Additive-free nano-polycrystalline diamond(nPCD)composite was sintered by using a mixture of microdiamond(MD)and onion-like carbon(OLC)as raw materials at 4～6 GPa/1 000～1 400 ℃/5～30 minutes holding time.The composition,morphology,microstructure,density and hardness of the nPCD composite were measured by XRD,FESEM,HRTEM,Archimedes principle and Vickers hardness tester.The effect of MD and high-pressure sintering parameters on the OLC transformation process and the com-position,microstructure,properties of nPCD composite were studied.The results showed that the MD was uniformly distributed in the nPCD composite.MD acted as nu-cleus to promote the conversion of OLC to diamond.The increase of sintering pressure enhanced the density and hardness of the nPCD composite.When the sintering pressure was raised from 4 GPa to 6 GPa,the density of nPCD composite was increased from 2.72 g/cm3 to 3.02 g/cm3,and the hardness was increased from 41.85 GPa to 56 GPa.The in-crease of sintering temperature and holding time made the density and hardness of the nPCD composite increase first and then decrease.Nanotwinned diamond with 10 nm size appeared in the nPCD region in the nPCD composite.The presence of nanotwinned dia-mond increased the hardness of nPCD composite.
关键词
纳米聚晶金刚石(nPCD)/洋葱状碳(OLD)/微米金刚石(MD)/高压高温/相变
Key words
polycrystalline diamond/onion-like carbon/microdiamond/high pressure and high temperature/phase transition
维普
万方数据