Explorative Trials towards Original Techniques of Diamond High Pressure Synthesis in Toshiba Group

<p>The reliable method of synthesizing diamond at HPHT condition was first disclosed by GE, through Nature in 1955, with no information about the apparatus used nor actual method of conversion from graphite to diamond. No disclosure was kept continued till 1959, when patents and scientific journal papers describing the actual method were published at the same time. </p><p>We had to start the trial of developing a process for industrial production of diamond, under a difficult situation that the newly disclosed technical factors were completely covered with GE’s exclusive patent rights. On the other hand, some Japanese industries in that time had strong intention of challenge to realize new and their original attainment in technology and science, in the background of their regrowth from the depression after the war. </p><p>Thus, we could have opportunity of making rather basic or explorative search for new and original methods different from those of GE, and fortunately as a researcher, we could find a series of composite systems certainly catalyzing the diamond formation from graphite. Two types of cubic apparatuses were also newly designed with concept of excellent mechanical accuracy in repeated use together with easiness of operation. Some evaluation experiments finally resulted in the formation of large transparent and colorless particles of diamond (>0.5mm) without sensitive P-T control, in a wide range of P-T condition. Need of pressure of several kilobars higher than that with the process using the Ni-based alloy, was the remaining subject. Some condition could produce polycrystalline particles with nearly cubic shape and lightly greyish color, around 2mm in size, like naturally produced polycrystalline particles. </p><p>The author would like to show our experience for explaining the technical situation and the background of the age when we started, though the development activity itself might be improper in the current situation where risk of investment and early gain are severely considered.</p>