JP2767393B2 - Method for producing boron nitride sintered body - Google Patents
Method for producing boron nitride sintered bodyInfo
- Publication number
- JP2767393B2 JP2767393B2 JP7023484A JP2348495A JP2767393B2 JP 2767393 B2 JP2767393 B2 JP 2767393B2 JP 7023484 A JP7023484 A JP 7023484A JP 2348495 A JP2348495 A JP 2348495A JP 2767393 B2 JP2767393 B2 JP 2767393B2
- Authority
- JP
- Japan
- Prior art keywords
- boron nitride
- copper
- sintered body
- sintering
- nitride sintered
- 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
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Description
【０００１】[0001]
【産業上の利用分野】この発明は、窒化ほう素焼結体の
製造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 a boron nitride sintered body.
【０００２】[0002]
【従来の技術とその課題】窒化ほう素は、耐熱、耐食、
潤滑、絶縁性等に極めて優れているため、熔融金属のノ
ズル等として工業的に用いられ、他に替え難い素材とな
っている。この窒化ほう素は、通常は粉末で焼結して用
いられるが、単独では極めて焼結しにくいため、通常は
助剤を用いて加圧焼結されている。助剤としては、酸化
ほう素、酸化カルシウム、酸化珪素等の酸化物が用いら
れている。2. Description of the Related Art Boron nitride is known for its heat resistance, corrosion resistance,
Since it is extremely excellent in lubrication and insulation properties, it is used industrially as a nozzle for molten metal and the like, and is a material that is difficult to replace. This boron nitride is usually used by sintering it as a powder, but it is extremely difficult to sinter alone, and is usually pressure-sintered using an auxiliary agent. As the auxiliary agent, oxides such as boron oxide, calcium oxide, and silicon oxide are used.
【０００３】しかしながら、このような酸化物助剤によ
る方法で窒化ほう素を焼結した場合、製品に酸化物が残
存するため吸湿性や化学的不安定性、高温での腐食性、
潤滑性能の低下等が生じるため、ＢＮ本来の耐熱、耐
食、絶縁、潤滑等の優れた特性が発揮できないという問
題があった。そして、薄板状に発達した窒化ほう素結晶
子の面（ｃ面）が加圧軸に垂直に並ぶ（ｃ軸配向性）傾
向があるため、加圧軸に垂直に割れ易く、熱伝導に異方
性があるという問題点もあった。さらに、炭素窒化ほう
素複合系等の還元性条件下では、酸化物助剤は作用しな
い等の問題があった。また、このような問題を解消する
ために、無添加焼結法や窒化ほう素珪素による複合焼結
法等が開発されているが、前者は機械的強度が低く、後
者はＢＮ本来の性質を損なうという問題があった。[0003] However, when boron nitride is sintered by the method using such an oxide auxiliary, the oxide remains in the product, so that hygroscopicity, chemical instability, corrosiveness at high temperature,
Since lubrication performance is deteriorated, there is a problem that excellent characteristics such as heat resistance, corrosion resistance, insulation and lubrication inherent to BN cannot be exhibited. Since the plane (c-plane) of the boron nitride crystallites developed in the form of a thin plate tends to be perpendicular to the pressing axis (c-axis orientation), it is easily broken perpendicularly to the pressing axis, resulting in a difference in heat conduction. There was also the problem of being anisotropic. Further, there is a problem that the oxide auxiliary does not act under reducing conditions such as a carbon boron nitride composite system. Further, in order to solve such a problem, an additive-free sintering method and a composite sintering method using silicon boron nitride have been developed. However, the former has low mechanical strength, and the latter has a property inherent in BN. There was a problem of spoiling.
【０００４】そこでこの発明は、以上の通りの従来技術
の欠点を解消し、結晶配向性が従来のものとは異なる新
しい窒化ほう素焼結体を製造することのできる方法を提
供することを目的としている。Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a method capable of producing a new boron nitride sintered body having a different crystal orientation from the conventional one. I have.
