RELIABLE HIGH PRESSURE TECHNIQUES AND SYNTHESIS OF DIAMOND

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1.Comparison of high pressure experimental techniques in China with those in JapanAnvils with double-beveled flank surfaces can confine a cubic pressurized space which is larger than that confined by single-beveled anvils, if the top faces of the both types are the same in size. On the basis of the confined cube size, the pressure generation efficiency of the double-beveled type was about 90% of that of the single-beveled type. However, the former has an improved mechanical stability against the "blow-out" accident. Knowledge to use the both efficiently was accumulated.2.New reactions to form diamond from carbides decomposed in metallic solvents(1) Detailed examination of conditions to form diamond from SiC revealed that too high a concentration of Si in the solvent works against further dissolution of SiC into the solvent. (2) Si can be dissolve into diamond as an impurity. (3) B4C can also be decomposed in a molten metallic solvent to crystallize diamond. And such diamond was characterized containing B at high concentration. (4) 3d, 4d and 5d metal carbides are much more difficult to be decomposed to give diamond. Systematic experiments were performed on 3d carbides from TiC to Fe3C.VC and Cr3C2 gave diamond and Fe3C gave a trace amount of diamond, while others did not.3. Analyzes of metal elements in diamond as impuritiesIncorporation of Si, Ni, Co and Mn was already revealed. In the present study, x-ray fluorescence method using synchrotron radiation as the excitation source revealed Fe to be incorporated at a concentration around 1 ppm and Cr, at a much lower level. Concentration of Zr in diamond was first dectermined by the LAM-ICP mass spectroscopy as to be about 0.1ppm.4.An international award given by Chines governmentFriendship Award in 1996, which is the highest honor for a foreigner, was given to the head researcher based on the exchange activities supported and promoted much by the present subject.