日時 ： ２００７年１月１２日（金）17：00〜
場所 ： 愛媛大学理学部講義棟 １０１教室
要 旨
The maximum pressure achieved by Kawai-type multi-anvil apparatus (KMA) has been limited to ~30 GPa using tungsten carbide (WC) as the second-stage anvil material, which was recently extended to ~60 GPa by using Sintered diamond (SD) anvils. We developed a 6-8-2 system based on a combination of the concepts of KMA and diamond anvil cell (DAC). A pair of diamond rods were used for the pressure intensifiers, which were placed in the pressure medium of KMA. We used single crystal diamond (SCD: Ib), SD with cobalt binder, and ultra-hard nano-polycrystalline diamond (NPD or HIME-DIA) developed in our laboratory, as the third-stage anvils. In situ X-ray diffraction experiments were conducted at SPring-8, using the 6-8-2 system in KMA (SPEED-1500 and SPEED-Mk.II). The generated pressures were calculated from the unit cell volume of gold on the basis of the equation of state proposed by Anderson et al. (1989). By using the 6-8-2 system that we developed, the pressure generation of over 90 GPa has been achieved with the press load of ~700 ton at room temperature. In the heating experiments under pressure, the pressure substantially dropped with increasing temperature above 800 K, when SCD and SD were used as third-stage anvils, and ultimately decreased down to ~25 GPa at 1400 K. Inspection of the recovered third-stage anvils revealed that the pressure drop was presumably due to significant plastic deformation of the cullet surface of diamonds. In contrast, we were successful to maintain the generated pressures of 80-90 GPa at temperature up to about 1250 K using anvils with NPD. The pressure then decreased significantly at further higher temperature, but was obviously higher (~55GPa, at 1400 K) than those observed by using SCD and SD anvils. The plastic deformation of the cullet surface of the NPD anvils was actually substantially smaller than observed in other anvils.
問い合わせ先：土屋 卓久 TEL （089）927-8198
E-mail takut@sci.ehime-u.ac.jp
