Provided is a boron nitride agglomerate. The boron nitride agglomerate is of a multi-stage structure formed by arranging flaky hexagonal boron nitride primary particles in three-dimensional directions through adhesion of an inorganic binder. Further provided is a method for preparing the boron nitride agglomerate. The method comprises: mixing flaky hexagonal boron nitride primary particles with an inorganic binder, and controlling the mass of the inorganic binder to account for 0.02-20% of the mass of the flaky hexagonal boron nitride primary particles, so as to obtain the boron nitride agglomerate. The boron nitride agglomerate provided can be added to thermosetting resin compositions, and resin sheets, resin composite metal foil, prepregs, laminates, metal foil-covered laminates, and printed wiring boards prepared using the same have higher boron nitride addition, high thermal conductivity, and high peel strength.

A cubic boron nitride sintered material includes: more than or equal to 85 volume % and less than 100 volume % of cubic boron nitride grains; and a remainder of a binder, wherein the binder includes WC, Co and an Al compound, and when a TEM-EDX is used to analyze an interface region including an interface at which the cubic boron nitride grains are adjacent to each other, oxygen exists on a whole or part of the interface, and a width D of a region in which the oxygen exists is more than or equal to 0.1 nm and less than or equal to 10 nm.

Disclosed is a hexagonal boron nitride powder having excellent glitter property. A hexagonal boron nitride powder includes hexagonal boron nitride particles, in which among the hexagonal boron nitride particles, a number ratio of particles having a bent structure at an angle of 110° to 160° with respect to (0,0,1) crystal plane of the primary particles is 30% or more.

Provided is a composite material that has improved dispersibility of an exfoliated layered substance in a resin or the like and can thus significantly improve the properties, such as impact resistance, of a synthetic resin. A composite material in which the surface of an exfoliated layered substance is coated with a compound having a reactive group, wherein the compound having a reactive group is a compound having at least one reactive group selected from the group consisting of an epoxy group, an oxetanyl group, an isocyanate group, an acrylic group, a methacrylic group, a vinyl ether group, a vinyl ester group, and a hydrolyzable silyl group, and the compound having a reactive group is contained in an amount of 0.1 to 100 parts by mass, with respect to 100 parts by mass of the exfoliated layered substance.

A polycrystalline cubic boron nitride comprising 96% by volume or more of cubic boron nitride, wherein the cubic boron nitride has a dislocation density of more than 8×10.sup.15/m.sup.2, the polycrystalline cubic boron nitride comprises a plurality of crystal grains, and the plurality of crystal grains have a median diameter d50 of an equivalent circle diameter of less than 100 nm.

A polycrystalline cubic boron nitride comprising 98.5% by volume or more of cubic boron nitride, wherein the cubic boron nitride has a dislocation density of more than 8×10.sup.15/m.sup.2, the polycrystalline cubic boron nitride comprises a plurality of crystal grains, and the plurality of crystal grains have a median diameter d50 of an equivalent circle diameter of 0.1 μm or more and 0.5 μm or less.

A hexagonal BN powder including aggregates of primary particles of hexagonal BN containing boron and oxygen as impurity elements at a content of 1.00 to 30.00% and 0 to 1.00% by mass, respectively, which has a peak A in a predetermined particle diameter range and a 50% volume cumulative particle diameter D.sub.50 (d1) of 30.0 to 200.0 μl in a particle size distribution curve, and in which a ratio of a height (a1) of the peak A before treatment to a height (a2) of the peak A after treatment is 0.80 to 1.00 and a ratio of D.sub.50 (d1) before treatment to D.sub.50 (d2) after treatment is 0.80 to 1.00 when the hexagonal BN powder is ultrasonically treated under a predetermined condition for 1 minute. Also disclosed is a method for producing the hexagonal BN powder, a composition and a heat dissipation material.

The present invention provides a method of producing a boron nitride containing fluid comprising the steps of: providing boron nitride; oxidising the boron nitride to functionalise the surface of the boron nitride; and dispersing the oxidised boron nitride in a base fluid to produce the boron nitride containing fluid. Associated boron nitride containing fluids and its use are also disclosed.

Provided is an exfoliated layered substance that has favorable dispersibility when added to a resin or the like and has an effect of significantly improving the properties of the resin or the like. There is provided a composite material in which the surface of an exfoliated layered substance is coated with a coating substance, wherein the coating substance is at least one substance selected from the group consisting of an antioxidant, a UV absorber, a hindered amine light stabilizer, a flame retardant, a plasticizer, a lubricant, a surfactant, a polyoxypropylene compound, a radically polymerized polymer having a hydrophilic unit and a hydrophobic unit, a process oil, and a quaternary ammonium salt compound, and the coating substance is contained in an amount of 0.1 to 100 parts by mass, with respect to 100 parts by mass of the exfoliated layered substance.

The polycrystalline cubic boron nitride contains a cubic boron nitride at a content greater than or equal to 98.5% by volume, and has an area rate S1 of crystal grains, the crystal grains having an equivalent circle diameter greater than or equal to 1 μm, less than or equal to 20 area % at a cross section of the polycrystalline cubic boron nitride as observed with a scanning electron microscope at a magnification of 10,000.