Pressure sintering ferrite(s) - without a die, using over-large punch pistons then cutting moulding to size

摘要

Method of sintering under pressure comprises at least one step in which a disc of material to be sintered is placed in a furnace, heated to the desired temp. between two cylindrical pistons of dia. greater than that of the insintered disc, with pressure applied between the pistons to compress the disc for a predetermined period of time; followed by second step in which the disc obtd. is cut so as retain only the central portion of the disc. Used in mfr. of polycrystalline ferrites esp. Ni1-xZuxFe2O4. where x= 0-1. with high density and fine grain size. The avoidance of a die allows the furnace size to be reduced. The problems of a fragile die are hence eliminated together with its high cost of mfr. The temp. to which the furnace needs to be heated in order to heat the moulding to a desired temp. may be less than when a die is used.