JPH09255311A - Production of silicon nitride powder - Google Patents
Production of silicon nitride powderInfo
- Publication number
- JPH09255311A JPH09255311A JP8069496A JP6949696A JPH09255311A JP H09255311 A JPH09255311 A JP H09255311A JP 8069496 A JP8069496 A JP 8069496A JP 6949696 A JP6949696 A JP 6949696A JP H09255311 A JPH09255311 A JP H09255311A
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- Prior art keywords
- nitriding
- rate
- powder
- silicon nitride
- nitride powder
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Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は窒化けい素粉末の製
造方法、特には流動層、移動層又はロータリーキルンの
いずれかの設備により金属けい素を直接窒化して高窒化
率の窒化けい素を製造する方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing silicon nitride powder, and in particular, a method for producing silicon nitride having a high nitriding rate by directly nitriding metal silicon with equipment such as fluidized bed, moving bed or rotary kiln. It is about how to do it.
【0002】[0002]
【従来の技術】従来、窒化けい素粉末の製造方法として
は金属けい素を窒化する直接窒化法、シリカ還元法、イ
ミドの熱分解法が知られているが、工業的規模で経済性
に優れた製法としては直接窒化法が最も有望視されてい
る。この直接窒化法には流動層方式、移動層方式、ロー
タリーキルン方式、トンネル炉方式が提案されている
が、金属けい素粉末を流動層設備により直接窒化して連
続的に窒化けい素粉末を得るには、 1,150〜 1,400℃の
温度域においてN2 単独、N2 −H2 あるいはN2 −N
H3 の混合ガス等の雰囲気で窒化が行われる。2. Description of the Related Art Conventionally, as a method for producing silicon nitride powder, a direct nitriding method of nitriding metal silicon, a silica reduction method, and a thermal decomposition method of imide have been known, but they are excellent in industrial scale and economical. The direct nitriding method is the most promising as a manufacturing method. The fluidized bed method, moving bed method, rotary kiln method, and tunnel furnace method have been proposed for this direct nitriding method. However, in order to continuously obtain silicon nitride powder by directly nitriding metal silicon powder with a fluidized bed equipment. Is N 2 alone, N 2 —H 2 or N 2 —N in the temperature range of 1,150 to 1,400 ° C.
Nitriding is performed in an atmosphere such as a mixed gas of H 3 .
【0003】[0003]
【発明が解決しようとする課題】しかし、一般に高強
度、高密度の窒化けい素焼結体を得ようとする場合は、
原料粉末の結晶系を高α型としてα化率の高い窒化けい
素を製造することが望ましいが、α相は低温反応でβ相
は高温反応で生成し易いので、窒化率を高めるため反応
温度を上げて反応を加速すると、反応に伴なう急激な発
熱により温度がより上昇し、高α化率の窒化けい素の製
造が困難になる。また、この場合には急な温度上昇のた
め最悪の場合には未反応の金属けい素粉末同士が融着し
て比表面積が低下するため反応が抑制されて窒化率が低
いところで安定することもあり、さらには粒子同志の凝
集、付着によって生成物が塊状化し、反応を継続できな
くなるという問題が発生する。However, in general, in order to obtain a high-strength and high-density silicon nitride sintered body,
It is desirable to produce silicon nitride with a high α conversion by using the crystal system of the raw material powder as a high α type, but since the α phase is easily generated at low temperature reaction and the β phase is generated at high temperature reaction, the reaction temperature should be increased to increase the nitriding rate. When the temperature is raised to accelerate the reaction, the temperature further rises due to the abrupt heat generation accompanying the reaction, and it becomes difficult to produce silicon nitride having a high α conversion rate. Further, in this case, due to a sudden temperature rise, unreacted metal silicon powders are fused to each other in the worst case and the specific surface area is reduced, so that the reaction is suppressed and the nitriding rate becomes stable at a low rate. In addition, there is a problem that the product is agglomerated due to the aggregation and adhesion of the particles, and the reaction cannot be continued.
