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Controlled moderative sulfidation-fabricated hierarchical heterogeneous nickel sulfides-based electrocatalyst with tripartite Mo doping for efficient oxygen evolution

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Journal of Energy Chemistry 2022年第5期31卷 780-788页

作者： Xing Yu Qingyun Lv Lulu She Long Hou yves fautrelle Zhongming Ren Guanghui Cao Xionggang Lu Xi Li State Key Laboratory of Advanced Special Steels School of Materials Science and EngineeringShanghai UniversityShanghai 200072China Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming Shanghai Jiao Tong UniversityShanghai 200240China SIMAP-EPM-Madylam/G-INP/CNRS PHELMABP 7538402 St Martin d’HeresCedexFrance

An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction(OER), due to the synergistically enhanced kinetics on enriched active sites and reconfigured electronic band structure. Here this work introduces hierarchical heterostructures into a NiMo@NiS/MoS_(2)@Ni_(2)S_(2)/MoO_(x)(NiMoS) composite by one-pot controlled moderative sulfidation. The optimal solvent composition and addition of NaOH enable NiMoS to own loose and porous structures, smaller nanoparticle sizes, optimal phase composition and chemical states of elements, improving the OER activity of NiMoS. To achieve current densities of 50 and 100 mA cm^(-1), small overpotentials of 275 and 306 mV are required respectively, together with a minor Tafel slope of 58 mV dec^(-1), which outperforms most reported sulfide catalysts and IrO_(2). The synergistic effects in the hierarchical heterostructures expose more active sites,adjust the electronic band structure, and enable the fast charge transfer kinetics, which construct an optimized local coordination environment for high OER electrocatalytic activity. Furthermore, the hierarchical heterostructures suppress the distinct lowering of electrical conductivity and collapse of pristine structures resulted from the metal oxidation and synchronous S leaching during OER, yielding competitive catalytic stability.

关键词： OER electrocatalysts Controlled moderative sulfidation Hierarchical heterostructures Nickel sulfides Tripartite Mo doping

Microstructure evolution and mechanical behavior of Ni-rich Ni-Mn-Ga alloys under compressive and tensile stresses

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Journal of Materials Science & Technology 2022年第2期97卷 113-122页

作者： Yue Wang Siyuan Yang Ting Zhou Long Hou Lansong Ba yves fautrelle Zhongming Ren Yanyan Zhu Zongbin Li Xi Li State Key Laboratory of Advanced Special Steels Shanghai UniversityShanghai 200072China Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming Shanghai Jiao Tong UniversityShanghai 200240China EPM-Madylam ENSHMG BP 38402St Martin d’Heres CedexFrance School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Key Laboratory for Anisotropy and Texture of Materials Northeastern UniversityShenyang 110819China

The microstructure evolution and mechanical behavior in directionally solidified Ni-rich Ni-Mn-Ga alloys with nominal compositions of Ni_(58)Mn_(25)Ga_(17) and Ni_(60)Mn_(25)Ga_(15) under compressive and tensile stresses have been investigated.The composition distribution shows the element Ni segregates in gamma phase,while elements Mn and Ga segregate in martensite phase.Furthermore,the microstructure orientation examined by electron backscatter diffraction(EBSD)indicates that beta phase has a preferred growth orientation of(001)_(A) in Ni_(58)Mn_(25)Ga_(17) alloys,while gamma phase has a preferred growth orientation of(001)_(γ) in Ni_(60)Mn_(25)Ga_(15) alloys.The fracture morphology suggests that the existence of ductile y phase can reduce the crack propagation and promote fracture strain,particularly in the Ni_(60)Mn_(25)Ga_(15) alloys.Finally,Schmid factor and deformation gradient tensor were calculated to well explain the crystallographic evolution during the detwinning under compressive and tensile stresses.The present findings not only elucidate the mechanism ofγphase on the mechanical behavior of Ni-rich Ni-Mn-Ga alloys,but also shed light on the composition design of high temperature Ni-Mn-Ga shape memory alloys.

关键词： Ni-Mn-Ga Gamma phase Tensile Compressive EBSD

Microstructural,crystallographic,and mechanical characteristics in Ni-Mn-Ga alloys directionally solidified under a transverse magnetic field

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Journal of Materials Science & Technology 2023年第11期142卷 10-21页

作者： Xi Li Long Hou Siyuan Yang Ting Zhou Yue Wang Xing Yu Zongbin Li Daoyong Cong yves fautrelle Zhongming Ren Yanyan Zhu Shanghai Key Lab of Advanced High-Temperature Materials and Precision Forming Shanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Advanced Special Steels Shanghai UniversityShanghai 200072China Key Laboratory for Anisotropy and Texture of Materials Northeastern UniversityShenyang 110819China Beijing Advanced Innovation Center for Materials Genome Engineering State Key Laboratory for Advanced Metals and MaterialsUniversity of Science and Technology BeijingBeijing 100083China EPM-Madylam ENSHMG BPSt Martin d’Heres 38402 CEDEXFrance

