Abstract: Disclosed is a fiber of an organic, inorganic or metallic material or a simple substance wherein ultrafines of an inorganic or metallic material or a simple substance having an average particle diameter of 0.005-1 .mu.m are uniformly dispersed and deposited on 8-90% of the surface in a single layer. The fiber is produced by exposing a fiber of an organic, inorganic or metallic material or a simple substance to a gaseous stream forming ultrafines of an inorganic or metallic material or a simple substance by a vapor phase process, thereby contacting said ultrafines in the gaseous stream with said fiber in a state wherein the ultrafines are still active. The treated fiber is useful as a reinforcing material for a fiber reinforced composite.

Abstract: A particle of an inorganic or metallic material which is coated on the surface with ultrafines of an inorganic or metallic material. The coated particle is produced by introducing the particles of the inorganic or metallic material to be coated into a stream carrying the ultrafines of the inorganic or metallic material formed in a vapor phase and bringing the particles to be coated into contact with said ultrafines in a fluidized state. The coated particles are used for the production of a sintered product.