WO2022158127A1 - Method for producing boron nitride - Google Patents

Method for producing boron nitride Download PDF

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WO2022158127A1
WO2022158127A1 PCT/JP2021/043982 JP2021043982W WO2022158127A1 WO 2022158127 A1 WO2022158127 A1 WO 2022158127A1 JP 2021043982 W JP2021043982 W JP 2021043982W WO 2022158127 A1 WO2022158127 A1 WO 2022158127A1
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boron nitride
melamine borate
melamine
borate
flux
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PCT/JP2021/043982
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French (fr)
Japanese (ja)
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勝弥 手嶋
哲也 山田
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国立大学法人信州大学
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
    • C01B21/064—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with boron

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  • the present invention relates to a method for producing boron nitride.
  • This application claims priority based on Japanese Patent Application No. 2021-007381 filed in Japan on January 20, 2021, the content of which is incorporated herein.
  • Boron nitride has high thermal conductivity and is chemically or thermally stable. For this reason, boron nitride is increasingly being used as a heat-conducting filler. Boron nitride can be produced by reacting a compound containing boron with a compound containing nitrogen.
  • Patent Literature 1 describes a method of producing hexagonal boron nitride primary particle aggregates by two-stage firing of melamine borate under specific conditions.
  • Boron nitride is known to have a large anisotropy of thermal conductivity due to its crystal structure and scale shape. Therefore, when filled into a resin as a thermally conductive filler, there is a problem that the thermal conductivity tends to decrease due to the orientation of the boron nitride in the resin. Further, when filling a resin with boron nitride as a filler, it is required to improve filling properties. From the viewpoint of improving filling properties, it is required to control the particle size of melamine borate.
  • the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a boron nitride production method capable of controlling the shape and size of boron nitride particles.
  • the present invention includes the following [1] to [4].
  • [1] A method for producing boron nitride, comprising a step of obtaining melamine borate, and a baking step of obtaining boron nitride by baking the melamine borate at a temperature of 1000° C. or more and 1700° C. or less in the presence of a flux. .
  • the flux is mixed with the melamine borate at a molar ratio (melamine borate/flux) of 1 or more and 4 or less, and then fired.
  • [1] or [2] The manufacturing method of the boron nitride as described in ].
  • [4] The method for producing boron nitride according to any one of [1] to [3], wherein the flux is lithium carbonate or lithium hydroxide.
  • FIG. 2 shows an X-ray diffraction pattern of melamine borate
  • 1 is a scanning electron micrograph of melamine borate.
  • 1 is a diagram showing an X-ray diffraction pattern of boron nitride produced in Example 1.
  • FIG. 1 is a scanning electron micrograph of boron nitride produced in Example 1.
  • FIG. 2 is a scanning electron micrograph of melamine borate produced in Example 2.
  • FIG. 4 is a scanning electron micrograph of boron nitride produced in Example 2.
  • FIG. 1 is a scanning electron micrograph of melamine borate
  • 1 is a diagram showing an X-ray diffraction pattern of boron nitride produced in Example 1.
  • FIG. 1 is a scanning electron micrograph of boron nitride produced in Example 1.
  • FIG. 2 is a scanning electron micrograph of melamine borate produced in Example 2.
  • FIG. 4 is a scanning electron micrograph of boron n
  • the method for producing boron nitride according to the present embodiment includes a step of obtaining melamine borate and a firing step of firing the melamine borate in the presence of a flux.
  • the present inventors have found that sintering melamine borate in the presence of a flux can produce boron nitride in which the particle size and shape of melamine borate are maintained.
  • the present invention is based on the technical idea of controlling the shape and size of the produced boron nitride particles within a desired range by controlling the shape and size of the melamine borate particles in the process of obtaining melamine borate. It depends.
  • Step of obtaining melamine borate Melamine borate can be obtained, for example, by recrystallizing melamine borate from a saturated aqueous solution containing boric acid and melamine.
  • saturated aqueous solution means a saturated aqueous solution containing boric acid and melamine.
  • the particle size and shape of the melamine borate are maintained. Therefore, the size and shape of melamine borate are controlled in order to obtain boron nitride of desired size and shape.
  • melamine borate when producing boron nitride with a particle size of about 5 ⁇ m or more and 10 ⁇ m or less, it is preferable to produce melamine borate with a particle size of about 5 ⁇ m or more and 10 ⁇ m or less.
  • the above particle size range can be changed as appropriate depending on the desired size of the boron nitride.
  • the range of the aspect ratio can be appropriately changed depending on the desired size of the boron nitride.
  • the size and shape of the melamine borate particles can be controlled by controlling the recrystallization conditions and post-treatment.
  • Conditions for recrystallization include heating and cooling conditions for a saturated aqueous solution or ultrasonic treatment conditions for a saturated aqueous solution.
  • a post-treatment a dry pulverization method or mechanical pulverization such as a ball mill can be used.
  • the step of obtaining melamine borate is a step of heating and cooling a saturated aqueous solution.
  • the step of obtaining melamine borate is a step of subjecting a saturated aqueous solution to ultrasonication followed by suction filtration.
  • the amount of boric acid is, for example, 1 g or more and 5 g or less, preferably 2 g or more and 4 g or less, per 100 mL of distilled water.
  • the amount of melamine is, for example, 0.5 g or more and 4 g or less, preferably 1 g or more and 3 g or less, per 100 mL of distilled water.
  • Crystals of melamine borate are deposited by allowing the saturated aqueous solution to cool.
  • An example of the cooling conditions is that the beaker containing the resulting saturated aqueous solution is immersed in a 1 L beaker filled with hot water of 50° C. or more and 100° C. or less, left at room temperature for about 12 hours or more and 24 hours or less, and gradually It is preferred to cool the saturated aqueous solution.
  • the resulting precipitate is dried to obtain melamine borate.
  • natural drying may be performed, or drying may be performed using a constant temperature bath at room temperature or 100° C. or less.
  • melamine borate particles having an elongated columnar shape are obtained.
  • the melamine borate particles have a minor axis diameter of about 5 ⁇ m to 10 ⁇ m. Also, the major axis diameter is about 10 ⁇ m to 2 cm.
  • Ultrasonic treatment and suction filtration step it is preferable to sonicate the saturated aqueous solution obtained by the same method as above.
  • an ultrasonic cleaning machine may be used for ultrasonic treatment. Crystals of melamine borate are precipitated by the ultrasonic treatment.
  • an ultrasonic washing machine can be used for ultrasonic treatment.
  • the shape and size of the produced melamine borate particles can be controlled.
  • the ultrasonic treatment crushes the columnar particles to obtain melamine borate particles each having a short axis diameter and a long axis diameter of several tens of ⁇ m.
  • Conditions for ultrasonic treatment include frequency and treatment time.
  • the frequency is preferably adjusted in the range of 20 kHz or more and 50 kHz or less.
  • the treatment time is preferably adjusted in the range of 1 minute or more and 10 minutes or less.
  • the combination of frequency and processing time is, for example, 20 kHz or more and 50 kHz or less and 1 minute or more and 10 minutes or less.
  • the shape and size of the produced melamine borate particles can be confirmed by observing them with a scanning electron microscope.
  • the ultrasonic treatment makes it easier to obtain melamine borate particles with an aspect ratio of about 1 to 1.5, which is the ratio of the short axis diameter to the long axis diameter.