In this study,the effect of transverse magnetic field-assisted directional solidification(MFADS)on the microstructures in Ni-Mn-Ga alloys has been investigated.The results show that the magnetic field is capable of inducing transversal macrosegregation perpendicular to the magnetic field,causing the emergence of martensite clusters in the austenite matrix.Moreover,the magnetic field alleviates the microseg-regation on a dendritic scale and promotes the preferred growth of austenite dendrites.On the basis of the above investigation,several special samples are designed using the MFADS to study the crystallographic evolution and mechanical behavior during thermal/stress-induced martensite transformation.The martensite cluster in the austenite matrix is used to investigate the martensite transformation and growth under cooling-heating cycles.The crystallographic relationship and phase boundary microstructure between martensite and austenite have been characterized.In addition,the microsegregation on a dendritic scale can significantly influence the martensite variant distribution,corresponding to the performance during compressive circles based on the analysis of the deformation gradient tensor.The stress-induced superelasticity is closely dependent on orientation,well explained from the perspective of different resolved shear stress factors and correspondence variant pair formation transformation strain.The crystallographic evolution has been characterized during in-situ stress-induced transformation.The findings not only deepen the understanding of martensite transformation and mechanical behavior under a thermal/stress field in Ni-Mn-Ga alloys but also propose a promising strategy to obtain microstructure-controllable functional alloys by MFADS.

关键词： Magnetic field-assisted directional solidification Segregation Orientation Martensite transformation Superelasticity

Controlling and adjusting the concentration distribution during solidification process using static magnetic fields

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Journal of Materials Science & Technology 2020年第15期47卷 86-91页

作者： Pinfang Jiang Jiantao Wang Long Hou yves fautrelle Xi Li State Key Laboratory of Advanced Special Steels Shanghai UniversityShanghai200072PR China SIMAP-EPM-Madylam/G-INP/CNRS PHELMABP 7538402St Martin d'Heres CedexFrance

As concentration distribution changes have important effects on material structures and properties,controlling the concentration distribution is essential to alloy performance.The aim of the present work is to control and adjust the concentration distribution by the static magnetic field.It is found that the magnetic field disperses grain boundary segregation and causes the uniform distribution of concentration.Further,by the three-dimensional computed tomography(3 D-CT) reconstruction,the flow distribution is seen and the effect mechanism of the magnetic field is revealed.The present work may clarify the ambiguous understanding on the effect of the static magnetic field on solidification process.

关键词： Static magnetic feld Concentration distribution Structures

Effect of the simultaneous application of a high static magnetic field and a low alternating current on grain structure and grain boundary of pure aluminum

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Journal of Materials Science & Technology 2018年第12期34卷 2431-2438页

作者： Chengshuai Li Shaodong Hu Zhongming Ren yves fautrelle Xi Li State Key Laboratory of Advanced Special Steels Shanghai University SIMAP-EPM-Madylam/G-INP/CNRS PHELMA

Effect of the simultaneous application of a high static magnetic field and a low alternating electric current on the solidification structure of pure aluminum has been investigated. Results show that the refinement of the solidification structure is enhanced by the electric current under a certain magnetic field. However,when the magnetic field intensity exceeds a certain value, the refinement is impaired under a certain electric current. The observation by electron backscattered diffraction(EBSD) shows the complex fields have led to the increase of the low angle boundaries with the refinement. Moreover, the application of the static gradient magnetic field is capable of modifying the distribution of the refined grains. The above results may be attributed to the formation of the cavities during the electromagnetic vibration process and the high magnetic field.

关键词： Complex fields High magnetic field Refinement Grain boundaries

Nucleation kinetics of paramagnetic and diamagnetic metal melts under a high magnetic field

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Journal of Materials Science & Technology 2021年第14期73卷 165-170页

作者： Zhipeng Long Qiuyue Jiang Jiantao Wang Long Hou Xing Yu yves fautrelle Zhongming Ren Xi Li State Key Laboratory of Advanced Special Steels Shanghai UniversityShanghai200072China SIMAP-EPM-Madylam/G-INP/CNRS PHELMABP 75.38402St Martin d'Heres Cedex.France

The influence of a high magnetic field(HMF)on the nucleation kinetics of paramagnetic aluminum and diamagnetic zinc melts has been investigated by differential thermal analysis(DTA).It is found that the application of an HMF increases the undercooling of pure aluminum and pure zinc at the same heatingcooling rates.Moreover,the quantitative analysis of activation energy calculated from the DTA results using the Kissinger method manifests that the HMF reduces the activation energy of pure aluminum and pure zinc.Regardless of magnetism,the nucleation frequency under an HMF is higher than that without an HMF.Furthermore,the increase in undercooling under the HMF is mainly attributed to the increase of the contact angle,calculated by the functional relationship between the cooling rate and undercooling.This result is consistent with the increase of the calculated nucleation work for pure aluminum and pure zinc.Additionally,the increase in undercooling caused by the HMF is partly ascribed to the magnetic field-induced suppression of thermal convection in the undercooled melt.

