JP2635695B2 - Method for producing α-silicon nitride powder - Google Patents

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明はα−窒化ケイ素粉末の製造方法に関する。The present invention relates to a method for producing α-silicon nitride powder.

窒化ケイ素粉末は、高強度、耐摩耗性を必要とする治
工具類（切削工具、ダイス、抽伸プラグ等）、産業機械
部品（メカニカルシール、ポンプ部品等）及び耐熱構造
部材（タービン、エンジン部品等）等の用途に利用され
ている。Silicon nitride powder is used for jigs and tools that require high strength and wear resistance (cutting tools, dies, drawing plugs, etc.), industrial machine parts (mechanical seals, pump parts, etc.) and heat-resistant structural members (turbines, engine parts, etc.) )).

〔従来の技術〕[Conventional technology]

従来、高α化率、高純度かつ結晶形状と大きさの一定
した高品質の結晶質窒化ケイ素を得る方法として、含窒
素シラン化合物及び／又は非晶質窒化ケイ素に高α化率
の結晶質窒化ケイ素を種として添加する技術が知られて
いる（特公昭62−59050号公報）。この方法によれば、
針状晶を含まず、適当な比表面積をもつたα化率90％以
上の窒化ケイ素粉末の合成が可能である。一般的には、
高α化率なもの程、焼結工程でのβ−柱状晶の生成には
良いといわれているが、窒化ケイ素の高α化率と窒化ケ
イ素焼結体の高強度等の特性との関係についてはよく判
つておらず、現在、高温構造材料に要求されている充分
な高温強度例えば1200℃の曲げ強度600MPa以上は得られ
ていない。Conventionally, as a method of obtaining high-quality crystalline silicon nitride having a high α-rate, high purity, and a uniform crystal shape and size, a nitrogen-containing silane compound and / or amorphous silicon nitride have a high α-rate crystalline material. A technique of adding silicon nitride as a seed is known (JP-B-62-59050). According to this method,
It is possible to synthesize a silicon nitride powder having an appropriate specific surface area and having a pregelatinization ratio of 90% or more without containing needle-like crystals. In general,
It is said that the higher the α-rate, the better the formation of β-columnar crystals in the sintering process, but the relationship between the high α-rate of silicon nitride and the properties such as the high strength of the silicon nitride sintered body. However, at present, sufficient high-temperature strength required for high-temperature structural materials, for example, bending strength at 1200 ° C. of 600 MPa or more has not been obtained.

〔発明が解決しようとする課題〕[Problems to be solved by the invention]

本発明者は、従来技術における問題点、即ち焼結過程
に於ける緻密化、α−β転移挙動等について、窒化ケイ
素粉末の合成条件を種々変更して得られた各種粉末を用
いて検討した結果、焼結特性及び焼結体特性を向上せし
めるには、焼結体組織に於けるβ−柱状晶の制御が重要
な役割を果しており、それは、合成工程で添加したβ−
窒化ケイ素とα−窒化ケイ素とからなる種にもとづいて
いることを見い出し、本発明を完成したものである。The present inventor studied the problems in the prior art, that is, densification in the sintering process, α-β transition behavior, etc., using various powders obtained by variously changing the synthesis conditions of the silicon nitride powder. As a result, the control of β-columnar crystals in the structure of the sintered body plays an important role in improving the sintering characteristics and the characteristics of the sintered body.
The present invention has been completed based on a species comprising silicon nitride and α-silicon nitride, and the present invention has been completed.

〔課題を解決するための手段〕[Means for solving the problem]

すなわち、本発明は、含窒素シラン化合物及び／又は
非晶質窒化ケイ素を原料とし、この原料に、比表面積10
〜20m²/gでFe、Al、Ca及びMgの合計が1000ppm以下のβ
−窒化ケイ素とα−窒化ケイ素とを、前記原料から生成
される理論窒化ケイ素に対して合計２〜10重量％かつβ
−窒化ケイ素0.3〜３重量％の割合として添加し、次い
でそれを非酸化性雰囲気下において加熱結晶化すること
を特徴とするα−窒化ケイ素粉末の製造方法である。That is, the present invention uses a nitrogen-containing silane compound and / or amorphous silicon nitride as a raw material,
Β of not more than 1000 ppm of Fe, Al, Ca and Mg at 2020 m ² / g
-Silicon nitride and α-silicon nitride in a total of 2 to 10% by weight based on theoretical silicon nitride produced from the raw material and β
-A method for producing α-silicon nitride powder, characterized by adding silicon nitride in a ratio of 0.3 to 3% by weight and then heating and crystallizing it in a non-oxidizing atmosphere.