【０００５】[0005]
【課題を解決するための手段】この発明は、上記の課題
を解決するものとして、窒化ほう素またはその前駆体と
銅または銅化合物との混合物を、銅の融点以上の温度に
て加圧することを特徴とする窒化ほう素焼結体の製造方
法および垂直に並んだ板状の結晶子からなり、板状に発
達した窒化ほう素結晶子の面（ｃ面）が加圧軸に平行に
配列（ａ軸配向）しているａ軸配向性の窒化ほう素焼結
体を提供する。The present invention solves the above-mentioned problems by pressurizing a mixture of boron nitride or its precursor and copper or a copper compound at a temperature equal to or higher than the melting point of copper. the result from the manufacturing process and vertically aligned plate-like crystallites of boron nitride sinter, wherein, originating in a plate shape
The plane (c-plane) of the boron nitride crystallite reached is parallel to the pressure axis.
Aligned (a-axis oriented) a-axis oriented boron nitride sintering
Provide body .
【０００６】[0006]
【作用】この発明では、窒化ほう素の焼結体の製造に際
し、銅を助剤として用い、加圧下で銅の融点以上に加熱
する。この発明の窒化ほう素の焼結体の製造方法におい
ては、銅は、加熱中に銅を遊離するものであれば任意の
化合物であってもよい。窒化ほう素に対する銅の割合
は、大きいと熔融した銅により加圧の等方性が増し、ａ
軸配向の度合いを減じるので、配向性の強い製品を得る
ためには０．０１％〜２０％、望ましくは１％〜５％が
適当である。窒化ほう素は、結晶質、非晶質、乱層構
造、窒化ほう素前駆体のいずれであってもよいが、結晶
性が低いほど焼結の高密化が進み易く、ａ軸配向性の強
い製品が得られる。窒化ほう素前駆体の原料とこれを用
いた方法としては、以下のものがある。According to the present invention, when producing a sintered body of boron nitride, copper is used as an auxiliary agent and heated to a temperature equal to or higher than the melting point of copper under pressure. In the method for producing a sintered body of boron nitride according to the present invention, copper may be any compound as long as it releases copper during heating. If the ratio of copper to boron nitride is large, the isotropy of pressure increases due to the molten copper, and a
Since the degree of axial orientation is reduced, 0.01% to 20%, preferably 1% to 5% is appropriate for obtaining a product with strong orientation. Boron nitride may be any of crystalline, amorphous, turbostratic, and boron nitride precursors. However, the lower the crystallinity, the easier the sintering becomes, and the stronger the a-axis orientation. The product is obtained. As a raw material of the boron nitride precursor and a method using the same, there are the following.
【０００７】（イ）ほう酸と、尿素またはメラミン、ジ
シアンジアミド等の有機ほう窒化物を、２００°以上で
反応させると得られ、Ｂ，Ｎの外に酸素、炭素、窒素等
の原料成分が残留している。これを１１００°以上に加
熱するとＢＮが得られる。 （ロ）ボラジンや、塩化ほう素とアンモニアの反応で得
られる付加化合物等の水素を含む非酸化物の熱分解過程
で得られる。８００°以上で水素を失ってＢＮになる。(A) It is obtained by reacting boric acid with an organic boron nitride such as urea or melamine or dicyandiamide at a temperature of 200 ° or more. In addition to B and N, raw material components such as oxygen, carbon and nitrogen remain. ing. When this is heated to 1100 ° or more, BN is obtained. (B) Obtained during the thermal decomposition process of non-oxides containing hydrogen, such as borazine and adducts obtained by the reaction of boron chloride and ammonia. Above 800 °, hydrogen is lost to BN.
【０００８】銅と窒化ほう素の混合物については、機械
的に混合する方法と窒化ほう素の合成原料に銅の化合物
を加えておき窒化ほう素の生成反応中に銅を遊離させる
方法がある。特に後者は、窒化ほう素に銅が極めて微細
に分散したものが得られるので、助剤としての効果が大
きい。銅は、目的に応じ焼結後、酸処理または加熱気化
により除去する。For the mixture of copper and boron nitride, there are a mechanical mixing method and a method in which a copper compound is added to a raw material for synthesizing boron nitride, and copper is liberated during the boron nitride formation reaction. In particular, the latter has a great effect as an auxiliary agent, since an extremely fine dispersion of copper in boron nitride is obtained. After sintering, copper is removed by acid treatment or heat vaporization according to the purpose.
