Structural Dynamics of Polycrystals under Shock Compression Observed via Nanosecond Time-resolved X-ray Diffraction
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Structural Dynamics of Polycrystals under Shock Compression Observed via Nanosecond Time-resolved X-ray Diffraction Kazutaka G. Nakamura1, Jianbo Hu1, Kouhei Ichiyanagi2, Nobuaki Kawai3, Shin-ichi Adachi4 1 Materials and Structures Laboratory, Tokyo Institute of Technology, R3-10, 4259 Nagatsuta, Yokohama 226-8503, Japan 2 Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8562, Japan 3 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai 3-1-1, Sagamihara 252-5210, Japan 4 Photon Factory, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan ABSTRACT Dynamics of structural phase transition in polycrystalline samples (tetragonal stabilized zirconia and bismuth) under laser-shock compression has been studied using nanosecond timeresolved X-ray diffraction technique based on synchrotron radiation. Tetragonal zirconia shows the structural phase transition to the monoclinic phase within 20 ns during shock compression without any intermediate and reverts back to the tetragonal phase during pressure release. Bismuth shows more complex phase transition dynamics. The Bi-I phase, which is the stable phase at ambient pressure and temperature, transfers to Bi-V phase within 4 ns under shock compression and gradually reverts back following the path of Bi-V →Bi-III → Bi-II → Bi-I within 30 ns during pressure release. INTRODUCTION Investigation on phase transition of materials under shock compression has bottlenecked due to the limitation of traditional experimental approaches that provide incomplete information on structural dynamics. Direct measurement of transient structures such as X-ray diffraction and electron diffraction during the phase transition is required to understand details of the phase transition. In order to achieve this measurement, there are two problems. One is that the transition usually occurs very fast in the nanosecond time region and the time-resolved measurement is required. The other is that a sample is damaged or broken by the shock compression and the single-shot measurement is required. The combination of short-pulsed Xrays from synchrotron radiation and laser shock compression overcomes these problems, because the transient structure of materials can be determined by the single-shot X-ray diffraction with the nanosecond time resolution. Using this technique, Ichiyanagi et al. [1] demonstrated nanosecond time-resolved Laue diffraction of a CdS single crystal under laser shock compression and observed its transient lattice deformation. We applied this technique for polycrystalline materials and demonstrated direct observations of shock-induced phase transitions of polycrystalline zirconia ceramics and bismuth.
EXPERIMENT All experiments were performed using the beamline NW-14A [2] at the Photon Factory Advanced Ring (PF-AR) of High Energy Accelerator Research Organization, Japan. The X-ray pulse from an undulator with the period length of 20 mm has the pulse duration of approximately 100 ps a
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