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論文

Quantitative analysis of microstructure evolution, stress partitioning and thermodynamics in the dynamic transformation of Fe-14Ni alloy

Li, L.*; 宮本 吾郎*; Zhang, Y.*; Li, M.*; 諸岡 聡; 及川 勝成*; 友田 陽*; 古原 忠*

Journal of Materials Science & Technology, 184, p.221 - 234, 2024/06

 被引用回数:0 パーセンタイル:0(Materials Science, Multidisciplinary)

Dynamic transformation (DT) of austenite ($$gamma$$) to ferrite ($$alpha$$) in the hot deformation of various carbon steels was widely investigated. However, the nature of DT remains unclear due to the lack of quantitative analysis of stress partitioning between two phases and the uncertainty of local distribution of substitutional elements at the interface in multi-component carbon steels used in the previous studies. Therefore, in the present study, a binary Fe-Ni alloy with $$alpha$$+$$gamma$$ duplex microstructure in equilibrium was prepared and isothermally compressed in $$alpha$$+$$gamma$$ two-phase region to achieve quantitative analysis of microstructure evolution, stress partitioning and thermodynamics during DT. $$gamma$$ to $$alpha$$ DT during isothermal compression and $$alpha$$ to $$gamma$$ reverse transformation on isothermal annealing under unloaded condition after deformation were accompanied by Ni partitioning. The lattice strains during thermomechanical processing were obtained via in-situ neutron diffraction measurement, based on which the stress partitioning behavior between $$gamma$$ and $$alpha$$ was discussed by using the generalized Hooke's law. A thermodynamic framework for the isothermal deformation in solids was established based on the basic laws of thermodynamics, and it was shown that the total Helmholtz free energy change in the deformable material during the isothermal process should be smaller than the work done to the deformable material. Under the present thermodynamic framework, the microstructure evolution in the isothermal compression of Fe-14Ni alloy was well explained by considering the changes in chemical free energy, plastic and elastic energies and the work done to the material. In addition, the stabilization of the soft $$alpha$$ phase in Fe-14Ni alloy by deformation was rationalized since the $$gamma$$ to $$alpha$$ transformation decreased the total Helmholtz free energy by decreasing the elastic and dislocation energies.

論文

A Systematic approach for the adequacy analysis of a set of experimental databases: Application in the framework of the ATRIUM activity

Baccou, J.*; Glantz, T.*; Ghione, A.*; Sargentini, L.*; Fillion, P.*; Damblin, G.*; Sueur, R.*; Iooss, B.*; Fang, J.*; Liu, J.*; et al.

Nuclear Engineering and Design, 421, p.113035_1 - 113035_16, 2024/05

In the Best-Estimate Plus Uncertainty (BEPU) framework, the use of best-estimate code requires to go through a Verification, Validation and Uncertainty Quantification process (VVUQ). The relevance of the experimental data in relation to the physical phenomena of interest in the VVUQ process is crucial. Adequacy analysis of selected experimental databases addresses this problem. The outcomes of the analysis can be used to select a subset of relevant experimental data, to encourage designing new experiments or to drop some experiments from a database because of their substantial lack of adequacy. The development of a specific transparent and reproducible approach to analyze the relevance of experimental data for VVUQ still remains open and is the topic of this contribution. In this paper, the concept of adequacy initially introduced in the OECD/NEA SAPIUM (Systematic APproach for model Input Uncertainty quantification Methodology) activity is formalized. It is defined through two key properties, called representativeness and completeness, that allows considering the multifactorial dimension of the adequacy problem. A new systematic approach is then proposed to analyze the adequacy of a set of experimental databases. It relies on the introduction of two sets of criteria to characterize representativeness and completeness and on the use of multi-criteria decision analysis method to perform the analysis. Finally, the approach is applied in the framework of the new OECD/NEA ATRIUM activity which includes a set of practical IUQ exercises in thermal-hydraulics to test the SAPIUM guideline in determining input uncertainties and forward propagating them on an application case. It allows evaluating the adequacy of eight experimental databases coming from the Super Moby-dick, Sozzi-Sutherland and Marviken experiments and identifying the most adequate ones.

論文

Gradient residual strain measurement procedure in surface impacted railway steel axles by using neutron scattering

Zhou, L.*; Zhang, H.*; Qin, T. Y.*; Hu, F. F.*; 徐 平光; Ao, N.*; Su, Y. H.; He, L. H.*; Li, X. H.*; Zhang, J. R.*; et al.

