US20180230012A1 - Method of producing spherical boron nitride fine particles - Google Patents
Method of producing spherical boron nitride fine particles Download PDFInfo
- Publication number
- US20180230012A1 US20180230012A1 US15/955,211 US201815955211A US2018230012A1 US 20180230012 A1 US20180230012 A1 US 20180230012A1 US 201815955211 A US201815955211 A US 201815955211A US 2018230012 A1 US2018230012 A1 US 2018230012A1
- Authority
- US
- United States
- Prior art keywords
- boron nitride
- ammonia
- fine particles
- nitride fine
- gas
- 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.)
- Abandoned
Links
Images
Classifications
-
- 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
- C01B21/0646—Preparation by pyrolysis of boron and nitrogen containing compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Definitions
- the present invention relates to a spherical boron nitride fine particle well suited for use as a highly thermoconductive filler or the like, and a production method thereof.
- boron nitride Hexagonal boron nitride (hereinafter called “boron nitride”), because of having lubrication capability, high thermal conductivity and insulation capability, is now widely used as releasing agents for solid lubricants, molten glasses and aluminum or the like as well as fillers for thermal radiation materials.
- boron nitride While generally available boron nitride has an average particle diameter of a few ⁇ m to 20 ⁇ m, some resin substrates for printed wiring boards and flexible copper-clad laminated sheets have a thickness of the order of several tens ⁇ m, and large average particle diameters of boron nitride result in poor dispersability in resins, failing to obtain smooth surfaces, or with that boron nitride dispersed, there are hard spots appearing, often making it impossible to keep the strength of the resin layer high. For these reasons, there is mounting demand for boron nitride fine particles of the submicron order (0.1 ⁇ m).
- the boron nitride must be of high purity and high crystallinity, and the same goes for boron nitrite fine particles on the submicron order (0.1 ⁇ m).
- the boron nitride has a characteristic scaly shape, and its thermal properties are overwhelmingly better in the major or minor diameter direction than in the thickness or perpendicular direction. For this reason, the thermal properties of a composite material having boron nitride filled or packed in a resin such as silicone are considerably affected by the directionality of boron nitride fine particles in the composite material.
- the boron nitride fine particles are often apt to lie down laterally and the necessary sufficient thermal properties are not obtained anymore in the longitudinal direction.
- the boron nitride in order to be well fitted as a highly thermoconductive filler, the boron nitride must be configured into a spherical or aggregate shape thereby keeping the influence of directionality less.
- the boron nitride is generally obtained by reactions at high temperatures between a boron source (boric acid, borax, etc.) and a nitrogen source (urea, melamine, ammonia, etc.), and a “pineal” boron nitride obtained by the aggregation of scaly primary particles from boric acid and melamine has been proposed in the art (Patent Publication 1).
- the aggregate particle diameter of boron nitride prepared by this method is greater than 50 ⁇ m; in other words, it is difficult to prepare boron nitride fine particles of the submicron order—the object of the invention.
- Patent Publications 2, 3 and 4 there have been reports (Patent Publications 2, 3 and 4) about how to obtain boron nitride fine particles by a vapor-phase synthesis process.
- boron nitride fine particles obtained by these methods because of having low crystallinity, are found to be less than satisfactory in terms of boron nitride's characteristics: lubrication capability and high thermal conductivity.
- An object of the invention is to provide a submicron-order spherical boron nitride fine particle having a high sphericity.
- the present invention is embodied as follows.
- FIG. 1 is a schematic view of the apparatus of producing boron nitride fine particles under firing condition 1.
- FIG. 2 is a schematic view of the apparatus of producing boron nitride fine particles under firing condition 2.
- FIG. 3 is an electron micrograph taken of spherical boron nitride fine particles according to an example of the invention.
- FIG. 4 is an electron micrograph taken of spherical boron nitride fine particles according to a comparative example of the invention.
- a tubular furnace 3 is first used in an inert gas stream for a so-called gas phase reaction between a vaporized alkoxide borate and ammonia thereby continuously synthesizing a white powder (firing condition 1). Then, this white powder is fired in the tubular furnace 3 (resistance heating furnace) (firing condition 2). Finally, the fired product is charged in a boron nitride crucible that is then transferred to an induction heating furnace in which the fired product is further fired into a boron nitride fine particle (firing condition 3).
- firing conditions 1 and 2 there are three firing conditions used in the invention: in firing temperature ascending order, firing condition 1 of at least 750° C., firing condition 2 of 1,000 to 1,600° C., and firing condition 3 of 1,800 to 2,200° C.
- firing condition 1 and 2 the tubular furnace 3 may be used in the resistance heating mode
- firing condition 3 an electric furnace may be used as the tubular furnace 3 in the induction heating mode.
- firing conditions 1 and 2 there is no problem at all with the use of the induction heating mode of electric furnace under firing conditions 1 and 2.
- An apparatus used under firing condition 1 to prepare boron nitride fine particles comprises a tubular furnace 3 (resistance heating furnace), a reaction tube (quartz tube) 2 , an alkoxide borate feeder vessel 1 , an alkoxide borate inlet pipe 4 , an ammonia gas inlet pipe 5 , a sample recovery vessel 6 , etc.
- the spherical boron nitride fine particles of the invention are continuously synthesized by the so-called gas-phase reaction between a vaporized alkoxide borate and ammonia. This requires the use of an apparatus capable of continuous synthesis, and an apparatus using such a tubular furnace 3 as shown typically in FIG. 1 is preferably used under firing condition 1.
- tubular furnace 3 While there is no particular limitation on the tubular furnace 3 , it is preferable to use an easy-to-handle electric furnace.
