Nanotechnologies / Materials
Material synthesis, Energy, Cutting edge sciences

High performance high-power lasers and high energy
density materials
Division of Electrical, Electronic and Infocommunications Engineering, Graduate School of Engineering
Associate Professor

Norimasa Ozaki

Researchmap https://researchmap.jp/read0191201

Abstract

Nanotechnologies / Materials

Our research is to study structures and properties of materials
in extreme conditions, such as ultrahigh pressures generated byhigh-power lasers. Understanding the changes in the structure andstate of matter and the resulting changes in physical properties
and chemical reactions is crucial for designing and synthesizing
new materials. We believe that we can contribute to the developments of advanced laser machining and processing by combining
real-time observation data with informatics technology. Our projectwill produce new knowledge through collaborative research usingstate-of-the-art facilities and equipment such as X-ray free electron
lasers and supercomputers.

▍ Background & Results
High-power laser-driven dynamic compression enables us to
study materials under ultrahigh pressures over 10 million atmospheres (three times the pressure of the Earth's core), which is
impossible to achieve with other techniques. In other words, thelaser technique is an excellent approach to discovering the hidden
structures and properties of matter. For example, carbon is oneof the most important materials with various polymorphs. It has aunique phase that can exist as a solid (diamond) even under ultra-high pressure and temperature. Nano-polycrystalline diamond,consisting of nano-sized diamond grains packed without gaps,
has believed to exhibit much higher strength than single-crystal
diamond. In our research project, the strength of nano-polycrystalline diamond was quantitatively determined for the first time using
the laser-driven ultrahigh pressure technique. Moreover, materials'
deformation and state change under such extreme conditions
can now be directly investigated using a highly bright, ultra-shortpulsed light source called an X-ray free electron laser. We can evenvisualize how high-strength diamond is deformed and loses its
strength by measuring the X-ray diffraction on such an X-ray freeelectron laser facility. In our research project, we plan to investigate
how such high strength and high hardness materials melt. As thefirst step, we have succeeded in directly investigating the structureof tantalum, which is one of the hardest elemental metals with avery high melting point. The "breaking" of the high-temperature tantalum liquid was revealed by comparing the experimental resultswith first-principles quantum mechanics calculations.

ergy density science, is progressing, and further developments areexpected.

Fig. 1

Fig. 2▍ Significance of the research and Future perspective
The discovery of new materials and new structures in extreme
conditions extends the possibility of materials. Many questions
exist in fast structural transitions, state changes like melting andmetallization, and chemical reaction kinetics under extreme pressures and temperatures. The understanding of structural changes
in terrestrial and planetary materials can lead to the elucidation of
the internal structure and formation process of planets. A cross-disciplinary science in which Japan has an advantage, called high-en-

P a t e n t Japanese Unexamined Patent Publication No.2020-098330, WO2019098330
Katagiri, Kento; Ozaki, Norimasa; Umeda, Yuhei et al. Shock Response of Full Density Nanopolycrystalline Diamond. Physical Review Letters. 2020;125:185701. doi: 10.1103/PhysRevLett.125.185701
Tr e a t i s e
Katagiri, Kento; Ozaki, Norimasa; Ohmura, Satoshi et al. Liquid Structure of Tantalum under Internal Negative Pressure. Physical Review Letters. 2021;
126:175503. doi: 10.1103/PhysRevLett.126.175503
https://resou.osaka-u.ac.jp/ja/research/2020/20201028_1
https://resou.osaka-u.ac.jp/ja/research/2021/20210521_2
URL
https://www.asahi.com/articles/ASN767L0BN6TPLBJ004.html?iref=pc_photo_gallery_bottom
https://www.ile.osaka-u.ac.jp/ja/blog/2019/08/21/post-4073/index.html
K e y w o r d high-power laser, new material, extreme conditions, X-ray free electron laser, laser machining