Using a turbostratic pyrolytic boron nitride as a starting material, we synthesized a variety of ultrahard polycrystalline cubic boron nitride (PcBN) as a function of the heating duration changing from 1 to 60 min under a constant temperature and pressure conditions (1950 °C and 25 GPa) using a multi-anvil apparatus. When the heating duration was less than 13 min, ultrafine nano-polycrystalline cBN (U-NPcBN) with the mean grain size of <50 nm was produced. Among these U-NPcBNs those synthesized with 11–13 min were found to have a uniform texture composed purely of cBN (i.e. with no wurzite BN residue) and a Knoop hardness of >53 GPa, which is 20% higher than that of the hardest conventional binderless PcBN in practical use. Furthermore, the PcBNs synthesized with 18–20 min showed a unique nanocrystalline texture composed of relatively coarse grains dispersed in a fine grained matrix and even higher Knoop hardness (54.5–55.2 GPa).

使用涡轮层热解氮化硼作为起始材料，我们合成了多种超硬多晶立方氮化硼（PcBN），作为在恒定温度和压力条件下（1950°C和25的加热时间从1到60分钟变化的函数） GPa）使用多砧装置。当加热时间少于13分钟时，产生平均晶粒尺寸＜50nm的超细纳米多晶cBN（U-NPcBN）。在这些U-NPcBN中，经11-13分钟合成的U-NPcBN具有均匀的质地，仅由cBN组成（即没有纤锌矿BN残留物），努氏硬度大于53 GPa，比最坚硬的努氏硬度高20％。实际使用中的传统无粘结剂PcBN。此外，