JPS60186406A - Continuous preparation of alpha type silicon nitride - Google Patents

Abstract

PURPOSE:To prepare high-purity alpha type Si3N4 in high yield continuously, by calcining finely powdered metal silicon in a tunnel furnace in an nitrogen gas atmosphere having extremely low oxygen content at high temperature. CONSTITUTION:In a pressure type tunnel furnace equipped with vacuum replacement chambers at the inlet and the outlet, metal silicon powder having particle size adjusted to <=325 meshes is placed on a bed plate made of silicon nitride, and passed through it. The metal silicon of a raw material is sent through the vacuum replacement chamber at the inlet, air attached to the metal silicon is almost completely removed, and passed through the tunnel furnace. The furnace has an N2 gas atmosphere with <=10<-10> oxygen partial pressure and a small amount of reducing gases such as H2, CO, etc., and is heated at 1,000-1,500 deg.C to nitrigenize the metal silicon. Powder of alpha type Si3N4 having at least >=90% purity of alpha type Si3N4 is formed continuously, and taken out through the vacuum replacement chamber from the tunnel furnace.

Description

【発明の詳細な説明】 本発明は、窒化けい素の連続的製法に関し、特にプッシ
ャ一式トンネル炉を用いて、連続的且っ高収率でアルフ
ァ（α）型窒化けい素を製造する方法に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously producing silicon nitride, and in particular to a method for producing alpha (α) type silicon nitride continuously and in high yield using a pusher-equipped tunnel furnace. .

窒化けい素は、低温型のαと高温型のβの二つの変態が
知られているが、それぞれの単−相を得ることはむずか
しく１通常、混合物として存在する。また、窒化けい素
は、共有結合性の強い物質であって、高温強度や化学的
耐食性などに優れ。Silicon nitride is known to undergo two transformations: a low-temperature type α and a high-temperature type β, but it is difficult to obtain a single phase of each of them, so they usually exist as a mixture. In addition, silicon nitride is a substance with strong covalent bonds and has excellent high-temperature strength and chemical corrosion resistance.

また熱膨張率が極めて小さい特性を有し、各種エンジン
部材や熱交換器、あるいはその他各種耐熱性材料として
の利用が期待され、広く用途研究が進められている。し
かし、一般に窒化けい素焼給体を高温高応力材料として
実用に供する場合には。In addition, it has an extremely low coefficient of thermal expansion, and is expected to be used in various engine parts, heat exchangers, and various other heat-resistant materials, and research on its use is widely underway. However, in general, when a silicon nitride burner is used as a high-temperature, high-stress material for practical use.

高温での物理的、化学的安定性が厳しく要求される。こ
の物理的、化学的特性は、焼結体を構成する素材の種類
、純屓−粒度及び結晶型等に大きく影響され、特に窒化
けい素を素材とする焼結体にあっては、α型を可及的高
度に含有した窒化けい素粉床が望ましく、高強度焼結体
構造物を提供することができる。Physical and chemical stability at high temperatures is strictly required. These physical and chemical properties are greatly influenced by the type, grain size, crystal type, etc. of the material that makes up the sintered body. In particular, in the case of a sintered body made of silicon nitride, α-type A silicon nitride powder bed containing as high as possible is desirable and can provide a high strength sintered structure.

従来、α型窒化けい素の工業的製造法として。Conventionally, as an industrial manufacturing method for α-type silicon nitride.