【０００９】この後者の方法は、たとえば、ほう素、尿
素および硝酸銅等を原料とし、この混合融液を熱分解す
ることにより窒化ほう素と銅の混合物を得、これを加圧
焼結する方法である。ほう酸と尿素はよく知られた窒化
ほう素合成の原料であり、銅はこれにたとえば硝酸銅の
形で混合される。銅化合物としては、酸化銅、水酸化
銅、及び硝酸、硫酸、炭酸、青酸等の無機酸の塩や、酢
酸等の有機酸の塩等が例示される。In the latter method, a mixture of boron nitride and copper is obtained by, for example, using boron, urea, copper nitrate and the like as raw materials, and thermally decomposing the mixed melt to obtain a mixture of boron nitride and copper. Is the way. Boric acid and urea are well-known raw materials for boron nitride synthesis, to which copper is mixed, for example, in the form of copper nitrate. Examples of the copper compound include copper oxide, copper hydroxide, salts of inorganic acids such as nitric acid, sulfuric acid, carbonic acid, and hydrocyanic acid, and salts of organic acids such as acetic acid.
【００１０】この混合物は、約１００℃の加熱で互いに
溶解し、均一混合融液を形成する。これを約２００℃に
保持すると青色にあわ立ちながら徐々に粘性を増して固
化し、銅を含む窒化ほう素前駆体が得られる。さらに、
石英管状炉によりアンモニア気流中で１１００℃に加熱
すると、銅が１μｍ以下の微粒子になって分散した銅色
をおびた乱層構造窒化ほう素の粉末が得られる。これを
焼結の出発物質とする。またここで、硝酸銅を増減する
ことにより焼結後の窒化ほう素の結晶化度および結晶配
向性の度合いを調節することができる。特に、配向性の
強い製品を得るには、銅が０．５％以上３％以下である
ことが望ましい。[0010] The mixtures are melted together by heating at about 100 ° C to form a homogeneous mixed melt. When it is kept at about 200 ° C., it gradually rises in viscosity while being blue and solidifies to obtain a boron nitride precursor containing copper. further,
When heated to 1100 ° C. in a flow of ammonia in a quartz tube furnace, a copper-colored turbostratic boron nitride powder in which copper is dispersed in fine particles of 1 μm or less is obtained. This is used as a starting material for sintering. Here, by increasing or decreasing the amount of copper nitrate, the degree of crystallinity and the degree of crystal orientation of boron nitride after sintering can be adjusted. In particular, in order to obtain a product with a strong orientation, it is desirable that copper is 0.5% or more and 3% or less.
【００１１】焼結は、出発物質を粉砕して内面に窒化ほ
う素を塗布した黒鉛型に充填し、加圧および加熱して行
うのが望ましい。焼結の温度は銅の融点以上であること
が必要であり、１３００°以上で急激に焼結が進むが、
温度が高すぎると窒化ほう素が分解するので、１０８５
℃〜２３００℃程度、好ましくは１５００℃以上、さら
に好ましくは１８００°以上である。加圧の圧力は高い
ほどよい。ただ、黒鉛型の強度による上限があるため、
後述の実施例では３０ＭＰａで行っている。加圧の雰囲
気は窒化ほう素が反応または分解しないものであれば良
く、窒素、アンモニア、不活性ガス等から選ばれる。The sintering is preferably carried out by pulverizing the starting material, filling it in a graphite mold coated with boron nitride on its inner surface, and applying pressure and heat. The sintering temperature must be equal to or higher than the melting point of copper.
If the temperature is too high, boron nitride will decompose,
C. to about 2300.degree. C., preferably 1500.degree. C. or more, more preferably 1800.degree. The higher the pressure, the better. However, there is an upper limit due to the strength of the graphite mold,
In the embodiment described later, the measurement is performed at 30 MPa. The pressurized atmosphere may be any atmosphere in which boron nitride does not react or decompose, and is selected from nitrogen, ammonia, inert gas, and the like.
【００１２】銅の作用は加熱により窒化ほう素の物質移
動を助け結晶化を促進することにあり、結晶化と同時に
焼結が進行する。この発明の方法では、銅を微細に分散
することが出来るためその効果が大きい。この発明の方
法により得られた焼結体は、従来とは異なり、板状に発
達した窒化ほう素結晶子の面（ｃ軸）が加圧軸に平行に
配列（ａ軸配向）している。また、酸化物の残存による
問題は全くない。さらに、焼結に際し加熱に用いる黒鉛
部材の酸化による消耗がなく、還元性条件下での焼結が
可能である。The function of copper is to promote the crystallization by promoting the mass transfer of boron nitride by heating, and sintering proceeds simultaneously with the crystallization. According to the method of the present invention, copper can be finely dispersed, so that the effect is large. In the sintered body obtained by the method of the present invention, the plane (c-axis) of the boron nitride crystallite developed in a plate shape is arranged parallel to the pressing axis (a-axis orientation), unlike the related art. . Further, there is no problem due to the remaining oxide. Furthermore, the graphite member used for heating during sintering is not consumed by oxidation, and sintering under reducing conditions is possible.