【0004】なお、金属けい素を粉末状または顆粒状に
保って反応炉中で窒化けい素を連続的に製造するには、
流動層、移動層、ロータリーキルン方式が知られている
が、これらの連続供給、連続排出方法では個々の粒子は
一様な滞留時間の保持が難しく、かつ滞留時間分布をも
っているため各粒子間の窒化率に分布が生じる。一方、
直接窒化反応においては金属けい素内へのN2 の拡散が
律速となる。また、窒化反応により生成した窒化膜自身
がN2 の拡散の妨げとなり、所定時間に保持しただけで
は到達窒化率は 100%に至らず、反応温度に依存した値
で飽和するという問題点もあるため、原料を連続供給
し、中間体を連続排出する方法において、高窒化率、高
α化率の窒化けい素粉末を得るには、低温での反応を繰
り返すという多段反応が必須であるとされている。In order to continuously produce silicon nitride in a reaction furnace while keeping the metal silicon in powder or granular form,
Fluidized bed, moving bed, and rotary kiln systems are known, but it is difficult to maintain a uniform residence time for each particle by continuous supply and continuous discharge methods of these, and since there is a residence time distribution, nitriding between particles Distribution of rates occurs. on the other hand,
In the direct nitriding reaction, diffusion of N 2 into the metal silicon is rate-determining. Further, the nitride film itself generated by the nitriding reaction hinders the diffusion of N 2 , and the reached nitriding rate does not reach 100% only by keeping it for a predetermined time, and it is saturated at a value depending on the reaction temperature. Therefore, in the method of continuously supplying the raw material and continuously discharging the intermediate, in order to obtain a silicon nitride powder having a high nitriding rate and a high α-converting rate, it is said that a multi-step reaction of repeating the reaction at a low temperature is essential. ing.
【0005】[0005]
【課題を解決するための手段】本発明はこのような不
利、問題点を解決した窒化けい素粉末の製造方法に関す
るもので、これは金属けい素粉末を連続的に多段で直接
窒化する際、その中間体粉末を窒化率と相関のある比重
差により分級し、その窒化率に応じて次の工程に振り分
けることを特徴とするものである。SUMMARY OF THE INVENTION The present invention relates to a method for producing silicon nitride powder which solves the above disadvantages and problems, which is obtained by directly nitriding metal silicon powder continuously in multiple stages. It is characterized in that the intermediate powder is classified according to the difference in specific gravity having a correlation with the nitriding rate, and is distributed to the next step according to the nitriding rate.
【0006】[0006]
【発明の実施の形態】本発明は金属けい素粉末あるいは
その造粒品を連続供給し、窒化物を連続排出する反応器
を用いて、 1,150〜 1,400℃の温度域で窒化させて窒化
けい素を連続的に生産し、1段反応で得られた窒化けい
素中間体をその窒化率により分級することを特徴とする
ものである。BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a reactor which continuously supplies metal silicon powder or a granulated product thereof and continuously discharges nitrides, and nitrides silicon nitride in a temperature range of 1,150 to 1,400 ° C. Is continuously produced, and the silicon nitride intermediate obtained in the one-step reaction is classified according to the nitriding rate.
【0007】上記連続法による窒化けい素の製造法で高
窒化率で、かつ高α化率の窒化けい素を得るには低温度
で数回に分ける多段反応により徐々に窒化率を上げてい
くことがよい。しかし、例えば 1,230℃での第1段階で
窒化を行なって得られる中間体の窒化率は、この平均滞
留時間を6時間とすると、図1に示したように窒化率が
90〜 100%のものが62%、80〜90重量%のものが13%、
70〜80%のものが7%、60〜70%のものが5%…0〜10
%のもが2%と順次低下しており、この平均窒化率は80
±2%となるが、これは連続供給連続排出であるため
に、個々の粒子の滞留時間を全く一様にすることが難し
く、これらの滞留時間が異なることと粒子径分布の差
(比表面積の差)のためであり、これによって各粒子間
に窒化率の分布が生ずる。In order to obtain silicon nitride having a high nitriding rate and a high α conversion rate in the above-described method for producing silicon nitride by the continuous method, the nitriding rate is gradually increased by a multi-step reaction divided into several times at low temperature. Is good. However, for example, the nitriding rate of the intermediate obtained by performing the nitriding at the first stage at 1,230 ° C. is as shown in FIG. 1 when the average residence time is 6 hours.
