| Summary: | 博士 === 國立成功大學 === 材料科學及工程學系 === 107 === Ti3SiC2 ceramics and TiC/Ti3SiC2 composites have been synthesized by reactive hot-pressed sintering. The influences of composition and preparation parameters on the purity, microstructure, and the reaction mechanism of Ti3SiC2 ceramics were investigated. The mechanical properties of the TiC/Ti3SiC2 composites and highly pure Ti3SiC2 ceramics were also estimated. Results indicated that the content of Ti3SiC2 increased with increasing hot-pressed temperature up to 1500°C. The amount of excess Si additive had substantial effects on the purity of Ti3SiC2 at the lower hot-pressed temperatures. The samples with 3Ti/SiC/C/0.1Si (molar ratio) hot-pressed at 1500°C for 1 h were predominantly Ti3SiC2 phase (Purity higher than 99 vol%), and the grains exhibited elongated in shape with a grain size of 3 – 8 m. The four-point bending strength, fracture toughness, hardness, and apparent density were 335 MPa, 7 MPa·m1/2, 3 GPa and 4.51 g/cm3, respectively. The deformation response of high pure Ti3SiC2 ceramics have been investigated by performing ballistic impact testing at a range of low velocities. The typical fracture surface of the fragments exhibited transgranular fracture combined with intergranular fracture. Most fracture mechanisms were similar to energy-absorbing mechanisms observed in the vicinity of the indentation. The Si plane was depleted and the remaining thin lamella consisted of six close-packed Ti planes, with five C planes in-between, showing identical stacking as {111} planes in TiC. The Hugoniot elastic limit was estimated to be 10 GPa. The TiC/Ti3SiC2 composite sample exhibits maximum flexural strength of 627 MPa. The composite synthesized from 2TiC/1Ti/1.1Si (molar ratio) composition shows better mechanical properties compared to 2TiC/1Ti/1Si (molar ratio) composition.
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