A p-type semiconductor film including heterofullerene having a further sufficiently high hole mobility is provided. The p-type semiconductor film contains heterofullerene in which n+r number (where n and r are both positive odd numbers) of carbon atoms constituting a fullerene are substituted by n number of boron atom or atoms and r number of nitrogen atom or atoms.

A method for preparing a positive electrode active material for a secondary battery is provided. The method includes providing a lithium complex transition metal oxide which contains nickel (Ni) and cobalt (Co), and contains at least one selected from the group consisting of manganese (Mn) and aluminum (Al); removing lithium by-products present on a surface of the lithium complex transition metal oxide by washing the lithium complex transition metal oxide with water; and mixing the washed lithium complex transition metal oxide, a cobalt (Co)-containing raw material, and a boron (B)-containing raw material and performing high-temperature heat treatment at a temperature of 600 C. or higher.

A method for preparing a positive electrode active material for a secondary battery is provided. The method includes providing a lithium complex transition metal oxide which contains nickel (Ni) and cobalt (Co), and contains at least one selected from the group consisting of manganese (Mn) and aluminum (Al); removing lithium by-products present on a surface of the lithium complex transition metal oxide by washing the lithium complex transition metal oxide with water; and mixing the washed lithium complex transition metal oxide, a cobalt (Co)-containing raw material, and a boron (B)-containing raw material and performing high-temperature heat treatment at a temperature of 600 C. or higher.

A method for producing pellets of sintered material, comprising: a) forming calibrated pre-compacts by first uniaxial pressing of equal portions powder at a first threshold below the maximum green density threshold of the powder; b) providing a pressing tool set comprising a die having a plurality of cavities and pressure pistons; c) placing the pre-compacts in the cavities with first and second sintered boron nitride disks, having a thickness in the millimetre range and a density >=90%; d) forming calibrated compacts by second uniaxial pressing of the pre-compacts using the pressure pistons at a second threshold greater than the first threshold, which is less than or equal to the maximum green density of the powder; e) forming sintered compacts by applying pressure and a pulsed current to the pressing tool set to bring about a rapid rise in temperature according to a temperature-, pressure- and duration-controlled SPS sintering cycle.

A method for producing pellets of sintered material, comprising: a) forming calibrated pre-compacts by first uniaxial pressing of equal portions powder at a first threshold below the maximum green density threshold of the powder; b) providing a pressing tool set comprising a die having a plurality of cavities and pressure pistons; c) placing the pre-compacts in the cavities with first and second sintered boron nitride disks, having a thickness in the millimetre range and a density >=90%; d) forming calibrated compacts by second uniaxial pressing of the pre-compacts using the pressure pistons at a second threshold greater than the first threshold, which is less than or equal to the maximum green density of the powder; e) forming sintered compacts by applying pressure and a pulsed current to the pressing tool set to bring about a rapid rise in temperature according to a temperature-, pressure- and duration-controlled SPS sintering cycle.

The carbon nanotube pellets according to the present invention are produced by using only a small amount of solvent and have increased apparent density. The present invention can improve the problems of the change of the content generated by scattering of powders and safety issues by using carbon nanotubes in the form of pellet rather than carbon nanotubes in the form of powder in composite materials. And since the density of the pellet form is higher than that of the powder form, transport, transfer and improvement become easier. Therefore, it can be more effectively applied to the manufacturing of composite materials.

The carbon nanotube pellets according to the present invention are produced by using only a small amount of solvent and have increased apparent density. The present invention can improve the problems of the change of the content generated by scattering of powders and safety issues by using carbon nanotubes in the form of pellet rather than carbon nanotubes in the form of powder in composite materials. And since the density of the pellet form is higher than that of the powder form, transport, transfer and improvement become easier. Therefore, it can be more effectively applied to the manufacturing of composite materials.

A production method of boron carbide nano-sized particles and/or submicron particles includes the following sequential steps: obtention of a fluid mixture including elemental boron, glycerin and one or more carboxylic acid, wherein a molar ratio of glycerin to the one or more carboxylic acids is within a range between 10:1 and 10:7.5. Heating of the fluid mixture to obtain a first mid-product in a form of a gel including borate ester bonds. Solidification of the first mid-product by heating a reaction product to obtain a second mid-product in solid form. Sintering the second mid-product to obtain boron carbide in a form of particles.

A production method of boron carbide nano-sized particles and/or submicron particles includes the following sequential steps: obtention of a fluid mixture including elemental boron, glycerin and one or more carboxylic acid, wherein a molar ratio of glycerin to the one or more carboxylic acids is within a range between 10:1 and 10:7.5. Heating of the fluid mixture to obtain a first mid-product in a form of a gel including borate ester bonds. Solidification of the first mid-product by heating a reaction product to obtain a second mid-product in solid form. Sintering the second mid-product to obtain boron carbide in a form of particles.

An hBN powder containing an aggregate of primary particles of hBN, the hBN powder having 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 10 to 25, a tap density of 0.80 g/cm.sup.3 or more, and a BET specific surface area of less than 5.0 m.sup.2/g, in which a particle size distribution curve showing a frequency distribution based on volume of the hBN powder is a bimodal distribution curve having a first peak and a second peak in a range of a particle size of 500 m or less and having a peak height ratio of a second peak height (H.sub.B) to a first peak height (H.sub.A), [(H.sub.B)/(H.sub.A)], of 0.90 or less, a method for producing the same, and a resin composition and a resin sheet each comprising the hBN powder.