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論文

Phase transformation and equation of state in Ti-45Al alloy under high pressure

Li, X.*; Zhu, R.*; Xin, J.*; Luo, M.*; Shang, S.-L.*; Liu, Z.-K.*; Yin, C.*; 舟越 賢一*; Dippenaar, R. J.*; 肥後 祐司*; et al.

CALPHAD; Computer Coupling of Phase Diagrams and Thermochemistry, 84, p.102641_1 - 102641_6, 2024/03

https://doi.org/10.1016/j.calphad.2023.102641
 被引用回数：0 パーセンタイル：0.00(Thermodynamics)

The phase transformations and pressure-volume dependencies of the Ti-45Al alloy with respect to pressure have been investigated by means of in-situ observation using multi anvil-type high-pressure devices and synchrotron radiation. Under hydrostatic compression from 0 to 10.1 GPa, about 2.3 vol. % of $$gamma$$ transforms continuously to $$alpha$$2. Lattice parameters as well as volume fractions of these two phases have been determined as a function of pressure. Bulk moduli estimated using Birch-Murnaghan's equation of state are 148 GPa for the $$gamma$$ phase, 138 GPa for the $$alpha$$2 phase, and 149 GPa for their two-phase mixture of Ti-45Al alloy. First-principles have also applied to investigate bulk moduli of two single phases, and the deviation between calculations and measurements is discussed and attributed to mainly phase transformation. The presently study provides useful insights into thermodynamics of $$alpha$$2 and $$gamma$$ phases under high pressure.

論文

Strongly coupled spin waves and surface acoustic waves at room temperature

Hwang, Y.*; Puebla, J.*; 近藤 浩太*; Gonzalez-Ballestero, C.*; 一色 弘成*; S$'a$nchez Mu$~n$oz, C.*; Liao, L.*; Chen, F.*; Luo, W.*; 前川 禎通*; et al.

Physical Review Letters, 132(5), p.056704_1 - 056704_7, 2024/01

https://doi.org/10.1103/PhysRevLett.132.056704
 被引用回数：17 パーセンタイル：97.80(Physics, Multidisciplinary)

Here, we report the observation of strong coupling between magnons and surface acoustic wave (SAW) phonons in a thin CoFeB film constructed in an on-chip SAW resonator by analyzing SAW phonon dispersion anticrossings. We employ a nanostructured SAW resonator design that, in contrast to conventional SAW resonators, allows us to enhance shear-horizontal strain. Crucially, this type of strain couples strongly to magnons. Our device design provides the tunability of the film thickness with a fixed phonon wavelength, which is a departure from the conventional approach in strong magnon-phonon coupling research. We detect a monotonic increase in the coupling strength by expanding the film thickness, which agrees with our theoretical model. Our work offers a significant way to advance fundamental research and the development of devices based on magnon-phonon hybrid quasiparticles.

論文

Spin fluctuations in the 112-type iron-based superconductor Ca$$_{0.82}$$La$$_{0.18}$$Fe$$_{0.96}$$Ni$$_{0.04}$$As$$_{2}$$

Xie, T.*; Liu, C.*; 梶本 亮一; 池内 和彦*; Li, S.*; Luo, H.*

Journal of Physics; Condensed Matter, 34(47), p.474001_1 - 474001_8, 2022/11

https://doi.org/10.1088/1361-648X/ac9441
 被引用回数：0 パーセンタイル：0.00(Physics, Condensed Matter)

We report time-of-flight inelastic neutron scattering (INS) investigations on the spin fluctuation spectrum in the 112-type iron-based superconductor (FeSC) Ca$$_{0.82}$$La$$_{0.18}$$Fe$$_{0.96}$$Ni$$_{0.04}$$As$$_{2}$$ (CaLa-112). In comparison to the 122-type FeSCs with a centrosymmetric tetragonal lattice structure (space group $$I4/mmm$$) at room temperature and an in-plane stripe-type antiferromagnetic (AF) order at low temperature, the 112 system has a noncentrosymmetric structure (space group $$P2_1$$) with additional zigzag arsenic chains between Ca/La layers and a magnetic ground state with similar wavevector $$mathbf{Q}_mathrm{AF}$$ but different orientations of ordered moments in the parent compounds. Our INS study clearly reveals that the in-plane dispersions and the bandwidth of spin excitations in the superconducting CaLa-112 closely resemble to those in 122 systems. While the total fluctuating moments $$langle m^2 rangle approx 4.6 pm 0.2$$ $$mu_B^2$$/Fe are larger than 122 system, the dynamic correlation lengths are similar ($$xi approx 10$$ ${AA}$). These results suggest that superconductivity in iron arsenides may have a common magnetic origin under similar magnetic exchange couplings with a dual nature from local moments and itinerant electrons, despite their different magnetic patterns and lattice symmetries.