  • the firing step is a step of firing melamine borate in the presence of a flux.
  • boron nitride can be produced while maintaining the shape and size of the melamine borate particles.
  • the firing temperature is 1000° C. or higher and 1700° C. or lower, preferably 1100° C. or higher and 1600° C. or lower, and more preferably 1200° C. or higher and 1500° C. or lower.
  • the firing temperature is within the above range, it is easy to obtain boron nitride that maintains the size and shape of melamine borate.
  • the firing temperature is equal to or higher than the above lower limit, crystal growth of boron nitride tends to proceed. If the firing temperature exceeds the above upper limit, the crystallization of boron nitride proceeds and it becomes easy to grow into scales. For this reason, in order to obtain particulate boron nitride, it is preferable to bake at a temperature of 1700° C. or lower.
  • the "firing temperature” means the maximum temperature of the atmosphere in the firing furnace in the firing process.
  • the duration of holding at the above firing temperature is preferably 30 minutes or more and 2 hours or less, and preferably 50 minutes or more and 90 minutes or less.
  • the firing process is preferably carried out under an inert gas atmosphere.
  • inert gas examples include nitrogen gas and argon gas.
  • the rate of temperature increase until reaching the firing temperature is 200°C/hour or more and 400°C/hour or less, preferably 250°C/hour or more and 350°C/hour or less.
  • the “heating rate” means the time from the time when the temperature rise in the firing device starts until the maximum holding temperature is reached, and the temperature at the time when the temperature rise in the firing furnace of the heating device starts. and the temperature difference up to the holding temperature.
  • the fired product may be washed with water.
  • the melamine borate is fired in the presence of a flux.
  • the flux is not particularly limited as long as it is commonly used.
  • one or more elements selected from the group consisting of Li, Na, K, and B hereinafter referred to as “M”) borate, M oxide, M nitrate, M chloride, M carbonate, M sulfate, M organic acid salt, M hydroxide, and M fluoride.
  • lithium borate lithium borate, sodium borate, and potassium borate can be used.
  • Boron oxide, sodium oxide, potassium oxide, and lithium oxide can be used as oxides of M.
  • Sodium nitrate can be used as the nitrate of M.
  • chlorides of M sodium chloride, potassium chloride, and lithium chloride can be used.
  • carbonate of M sodium carbonate, potassium carbonate, and lithium carbonate can be used.
  • sodium sulfate, potassium sulfate, and lithium sulfate can be used as the sulfate of M.
  • hydroxide of M sodium hydroxide, potassium hydroxide, and lithium hydroxide can be used.
  • fluoride of M sodium fluoride, potassium fluoride, and lithium fluoride can be used.
  • M organic acid salt M acetate, M oxalate, and M citrate can be used.
  • sodium acetate, potassium acetate, and lithium acetate can be used as the acetate of M.
  • sodium oxalate, potassium oxalate, and lithium oxalate can be used as the oxalate of M.
  • citrate of M sodium citrate, potassium citrate, and lithium citrate can be used.
  • the flux may be an ammonium salt of element M. Moreover, you may use together 2 or more types of said flux.
  • the element M is preferably one or more elements selected from the group consisting of Li, Na, and K, preferably Li or Na, and more preferably Li.
  • the flux is preferably a carbonate of the element M or a hydroxide of the element M, and more preferably lithium carbonate or lithium hydroxide.
  • the firing step it is preferable to mix and fire the flux at a molar ratio (melamine borate/flux) to melamine borate of 1 or more and 3 or less.
  • boron nitride crystals By firing in the presence of a flux, boron nitride crystals can be grown under low temperature conditions of 1700°C or less. As a result, boron nitride is less likely to grow into scales, and boron nitride in which the shape and size of melamine borate particles are maintained can be produced.
  • Boron nitride produced by the production method of the present embodiment maintains the shape and size of the particles of melamine borate as a raw material.
  • the boron nitride of the present embodiment is secondary particles that are aggregates of primary particles.
  • the secondary particles are porous and have fine pores with a pore size of about 10 nm.
  • the boron nitride of the present embodiment is, for example, secondary particles having an elongated columnar shape and having a short axis diameter of about 5 ⁇ m or more and 10 ⁇ m or less and a long axis diameter of about 10 ⁇ m or more and 2 cm or less.
  • the boron nitride of the present embodiment is, for example, secondary particles each having a short axis diameter and a long axis diameter of several tens of ⁇ m, and having an aspect ratio of about 1 to 1.5.
  • the boron nitride of the present embodiment has less anisotropy in thermal conductivity than conventional scaly boron nitride, so it can be inferred that the thermal conductivity of the entire thermal conductor is improved.
  • the size and shape of boron nitride particles can be controlled, it can be applied to a wide range of applications, such as thin insulating films with excellent thermal conductivity and interlayer insulating films for devices.
  • the resulting beaker containing the saturated aqueous solution was immersed in a 1 L beaker containing hot water at 80° C. and allowed to stand at room temperature for about 12 hours to gradually cool the saturated aqueous solution.
  • crystals of melamine borate precipitated.
  • the precipitated melamine borate crystals were taken out in a petri dish and allowed to stand at room temperature for 12 hours to air dry. Thus, a precipitate 1 was obtained.
  • melamine borate 1 had an elongated columnar shape with a minor axis diameter of about 5 ⁇ m to 10 ⁇ m.
  • a mixture 1 was obtained by mixing 2 mmol of melamine borate 1 and 1 mmol of lithium carbonate for 10 minutes. Mixture 1 was placed in a square carbon crucible and fired using a Keramax box electric furnace. The molar ratio of flux to melamine borate (melamine borate/flux) was two.
  • the temperature was raised to 1400° C. over 4 hours and 20 minutes at a temperature elevation rate of 300° C./hour, and held at 1400° C. for 1 hour. After that, the temperature was lowered to 0° C. over 4 hours and 20 minutes at a temperature lowering rate of 300° C./hour. Nitrogen gas was passed through at a flow rate of 0.2 L/min during all of the heating, holding at 1400° C., and cooling steps. As a result, a baked product 1 was obtained. A baked product 1 was obtained by washing the baked product 1 with water.
  • FIG. 3(a) shows the X-ray diffraction pattern of the baked product 1 before washing with water.
  • FIG. 3(b) shows the X-ray diffraction pattern of the fired product 1 after washing with water. No peak attributed to lithium carbonate was observed in both FIGS. 3(a) and 3(b).
  • FIG. 4(a) shows an SEM photograph (magnification: 2000 times) of boron nitride 1
  • FIG. 4(b) shows an SEM photograph (magnification: 20000 times).
  • the boron nitride 1 had an elongated columnar shape with a minor axis diameter of about 5 ⁇ m to 10 ⁇ m. That is, it was confirmed that the shape and size of melamine borate 1 were maintained.
  • melamine borate 1 has a porous structure with a plurality of pores with a pore diameter of about 10 nm.
  • the resulting saturated aqueous solution was ultrasonically treated for 5 minutes to precipitate crystals of melamine borate.
  • the obtained crystals were suction-filtered to obtain a deposit 2.
  • the X-ray diffraction pattern of the resulting precipitate 2 was obtained. The results confirmed that the deposit 2 was melamine borate.
