Process for producing oxide coated fine metal particles

A process for producing oxide coated fine metal particles, comprising the steps of:

• mixing a metal powder material with an oxide powder material of at least one member selected from the group consisting of an oxide, a complex oxide and an oxy-acid salt, wherein each of said oxide, said complex oxide and said oxy-acid salt does not contain as a main component a metal element which is a main component of the metal powder material, thereby to obtain a powder material mixture,
• wherein said mixing step comprises a compositing sub-step of compositing said metal powder material and said oxide powder material to produce as the powder material mixture composite particles in which particles in the metal powder material do not agglomerate together but are individually covered on respective entire surfaces with a multiple of particles in the oxide powder material that have been dispersed and attached and/or adhered;
• supplying the powder material mixture into a thermal plasma to make a vapor-phase mixture;
• and then
• quenching the vapor-phase mixture to form said oxide coated fine metal particles which comprise:
• core particles made of fine elemental metal particles that are finer than said metal powder material;
• and
• a coating layer with which said core particles are covered;
• wherein said coating layer comprises at least one member selected from the group consisting of:
• (1) said oxide;
• (2) said complex oxide;
• (3) said oxy-acid salt;
• (4) a complex compound of said oxide or said complex oxide or said oxy-acid salt, and an oxide of said metal element;
• and
• (5) a complex salt of said oxide or said complex oxide or said oxy-acid salt, and said oxide of said metal element.