Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

DOI： 10.1038/s41598-022-2

Publishing type：Research paper (scientific journal)  

Abstract

Laser-induced periodic surface structure (LIPSS), which has a period smaller than the laser wavelength, is expected to become a potential technique for fine surface processing. We report the microscopic and macroscopic observations of the crystallinity of LIPSSs, where the characteristics such as defects generation and residual strain were analyzed, respectively. The LIPSSs were formed on a Si substrate using two different femtosecond pulses from Ti:Sapphire laser with near-infrared wavelength (0.8 μm) and free-electron laser (FEL) with mid-infrared wavelength (11.4 μm). The photon energies of the former and latter lasers used here are higher and lower than the Si bandgap energies, respectively. These LIPSSs exhibit different crystalline states, where LIPSS induced by Ti:Sapphire laser show residual strain while having a stable crystallinity; in contrast, FEL-LIPSS generates defects without residual strain. This multiple analysis (microscopic and macroscopic observations) provides such previously-unknown structural characteristics with high spatial resolution. To obtain LIPSS with suitable properties and characteristics based on each application it is paramount to identify the laser sources that can achieve such properties. Therefore, identifying the structural information of the LIPSS generated by each specific laser is of great importance.

DOI： 10.1038/s41598-022-25365-1

Other URL： https://www.nature.com/articles/s41598-022-25365-1

Abstract

Silicon polymorphs with exotic electronic and optical properties have recently attracted significant attention due to the wide range of useful bandgap characteristics1,2,3,4. They are typically formed by high pressure techniques, which put limitations on the sample volumes and their crystal structure5,6,7,8,9,10. This constitutes a major obstacle to study these polymorphs and their incorporation into existing technology. Here, we report on a new approach to create unusual crystal structures deep into the bulk of a silicon wafer by MeV-electrons generated by laser irradiation at ultra-relativistic intensity above ~2x10^18 W/cm2. Strong repulsion between the electrons, their branching due to self-generated magnetic field and nonlinear relativistic effects11,12,13 enhance deposition of their energy deep into the target and form high energy density conditions leading to ionisation, followed by fast quenching and restructuring into new crystal arrangements14,15,16,17,18. Analysis by Raman spectroscopy, synchrotron X-ray diffraction, and high-resolution transmission electron microscopy of nanocrystals formed in the irradiated samples provide compelling evidence of the formation of metastable Si phases. The unexplored domain of material transformations exposed to laser-produced MeV-electrons opens new pathways for the conversion into new crystal structures applicable to a wide range of materials at considerably larger quantity, all preserved for further studies and exploitation.

DOI： 10.21203/rs.3.rs-2060424/v1

Other URL： https://www.researchsquare.com/article/rs-2060424/v1.html

Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00269-022-01184-8

Other URL： https://link.springer.com/article/10.1007/s00269-022-01184-8/fulltext.html

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

<italic>ReciPro</italic> is a comprehensive multipurpose crystallographic program equipped with an intuitive graphical user interface (GUI), and it is completely free and open source. This software has a built-in crystal database consisting of over 20 000 crystal models, and the visualization system can seamlessly display a specified crystal model as an attractive three-dimensional graphic. The comprehensive features are not confined to these crystal model databases and viewers. It can smoothly and quantitatively simulate not only single-crystal and/or polycrystalline (powder) diffraction patterns of X-ray, electron and neutron diffraction of a selected crystal model, based on the kinematic scattering theory, but also various electron diffraction patterns and high-resolution transmission electron microscopy (TEM) images, based on the dynamical scattering theory. The features of stereographic projection of crystal planes/axes to explore crystal orientation relationships and the semi-automatic diffraction spot indexing function for experimental diffraction patterns assist diffraction experiments and analyses. These features are linked through a user-friendly GUI, and the results can be synchronously displayed almost in real time. <italic>ReciPro</italic> will assist a wide range of crystallographers (including beginners) using X-ray, electron and neutron diffraction crystallography and TEM.