- An electric furnace operates on the basic principle that a heating element or the like forming a furnace generates heat by the passage of electric current for heating of the interior of the furnace, and is specialized on the basis of heating modes and heating element materials.
- heating up to nearly 1,700° C. may be carried out in the resistance heating mode using a heating element, but for heating up to nearly 2,000° C. there is a coil induction heating mode in need.
- the heating element may be formed of a material such as silicon carbide or carbon.
- reaction tube 2 Although there is no particular limitation on the material of the reaction tube 2 used herein, it is preferable to make use of alumina or quartz having chemical stability and good heat resistance.
- FIG. 1 is a schematic view of firing condition 1 where a quartz tube is used as the reaction tube 2 and trimethyl borate is used as the alkoxide borate.
- the quartz tube 2 is placed in the resistance heating furnace 3 that is heated up to a given temperature. Then, trimethyl borate is placed in the feeder vessel 1 and introduced together with nitrogen into the quartz tube 2 by way of the inlet pipe 4 . In the meantime, ammonia is also introduced into the quartz tube 2 by way of the inlet pipe 5 . The introduced trimethyl borate and ammonia react with each other in the heated quartz tube 2 , yielding white powders (firing condition 1). Some white powders adhere to the interior of the quartz tube 2 , but the rest is all delivered to the recovery vessel 6 together with nitrogen and unreacted ammonia. The white powder product (product 7 ) is recovered in the recovery vessel 6 .
- the temperature of the tubular furnace 3 is preferably 750° C. or higher. At lower than 750° C., the resultant boron nitride fine particles often come to have an average particle diameter of greater than 1.0 ⁇ m.
- the reaction between trimethyl borate and ammonia gets done within 30 seconds. Exceeding 30 seconds may possibly cause the boron nitride fine particles to have an average particle diameter of greater than 1.0 ⁇ m.
- the alkoxide borate used herein includes trimethyl borate, triethyl borate and tri-isopropyl borate, among which the trimethyl borate is preferred because of its high reactivity with ammonia and its availableness.
- the trimethyl borate is available as reagents from many companies in general, and in the form of a reagent under the trade name of “TMB” from Tama Chemicals Corporate in particular.
- ammonia used herein, it is preferable to use a so-called impurity-free “high-purity” type.
- inert gas used herein, there is the mention of less chemical reactive gases, for instance, noble or rare gases such as helium, neon and argon, and nitrogen.
- the ammonia and alkoxide borate are fed at a molar ratio of 1 to 10.
- the ammonia/alkoxide borate molar ratio is less than 1, it is likely that the boron nitride fine particles may have a purity of lower than 98.0%, and as that molar ratio is greater than 10, it is likely that the boron nitride fine particles may have an average particle diameter of less than 0.01 ⁇ m.
- the apparatus used under firing condition 2 is built up of a resistance heating furnace 3 ′ and a reaction tube 2 ′ formed of alumina.
- the white powder product (product 7 ) synthesized under fining condition 1 is filled in the middle of the reaction tube that is then placed in the resistance heating furnace 3 ′. After that, nitrogen is introduced from an inlet pipe 4 ′ and ammonia is introduced from an inlet pipe 5 ′. After heated to a given temperature, the white powder product is fired for a given period of time. After the completion of firing, the resistance heating furnace 3 ′ is cooled down for recovery of the fired product.
- an induction heating furnace may be used instead.
- the temperature of the resistance heating furnace 3 is in the range of 1,000 to 1,600° C. Out of this range, the boron nitride fine particles are likely to have an orientation index of greater than 15.
- the reaction time under firing condition 2 is 1 hour or longer. In less than 1 hour, the boron nitride fine particles are likely to have an orientation index of greater than 15 and a scaly shape having a lower circularity.
- the atmosphere used under fining condition 2 is preferably ammonia gas or an ammonia gas/inert gas mixture.
- the boron nitride fine particles are likely to have an orientation index of greater than 15 or a purity of less than 98.0%, and to take a scaly shape having a lower average circularity.
- the fired product obtained under firing condition 2 is placed in a boron nitride crucible, and then further fired under firing condition 3 in an induction heating furnace at a given temperature, in which furnace a nitrogen atmosphere prevails.
- the firing temperature is as high as about 2,000° C.; so it is preferable to use the induction heating furnace as the firing furnace.
- the temperature under firing condition 3 is 1,800 to 2,200° C. At lower than 1,800° C., the boron nitride fine particles are likely to have a purity of lower than 98.0%, and at higher than 2,200° C., the boron nitride fine particles are likely to break down.
- the reaction time under fining condition 3 is 0.5 hour or longer. In less than 0.5 hour, the boron nitride fine particles are likely to have a purity of lower than 98.0%.
- the boron nitride fine particles of the invention have an average particle diameter of 0.05 to 1.0 ⁇ m. Out of this range, there is poor dispersability in resins, failing to obtain smooth surfaces, or upon dispersed in a resin, there are hard spots appearing in the resin, often making it impossible to keep the strength of the resin layer high.
- the orientation index of the boron nitride fine particles of the invention represented by a ratio (I 002 /I 100 ) between the diffraction line intensity I 002 of the (002) plane and the diffraction line intensity I 100 of the (100) plane as measured by powder X-ray diffractometry, should be 1 to 15 so as to obtain high thermal conductivity.
- the boron nitride fine particles of the invention should have a boron nitride purity of at least 98.0% so as to obtain high thermal conductivity.
- the boron nitride fine particles of the invention should have an average circularity of at least 0.80 so as to obtain high thermal conductivity.