以下、さらに詳しく本発明について説明する。 Hereinafter, the present invention will be described in more detail.

先ず、含窒素シラン化合物及び／又は非晶質窒化ケイ
素原料、例えばハロゲン化ケイ素、モノシランガス等と
アンモニアガスを気相で反応させて得られた原料に、そ
の原料から生成する理論窒化ケイ素に対して、それぞれ
比表面積が10〜20m²/gでかつFe、Al、Ca及びMgの合計
（以下金属不純物という）が1000ppm以下のβ−窒化ケ
イ素とα−窒化ケイ素とを種として合計で内割２〜10重
量％好ましくは４〜７重量％でかつβ−窒化ケイ素0.3
〜３重量％好ましくは0.4〜1.2重量％の割合で添加す
る。β−窒化ケイ素のβ化率は80％以上特に90％以上が
望ましく、またα−窒化ケイ素のα化率は80％以上特に
90％以上が望ましい。First, a raw material obtained by reacting a nitrogen-containing silane compound and / or an amorphous silicon nitride raw material, for example, a silicon halide, a monosilane gas or the like with an ammonia gas in a gas phase, and a theoretical silicon nitride generated from the raw material. And β-silicon nitride and α-silicon nitride each having a specific surface area of 10 to 20 m ² / g and a total of Fe, Al, Ca and Mg (hereinafter referred to as metal impurities) of 1000 ppm or less as a seed, -10% by weight, preferably 4-7% by weight, and β-silicon nitride 0.3
To 3% by weight, preferably 0.4 to 1.2% by weight. The β conversion of β-silicon nitride is preferably 80% or more, more preferably 90% or more, and the α conversion of α-silicon nitride is 80% or more, particularly
90% or more is desirable.

ここで、種として混合するβ−窒化ケイ素とα−窒化
ケイ素の比表面積を10〜20m²/gに限定した理由は、10m²
/g未満になると熱分解して生じる窒化ケイ素自身の粒子
が大きくなつて焼結特性及び焼結体特性の向上は期待で
きず、一方、20m²/gを越えると生成する窒化ケイ素が微
粉末になり過ぎて取扱い性と成形性が悪くなるからであ
る。また金属不純物を1000ppm以下に限定した理由は、1
000ppmを越えると粒界相中の金属不純物の濃縮に起因す
ると推定される高温強度の劣化が起こる。Here, the reason for limiting the specific surface area of the mixed β- silicon nitride and α- silicon nitride as a seed to 10 to 20 m ² / g is, 10 m ²
/ less than g, the improvement of the thermal decomposition larger particles of silicon nitride itself occurs by Do connexion sintering properties and sintered properties can not be expected, while the silicon nitride fine powder to produce when it exceeds 20 m ² / g This is because handleability and moldability become too poor. The reason for limiting metal impurities to 1000 ppm or less is as follows.
If it exceeds 000 ppm, deterioration of high-temperature strength presumably due to concentration of metal impurities in the grain boundary phase occurs.

さらに本発明において、種の添加量をβ−窒化ケイ素
とα−窒化ケイ素の合計で２〜10重量％とした理由は、
２重量％未満であると熱分解して生じる窒化ケイ素自身
の粒子が大きくなつて焼結特性及び焼結体特性の向上は
望めず、一方、10重量％を越えると生成する窒化ケイ素
が微粉末になり過ぎて取扱い性と成形性が悪くなり、ま
た経済的にも不利となるからである。さらにその際、β
−窒化ケイ素量を0.3〜３重量％としたのは、0.3重量％
未満では粒界相よりβ−柱状晶が析出する際の核の数が
不足し、その結果、不均一なβ−柱状晶となり焼結特性
と焼結体特性を向上させることができず、一方、３重量
％を越えると、生成するα−窒化ケイ素のα化率が低下
し、さらには焼結時の核の数の増加に伴い焼結体組織に
おけるβ−柱状晶の微細化が起こり焼結体特性が向上し
なくなるからである。Furthermore, in the present invention, the reason why the amount of the seed added is 2 to 10% by weight in total of β-silicon nitride and α-silicon nitride,
If the content is less than 2% by weight, the particles of silicon nitride generated by thermal decomposition become large, so that the improvement of the sintering characteristics and the characteristics of the sintered body cannot be expected. This is because handling becomes too poor and moldability deteriorates, and it is economically disadvantageous. In that case, β
The reason why the amount of silicon nitride is 0.3 to 3% by weight is that 0.3% by weight is used.
If less than the number of nuclei at the time of precipitation of β-columnar crystals from the grain boundary phase is insufficient, as a result, non-uniform β-columnar crystals will not be able to improve the sintering characteristics and sintered body characteristics, while If it exceeds 3% by weight, the rate of α-formation of the α-silicon nitride formed decreases, and further, with the increase in the number of nuclei during sintering, β-columnar crystals are refined in the structure of the sintered body, resulting in burning. This is because the consolidation characteristics do not improve.

