Novel Development of High-Pressure Synthetic Diamonds 'Ultra-hard Nano-polycrystalline Diamonds'

摘要

We have succeeded in synthesizing a single-phase (binderless) ultra-hard nano-polycrystalline diamond (NPD) by direct conversion sintering from graphite under ultra-high pressure and high temperature. The hardness of NPD is considerably high, far surpassing that of single-crystal diamonds even at high temperature. In addition, NPD shows outstanding strength, possessing no cleavage features and no anisotropy of mechanical properties. The NPD consists of very fine grains of several tens nanometers without containing any secondary phases and binder materials which greatly affect the mechanical properties and thermal stability. These characteristics of NPD suggest potential applications of this novel material to innovative cutting tools and wear resistance tools. This report reviews our systematic studies concerning NPD in terms of its synthesis mechanism, characteristics and applications.