A composition (or an aggregate) comprising a h-BN/BNNT structure that comprises a boron nitride nanotube structure and at least a first hexagonal boron nitride structure. Also, a composition comprising at least a first epitaxial h-BN/BNNT structure and at least one metal adhered to the first epitaxial h-BN/BNNT structure. Also, a composition (or an aggregate) that comprises independent boron nitride nanotubes, in which a total mass percentage of independent hexagonal boron nitride and residual boron in the composition is not more than 35%. Also, a material comprising at least a first hexagonal boron nitride structure and at least a first boron nitride nanotube structure, wherein atoms in the first hexagonal boron nitride structure are epitaxially aligned with atoms in the first boron nitride nanotube structure that are closest to the first hexagonal boron nitride structure.

A microstructure comprises a plurality of interconnected units wherein the units are formed of hexagonal boron nitride (h-BN) tubes. The graphene tubes may be formed by photo-initiating the polymerization of a monomer in a pattern of interconnected units to form a polymer microlattice, removing unpolymerized monomer, coating the polymer microlattice with a metal, removing the polymer microlattice to leave a metal microlattice, depositing an h-BN precursor on the metal microlattice, converting the h-BN precursor to h-BN, and removing the metal microlattice.

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/cm.sup.3 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.

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/cm.sup.3 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.

Provided is an insulating sheet capable of effectively enhancing thermal conduction and adhesiveness and effectively suppressing variation in the adhesiveness. The insulating sheet according to the present invention contains a thermosetting component and boron nitride, the insulating sheet has a first surface on one side in a thickness direction and a second surface on the other side in the thickness direction, and a first average aspect ratio of the boron nitride in a region having a thickness of 10% of a thickness of the sheet, from the first surface toward the second surface is smaller than a second average aspect ratio of the boron nitride in a region having a thickness of 90% of a thickness of the sheet, from the second surface toward the first surface.

Provided is an insulating sheet capable of effectively enhancing thermal conduction and adhesiveness and effectively suppressing variation in the adhesiveness. The insulating sheet according to the present invention contains a thermosetting component and boron nitride, the insulating sheet has a first surface on one side in a thickness direction and a second surface on the other side in the thickness direction, and a first average aspect ratio of the boron nitride in a region having a thickness of 10% of a thickness of the sheet, from the first surface toward the second surface is smaller than a second average aspect ratio of the boron nitride in a region having a thickness of 90% of a thickness of the sheet, from the second surface toward the first surface.

Provided is an insulating sheet capable of effectively enhancing thermal conduction and adhesiveness and effectively suppressing generation of voids. The insulating sheet according to the present invention contains a thermosetting component and boron nitride, the insulating sheet has a first surface on one side in a thickness direction and a second surface on the other side in the thickness direction, and a first average major diameter of the boron nitride in a region having a thickness of 10% of a thickness of the sheet, from the first surface toward the second surface is smaller than a second average major diameter of the boron nitride in a region having a thickness of 90% of a thickness of the sheet, from the second surface toward the first surface.

Thermal interface materials may be enhanced through the dispersion of refined boron nitride nanotubes (BNNTs) into a polymer matrix material and one or more microfillers. A refined BNNT material may be formed by reducing free boron particle content from an as-synthesized BNNT material, and in some embodiments reducing h-BN content. Reducing these species improves the thermal conductivity of the BNNTs. Refined BNNTs may be deagglomerated to reduce the size and mass of BNNTs in agglomerations when the deagglomerated BNNT material is dispersed into a target polymer matrix material. The deagglomerated BNNT material may be lyophilized prior to dispersion in the matrix material, to retain the deagglomeration benefit following return to solid state. The surface of the deagglomerated BNNT material may be modified, with one or more functional groups that improve dispersibility and heat transfer in the target polymer matrix material.

Thermal interface materials may be enhanced through the dispersion of refined boron nitride nanotubes (BNNTs) into a polymer matrix material and one or more microfillers. A refined BNNT material may be formed by reducing free boron particle content from an as-synthesized BNNT material, and in some embodiments reducing h-BN content. Reducing these species improves the thermal conductivity of the BNNTs. Refined BNNTs may be deagglomerated to reduce the size and mass of BNNTs in agglomerations when the deagglomerated BNNT material is dispersed into a target polymer matrix material. The deagglomerated BNNT material may be lyophilized prior to dispersion in the matrix material, to retain the deagglomeration benefit following return to solid state. The surface of the deagglomerated BNNT material may be modified, with one or more functional groups that improve dispersibility and heat transfer in the target polymer matrix material.

The present disclosure relates to an apparatus and a method for purifying BNNT and purified BNNT, more specifically to an apparatus and a method for purifying BNNT, which allow separation of pure BNNT from synthesized BNNT wherein various impurities are included with high purification efficiency and separation of BNNT based on length, and purified BNNT. The method for purifying BNNT according to the present disclosure is characterized in that pure BNNT is separated from synthesized BNNT based on length by inputting a mobile phase including synthesized BNNT into a column chromatography device.