次に、含窒素シラン化合物及び／又は非晶質窒化ケイ
素に上記α−及びβ−窒化ケイ素粉末を添加した混合物
を非酸化性雰囲気下で加熱結晶化し、添加した窒化ケイ
素粉末表面上に包晶反応的にα−窒化ケイ素を析出させ
る。ここで非酸化性雰囲気とは窒素又はアンモニアを含
む雰囲気である。非酸化性雰囲気で加熱する理由は、気
相反応で得られた原料は酸化性雰囲気下では非常に不安
定であり酸素等と反応して酸化物は酸窒化物を生成し易
く、得られるα−窒化ケイ素の特性を悪化させるからで
ある。この際の加熱結晶化温度としては、1350℃以上特
に150℃以上が好ましい。1350℃未満の温度では非晶質
部分が残り生成窒化ケイ素粉末に酸化・変質が生じ充分
な焼結体特性が得られにくい。Next, a mixture obtained by adding the above α- and β-silicon nitride powder to the nitrogen-containing silane compound and / or amorphous silicon nitride is heated and crystallized in a non-oxidizing atmosphere, and a peritectic crystal is formed on the surface of the added silicon nitride powder. Reactively deposit α-silicon nitride. Here, the non-oxidizing atmosphere is an atmosphere containing nitrogen or ammonia. The reason for heating in a non-oxidizing atmosphere is that the raw material obtained by the gas phase reaction is very unstable under the oxidizing atmosphere, and reacts with oxygen or the like to easily produce oxides and oxynitrides. -This is because the properties of silicon nitride are deteriorated. The heating crystallization temperature at this time is preferably 1350 ° C. or higher, particularly preferably 150 ° C. or higher. If the temperature is lower than 1350 ° C., an amorphous portion remains, and the resulting silicon nitride powder is oxidized and deteriorated, so that it is difficult to obtain sufficient sintered body characteristics.

〔実施例〕〔Example〕

以下、実施例と比較例をあげてさらに具体的に本発明
を説明する。Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

実施例１〜９ 比較例１〜10 NH₃とSiCl₄を反応温度120℃、NH₃/SiCl₄モル比6.8の
気相状態で反応させて、含窒素化合物を得た。次に、こ
の粉末に無添加も含め、β−窒化ケイ素及びα−窒化ケ
イ素からなる各種混合粉末を、前記窒素化合物から理論
的に生成される窒化ケイ素に対し第１表に示すとおり添
加量（内割）を変えて混合し、N₂雰囲気下1550℃×2h加
熱して結晶化させてα−窒化ケイ素粉末を得た。Examples 1 to 9 Comparative Examples 1 to 10 NH ₃ and SiCl ₄ were reacted at a reaction temperature of 120 ° C. in a gas phase of NH ₃ / SiCl ₄ molar ratio of 6.8 to obtain a nitrogen-containing compound. Next, as shown in Table 1, various mixed powders composed of β-silicon nitride and α-silicon nitride were added to the silicon nitride theoretically produced from the nitrogen compound, as shown in Table 1 (including no addition). The mixture was heated at 1550 ° C. for ₂ hours in an N ₂ atmosphere to be crystallized to obtain α-silicon nitride powder.

得られたα−窒化ケイ素粉末についてα化率、比表面
積の測定を行つた。その結果を第１表に示す。The α-silicon nitride powder was measured for α conversion and specific surface area. Table 1 shows the results.

次に、この粉末90重量％に、焼結助剤として、MgO3重
量％、Al₂O₃2重量％、Y₂O₃5重量％を添加し、更に1,1,1
−トリクロルエタンを加えて４時間ボールミルで湿式混
合し、乾燥後、100kg/cm²の成形圧で６×10×60mm形状
に金型成形した後、2000kg/cm²の成形圧でCIP成形し
た。Next, ₃ % by weight of MgO, ₂ % by weight of Al ₂ O _{3, and} 5% by weight of Y ₂ O ₃ were added as sintering aids to 90% by weight of the powder, and 1,1,1
- wet-mixed in a 4-hour ball mill added trichloroethane, dried, after molding to 6 × 10 × 60 mm shape molding pressure of 100 kg / cm ^2, and CIP molded at a molding pressure of 2000 kg / cm ^2.

