Study On Synthesis And Properties Of Ternary Laryerd Carbide Ti₃SiC₂

(Titanium silicon carbide) attracts increasing interest owing to their unique properties. Ti3SiC2 combines unusual properties of both metals and ceramics. Like metals, it is a good thermal and electrical conductor, relatively soft. Like ceramics, it is elastically stiff; exhibit excellent high temperature mechanical properties. It is resistant to thermal shock and unusually damage tolerant, and exhibit excellent corrosion resistance. Above all, unlike conventional carbides, they can be machined by using conventional tools without lubricant, which is of great technological importance for their application. Additionally, Ti3SiC₂ is an exceptional solid lubricant with an ultra-friction. These excellent properties mentioned above make them another family of technically important materials. To date, many methods such as chemical-vapor deposit (CVD), self-propagating high temperature reaction synthesis (SHS), hot pressing (HP), hot-isostatic pressing (HIP) and spark plasma sintering (SPS) have been used for the synthesis of Ti3SiC₂Unfortunately, it is difficult to be synthesized as a pure phase, being often accompanied by unacceptably large amounts of TiC and titanium silicides (TixSiy). Because aluminum has a low melting point, and Ti3SiC₂ has the same structure and similar properties as those of Ti3SiC₂, the idea that addition of aluminum is used as an additive for the synthesis of Ti3SiC₂ has been proposed. Both spark plasma sintering and hot pressing were utilized for the synthesis of single-phase dense Ti3SiC₂. Also, the microstructures, the physical properties as well as oxidation behavior of the obtained materials were investigated, respectively.SPS was used to synthesize Ti3SiC₂ from the mixtures of both Ti/Si/C and Ti/SiC/C. Also, effect of aluminum on the synthesis of Ti3SiC₂ was especially investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) coupled with energy-dispersive spectroscopy (EDS) were utilized to investigate the phase composition and the morphology characteristics of the products. In addition, the SPS process parameters were also analyzed to study the reaction characteristics. The results indicated that appropriate addition of Al accelerates the reaction synthesis, and favors the crystal growth of Ti3SiC₂, as well as considerably improves Ti3SiC₂ content. Fully dense, essentially single-phase Ti3SiC₂ is fabricated by spark plasma sintering (SPS) 3Ti/lSi/0.2Al/2C at 1250℃ under 30 MPa for 10 minutes. The obtained Ti3SiC₂ grains are well developed and plate-shape with a size of 5m and 25m, in thickness and elongated dimension,respectively.In chapter 3, the synthesis of single-phase materials of both Ti3AlC₂ and Ti3AlC₂ was conducted by HP method. For the synthesis of Ti3AlC₂, two kinds of powder mixtures Ti/Si/C and TiC/Ti/Si were used and the effect of aluminum on the synthesis of Ti3AlC₂ were together investigated. Also, for the synthesis of Ti3AlC₂, silicon was chosen as the synthesis additive. Characterized by XRD, SEM and EDS, the results indicated that addition of aluminum and silicon in the starting mixtures improves the reaction synthesis of Ti3AlC₂, and Ti3AlC₂, respectively. Ti3AlC₂ with 98.2% purity and 98.8% theoretic density was fabricated by hot pressing 2TiC/Ti/Si/0.2Al at the temperature of 1400℃, and under the pressure of 30 MPa for 2 hours, and essentially single-phase Ti3AlC2 with 98.6% density was prepared from the starting mixture of HP the 2TiC/Ti/Al/0.2Si under the same condition.Chapter 4 deals with the microstructures of SPS Ti3SiC2, HP Ti3SiC2, and HP Ti3AlC₂ The lattice parameters of Ti3AlC₂ were calculated by Rietveld analysis and measured using silicon as a standard additive. The morphology characteristics of the grains were investigated by the secondary electron images of fracture surfaces of sintered products. Energy-dispersive spectroscopy and electron-probe microanalysis (EPMA) were used to study the chemical composition of minerals, and the distribution of...