Abstract: Provided are a boron nitride powder having a relatively small particle size, in which an amount of metal impurities present on a surface of the boron nitride powder is significantly reduced, and extremely high purity is achieved, and a method for producing the boron nitride powder. A hexagonal boron nitride powder has an average particle size (D50) of 2.0 to 6.0 ?m and a specific surface area measured by a BET method of 4 to 12 m2/g, in which a concentration of a calcium element is 1 ppm or less, a concentration of a silicon element is 5 ppm or less, a concentration of a sodium element is 5 ppm or less, and a concentration of an iron element is 1 ppm or less on a surface of hexagonal boron nitride particles constituting the powder, the hexagonal boron nitride powder preferably has an average aspect ratio (major axis/thickness) of 1 to 7, and is useful as a filler for resin.

Abstract: Provided is a method for producing, with a small amount of lithium, a hexagonal boron nitride powder containing thick hexagonal boron nitride particles. A method for producing a hexagonal boron nitride powder, including the steps of: preparing a mixed powder which contains an organic compound containing nitrogen atoms, a boron source which contains boron atoms whose molar ratio with respect to the nitrogen atoms is adjusted to be 0.26 or more and 0.67 or less, and an alkali metal in which lithium atoms are adjusted to be in a range of 30 mol % or more and less than 100 mol %, the alkali metal being present such that a molar ratio of the boron atoms with respect to alkali metal atoms contained in the alkali metal is 0.75 or more and 3.35 or less; and heating the mixed powder at a maximum temperature of 1200° C. or higher and 1500° C. or lower.

Abstract: The present invention provides a hexagonal boron nitride powder that has a highly reduced content of magnetic foreign bodies and is excellent in electrical insulation, and a production method capable of producing the hexagonal boron nitride powder at low cost. The hexagonal boron nitride powder includes single particles and/or aggregated particles of hexagonal boron nitride and has a total content of Co, Cr, Cu, Fe, Mg, Mn, Ni, Ti, Zn, and Al of not more than 20 ppm. The method for producing the hexagonal boron nitride powder with a reduced content of magnetic foreign bodies includes a plurality of specific steps.

Abstract: Provided is a production method which makes it possible to improve a filling property, with respect to a resin, of a hexagonal boron nitride powder which contains hexagonal boron nitride particles each having a low aspect ratio, while maintaining low thermal conduction anisotropy of the hexagonal boron nitride powder. A method of producing a hexagonal boron nitride powder includes disintegrating, by a means which substantially does not involve pulverization of primary particles, a hexagonal boron nitride raw material powder which contains (i) hexagonal boron nitride particles each having an aspect ratio of 1.5 to 5.0 and (ii) an aggregate that contains hexagonal boron nitride particles each having an aspect ratio of more than 5.0.

Abstract: To provide a hexagonal boron nitride powder which contains agglomerates, has a maximum torque calculated by measuring in accordance with JIS-K-6217-4 of 0.20 to 0.50 Nm, a DBP absorption rate of 50 to 100 ml/100 g, a tap bulk density of 0.66 to 0.95 g/cm3 and reduced anisotropy of heat conduction and can provide high heat conductivity and dielectric strength to a resin composition produced by filling a resin therewith and a process for producing the powder by carrying out a reduction nitriding reaction using boron carbide.

Abstract: It is an object to achieve a resin sheet having high thermal conductance and high dielectric strength. Hexagonal boron nitride powder in accordance with an aspect of the present invention includes hexagonal boron nitride agglomerate particles each including agglomerated hexagonal boron nitride primary particles, and has a specific surface area of not less than 0.5 m2/g and not more than 5.0 m2/g. The hexagonal boron nitride primary particles each have a long diameter of not less than 0.6 ?m and not more than 4.0 ?m and an aspect ratio of not less than 1.5 and not more than 5.0.

Abstract: A hexagonal boron nitride powder whose maximum absorption peak within the range of 3,100 to 3,800 cm?1 of the diffuse reflectance fourier transform infrared spectrum is existent at 3,530 to 3,590 cm?1 and which is able to provide high heat conductivity, dielectric strength and copper foil peel strength to a resin composition obtained by filling the powder into a resin, and a process for producing the above boron nitride powder by mixing together an oxygen-containing boron compound, a carbon source having a sulfur concentration of 1,000 to 10,000 ppm and an oxygen-containing calcium compound in a specific ratio and reduction nitriding the mixture.

Abstract: To provide a hexagonal boron nitride powder which contains agglomerates, has a maximum torque calculated by measuring in accordance with JIS-K-6217-4 of 0.20 to 0.50 Nm, a DBP absorption rate of 50 to 100 ml/100 g, a tap bulk density of 0.66 to 0.95 g/cm3 and reduced anisotropy of heat conduction and can provide high heat conductivity and dielectric strength to a resin composition produced by filling a resin therewith and a process for producing the powder by carrying out a reduction nitriding reaction using boron carbide.

Abstract: A hexagonal boron nitride powder whose maximum absorption peak within the range of 3,100 to 3,800 cm?1 of the diffuse reflectance fourier transform infrared spectrum is existent at 3,530 to 3,590 cm?1 and which is able to provide high heat conductivity, dielectric strength and copper foil peel strength to a resin composition obtained by filling the powder into a resin, and a process for producing the above boron nitride powder by mixing together an oxygen-containing boron compound, a carbon source having a sulfur concentration of 1,000 to 10,000 ppm and an oxygen-containing calcium compound in a specific ratio and reduction nitriding the mixture.