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.

A treatment method for modifying the reflected color of a sapphire material surface comprising bombardment by a single- and/or multi-charged gas ion beam so as to modify the reflected color of the treated sapphire material surface, wherein the ions are selected from ions of the elements from the list consisting of helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), boron (B), carbon (C), nitrogen (N), oxygen (O), fluorine (F), silicon (Si), phosphorus (P) and sulphur (S).

Alumina having excellent electrolytic solution stability, a slurry containing the same, an alumina porous film using the same, a laminated separator, a nonaqueous electrolyte secondary battery and a method for manufacturing the nonaqueous electrolyte secondary battery are provided. Alumina is provided including one or more selected from K, Mg, Ca, Sr, Ba and La in the total amount of 200 to 50,000 ppm by mass, wherein a surface concentration of one or more elements is 0.5 to 20 at % in total. Alumina is provided in which in an infrared absorption spectrum of the alumina obtained by Fourier-transform infrared spectroscopy, a peak having an intensity larger than that of a baseline defined by a line segment connecting an intensity at 3,400 cm.sup.1 and an intensity at 3,500 cm.sup.1 and having a half width of 90 cm.sup.1 or less, does not exist in a range of 3,400 to 3,500 cm.sup.1.

The present invention provides a resin composition including aluminum oxide (A) containing molybdenum having a size on the order of m or less and a resin (B); and a resin molded body formed by molding the resin composition. Also, the present invention provides a heat-dissipating material containing the resin composition; and a heat-dissipating member containing the resin molded body. The heat-dissipating member of the present invention can be used for electronic parts such as electronic devices, electric devices, OA devices or for LED illumination.

Disclosed is a low-temperature preparation method for a polyaryletherketone inorganic composite material, in particular a method for the low-temperature synthesis of a polyaryletherketone resin on a nano/micron-scale inorganic seedbed. The method comprises: adding nano/micron-scale inorganic material particles (mono-element or multi-element of aluminium oxide, silicon oxide, hydroxyapatite and the like) to a reaction system of a polyaryletherketone high-molecular polymer, and realizing the blending of inorganics in a high proportion (>50%) and organics while completing the one-step polymerization reaction, so that the common thermal degradation problem of the organic materials induced during the melting, blending and thermal processing is avoided. The composite material can be used in the technical fields of aerospace, industry, medicine and the like.

A method of producing new hydrophobic aluminas by i) providing a slurry comprising an alumina compound, the slurry having a pH of above 5.5; ii) mixing an organic composition comprising carboxylic acids with long hydrocarbon chains with the slurry to form an acid modified slurry; iii) hydrothermally conditioning the acid modified slurry to form a hydrothermally aged slurry; and iv) drying the hydrothermally aged slurry. The new hydrophobic aluminas have surface modified structures distinguished by a low humidity content and very small nanoparticles. These new hydrophobic aluminas can be uniformly dispersed in a substrate, for example polymers.

Provided are a molding step (A) of preparing an alumina molded body 11 from a molding raw material which contains an alumina raw material powder having an average particle size of 2 m to 5 m and a molding additive, and a sintering step (B) of preparing an alumina molded body 12, which becomes a spark plug insulator 1, by sintering the alumina molded body 11. At the sintering step (B), the alumina molded body 11 is conveyed to a continuous furnace 100 provided with a heating zone Z1 which is heated to 700 C. to 1600 C. by a heating means 401, followed by introducing oxygen gas to control the heating zone Z1 to have a high oxygen atmosphere with an oxygen concentration exceeding 20 mol %.

Provided are oxide composite particles closer to a sphere that are mixed with a resin to obtain a resin composition having low dielectric constant and low dielectric loss tangent. The oxide composite particles containing silica and an oxide of aluminum (a single oxide or a composite oxide, or both), in which the oxide composite particles contain 10 to 90% by mass of an ?-cristobalite crystal phase, 50% by mass or less of an ?-alumina crystal phase, and more than 10% by mass of a mullite crystal phase, and an elemental ratio of aluminum to silicon (aluminum/silicon) as determined by X-ray photoelectron spectroscopy is 0.1 or more.

Provided are spherical alumina particles to be mixed with a resin to obtain a resin composition having low dielectric loss tangent. The spherical alumina particles containing 90% by mass or more of an ?-alumina crystal phase, in which the spherical alumina particles have a half-width of an ?-alumina (113) peak of 0.124? or less as observed by X-ray diffraction and an average particle diameter of 0.5 to 40 ?m.

Provided are spherical alumina particles to be mixed with a resin to obtain a resin composition having low dielectric loss tangent. The spherical alumina particles containing 90% by mass or more of an ?-alumina crystal phase, in which the spherical alumina particles have a half-width of an ?-alumina (113) peak of 0.124? or less as observed by X-ray diffraction and an average particle diameter of 0.5 to 40 ?m.