Study on the Sintering of TiB₂-Based Ceramics

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.