A method for producing a transparent alumina sintered body includes (a) the step of preparing an alumina raw material powder containing a plate-like alumina powder having an aspect ratio of 3 or more so that the mass ratio R1 of F to Al in the alumina raw material powder is 5 ppm or more, and forming a compaction raw material containing the alumina raw material powder into a compact, and (b) the step of pressure-sintering the compact at a temperature at which F evaporate to yield a transparent alumina sintered body.

The invention provides a plurality of substantially same planar pigment flakes, each formed of one or more thin film layers. Each flake has a face surface and a flake border delimiting the face surface; the flake border undulates in the plane of the flake. The flakes have a pre-selected shape, may have a symbol or a grating thereon. A method of manufacturing of these flakes including the steps of: (a) providing a substrate having a plurality of one-flake regions and a plurality of depressions or protrusions disposed therebetween and not extending into the one-flake regions, (b) coating the substrate with a releasable coating, and (c) removing the releasable coating and breaking it into the flakes; wherein two adjacent of the one-flake regions are separated by at least three of the depressions or protrusions for facilitating the breaking of the releasable coating into the flakes.

There is provided a near-infrared absorbing fine particle dispersion liquid containing near-infrared absorbing fine particles, thereby as well as exhibiting near-infrared light absorption properties and suppressing a scorching sensation on the skin when used in structures such as window materials and the like, also enabling usage of communication devices, imaging devices, sensors and the like that employ near-infrared light through these structures, a near-infrared absorbing film or a near-infrared absorbing glass, a dispersion body or a laminated transparent substrate, the dispersion liquid containing at least composite tungsten oxide fine particles and antimony doped tin oxide fine particles and/or tin doped indium oxide fine particles as near-infrared absorbing fine particles, wherein in the composite tungsten oxide fine particles, an average value of a transmittance in a wavelength range of 800 to 900 nm is 30% or more and 60% or less, and an average value of a transmittance in a wavelength range of 1200 to 1500 nm is 20% or less, and a transmittance at a wavelength of 2100 nm is 22% or less, when a visible light transmittance is 85% at the time of calculating only light absorption by the composite tungsten oxide fine particles, and containing mixed particles of the composite tungsten oxide fine particles and antimony-doped tin oxide fine particles and/or tin-doped indium oxide fine particles dispersed in a liquid medium, wherein the liquid medium is selected from rater, an organic solvent, an oil and fat, a liquid resin, a liquid plasticizer for plastics, or a mixture thereof, wherein when a visible light transmittance is adjusted to 85% at the time of calculating only light absorption by the near-infrared absorbing fine particles in the dispersion liquid by diluting with the liquid medium, an average value of a transmittance in the wavelength range of 800 to 900 nm is 30% or more and 60% or less, an average value of a transmittance in the wavelength range of 1200 to 1500 nm is 20% or less, and a transmittance at the wavelength of 2100 nm is 11% or less.

The present invention provides a method of preparing a positive electrode active material for a secondary battery including preparing a first transition metal-containing solution including a nickel raw material, a cobalt raw material, and a manganese raw material and a second transition metal-containing solution including a nickel raw material, a cobalt raw material, and a manganese raw material in a concentration different from that of the first transition metal-containing solution; preparing a reaction solution, in which nickel manganese cobalt-based composite metal hydroxide particles are formed, by adding an ammonium cation-containing complexing agent and a basic compound as well as the second transition metal-containing solution to the first transition metal-containing solution and performing a co-precipitation reaction in a pH range of 11 to 13.

The present invention provides a positive electrode active material for a secondary battery, which includes a core, a shell disposed to surround the core, and a buffer layer which is disposed between the core and the shell and includes pores and a three-dimensional network structure connecting the core and the shell, wherein, the core, the shell, and the three-dimensional network structure of the buffer layer each independently include a lithium nickel manganese cobalt-based composite metal oxide and at least one metallic element of the nickel, the manganese, and the cobalt has a concentration gradient that gradually changes in any one region of the core, the shell, and the entire positive electrode active material.

A method for preparing a carbon powder from an organic polymer material and a method for detecting the crystal morphology in the organic polymer material. A method for preparing a carbon material product comprises a carbonization step in which: a straight-chain polymer material containing nanoscale crystals is carbonized by using a strong oxidizing agent free of heavy metal ions, thus acquiring a nanoscale carbon material. Also disclosed is a method for acquiring either a material having a carbonized surface or a powder material containing graphene by using an acid in treating the organic polymer material.

The present invention relates to a method for preparing a sulfonated graphene from an organic material and to the sulfonated graphene prepared therefrom. The method comprises the following steps: a first contact step: a reaction medium containing oxidative sulfonating agent is allowed to come into contact with the organic macromolecular material at a first temperature; and, a second contact step: when the first contact step is completed, in same reaction medium, the reaction temperature is increased to a second temperature to allow for continued reaction, thus producing the sulfonated graphene.

A thermal method of forming ferric oxide nano/microparticles with predominant morphology is described using different solvents. Methods of using the Fe.sub.3O.sub.4 nano/microparticles as catalysts in the reduction of nitro compounds with sodium borohydride to the corresponding amines and decomposition of ammonium salts.

A thermal method of forming ferric oxide nano/microparticles with predominant morphology is described using different solvents. Methods of using the Fe.sub.3O.sub.4 nano/microparticles as catalysts in the reduction of nitro compounds with sodium borohydride to the corresponding amines and decomposition of ammonium salts.

A plate-like alumina powder production method of the present invention comprises placing a transition alumina and a fluoride in a container such that the transition alumina and the fluoride do not come into contact with each other and then performing heat treatment to obtain a plate-like -alumina powder. The transition alumina is preferably at least one selected from the group consisting of gibbsite, boehmite, and -alumina. It is preferable that the amount of the fluoride used is set such that the percentage ration of F in the fluoride to the transition alumina is 0.17% by mass or more. The container preferably has a volume such that a value obtained by dividing the mass of F in the fluoride by the volume of the container is 6.510.sup.5 g/cm.sup.3 or more. The heat treatment is preferably performed at the temperature of 750 to 1,650 C.