- the quartz tube 2 was placed in the resistance heating furnace 3 that was then heated to a given temperature. Trimethyl borate was introduced from the feeder vessel 1 together with nitrogen into the quartz tube 2 by way of the inlet pipe 4 . In the meantime, ammonia was also introduced into the quartz tube 2 by way of the inlet pipe 5 . The introduced trimethyl borate and ammonia reacted with each other in the heated quartz tube 2 , yielding a white power product. The resultant white powder product was recovered in the recovery vessel 6 .
- the white powder product recovered under firing condition 1 was fired in the apparatus shown in FIG. 2 .
- the white powder product was filled up in the middle of the alumina tube 2 ′ that was then placed in the resistance heating furnace 3 ′, after which nitrogen and ammonia were admitted in from the inlet pipes 4 ′ and 5 ′, respectively. After heated up to the given temperatures indicated in Table 1, the white powder product was fired for a given time, after which the fired product was cooled down for recovery.
- the fired product obtained under firing condition 2 was placed in a boron nitride crucible, and further fired at a given temperature indicated in Table 1 in the induction heating furnace, in which a nitrogen atmosphere prevailed.
- the resultant boron nitride fine particles were measured in terms of average particle diameter (APD), orientation index (OI), boron nitride purity (BN) and average circularity (AC). The results are set out in Table 1.
- FIG. 3 An electron micrograph taken of an example of the invention is attached hereto as FIG. 3
- FIG. 4 An electron micrograph taken of a comparative example is attached hereto as FIG. 4 .
- Trimethyl Borate (C 3 H 9 BO 3 ): Reagent Trimethoxy Borane made by Wako Pure Chemical Industries, Ltd.
- the average particle diameter was measured using a laser diffraction/scattering particle size distribution analyzer made by Coulter and available under the trade name of LS-230.
- the orientation index I 002 /I 100 was figured out from the peak intensity ratio of X-ray diffraction of boron nitride.
- a particle image was taken using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and an image analyzer (for instance, trade name “MacView” available from Mountech Co., Ltd.) was then used to measure the projection area (S) and peripheral length (L) of the particle.
- SEM scanning electron microscope
- TEM transmission electron microscope
- MacView trade name “MacView” available from Mountech Co., Ltd.
Abstract
A method of producing a spherical boron nitride fine particle includes reacting ammonia with an alkoxide borate at an ammonia/alkoxide borate molar ratio of 1 to 10 in an inert gas stream at 750° C. or higher within 30 seconds, then applying heat treatment to a reaction product in an atmosphere of ammonia gas or a mixed gas of ammonia gas and an inert gas at 1,000 to 1,600° C. for at least 1 hour, and further firing the reaction product in an inert gas atmosphere at 1,800 to 2,200° C. for at least 0.5 hour.
Description
- This is a divisional application Ser. No. 15/117,853 filed Aug. 10, 2016, which is a National Phase of International Application No. PCT/JP2015/053489 filed Feb. 9, 2015, and claims priority from Japanese Patent Application No. 2014-024009 filed Feb. 12, 2014, the disclosure of which is hereby incorporated by reference herein in its entirety.
- The present invention relates to a spherical boron nitride fine particle well suited for use as a highly thermoconductive filler or the like, and a production method thereof.
- Hexagonal boron nitride (hereinafter called “boron nitride”), because of having lubrication capability, high thermal conductivity and insulation capability, is now widely used as releasing agents for solid lubricants, molten glasses and aluminum or the like as well as fillers for thermal radiation materials.
- To be compatible with higher performances of recent computers and electronic hardware in particular, measures against thermal radiation have increased in importance and attention has been directed to the high thermal conductivity of boron nitride.
- In recent years, it has been studied to add boron nitride to the resin layers of printed wiring boards and flexible copper-clad laminated sheets for the purpose of imparting high thermal conductivity and insulation to them.
- While generally available boron nitride has an average particle diameter of a few μm to 20 μm, some resin substrates for printed wiring boards and flexible copper-clad laminated sheets have a thickness of the order of several tens μm, and large average particle diameters of boron nitride result in poor dispersability in resins, failing to obtain smooth surfaces, or with that boron nitride dispersed, there are hard spots appearing, often making it impossible to keep the strength of the resin layer high. For these reasons, there is mounting demand for boron nitride fine particles of the submicron order (0.1 μm).
- To have high thermal conductivity, the boron nitride must be of high purity and high crystallinity, and the same goes for boron nitrite fine particles on the submicron order (0.1 μm).
- On the other hand, the boron nitride has a characteristic scaly shape, and its thermal properties are overwhelmingly better in the major or minor diameter direction than in the thickness or perpendicular direction. For this reason, the thermal properties of a composite material having boron nitride filled or packed in a resin such as silicone are considerably affected by the directionality of boron nitride fine particles in the composite material.
- For instance when the composite material is provided in a sheet form, however, the boron nitride fine particles are often apt to lie down laterally and the necessary sufficient thermal properties are not obtained anymore in the longitudinal direction.
- It follows that in order to be well fitted as a highly thermoconductive filler, the boron nitride must be configured into a spherical or aggregate shape thereby keeping the influence of directionality less.
- The boron nitride is generally obtained by reactions at high temperatures between a boron source (boric acid, borax, etc.) and a nitrogen source (urea, melamine, ammonia, etc.), and a “pineal” boron nitride obtained by the aggregation of scaly primary particles from boric acid and melamine has been proposed in the art (Patent Publication 1).
- However, the aggregate particle diameter of boron nitride prepared by this method is greater than 50 μm; in other words, it is difficult to prepare boron nitride fine particles of the submicron order—the object of the invention.
