Abstract: A boron nitride powder including flat-shaped primary particles of BN and an aggregate of the primary particles has a water permeation speed less than 1 mm2/s and oil absorption of 100 ml/100 g to 500 ml/100 g, which is a cosmetic boron nitride powder excellent in water repellency and oil absorbency. The use of such a boron nitride powder provides a cosmetic significantly improved not only in gloss finish and transparency (bare skin feeling) but also in sustainability.

Abstract: A boron nitride powder including flat-shaped primary particles of BN and an aggregate of the primary particles has a water permeation speed not less than 1 mm2/s and oil absorption of 100 ml/100 g to 500 ml/100 g, which is a cosmetic boron nitride powder with high hydrophilicity and high oil absorbency. The use of such a boron nitride powder provides a cosmetic that is significantly improved not only in gloss finish and transparency (bare skin feeling) but also in sustainability.

Abstract: Sintered spherical BN particles having secondary particles formed of aggregated primary BN particles, in which the number ratio of particles, each having a recess on its surface is 50% or more in the sintered spherical BN particles, and each of the sintered spherical BN particles has a compressive strength of 0.1 MPa to 100 MPa. The sintered spherical BN particles are not only excellent in heat dissipation properties and adhesiveness, but also have high compressive strength, and therefore, show a small variation in heat dissipation properties and is free from conduction failure, which would otherwise be caused by exfoliation of the copper foil, when used as a filling material for a polymer composite material.

Abstract: A boron nitride powder including flat-shaped primary particles of BN and an aggregate of the primary particles has a water permeation speed less than 1 mm2/s and oil absorption of 100 ml/100 g to 500 ml/100 g, which is a cosmetic boron nitride powder excellent in water repellency and oil absorbency. The use of such a boron nitride powder provides a cosmetic significantly improved not only in gloss finish and transparency (bare skin feeling) but also in sustainability.

Abstract: A boron nitride powder including flat-shaped primary particles of BN and an aggregate of the primary particles has a water permeation speed not less than 1 mm2/s and oil absorption of 100 ml/100 g to 500 ml/100 g, which is a cosmetic boron nitride powder with high hydrophilicity and high oil absorbency. The use of such a boron nitride powder provides a cosmetic that is significantly improved not only in gloss finish and transparency (bare skin feeling) but also in sustainability.

Abstract: Sintered spherical BN particles having secondary particles formed of aggregated primary BN particles, in which the number ratio of particles, each having a recess on its surface is 50% or more in the sintered spherical BN particles, and each of the sintered spherical BN particles has a compressive strength of 0.1 MPa to 100 MPa. The sintered spherical BN particles are not only excellent in heat dissipation properties and adhesiveness, but also have high compressive strength, and therefore, show a small variation in heat dissipation properties and is free from conduction failure, which would otherwise be caused by exfoliation of the copper foil, when used as a filling material for a polymer composite material.

Abstract: A hexagonal boron nitride (h-BN) powder is disclosed in which primary particles of the powder exhibit a ratio (D/d) of long diameter (D) to thickness (d) in a range of 5 to 10. Agglomerated particle bodies made of the primary particles have an average particle diameter (D50) in a range of 2 ?m to 200 ?m, inclusive, and the powder has a bulk density in a range of 0.5 g/cm3 to 1.0 g/cm3. In an exemplary method for producing the h-BN, boron carbide is nitridizated in a nitrogen partial pressure of at least 5 kPa at 1800° C. to 2200° C., inclusive. B2O3 (or precursor thereof) is added to the nitridization product to produce a mixture. The mixture is decarbonized in a non-oxidizing atmosphere at a 1500° C. to 2200° C., inclusive. The decarbonization product is pulverized and subject to particle-size classification, yielding H-BN powder. The method includes a depressurizing step, performed at 100 kPa or less either during nitridization or after decarbonization.

Abstract: A hexagonal boron nitride (h-BN) powder is disclosed in which primary particles of the powder exhibit a ratio (D/d) of long diameter (D) to thickness (d) in a range of 5 to 10. Agglomerated particle bodies made of the primary particles have an average particle diameter (D50) in a range of 2 ?m to 200 ?m, inclusive, and the powder has a bulk density in a range of 0.5 g/cm3 to 1.0 g/cm3. In an exemplary method for producing the h-BN, boron carbide is nitridizated in a nitrogen partial pressure of at least 5 kPa at 1800° C. to 2200° C., inclusive. B2O3 (or precursor thereof) is added to the nitridization product to produce a mixture. The mixture is decarbonized in a non-oxidizing atmosphere at a 1500° C. to 2200° C., inclusive. The decarbonization product is pulverized and subject to particle-size classification, yielding H-BN powder. The method includes a depressurizing step, performed at 100 kPa or less either during nitridization or after decarbonization.

Abstract: A hexagonally crystalline boron nitride containing water-soluble boron containing impurity in such a magnitude that amount of boron to be contained in an extract after boiling at 100.degree. C. of pure water is less than or equal to 100 .mu.g/g-BN. In order to purify the boron nitride, a purification process is carried out according to the steps of preparing fine particles of boron nitride powder; dispersing the boron nitride powder in a disperser and stirred for a given period of time for removing water-soluble boron containing impurity; and drying the boron nitride in an atmosphere, in which vapor pressure is maintained lower than or equal to 10 mmHG and/or the process temperature is maintained lower than or equal to 100.degree. C.

Abstract: A hexagonally crystalline boron nitride containing water-soluble boron containing impurities in such a magnitude that the amount of boron contained in an extract after boiling at 100.degree. C. in pure water is less than or equal to 100 .mu.g per gram of boron nitride. In order to purify the boron nitride, a purification process is carried out according to the steps of preparing fine particles of boron nitride powder; dispersing the boron nitride powder in a dispersion medium and stirred for a given period of time for removing water-soluble boron containing impurities; and drying the boron nitride in atmosphere, in which the vapor pressure is maintained lower than or equal to 10 mmHG and/or the process temperature is maintained lower than or equal to 100.degree. C.

Abstract: The powder of hexagonal boron nitride is prepared by heat-treating a powdery mixture composed of an oxygen-containing boron compound, e.g. boric acid, and a nitrogen compound, e.g. dicyandiamide and melamine, with admixture of minor amounts of a carbonaceous powder, e.g. carbon black, and/or borax. Further, an alkaline earth metal compound such as calcium carbonate is added either to the powdery mixture of the starting materials before the heat treatment or to the powder after the heat treatment. The h-BN powder has excellent sinterability so that sintered bodies of boron nitride having a high density and high bending strength can readily be prepared by use of a hot press.