62% for 90-100%, 13% for 80-90% by weight,
7-80% for 70-80%, 5% for 60-70% ... 0-10
The% nitriding rate is gradually decreasing to 2% and the average nitriding rate is 80
It is ± 2%, but it is difficult to make the residence time of individual particles completely uniform because it is continuous supply and continuous discharge, and the difference in these residence times and the difference in particle size distribution (specific surface area) Difference), which causes a distribution of the nitriding rate among the particles.
【0008】この平均窒化率とは粒子個数 1,000個以上
からなる集合体を均一に混合し、測定した窒化率で、平
均滞留時間とは反応器内滞留量(kg)を排出速度 (kg/h
r)で割った値である。したがって、連続排出される中間
体粒子は個々に異なる滞留時間をもったものの集合体で
あり、例えば 1,230℃、平均滞留時間6時間の平均窒化
率は80±2%で安定しているが、中間体を構成する個々
の粒子の窒化率は滞留時間に応じて異なる。そのため、
本発明ではこの方法で排出された窒化けい素の中間体を
窒化率により分級し、これらを高窒化率品、低窒化率品
およびその中間品というように分け、各窒化率で次工程
別に仕分けて、収率よく窒化けい素を得るようにした。The average nitriding rate is a nitriding rate measured by uniformly mixing an aggregate consisting of 1,000 or more particles, and the average residence time is the retention rate (kg) in the reactor and the discharge rate (kg / h).
It is the value divided by r). Therefore, the continuously discharged intermediate particles are aggregates having different residence times. For example, the average nitriding rate at 1,230 ° C. and the average residence time of 6 hours is stable at 80 ± 2%. The nitriding rate of individual particles forming the body varies depending on the residence time. for that reason,
In the present invention, the silicon nitride intermediates discharged by this method are classified according to the nitriding rate, and these are classified into high nitriding rate products, low nitriding rate products and intermediate products thereof, and are sorted according to the next process at each nitriding rate. The silicon nitride was obtained in good yield.
【0009】この窒化けい素中間品の仕分けは、金属け
い素が窒化けい素になると共にその窒化率に応じて密度
が上り、窒化率が 100%のものは密度が1.67倍となり、
密度の差は比重差と相関があるので、中間品の分級は公
知の方法、例えば重力沈降を利用する方法、遠心分離
器、サイクロンといった遠心力を利用する方法で容易に
行なうことができる。In the sorting of the silicon nitride intermediate products, the metal silicon becomes silicon nitride and the density increases according to the nitriding rate, and the density of 100% nitriding increases the density by 1.67 times.
Since the difference in density correlates with the difference in specific gravity, classification of the intermediate product can be easily performed by a known method, for example, a method using gravity sedimentation, a method using centrifugal force such as a centrifuge, or a cyclone.
【0010】したがって、分級後金属けい素含有率がた
とえば5重量%以下のものが得られたときには、それが
製品のスペックを満足するものであればそのまま次工程
の粉砕に進めればよく、窒化工程が1回ですむことにな
る。またさらに高い窒化率のものが必要であるときには
これを2段目の窒化反応に進めればよく、この場合には
分級により窒化率の高いものが使用できるので、未分級
で2段反応を行なうのに較べて2段目の反応温度を低
く、滞留時間も短くすることができるので、2段目反応
の負荷を小さくできる。Therefore, when the content of metal silicon after classification is, for example, 5% by weight or less, if it satisfies the specifications of the product, it is sufficient to proceed to the pulverization in the next step. Only one process is required. When a higher nitriding rate is required, it can be advanced to the second stage nitriding reaction. In this case, since a higher nitriding rate can be used by classification, the two-step reaction is performed unclassified. Since the reaction temperature of the second step can be lowered and the residence time can be shortened as compared with the above, the load of the second step reaction can be reduced.