【００１３】焼結には、炭素材を共存させてもよい。こ
の場合には、黒鉛、乱層構造炭素、炭窒化ほう素、また
は、加熱により炭素を生成する蔗糖等の有機化合物が用
いられる。以下、実施例を示し、さらに詳しくこの発明
について説明する。For sintering, a carbon material may coexist. In this case, an organic compound such as graphite, turbostratic carbon, boron carbonitride, or sucrose that generates carbon by heating is used. Hereinafter, the present invention will be described in more detail with reference to Examples.
【００１４】[0014]
【実施例】実施例１ この発明の方法を用いて、実際に窒化ほう素焼結体を作
成した。この実施例においては、ほう酸と尿酸と硝酸銅
を重量比で１：２．５：０．０２の割合で混合し１３０
℃に加熱して融解した。引き続き２５０℃に２時間保持
すると、発泡しながら固化した。この固形物を軽く粉砕
しアンモニア気流中で１１００℃に加熱、３時間保持し
たところ、銅を０．１μｍ以下の微粒子で分散担持する
乱層構造窒化ほう素を得た。これをメノウ製の振動ミル
で粉砕して加圧焼結用の黒鉛型に充填し、窒素気流中で
３０ＭＰａに加圧しながら１９５０℃に加熱し１時間保
持した。 Example 1 A boron nitride sintered body was actually produced by using the method of the present invention. In this example, boric acid, uric acid and copper nitrate were mixed at a weight ratio of 1: 2.5: 0.02 and mixed.
Heated to ° C. to melt. Subsequently, when the temperature was maintained at 250 ° C. for 2 hours, it solidified while foaming. This solid was lightly pulverized, heated to 1100 ° C. in an ammonia stream, and held for 3 hours to obtain a turbostratic boron nitride having copper dispersed and supported by fine particles of 0.1 μm or less. This was pulverized by a vibrating mill made of agate and filled in a graphite mold for pressure sintering, heated to 1950 ° C. while being pressurized to 30 MPa in a nitrogen stream, and held for 1 hour.
【００１５】回収した焼結体の走査型電子顕微鏡写真を
図１に示す。また、この焼結体のＸ線回折測定図を図２
に示す。図１によれば、垂直に並んだ板状の結晶子から
なることがわかる。また、図２から結晶面（ｃ面）が加
圧軸に平行に配向（ａ軸配向）していることが分かっ
た。さらに、回収した焼結体の密度は９７％であった。実施例２ ほう酸と尿酸の重量比で１：２．５の混合物を実施例１
と同様な手順で加熱して、乱層構造窒化ほう素を得た。
これに、銅の粉末を重量比で６％加えてよく混合し、実
施例１と同様な手順で加圧焼結操作を行った結果、ａ軸
配向性焼結体を得た。しかし配向度は、実施例１のもの
に比べて小さかった。実施例３ ほう酸、尿素、サッカローズの混合物から合成した炭窒
化ほう素系粉末を銅を用いて加圧焼結した。このとき酸
化物の焼結助剤が炭素により還元される。FIG. 1 shows a scanning electron micrograph of the recovered sintered body. FIG. 2 shows an X-ray diffraction measurement diagram of the sintered body.
Shown in According to FIG. 1, it can be seen that it is composed of plate-like crystallites arranged vertically. In addition, it was found from FIG. 2 that the crystal plane (c-plane) was oriented parallel to the pressure axis (a-axis orientation). Further, the density of the recovered sintered body was 97%. Example 2 Example 1 was a mixture of boric acid and uric acid at a weight ratio of 1: 2.5.
Heating was performed in the same manner as in the above to obtain boron nitride having a turbostratic structure.
6% by weight of a copper powder was added thereto and mixed well, and a pressure sintering operation was performed in the same procedure as in Example 1. As a result, an a-axis oriented sintered body was obtained. However, the degree of orientation was smaller than that of Example 1. Example 3 Boron carbonitride-based powder synthesized from a mixture of boric acid, urea, and saccharose was pressure-sintered using copper. At this time, the oxide sintering aid is reduced by carbon.
