压力环境对纳米晶金刚石石墨化的影响

Effect of Pressure Environment on Graphitization of Nano-Crystalline Diamond

高压下纳米金刚石石墨化对多晶金刚石烧结体的性能具有非常重要的影响。为此,在5~9 GPa、600~1500℃的压力温度范围,分别对平均晶粒尺寸为50 nm的纯纳米金刚石粉末和NaCl-纳米金刚石混合粉末的石墨化温度进行了研究。结合粉末X射线衍射的物相定量分析方法,分析了非静水压(纯金刚石粉末)和准静水压(NaCl-纳米金刚石混合粉末)下纳米金刚石在不同压力和温度下的石墨化程度。结果表明:5 GPa时,纯纳米金刚石粉末石墨化的起始温度在800℃以上,9 GPa时则在1000~1300℃之间;在约7 GPa的压力下,较短的保温时间内纳米金刚石的石墨化温度由非静水压环境中的1000℃提高到准静水压环境中的1500℃以上。

The graphitization process of nano-crystalline diamond(NCD)under high pressure significantly influences the performance of sintered polycrystalline diamond bulks.Here,we investigated the graphitization temperature of both pure nano-diamond,with an average grain size of 50 nm,and a mixture of NaCl and nano-diamond powder in a pressure and temperature range of 5−9 GPa and 600−1500℃,respectively.With a quantitative analysis method employing powder X-ray diffraction,we analyzed the graphitization degree of NCD under different pressures and temperatures,examining both non-hydrostatic pressure conditions(pure NCD powder)and quasi-hydrostatic pressure conditions(NaCl-NCD mixed powder).Our findings indicate that the initial graphitization temperature of pure NCD powder exceeds 800℃ at 5 GPa,and ranges between 1000 and 1300℃ at 9 GPa.Notably,under quasi-hydrostatic pressure conditions at about 7 GPa,the graphitization temperature of NCD increases from 1000℃ in non-hydrostatic pressure conditions to 1500℃ or higher within a short holding time.