金属けい素を窒素ガスを含む雰囲気中で１０００〜１５
００℃の温度で加熱するバッチ式方法が最も広く実用さ
れている。しかし、この方法は、炉の気密性を保ってＮ
２　及び／又はＮＨ，雰囲気中で加熱反応させることが
重要で、特に−けい素の窒化反応の反応熱（３８１＋　
２Ｎ２＝Ｓｉ３Ｎ４＋１７６　Ｋ　ｃａｔ）を利用する
関係から、炉内の原料の充てん位置によって窒化反応開
始時間が異なり。1000-15 in an atmosphere containing nitrogen gas
A batch method using heating at a temperature of 0.000C is most widely used. However, this method maintains the airtightness of the furnace and
2 and/or NH, it is important to carry out the reaction by heating in an atmosphere, especially the reaction heat of the nitriding reaction of -silicon (381+
2N2=Si3N4+176 K cat), the nitriding reaction start time differs depending on the filling position of the raw material in the furnace.

反応の進行もばらばらで、そのため均一な加熱反応が得
られない。その結果、α型を高い割合で含有する窒化け
い素を得ることは極めて困難であり。The progress of the reaction is uneven, and therefore a uniform heating reaction cannot be obtained. As a result, it is extremely difficult to obtain silicon nitride containing a high proportion of α-type.

更にバッチ間の品質のばらつきも避けられないなど工業
的製法としては望ましい方法ではない。Furthermore, variations in quality between batches are unavoidable, making this method undesirable as an industrial manufacturing method.

このようなバッチ式製法の改善法として、けい素の粉末
等を棚仮に載置し、これをトンネル炉に入れて窒素を含
む非酸化性ガスと向流で接触させ。As an improvement to such a batch-type manufacturing method, silicon powder or the like is placed on a shelf, placed in a tunnel furnace, and brought into contact with a non-oxidizing gas containing nitrogen in a countercurrent flow.

常温から次第に温度を上昇させるようにして加熱反応さ
せる方法が提案された（特開昭５８−８８１０７号公報
）。しかし、この方法によって製造された窒化けい素は
一α型の含有率がいずれも８０％未満であり、充分満足
しつるに至っていない。A method has been proposed in which a heating reaction is carried out by gradually raising the temperature from room temperature (Japanese Patent Application Laid-open No. 88107/1983). However, the silicon nitride produced by this method has a content of -α type less than 80% in all cases, and is not fully satisfactory.

本発明者らは、このような実状において、更に高純度の
α型窒化げい累を工業的に有利に製造する方法について
−特に、上記提業法の技術的欠陥に関し、多くの要因を
追求した。その結果、金属けい累の窒化反応１％にα型
窒化けい素の形成は。Under these circumstances, the present inventors investigated many factors regarding the industrially advantageous method of manufacturing α-type nitride with higher purity, particularly regarding the technical deficiencies of the above-mentioned method. . As a result, α-type silicon nitride was formed in 1% of the nitriding reaction of metal silicon.

微量の酸素の存在によっても極めて大きな悪影響を受け
一前記の特開昭５８−８８１０７号公報に開示された方
法では１反応領域におけるＮ２雰囲気中のＯ濃度を充分
低下させることができないま ため１反応生成物中のα型窒化けい累の含有率は可成り
低いものであることがわかった。本発明者らは１反応系
に存在させるＮ　雰囲気における０　量に着目し、Ｏ分
圧とα型窒化げい累生成２ 率との関係について研究を重ねた結果、０！　分圧を１
（１”’ａｔｍ　以下にすることにより９（１以上のα
型窒化げい素を容易に得ることを見出し１本発明に到っ
た。Even the presence of a trace amount of oxygen has a very large negative effect.The method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 58-88107 cannot sufficiently reduce the O concentration in the N2 atmosphere in one reaction region. It was found that the content of α-type nitride silicate in the product was quite low. The present inventors focused on the amount of 0 in the N atmosphere present in the reaction system, and as a result of repeated research on the relationship between O partial pressure and the rate of α-type nitride formation, we found that 0! partial pressure 1
(1"'atm or less, 9 (1 or more α
The inventors have discovered that type silicon nitride can be easily obtained and have arrived at the present invention.

