A research team composed of Ph.D student Kento Katairi and Associate Professor Masayoshi Ozaki of the Graduate School of Engineering, Osaka University, Japan, and Professor Toruo Iriya from the Research Center for Deep Earth Dynamics of Ehime University, and others, have clarified the strength of nano-polycrystalline diamond during high-speed deformation.

The research team sintered crystallites with a maximum size of tens of nanometers to form a diamond in a “nanopolycrystalline” state, and then applied ultra-high pressure to it to investigate its strength. The experiment was carried out using the laser XII laser with the largest pulse output power in Japan. Observation found that when the maximum pressure of 16 million atmospheres (more than 4 times the pressure of the center of the earth) is applied, the volume of the diamond is reduced to less than half of its original size.

The experimental data obtained this time show that the strength of nano-polycrystalline diamond (NPD) is more than twice that of ordinary single crystal diamond. It was also found that NPD has the highest strength among all materials investigated so far.