論文

$$Q$$-dependent collective relaxation dynamics of glass-forming liquid Ca$$_{0.4}$$K$$_{0.6}$$(NO$$_{3}$$)$$_{1.4}$$ investigated by wide-angle neutron spin-echo

Luo, P.*; Zhai, Y.*; Falus, P.*; Garc$'i$a Sakai, V.*; Hartl, M.*; 古府 麻衣子; 中島 健次; Faraone, A.*; Z, Y.*

Nature Communications (Internet), 13, p.2092_1 - 2092_9, 2022/04

https://doi.org/10.1038/s41467-022-29778-4
 被引用回数：12 パーセンタイル：73.09(Multidisciplinary Sciences)

The relaxation behavior of glass formers exhibits spatial heterogeneity and dramatically changes upon cooling towards the glass transition. However, the underlying mechanisms of the dynamics at different microscopic length scales are not fully understood. We measured the $$Q$$-dependent coherent intermediate scattering function of a prototypical ionic glass former Ca$$_{0.4}$$K$$_{0.6}$$(NO$$_{3}$$)$$_{1.4}$$, in the highly viscous liquid state. In contrast to the structure modulated dynamics for $$Q$$ $$<$$ 2.4 $AA$^{-1}$$, i.e., at and below the structure factor main peak, for $$Q$$ $$>$$ 2.4 $AA$^{-1}$$, beyond the first minimum above the structure factor main peak, the stretching exponent exhibits no temperature dependence and concomitantly the relaxation time shows smaller deviations from Arrhenius behavior. This finding indicates a change in the dominant relaxation mechanisms around a characteristic length of 2.6 AA, below which the relaxation process exhibits a temperature independent distribution and more Arrhenius-like behavior.

論文

Grain-size-dependent microstructure effects on cyclic deformation mechanisms in CoCrFeMnNi high-entropy-alloys

Luo, M.-Y.*; Lam, T.-N.*; Wang, P.-T.*; Tsou, N.-T.*; Chang, Y.-J.*; Feng, R.*; 川崎 卓郎; Harjo, S.; Liaw, P. K.*; Yeh, A.-C.*; et al.

Scripta Materialia, 210, p.114459_1 - 114459_7, 2022/03

https://doi.org/10.1016/j.scriptamat.2021.114459
 被引用回数：25 パーセンタイル：87.99(Nanoscience & Nanotechnology)

The effect of grain size on strain-controlled low-cycle fatigue (LCF) properties in the CoCrFeMnNi high-entropy alloys (HEAs) was investigated towards the distinct microstructural developments during cyclic loading at a strain amplitude of $$pm$$ 1.0%. A much more prominent secondary cyclic hardening (SCH) behavior at the final deformation stage was observed in the fine-grained (FG) than in the coarse-grained (CG) CoCrFeMnNi. In-situ neutron-diffraction and microscopic examination, strongly corroborated by molecular dynamic (MD) simulations, indicated that dislocation activities from planar slip to wavy slip-driven subgrain structures within the grains acted as the primary cyclic-deformation behaviors in the FG CoCrFeMnNi. Differently observed in the cyclic behavior of the CG CoCrFeMnNi was due to a transition from the planar dislocation slip to twinning.

