Synthesis and characterization of the properties of Ti3SiC2/SiC and Ti3SiC2/TiC composites

In 1996, the ternary compound titanium silicon carbide (Ti3SiC2) was for the first timesynthesized as a single-phase, fully dense compound. Its characterization revealed aunique combination of properties. For its high fracture toughness, low hardness toelastic modulus ratio and excellent damage tolerance, it was dubbed a soft ceramic. Italso displayed good thermal shock and oxidation resistance. In this work, thereinforcement of this material with silicon carbide and titanium carbide particles wasexplored with the intention of improving mechanical and oxidation properties. Thecomposites were synthesized by HIPing of starting powders, following the sameprocessing as for pure Ti3SiC2.It was found that the particles affected the microstructureof the Ti3SiC2 matrix, reducing the grain size of a material that otherwise would havebeen coarse-grained. Mechanical properties of the composites were investigated throughfour-point bend tests and Vickers indentations. The flexural strength of the compositeswas lower than expected from the grain size of the matrix and was explained by athermal expansion coefficient mismatch. Fracture toughness of the composites was alsolower than for Ti3SiC2. However, the hardness and damage tolerance were improved.Oxidation experiments were conducted in air at temperatures ranging between 875°Cand 1220°C. The oxidation behavior of the Ti3SiC2/SiC composite was found to besubparabolic at 925°C, but from 1010°C to 1220°C, it was parabolic with a transition tolinear behavior. The oxidation of the Ti3SiC2/TiC composite was parabolic at 875°C, andfrom 975°C to 1220°C, showed the same behavior as the other composite. The growth ofthe oxide scale of the composites was fitted with a multiple-law model. It wasdetermined that the oxidation of the composites occurred by diffusion of oxygen inwardand titanium outward. The parabolic component of the oxide scale growth was found tocorrespond to the diffusion of oxygen inward, as in pure Ti3SiC2. The correspondingparabolic constants were found to be lower for Ti3SiC2/SiC and higher for Ti3SiC2/TiC,compared to the pure material.M.S., Materials Engineering -- Drexel University, 200