Metallurgical and Materials Transactions A, 11 Pages, 2024/00

 被引用回数:0

High-speed railway S38C axles undergo surface induction hardening for durability, but are susceptible to fatigue cracks from foreign object impact. The neutron diffraction method was employed to measure the residual strain in S38C axles, obtaining microscopic lattice distortion data, for the gradient layer at a depth of 8 mm under the surface. The results showed that after induction-hardening, the microscopic lattice distortion had a gradient distribution, decreasing with the distance from the surface. However, in the case of impacting speed of 600 km/m, the average microscopic lattice distortion increased with the distance from the surface, reaching a maximum augmentation of 55 pct. These findings indicate a strong experimental basis, and improve our understanding of the relationship between macroscopic residual stress and decision-making, in regard to operation and maintenance.

論文

Direct observation of topological magnon polarons in a multiferroic material

Bao, S.*; Gu, Z.-L.*; Shangguan, Y.*; Huang, Z.*; Liao, J.*; Zhao, X.*; Zhang, B.*; Dong, Z.-Y.*; Wang, W.*; 梶本 亮一; et al.

Nature Communications (Internet), 14, p.6093_1 - 6093_9, 2023/09

 被引用回数:1 パーセンタイル:61.99(Multidisciplinary Sciences)

Magnon polarons are novel elementary excitations possessing hybrid magnonic and phononic signatures, and are responsible for many exotic spintronic and magnonic phenomena. Despite long-term sustained experimental efforts in chasing for magnon polarons, direct spectroscopic evidence of their existence is hardly observed. Here, we report the direct observation of magnon polarons using neutron spectroscopy on a multiferroic Fe$$_{2}$$Mo$$_{3}$$O$$_{8}$$ possessing strong magnon-phonon coupling. Specifically, below the magnetic ordering temperature, a gap opens at the nominal intersection of the original magnon and phonon bands, leading to two separated magnon-polaron bands. Each of the bands undergoes mixing, interconverting and reversing between its magnonic and phononic components. We attribute the formation of magnon polarons to the strong magnon-phonon coupling induced by Dzyaloshinskii-Moriya interaction. Intriguingly, we find that the band-inverted magnon polarons are topologically nontrivial. These results uncover exotic elementary excitations arising from the magnon-phonon coupling, and offer a new route to topological states by considering hybridizations between different types of fundamental excitations.

論文

A Predicted CRISPR-mediated symbiosis between uncultivated archaea

Esser, S. P.*; Rahlff, J.*; Zhao, W.*; Predl, M.*; Plewka, J.*; Sures, K.*; Wimmer, F.*; Lee, J.*; Adam, P. S.*; McGonigle, J.*; et al.

Nature Microbiology (Internet), 8(9), p.1619 - 1633, 2023/09

 被引用回数:2 パーセンタイル:79.73(Microbiology)

CRISPR-Cas systems defend prokaryotic cells from viruses, plasmids, and other mobile genetic elements. Capitalizing on multi-omics approaches, we show here that the CRISPR-Cas systems of uncultivated archaea also play an integral role in mitigating potentially detrimental interactions with episymbionts. A comprehensive analysis of CRISPR-Cas-based infection histories revealed that uncultivated deep-subsurface archaeal primary-producers defend themselves from archaeal episymbionts of the DPANN superphylum of archaea, some of which are known to fuse their membranes with their host. We show that host cells counter these attacks by deploying one of two CRISPR-Cas systems (type I-B and type III-A) to target and disrupt essential genes in the episymbiont. However, genome-scale modeling of metabolic interactions between two deep subsurface host-symbiont systems revealed that host cells also benefit from the symbionts via metabolic complementation. We speculate that populations of these uncultivated archaeal episymbionts are currently transitioning from a parasitic lifestyle to one of mutualism, as must have occurred in countless mutualistic systems known today. By expanding our analysis to thousands of archaeal genomes, we conclude that CRISPR-Cas mediated resistance to archaeal episymbiosis evolved independently in various archaeal lineages and may be a wide-spread evolutionary phenomenon.

