Patent ID: 8187710
Filing Date: 2012-05-29
Classification: B82Y,C01P,C04B,C09C,H01B,H01G,H05K,Y10T

Abstract:
1. A process for producing insulated ultrafine powder composed of electroconductive ultrafine powder selected from the group consisting of stannic oxide doped with antimony, indium trioxide doped with tin, zinc oxide doped with aluminum or gallium, and a barium plumbate, which is in the form of sphere, spheroid or acicular each having a minor axis in the range of 1 to 100 nm, and an insulating film, which has a thickness in a range of 0.3 nm to a thickness not larger than a thickness of said minor axis of the electroconductive fine powder, which is made of a metal oxide having a relative dielectric constant of at least 20, and which is applied onto said electroconductive ultrafine powder, comprising any of the steps (a), (b) and (c), wherein step (a) comprises dispersing electroconductive ultrafine powder in an organic solvent; adding a metal alkoxide in the resultant dispersion; and precipitating a metal oxide on the surfaces of said electroconductive ultrafine powder by sol-gel reaction, the step (b) comprises dispersing electroconductive ultrafine powder in an aqueous solution of a metal salt; adding an alkali in the aqueous solution; precipitating a metal hydroxide on the surfaces of said electroconductive ultrafine powder; conducting dehydration condensation reaction by drying; and sticking a metal oxide onto the surfaces of said electroconductive ultrafine powder, and the step (c) comprises simultaneously or consecutively adding an aqueous solution of a metal salt and an aqueous solution of an alkali to an aqueous dispersion of the electroconductive ultrafine powder; precipitating a metal hydroxide on the surfaces of said electroconductive ultrafine powder; conducting dehydration condensation reaction by drying; and sticking a metal oxide onto the surfaces of said electroconductive ultrafine powder, and a subsequent step of calcining the metal oxide precipitated or stuck to the surfaces of said electroconductive ultrafine powder at a temperature ranging from a temperature which is higher than a temperature which is 900° C. lower than the melting point of the metal oxide to a temperature lower than the melting point thereof.