これらの成形体をカーボンルツボにセツトし、N₂ガス
雰囲気中、1700℃×4h焼成して焼結体を得た。得られた
焼結体を研削後相対密度と３点曲げ法にて常温と高温
（1200℃）の強度を測定した。それらの結果を第２表の
焼結体Ａとして示す。These compacts were set in a carbon crucible and fired at 1700 ° C. for 4 hours in an N ₂ gas atmosphere to obtain a sintered body. After grinding the obtained sintered body, the relative density and the strength at normal temperature and high temperature (1200 ° C.) were measured by a three-point bending method. The results are shown as sintered body A in Table 2.

上記で得られたα−窒化ケイ素粉末93重量％に、焼結
助剤として、Al₂O₃2重量％及びY₂O₃5重量％としたこ
と、並びにCIP成形体の焼結条件を1850℃×4hとしたこ
と以外は同様にして試験した。その結果を第２表の焼結
体Ｂに示す。To 93% by weight of the α-silicon nitride powder obtained above, 2% by weight of Al ₂ O ₃ and 5% by weight of Y ₂ O ₃ were used as sintering aids, and the sintering conditions of the CIP compact were 1850. The test was conducted in the same manner except that the temperature was changed to 4 hours. The results are shown in Table 2 for sintered body B.

さらに上記で得られたα−窒化ケイ素粉末95重量％
に、焼結助剤として、Al₂O₃1.5重量％及びY₂O₃3.5重量
％としたこと、並びにCIP成形体の焼結条件を1850℃×
ｈとしたこと以外は同様にして試験した。その結果を第
２表の焼結体Ｃに示す。Further, 95% by weight of the α-silicon nitride powder obtained above
In addition, as a sintering aid, Al ₂ O _{3 was} 1.5% by weight and Y ₂ O _{3 was} 3.5% by weight, and the sintering condition of the CIP compact was 1850 ° C. ×
The test was performed in the same manner except that h was used. The results are shown in Table 2 for sintered body C.

尚、表に示した測定値は次の方法によつた。 The measured values shown in the table were obtained by the following methods.

（１） α化率……理学電気（株）製のガイガーフラツ
クスRAD−II B型のＸ線回折による。(1) α conversion rate: X-ray diffraction of Geiger flux RAD-IIB type manufactured by Rigaku Denki KK

（２） 比表面積…湯浅アイオニクス社製のカンターブ
Jr BET1点法による。(2) Specific surface area: Cantab made by Yuasa Ionics
Jr BET One point method.

（３） 金属不純物（Fe、Al、Ca、Mg）……JIS−Ｇ−1
322に準拠。(3) Metallic impurities (Fe, Al, Ca, Mg) ... JIS-G-1
Conforms to 322.

〔発明の効果〕〔The invention's effect〕

本発明のα−窒化ケイ素粉末は、易焼結性であり焼結
体強度にすぐれた窒化ケイ素焼結体を製造することがで
きる。これは、β−窒化ケイ素とα−窒化ケイ素からな
る混合種を用いることにより、β−柱状晶の析出過程を
制御できるので、析出するβ−柱状晶の大きさ、アスペ
クト比等を変化させることができた結果である。The α-silicon nitride powder of the present invention can produce a silicon nitride sintered body that is easily sintered and has excellent sintered body strength. This is because, by using a mixed species of β-silicon nitride and α-silicon nitride, the precipitation process of β-columnar crystals can be controlled, so that the size, aspect ratio, etc. of the precipitated β-columnar crystals can be changed. This is the result.

Claims (1)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】含窒素シラン化合物及び／又は非晶質窒化
ケイ素を原料とし、この原料に、非表面積10〜20m²/gで
Fe、Al、Ca及びMgの合計が1000ppm以下のβ−窒化ケイ
素とα−窒化ケイ素とを、前記原料から生成される理論
窒化ケイ素に対して合計２〜10重量％かつβ−窒化ケイ
素0.3〜３重量％の割合として添加し、次いでそれを非
酸化性雰囲気下において加熱結晶化することを特徴とす
るα−窒化ケイ素粉末の製造方法。1. A nitrogen-containing silane compound and / or amorphous silicon nitride as a raw material, which has a non-surface area of 10 to 20 m ² / g.
The total of Fe, Al, Ca and Mg is β-silicon nitride and α-silicon nitride having a total of 1000 ppm or less, a total of 2 to 10% by weight and β-silicon nitride 0.3 to 0.3% by weight based on theoretical silicon nitride produced from the raw material. A method for producing α-silicon nitride powder, characterized in that it is added in a proportion of 3% by weight and then heated and crystallized in a non-oxidizing atmosphere.