【0011】また、窒化率が60〜90%のものは量が全体
の25〜30%であるが、そのままでは製品のスペックを満
足できないので、これらはまとめて2段反応させればよ
く、窒化率が90%以上のものも可成りの量で得ることが
でき、この中で窒化率の低いものは3段目の反応に進め
ればよい。しかし、窒化率が50%以下の低窒化率のもの
は量も全体の15%以下と少なく、このものは2段反応を
行なっても窒化率を高くすることが難しいため、これは
原料としての金属けい素粉末に混合して再び一段目の反
応を行なうことがよく、これによれば効率よく窒化工程
を進めることができる。なお、低窒化率品の供給方法は
原料フィーダーの前に初期原料である金属けい素と混合
するラインを設ける方法、あるいは原料金属けい素とは
別に中間体独自の供給設備を設け、同時に供給する方法
のどちらかを選択するようにすればよい。Further, the amount of the nitriding rate of 60 to 90% is 25 to 30% of the whole amount, but since the product specifications cannot be satisfied as they are, it is sufficient to react them in two steps at a time. Those with a rate of 90% or more can be obtained in a considerable amount, and those with a low nitriding rate can be advanced to the reaction in the third step. However, the amount of low nitriding rate of 50% or less is as small as 15% or less of the whole, and it is difficult to increase the nitriding rate even if the two-step reaction is performed. It is preferable to mix with the metal silicon powder and carry out the first-step reaction again, which allows the nitriding step to proceed efficiently. The low nitriding rate product can be supplied at the same time by installing a line for mixing with the initial raw material metal silicon in front of the raw material feeder, or by providing a supply facility unique to the intermediate separately from the raw material metal silicon. Only one of the methods should be selected.
【0012】[0012]
【実施例】つぎに本発明の実施例、比較例をあげる。 実施例1 内径80mmφの反応管、底面には多孔板である分散板、原
料金属けい素粉末を層内に供給する供給管、生成した窒
化物をオーバーフローで排出する排出管を備えた流動層
反応器に、顆粒状の窒化けい素造粒品を700g仕込み、
1,250℃まで昇温し保持した。この際、反応ガスとして
N2 −20%H2 混合ガスを流し、層内充填物が充分な流
動状態を保つようにした。ついで、最大粒径10μmの金
属けい素粉末を造粒、仮焼し作製した顆粒状の金属けい
素造粒品を 80g/minの速度で供給した。窒化された生成
物は連続的に排出管より平均 120g/hrの速度、平均窒化
率80%で排出し(平均滞留時間約6時間)、これを遠心
分級器とサイクロンの組み合わせにて、以下の様なA、
B、Cの3成分に分級した。 成分 A 窒化率 38.7% 比率 13.8% B 74.5% 33.2% C 94.8% 53.0%Next, examples of the present invention and comparative examples will be described. Example 1 Fluidized bed reaction equipped with a reaction tube having an inner diameter of 80 mmφ, a dispersion plate which is a porous plate on the bottom surface, a supply tube for supplying raw material silicon metal powder into the bed, and a discharge tube for discharging generated nitride by overflow. Charge 700g of granular silicon nitride granulated product into a container,
The temperature was raised to 1,250 ° C and maintained. At this time, a mixed gas of N 2 -20% H 2 was flown as a reaction gas so that the filling material in the layer was kept in a sufficiently fluidized state. Then, a granular metal silicon granulated product prepared by granulating and calcining a metal silicon powder having a maximum particle size of 10 μm was supplied at a rate of 80 g / min. The nitrided product was continuously discharged from the discharge pipe at an average rate of 120 g / hr and an average nitriding rate of 80% (average residence time of about 6 hours), and this was combined with a centrifugal classifier and a cyclone as follows. Like A,
Classified into 3 components of B and C. Ingredient A Nitriding rate 38.7% Ratio 13.8% B 74.5% 33.2% C 94.8% 53.0%
【0013】つぎに、これら中間体のうち窒化率が94.8
%である成分Cを通常の手法で粗粉砕、微粉砕したとこ
ろ、この場合には粉砕工程で残った未反応の金属けい素
が酸化されることもあって見かけ上の窒化率が向上し、
窒化率96.5%の窒化けい素粉末を1回の反応工程で得る
ことができた。Next, among these intermediates, the nitriding rate is 94.8.
