Preparation Of Ti₃SiC₂/Cu Composites And Application Basic Research Of Vacuum Contact

High-performance Ti3SiC2/Cu composites, which was used to fabricate vacuum arc-extinguishing contactor, has been prepared and investigated in this work. Furthermore, detailed information about mechanical and electrical properties of Ti3SiC2/Cu composites was obtained. The thesis is expounded in seven chapters: introduction of Ti3SiC2/Cu composites, wettability and wetting behavior of Ti3SiC2/Cu composites, preparation of high purity Ti3SiC2powder, preparation and characterization of high performance Ti3SiC2/Cu composites, and measurement and analysis of the Chopping current level, breaking ability, line frequency withstand voltage capability of Ti3SiC2/Cu vacuum contactor.The innovations of this work can be drawn mainly as following:1. Wetting behavior between Cu and Ti3SiC2at high temperature and its influence factors were revealed. Furthermore, the interface reaction mechanism had been discussed through phase composition measurement and microstructure observation of Ti3SiC2/Cu interface, which provided a theoretical basis for the preparation of high-performance Ti3SiC2/Cu vacuum contactor material.2. High purity (>92wt.%) Ti3SiC2powders had been successfully synthesized from TiH2, Si and TiC starting powders without any additive, which can be directly used to prepare of Ti3SiC2/Cu vacuum contactor.3. Ti3SiC2/Cu composites with excellent mechanical and electrical properties were obtained by hot-press sintering and pressureless sintering. Furthermore, the composition, preparation process and technological parameters of the composites were optimized.4. The chopping current level, breaking ability, ablation resistance and line frequency withstand voltage capability of Ti3SiC2/Cu vacuum contactors were tested under the condition of practical application. The results showed that Ti3SiC2/Cu has excellent electrical contact properties, and it is a new type of vacuum contactor material with great application potential.The main academic significance and engineering values of the present work are listed as following:1. An excellent wettability between Ti3SiC2and Cu was observed at elevated temperature, and the wetting process belongs to reactive wetting. The contact angle between Ti3SiC2and Cu decreased obviously with increasing temperature, and down to15.1°at1270℃. Some new phases, such as TiCx and Cu-Si intermetallics, were formed at the interface of Ti3SiC2and Cu. At the same time, Cu diffused into Ti3SiC2and showed a gradient distribution in the reaction layer. The reaction and diffusion behavior improve the interfacial bonding and the wettability of the Ti3SiC2/Cu system.2. High-purity (>92wt.%) Ti3SiC2powder was successfully synthesized through vacuum pressureless sintering from TiH2, Si and TiC mixture powders (molar ratio of the three raw materials is1:1.25:1.8～1.9) without any additive. The synthesis procedure was:increasing the temperature to1450-1480℃with a heating rate of30℃/min, and then holding10min.3. Performances of Ti3SiC2/Cu composites were influenced significantly by the Ti3SiC2content. The suitable contents of Ti3SiC2reinforcement in Ti3SiC2/Cu composites were located40-60vol.%.4. Different sintering process had been used to prepare Ti3SiC2/Cu vacuum contactor composites. The appropriate hot-press sintering technologies were that: sintering temperature900～1100℃with heating rate30℃/min, and hot-pressing pressure30MPa with holding time2h. For pressureless sintering process, the best sintering parameters were that:sintering temperature1250～1400℃with heating rate30℃/min, and holding time Ih. The performance of Ti3SiC2/Cu composites prepared by hot-press sintering is superior to the one obtained through pressureless sintering.5. The chopping current level of Ti3SiC2/Cu vacuum contactors was tested under the condition of practical application. It is indicated that the lowest chopping current level was1.68A for the40vol.%Ti3SiC2/Cu vacuum contactorprepared by hot-press sintering, and the lowest value was2.48A for the40vol.%Ti3SiC2/Cu vacuum contactor prepared by pressureless sintering.6. The breaking ability and line frequency withstand voltage capability of Ti3SiC2/Cu vacuum contactors were tested under the condition of practical application. Ultimate breaking capacities are14.30KA and11.40KA for50vol.%Ti3SiC2/Cu contactor prepared by hot-press sintering and40vol.%Ti3SiC2/Cu prepared by pressureless sintering, respectively. The line frequency with stand voltage capability of all Ti3SiC2/Cu contactor can reached65KV. No cracks can be found on the surface of Ti3SiC2/Cu contactor undergone different degrees of arc erosion for all the experimental materials, which showed an excellent performance of Ti3SiC2/Cu vacuum contact materials.