Changes in the Phase and the State of Diamond and Carbons determined under High Pressures, High Temperatures, and Rapid Quenfhing Conditions

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Diamond and various types of carbon materials were subjected to the shock compression whin induced the extreme conditions such as high pressures up to 100 GPa and high temperaures up to 10^4 K, and were recovered under the repid quenching condition in which the cooling reteof the materials was greater than 10^<10> K/s in the duration at the pressures. Although the attainable pressure had previously benn limited in the range of 15 to 55 GPa, the maximum pressure was extended up to 100 GPa by emplouing a high-stremgth steel and improving the design of recovery fixture through 2D numerical simulations.The phase transformation from various types of carbon to diamond was determined under equivalent conditions at temperatures less than 2000 K ; all the materials except for C_<60> fullerene, i.e., natural graphite crystal, synthesis isotropic graphite, pyrolytic graphite, carbon black, glassy carbon, and graphite sheet with a low density, did not transformed, whereas fullerene transformed into diamond completely.This implies that the activation energy of the transition is much different from the others, and that the reaction diagram significantly differs from the equilibrium phase diagram.C_<60> fulleren having a high purity and agood crysallinity transformed into transparent amorphous diamond which had the same properties as diamond but no long-range ordering in atomic arrangement. This is a new material and implies the evidence of high quenching rate.A high acceleration unit which was developed for a two-stage light-gas gun to exceed a velocity of 5Km/s was not applied because of the lekage of accelerating gas at the maximum velocity of 4.2 Km/s.