Application of nano-polycrystalline diamond to high-pressure technique using multi anvil apparatus

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K18806
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Earth and planetary science and related fields
• Research Institution: Ehime University
• Principal Investigator: Kunimoto Takehiro 愛媛大学, 地球深部ダイナミクス研究センター, 特定研究員 (20543169)
• Project Period (FY): 2017-06-30 – 2020-03-31
• Keywords: ナノ多結晶ダイヤモンド / 高圧発生 / マルチアンビル装置

Outline of Final Research Achievements

The pressures available in Kawai-type multianvil apparatus (KMA), using tungsten carbide or sintered diamond, have been limited to about 30 GPa and 60 GPa, respectively. Recent efforts in introductions of new materials and improvements in cell assemblies significantly expanded these limits to 60 GPa for WC anvils and 120 GPa for SD anvils.
We have been trying to improve the cell for the 6-8-2 cell to generate the pressure equivalent to the Earth’s core-mantle boundary (CMB), for better understanding of this heterogeneous region.
Experiments were conducted using the KMA at SPring-8. Generated pressures were determined from the unit cell volumes of Au using adequate equation of state. We reached pressures of about 150 GPa in two independent runs, which are the highest pressure ever reported in KMA. The pressure achieved in these runs completely cover the entire D” region (approx. 125-135 GPa), and some attempts have also been made to produce high temperatures under such pressures.

Free Research Field

地球内部科学

Academic Significance and Societal Importance of the Research Achievements

地球内部、特にマントル最下部条件(CMB)の物質科学的研究は主にダイヤモンドアンビル装置(DAC)を用いて行われてきた。しかしながらDACの場合、高温発生や温度測定において大きな誤差を含むため、研究内容によっては信頼性に乏しい場合もある。
本研究ではマルチアンビル装置を用いてCMBに相当する圧力発生を可能とした。そのため、これまでDACで実施された相境界の決定などの再現実験や実際のマントルに近い組成の試料を用いた実験を行うことで、これまで明らかにされてきた地球内部環境を再確認し、さらに新たな知見を加える事が期待できる。