Microstructural Characterization of a Hot Pressed Si₃N₄-TiN Composite Studied by TEM

抄録

Microstructures and material properties of TiN reinforced-Si₃N₄ composites, fabricated by hot pressing and using Si₃N₄, TiN and sponge Ti powders, were investigated. The sponge Ti powders in the Si₃N₄–TiN-sponge-Ti compacts are fully nitrided into TiN without residual Ti phase, but some residual pores remain. The Si₃N₄ grain boundaries, Si₃N₄/TiN interfaces and triple regions are covered with an amorphous phase. However, some reaction compounds estimated to be Si₁₀Ti₃W₂ phase are observed around fine TiN particles. The values of electrical resistivity, fracture strength and fracture toughness of the composite are 1.2×10⁻² Ωcm, 362 MPa and 5.3 MPam^1⁄2, respectively. The main reason for the relatively low mechanical properties is the existence of microcracks at the interface of Si₃N₄/large TiN grains, as well as the microstructure of fine, rod-like Si₃N₄ grains.