A hexagonal boron nitride powder whose maximum absorption peak within the range of 3,100 to 3,800 cm.sup.1 of the diffuse reflectance fourier transform infrared spectrum is existent at 3,530 to 3,590 cm.sup.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.

A hexagonal boron nitride powder having an average longer diameter (L) of primary particles in the hexagonal boron nitride powder of 10 ?m or less, an average thickness (D) of the primary particles in the hexagonal boron nitride powder of 0.20 ?m or more, a ratio of the average longer diameter (L) to the average thickness (D), [L/D], of 3.0 or more and 5.0 or less, and a content of primary particles having a ratio of a longer diameter (l) to a thickness (d), [l/d], of 3.0 or more and 5.0 or less of 25% or more. Also disclosed is a method for producing the hexagonal boron nitride powder, and a resin composition and a resin sheet each containing the hexagonal boron nitride powder.

A hexagonal boron nitride (hBN) powder containing an aggregate of primary particles of hBN, in which the powder has a primary particle size of less than 10 m, a ratio of an average longer diameter (L.sub.1) to an average thickness (d.sub.1) of the primary particles, [L.sub.1/d.sub.1], of 5.0 or more and 20 or less, and a BET specific surface area of less than 10 m.sup.2/g, and the powder has one maximum peak in a range of a particle size of 45 m or more and 150 m or less in a particle size distribution curve of a hexagonal boron nitride powder classified to have a particle size of 45 m or more and 106 m or less, and has a decrease rate of the maximum peak of 10% or more and less than 40% when a dispersion liquid obtained by dispersing the hexagonal boron nitride powder in water is subjected to an ultrasonic treatment for 1 minute, the peak decrease rate being calculated by expression (1), a method for producing the hBN powder, and a resin composition and a resin sheet each containing the hBN powder.

In various embodiments set forth herein, methods of making boron nitride ceramic powder are provided.

To provide a boron nitride powder having excellent heat conductivity and high particle strength. Provided is a boron nitride powder which comprises bulky boron nitride formed such that scaly primary particles of hexagonal boron nitride are aggregated to form bulky particles, and which has the following characteristics (A) to (C): (A) a particle strength of the bulky particles at a cumulative breakdown rate of 63.2% is 5.0 MPa or more; (B) an average particle size of the boron nitride powder is 2 m or more and 20 m or less; and (C) an orientation index of the boron nitride powder as determined from X-ray diffraction is 20 or less.

This disclosure provides methods and materials related to boron nitride aerogels. For example, one aspect relates to a method for making an aerogel comprising boron nitride, comprising: (a) providing boron oxide and an aerogel comprising carbon; (b) heating the boron oxide to melt the boron oxide and heating the aerogel; (c) mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide; and (d) converting at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride. Another aspect relates to a method for making an aerogel comprising boron nitride, comprising heating boron oxide and an aerogel comprising carbon under flow of a nitrogen-containing gas, wherein boron oxide vapor and the nitrogen-containing gas convert at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride.

This disclosure provides methods and materials related to boron nitride aerogels. For example, one aspect relates to a method for making an aerogel comprising boron nitride, comprising: (a) providing boron oxide and an aerogel comprising carbon; (b) heating the boron oxide to melt the boron oxide and heating the aerogel; (c) mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide; and (d) converting at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride. Another aspect relates to a method for making an aerogel comprising boron nitride, comprising heating boron oxide and an aerogel comprising carbon under flow of a nitrogen-containing gas, wherein boron oxide vapor and the nitrogen-containing gas convert at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride.

There is provided a hexagonal boron nitride powder, having: a particle diameter D95 of 70 m or less; a dynamic friction coefficient (MIU) of 0.50 or less; and a deviation of the dynamic friction coefficient (MMD) of 0.005 or less in a volume-based cumulative particle diameter distribution (a) as measured by a laser diffraction scattering method for the powder untreated with ultrasonic, the D95 being a 95% cumulative value in the volume-based cumulative particle diameter distribution (a) in a particle size distribution curve; and an average particle diameter (D50) of 3 to 15 m; a (D90-D10)/D50 of 1.30 or less; and a content of coarse particles of 2.0 volume % or less, the coarse particles being more than three times as large as the D50, in a volume-based cumulative particle diameter distribution (b) as measured by a laser diffraction scattering method for the powder treated with ultrasonic, the D10, the D50, and the D90 being a 10% cumulative value, a 50% cumulative value, and a 90% cumulative value, respectively, in the volume-based cumulative particle diameter distribution (b) in a particle size distribution curve.

This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

A boron nitride powder that includes agglomerated particles formed by agglomeration of primary particles of boron nitride, where a graphitization index is 2.0 or less, a boron oxide content is 0.1% by mass or less, and a boron oxide content after a heat cycle test is 0.2% by mass or less.