%, The component C was roughly pulverized and finely pulverized by a usual method. In this case, the unreacted metal silicon remaining in the pulverization step may be oxidized, and the apparent nitriding rate is improved.
A silicon nitride powder having a nitriding rate of 96.5% could be obtained in one reaction step.
【0014】比較例1 実施例1で得られた中間体を窒化率により分級せずに、
そのまま実施例と同じような粉砕工程を得て窒化けい素
製品としたところ、窒化率が88.2%と低く製品としては
充分なものではなかった。Comparative Example 1 The intermediate obtained in Example 1 was classified according to the nitriding ratio,
When the same crushing process as in the example was carried out to obtain a silicon nitride product as it was, the nitriding ratio was as low as 88.2%, which was not sufficient as a product.
【0015】実施例2 実施例1で得られた成分Cを、実施例1と同じ装置を用
いて 1,300℃で2段目の窒化反応を行なったところ、平
均窒化率が99.5%の窒化けい素が得られた。Example 2 The component C obtained in Example 1 was subjected to a second nitriding reaction at 1,300 ° C. using the same apparatus as in Example 1, and silicon nitride having an average nitriding rate of 99.5% was obtained. was gotten.
【0016】比較例2 実施例1で得られた中間体を窒化率で分けずに、そのま
ま実施例2と同様に2段目の窒化反応を行なったとこ
ろ、得られた窒化けい素の平均窒化率は90.0%にとどま
り、製品としては充分なものではなかった。 実施例3 実施例1で得られた成分Aは、通常の原料金属けい素8
に対し、2の割合で混合し(重量比)、実施例1と同じ
装置を用いて 1,230℃にて1段目の窒化反応を行ったと
ころ、平均窒化率で80.3%と通常の1段目反応とほぼ同
じ窒化けい素が得られた。 実施例4 実施例1で得られた成分Bは、そのまま実施例1と同じ
装置を用いて 1,350℃にて2段目の窒化反応を行ったと
ころ、平均窒化率で97.0%と充分な窒化率の窒化けい素
が得られた。Comparative Example 2 The intermediate product obtained in Example 1 was subjected to the second nitriding reaction in the same manner as in Example 2 without being divided by the nitriding rate, and the average nitriding of the obtained silicon nitride was performed. The rate was only 90.0%, which was not sufficient as a product. Example 3 Component A obtained in Example 1 is the usual raw material metal silicon 8
On the other hand, when mixed at a ratio of 2 (weight ratio) and subjected to the first stage nitriding reaction at 1,230 ° C. using the same apparatus as in Example 1, the average nitriding rate was 80.3%, which was the usual first stage. Almost the same silicon nitride as the reaction was obtained. Example 4 The component B obtained in Example 1 was subjected to a second nitriding reaction at 1,350 ° C. using the same apparatus as in Example 1 as it was. The average nitriding rate was 97.0%, which was a sufficient nitriding rate. Of silicon nitride was obtained.
【0017】[0017]
【発明の効果】本発明によれば1段の窒化反応により得
られた窒化けい素粉末の中間体は窒化率により分級さ
れ、高窒化率のものはそのまま製品とすることができ、
さらに高窒化率を得るための2段反応は負荷が軽くな
り、また低窒化率のものは原料戻しとするので効率のよ
い窒化工程が可能になる。According to the present invention, the intermediate product of the silicon nitride powder obtained by the one-step nitriding reaction is classified according to the nitriding rate, and the one having the high nitriding rate can be directly used as a product.