論文

Pressure engineering of van der Waals compound RhI$$_3$$; Bandgap narrowing, metallization, and remarkable enhancement of photoelectric activity

Fang, Y.*; Kong, L.*; Wang, R.*; Zhang, Z.*; Li, Z.*; Wu, Y.*; Bu, K.*; Liu, X.*; Yan, S.*; 服部 高典; et al.

Materials Today Physics (Internet), 34, p.101083_1 - 101083_7, 2023/05

 被引用回数:1 パーセンタイル:0(Materials Science, Multidisciplinary)

層状ファンデルワールスハライドは、外部圧力に対して特に敏感であるため、目的とする性質を持つ構造にチューンすることが可能となる。一方で、圧力に非常に敏感であるという特性は、同時に目的とする機能の実現に有害な相転移や格子歪みを引き起こす可能性があるためその操作は依然として困難である。この研究では、層状RhI$$_3$$結晶が持つ極めて弱い層間結合と高い機能可変性を観察した。5GPaという適度な圧力をかけると圧力誘起相転移が起こり、積層構造に変化が現れた。驚くべきことに、この相転移は、圧力に対してほぼ直線的なバンドギャップ減少という傾向に影響を与えなかった。また、より高い圧力では、1.3eVの赤方偏移というかなり大きな調整幅を伴う金属相が観測された。さらに、RhI$$_3$$のキャリア濃度は30GPaで4桁増加し、光電流は7.8GPaで5桁増加することが確認された。これらの結果は、ファンデルワールスハライドの層状構造という特異な特徴を生かした探索、調整、理解のための新たな機会を創出し、原子レベルの薄さを持つマテリアルバイデザインに基づく将来のデバイスとして有望である。

論文

Fatigue crack non-propagation behavior of a gradient steel structure from induction hardened railway axles

Zhang, H.*; Wu, S. C.*; Ao, N.*; Zhang, J. W.*; Li, H.*; Zhou, L.*; 徐 平光; Su, Y. H.

International Journal of Fatigue, 166, p.107296_1 - 107296_11, 2023/01

 被引用回数:4 パーセンタイル:61.91(Engineering, Mechanical)

Abnormal damages in railway axles can lead to a significant hazard to running safety and reliability. To this end, a surface treatment was selected to effectively inhibit fatigue crack initiation and growth. In this study, a single edge notch bending fatigue test campaign with artificial notches was conducted to elucidate the fatigue crack non-propagation behavior in railway S38C axles subjected to an induction hardening process. The fatigue cracking behavior in the gradient structure was revealed by optical microscopy, electron backscatter diffraction, and fractography. The microhardness distribution was measured using a Vickers tester. The obtained results show that the microhardness of the strengthening layer is nearly triple that of the matrix. Owing to the gradient microstructures and hardness, as well as compressive residual stress, the fatigue long crack propagates faster once it passes through the hardened zone (approximately 2.0 mm in the radial depth). Thereafter, local retarding (including deflection, branching, and blunting) of the long crack occurs because of the relatively coarse ferrite and pearlite in the transition region and matrix. Totally, this fatigue cracking resistance is reasonably believed to be due to the gradient microstructure and residual stress. These findings help to tailor a suitable detection strategy for maximum defects or cracks in railway axles.

論文

Ten years of warming increased plant-derived carbon accumulation in an East Asian monsoon forest

Zhang, J.*; Kuang, L.*; Mou, Z.*; 近藤 俊明*; 小嵐 淳; 安藤 麻里子; Li, Y.*; Tang, X.*; Wang, Y.-P.*; Pe$~n$uelas, J.*; et al.

Plant and Soil, 481(1-2), p.349 - 365, 2022/12

 被引用回数:3 パーセンタイル:22.98(Agronomy)

Soil warming effects on soil organic carbon (SOC) decomposition and stabilization are highly variable, and the underlying mechanisms are poorly understood. In this study, concentration, stability (dissolved, particle and mineral-associated SOC), and source (plant-derived and microbial-derived) of SOC, soil microbial community composition, and enzyme activities were studied in a 10-year soil warming field experiment in an East Asian monsoon forest. The results showed that 10-year soil warming significantly enhanced SOC in the top 0-10 cm soil. The increased SOC induced by warming was mainly derived from plants with lignin markers, accompanied by a decrease in microbial-derived SOC. This highlights an urgent need for a better understanding of how the contrasting effects of plant- and microbial-derived C mediate the response of the SOC pool to warming across different biomes.