  • FIG. 5(a) A SEM photograph (500x) of the obtained melamine borate 2 is shown in Fig. 5(a).
  • FIG. 5(b) A SEM photograph (1000 times) of the obtained melamine borate 2 is shown in FIG. 5(b).
  • melamine borate 2 had a particle shape, and the short axis diameter and long axis diameter of the particles were each about 20 ⁇ m.
  • the aspect ratio (minor axis diameter/major axis diameter) of melamine borate 2 was about 1.
  • Mixture 2 was obtained by mixing 4 mmol of melamine borate 2 and 2 mmol of lithium carbonate for 10 minutes. Mixture 2 was placed in a square carbon crucible and fired using a Keramax box electric furnace. The molar ratio of flux to melamine borate (melamine borate/flux) was two.
  • the temperature was raised to 1400° C. over 4 hours and 40 minutes at a temperature elevation rate of 300° C./hour, and held at 1400° C. for 1 hour. After that, the temperature was lowered to 0° C. over 4 hours and 20 minutes at a temperature lowering rate of 300° C./hour. Nitrogen gas was passed through at a flow rate of 0.2 L/min during all of the heating, holding at 1400° C., and cooling steps. As a result, a baked product 2 was obtained. The baked product 2 was washed with water to obtain the baked product 2.
  • FIG. 6(a) shows an SEM photograph (magnification: 1000 times) of boron nitride 2
  • FIG. 6(b) shows an SEM photograph (magnification: 2000 times).
  • the boron nitride 2 had a particle shape, and the minor axis diameter and the major axis diameter of the particles were each about 20 ⁇ m.
  • the aspect ratio (minor axis diameter/major axis diameter) of the boron nitride 2 was about 1. In other words, it was confirmed that the shape and size of melamine borate 2 were maintained.
  • FIG. 6(c) A SEM photograph of boron nitride 2 at 40,000 times is shown in FIG. 6(c). From FIG. 6(c), it was confirmed that the melamine borate 2 has a porous structure having a plurality of pores with a pore size of about 10 nm.

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Abstract

A method for producing boron nitride, said method comprising a step for obtaining melamine borate and a firing step for firing the melamine borate in the presence of a flux at a temperature of 1000-1700°C inclusive to give boron nitride.

Description

窒化ホウ素の製造方法Method for producing boron nitride
　本発明は、窒化ホウ素の製造方法に関する。
　本願は、２０２１年１月２０日に、日本に出願された特願２０２１－００７３８１号に基づき優先権を主張し、その内容をここに援用する。 The present invention relates to a method for producing boron nitride.
This application claims priority based on Japanese Patent Application No. 2021-007381 filed in Japan on January 20, 2021, the content of which is incorporated herein.
　窒化ホウ素は高い熱伝導性を有し、化学的又は熱的に安定である。このため、窒化ホウ素は熱伝導フィラーとしての利用が進んでいる。
　窒化ホウ素は、ホウ素を含む化合物と窒素を含む化合物とを反応させることにより製造できる。例えば特許文献１には、ホウ酸メラミンを特定の条件で二段焼成し、六方晶窒化ホウ素一次粒子凝集体を製造する方法が記載されている。 Boron nitride has high thermal conductivity and is chemically or thermally stable. For this reason, boron nitride is increasingly being used as a heat-conducting filler.
Boron nitride can be produced by reacting a compound containing boron with a compound containing nitrogen. For example, Patent Literature 1 describes a method of producing hexagonal boron nitride primary particle aggregates by two-stage firing of melamine borate under specific conditions.
特開２０１８－１０４２５３号公報JP 2018-104253 A
　窒化ホウ素は、結晶構造と鱗片形状に由来する熱伝導の異方性が大きいことが知られている。このため、熱伝導フィラーとして樹脂に充填した場合、樹脂中での窒化ホウ素の配向に起因して、熱伝導性が低下しやすいという課題があった。
　また、樹脂にフィラーとして窒化ホウ素を充填させる場合、充填性の向上が求められる。充填性を向上させる観点から、ホウ酸メラミンの粒子の大きさを制御することが求められる。 Boron nitride is known to have a large anisotropy of thermal conductivity due to its crystal structure and scale shape. Therefore, when filled into a resin as a thermally conductive filler, there is a problem that the thermal conductivity tends to decrease due to the orientation of the boron nitride in the resin.
Further, when filling a resin with boron nitride as a filler, it is required to improve filling properties. From the viewpoint of improving filling properties, it is required to control the particle size of melamine borate.
　本発明は上記事情に鑑みてなされたものであって、窒化ホウ素の粒子の形状と大きさを制御できる窒化ホウ素の製造方法を提供することを課題とする。 The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a boron nitride production method capable of controlling the shape and size of boron nitride particles.
　本発明は下記の［１］～［４］を包含する。
［１］ホウ酸メラミンを得る工程と、前記ホウ酸メラミンを融剤の存在下で１０００℃以上１７００℃以下の温度で焼成し、窒化ホウ素を得る焼成工程と、を備える、窒化ホウ素の製造方法。
［２］前記ホウ酸メラミンを得る工程は、ホウ酸とメラミンの飽和水溶液を超音波処理する工程を備える、［１］に記載の窒化ホウ素の製造方法。
［３］前記焼成工程において、前記ホウ酸メラミンに対する、前記融剤のモル比（ホウ酸メラミン／融剤）が、１以上４以下となる割合で混合して焼成する、［１］又は［２］に記載の窒化ホウ素の製造方法。
［４］前記融剤は、炭酸リチウム又は水酸化リチウムである、［１］～［３］のいずれか１つに記載の窒化ホウ素の製造方法。 The present invention includes the following [1] to [4].
[1] A method for producing boron nitride, comprising a step of obtaining melamine borate, and a baking step of obtaining boron nitride by baking the melamine borate at a temperature of 1000° C. or more and 1700° C. or less in the presence of a flux. .
[2] The method for producing boron nitride according to [1], wherein the step of obtaining the melamine borate includes a step of ultrasonicating a saturated aqueous solution of boric acid and melamine.
[3] In the firing step, the flux is mixed with the melamine borate at a molar ratio (melamine borate/flux) of 1 or more and 4 or less, and then fired. [1] or [2] ] The manufacturing method of the boron nitride as described in ].
[4] The method for producing boron nitride according to any one of [1] to [3], wherein the flux is lithium carbonate or lithium hydroxide.
　本発明によれば、窒化ホウ素の粒子の形状と大きさを制御できる窒化ホウ素の製造方法を提供することができる。 According to the present invention, it is possible to provide a method for producing boron nitride in which the shape and size of boron nitride particles can be controlled.
ホウ酸メラミンのＸ線回折パターンを示す図である。FIG. 2 shows an X-ray diffraction pattern of melamine borate; ホウ酸メラミンの走査型電子顕微鏡写真である。1 is a scanning electron micrograph of melamine borate. 実施例１で製造した窒化ホウ素のＸ線回折パターンを示す図である。1 is a diagram showing an X-ray diffraction pattern of boron nitride produced in Example 1. FIG. 実施例１で製造した窒化ホウ素の走査型電子顕微鏡写真である。1 is a scanning electron micrograph of boron nitride produced in Example 1. FIG. 実施例２で製造したホウ酸メラミンの走査型電子顕微鏡写真である。2 is a scanning electron micrograph of melamine borate produced in Example 2. FIG. 実施例２で製造した窒化ホウ素の走査型電子顕微鏡写真である。4 is a scanning electron micrograph of boron nitride produced in Example 2. FIG.