すなわち１本発明は、粉末状金属けい素を合板に載置し
てトンネル炉に送入し、窒素雰囲気下に１０００〜１５
００−４℃の温度範囲で窒化反応させる窒化けい素の製
造方法において、トンネル炉の入口及び出口にそれぞれ
真壁置換室を設けたプッシャ一式トンネル炉を用い、該
粉末状金属叶い累を炉の入口に隣接する真空置換室を通
して炉の入口から順次送入し、炉内の酸素ガス分圧を１
０ １０１０ａｔ下の条件下で窒化反応させ、得られた反応
生成物を炉の出口から、それに隣接する真空置換室を経
て連続的に取出す実用性の優れたα型窒化げい累の連続
的製造方法を提供する。That is, in the present invention, powdered metal silicon is placed on a plywood board, fed into a tunnel furnace, and heated to 1,000 to 15
In a method for producing silicon nitride in which a nitriding reaction is carried out in the temperature range of 00-4°C, a pusher-equipped tunnel furnace with solid wall displacement chambers provided at the entrance and exit of the tunnel furnace is used, and the powdered metal pile is placed at the entrance and exit of the furnace. Oxygen gas is introduced sequentially from the entrance of the furnace through the vacuum displacement chamber adjacent to the
Continuous production of highly practical α-type nitriding products, in which the nitriding reaction is carried out under conditions of 0.1010 at, and the resulting reaction product is continuously taken out from the outlet of the furnace through the vacuum replacement chamber adjacent to it. provide a method.

本発明の方法に用いる粉末状金属けい素原料は。The powdered metal silicon raw material used in the method of the present invention is as follows.

可及的に微粉砕されたものが望ましく、実用的には３２
５メツシユ下に調整されたものが好都合に使用できる。It is desirable that it be as finely pulverized as possible, and practically 32
One adjusted below 5 meshes can be conveniently used.

また１合板に載置される微粉状金屑げい累は、粉末のま
＼でもよいし１反応温度において容易に分解あるいは揮
散しつる適当なバインダーを用いて、均一反応が得られ
る粒状あるいは板状などに成形して反応に供することも
できる。In addition, the fine powder metal scraps placed on the plywood may be in the form of powder, or they may be in the form of granules or plates that allow a uniform reaction by using an appropriate binder that easily decomposes or volatilizes at the reaction temperature. It can also be formed into a shape and subjected to the reaction.

粉末粒子が粗いと窒化反応が不充分になりやすく。If the powder particles are coarse, the nitriding reaction tends to be insufficient.

またβ型の窒化けい素が形成されるので好ましくない。Furthermore, β-type silicon nitride is formed, which is not preferable.

金属けい素装置用台板は、窒化反応条件下において熱的
にも化学的にも耐性を有する安定なものであれば、どん
な材料で形成させてもよく１例えば窒化けい累などが有
利に用いられる。The base plate for the metal silicon device may be made of any stable material that is thermally and chemically resistant under nitriding reaction conditions. For example, silicon nitride is advantageously used. It will be done.

また１本発明の方法で用いる炉は一通′縮のプッシャ一
式トンネル炉の入口及び出口にそれぞれ真空置換室を設
けた特殊なもので、各室は各日に扉を介して気密に隣接
して成るものである。真空置換室は、炉の内部と外気を
遮断する位置にあって。In addition, the furnace used in the method of the present invention is a special type in which vacuum displacement chambers are provided at the inlet and outlet of a one-way pusher tunnel furnace. It is what it is. The vacuum displacement chamber is located in a position that isolates the inside of the furnace from outside air.