論文

Novel graphene-based foam composite as a highly reactive filter medium for the efficient removal of gemfibrozil from (waste)water

Khalil, A. M. E.*; Han, L.*; Maamoun, I.; Tabish, T. A.*; Chen, Y.*; Eljamal, O.*; Zhang, S.*; Butler, D.*; Memon, F. A.*

Advanced Sustainable Systems (Internet), 6(8), p.2200016_1 - 2200016_16, 2022/08

 被引用回数:2 パーセンタイル:29.01(Green & Sustainable Science & Technology)

Graphene-based materials have emerged as alternative adsorbents, but their success in removing pharmaceutical contaminants has been limited due to degradation caused by restacking and limited control over their sizes and porosities. Driven by this issue, in the current study, to counteract the restacking behavior, graphene sheets are supported on a thread/rod-like matrix structure in a boron nitride foam material, and a novel porous composite foam-supported graphene is synthesized. The as-prepared novel composite offers extraordinary features, such as high absorption kinetics, large available surface area, high porosity, ecofriendliness and cost-effective synthesis, and excellent affinity to emerging pharmaceutical contaminants. When batch-testing graphene-based foam material and porous graphene nanosheets to remove gemfibrozil (GEM) from wastewater samples, rapid adsorption kinetics (less than 5 min) are exhibited by the graphene-based foam. Column filter studies are conducted for both materials to test their performance in removing GEM from distilled water, synthetic graywater, and actual wastewater. Overall, the foam composite-based filter marginally outperforms the sand-supported graphene filter and significantly outperforms the unsupported graphene filter. A numerical MATLAB model is developed to simulate the reactive solute transport of GEM influent through the foam filter. Also, a formal sensitivity analysis is conducted to identify the key parameters influencing the model results.

論文

Fine structure in the $$alpha$$ decay of the 8$$^{+}$$ isomer in $$^{216,218}$$U

Zhang, M. M.*; Tian, Y. L.*; Wang, Y. S.*; Zhang, Z. Y.*; Gan, Z. G.*; Yang, H. B.*; Huang, M. H.*; Ma, L.*; Yang, C. L.*; Wang, J. G.*; et al.

Physical Review C, 106(2), p.024305_1 - 024305_6, 2022/08

 被引用回数:2 パーセンタイル:52.69(Physics, Nuclear)

The extremely neutron-deficient even-even uranium isotopes $$^{216,218}$$U were produced in the complete-fusion reactions induced by impinging $$^{40}$$Ar and $$^{40}$$Ca ions on $$^{180,182,184}$$W targets. Fusion evaporation residues were separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and subsequently identified using the recoil-$$alpha$$-correlation method. In this paper, we report on new $$alpha$$-decay activities with $$E_{alpha} = 10163(27)$$ keV for $$^{216}$$U and $$E_{alpha} = 10073(16)$$ keV for $$^{218}$$U, which decay from the 8$$^{+}$$ isomeric states of $$^{216,218}$$U into the 2$$^{+}$$ states of their daughter nuclei $$^{212,214}$$Th, respectively. The new results extend the systematics of the $$alpha$$-decay fine structure for the $$N$$ = 124 and 126 even-even isotones.

論文

The $$omega^{3}$$ scaling of the vibrational density of states in quasi-2D nanoconfined solids

Yu, Y.*; Yang, C.*; Baggioli, M.*; Phillips, A. E.*; Zaccone, A.*; Zhang, L.*; 梶本 亮一; 中村 充孝; Yu, D.*; Hong, L.*

Nature Communications (Internet), 13, p.3649_1 - 3649_10, 2022/06

 被引用回数:8 パーセンタイル:81.66(Multidisciplinary Sciences)

The vibrational properties of crystalline bulk materials are well described by Debye theory, which successfully predicts the quadratic $$omega^{2}$$ low-frequency scaling of the vibrational density of states. However, the analogous framework for nanoconfined materials with fewer degrees of freedom has been far less well explored. Using inelastic neutron scattering, we characterize the vibrational density of states of amorphous ice confined inside graphene oxide membranes and we observe a crossover from the Debye $$omega^{2}$$ scaling to an anomalous $$omega^{3}$$ behaviour upon reducing the confinement size L.