＜窒化ホウ素の製造方法＞
　本実施形態の窒化ホウ素の製造方法は、ホウ酸メラミンを得る工程と、ホウ酸メラミンを融剤の存在下で焼成する焼成工程とを備える。
　本発明者らの検討により、ホウ酸メラミンを融剤の存在下で焼成すると、ホウ酸メラミンの粒子の大きさや形状が維持された窒化ホウ素を製造できることが見いだされた。本発明は、ホウ酸メラミンを得る工程においてホウ酸メラミンの粒子の形状や大きさを制御することにより、製造される窒化ホウ素の粒子の形状と大きさを所望の範囲に制御するという技術思想に係る。 <Method for producing boron nitride>
The method for producing boron nitride according to the present embodiment includes a step of obtaining melamine borate and a firing step of firing the melamine borate in the presence of a flux.
The present inventors have found that sintering melamine borate in the presence of a flux can produce boron nitride in which the particle size and shape of melamine borate are maintained. The present invention is based on the technical idea of controlling the shape and size of the produced boron nitride particles within a desired range by controlling the shape and size of the melamine borate particles in the process of obtaining melamine borate. It depends.
［ホウ酸メラミンを得る工程］
　ホウ酸メラミンは、例えばホウ酸とメラミンとを含む飽和水溶液から、ホウ酸メラミンを再結晶することにより得られる。以下、「飽和水溶液」と記載する場合には、ホウ酸とメラミンとを含む飽和水溶液を意味する。 [Step of obtaining melamine borate]
Melamine borate can be obtained, for example, by recrystallizing melamine borate from a saturated aqueous solution containing boric acid and melamine. Hereinafter, the term "saturated aqueous solution" means a saturated aqueous solution containing boric acid and melamine.
　後の焼成工程においてホウ酸メラミンを融剤の存在下で焼成すると、ホウ酸メラミンの粒子の大きさや形状が維持される。このため、目的とする大きさや形状の窒化ホウ素を得るために、ホウ酸メラミンの大きさや形状を制御する。 When the melamine borate is fired in the presence of a flux in the subsequent firing step, the particle size and shape of the melamine borate are maintained. Therefore, the size and shape of melamine borate are controlled in order to obtain boron nitride of desired size and shape.
　例えば、粒子径が約５μｍ以上１０μｍ以下の窒化ホウ素を製造しようとする場合、粒子径が約５μｍ以上１０μｍ以下のホウ酸メラミンを製造することが好ましい。
　上記の粒子径の範囲は、目的とする窒化ホウ素の大きさによって適宜変更できる。 For example, when producing boron nitride with a particle size of about 5 μm or more and 10 μm or less, it is preferable to produce melamine borate with a particle size of about 5 μm or more and 10 μm or less.
The above particle size range can be changed as appropriate depending on the desired size of the boron nitride.
　柱状の細長い形状を有する二次粒子であって、短軸径と長軸径との比であるアスペクト比が約１～１．５である窒化ホウ素を製造しようとする場合、短軸径と長軸径との比であるアスペクト比が約１～１．５のホウ酸メラミンを製造することが好ましい。
　上記のアスペクト比の範囲は、目的とする窒化ホウ素の大きさによって適宜変更できる。 Secondary particles having a columnar elongated shape and having an aspect ratio, which is the ratio of the minor axis diameter to the major axis diameter, of about 1 to 1.5. It is preferable to produce melamine borate having an aspect ratio, which is the ratio to the shaft diameter, of about 1 to 1.5.
The range of the aspect ratio can be appropriately changed depending on the desired size of the boron nitride.
　ホウ酸メラミンの粒子の大きさや形状は、再結晶の条件制御や後処理を施すことにより、制御できる。再結晶の条件としては、飽和水溶液の加熱冷却条件又は飽和水溶液の超音波処理条件である。後処理としては、乾式粉砕法やボールミル等の機械的粉砕を用いることができる。 The size and shape of the melamine borate particles can be controlled by controlling the recrystallization conditions and post-treatment. Conditions for recrystallization include heating and cooling conditions for a saturated aqueous solution or ultrasonic treatment conditions for a saturated aqueous solution. As a post-treatment, a dry pulverization method or mechanical pulverization such as a ball mill can be used.
　本発明の一態様において、ホウ酸メラミンを得る工程は飽和水溶液を加熱冷却する工程である。
　本発明の一態様において、ホウ酸メラミンを得る工程は飽和水溶液を超音波処理した後に、吸引ろ過をする工程である。 In one aspect of the present invention, the step of obtaining melamine borate is a step of heating and cooling a saturated aqueous solution.
In one embodiment of the present invention, the step of obtaining melamine borate is a step of subjecting a saturated aqueous solution to ultrasonication followed by suction filtration.
（加熱冷却する工程）
　まず、約９５℃に加温された純水に、所定量のホウ酸を完全に溶解させる。次いで、所定量のメラミンを加え、攪拌し、メラミンを完全に溶解させる。この操作により、飽和水溶液が得られる。 (Process of heating and cooling)
First, a predetermined amount of boric acid is completely dissolved in pure water heated to about 95°C. Next, add a predetermined amount of melamine and stir to completely dissolve the melamine. This operation yields a saturated aqueous solution.
　ホウ酸の量は、例えば１００ｍＬの蒸留水に対し、１ｇ以上５ｇ以下であり、２ｇ以上４ｇ以下が好ましい。
　メラミンの量は、例えば１００ｍＬの蒸留水に対し、０．５ｇ以上４ｇ以下であり、１ｇ以上３ｇ以下が好ましい。 The amount of boric acid is, for example, 1 g or more and 5 g or less, preferably 2 g or more and 4 g or less, per 100 mL of distilled water.
The amount of melamine is, for example, 0.5 g or more and 4 g or less, preferably 1 g or more and 3 g or less, per 100 mL of distilled water.
　飽和水溶液を、放冷することにより、ホウ酸メラミンの結晶が析出する。
　放冷の条件の一例は、５０℃以上１００℃以下のお湯を入れた１Ｌビーカーに、得られた飽和水溶液を入れたビーカーを漬けて、室温で約１２時間以上２４時間以下放置し、徐々に飽和水溶液を冷却することが好ましい。 Crystals of melamine borate are deposited by allowing the saturated aqueous solution to cool.
An example of the cooling conditions is that the beaker containing the resulting saturated aqueous solution is immersed in a 1 L beaker filled with hot water of 50° C. or more and 100° C. or less, left at room temperature for about 12 hours or more and 24 hours or less, and gradually It is preferred to cool the saturated aqueous solution.
　得られた析出物を乾燥させ、ホウ酸メラミンが得られる。析出物を乾燥させる方法としては、自然乾燥させてもよく、室温又は１００℃以下の恒温槽を用いて乾燥させてもよい。 The resulting precipitate is dried to obtain melamine borate. As a method for drying the precipitate, natural drying may be performed, or drying may be performed using a constant temperature bath at room temperature or 100° C. or less.