【００１６】すなわち、ほう酸と尿酸と蔗糖と硝酸銅の
重量比を１：２．２：１：１の混合物を実施例１と同様
の手順で加熱処理したものは、乱層構造を有する炭窒化
ほう素であった。これを出発物質として実施例１と同様
な手順で加圧焼結操作を行ったところ、結晶性窒化ほう
素を含む炭窒化ほう素系物質からなる焼結体を得た。That is, a mixture obtained by heating a mixture of boric acid, uric acid, sucrose and copper nitrate in a weight ratio of 1: 2.2: 1: 1 in the same procedure as in Example 1 has a turbostratic structure. It was boron. Using this as a starting material, pressure sintering was performed in the same procedure as in Example 1 to obtain a sintered body made of a boron carbonitride-based material containing crystalline boron nitride.
【００１７】[0017]
【発明の効果】以上詳しく説明した通り、この発明にお
いて、平均粒径が数ミクロン以下でｃ面が加圧方向に配
向した結晶子からなる緻密な焼結体が得られるため、焼
結体の機械的強度の異方性が緩和される。また、炭素を
含む還元性条件下での焼結が可能なため、黒鉛等の加熱
部材の長寿命化がはかられ、炭窒化ほう素等の複合系で
の結晶化が可能になる。As described in detail above, in the present invention, a dense sintered body composed of crystallites having an average particle diameter of several microns or less and a c-plane oriented in the pressing direction can be obtained. The anisotropy of mechanical strength is reduced. In addition, since sintering can be performed under reducing conditions including carbon, the life of a heating member such as graphite can be prolonged, and crystallization in a composite system such as boron carbonitride becomes possible.
【図１】この発明の実施例において得られた窒化ほう素
の加圧軸に垂直な面の図面に代わる走査型電子顕微鏡写
真である。FIG. 1 is a scanning electron microscope photograph instead of a drawing of a plane perpendicular to a pressing axis of boron nitride obtained in an example of the present invention.
【図２】この発明の実施例において得られた窒化ほう素
の加圧軸に垂直の面で測定したＸ線回折図である。FIG. 2 is an X-ray diffraction diagram measured on a plane perpendicular to the pressing axis of the boron nitride obtained in the example of the present invention.
Claims (6)
銅化合物との混合物を、銅の融点以上の温度にて加圧す
ることを特徴とする窒化ほう素焼結体製造方法。1. A method for producing a boron nitride sintered body, comprising pressing a mixture of boron nitride or a precursor thereof and copper or a copper compound at a temperature equal to or higher than the melting point of copper.
加圧する請求項１の窒化ほう素焼結体方法。2. The method according to claim 1, wherein the reaction mixture of boric acid, urea and copper nitrate is pressurized.
圧する請求項１の窒化ほう素焼結体の製造方法。3. The method for producing a boron nitride sintered body according to claim 1, wherein the pressure is applied at a temperature not lower than the melting point of copper and not higher than 2300 ° C.
状に発達した窒化ほう素結晶子の面（ｃ面）が加圧軸に
平行に配列（ａ軸配向）しているａ軸配向性の窒化ほう
素焼結体。4. A plate comprising vertically arranged plate-like crystallites.
Plane of boron nitride crystallite (c-plane)
An a-axis oriented boron nitride sintered body arranged in parallel (a-axis orientation) .
合物とともに炭素質材が添加される炭窒化ほう素焼結体
の製造方法。5. The method according to claim 1, wherein a carbonaceous material is added together with copper or a copper compound.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7023484A JP2767393B2 (en) | 1995-01-18 | 1995-01-18 | Method for producing boron nitride sintered body |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7023484A JP2767393B2 (en) | 1995-01-18 | 1995-01-18 | Method for producing boron nitride sintered body |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08198682A JPH08198682A (en) | 1996-08-06 |
| JP2767393B2 true JP2767393B2 (en) | 1998-06-18 |
Family
ID=12111809
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7023484A Expired - Lifetime JP2767393B2 (en) | 1995-01-18 | 1995-01-18 | Method for producing boron nitride sintered body |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2767393B2 (en) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5837273B2 (en) * | 1981-05-18 | 1983-08-15 | 日本碍子株式会社 | Manufacturing method of cubic boron nitride sintered body |
-
1995
- 1995-01-18 JP JP7023484A patent/JP2767393B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08198682A (en) | 1996-08-06 |
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