論文

Tensile response of as-cast CoCrFeNi and CoCrFeMnNi high-entropy alloys

Lam, T.-N.*; Luo, M.-Y.*; 川崎 卓郎; Harjo, S.; Jain, J.*; Lee, S.-Y.*; Yeh, A.-C.*; Huang, E.-W.*

Crystals (Internet), 12(2), p.157_1 - 157_9, 2022/02

https://doi.org/10.3390/cryst12020157
 被引用回数：19 パーセンタイル：95.61(Crystallography)

In this research, we systematically investigated equiatomic CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs). Both of these HEA systems are single-phase, face-centered-cubic (FCC) structures. Specifically, we examined the tensile response in as-cast quaternary CoCrFeNi and quinary CoCrFeMnNi HEAs at room temperature. Compared to CoCrFeNi HEA, the elongation of CoCrFeMnNi HEA was 14% lower, but the yield strength and ultimate tensile strength were increased by 17% and 6%, respectively. The direct real-time evolution of structural defects during uniaxial straining was acquired via in situ neutron-diffraction measurements. The dominant microstructures underlying plastic deformation mechanisms at each deformation stage in as-cast CoCrFeNi and CoCrFeMnNi HEAs were revealed using the Convolutional Multiple Whole Profile (CMWP) software for peak-profile fitting. The possible mechanisms are reported.

論文

Relevance of hydrogen bonded associates to the transport properties and nanoscale dynamics of liquid and supercooled 2-propanol

Zhai, Y.*; Luo, P.*; 長尾 道弘*; 中島 健次; 菊地 龍弥*; 川北 至信; Kienzle, P. A.*; Z, Y.*; Faraone, A.*

Physical Chemistry Chemical Physics, 23(12), p.7220 - 7232, 2021/03

https://doi.org/10.1039/d0cp05481j
 被引用回数：5 パーセンタイル：30.29(Chemistry, Physical)

2-Propanol was investigated, in both the liquid and supercooled states, as a model system to study how hydrogen bonds affect the structural relaxation and the dynamics of mesoscale structures, of approximately several Angstroms, employing static and quasi-elastic neutron scattering and molecular dynamics simulation. Dynamic neutron scattering measurements were performed over an exchanged wave-vector range encompassing the pre-peak, indicative of the presence of H-bonding associates, and the main peak. The dynamics observed at the pre-peak is associated with the formation and disaggregation of the H-bonded associates and is measured to be at least one order of magnitude slower than the dynamics at the main peak, which is identified as the structural relaxation. The measurements indicate that the macroscopic shear viscosity has a similar temperature dependence as the dynamics of the H-bonded associates, which highlights the important role played by these structures, together with the structural relaxation, in defining the macroscopic rheological properties of the system. Importantly, the characteristic relaxation time at the pre-peak follows an Arrhenius temperature dependence whereas at the main peak it exhibits a non-Arrhenius behavior on approaching the supercooled state. The origin of this differing behavior is attributed to an increased structuring of the hydrophobic domains of 2-propanol accommodating a more and more encompassing H-bond network, and a consequent set in of dynamic cooperativity.

論文

Lattice Boltzmann modeling and simulation of forced-convection boiling on a cylinder

齋藤 慎平*; De Rosis, A.*; Fei, L.*; Luo, K. H.*; 海老原 健一; 金子 暁子*; 阿部 豊*

Physics of Fluids, 33(2), p.023307_1 - 023307_21, 2021/02

https://doi.org/10.1063/5.0032743
 被引用回数：48 パーセンタイル：97.96(Mechanics)

流れ場で沸騰が発生する現象は強制対流沸騰として知られている。今回、飽和条件の流れ場中の円柱上での沸騰システムを数値的に調査した。複雑な気液相変化現象に対処するために、擬ポテンシャル格子ボルツマン法(LBM)に基づく数値スキームを開発した。高いレイノルズ数の数値安定性を高めるため、衝突項を中心モーメント(CM)の空間で解いた。CMベースのLBMに適した力場スキームを採用することで簡潔でありながら堅牢なアルゴリズムとなっている。さらに、熱力学的一貫性を確保するために必要な追加項をCMの枠組みにおいて導出した。現在のスキームの有効性は、核形成,成長、および30-30000の間で変化するレイノルズ数の蒸気泡の離脱を含む一連の沸騰プロセスに対してテストされた。開発したCMベースのLBMは、初期気相などの人工的な入力なしに、核沸騰,遷移沸騰、および膜沸騰の沸騰様式を再現できる。結果からプール沸騰ではなく強制対流システムでも抜山曲線として知られる典型的な沸騰曲線が現れることが分かった。また、今回のシミュレーションは膜沸騰領域でも断続的な直接固液接触の実験的観察を支持することが分かった。