　加熱冷却する工程により、柱状の細長い形状を有するホウ酸メラミンの粒子が得られる。このホウ酸メラミンの粒子は、短軸径は約５μｍ～１０μｍである。また、長軸径は、約１０μｍ～２ｃｍである。 Through the heating and cooling process, melamine borate particles having an elongated columnar shape are obtained. The melamine borate particles have a minor axis diameter of about 5 μm to 10 μm. Also, the major axis diameter is about 10 μm to 2 cm.
（超音波処理及び吸引ろ過工程）
　本実施形態において、上記と同様の方法により得た飽和水溶液を超音波処理することが好ましい。この場合には、例えば超音波洗浄機を用い、超音波処理すればよい。超音波処理により、ホウ酸メラミンの結晶が析出する。超音波処理には、例えば超音波洗浄機が使用できる。 (Ultrasonic treatment and suction filtration step)
In the present embodiment, it is preferable to sonicate the saturated aqueous solution obtained by the same method as above. In this case, for example, an ultrasonic cleaning machine may be used for ultrasonic treatment. Crystals of melamine borate are precipitated by the ultrasonic treatment. For ultrasonic treatment, for example, an ultrasonic washing machine can be used.
　超音波処理の条件を変更することにより、製造されるホウ酸メラミンの粒子の形状と大きさを制御できる。超音波処理することにより、柱状の粒子が破砕され、短軸径と長軸径がそれぞれ数十μｍであるホウ酸メラミンの粒子が得られる。 By changing the ultrasonic treatment conditions, the shape and size of the produced melamine borate particles can be controlled. The ultrasonic treatment crushes the columnar particles to obtain melamine borate particles each having a short axis diameter and a long axis diameter of several tens of μm.
　超音波処理の条件としては、周波数と処理時間が挙げられる。周波数は、２０ｋＨｚ以上５０ｋＨｚ以下の範囲に調整することが好ましい。処理時間は、１分間以上１０分間以下の範囲に調整することが好ましい。 Conditions for ultrasonic treatment include frequency and treatment time. The frequency is preferably adjusted in the range of 20 kHz or more and 50 kHz or less. The treatment time is preferably adjusted in the range of 1 minute or more and 10 minutes or less.
　周波数と処理時間の組み合わせは、例えば２０ｋＨｚ以上５０ｋＨｚ以下、且つ１分間以上１０分間以下である。 The combination of frequency and processing time is, for example, 20 kHz or more and 50 kHz or less and 1 minute or more and 10 minutes or less.
　超音波処理の時間を長くするほど、得られるホウ酸メラミンの大きさは小さくなり、アスペクト比が増加する。
　また超音波の周波数を高くするほど、得られるホウ酸メラミンの大きさは小さくなる。 The longer the sonication time, the smaller the size of the resulting melamine borate and the higher the aspect ratio.
Also, the higher the frequency of the ultrasonic waves, the smaller the size of the obtained melamine borate.
　例えば、１００ｍＬ飽和溶液中に１ｇのホウ酸メラミンを入れた場合には、消費電力４３０Ｗ、高周波出力３００ｗ、発振周波数３８ｋＨｚで５分間の超音波処理をすると、粒径が数十μｍであるホウ酸メラミンの粒子が得られる。 For example, when 1 g of melamine borate is added to 100 mL of saturated solution, when ultrasonic treatment is performed for 5 minutes at power consumption of 430 W, high frequency output of 300 W, and oscillation frequency of 38 kHz, the particle size of boric acid is several tens of μm. Particles of melamine are obtained.
　超音波処理の後、得られた結晶を吸引ろ過して、ホウ酸メラミンの粒子を得ることが好ましい。 After the ultrasonic treatment, it is preferable to suction-filter the obtained crystals to obtain melamine borate particles.
　製造されたホウ酸メラミンの粒子の形状及び大きさは、走査型電子顕微鏡により観察することで確認できる。 The shape and size of the produced melamine borate particles can be confirmed by observing them with a scanning electron microscope.
　超音波処理をすることにより、短軸径と長軸径との比であるアスペクト比が約１～１．５であるホウ酸メラミンの粒子が得られやすくなる。 The ultrasonic treatment makes it easier to obtain melamine borate particles with an aspect ratio of about 1 to 1.5, which is the ratio of the short axis diameter to the long axis diameter.
［焼成工程］
　焼成工程は、ホウ酸メラミンを融剤の存在下で焼成する工程である。
　ホウ酸メラミンを融剤の存在下で焼成することにより、ホウ酸メラミンの粒子の形状と大きさを維持した窒化ホウ素を製造することができる。 [Baking process]
The firing step is a step of firing melamine borate in the presence of a flux.
By firing melamine borate in the presence of a flux, boron nitride can be produced while maintaining the shape and size of the melamine borate particles.
　焼成温度は、１０００℃以上１７００℃以下であり、１１００℃以上１６００℃以下が好ましく、１２００℃以上１５００℃以下がより好ましい。
　焼成温度が上記範囲内であると、ホウ酸メラミンの大きさと形状を維持した窒化ホウ素が得られやすい。
　焼成温度が上記下限値以上であると、窒化ホウ素の結晶成長が進みやすい。
　焼成温度が上記上限値を超えると、窒化ホウ素の結晶化が進み鱗片状に成長しやすくなる。このため、粒子状の窒化ホウ素を得るためには、１７００℃以下の温度で焼成することが好ましい。 The firing temperature is 1000° C. or higher and 1700° C. or lower, preferably 1100° C. or higher and 1600° C. or lower, and more preferably 1200° C. or higher and 1500° C. or lower.
When the firing temperature is within the above range, it is easy to obtain boron nitride that maintains the size and shape of melamine borate.
When the firing temperature is equal to or higher than the above lower limit, crystal growth of boron nitride tends to proceed.
If the firing temperature exceeds the above upper limit, the crystallization of boron nitride proceeds and it becomes easy to grow into scales. For this reason, in order to obtain particulate boron nitride, it is preferable to bake at a temperature of 1700° C. or lower.
　本実施形態において「焼成温度」とは、焼成工程における焼成炉内雰囲気の保持温度の最高温度を意味する。 In the present embodiment, the "firing temperature" means the maximum temperature of the atmosphere in the firing furnace in the firing process.
　上記の焼成温度で保持する時間は、３０分間以上２時間以下が好ましく、５０分間以上９０分間以下が好ましい。 The duration of holding at the above firing temperature is preferably 30 minutes or more and 2 hours or less, and preferably 50 minutes or more and 90 minutes or less.
　本実施形態において、焼成工程は不活性ガスの雰囲気下で実施することが好ましい。不活性ガスとしては、窒素ガス又はアルゴンガスが挙げられる。 In this embodiment, the firing process is preferably carried out under an inert gas atmosphere. Examples of inert gas include nitrogen gas and argon gas.
　焼成工程において、焼成温度に達するまでの昇温速度は、２００℃／時間以上４００℃／時間以下が挙げられ、２５０℃／時間以上３５０℃／時間以下が好ましい。 In the firing step, the rate of temperature increase until reaching the firing temperature is 200°C/hour or more and 400°C/hour or less, preferably 250°C/hour or more and 350°C/hour or less.
