HPHT Synthesis of Different Shape Coarse-Grain Diamond Single Crystals

Synthesis of coarse-grain diamond crystals is studied in a China-type SPD6× 1670T cubic high-pressure apparatus with high exact control system. To synthesize high quality coarse-grain diamond crystals, advanced indirect heat assembly, powder catalyst technology and optimized synthesis craft are used. At last, three kinds of coarse- grain diamond （about 0.85 mm） single crystals with hexahedron, hex-octahedron and octahedron are synthesized successfully under HPHT （about 5.4 GPa, 1300-1450℃）. The growth characters of different shape crystals are discussed. The results and techniques might be useful for the production of coarse-grain diamonds.     

Rare earth Ce-modified (Ti,Ce)/a-C:H carbon-based film on WC cemented carbide substrate

WC cemented carbide suffers severe wear in water environments. A novel carbon-based film could be a feasible way to overcome this drawback. In this study, a rare earth Ce-modified(Ti,Ce)/a-C:H carbon-based film is successfully prepared on WC cemented carbide using a DC reactive magnetron sputtering process. The microstructure, mechanical properties,and tribological behavior of the as-prepared carbon-based film are systematically investigated. The results show that the doping Ti forms Ti C nanocrystallites that are uniformly dispersed in the amorphous carbon matrix, whereas the doping Ce forms CeO_2 that exists with the amorphous phase in the co-doped(Ti,Ce)/a-C:H carbon-based film. The mechanical properties of this(Ti,Ce)/a-C:H film exhibit remarkable improvements, which could suggest higher hardness and elastic modulus as well as better adhesive strength compared to solitary Ti-doped Ti/a-C:H film. In particular, the as-prepared(Ti,Ce)/a-C:H film presents a relatively low friction coefficient and wear rate in both ambient air and deionized water,indicating that(Ti,Ce)/a-C:H film could feasibly improve the tribological performance of WC cemented carbide in a water environment.     

磁控溅射Al靶功率对类金刚石薄膜的结构和摩擦学性能影响

本文采用中频磁控溅射金属Al靶,以CH4为反应气体,通过调整Al靶溅射功率,在p(100)单晶硅片和不锈钢基底上成功制备出不同Al含量的Al/a-C:H纳米复合薄膜。并利用HR-TEM、XPS、纳米压痕仪和摩擦磨损试验机等手段分析和研究了Al/a-C:H薄膜的结构、机械及摩擦学性能。结果表明：金属Al以纳米晶颗粒形式镶嵌在非晶碳网络中,使得所制备Al/a-C:H薄膜呈现出典型的纳米晶/非晶复合结构;同时,Al掺杂促进薄膜中sp2杂化碳形成,且有效地释放残余内应力。Al靶溅射功率为800 W时所制备的Al/a-C:H薄膜具有结构致密、内应力低、硬度高的特性;在大气环境中,该薄膜与Si3N4陶瓷球干摩擦时显示出优越的摩擦学性能,其摩擦系数约为0.055,磨损率约为2.9×10-16 m3/(N?m)。