論文

Neutron spin-echo studies of the structural relaxation of network liquid ZnCl$$_2$$ at the structure factor primary peak and prepeak

Luo, P.*; Zhai, Y.*; Leao, J. B.*; 古府 麻衣子; 中島 健次; Faraone, A.*; Zhang, Y.*

Journal of Physical Chemistry Letters (Internet), 12(1), p.392 - 398, 2021/01

https://doi.org/10.1021/acs.jpclett.0c03146
 被引用回数：6 パーセンタイル：36.33(Chemistry, Physical)

典型的なネットワークイオン性液体ZnCl$$_2$$の第1およびプレ回折ピークでの微視的な構造緩和を中性子スピンエコー分光により調べた。第1構造ピークの緩和はプレピークのものより速く、活性化エネルギーは約33%高い。融点より十分高温においても、伸長指数関数で記述される緩和が観測された。驚くべきことに、とくに第1ピークにおいて、非指数関数性パラメータは冷却とともに急激に増加し、$$T_{rm m}$$に向かって緩和は伸長指数型から指数型へと変わる。これらの結果は、過冷却状態の典型的なガラス的ダイナミクスが平衡液体で現れること、2つの異なる空間スケールの運動の活性化エネルギーが冷却に伴うネットワーク構造の形成と関連していることを示唆する。

論文

Odd and even modes of neutron spin resonance in the bilayer iron-based superconductor CaKFe$$_{4}$$As$$_{4}$$

Xie, T.*; Wei, Y.*; Gong, D.*; Fennell, T.*; Stuhr, U.*; 梶本 亮一; 池内 和彦*; Li, S.*; Hu, J.*; Luo, H.*

Physical Review Letters, 120(26), p.267003_1 - 267003_7, 2018/06

https://doi.org/10.1103/PhysRevLett.120.267003
 被引用回数：40 パーセンタイル：86.24(Physics, Multidisciplinary)

We report an inelastic neutron scattering study on the spin resonance in the bilayer iron-based superconductor CaKFe$$_4$$As$$_4$$. In contrast to its quasi-two-dimensional electron structure, three strongly $$L$$-dependent modes of spin resonance are found below $$T_c$$ = 35 K. The mode energies are below and linearly scale with the total superconducting gaps summed on the nesting hole and electron pockets, essentially in agreement with the results in cuprate and heavy fermion superconductors. This observation supports the sign-reversed Cooper-pairing mechanism under multiple pairing channels and resolves the long-standing puzzles concerning the broadening and dispersive spin resonance peak in iron pnictides. More importantly, the triple resonant modes can be classified into odd and even symmetries with respect to the distance of Fe-Fe planes within the Fe-As bilayer unit. Thus, our results closely resemble those in the bilayer cuprates with nondegenerate spin excitations, suggesting that these two high-$$T_c$$ superconducting families share a common nature.

論文

Spin excitations in optimally P-doped BaFe$$_2$$(As$$_{0.7}$$P$$_{0.3}$$)$$_2$$ superconductor

Hu, D.*; Yin, Z.*; Zhang, W.*; Ewings, R. A.*; 池内 和彦*; 中村 充孝; Roessli, B.*; Wei, Y.*; Zhao, L.*; Chen, G.*; et al.

Physical Review B, 94(9), p.094504_1 - 094504_7, 2016/09

AA2016-0252.pdf:2.18MB

https://doi.org/10.1103/PhysRevB.94.094504
 被引用回数：20 パーセンタイル：62.63(Materials Science, Multidisciplinary)

最適Pドープされた超伝導体BaFe$$_2$$(As$$_{0.7}$$P$$_{0.3}$$)$$_2$$ (T$$_c$$=30K)におけるスピン励起の温度及びエネルギー依存性が非弾性中性子散乱実験を使って調べられた。我々の実験結果は密度汎関数理論や動的平均場理論で予想される計算結果と矛盾しておらず、BaFe$$_2$$(As$$_{0.7}$$P$$_{0.3}$$)$$_2$$における平均プニクトゲン高さの減少が、電子相関の強さを弱め、磁気励起の有効バンド幅の増加に寄与することを示唆している。