DOI： 10.1107/s1600576722000139

Publishing type：Research paper (scientific journal)  

The Hugoniot equation-of-state, Grüneisen 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 Hugoniot is below 32(±3) GPa, indicating that the discontinuous volume change of the polyimide Hugoniot at ∼26 GPa observed in previous gas-gun experiments denotes the onset of melting. The consistency of the melting pressure between the previous gas-gun results and the present laser experiments suggests that the shock-melting process of polyimide is independent of the duration of the compression, revealing its rapid melting kinetics.

DOI： 10.1103/physrevb.105.054103

Other URL： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.105.054103/fulltext

Publishing type：Research paper (scientific journal)  

Skeletons of contemporary reef-building scleractinian corals are formed of aragonite, a polymorph of the calcium carbonate (CaCO3), notwithstanding calcite being a more stable phase under the condition of coral habitats. Circumstances developing aragonite in coral calcification have been addressed currently. Considering that the symbiotic relationship between the coral host and dinoflagellate algae (zooxanthellae) is perhaps relevant to coral calcification, we studied the impact of these symbiotic relationships on CaCO3 polymorph selection. Juvenile scleractinian corals (Acropora tenuis and Acropora digitifera) absent symbionts were cultured in seawaters with varied Mg/Ca molar ratios (mMg/Ca), and the mineral phases of the skeletons were detected employing X-ray diffraction. The findings revealed that diminutive quantities of calcite precipitated as coral skeleton in Acropora digitifera surprisingly in pseudo-present seawater (mMg/Ca similar to 5). Additionally, coral developed skeletons from only calcite in seawater with an mMg/Ca < 1. The evidence gathered in this investigation suggests that the symbiotic relationship affects the establishment of aragonite skeletons in the course of coral calcification.

DOI： 10.1029/2021jg006574

Other URL： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2021JG006574

Publishing type：Research paper (scientific journal)  

<title>Abstract</title>Meteorites from interplanetary space often include high-pressure polymorphs of their constituent minerals, which provide records of past hypervelocity collisions. These collisions were expected to occur between kilometre-sized asteroids, generating transient high-pressure states lasting for several seconds to facilitate mineral transformations across the relevant phase boundaries. However, their mechanisms in such a short timescale were never experimentally evaluated and remained speculative. Here, we show a nanosecond transformation mechanism yielding ringwoodite, which is the most typical high-pressure mineral in meteorites. An olivine crystal was shock-compressed by a focused high-power laser pulse, and the transformation was time-resolved by femtosecond diffractometry using an X-ray free electron laser. Our results show the formation of ringwoodite through a faster, diffusionless process, suggesting that ringwoodite can form from collisions between much smaller bodies, such as metre to submetre-sized asteroids, at common relative velocities. Even nominally unshocked meteorites could therefore contain signatures of high-pressure states from past collisions.

DOI： 10.1038/s41467-021-24633-4

PubMed

Other URL： http://www.nature.com/articles/s41467-021-24633-4

Publishing type：Research paper (scientific journal)  

