Songlan Yang

Synthesis of single-phase Ti3SiC2 powder

Abstract In this study, free 2Ti/2Si/3TiC powder mixture was heated at high temperatures in vacuum, in order to reveal the possibility for the synthesis of high Ti 3 SiC 2 content powder. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the evaluation of phase identities and the morphology of the powder after different treatments. Results showed that almost single phase Ti 3 SiC 2 powder (99.3 wt.%) can be synthesized by heat treatment with free 2Ti/2Si/3TiC powders in vacuum at 1210°C for about 3 h. The nucleation and growth of Ti 3 SiC 2 within TiC particles was observed. The typical appearance of the formed Ti 3 SiC 2 is equiaxed with particle size of 2–4 μm. Effects of temperature and heating time on the morphology and the particle sizes of the synthesized Ti 3 SiC 2 powders are not obvious.

Ti3SiC2 powder synthesis from Ti/Si/TiC powder mixtures

Abstract Various heat treatments in vacuum were carried out on free Ti/Si/TiC powder mixtures with molar ratios of 2:2:3 and 1:1:2, in order to reveal the effect of original powder composition on the Ti 3 SiC 2 powder synthesis. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the identification of phase constitutions and the characterization of the synthesized powder. During the synthesis process, Ti 5 Si 3 was found to be the only intermediate phase in both cases and part of which remained in the final synthesized powder together with Ti 3 SiC 2 . The optimal temperature range for the formation of Ti 3 SiC 2 was 1210–1300xa0°C; above 1300xa0°C the content of Ti 3 SiC 2 decreased significantly with temperature. At 1300xa0°C in the time range of 0.5–4 h, the effect of heating time on the Ti 3 SiC 2 content was not obvious.

Formation of Ti3SiC2 from Ti-Si-TiC powders by pulse discharge sintering (PDS) technique

Abstract.nTi/Si/TiC powder mixture with molar ratios of 2:2:3 were sintered at various temperatures from 700–1300xa0°C for 15xa0min by PDS technique. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the evaluation of phase composition in different samples for the understanding of the sintering mechanism for this system. Results showed that Ti5Si3 formed as the intermediate phase during sintering. The reaction between Ti5Si3 and TiC as well as Si induces the formation of Ti3SiC2, and TiSi2 appears as the byproduct in this process. At temperature above 1000xa0°C, TiSi2 reacts with TiC to form Ti3SiC2. High Ti3SiC2 phase content bulk material can be synthesized at 1300xa0°C for 15xa0min.

Oxidation of Ti3SiC2 at 1000°C in Air

Oxidation of polycrystalline Ti3SiC2 was investigated at 1000°C by XRD and SEM. Results show that a thin SiO2-rich scale forms after short-term oxidation, but it cannot prevent further oxidation effectively. The TiO2 content increased with increasing time and covered the whole surface eventually. For the long-term oxidation, the oxide scales are layered, the outer layer is comprised of pure TiO2, while the inner layer is a mixture of TiO2 and SiO2. The position of the pre-formed SiO2 layer indicates that it can serve as an initial marker for the subsequent oxidation.