論文

Colossal negative thermal expansion induced by magnetic phase competition on frustrated lattices in Laves phase compound (Hf,Ta)Fe$$_2$$

Li, B.; Luo, X. H.*; Wang, H.*; Ren, W. J.*; Yano, S.*; Wang, C.-W.*; Gardner, J. S.*; Liss, K.-D.*; Miao, P.*; Lee, S.-H.*; et al.

Physical Review B, 93(22), p.224405_1 - 224405_6, 2016/06

https://doi.org/10.1103/PhysRevB.93.224405
 被引用回数：56 パーセンタイル：87.40(Materials Science, Multidisciplinary)

Competition between ferromagnetic and antiferromagnetic phases on frustrated lattices in hexagonal Laves phase compound Hf$$_{0.86}$$Ta$$_{0.14}$$Fe$$_2$$ is investigated by using neutron diffraction as a function of temperature and magnetic fields and density-functional-theory calculations. At 325 K, the compound orders into the 120$$^{circ}$$ frustrated antiferromagnetic state with well-reduced magnetic moment and an in-plane lattice contraction simultaneously sets in. With further cooling down, however, the accumulated distortion in turn destabilizes this susceptible frustrated structure. The frustration is completely relieved at 255 K when the first-order transition to the ferromagnetic state takes place, where a colossal negative volumetric thermal expansion, $$-123 times 10^{-6}$$/K, is obtained. Meanwhile, the antiferromagnetic state can be suppressed by few Tesla magnetic fields, which results in a colossal positive magnetostriction. Such delicate competition is attributed to the giant magnetic fluctuation inherent in the frustrated antiferromagnetic state. Therefore, the magnetoelastic instability is approached even under a small perturbation.

論文

Overview of plasma-material interaction experiments on EAST employing MAPES

Ding, F.*; Luo, G.-N.*; Pitts, R.*; Litnovsky, A.*; Gong, X.*; Ding, R.*; Mao, H.*; Zhou, H.*; Wampler, W. R.*; Stangeby, P. C.*; et al.

Journal of Nuclear Materials, 455(1-3), p.710 - 716, 2014/12

https://doi.org/10.1016/j.jnucmat.2014.09.017
 被引用回数：28 パーセンタイル：88.29(Materials Science, Multidisciplinary)

A movable material probe system (Material and Plasma Evaluation System: MAPES) with an independent pumping system and a sample exchange chamber has been developed and installed on a horizontal port of the EAST tokamak for studies of plasma material interaction (PMI). In the 2012 experimental campaign, deposition and erosion were studied for three samples: mock-up of the outer first wall panels (FWPs) in ITER, castellated tungsten, and molybdenum mirrors. The FWPs with carbon deposition layer were exposed to helium plasmas. The maximum erosion rate of the carbon was valuated to be 8 nm/s. The castellated tungsten with rectangular cells and roof-like shaped cells was exposed to deuterium plasmas to compare amount of deposits on the gap surface. The amount of carbon and boron impurities on the gap surface of the roof-like shaped cells were reduced to less than 30% compared with that of the rectangular cells. The molybdenum mirrors of which protective ducts are installed in front were exposed to deuterium plasmas in order to investigate effects of length of the ducts. It was found that the reflectivity of the mirrors with 60 mm-long protective ducts is kept the initial reflectivity.

論文

Nitrate facilitates cadmium uptake, transport and accumulation in the hyperaccumulator ${it Sedum plumbizincicola}$

Hu, P.*; 尹 永根; 石川 覚*; 鈴井 伸郎; 河地 有木; 藤巻 秀; 井倉 将人*; Yuan, C.*; Huang, J.*; Li, Z.*; et al.