- On the other hand, there have been reports (
Patent Publications - However, boron nitride fine particles obtained by these methods, because of having low crystallinity, are found to be less than satisfactory in terms of boron nitride's characteristics: lubrication capability and high thermal conductivity.
-
- Patent Publication 1: JP(A) 09-202663
- Patent Publication 2: JP(A) 2000-327312
- Patent Publication 3: JP(A) 2004-182572
- Patent Publication 4: JP(A) 2010-180066
- An object of the invention is to provide a submicron-order spherical boron nitride fine particle having a high sphericity.
- To achieve the aforesaid object, the present invention is embodied as follows.
-
- (1) A spherical boron nitride fine particle, characterized by having an average particle diameter of 0.01 to 1.0 μm, an orientation index of 1 to 15, a boron nitride purity of 98.0% by mass or greater, and an average circularity of 0.80 or greater.
- (2) A method of producing a spherical boron nitride fine particle, characterized by reacting ammonia with an alkoxide borate at an ammonia/alkoxide borate molar ratio of 1 to 10 in an inert gas stream at 750° C. or higher within 30 seconds, then applying heat treatment to a reaction product in an atmosphere of ammonia gas or a mixed gas of ammonia gas and an inert gas at 1,000 to 1,600° C. for at least 1 hour, and further firing the reaction product in an inert gas atmosphere at 1,800 to 2,200° C. for at least 0.5 hour.
- According to the invention, it is possible to provide a submicron-order spherical boron nitride fine particle having a high sphericity.
-
FIG. 1 is a schematic view of the apparatus of producing boron nitride fine particles under firing condition 1. -
FIG. 2 is a schematic view of the apparatus of producing boron nitride fine particles underfiring condition 2. -
FIG. 3 is an electron micrograph taken of spherical boron nitride fine particles according to an example of the invention. -
FIG. 4 is an electron micrograph taken of spherical boron nitride fine particles according to a comparative example of the invention. - In the invention described here, a
tubular furnace 3 is first used in an inert gas stream for a so-called gas phase reaction between a vaporized alkoxide borate and ammonia thereby continuously synthesizing a white powder (firing condition 1). Then, this white powder is fired in the tubular furnace 3 (resistance heating furnace) (firing condition 2). Finally, the fired product is charged in a boron nitride crucible that is then transferred to an induction heating furnace in which the fired product is further fired into a boron nitride fine particle (firing condition 3). - It is here to be noted that unless otherwise specified, % is given on the mass basis.
- As described above, there are three firing conditions used in the invention: in firing temperature ascending order, firing condition 1 of at least 750° C.,
firing condition 2 of 1,000 to 1,600° C., andfiring condition 3 of 1,800 to 2,200° C. Underfiring conditions 1 and 2 thetubular furnace 3 may be used in the resistance heating mode, and underfiring condition 3 an electric furnace may be used as thetubular furnace 3 in the induction heating mode. Of course, there is no problem at all with the use of the induction heating mode of electric furnace underfiring conditions 1 and 2. - The invention will now be explained with reference to the accompanying drawings.
- An apparatus used under firing condition 1 to prepare boron nitride fine particles comprises a tubular furnace 3 (resistance heating furnace), a reaction tube (quartz tube) 2, an alkoxide borate feeder vessel 1, an alkoxide
borate inlet pipe 4, an ammoniagas inlet pipe 5, asample recovery vessel 6, etc. - The spherical boron nitride fine particles of the invention are continuously synthesized by the so-called gas-phase reaction between a vaporized alkoxide borate and ammonia. This requires the use of an apparatus capable of continuous synthesis, and an apparatus using such a
tubular furnace 3 as shown typically inFIG. 1 is preferably used under firing condition 1. - While there is no particular limitation on the
tubular furnace 3, it is preferable to use an easy-to-handle electric furnace. - An electric furnace operates on the basic principle that a heating element or the like forming a furnace generates heat by the passage of electric current for heating of the interior of the furnace, and is specialized on the basis of heating modes and heating element materials.
- Generally, heating up to nearly 1,700° C. may be carried out in the resistance heating mode using a heating element, but for heating up to nearly 2,000° C. there is a coil induction heating mode in need.
- By way of example but not by way of limitation, the heating element may be formed of a material such as silicon carbide or carbon.
- Although there is no particular limitation on the material of the
reaction tube 2 used herein, it is preferable to make use of alumina or quartz having chemical stability and good heat resistance. - Reference is now made to
FIG. 1 that is a schematic view of firing condition 1 where a quartz tube is used as thereaction tube 2 and trimethyl borate is used as the alkoxide borate. - The
quartz tube 2 is placed in theresistance heating furnace 3 that is heated up to a given temperature. Then, trimethyl borate is placed in the feeder vessel 1 and introduced together with nitrogen into thequartz tube 2 by way of theinlet pipe 4. In the meantime, ammonia is also introduced into thequartz tube 2 by way of theinlet pipe 5. The introduced trimethyl borate and ammonia react with each other in theheated quartz tube 2, yielding white powders (firing condition 1). Some white powders adhere to the interior of thequartz tube 2, but the rest is all delivered to therecovery vessel 6 together with nitrogen and unreacted ammonia. The white powder product (product 7) is recovered in therecovery vessel 6. - The temperature of the
tubular furnace 3 is preferably 750° C. or higher. At lower than 750° C., the resultant boron nitride fine particles often come to have an average particle diameter of greater than 1.0 μm. - The reaction between trimethyl borate and ammonia gets done within 30 seconds. Exceeding 30 seconds may possibly cause the boron nitride fine particles to have an average particle diameter of greater than 1.0 μm.