　本実施形態において「昇温速度」とは、焼成装置において昇温を開始した時間から、最高保持温度に達するまでの時間と、昇温装置の焼成炉内の昇温開始時の温度から細孔保持温度までの温度差と、から算出される。 In the present embodiment, the “heating rate” means the time from the time when the temperature rise in the firing device starts until the maximum holding temperature is reached, and the temperature at the time when the temperature rise in the firing furnace of the heating device starts. and the temperature difference up to the holding temperature.
　焼成後、得られた焼成品を水洗してもよい。 After firing, the fired product may be washed with water.
　焼成工程において、ホウ酸メラミンを融剤（フラックス）の存在下で焼成する。
　フラックスとして、通常用いられるものであれば特に限定されない。
　本実施形態においては、Ｌｉ、Ｎａ、Ｋ、及びＢからなる群より選ばれる１種以上の元素（以下、「Ｍ」と称する。）のホウ酸塩、Ｍの酸化物、Ｍの硝酸塩、Ｍの塩化物、Ｍの炭酸塩、Ｍの硫酸塩、Ｍの有機酸塩、Ｍの水酸化物、Ｍのフッ化物が挙げられる。 In the firing step, the melamine borate is fired in the presence of a flux.
The flux is not particularly limited as long as it is commonly used.
In the present embodiment, one or more elements selected from the group consisting of Li, Na, K, and B (hereinafter referred to as “M”) borate, M oxide, M nitrate, M chloride, M carbonate, M sulfate, M organic acid salt, M hydroxide, and M fluoride.
　Ｍのホウ酸塩としては、ホウ酸リチウム、ホウ酸ナトリウム、ホウ酸カリウムが使用できる。 As the borate of M, lithium borate, sodium borate, and potassium borate can be used.
　Ｍの酸化物としては、酸化ホウ素、酸化ナトリウム、酸化カリウム、酸化リチウムが使用できる。 Boron oxide, sodium oxide, potassium oxide, and lithium oxide can be used as oxides of M.
　Ｍの硝酸塩としては、硝酸ナトリウムが使用できる。 Sodium nitrate can be used as the nitrate of M.
　Ｍの塩化物としては、塩化ナトリウム、塩化カリウム、塩化リチウムが使用できる。 As chlorides of M, sodium chloride, potassium chloride, and lithium chloride can be used.
　Ｍの炭酸塩としては、炭酸ナトリウム、炭酸カリウム、炭酸リチウムが使用できる。 As the carbonate of M, sodium carbonate, potassium carbonate, and lithium carbonate can be used.
　Ｍの硫酸塩としては、硫酸ナトリウム、硫酸カリウム、硫酸リチウムが使用できる。 As the sulfate of M, sodium sulfate, potassium sulfate, and lithium sulfate can be used.
　Ｍの水酸化物としては、水酸化ナトリウム、水酸化カリウム、水酸化リチウムが使用できる。 As the hydroxide of M, sodium hydroxide, potassium hydroxide, and lithium hydroxide can be used.
　Ｍのフッ化物としては、フッ化ナトリウム、フッ化カリウム、フッ化リチウムが使用できる。 As the fluoride of M, sodium fluoride, potassium fluoride, and lithium fluoride can be used.
　Ｍの有機酸塩としては、Ｍの酢酸塩、Ｍのシュウ酸塩、Ｍのクエン酸塩が使用できる。 As the M organic acid salt, M acetate, M oxalate, and M citrate can be used.
　Ｍの酢酸塩としては、酢酸ナトリウム、酢酸カリウム、酢酸リチウムが使用できる。 As the acetate of M, sodium acetate, potassium acetate, and lithium acetate can be used.
　Ｍのシュウ酸塩としては、シュウ酸ナトリウム、シュウ酸カリウム、シュウ酸リチウムが使用できる。 As the oxalate of M, sodium oxalate, potassium oxalate, and lithium oxalate can be used.
　Ｍのクエン酸塩としては、クエン酸ナトリウム、クエン酸カリウム、クエン酸リチウムが使用できる。 As the citrate of M, sodium citrate, potassium citrate, and lithium citrate can be used.
　フラックスは、元素Ｍのアンモニウム塩であってもよい。また、上記のフラックスを２種以上併用してもよい。 The flux may be an ammonium salt of element M. Moreover, you may use together 2 or more types of said flux.
　本実施形態において、元素ＭはＬｉ、Ｎａ、及びＫからなる群より選ばれる１種以上の元素であることが好ましく、Ｌｉ又はＮａが好ましく、Ｌｉがさらに好ましい。
　本実施形態において、フラックスは元素Ｍの炭酸塩、元素Ｍの水酸化物が好ましく、炭酸リチウム又は水酸化リチウムを用いることがより好ましい。 In this embodiment, the element M is preferably one or more elements selected from the group consisting of Li, Na, and K, preferably Li or Na, and more preferably Li.
In this embodiment, the flux is preferably a carbonate of the element M or a hydroxide of the element M, and more preferably lithium carbonate or lithium hydroxide.
　焼成工程において、ホウ酸メラミンに対する、融剤のモル比（ホウ酸メラミン／融剤）が、１以上３以下となる割合で混合して焼成することが好ましい。 In the firing step, it is preferable to mix and fire the flux at a molar ratio (melamine borate/flux) to melamine borate of 1 or more and 3 or less.
　融剤（フラックス）の存在下で焼成することにより、１７００℃以下の低い温度条件で窒化ホウ素の結晶を育成することができる。これにより、窒化ホウ素が鱗片状に成長しにくく、ホウ酸メラミンの粒子の形状と大きさを維持した窒化ホウ素を製造することができる。 By firing in the presence of a flux, boron nitride crystals can be grown under low temperature conditions of 1700°C or less. As a result, boron nitride is less likely to grow into scales, and boron nitride in which the shape and size of melamine borate particles are maintained can be produced.
＜窒化ホウ素＞
　本実施形態の製造方法により製造される窒化ホウ素は、原料であるホウ酸メラミンの粒子の形状と大きさが維持されている。
　本実施形態の窒化ホウ素は一次粒子の凝集体である二次粒子である。二次粒子は多孔質であり、孔径が約１０ｎｍの微細な孔を備える。 <Boron nitride>
Boron nitride produced by the production method of the present embodiment maintains the shape and size of the particles of melamine borate as a raw material.
The boron nitride of the present embodiment is secondary particles that are aggregates of primary particles. The secondary particles are porous and have fine pores with a pore size of about 10 nm.
　本実施形態の窒化ホウ素は、例えば柱状の細長い形状を有する二次粒子であって、短軸径が約５μｍ以上１０μｍ以下、長軸径が約１０μｍ以上２ｃｍ以下である粒子である。
　本実施形態の窒化ホウ素は、例えば短軸径と長軸径がそれぞれ数十μｍである二次粒子であって、アスペクト比が約１～１．５の粒子である。 The boron nitride of the present embodiment is, for example, secondary particles having an elongated columnar shape and having a short axis diameter of about 5 μm or more and 10 μm or less and a long axis diameter of about 10 μm or more and 2 cm or less.
The boron nitride of the present embodiment is, for example, secondary particles each having a short axis diameter and a long axis diameter of several tens of μm, and having an aspect ratio of about 1 to 1.5.