Further, the load of the two-step reaction for obtaining a high nitriding rate is lightened, and the material having a low nitriding rate is returned to the raw material, which enables an efficient nitriding process.
【図面の簡単な説明】[Brief description of drawings]
【図1】1,230℃、平均滞留時間6時間での窒化反応で
得られた窒化けい素中間体の窒化率とその存在比との関
係グラフを示したものである。FIG. 1 is a graph showing the relationship between the nitriding ratio of a silicon nitride intermediate obtained by a nitriding reaction at 1,230 ° C. and an average residence time of 6 hours and its abundance ratio.
Claims (6)
化する際、その中間体粉末を窒化率と相関のある比重差
により分級し、その窒化率に応じて次の工程に振り分け
ることを特徴とする窒化けい素粉末の製造方法。1. When directly nitriding metal silicon powder continuously in multiple stages, the intermediate powder is classified according to the specific gravity difference correlated with the nitriding rate, and distributed to the next step according to the nitriding rate. A method for producing a silicon nitride powder, which is characterized.
した二次粒子を用いる請求項1記載の窒化けい素粉末の
製造方法。2. The method for producing a silicon nitride powder according to claim 1, wherein primary particles or secondary particles obtained by granulating metallic silicon powder are used.
応、排出できる流動層、移動層、またはロータリーキル
ンのいずれかである請求項1記載の窒化けい素粉末の製
造方法。3. The method for producing silicon nitride powder according to claim 1, wherein the nitriding equipment is a fluidized bed, a moving bed, or a rotary kiln capable of continuously supplying, reacting, and discharging powdery material.
けい素含有率が5重量%以下の高窒化率のものはそのま
ま粉砕し製品にする請求項1記載の窒化けい素粉末の製
造方法。4. The production of silicon nitride powder according to claim 1, wherein among the intermediates classified by nitriding rate, those having a high nitriding rate with a metal silicon content of 5% by weight or less are pulverized as they are into a product. Method.
化率のものは原料へ戻す請求項1記載の窒化けい素粉末
の製造方法。5. The method for producing silicon nitride powder according to claim 1, wherein the intermediate having a low nitriding rate among the intermediates divided by the nitriding rate is returned to the raw material.
けい素含有量が5重量%以下の高窒化率の窒化けい素粉
末を用いて次の窒化反応を行い、金属けい素含有量 0.5
%未満の窒化けい素粉末を得る請求項1記載の窒化けい
素粉末の製造方法。6. Among the intermediates classified by the nitriding rate, the following nitriding reaction is performed by using the silicon nitride powder having a high nitriding rate of 5% by weight or less of the metal silicon content, and the metal silicon content is 0.5
% Of silicon nitride powder is obtained.
Priority Applications (1)
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JP8069496A JPH09255311A (en) | 1996-03-26 | 1996-03-26 | Production of silicon nitride powder |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP8069496A JPH09255311A (en) | 1996-03-26 | 1996-03-26 | Production of silicon nitride powder |
Publications (1)
Publication Number | Publication Date |
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JPH09255311A true JPH09255311A (en) | 1997-09-30 |
Family
ID=13404395
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JP8069496A Pending JPH09255311A (en) | 1996-03-26 | 1996-03-26 | Production of silicon nitride powder |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2012511490A (en) * | 2008-12-13 | 2012-05-24 | アルツケム・トロストベルク・ゲーエムベーハー | Method for producing high purity silicon nitride |
-
1996
- 1996-03-26 JP JP8069496A patent/JPH09255311A/en active Pending
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2012511490A (en) * | 2008-12-13 | 2012-05-24 | アルツケム・トロストベルク・ゲーエムベーハー | Method for producing high purity silicon nitride |
US8697023B2 (en) | 2008-12-13 | 2014-04-15 | Alzchem Trostberg Gmbh | Method for producing high-purity silicon nitride |
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