論文

Status of the uncertainty quantification for severe accident sequences of different NPP-designs in the frame of the H-2020 project MUSA

Brumm, S.*; Gabrielli, F.*; Sanchez-Espinoza, V.*; Groudev, P.*; Ou, P.*; Zhang, W.*; Malkhasyan, A.*; Bocanegra, R.*; Herranz, L. E.*; Berda$"i$, M.*; et al.

Proceedings of 10th European Review Meeting on Severe Accident Research (ERMSAR 2022) (Internet), 13 Pages, 2022/05

The current HORIZON-2020 project on "Management and Uncertainties of Severe Accidents (MUSA)" aims at applying Uncertainty Quantification (UQ) in the modeling of Severe Accidents (SA), particularly in predicting the radiological source term of mitigated and unmitigated accident scenarios. Within its application part, the project is devoted to the uncertainty quantification of different severe accident codes when predicting the radiological source term of selected severe accident sequences of different nuclear power plant designs, e.g. PWR, VVER, and BWR. Key steps for this investigation are, (a) the selection of severe accident sequences for each reactor design, (b) the development of a reference input model for the specific design and SA-code, (c) the selection of a list of uncertain model parameters to be investigated, (d) the choice of an UQ-tool e.g. DAKOTA, SUSA, URANIE, etc., (e) the definition of the figures of merit for the UA-analysis, (f) the performance of the simulations with the SA-codes, and, (g) the statistical evaluation of the results using the capabilities, i.e. methods and tools offered by the UQ-tools. This paper describes the project status of the UQ of different SA codes for the selected SA sequences, and the technical challenges and lessons learnt from the preparatory and exploratory investigations performed.

論文

Metalloid substitution elevates simultaneously the strength and ductility of face-centered-cubic high-entropy alloys

Wei, D.*; Wang, L.*; Zhang, Y.*; Gong, W.; 都留 智仁; Lobzenko, I.; Jiang, J.*; Harjo, S.; 川崎 卓郎; Bae, J. W.*; et al.

Acta Materialia, 225, p.117571_1 - 117571_16, 2022/02

 被引用回数:59 パーセンタイル:99.75(Materials Science, Multidisciplinary)

Recently-developed high-entropy alloys (HEAs) containing multiple principal metallic elements have ex-tended the compositional space of solid solutions and the range of their mechanical properties. Here we show that the realm of possibilities can be further expanded through substituting the constituent metals with metalloids, which are desirable for tailoring strength/ductility because they have chemical interactions and atomic sizes distinctly different from the host metallic elements. Specifically, the metalloid substitution increases local lattice distortion and short-range chemical inhomogeneities to elevate strength, and in the meantime reduces the stacking fault energy to discourage dynamic recovery and encourage defect accumulation via partial-dislocation-mediated activities. These impart potent dislocation storage to improve the strain hardening capability, which is essential for sustaining large tensile elongation. As such, metalloid substitution into HEAs evades the normally expected strength-ductility trade-off, enabling an unusual synergy of high tensile strength and extraordinary ductility for these single-phase solid solutions.

論文

Modelling and simulation of the source term for a sodium cooled fast reactor under hypothetical severe accident conditions; Final report of a coordinated research project

Arokiaswamy, J. A.*; Batra, C.*; Chang, J. E.*; Garcia, M.*; Herranz, L. E.*; Klimonov, I. A.*; Kriventsev, V.*; Li, S.*; Liegeard, C.*; Mahanes, J.*; et al.

IAEA-TECDOC-2006, 380 Pages, 2022/00

IAEAの共同研究プロジェクト「シビアアクシデント条件下におけるプロトタイプナトリウム冷却高速炉からの放射性物質の放出」は、シビアアクシデント条件下における、リファレンスとなるナトリウム冷却高速炉の施設内における放射性物質および燃料粒子の存在量の、異なる時間スケールにおける現実的な数値シミュレーションを目的として実施された。解析のスコープは3つに分割され、3つのワークパッケージ(WP)として定義された:(1)炉内ソースターム評価、(2)一次系/格納容器系境界のソースターム評価、および(3)格納容器内の現象分析。WP-1の参加機関の結果を比較すると、希ガスおよび放射性セシウムの放出割合、およびカバーガスへの放射性核種の放出割合はよく一致した。共通の圧力履歴を用いたWP-2の解析では、各機関の解析結果はよく一致し、いずれの機関の解析手法も同程度の精度を有することが示された。先行するWPにおける解析と分離するため、放出割合をあらかじめ設定したスタンドアロンケースがWP-3にて定義された。WP-3の全参加機関によるスタンドアロンケースの解析結果は全般的に一致した。