- The alkoxide borate used herein includes trimethyl borate, triethyl borate and tri-isopropyl borate, among which the trimethyl borate is preferred because of its high reactivity with ammonia and its availableness. The trimethyl borate is available as reagents from many companies in general, and in the form of a reagent under the trade name of “TMB” from Tama Chemicals Corporate in particular.
- While there is also no particular limitation on the ammonia used herein, it is preferable to use a so-called impurity-free “high-purity” type.
- While there is no particular limitation on the inert gas used herein, there is the mention of less chemical reactive gases, for instance, noble or rare gases such as helium, neon and argon, and nitrogen.
- The ammonia and alkoxide borate are fed at a molar ratio of 1 to 10. As the ammonia/alkoxide borate molar ratio is less than 1, it is likely that the boron nitride fine particles may have a purity of lower than 98.0%, and as that molar ratio is greater than 10, it is likely that the boron nitride fine particles may have an average particle diameter of less than 0.01 μm.
- The feeding of alkoxide borate and ammonia is put off, and the
tubular furnace 3 is powered off to recover the white powders synthesized under firing condition 1. Then, firing is carried out by the apparatus shown typically inFIG. 2 under firingcondition 2. - The apparatus used under firing
condition 2 is built up of aresistance heating furnace 3′ and areaction tube 2′ formed of alumina. The white powder product (product 7) synthesized under fining condition 1 is filled in the middle of the reaction tube that is then placed in theresistance heating furnace 3′. After that, nitrogen is introduced from aninlet pipe 4′ and ammonia is introduced from aninlet pipe 5′. After heated to a given temperature, the white powder product is fired for a given period of time. After the completion of firing, theresistance heating furnace 3′ is cooled down for recovery of the fired product. - Under firing
condition 2 an induction heating furnace may be used instead. - The temperature of the
resistance heating furnace 3 is in the range of 1,000 to 1,600° C. Out of this range, the boron nitride fine particles are likely to have an orientation index of greater than 15. - The reaction time under firing
condition 2 is 1 hour or longer. In less than 1 hour, the boron nitride fine particles are likely to have an orientation index of greater than 15 and a scaly shape having a lower circularity. - The atmosphere used under fining
condition 2 is preferably ammonia gas or an ammonia gas/inert gas mixture. In the absence of ammonia gas, the boron nitride fine particles are likely to have an orientation index of greater than 15 or a purity of less than 98.0%, and to take a scaly shape having a lower average circularity. - After the completion of the reaction under firing
condition 2, the electric furnace is powered off and the introduction of nitrogen or ammonia is put off, followed by cooling. - The fired product obtained under firing
condition 2 is placed in a boron nitride crucible, and then further fired under firingcondition 3 in an induction heating furnace at a given temperature, in which furnace a nitrogen atmosphere prevails. - It is here to be noted that the firing temperature is as high as about 2,000° C.; so it is preferable to use the induction heating furnace as the firing furnace.
- The temperature under firing
condition 3 is 1,800 to 2,200° C. At lower than 1,800° C., the boron nitride fine particles are likely to have a purity of lower than 98.0%, and at higher than 2,200° C., the boron nitride fine particles are likely to break down. - The reaction time under fining
condition 3 is 0.5 hour or longer. In less than 0.5 hour, the boron nitride fine particles are likely to have a purity of lower than 98.0%. - The boron nitride fine particles of the invention have an average particle diameter of 0.05 to 1.0 μm. Out of this range, there is poor dispersability in resins, failing to obtain smooth surfaces, or upon dispersed in a resin, there are hard spots appearing in the resin, often making it impossible to keep the strength of the resin layer high.
- The orientation index of the boron nitride fine particles of the invention, represented by a ratio (I002/I100) between the diffraction line intensity I002 of the (002) plane and the diffraction line intensity I100 of the (100) plane as measured by powder X-ray diffractometry, should be 1 to 15 so as to obtain high thermal conductivity.
- The boron nitride fine particles of the invention should have a boron nitride purity of at least 98.0% so as to obtain high thermal conductivity.
- The boron nitride fine particles of the invention should have an average circularity of at least 0.80 so as to obtain high thermal conductivity.
- The present invention will now be explained in further details with reference to experimental runs.
- The
quartz tube 2 was placed in theresistance heating furnace 3 that was then heated to a given temperature. Trimethyl borate was introduced from the feeder vessel 1 together with nitrogen into thequartz tube 2 by way of theinlet pipe 4. In the meantime, ammonia was also introduced into thequartz tube 2 by way of theinlet pipe 5. The introduced trimethyl borate and ammonia reacted with each other in theheated quartz tube 2, yielding a white power product. The resultant white powder product was recovered in therecovery vessel 6. - The white powder product recovered under firing condition 1 was fired in the apparatus shown in
FIG. 2 . - The white powder product was filled up in the middle of the
alumina tube 2′ that was then placed in theresistance heating furnace 3′, after which nitrogen and ammonia were admitted in from theinlet pipes 4′ and 5′, respectively. After heated up to the given temperatures indicated in Table 1, the white powder product was fired for a given time, after which the fired product was cooled down for recovery. - The fired product obtained under firing
condition 2 was placed in a boron nitride crucible, and further fired at a given temperature indicated in Table 1 in the induction heating furnace, in which a nitrogen atmosphere prevailed. The resultant boron nitride fine particles were measured in terms of average particle diameter (APD), orientation index (OI), boron nitride purity (BN) and average circularity (AC). The results are set out in Table 1. - It is to be noted that the temperature, time and firing atmosphere under firing
conditions - It is also to be noted that an electron micrograph taken of an example of the invention is attached hereto as
FIG. 3 , and an electron micrograph taken of a comparative example is attached hereto asFIG. 4 . - Trimethyl Borate (C3H9BO3): Reagent Trimethoxy Borane made by Wako Pure Chemical Industries, Ltd.