Environmental Science and Pollution Research, 20(9), p.6306 - 6316, 2013/09

https://doi.org/10.1007/s11356-013-1680-3
 被引用回数：57 パーセンタイル：80.00(Environmental Sciences)

${it Sedum plumbizincicola}$, a species in the family Crassulaceae, has been reported to be a Cd hyperaccumulator exhibiting fast growth, large biomass, asexual reproduction and perennial habit and showing remarkable potential in the phytoextraction of Cd from polluted soils. The aims of this study are to investigate whether and how the nitrogen form (nitrate (NO$$_{3}$$$$^{-}$$) versus ammonium (NH$$_{4}$$$$^{+}$$)) influences cadmium (Cd) uptake and translocation and subsequent Cd phytoextraction by the ${it S. plumbizincicola}$. This is the first report of successful visualisation and quantification of Cd uptake and root-to-shoot translocation in intact plants of the hyperaccumulator species ${it S. plumbizincicola}$ supplied with different forms of inorganic N using positron-emitting tracer imaging system (PETIS), a real-time imaging method.

論文

Deuterium retention, blistering and local melting at tungsten exposed to high-fluence deuterium plasma

洲 亘; 中道 勝; Alimov, V.; Luo, G.-N.*; 磯部 兼嗣; 山西 敏彦

Journal of Nuclear Materials, 390-391, p.1017 - 1021, 2009/06

https://doi.org/10.1016/j.jnucmat.2009.01.267
 被引用回数：53 パーセンタイル：94.94(Materials Science, Multidisciplinary)

大きいフラックス(10$$^{22}$$D$$^{+}$$/m$$^{2}$$/s)と低いエネルギー(38eV)の重水素プラズマ(フルエンス:$$>$$10$$^{26}$$D/m$$^{2}$$)照射によるタングステンでのブリスタリング,重水素滞留及び局所的な溶融について、SEM, FIB, TDS、及びEPMAを用いて調べた。ブリスタリングと重水素滞留は、顕著な温度依存性及びフルエンス依存性を示したが、ブリスタリングが重水素-空孔のクラスタ形成,拡散と凝縮によるものと考えられ、その機構の解明によりブリスタリングの抑制に指針が与えられた。また、局所的な溶融はフレークのある結晶粒に現れ、フレークとバルク材との熱伝導の損失によるものと考えられる。

論文

Mechanisms of retention and blistering in near-surface region of tungsten exposed to high flux deuterium plasmas of tens of eV

洲 亘; Luo, G.; 山西 敏彦

Journal of Nuclear Materials, 367-370(2), p.1463 - 1467, 2007/08

https://doi.org/10.1016/j.jnucmat.2007.04.005
 被引用回数：70 パーセンタイル：96.54(Materials Science, Multidisciplinary)

数十eVの高フラックス重水素プラズマ照射によるタングステンでの滞留とブリスタリングの機構を解明するため、各種分析・観察手法(XRD, TEM, SEM, TDS, NRA、及びERDA)による測定・観察を行った。1.5$$^{circ}$$の固定入射角のXRD測定により、重水素プラズマ照射後のタングステン表面付近の格子定数が変化していないことを確認した。このことは、重水素が空隙サイトに存在せず、重水素-空孔複合体を形成してバブル(空孔クラスターやボイドに集合している重水素分子)に成長していることを示唆している。また、重水素プラズマ照射後のタングステン断面のTEM観察により、大きいブリスタ(直径:数ミクロン,結晶粒に相当)の発生前、表面付近に直径30nm程度の小さいブリスタやナノ亀裂が形成されていることを明らかにした。さらに、重水素は、照射後のタングステンに分子として滞留していること(TDS結果)、並びに最大重水素/タングステンの原子比が1-2%に到達していること(NRAとERDAの結果)を明らかにした。以上の結果は、空孔型欠陥が滞留重水素の侵入に伴ってタングステンの表面付近に生成されることを示唆しているものである。

論文

Microstructure dependence of deuterium retention and blistering in the near-surface region of tungsten exposed to high flux deuterium plasmas of 38 eV at 315 K

洲 亘; 河裾 厚男; 三輪 幸夫; 若井 栄一; Luo, G.-N.*; 山西 敏彦

Physica Scripta, T128, p.96 - 99, 2007/03

https://doi.org/10.1088/0031-8949/2007/T128/019
 被引用回数：97 パーセンタイル：92.36(Physics, Multidisciplinary)

