The University of Osaka · Physics and Astronomy
Professor Kento Katagiri's research lab specializes in high-pressure and dynamic materials science, focusing on the extreme-state behavior of advanced materials under shock compression and ultrahigh strain rates. The lab combines in situ femtosecond x-ray techniques, ab initio molecular dynamics, and diamond anvil cell experiments to investigate phase transitions, defect dynamics, and structural responses in materials such as diamond, tantalum, polyimide, and high-entropy alloys. A central theme is understanding the fundamental limits of material performance—such as dislocation velocities, tensile strength in liquids, and elastic limits—under conditions relevant to planetary interiors, inertial confinement fusion, and next-generation structural materials.
Figures are computed from collected data and may differ slightly.
The motion of line defects (dislocations) has been studied for more than 60 years, but the maximum speed at which they can move is unresolved. Recent models and atomistic simulations predict the existence of a limiting velocity of dislocation motion between the transonic and subsonic ranges at which the self-energy of dislocation diverges, though they do not deny the possibility of the transonic dislocations. We used femtosecond x-ray radiography to track ultrafast dislocation motion in shock-co
Hugoniot of full-dense nanopolycrystalline diamond (NPD) was investigated up to 1600 GPa. The Hugoniot elastic limit of NPD is 208 (±14) GPa, which is more than twice as high as that of single-crystal diamond. The Hugoniot of NPD is stiffer than that of single-crystal diamond up to 500 GPa, while no significant difference is observed at higher pressures where the elastic precursor is overdriven by a following plastic wave. These findings confirm that the grain boundary strengthening effect recog
In situ femtosecond x-ray diffraction measurements and ab initio molecular dynamics simulations were performed to study the liquid structure of tantalum shock released from several hundred gigapascals (GPa) on the nanosecond timescale. The results show that the internal negative pressure applied to the liquid tantalum reached -5.6 (0.8) GPa, suggesting the existence of a liquid-gas mixing state due to cavitation. This is the first direct evidence to prove the classical nucleation theory which pr
A series of shock wave experiments were conducted to measure the optical properties of single-crystal diamond $\ensuremath{\langle}100\ensuremath{\rangle}$ in the pressure regime between 60 and 550 GPa. The results show that the transparency limit of diamond at 532 nm is $\ensuremath{\sim}170\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. When the applied pressure in diamond is lower than its Hugoniot elastic limit (HEL), diamond remains transparent during both compression and release processes. At t
The Hugoniot equation-of-state, Gr\"uneisen parameter, and structure of laser-shocked polyimide were measured. The polyimide Hugoniots were measured in the pressure range 80--600 GPa and found to be consistent with the extrapolation of previously reported data below 60 GPa. The structural measurements of polyimide shock compressed to pressures of 28--163 GPa were performed using the in situ x-ray diffraction technique, and the results show that the melting pressure of polyimide along its Hugonio
The high-entropy alloy with composition AlCoCrFeNi2.1, additively manufactured with the laser powder-bed fusion technique, has a far-from-equilibrium BCC/FCC eutectic nanolamellar structure. We studied the high-pressure response of this alloy under both static compression and high-strain rate shock compression. The response to static compression using a diamond anvil cell was studied at pressures up to 302 GPa with synchrotron x-ray diffraction at the advanced photon source. The high-pressure FC
We propose a new remote diagnostic technique using microwave time-domain response and Radio-over-fiber (RoF) technology to efficiently diagnose underground Fiberglass-Reinforced Plastic Mortar (FRPM) pipelines in a non-destructive and non-excavation scheme. We focused on the “Radio-over-Pipewall (RoP)” characteristics, in which microwaves propagate along the FRPM pipe wall and converge inside the cylindrical dielectric wall (FRPM) as guided modes, when the FRPM is buried underground to compose t
The motion of line defects (dislocations) has been studied for over 60 years but the maximum speed at which they can move is unresolved. Recent models and atomistic simulations predict the existence of a limiting velocity of dislocation motions between the transonic and subsonic ranges at which the self-energy of dislocation diverges, though they do not deny the possibility of the transonic dislocations. We use femtosecond x-ray radiography to track ultrafast dislocation motion in shock-compress
Optimizing grain boundary characteristics in polycrystalline materials can improve their properties. Many processing methods have been developed for grain boundary manipulation, including the use of intense radiation in certain applications. In this work, we used X-ray free electron laser pulses to irradiate single-crystalline bismuth selenide (Bi2Se3) and observed grain boundary formation and subsequent grain rotation in response to the X-ray radiation. Our observations with simultaneous transm
In their comment (1), Hawreliak et al. claims that our observation of stacking fault formation and transonic dislocation propagation in diamond (2) is not valid as they interpret the observed features as cracks. In this response letter, we describe our rationale for interpreting the observed features as stacking faults. We also address other points raised in their comments, including the clarifications of how the results of Makarov et al. (3) are not in conflict with our study.
We have proposed and developed the nondestructive inspection technique for underground fiberglass-reinforced plastic mortar (FRPM) pipelines utilizing microwave guided-modes propagation along a pipe-wall.This technique is attractive for remote sensing by combining with radio-over-fiber (RoF) technology.In this paper, the measurement results for an underground FRPM pipe combined with a RoF link are presented.
High entropy alloys (HEAs) are a new class of metals that exhibit unique mechanical performance. Among HEAs, additively manufactured eutectic high entropy alloys (AM EHEAs) have recently emerged as candidate materials for use in extreme conditions due to their simultaneous high strength and ductility. However, the deformation and structural evolution of AM EHEAs under conditions of high pressure have not been well characterized, limiting their use in extreme applications. Dynamic compression exp
Received 4 January 2023DOI:https://doi.org/10.1103/PhysRevB.107.019902©2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasRefractionShock wavesPhysical SystemsDiamondTechniquesPressure techniquesCondensed Matter, Materials & Applied Physics
Open papers in the app to read, cite, and organize with AI.