- Ammonia: Commercially available high-purity type
- The average particle diameter was measured using a laser diffraction/scattering particle size distribution analyzer made by Coulter and available under the trade name of LS-230.
- For the orientation index, an X-ray diffractometry apparatus (Geiger Flex 2013 Model) made by Rigaku Corporation was used in a range of 2θ=20°-25° to measure the intensity I002 of a diffraction line in the vicinity of 2θ=27-28° (the plane (002)) and the intensity I100 of a diffraction line in the vicinity of 2θ=41° (the plane (100)). The orientation index I002/I100 was figured out from the peak intensity ratio of X-ray diffraction of boron nitride.
- The boron nitride purity was measured by a method in which a sample was subjected to decomposition with an alkali sodium hydroxide, and ammonia was distilled out by a steam distillation process for collection in a boric acid solution. The resultant solution was titrated with a sulfuric acid normal solution to find the amount of nitrogen (N), after which the boron nitride purity (BN) was calculated from BN (%)=N(%)×1.772.
- For the average circularity, a particle image was taken using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and an image analyzer (for instance, trade name “MacView” available from Mountech Co., Ltd.) was then used to measure the projection area (S) and peripheral length (L) of the particle. The circularity was found by:
-
Circularity=4πS/L 2 - Arbitrarily selected one hundred particles were measured in terms of circularity, and the resultant average value was used as the average circularity for the sample.
-
TABLE 1 NH3/ Firing Firing Firing Run C3H9BO3 Cond. 1 Cond. 2 Cond. 3 No. (molar ratio) (° C.) (sec.) (° C.) (hr.) Gas (° C.) (hr.) 1-1 0.8 1,000 10 1,350 5 N2/NH3 2,000 4 1-2 1.2 1,000 10 1,350 5 N2/NH3 2,000 4 1-3 3.5 1,000 10 1,350 5 N2/NH3 2,000 4 1-4 9.7 1,000 10 1,350 5 N2/NH3 2,000 4 1-5 10.3 1,000 10 1,350 5 N2/NH3 2,000 4 1-6 3.5 720 10 1,350 5 N2/NH3 2,000 4 1-7 3.5 760 10 1,350 5 N2/NH3 2,000 4 1-8 3.5 1,300 10 1,350 5 N2/NH3 2,000 4 1-9 3.5 1,000 25 1,350 5 N2/NH3 2,000 4 1-10 3.5 1,000 40 1,350 5 N2/NH3 2,000 4 1-11 3.5 1,000 10 950 5 N2/NH3 2,000 4 1-12 3.5 1,000 10 1,020 5 N2/NH3 2,000 4 1-13 3.5 1,000 10 1,600 5 N2/NH3 2,000 4 1-14 3.5 1,000 10 1,630 5 N2/NH3 2,000 4 1-15 3.5 1,000 10 1,350 0.5 N2/NH3 2,000 4 1-16 3.5 1,000 10 1,350 1 NH3 2,000 4 1-17 3.5 1,000 10 1,350 5 N2 2,000 4 1-18 3.5 1,000 10 1,350 5 N2/NH3 2,000 4 1-19 3.5 1,000 10 1,350 5 N2/NH3 1,750 4 1-20 3.5 1,000 10 1,350 5 N2/NH3 1,800 4 1-21 3.5 1,000 10 1,350 5 N2/NH3 2,150 4 1-22 3.5 1,000 10 1,350 5 N2/NH3 2,230 4 1-23 3.5 1,000 10 1,350 5 N2/NH3 2,000 0.4 1-24 3.5 1,000 10 1,350 5 N2/NH3 2,000 0.8 Run No. APD (μm) OI BN (%) AC Remarks 1-1 0.20 5.6 97.8 0.90 Comparative 1-2 0.50 6.0 98.3 0.88 Inventive 1-3 0.20 6.0 99.0 0.90 Inventive 1-4 0.05 5.5 99.2 0.90 Inventive 1-5 0.008 4.0 99.2 0.90 Comparative 1-6 1.10 6.0 98.2 0.85 Comparative 1-7 0.50 6.0 98.7 0.87 Inventive 1-8 0.20 8.0 99.1 0.89 Inventive 1-9 0.70 7.0 99.0 0.85 Inventive 1-10 1.20 10.0 98.8 0.87 Comparative 1-11 0.90 18.0 98.3 0.80 Comparative 1-12 0.40 10.0 98.8 0.84 Inventive 1-13 0.30 13.0 99.2 0.82 Inventive 1-14 0.60 16.0 99.1 0.81 Comparative 1-15 1.00 25.0 98.7 * Comparative 1-16 0.20 7.0 98.6 0.85 Inventive 1-17 1.00 22.0 97.0 * Comparative 1-18 0.20 7.0 99.0 0.86 Inventive 1-19 0.20 8.0 97.8 0.88 Comparative 1-20 0.20 6.0 98.4 0.86 Inventive 1-21 0.70 11.0 99.4 0.83 Inventive 1-22 Particle Broken Down Comparative 1-23 0.70 4.5 97.7 0.91 Comparative 1-24 0.20 6.5 98.1 0.89 Inventive *Scaly shape -
- 1: Feeder vessel for the alkoxide borate
- 2: Reaction tube (quartz tube)
- 2′: Reaction tube (alumina tube)
- 3, 3′: Tubular furnace (resistance heating furnace)
- 4: Alkoxide borate inlet pipe
- 4′: Nitrogen inlet pile
- 5, 5′: Ammonia gas inlet pipe
- 6: Sample recovery vessel
- 7: Product
Claims (1)
1. A method of producing a spherical boron nitride fine particle, characterized by reacting ammonia with an alkoxide borate at an ammonia/alkoxide borate molar ratio of 1 to 10 in an inert gas stream at 750° C. or higher within 30 seconds, then applying heat treatment to a reaction product in an atmosphere of ammonia gas or a mixed gas of ammonia gas and an inert gas at 1,000 to 1,600° C. for at least 1 hour, and further firing the reaction product in an inert gas atmosphere at 1,800 to 2,200° C. for at least 0.5 hour.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US15/955,211 US20180230012A1 (en) | 2014-02-12 | 2018-04-17 | Method of producing spherical boron nitride fine particles |
