Patent ID: 7425287

Claim:
A surface modification method comprising (a) bringing, into a high-temperature flame formed by use of a combustible gas and a combustion-supporting gas, inorganic oxide powder A having an average particle size falling within a range of 0.5 to 200 μm as measured by means of laser diffraction/scattering particle size analysis; and (b) bringing again the resultant powder into a high-temperature flame formed by use of a combustible gas and a combustion-supporting gas, to thereby modify the surfaces of particles of powder A, wherein powder A comprises particles of an oxide of Al, Mg, Ca, Ti, or Si, or particles of a mixed crystal of such oxides, and wherein powder A comprises particles having a spherical degree of at least 0.7 as defined by the following formula [1]: spherical degree=(the circumference of a circle having the same area as that of a projection image of a particle)/(the length of the contour of the projection image of the particle) [1].