炉入口側扉と外気に通ずる扉を閉じるとき気密状態が得
られ一操業中は、例えば真空ポンプによって真空条件に
保持されるから、空気、特に０　が炉内に流入すること
を実質的に完全に防止しつるものである。そして、原料
を載置した合板は、炉入口側の真空置換室中を通って炉
の入口から炉内へ運ばれ、炉出口から隣接する真空置換
室を通って外へ取出される。これらの原料を載せた合板
の移動は、プッシャー装置を利用して好都合に行なうこ
とができる。このような真空置換室を備えたプッシャ一
式トンネル炉を用いるときは、入口側の該室に入った合
板上の微粉末状金属けい素原料は、その表面あるいは粒
子間に存在する空気（酸素ガス）及び望ましくない吸付
着水分が高度に除去され、炉内に送入された場合にも、
窒素ガスあるいは非酸化性含有窒素ガスで満たされた。When the furnace inlet side door and the door communicating with the outside air are closed, an airtight state is obtained, and during one operation, the vacuum condition is maintained, for example, by a vacuum pump, so that air, especially zero, is virtually completely prevented from flowing into the furnace. It is something that prevents it from hanging. Then, the plywood on which the raw material is placed is carried into the furnace through the vacuum exchange chamber on the furnace inlet side, and is taken out from the furnace outlet through the adjacent vacuum exchange chamber. The movement of the plywood loaded with these materials can be conveniently carried out using a pusher device. When using a pusher-equipped tunnel furnace equipped with such a vacuum displacement chamber, the fine powder metal silicon raw material on the plywood that has entered the chamber on the entrance side is exposed to air (oxygen gas) present on its surface or between particles. ) and undesirable adsorbed moisture is highly removed and fed into the furnace.
Filled with nitrogen gas or non-oxidizing containing nitrogen gas.

好ましくは原料の移動方向とは向流状に流されている炉
内の窒素雰囲気を極めて低い酸素分圧に保時することが
でき、特に運転操業中の炉内の酸素分圧を継続的に１０
ａｔｍ　以下に保つことが容易である。炉内の反応雰囲
気はＮ　単独でもよいが。Preferably, the nitrogen atmosphere in the furnace, which is flowing countercurrently to the moving direction of the raw materials, can be maintained at an extremely low oxygen partial pressure, and in particular, the oxygen partial pressure in the furnace can be maintained continuously during operation. 10
Easy to keep below ATM. The reaction atmosphere in the furnace may be N2 alone.

例えば還元能を有するＮＨ，Ｈあるいは００２ などの非酸化性ガスの一定少量を混用することは実用上
望ましい。また、炉内拌囲気ガスはトンネル炉の出口部
から入口部に向けて原料移動方向と向流状に継続的に流
すことがよい。For example, it is practically desirable to mix a certain amount of a non-oxidizing gas such as NH, H or 002 having reducing ability. Further, it is preferable that the in-furnace stirring surrounding gas continuously flows from the outlet to the inlet of the tunnel furnace in a countercurrent direction to the raw material movement direction.

加熱反応温度は、α型窒化けい素の製造温度として知ら
れる１０００〜１５００℃が採用され。The heating reaction temperature is 1000 to 1500°C, which is known as the production temperature of α-type silicon nitride.

またーその加熱手段としては１通常、加熱炉に用いられ
るいずれの手段も使用できる。As the heating means, any means normally used in heating furnaces can be used.

本発明の方法は、上記のように一人口及び出口にそれぞ
れ真空置換室を備えたトンネル炉を用いることにより、
炉内の輩累ガス雰囲気の酸素ガスを１０　ａｔｍ以下の
低い分圧に保って加熱窒化素を得ることは実質的に困難
で１例えば特開昭５８−８８１０７号公報に開示された
方法のように、単に向流ガスを炉内に流したＩＪ１本発
明における真空置換室に代えて、該置換室をガスシール
室としてガス置換を行った場合には、酸素分圧はせいぜ
い１０〜１０ａｔｍ　程度であって。The method of the present invention uses a tunnel furnace equipped with a vacuum displacement chamber at each of the inlet and the outlet as described above.
It is virtually difficult to obtain heated nitride by maintaining the oxygen gas atmosphere in the furnace at a low partial pressure of 10 atm or less. In this case, instead of the vacuum exchange chamber in the IJ1 invention in which countercurrent gas is simply flowed into the furnace, when gas exchange is performed using the exchange chamber as a gas seal chamber, the oxygen partial pressure is at most about 10 to 10 atm. There it is.