　本実施形態の窒化ホウ素は、従来の鱗片状の窒化ホウ素に比べて熱伝導の異方性が小さいため、熱伝導体全体としての熱伝導性が向上すると推察できる。また、窒化ホウ素の粒子の大きさと形状を制御できるため、例えば熱伝導性に優れた薄い絶縁膜や、デバイスの層間絶縁膜など、幅広く応用できる。 The boron nitride of the present embodiment has less anisotropy in thermal conductivity than conventional scaly boron nitride, so it can be inferred that the thermal conductivity of the entire thermal conductor is improved. In addition, since the size and shape of boron nitride particles can be controlled, it can be applied to a wide range of applications, such as thin insulating films with excellent thermal conductivity and interlayer insulating films for devices.
　以下、実施例により本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。 The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.
＜実施例１＞
［ホウ酸メラミンを得る工程］
　８０℃まで加熱した蒸留水１００ｍＬに、ホウ酸３ｇを添加し、攪拌して完全に溶解させた。次いで、２ｇのメラミンを添加し、攪拌して完全に溶解させた。攪拌にはスターラーを使用した。これにより、ホウ酸とメラミンの飽和水溶液を得た。 <Example 1>
[Step of obtaining melamine borate]
3 g of boric acid was added to 100 mL of distilled water heated to 80° C. and completely dissolved by stirring. 2 g of melamine was then added and completely dissolved by stirring. A stirrer was used for stirring. This gave a saturated aqueous solution of boric acid and melamine.
　８０℃のお湯を入れた１Ｌビーカーに、得られた飽和水溶液を入れたビーカーを漬けて、室温で約１２時間放置し、徐々に飽和水溶液を冷却した。冷却により、ホウ酸メラミンの結晶が析出した。
　析出したホウ酸メラミンの結晶をシャーレに取り出して、室温で１２時間放置し、自然乾燥させた。これにより、析出物１を得た。 The resulting beaker containing the saturated aqueous solution was immersed in a 1 L beaker containing hot water at 80° C. and allowed to stand at room temperature for about 12 hours to gradually cool the saturated aqueous solution. Upon cooling, crystals of melamine borate precipitated.
The precipitated melamine borate crystals were taken out in a petri dish and allowed to stand at room temperature for 12 hours to air dry. Thus, a precipitate 1 was obtained.
　得られた析出物１のＸ線回折パターンを得た。その結果を図１（ａ）に示す。 The X-ray diffraction pattern of the resulting precipitate 1 was obtained. The results are shown in FIG. 1(a).
　図１（ｂ）に示すように、粉末Ｘ線回折データベース（ＩＣＤＤ）と参照したところ、ＩＣＤＤのＮｏ０５０－２３８４のＣ４Ｈ３ＮＯ２であることが確認できた。 As shown in FIG. 1(b), when referring to the powder X-ray diffraction database (ICDD), it was confirmed to be C 4 H 3 NO 2 of ICDD No. 050-2384.
　さらに、図１（ｃ）に示すように、ＩＣＤＤのＮｏ０７６－６９４９のホウ酸メラミンであることが確認できた。図１（ｃ）の結果から、析出物１はホウ酸メラミン１であることが確認できた。 Furthermore, as shown in Fig. 1(c), it was confirmed to be ICDD No076-6949 melamine borate. From the results of FIG. 1(c), it was confirmed that the deposit 1 was melamine borate 1.
　得られたホウ酸メラミン１のＳＥＭ写真（倍率３０００倍）を図２に示す。図２に示すように、ホウ酸メラミン１は、柱状の細長い形状を有し、短軸径は約５μｍ～１０μｍであった。 A SEM photograph (3000x magnification) of the obtained melamine borate 1 is shown in FIG. As shown in FIG. 2, melamine borate 1 had an elongated columnar shape with a minor axis diameter of about 5 μm to 10 μm.
［焼成工程］
　２ｍｍｏｌのホウ酸メラミン１と、１ｍｍｏｌの炭酸リチウムとを１０分間混合し、混合物１を得た。混合物１を角型カーボンるつぼに入れ、ケラマックス箱形電気炉を用いて焼成した。ホウ酸メラミンに対する、融剤のモル比（ホウ酸メラミン／融剤）は２であった。 [Baking process]
A mixture 1 was obtained by mixing 2 mmol of melamine borate 1 and 1 mmol of lithium carbonate for 10 minutes. Mixture 1 was placed in a square carbon crucible and fired using a Keramax box electric furnace. The molar ratio of flux to melamine borate (melamine borate/flux) was two.
　まず、昇温速度３００℃／時間で４時間２０分かけて１４００℃まで昇温し、１４００℃で１時間保持した。その後、降温速度３００℃／時間で４時間２０分かけて０℃まで降温した。昇温、１４００℃での保持、及び降温工程のすべてにおいて、０．２Ｌ／分間の流量で窒素ガスを通気した。
　これにより、焼成物１得た。焼成物１を水洗し、焼成品１を得た。 First, the temperature was raised to 1400° C. over 4 hours and 20 minutes at a temperature elevation rate of 300° C./hour, and held at 1400° C. for 1 hour. After that, the temperature was lowered to 0° C. over 4 hours and 20 minutes at a temperature lowering rate of 300° C./hour. Nitrogen gas was passed through at a flow rate of 0.2 L/min during all of the heating, holding at 1400° C., and cooling steps.
As a result, a baked product 1 was obtained. A baked product 1 was obtained by washing the baked product 1 with water.
　得られた焼成品１のＸ線回折パターンを得た。図３（ａ）に、水洗前の焼成物１のＸ線回折パターンを示す。図３（ｂ）に水洗後の焼成品１のＸ線回折パターンを示す。図３（ａ）、（ｂ）ともに、炭酸リチウムに帰属するピークは確認されなかった。 An X-ray diffraction pattern of the obtained fired product 1 was obtained. FIG. 3(a) shows the X-ray diffraction pattern of the baked product 1 before washing with water. FIG. 3(b) shows the X-ray diffraction pattern of the fired product 1 after washing with water. No peak attributed to lithium carbonate was observed in both FIGS. 3(a) and 3(b).
　図３（ｃ）に示すように、ＩＣＤＤと参照したところ、ＩＣＤＤのＮｏ０３４－０４２１である窒化ホウ素であることが確認できた。図３（ｃ）の結果から、焼成品１は窒化ホウ素１であることが確認できた。 As shown in FIG. 3(c), when referring to ICDD, it was confirmed that it was boron nitride, which is ICDD No. 034-0421. From the results of FIG. 3(c), it was confirmed that the fired product 1 was boron nitride 1.
　図４（ａ）に、窒化ホウ素１のＳＥＭ写真（倍率２０００倍）を、図４（ｂ）にＳＥＭ写真（倍率２００００倍）をそれぞれ示す。図４（ａ）から、窒化ホウ素１は、柱状の細長い形状を有し、短軸径は約５μｍ～１０μｍであった。つまり、ホウ酸メラミン１の形状と大きさが維持されていることが確認できた。 FIG. 4(a) shows an SEM photograph (magnification: 2000 times) of boron nitride 1, and FIG. 4(b) shows an SEM photograph (magnification: 20000 times). As can be seen from FIG. 4(a), the boron nitride 1 had an elongated columnar shape with a minor axis diameter of about 5 μm to 10 μm. That is, it was confirmed that the shape and size of melamine borate 1 were maintained.