We report the in-situ oxygen isotopic distributions corresponding to the petrographic-mineralogical observation on a compact Type A (CTA) Ca-Al-rich inclusion (CAI), KU-N-02, from a reduced CV3 chondrite, Northwest Africa 7865. The CTA has an igneous texture and mainly consists of spinel, melilite, and Al-Ti-rich clinopyroxene (fassaite). Oxygen isotopic compositions of the constituent minerals plot along the carbonaceous chondrite anhydrous mineral line. The spinel grains are poikilitically enclosed in the melilite and fassaite and are uniformly 16O-rich (Δ17O = approximately − 23‰). The fassaite is texturally classified into two types: blocky fassaite and intergranular fassaite. The blocky fassaite crystals exhibit growth zoning as they change from Ti-rich to Ti-poor along the inferred directions of crystal growth from core to rim, while the oxygen isotopic compositions change from 16O-poor (Δ17O = approximately − 6‰) to 16O-rich (Δ17O = approximately − 23‰) with crystal growth. The intergranular fassaite crystals exist between the melilite crystals and exhibit variable Ti abundance and oxygen isotopic compositions. Additionally, their relationships between Ti contents and oxygen isotopic composition are similar to those of the blocky fassaite. The melilite grains are homogeneously 16O-poor (Δ17O = approximately − 2‰), irrespective of their åkermanite (Åk) content. Each melilite grain generally exhibits growth zoning with increasing Åk contents from core to rim, although the melilite contains Åk-rich patches within single crystal. Åk-rich patches often include two types of fassaite: small blebby crystals attached to spinel crystals and round crystals. The oxygen isotopic compositions of the Åk-rich patch and blebby fassaite are 16O-poor (Δ17O = approximately − 2‰), similar to that of the host melilite. On the other hand, the round fassaite exhibits significant variation in oxygen isotopic compositions ranging from Δ17O = −23‰ to − 4‰, which are different from those of the host melilite. These petrographic textures and oxygen isotopic variations indicate the presence of a solid precursor with variable oxygen isotopic compositions for the CTA. The spinel and round fassaite grains are relicts of the precursor that melted in the 16O-poor nebular gas, resulting in the crystallization of the host melilite from the 16O-poor melt. The Åk-rich patches and blebby fassaite crystallized from melts trapped by the growing host melilite crystals. The blocky and intergranular fassaite crystallized after the melilite did, and the oxygen isotopic composition of the melt changed to 16O-rich during the crystallization process, suggesting that the oxygen isotopic composition of the surrounding nebular gas could be varied. The inferred oxygen isotopic evolution for CTA is consistent with those inferred for Type B CAIs, suggesting that coarse-grained igneous CAIs formed in a similar nebular environment regardless of precursor chemistry.

DOI： 10.1016/j.gca.2021.03.030

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.palaeo.2021.110329

Publishing type：Research paper (scientific journal)  

DOI： 10.1103/physrevlett.126.175503

PubMed

Other URL： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.126.175503/fulltext

Publishing type：Research paper (international conference proceedings)  

DOI： 10.1063/12.0000930

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.earscirev.2020.103385

Publishing type：Research paper (scientific journal)  

<title>Abstract</title>
Talc is widely distributed over the Earth's surface and is predicted to be formed in various tectonic settings. Talc is a very soft and anisotropic sheet silicate showing very low friction behavior. Therefore, the formation of talc is expected to weaken the strength of talc-bearing rocks and may be associated with the initiation of subduction, and with a decrease in the coupling coefficient resulting in aseismic movements along faults and shear zones within subduction zones. For these reasons, understanding the crystallographic preferred orientation (CPO) of talc is important to quantify the anisotropy and physical properties of the host rock. However, it is difficult to measure a significant number of talc crystal orientations and to evaluate the accuracy of the measurements using electron-backscattered diffraction (EBSD). Therefore, talc CPO has not been reported, and there is uncertainty regarding the estimation of the strength of deformed talc-bearing rocks. Using methods developed for antigorite, we report the first successful EBSD measurements of talc CPO from a talc schist formed due to Simetasomatism of ultramafic rocks by subduction zone fluids. We used a combination of W-SEM and FE-SEM measurements to examine domains of various grain sizes of talc. In addition, we used TEM measurements to evaluate the accuracy of the EBSD measurements and discuss the results of talc CPO analysis. Talc CPO in the present study shows a strong concentration of the pole to the (001) plane normal to the foliation. The strongest concentration of the [100] direction is parallel to the lineation. The talc schist produces similar S-wave splitting and P- and S-wave anisotropy as antigorite schist in deeper domains, thus identifying talc-rich layers in subduction zones may require a combination of geophysical surveys, seismic observations, and anisotropy modeling. The presence of strong talc CPO in rocks comprising the slab–mantle interface boundary may promote spatial expansion of the slip area during earthquakes along the base of the mantle wedge.