８０係以下のα型を含有する窒化けい累しか得られない
。Only nitride silicate containing α-type of less than 80 coefficients can be obtained.

電化反応に要する反応時間は、炉内温度条件。The reaction time required for the electrification reaction depends on the furnace temperature conditions.

粉末状金属けい素の粒度や比表面積などによって変動す
るが０通常、数時間ないし数十時間である。Although it varies depending on the particle size and specific surface area of the powdered silicon metal, it is usually several hours to several tens of hours.

この反応時間は−例えば炉長１５ｍの一般面トンネル炉
の場合には、プッシャー装置による原料の炉内の移動速
度は、１〜５０關／分程度、好ましくは３〜３０ｍｍ／
分程度が採用される。炉内は。This reaction time is - For example, in the case of a general surface tunnel furnace with a furnace length of 15 m, the moving speed of the raw material in the furnace by the pusher device is about 1 to 50 mm/min, preferably 3 to 30 mm/min.
Approximately 1 minute is adopted. Inside the furnace.

通常、長さ方向の中央部が１例えば１５００℃の最高温
度に設定され、こ＼を通る反応生成物は反応を完結しな
がら出口方向に移動し、出口部から流入する一定組成の
雰囲気ガスで冷却されて真空置換室から取出される。Usually, the central part in the length direction is set at the maximum temperature of 1,500°C, for example, and the reaction products passing through this part move toward the outlet while completing the reaction, and the atmospheric gas of a constant composition flows in from the outlet part. It is cooled and taken out from the vacuum displacement chamber.

本発明方法によれば、α型が例えば９０％以上からなる
高純度のα型窒化けい素を容易に製造することができ、
酸素分圧を１０ａｔｍ以下に低下させるとき、５俤以下
の未反応原料を含む９５チ以上のものを得ることができ
る。また１本発明の方法は、同一の反応諸条件で長期連
続的に操業することが可能であり１合板ごとの生成物の
バラツキが極めて小さく、高品質のα型窒化けい素を安
定に得ることができる。According to the method of the present invention, high purity α-type silicon nitride comprising, for example, 90% or more of α-type can be easily produced,
When the oxygen partial pressure is lowered to 10 atm or less, more than 95 atm containing less than 5 atm of unreacted raw material can be obtained. In addition, the method of the present invention can be operated continuously for a long period of time under the same reaction conditions, and the variation in the product from one plywood to another is extremely small, making it possible to stably obtain high quality α-type silicon nitride. I can do it.

本発明の方法で得られる窒化叶い累は、極めて高品質の
α型Ｓｉ３Ｎ４　であって、従来のものに比べて、より
高い強度の安定な窒化けい素焼給体を提供しうるばかり
でなく、ニューセラミック原料として高い信頼性の要求
されるエンジンやガスタービン等の部材への利用が期待
できる極めて望ましいものであり、その他所しい分野へ
の用途も大いに期待できる。The nitrided material obtained by the method of the present invention is an extremely high quality α-type Si3N4, which not only can provide a stable silicon nitride burner with higher strength than conventional ones, but also has a new It is extremely desirable as a ceramic raw material and can be expected to be used in parts such as engines and gas turbines that require high reliability, and it is also highly expected to be used in other desired fields.

次に、実施例により本発明を更に詳細に説明する。Next, the present invention will be explained in more detail with reference to Examples.

