人工合成的400目细颗粒金刚石与破碎料的热稳定性比较

Comparison of thermal stability of synthetic and milled diamonds with grain size of 400 mesh

本文在SPD6×1200型六面顶高温高压设备上成功合成出400目以细的具有完整晶型、表面平整的超细颗粒金刚石单晶。为了对人工合成的细颗粒金刚石单晶的特性进行比较研究,我们分别对人工合成的400目和100目的金刚石单晶,以及400目的金刚石破碎料进行了扫描电镜形貌分析、差热和热重分析以及磁化强度分析。扫描电镜形貌分析结果表明,人工合成的400目细颗粒金刚石与100目金刚石单晶一样具有完成的晶型并且表面平整,以六八面体晶型为主,而400目的破碎料却没有完整的晶型并且表面凹凸不平。差热和热重分析结果表明,人工合成的400目和100目的金刚石的热稳定性差别不大,而400目的破碎料的热稳定性较差。比磁化强度的测定结果表明,400目的破碎料金刚石的比磁化强度较低,说明其基本不含金属包裹体。以上研究结果表明,人工合成的细颗粒金刚石单晶比破碎料金刚石具有更好的热稳定性。破碎料金刚石较低的热稳定性可能是由于其不规则的晶体表面以及在破碎过程中形成的宏观缺陷造成的。人工直接合成的细颗粒金刚石在高端工具制造方面将逐步成为破碎料微粉的替代产品。

400 -mesh diamond with good shape and slick crystal face was successfully synthesized in SPD6 1200 cubic high - pressure apparatus. The 400 - mesh and 100 - mesh synthetic diamond were studied by scanning electron microscope （SEM）, TG -DTA thermal analyzer, and magnetization strength analyzer. The SEM results show that the 400 - mesh and 100 - mesh synthetic diamonds both have well hex - octahedron shape; however, the 400- mech milled diamond has irregular crystal shape and accidented crystal surface.The TG - DTA results show that the 400 - mesh and 100 - mesh synthetic diamonds both have higher thermal stability than the 400 - mesh milled diamond. The results of specific magnetization strength analyze show that the 400 - mesh milled diamond has much weaker specific magnetization strength than the 400 - mesh and 100 -mesh synthetic diamonds, which indicates that the milled diamond contains few metal inclusions. The irregular crystal shape, accidented crystal surface and macroscopic disfigurement caused in the milling process may induce lower thermal stability. Synthetic fine diamond crystals are expected to replace milled diamond micro powder in making advanced diamond tools.