DOI： 10.2138/am-2020-7006

Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

© 2019 Elsevier Ltd Highly porous small bodies are thought to have been ubiquitous in the early solar system. Therefore, it is essential to understand the collision process of highly porous objects when considering the collisional evolution of primitive small bodies in the solar system. To date, impact disruption experiments have been conducted using high-porosity targets made of ice, pumice, gypsum, and glass, and numerical simulations of impact fracture of porous bodies have also been conducted. However, a variety of internal structures of high-porosity bodies are possible. Therefore, laboratory experiments and numerical simulations in the wide parameter space are necessary. In this study, high-porosity targets of sintered hollow glass beads and targets made by mixing perlite with hollow beads were used in a collision disruption experiment to investigate the effects of the mixture on collisional destruction of high-porosity bodies. Among the targets prepared under the same sintering conditions, it was found that the targets with more impurities tend to have lower compressive strength and lower resistance against impact disruption. Further, destruction of the mixture targets required more impact energy density than would have been expected from compressive strength. It is likely that the perlite grains in the target matrix inhibit crack growth through the glass framework. The mass fraction of the largest fragment collapsed to a single function of a scaling parameter of energy density in the strength regime (Πs) when assuming ratios of tensile strength to compressive strength based on a relationship obtained for ice-silicate mixtures. However, the dependence on Πs is much larger than that shown for porous targets with different internal microstructures from the targets in this study. The depth of the deep cavity specific to the high-porosity target was well represented by a dimensionless parameter using the compressive strength of both the pure glass and mixture targets. The empirical relationship of cavity depth was shown to hold for various targets used in previous studies irrespective of the internal microstructure of the targets.

DOI： 10.1016/j.pss.2019.104819

Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

© 2020 American Physical Society. We explore the electrical and magnetic properties of a fractal assembly of Josephson junctions with transparent interfaces. For this purpose, we employ an Mg/MgO/MgB2 nanocomposite with ∼16 vol. % of MgB2 nanograins, which are distributed in a fractal manner in the normal matrix. Irrespective of the low volume fraction of MgB2 nanograins, the nanocomposite behaves as a bulk-like superconductor, i.e., zero resistivity, perfect diamagnetism, and strong vortex pinning. Thus, a global Josephson phase coherence is achieved in the nanocomposite. The lower (Hc1J) and higher (Hc2J) critical fields of the Josephson network are exceptionally high (Hc1J=96Oe and Hc2J=83.5kOe) as compared to those reported previously for granular superconductors. This will give an example of robust macroscopic superconducting coherence derived from long-range proximity coupling among fractally distributed superconducting nanograins through quantum interference of Andreev quasiparticles. Transverse-field muon spin rotation measurements reveal that the mean internal field in the superconducting mixed state increases with decreasing temperature below which the Josephson phase coherence sets in, opposite to the diamagnetic response observed in magnetization measurements. This unusual behavior implies a highly disordered and fluctuating nature of the Josephson vortices in the present superconducting nanocomposite.

DOI： 10.1103/PhysRevB.101.035146

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.palaeo.2019.109335

Publishing type：Research paper (scientific journal)  

DOI： 10.1002/jqs.3101

Other URL： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/jqs.3101

We directly observed laser shock-induced, anomalous elastic compression of highly oriented pyrolytic
graphite (HOPG) and subsequent phase transition to lonsdaleite at a longitudinal stress of ~30 GPa using
an X-ray Free Electron Laser (XFEL). The observed phase transition is diffusionless and most likely
relaxes a strong shear stress in the highly elastically compressed lattice. Our experimental results show
that this diffusionless transformation depends on the mosaic spread of Highly Oriented Pyrlolytic
Graphite (HOPG) samples.

DOI： 10.2184/lsj.47.1_47

CiNii Article

Other URL： http://id.ndl.go.jp/bib/029483027

Presentation type：Oral presentation (general)  

Presentation type：Poster presentation  

Presentation type：Oral presentation (general)  

Presentation type：Poster presentation  

Presentation type：Oral presentation (general)  

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Presentation type：Poster presentation  

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Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Poster presentation  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Poster presentation  

Presentation type：Poster presentation  

Venue：Hokkaido University  

Presentation type：Oral presentation (general)  

Venue：Singapore  

Presentation type：Poster presentation  

Venue：Hokkaido University  

Presentation type：Poster presentation  

Venue：Nagoya  

Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba  

Presentation type：Oral presentation (general)  

Venue：千葉  

Presentation type：Poster presentation  

Venue：Makuhari Messe, Chiba  

Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba  

Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba  

Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba  

Presentation type：Oral presentation (general)  

Venue：高知大学  

Presentation type：Oral presentation (general)  

Venue：宇宙科学研究所