実施例１〜７及び比較例 比表面積４．Ｏｎ？／ｇを有する工業用金属けい素粉末
２００ｇを台形状２００Ｘ２００朋のアルミナ製の台板
上に載置し、全長１５ｍ、炉外形１．５ｍ×２ｍの入口
及び出口に真空置換室を設はプッシャ一式トンネル炉を
開いて、炉内の最高温部を１５００℃に保持し、炉内の
酸素分圧と合板の送りスピードを表中に示す一定条件に
保ちなから運１１− 続窒化を行なった。この時の酸素分圧はＮ２゜Ｎ２．Ｎ
Ｈ３の流量比率を適当にコントロールする事によって微
調整しながら日本碍子製０Ｐ−Ｘ型０２分圧計を用いて
測定した。得られた窒化げい累のα型係及び未反応金属
８１％はＸ線回折ピークからめた。それらの結果を表１
に示す。Examples 1 to 7 and comparative examples Specific surface area 4. On? 200g of industrial silicon metal powder having a particle size of 200g/g was placed on a trapezoidal 200x200mm alumina base plate, and vacuum displacement chambers were installed at the inlet and outlet of the furnace with a total length of 15m and a furnace outer diameter of 1.5m x 2m. A complete tunnel furnace was opened, and the highest temperature inside the furnace was maintained at 1500℃, and the oxygen partial pressure inside the furnace and the feeding speed of the plywood were maintained at the constant conditions shown in the table. . The oxygen partial pressure at this time was N2°N2. N
The measurement was carried out using a Nippon Insulator 0P-X type 02 partial pressure meter while making fine adjustments by appropriately controlling the flow rate ratio of H3. 81% of the α-type and unreacted metals in the obtained nitride deposit were determined from the X-ray diffraction peak. Table 1 shows the results.
Shown below.

なお、比較のために、同じ原料を用い、真空置換を行な
わないで、置換室をガスシールのみによって行なった場
合の結果も示した。For comparison, the results are also shown when the same raw materials were used and the replacement chamber was only gas-sealed without vacuum replacement.

１２− 上表の結果から１本発明の方法が、従来法に比べてはる
かに優れていることがわかる。12- From the results in the table above, it can be seen that the method of the present invention is far superior to the conventional method.

特許出願人　信越化学工業株式会社 １４− 一り０−Patent applicant: Shin-Etsu Chemical Co., Ltd. 14- One 0-

Claims (1)

【特許請求の範囲】[Claims] １、粉末状金属けい素を合板に載置してトンネル炉に送
入し一窒素雰囲気下に１０００〜１５００℃の温度範囲
で窒化反応させる窒化けい素の製造方法において、トン
ネル炉の入口及び出口にそれぞれ真空置換室を設けたプ
ッシャ一式トンネル炉を用い、該粉末状金属けい素を炉
の入口に隣接する真空置換室を通して炉の入口から順次
送入し、炉内の酸素分圧をｌロー１０ａｔｍ以下の条件
下で窒化反応させ、得られた反応生成物を炉の出口から
、それに隣接する真空置換室を経て連続的に取出すこと
を特徴とするアルファ型窒化けい素の連続的製造方法・
２、粉末状金属けい素が３２５メツシユ以下の微細粒度
に調整されたものである特許請求の範囲第１項記載の方
法。1. In a method for producing silicon nitride, in which powdered silicon metal is placed on a plywood board and sent into a tunnel furnace to undergo a nitriding reaction in a nitrogen atmosphere at a temperature range of 1000 to 1500°C, the inlet and outlet of the tunnel furnace are Using a pusher-equipped tunnel furnace with a vacuum displacement chamber in each chamber, the powdered silicon metal is sequentially introduced from the furnace entrance through the vacuum displacement chambers adjacent to the furnace entrance, and the oxygen partial pressure in the furnace is lowered by 1 row. A method for continuous production of alpha-type silicon nitride, characterized by carrying out a nitriding reaction under conditions of 10 atm or less, and continuously taking out the obtained reaction product from the outlet of the furnace via a vacuum displacement chamber adjacent thereto.
2. The method according to claim 1, wherein the powdered silicon metal is adjusted to a fine particle size of 325 mesh or less.