A heat dissipation sheet containing a silicone resin and a thermally conductive filler, wherein with respect to the cross-sectional shape of the thermally conductive filler, the average value of an aspect ratio of the 1st to 24th particles from the largest of biaxial average diameters, is in a range of 0.4 or more and 1.4 or less. In addition, an area ratio (Sr) of a total area S of cross-sectional shapes of the particles to a whole area of the cross-sectional view may be in a range of 20% or more and 80% or less, and the particle number ratio may be less than 1. Further, a thermal resistance ratio of a thermal resistance value when a pressure of 0.4 MPa is applied to a thermal resistance value when a pressure of 1.0 MPa is applied may be 1 or more.

A hexagonal boron nitride powder having an average longer diameter (L) of primary particles in the hexagonal boron nitride powder of more than 10.0 μm and 30.0 μm or less, an average thickness (D) of the primary particles in the hexagonal boron nitride powder of 1.0 μm 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 (1) to a thickness (d), [l/d], of 3.0 or more and 5.0 or less of 25% or more, 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 powder having an average longer diameter (L) of primary particles in the hexagonal boron nitride powder of more than 10.0 μm and 30.0 μm or less, an average thickness (D) of the primary particles in the hexagonal boron nitride powder of 1.0 μm 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 (1) to a thickness (d), [l/d], of 3.0 or more and 5.0 or less of 25% or more, a method for producing the hexagonal boron nitride powder, and a resin composition and a resin sheet each containing the hexagonal boron nitride powder.

The present disclosure relates to a novel sp.sup.2-sp.sup.3 hybrid crystalline boron nitride and its preparation process. A novel sp.sup.2-sp.sup.3 hybrid crystalline boron nitride allotrope, named Gradia BN, is synthesized using sp.sup.2 or sp.sup.3 hybridized boron nitride as raw materials under high-temperature and high-pressure. The basic structural units of Gradia BN are composed of sp.sup.2 hybridized graphite-like structural units and sp.sup.3 hybridized diamond-like structural units. Gradia BN disclosed in the present disclosure is a class of new sp.sup.2-sp.sup.3 hybrid boron nitride allotrope, whose crystal structure can vary with the widths and/or crystallographic orientation relationships of internal sp.sup.2 and/or sp.sup.3 structural units, and may have variable physical properties.

A solution is provided comprising boron nitride nanotubes (BNNTs) in a liquid solvent. An optical waveguide, such as an optical fiber, is contacted with the solution so as to form a layer of the solution supported on at least a portion of the optical waveguide. The liquid solvent is then removed from the layer of the solution supported on the optical waveguide in order to form a coating of the BNNTs on the optical waveguide. Further provided is a BNNT coated optical waveguide for use as a sensor.

The present application relates to a silanized boron nitride composite and a preparation method thereof, and more specifically, to a silanized boron nitride composite, which exhibits excellent mechanical properties and excellent thermal conductivity by realizing excellent dispersibility and improved affinity for epoxy through silane surface treatment, and a preparation method thereof.

A method of producing a resin sheet, including: mixing blocky boron nitride particles A, blocky boron nitride particles B, and a resin composition, and molding the resin composition to a sheet form and pressurizing the sheet form resin composition, the boron nitride primary particles a having a length in a shorter direction of 0.7 μm or less, the boron nitride primary particles b having a length in a shorter direction of 1 μm or more, the blocky boron nitride particles A having an average particle diameter of 30 μm or more, the blocky boron nitride particles B having an average particle diameter that is smaller than the average particle diameter of the blocky boron nitride particles A, the compressive strengths ratio of the blocky boron nitride particles A to the blocky boron nitride particles B being 1.2 or more. Thus, the thermal conductivity of a resin sheet can be enhanced.

A method of producing a resin sheet, including: mixing blocky boron nitride particles A, blocky boron nitride particles B, and a resin composition, and molding the resin composition to a sheet form and pressurizing the sheet form resin composition, the boron nitride primary particles a having a length in a shorter direction of 0.7 μm or less, the boron nitride primary particles b having a length in a shorter direction of 1 μm or more, the blocky boron nitride particles A having an average particle diameter of 30 μm or more, the blocky boron nitride particles B having an average particle diameter that is smaller than the average particle diameter of the blocky boron nitride particles A, the compressive strengths ratio of the blocky boron nitride particles A to the blocky boron nitride particles B being 1.2 or more. Thus, the thermal conductivity of a resin sheet can be enhanced.

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.

Boron nitride nanotube (BNNT)-polymide (PI) and poly-xylene (PX) nano-composites, in the form of thin films, powder, and mats may be useful as layers in electronic circuits, windows, membranes, and coatings. The processes described chemical vapor deposition (CVD) processes for coating the BNNTs with polymeric material, specifically PI and PX. The processes rely on surface adsorption of polymeric material onto BNNTs as to modify their surface properties or create a uniform dispersion of polymer around nanotubes. The resulting functionalized BNNTs have numerous valuable applications.