論文

Paramagnetic spin Hall magnetoresistance

大柳 洸一*; Gomez-Perez, J. M.*; Zhang, X.-P.*; 吉川 貴史*; Chen, Y.*; Sagasta, E.*; Chuvilin, A.*; Hueso, L. E.*; Golovach, V. N.*; Sebastian Bergeret, F.*; et al.

Physical Review B, 104(13), p.134428_1 - 134428_14, 2021/10

 被引用回数:14 パーセンタイル:77.64(Materials Science, Multidisciplinary)

We report the observation of the spin Hall magnetoresistance (SMR) in a paramagnetic insulator. By measuring the transverse resistance in a Pt/Gd$$_3$$Ga$$_5$$O$$_{12}$$ (GGG) system at low temperatures, paramagnetic SMR is found to appear with an intensity that increases with the magnetic field aligning GGG's spins. The observed effect is well supported by a microscopic SMR theory, which provides the parameters governing the spin transport at the interface. Our findings clarify the mechanism of spin exchange at a Pt/GGG interface, and demonstrate tunable spin-transfer torque through the field-induced magnetization of GGG. In this regard, paramagnetic insulators offer a key property for future spintronic devices.

論文

New $$alpha$$-emitting isotope $$^{214}$$U and abnormal enhancement of $$alpha$$-particle clustering in lightest uranium isotopes

Zhang, Z. Y.*; Yang, H. B.*; Andreyev, A. N.; Liu, M. L.*; Ma, L.*; 他37名*

Physical Review Letters, 126(15), p.152502_1 - 152502_6, 2021/04

 被引用回数:40 パーセンタイル:96.23(Physics, Multidisciplinary)

A new $$alpha$$-emitting isotope $$^{214}$$U, produced by the fusion-evaporation reaction $$^{182}$$W($$^{36}$$Ar,4n)$$^{214}$$U, was identified by employing the gas-filled recoil separator SHANS and the recoil-$$alpha$$ correlation technique. More precise $$alpha$$-decay properties of even-even nuclei $$^{216,218}$$U were also measured in the reactions of $$^{40}$$Ar, $$^{40}$$Ca beams with $$^{180,182,184}$$W targets. By combining the experimental data, improved $$alpha$$-decay reduced widths $$delta$$$$^{2}$$ for the even-even Po-Pu nuclei in the vicinity of the magic neutron number ${it N}$ = 126 are deduced. Their systematic trends are discussed in terms of the ${it N}$ $$_{it p}$$ ${it N}$ $$_{it n}$$ scheme in order to study the influence of proton-neutron interaction on $$alpha$$ decay in this region of nuclei. It is strikingly found that the reduced widths of $$^{214,216}$$U are significantly enhanced by a factor of two as compared with the ${it N}$ $$_{it p}$$ ${it N}$ $$_{it n}$$ systematics for the 84 $$leq$$ ${it Z}$ $$leq$$ 90 and ${it N}$ $$<$$ 126 even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the $$pi$$1${it f}$ $$_{7/2}$$ and $$nu$$1${it f}$ $$_{5/2}$$ spin-orbit partner orbits, which is supported by the large-scale shell model calculation.

論文

Field-tuned magnetic structure and phase diagram of the honeycomb magnet YbCl$$_3$$

Hao, Y. Q.*; Wo, H. L.*; Gu, Y. M.*; Zhang, X. W.*; Gu, Y. Q.*; Zheng, S. Y.*; Zhao, Y.*; Xu, G. Y.*; Lynn, J. W.*; 中島 健次; et al.