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2014024009 | 2014-02-12 | ||
JP2014-024009 | 2014-02-12 | ||
PCT/JP2015/053489 WO2015122379A1 (en) | 2014-02-12 | 2015-02-09 | Spherical boron nitride particles and production method thereof |
US201615117853A | 2016-08-10 | 2016-08-10 | |
US15/955,211 US20180230012A1 (en) | 2014-02-12 | 2018-04-17 | Method of producing spherical boron nitride fine particles |
Related Parent Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2015/053489 Division WO2015122379A1 (en) | 2014-02-12 | 2015-02-09 | Spherical boron nitride particles and production method thereof |
US15/117,853 Division US10017386B2 (en) | 2014-02-12 | 2015-02-09 | Spherical boron nitride fine particles and production method thereof |
Publications (1)
Publication Number | Publication Date |
---|---|
US20180230012A1 true US20180230012A1 (en) | 2018-08-16 |
Family
ID=53800122
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US15/117,853 Active US10017386B2 (en) | 2014-02-12 | 2015-02-09 | Spherical boron nitride fine particles and production method thereof |
US15/955,211 Abandoned US20180230012A1 (en) | 2014-02-12 | 2018-04-17 | Method of producing spherical boron nitride fine particles |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US15/117,853 Active US10017386B2 (en) | 2014-02-12 | 2015-02-09 | Spherical boron nitride fine particles and production method thereof |
Country Status (7)
Country | Link |
---|---|
US (2) | US10017386B2 (en) |
EP (1) | EP3106430B1 (en) |
JP (1) | JP6467650B2 (en) |
KR (1) | KR102258544B1 (en) |
CN (1) | CN105980298B (en) |
TW (1) | TWI639553B (en) |
WO (1) | WO2015122379A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10752503B2 (en) | 2016-10-21 | 2020-08-25 | Denka Company Limited | Spherical boron nitride fine powder, method for manufacturing same and thermally conductive resin composition using same |
Families Citing this family (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2015193504A (en) * | 2014-03-31 | 2015-11-05 | ナガセケムテックス株式会社 | Boron nitride particle, resin composition and heat-conductive sheet |
KR102560615B1 (en) * | 2015-08-26 | 2023-07-27 | 덴카 주식회사 | Thermally conductive resin composition |
JP7005523B2 (en) * | 2016-05-27 | 2022-01-21 | サン-ゴバン セラミックス アンド プラスティクス,インコーポレイティド | Process for Producing Boron Nitride Aggregates |
EP3680300A4 (en) * | 2017-09-04 | 2021-06-09 | Toagosei Co., Ltd. | Composition for powder coating materials and coated article |
EP3696140B1 (en) * | 2017-10-13 | 2021-07-21 | Denka Company Limited | Boron nitride powder, method for producing same, and heat-dissipating member produced using same |
US20210163288A1 (en) | 2018-08-07 | 2021-06-03 | Denka Company Limited | Hexagonal boron nitride powder and method for producing hexagonal boron nitride powder |
CN112295535A (en) * | 2019-07-31 | 2021-02-02 | 东泰高科装备科技有限公司 | Boron nitride adsorbing material and synthesis method and synthesis device thereof |
CN114514195A (en) | 2019-10-23 | 2022-05-17 | 电化株式会社 | Boron nitride powder and method for producing same, boron carbonitride powder, composite material, and heat-dissipating member |
WO2021100617A1 (en) | 2019-11-19 | 2021-05-27 | デンカ株式会社 | Hexagonal boron nitride powder |
TW202124263A (en) * | 2019-11-21 | 2021-07-01 | 日商電化股份有限公司 | Boron nitride particles and resin composition |
WO2021111909A1 (en) * | 2019-12-06 | 2021-06-10 | デンカ株式会社 | Boron nitride particles and method for manufacturing same |
JPWO2021193028A1 (en) * | 2020-03-27 | 2021-09-30 | ||
TWI766320B (en) * | 2020-07-23 | 2022-06-01 | 南亞塑膠工業股份有限公司 | Prepreg and metallic clad laminate |
CN113753866B (en) * | 2021-08-03 | 2023-02-07 | 湖南大学 | Hexagonal boron nitride nanocrystal and solid phase preparation method thereof |
CN114132904B (en) * | 2021-12-06 | 2023-04-25 | 湖南大学 | Hexagonal boron nitride porous microsphere with high oil absorption and whitening effects for cosmetics |
WO2023162598A1 (en) * | 2022-02-22 | 2023-08-31 | デンカ株式会社 | Method for producing boron nitride powder, boron nitride powder, and resin sealing material |
Family Cites Families (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2883405B2 (en) * | 1990-06-04 | 1999-04-19 | 信越化学工業株式会社 | Crucible for pulling single crystal and method for producing the same |
JP3647079B2 (en) * | 1995-04-19 | 2005-05-11 | 電気化学工業株式会社 | Method for producing hexagonal boron nitride powder |
JP3461651B2 (en) * | 1996-01-24 | 2003-10-27 | 電気化学工業株式会社 | Hexagonal boron nitride powder and its use |
US6348179B1 (en) | 1999-05-19 | 2002-02-19 | University Of New Mexico | Spherical boron nitride process, system and product of manufacture |