关键词： Undercooling Activation energy Nucleation work High magnetic field

Effect of transverse static magnetic field on radial microstructure of hypereutectic aluminum alloy during directional solidification

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Journal of Materials Science & Technology 2021年第17期76卷 207-214页

作者： Shaodong Hu Long Hou Kang Wang Zhongmiao Liao Wen Zhu Aihua Yi Wenfang Li yves fautrelle Xi Li School of Materials Science and Engineering Dongguan University of TechnologyDongguan 523808China State Key Laboratory Advanced Special Steel Shanghai UniversityShanghai 200072China School of Materials Science and Engineering Xi'an Jiaotong UniversityXi'an710049China SIMAP-EPM-Madylam/G-INP/CNRS.PHELMA.38402 St Martin d'Heres Cedex.France

The effect of different scales thermoelectric magnetic convection(TEMC)on the radial solidification microstructure of hypereutectic Al alloy has been investigated under transverse static magnetic field during directional solidification,focusing on the formation of freckle.Our experimental and numerical simulation results indicate that the TEMC circulation at sample scale under transverse static magnetic field leads to the enrichment of solute Al on one side of the sample.The TEMC and the solute enrichment degree increase with the increase of magnetic field when the magnetic field increases to 0.5 T.The enrichment degree of solute elements under magnetic field is affected by temperature gradient and growth rate.The non-uniform distribution of solute Al in the radial direction of the sample results in the non-uniform distribution of primary dendrite arm spacing(PDAS).Moreover,the applied magnetic field can lead to freckle formation and its number increases with the increase of magnetic field.The change of freckle is consistent with the anisotropy TEMC caused by the anisotropy of primary dendrite or primary dendrite network under magnetic field.Finally,the mechanism of synergism effect of the anisotropy TEMC,the distribution of solute Al and the PDAS on freckle formation and evolution is studied during directional solidification under magnetic field.

关键词： Static magnetic field Directional solidification Melt flow Radial solidification microstructure Freckle

Effect of γ phase on mechanical behavior and detwinning evolution of directionally solidified Ni-Mn-Ga alloys under uniaxial compression

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Journal of Materials Science & Technology 2021年第7期66卷 91-96页

作者： Ying Niu Yue Wang Long Hou Lansong Ba Yanchao Dai yves fautrelle Zongbin Li Zhongming Rena Xi Li State Key Laboratory of Advanced Special Steels Shanghai UniversityShanghai200072China EPM-Madylam ENSHMG BP 38402St Martin d'Heres CedexFrance Key Laboratory for Anisotropy and Texture of Materials Northeastern UniversityShenyang110819China

Specimens with single-phase martensite, net-like γ/martensite mixed structure and lamella-likeγ/martensite mixed structure were designed to investigate the effect of the γ phase on the mechanical behavior and the detwinning of non-modulated(NM) martensitic variant in Ni-rich Ni-Mn-Ga alloys under uniaxial compression. It can be found the existence of the γ phase significantly enhances the compressive stresses, and the net-like γ phase specimen presents a higher value of compressive strain than that of the lamella-like γ phase specimen. Especially, the detwinning plateau of the lamella-like γ phase specimen is almost invisible due to the martensite colonies with low Schmid factors. Finally, according to the calculation of deformation gradient tensor, we found that the tensors along compression direction(εzz) of net-like γ phase/martensite mixed structure specimen and single-phase martensite specimen are lower than that of the specimen with lamella-like γ phase/martensite mixed structure, which well explained the detwinning strain for these specimens. The present study not only highlights the role ofγ phase on the mechanical behavior, but also provides more guidelines for the mechanical training of Ni-Mn-Ga shape memory alloys.

关键词： Ni-Mn-Ga alloys Directional solidification Compression Detwinning

Columnar-to-Equiaxed Transition During Directional Solidification Under Strong Magnetic Field

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Journal of Iron and Steel Research(International) 2012年第S2期19卷 1044-1047页

作者： LI Xi DU Da-fan Annie GAGNOUD yves fautrelle REN Zhong-ming Department of Material Science and Engineering Shanghai University SIMAP-EPM-Madylam/CNRS ENSHMG

Effects of strong magnetic fields on the columnar-to-equiaxed transition(CET) have been investigated experimentally.Experimental results show that the application of a strong magnetic field causes a dendrite fragmentation and then the CET.The thermoelectric magnetic force acting on cells/dendrites and equiaxed grains in the mushy zone has been studied numerically.Numerical results reveal that a torque is created on cells/dendrites and equiaxed grains and the value of the thermoelectric magnetic force increases as the magnetic field intensity increase.This torque breaks cells/dendrites and drives the rotation of equiaxed grains.As a consequence,the CET will occur during directional solidification under a strong magnetic field.This may initiate a new method to induce the CET via an applied strong magnetic field during directional solidification.

关键词： columnar-to-equiaxed transition strong magnetic field directional solidification