　図４（ｂ）から、ホウ酸メラミン１は、孔径が約１０ｎｍ程度の孔を複数備える多孔質構造であることが確認できた。 From FIG. 4(b), it was confirmed that melamine borate 1 has a porous structure with a plurality of pores with a pore diameter of about 10 nm.
＜実施例２＞
［ホウ酸メラミンを得る工程］
　８０℃まで加熱した蒸留水１００ｍＬに、ホウ酸３ｇを添加し、攪拌して完全に溶解させた。次いで、２ｇのメラミンを添加し、攪拌して完全に溶解させた。攪拌にはスターラーを使用した。これにより、ホウ酸とメラミンの飽和水溶液を得た。 <Example 2>
[Step of obtaining melamine borate]
3 g of boric acid was added to 100 mL of distilled water heated to 80° C. and completely dissolved by stirring. 2 g of melamine was then added and completely dissolved by stirring. A stirrer was used for stirring. This gave a saturated aqueous solution of boric acid and melamine.
　得られた飽和水溶液を５分間超音波処理し、ホウ酸メラミンの結晶を析出させた。得られた結晶を吸引ろ過し、析出物２を得た。 The resulting saturated aqueous solution was ultrasonically treated for 5 minutes to precipitate crystals of melamine borate. The obtained crystals were suction-filtered to obtain a deposit 2.
　得られた析出物２のＸ線回折パターンを得た。その結果を析出物２はホウ酸メラミンであることを確認した。 The X-ray diffraction pattern of the resulting precipitate 2 was obtained. The results confirmed that the deposit 2 was melamine borate.
　得られたホウ酸メラミン２のＳＥＭ写真（５００倍）を図５（ａ）に示す。得られたホウ酸メラミン２のＳＥＭ写真（１０００倍）を図５（ｂ）に示す。図５（ａ）に示すように、ホウ酸メラミン２は、粒子形状を有し、粒子の短軸径と長軸径はそれぞれ約２０μｍであった。また、ホウ酸メラミン２のアスペクト比（短軸径／長軸径）は約１であった。 A SEM photograph (500x) of the obtained melamine borate 2 is shown in Fig. 5(a). A SEM photograph (1000 times) of the obtained melamine borate 2 is shown in FIG. 5(b). As shown in FIG. 5(a), melamine borate 2 had a particle shape, and the short axis diameter and long axis diameter of the particles were each about 20 μm. The aspect ratio (minor axis diameter/major axis diameter) of melamine borate 2 was about 1.
［焼成工程］
　４ｍｍｏｌのホウ酸メラミン２と、２ｍｍｏｌの炭酸リチウムとを１０分間混合し、混合物２を得た。混合物２を角型カーボンるつぼに入れ、ケラマックス箱形電気炉を用いて焼成した。ホウ酸メラミンに対する、融剤のモル比（ホウ酸メラミン／融剤）は２であった。 [Baking process]
Mixture 2 was obtained by mixing 4 mmol of melamine borate 2 and 2 mmol of lithium carbonate for 10 minutes. Mixture 2 was placed in a square carbon crucible and fired using a Keramax box electric furnace. The molar ratio of flux to melamine borate (melamine borate/flux) was two.
　まず、昇温速度３００℃／時間で４時間４０分かけて１４００℃まで昇温し、１４００℃で１時間保持した。その後、降温速度３００℃／時間で４時間２０分かけて０℃まで降温した。昇温、１４００℃での保持、及び降温工程のすべてにおいて、０．２Ｌ／分間の流量で窒素ガスを通気した。
　これにより、焼成物２得た。焼成物２を水洗し、焼成品２を得た。 First, the temperature was raised to 1400° C. over 4 hours and 40 minutes at a temperature elevation rate of 300° C./hour, and held at 1400° C. for 1 hour. After that, the temperature was lowered to 0° C. over 4 hours and 20 minutes at a temperature lowering rate of 300° C./hour. Nitrogen gas was passed through at a flow rate of 0.2 L/min during all of the heating, holding at 1400° C., and cooling steps.
As a result, a baked product 2 was obtained. The baked product 2 was washed with water to obtain the baked product 2.
　得られた焼成品２のＸ線回折パターンを得た。これにより焼成品２は窒化ホウ素２であることが確認できた。 An X-ray diffraction pattern of the obtained fired product 2 was obtained. As a result, it was confirmed that the fired product 2 was boron nitride 2 .
　図６（ａ）に、窒化ホウ素２のＳＥＭ写真（倍率１０００倍）を、図６（ｂ）にＳＥＭ写真（倍率２０００倍）をそれぞれ示す。
　図６（ａ）から、窒化ホウ素２は、粒子形状を有し、粒子の短軸径と長軸径はそれぞれ約２０μｍであった。また、窒化ホウ素２のアスペクト比（短軸径／長軸径）は約１であった。つまり、ホウ酸メラミン２の形状と大きさが維持されていることが確認できた。 FIG. 6(a) shows an SEM photograph (magnification: 1000 times) of boron nitride 2, and FIG. 6(b) shows an SEM photograph (magnification: 2000 times).
From FIG. 6(a), the boron nitride 2 had a particle shape, and the minor axis diameter and the major axis diameter of the particles were each about 20 μm. Moreover, the aspect ratio (minor axis diameter/major axis diameter) of the boron nitride 2 was about 1. In other words, it was confirmed that the shape and size of melamine borate 2 were maintained.
　図６（ｃ）に４００００倍の窒化ホウ素２のＳＥＭ写真を示す。図６（ｃ）から、ホウ酸メラミン２は、孔径が約１０ｎｍ程度の孔を複数備える多孔質構造であることが確認できた。 A SEM photograph of boron nitride 2 at 40,000 times is shown in FIG. 6(c). From FIG. 6(c), it was confirmed that the melamine borate 2 has a porous structure having a plurality of pores with a pore size of about 10 nm.

Claims (4)

  1. 　ホウ酸メラミンを得る工程と、
    　前記ホウ酸メラミンを融剤の存在下で１０００℃以上１７００℃以下の温度で焼成し、窒化ホウ素を得る焼成工程と、を備える、窒化ホウ素の製造方法。     obtaining melamine borate;
    a firing step of firing the melamine borate at a temperature of 1000° C. or higher and 1700° C. or lower in the presence of a flux to obtain boron nitride.
  2. 　前記ホウ酸メラミンを得る工程は、ホウ酸とメラミンの飽和水溶液を超音波処理する工程を備える、請求項１に記載の窒化ホウ素の製造方法。 The method for producing boron nitride according to claim 1, wherein the step of obtaining melamine borate comprises a step of ultrasonicating a saturated aqueous solution of boric acid and melamine.
  3. 　前記焼成工程において、前記ホウ酸メラミンに対する、前記融剤のモル比（ホウ酸メラミン／融剤）が、１以上４以下となる割合で混合して焼成する、請求項１又は２に記載の窒化ホウ素の製造方法。 The nitriding according to claim 1 or 2, wherein in the firing step, the flux is mixed with the melamine borate at a molar ratio (melamine borate/flux) of 1 or more and 4 or less and fired. A method for producing boron.
  4. 　前記融剤は、炭酸リチウム又は水酸化リチウムである、請求項１～３のいずれか１項に記載の窒化ホウ素の製造方法。 The method for producing boron nitride according to any one of claims 1 to 3, wherein the flux is lithium carbonate or lithium hydroxide.
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