CN1189249C (en) * | 2002-07-09 | 2005-02-16 | 中国科学院长春应用化学研究所 | Process for preparing nano cubic boron nitride |
JP3851951B2 (en) * | 2002-12-05 | 2006-11-29 | 独立行政法人物質・材料研究機構 | Method for producing submicron sized boron nitride spherical particles |
CN100402417C (en) * | 2005-12-01 | 2008-07-16 | 华中师范大学 | Hexagonal nanometer boron nitride microsphere and its synthesis process and application |
JP4817103B2 (en) * | 2007-04-25 | 2011-11-16 | 独立行政法人物質・材料研究機構 | Method for producing boron nitride nanotubes |
JP5105372B2 (en) * | 2009-02-03 | 2012-12-26 | 独立行政法人物質・材料研究機構 | Boron nitride spherical nanoparticles and production method thereof |
CN102482087A (en) * | 2009-08-20 | 2012-05-30 | 株式会社钟化 | Process for production of spheroidized boron nitride |
CN102574684B (en) * | 2009-10-09 | 2015-04-29 | 水岛合金铁株式会社 | Hexagonal boron nitride powder and method for producing same |
CN105947997B (en) | 2011-11-29 | 2018-12-21 | 三菱化学株式会社 | Boron nitride aggregated particle, the composition containing the particle and the three dimensional integrated circuits with the layer comprising the composition |
-
2015
- 2015-02-09 CN CN201580008547.9A patent/CN105980298B/en active Active
- 2015-02-09 US US15/117,853 patent/US10017386B2/en active Active
- 2015-02-09 JP JP2015562810A patent/JP6467650B2/en active Active
- 2015-02-09 KR KR1020167021931A patent/KR102258544B1/en active IP Right Grant
- 2015-02-09 EP EP15749281.0A patent/EP3106430B1/en active Active
- 2015-02-09 WO PCT/JP2015/053489 patent/WO2015122379A1/en active Application Filing
- 2015-02-11 TW TW104104538A patent/TWI639553B/en active
-
2018
- 2018-04-17 US US15/955,211 patent/US20180230012A1/en not_active Abandoned
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10752503B2 (en) | 2016-10-21 | 2020-08-25 | Denka Company Limited | Spherical boron nitride fine powder, method for manufacturing same and thermally conductive resin composition using same |
Also Published As
Publication number | Publication date |
---|---|
KR102258544B1 (en) | 2021-05-28 |
US20160368769A1 (en) | 2016-12-22 |
EP3106430A4 (en) | 2017-11-08 |
JP6467650B2 (en) | 2019-02-13 |
EP3106430B1 (en) | 2018-07-18 |
WO2015122379A1 (en) | 2015-08-20 |
JPWO2015122379A1 (en) | 2017-03-30 |
EP3106430A1 (en) | 2016-12-21 |
CN105980298B (en) | 2018-12-18 |
KR20160122725A (en) | 2016-10-24 |
TW201536671A (en) | 2015-10-01 |
CN105980298A (en) | 2016-09-28 |
US10017386B2 (en) | 2018-07-10 |
TWI639553B (en) | 2018-11-01 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US20180230012A1 (en) | Method of producing spherical boron nitride fine particles | |
US10017387B2 (en) | Boron nitride fine particles and production method thereof | |
JP6698953B2 (en) | Boron nitride powder, method for producing the same, and heat dissipation member using the same | |
JP5105372B2 (en) | Boron nitride spherical nanoparticles and production method thereof | |
JP2007308360A (en) | Hexagonal boron nitride powder | |
CN102515233A (en) | Method and product for preparing aluminum oxide with hot plasma | |
WO2020032060A1 (en) | Hexagonal boron nitride powder and method for producing hexagonal boron nitride powder | |
Jiang et al. | Study on the synthesis of β-SiC nanoparticles from diamond-wire silicon cutting waste | |
Liu et al. | Synthesis of β-SiC nanowires via a facile CVD method and their photoluminescence properties | |
Kipcak et al. | The synthesis and physical properties of magnesium borate mineral of admontite synthesized from sodium borates | |
Kumari et al. | Effect of surfactants on the structure and morphology of magnesium borate hydroxide nanowhiskers synthesized by hydrothermal route | |
JP2016175830A (en) | Apparatus and method for producing aluminum nitride powder and aluminum nitride powder produced by the method | |
JPH10203807A (en) | Boron nitride powder of turbostratic structure and its production | |
US20120070357A1 (en) | Method for the preparation of boron nitride powder | |
JP3896452B2 (en) | Method for producing silicon magnesium nitride powder and product thereof | |
Aleksandrov et al. | Plasma Chemical Production Technology of AlN as High Thermal Conductivity Material | |
Yang et al. | Synthesis of h-AlN Nanowires via Carbothermal Reduction and Nitridation Method Using Acetylene Black | |
WO2021193764A1 (en) | Boron nitride particle and resin composition and container comprising same | |
Wu et al. | Effect of ammonium chloride on the morphology of hexagonal boron nitride prepared by magnesium thermal reduction | |
JP2015051903A (en) | METHOD OF PRODUCING AMORPHOUS Li3 BO3 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: FINAL REJECTION MAILED |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |