ＴｉＢ２基焼結体に関する研究

Abstract

It was difficult to produce dense and high strength TiB2 ceramics by using hot pressing. This paper described densification and strengthening mechanisms by using of three kinds of additives. First additives are CoB, FeB, Ni4B3 and NiB. Each additive makes dense TiB2 ceramics. The densification mechanism is explained as activated sintering and pressure effects. The ceramics which have higher transverse rupture strengths and lower porosities can be produced by adding the second each additive of VB2, NbB2, TaB2, CrB2, MnB2, MoB2, Mo2B5 and W2B5. The higher transverse rupture strength has been caused mainly by suppressing grain growth of TiB2 with the solid solution between TiB2 and the hexagonal boride such as TaB2, and caused secondarily by the lattice strain of TiB2.Hence, it is expected that TiB2 ceramics having the higher mechanical shock resistance can be made from the raw materials with smaller particle size of TiB2. However, fine raw powders gave more pores, because of oxidizing during mixing. Final additives are cubic carbides such as TiC, ZrC and HfC. When the each additive adds to TiB2-1%CoB-6%TaB2 mixed powder, the ceramics have the smaller particle size and the lower porosity.This lower porosity, for example, may be formed by a solid solution of M(C, O) and deoxidation of the raw TiB2 powder.