Science China; Physics, Mechanics & Astronomy, 64(3), p.237411_1 - 237411_6, 2021/03

 被引用回数:6 パーセンタイル:61.42(Physics, Multidisciplinary)

We report thermodynamic and neutron diffraction measurements on the magnetic ordering properties of the honeycomb lattice magnet YbCl$$_3$$. We find YbCl$$_3$$ exhibits a N${'e}$el type long-range magnetic order at the wavevector (0, 0, 0) below T$$_N$$ = 600 mK. This magnetic order is associated with a small sharp peak in heat capacity and most magnetic entropy release occurs above the magnetic ordering temperature. The magnetic moment lies in-plane, parallel to the monoclinic a-axis, whose magnitude m$$_{rm Yb}$$ = 0.86(3) $$mu_B$$ is considerably smaller than the expected fully ordered moment of 2.24 $$mu_B$$ for the doublet crystal-field ground state. The magnetic ordering moment gradually increases with increasing magnetic field perpendicular to the ab-plane, reaching a maximum value of 1.6(2) $$mu_B$$ at 4 T, before it is completely suppressed above $$sim$$9 T. These results indicate the presence of strong quantum fluctuations in YbCl$$_3$$.

論文

Coordination number regulation of molybdenum single-atom nanozyme peroxidase-like specificity

Wang, Y.*; Jia, G.*; Cui, X.*; Zhao, X.*; Zhang, Q.*; Gu, L.*; Zheng, L.*; Li, L. H.*; Wu, Q.*; Singh, D. J.*; et al.

Chem, 7(2), p.436 - 449, 2021/02

 被引用回数:194 パーセンタイル:99.8(Chemistry, Multidisciplinary)

Nanozymes are promising alternatives to natural enzymes, but their use remains limited owing to poor specificity. Overcoming this is extremely challenging due to the intrinsic structural complexity of these systems. We report theoretical design and experimental realization of a series of heterogeneous molybdenum single-atom nanozymes (named Mo$$_{rm{SA}}$$-N$$_{x}$$-C), wherein we find that the peroxidase-like specificity is well regulated by the coordination numbers of single Mo sites. The resulting Mo$$_{rm{SA}}$$-N$$_{3}$$-C catalyst shows exclusive peroxidase-like behavior. It achieves this behavior via a homolytic pathway, whereas Mo$$_{rm{SA}}$$-N$$_{2}$$-C and Mo$$_{rm{SA}}$$-N$$_{4}$$-C catalysts have a different heterolytic pathway. The mechanism of this coordination-number-dependent enzymatic specificity is attributed to geometrical structure differences and orientation relationships of the frontier molecular orbitals.

論文

Stacking fault driven phase transformation in CrCoNi medium entropy alloy

He, H.*; Naeem, M.*; Zhang, F.*; Zhao, Y.*; Harjo, S.; 川崎 卓郎; Wang, B.*; Wu, X.*; Lan, S.*; Wu, Z.*; et al.

Nano Letters, 21(3), p.1419 - 1426, 2021/02

 被引用回数:41 パーセンタイル:95.34(Chemistry, Multidisciplinary)

In CrCoNi, a so-called medium-entropy alloy, an fcc-to-hcp phase transformation has long been anticipated. Here, we report an in situ loading study with neutron diffraction, which revealed a bulk fcc-to-hcp phase transformation in CrCoNi at 15 K under tensile loading. By correlating deformation characteristics of the fcc phase with the development of the hcp phase, it is shown that the nucleation of the hcp phase was triggered by intrinsic stacking faults. The confirmation of a bulk phase transformation adds to the myriads of deformation mechanisms available in CrCoNi, which together underpin the unusually large ductility at low temperatures.

論文

Extremely high dislocation density and deformation pathway of CrMnFeCoNi high entropy alloy at ultralow temperature

Naeem, M.*; He, H.*; Harjo, S.; 川崎 卓郎; Zhang, F.*; Wang, B.*; Lan, S.*; Wu, Z.*; Wu, Y.*; Lu, Z.*; et al.

Scripta Materialia, 188, p.21 - 25, 2020/11

 被引用回数:56 パーセンタイル:97.51(Nanoscience & Nanotechnology)

The deformation behavior of CrMnFeCoNi high entropy alloy was investigated by in situ neutron diffraction at an ultralow temperature of 15 K. Analysis of the diffraction peak widths showed an extremely high dislocation density at 15 K, reaching $$sim$$10$$^{16}$$ m$$^{-2}$$. In addition, the dislocation density was found to closely follow the development of texture caused by deformation. In contrast to deformation by dislocation slip at room temperature, the ultralow-temperature deformation also involved stacking faults, twinning and serrations. The deformation pathway at ultralow temperature is outlined which is responsible for the extraordinary strength-ductility combination.

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