based sintered body containing not less than 4% by weight and having an oxygen content of 1% by weight or less and a bulk density of 95% or more of the theoretical density. It is a fine ceramic material that is not only excellent in room temperature strength but also has extremely low strength reduction at high temperature, and has excellent high temperature properties such as creep resistance, high temperature strength, heat resistance and oxidation resistance. It is suitable as a material for various structural parts used at high temperatures, and has an extremely excellent effect of greatly contributing to weight reduction of these various structural parts.
第１図は本発明の実施例および比較例（ただし、比較例
１を除く）において採用した窒化処理スケジュールを示
す説明図である。FIG. 1 is an explanatory diagram showing a nitriding treatment schedule adopted in Examples of the present invention and Comparative Examples (excluding Comparative Example 1).
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭62−207767（ＪＰ，Ａ) 特開 昭62−132775（ＪＰ，Ａ) 特開 昭56−22678（ＪＰ，Ａ) 特開 平１−252581（ＪＰ，Ａ) ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-207767 (JP, A) JP-A-62-132775 (JP, A) JP-A-56-22678 (JP, A) JP-A-1- 252581 (JP, A)
Claims (4)
において、２種以上の周期表III a族元素の酸化物を酸
化物換算で１重量％以上４重量％以下含み且つ焼結体中
の酸素含有量が１重量％以下であり、かさ密度が理論密
度の95％以上であることを特徴とする窒化珪素質焼結
体。1. A silicon nitride-based sintered body containing silicon nitride as a main component, comprising two or more oxides of a Group IIIa element in the periodic table in an amount of 1% by weight to 4% by weight in terms of oxide and sintered. A silicon nitride sintered body characterized in that the oxygen content in the body is 1% by weight or less and the bulk density is 95% or more of the theoretical density.
において、イットリウムとネオジム、イットリウムとサ
マリウム、イットリウムとデスプロシウムのうち少なく
ともいずれかの組み合わせから選ばれる２種以上の周期
表III a族元素の酸化物を酸化物換算で１重量％以上４
重量％以下含み且つ焼結体中の酸素含有量が１重量％以
下であり、かさ密度が理論密度の95％以上であることを
特徴とする請求項１に記載の窒化珪素質焼結体。2. In the silicon nitride sintered body containing silicon nitride as a main component, two or more kinds of periodic table group IIIa selected from a combination of at least one of yttrium and neodymium, yttrium and samarium, yttrium and desprosium. 1% by weight or more of oxide of element
2. The silicon nitride-based sintered body according to claim 1, wherein the sintered body contains not more than 1% by weight, the oxygen content in the sintered body is 1% by weight or less, and the bulk density is 95% or more of the theoretical density.
上４重量％以下の２種以上の周期表III a族元素の酸化
物を混合して成形した成形体に窒素雰囲気中で1500℃以
下の温度で珪素残存率が２〜20重量％となる窒化処理を
施したのち、１気圧以上の窒素雰囲気中で1800〜2200℃
の温度で酸素含有量が１重量％以下で且つかさ密度が理
論密度の95％以上となるまで焼成を行うことを特徴とす
る窒化珪素質焼結体の製造方法。3. A compact formed by mixing silicon powder and two or more oxides of Group IIIa elements of the periodic table in a total of 1% by weight or more and 4% by weight or less in terms of oxide in a nitrogen atmosphere for 1500 minutes. After performing nitriding treatment at a temperature of not more than 1 ° C so that the residual silicon ratio becomes 2 to 20% by weight, 1800 to 2200 ° C in a nitrogen atmosphere of 1 atm or more
A method for producing a silicon nitride-based sintered body, characterized in that the sintering is carried out at a temperature of not more than 1% by weight and the bulk density is not less than 95% of the theoretical density.
上４重量％以下のイットリウムとネオジム、イットリウ
ムとサマリウム、イットリウムとデスプロシウムのうち
少なくともいずれかの組み合わせから選ばれる２種以上
の周期表III a族元素の酸化物を混合して成形した成形
体に窒素雰囲気中で1500℃以下の温度で珪素残存率が２
〜20重量％となる窒化処理を施したのち、１気圧以上の
窒素雰囲気中で1800〜2200℃の温度で酸素含有量が１重
量％以下で且つかさ密度が理論密度の95％以上となるま
で焼成を行うことを特徴とする請求項３に記載の窒化珪
素質焼結体の製造方法。4. A periodic table of at least two selected from a combination of at least one of yttrium and neodymium; yttrium and samarium; III In a nitrogen atmosphere, a molded body formed by mixing an oxide of a Group IIIa element has a silicon residual ratio of 2 at a temperature of 1500 ° C or less.
After performing nitriding treatment of up to 20% by weight, at a temperature of 1800 to 2200 ° C in a nitrogen atmosphere of 1 atm or more, until the oxygen content is 1% by weight or less and the bulk density becomes 95% or more of the theoretical density. The method for producing a silicon nitride-based sintered body according to claim 3, wherein firing is performed.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63199709A JP2642429B2 (en) | 1988-08-09 | 1988-08-09 | Silicon nitride sintered body and method for producing the same |
| US07/707,995 US5126294A (en) | 1988-08-09 | 1991-05-23 | Sintered silicon nitride and production method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63199709A JP2642429B2 (en) | 1988-08-09 | 1988-08-09 | Silicon nitride sintered body and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0248468A JPH0248468A (en) | 1990-02-19 |
| JP2642429B2 true JP2642429B2 (en) | 1997-08-20 |
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ID=16412305
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|---|---|---|---|
| JP63199709A Expired - Fee Related JP2642429B2 (en) | 1988-08-09 | 1988-08-09 | Silicon nitride sintered body and method for producing the same |
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| JP (1) | JP2642429B2 (en) |
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| US5928601A (en) * | 1994-02-28 | 1999-07-27 | Honda Giken Kogyo Kabushiki Kaisha | Method for producing silicon nitride reaction sintered body |
| CA2116644A1 (en) * | 1994-02-28 | 1995-08-29 | Yasunobu Kawakami | Silicon nitride reaction-sintered body and method and apparatus for producing same |
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|---|---|---|---|---|
| JPS5622678A (en) * | 1979-07-28 | 1981-03-03 | Ngk Spark Plug Co | Manufacture of high tenacity silicon nitride sintered body |
| JPS62132775A (en) * | 1985-12-06 | 1987-06-16 | 工業技術院長 | Manufacture of silicon nitride sintered body |
| JPS62207757A (en) * | 1986-03-04 | 1987-09-12 | ハリマセラミック株式会社 | Manufacture of chromium oxide-containing fine refractories |
| JPS62207767A (en) * | 1986-03-06 | 1987-09-12 | 工業技術院長 | High temperature high strength silicon nitride ceramics and manufacture |
| JPH01252581A (en) * | 1988-03-31 | 1989-10-09 | Taiyo Yuden Co Ltd | Production of nitride ceramics |
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