タングステン焼鈍材,部分再結晶材,完全再結晶材,単結晶材での重水素滞留挙動とブリスタリングを昇温脱離法,走査型電子顕微鏡,陽電子消滅法などで調べた。10$$^{27}$$ D/m$$^{-2}$$までの高フルエンス照射の試料では、ブリスタからの重水素の爆発的な放出及びブリスタの爆裂を昇温脱離測定と走査型電子顕微鏡観察で確認した。また、陽電子消滅法により、完全再結晶材での欠陥がもっとも少ないことを、並びに部分再結晶材では重水素プラズマ照射による空孔の生成を観測した。さらに、電子後方散乱回折により、ブリスタリングが(111)に近い方位の結晶粒に優先的に起こることを明らかにした。

論文

Application of Kelvin probe to studies of fusion reactor materials under irradiation

Luo, G.-N.*; 山口 憲司; 寺井 隆幸*; 山脇 道夫*

Plasma Science and Technology, 7(4), p.2982 - 2984, 2005/08

https://doi.org/10.1088/1009-0630/7/4/026

核融合炉で使用される金属,セラミックス材料に対して高エネルギー(MeV)ないしは低エネルギー(500eV)のHeイオンを照射し、照射に伴う仕事関数変化をケルビン計により測定した。1MeVのビームでNiを照射した場合、仕事関数は照射量に対して単調に減少したが、500eVのイオンに対しては、照射開始直後こそ仕事関数は減少するものの、その後照射量とともに増加した。実験結果を説明するため、計算コードを活用するとともに表面層に関するモデルを考案した。一方、Li系セラミックス材料では、ケルビン計の出力が表面での帯電による効果に強く支配されることを、モデルにより定性的に説明した。

論文

Electronic structure of carbon nitride thin films studied by X-ray spectroscopy techniques

Hellgren, N.*; Guo, J.*; Luo, Y.*; S${aa}$the, C.*; 安居院 あかね; Kashtanov, S.*; Nordgren, J.*; ${AA}$gren, H.*; Sundgren, J.-E.*

Thin Solid Films, 471(1-2), p.19 - 34, 2005/01

https://doi.org/10.1016/j.tsf.2004.03.027
 被引用回数：140 パーセンタイル：96.62(Materials Science, Multidisciplinary)

窒化炭素は近年ハードディスクや記録ヘッドなどの材料として着目されている。本研究ではマグネトスパッタ法によって作成した窒化炭素薄膜の電子構造を、軟X線光電子分光,X線吸収分光法,発光分光法によって測定した。これにより、薄膜作成時の温度などの条件で窒素-炭素の結合や、そのマイクロストラクチャーが変化することがわかった。

報告書

Characteristics of a low energy and high flux compact plasma source and preliminary results in studying surface modification of tungsten irradiated by the source

Luo, G.; 洲 亘; 中村 博文; 大平 茂; 林 巧; 西 正孝

JAERI-Tech 2004-031, 27 Pages, 2004/03

JAERI-Tech-2004-031.pdf:2.88MB

トカマクのプラズマ-表面相互作用を模擬する小型プラズマ源装置を製作した。この装置は、小型(全長1m)であるにもかかわらず、ITERダイバータの周辺プラズマに相当する低エネルギー(100eV以下)・高フラックス(約10$$^{22}$$/m$$^{2}$$/s)のプラズマビームを生成できる特徴を持つ装置である。本報告では、本装置の構成と特性、具体的にはフィラメント,アーク放電,磁場,バイアスなどによるプラズマビームへの影響について説明する。また、タングステンを試料として行った予備的な照射試験の結果についても報告する。焼結後熱圧延したタングステン試料片(0.1mm厚)に重水素イオンフラックス2$$times$$10$$^{21}$$$$sim$$1$$times$$10$$^{22}$$/m$$^{2}$$/s,フルエンス4$$times$$10$$^{22}$$$$sim$$1$$times$$10$$^{26}$$/m$$^{2}$$,エネルギー100eV前後のプラズマビームを照射させ、1$$times$$10$$^{23}$$/m$$^{2}$$以上のフルエンスで試料表面にブリスタの発生を観測した。

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