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Origin of the near-room temperature resistance transition in lutetium with H2/n2 gas mixture under high pressure

national Science Review 2024年第7期11卷 26-32页

作者： Di Peng Qiaoshi zeng Fujun Lan Zhenfang Xing Zhidan zeng Xiaoxing Ke Yang Ding Ho-kwang Mao Key Laboratory of Materials Physics Institute of Solid State Physics Hefei Institutes of Physical Science(HFIPS)Chinese Academy of Sciences Science Island Branch Graduate School of University of Science and Technology of China Center for High Pressure Science and Technology Advanced Research Shanghai Key Laboratory of Material Frontiers Research in Extreme Environments(MFree) Shanghai Advanced Research in Physical Sciences(SHARPS) State Key Laboratory of Superhard Materials Institute of PhysicsJilin University College of Materials Science&Engineering Beijing University of Technology

The recent report of room-temperature superconductivity at near-ambient pressure in nitrogen-doped lutetium hydride（Lu-H-n） by Dasenbrock-Gammon et al. [nature 615, 244–250（2023）] has attracted tremendous attention due to its anticipated great impact on technology. However, the results could not be independently reproduced by other groups worldwide in follow-up studies, which elicited intense controversy. Here, we develop a reliable experimental protocol to minimize the extensively concerned extrinsic influences on the sample by starting the reaction from pure lutetium loaded with an H2/n2gas mixture in a diamond anvil cell under different pressures and temperatures and simultaneously monitoring the entire chemical reaction process using in situ four-probe resistance measurements. Therefore, we could repeatedly reproduce the near-room temperature upsurge of electrical resistance at a relatively early stage of the chemical reaction. However, the mechanism is suggested to be a metal-to-semiconductor/insulator transition associated with the structural modulation in the non-stoichiometric Lu-H-n, rather than superconductivity.

关键词： superconductivity high pressure lutetium hydride resistance transition metal-to-semiconductor/insulator transition

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Stable graphene oxide-based lyotropic liquid crystals for interfacial lubrication

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Friction 2024年第5期12卷 954-967页

作者： Yumei GUO Hanglin LI Jiusheng LI Xiangqiong zeng Laboratory for Advanced Lubricating Materials Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai201210China University of Chinese Academy of Sciences Beijing100049China

Lyotropic liquid crystals have lubricating properties due to their ordered assembly and fluidity,whose mesogens are often characterized by amphiphilic *** the attention that graphene oxide(GO)has been studied as a novel amphiphilic lyotropic mesogen this decade,and GO applied as a lubrication additive has been demonstrated in both oil and water-based systems,little research reveals the interfacial lubrication of GO liquid crystals *** work reports that GO aqueous dispersion can form lyotropic liquid crystals above a specific critical concentration of 5.00 mg/mL,providing a form of stable water-based lubricant,which can keep stable for several months and can reduce friction by 37.3%and wear by 25.24%.The liquid crystal phase was verified by polarizing microscope and synchrotron radiation small-angle X-ray scattering,and its rheological properties and viscoelasticity were studied by interfacial *** formation of lyotropic liquid crystals can enhance the stability of GO aqueous dispersions at high density,simultaneously ensuring friction decrease and anti-wear *** is attributed to the stable nematic network by the ordered GO *** ordered assembly structure bears vertical shear force,therefore,reducing the *** is also assumed that the wide lateral size of graphene oxide promotes the nematic phase thus smoothes the graphene oxide film composed spontaneously under the coincidence of lamellar liquid crystal and 2D layered *** this work,the interlayer lubrication of GO was optimized,and the problem of GO dispersion sedimentation was solved by *** range of interfacial lubrication of GO aqueous dispersion has been expanded and the synergistic effect is conducive to the environmentally friendly lubricants.

关键词： lyotropic liquid crystal graphene oxide aqueous lubrication tribological behavior

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Mass transfer in heap leaching of weathered crust elution deposited rare earth ore with Al_(2)(SO_(4))_(3) solution

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Journal of Rare Earths 2024年第6期42卷 1175-1181,I0007页

作者： Jingqun Yin Dedong zeng Jun Tian Yaqing Weng Institute of Applied Chemistry Jiangxi Academy of SciencesNanchang330096China School of Chemistry and Chemical Engineering Nanchang UniversityNanchang330031China

In order to increase efficiency and avoid nH^(4+)-n pollution in the leaching process of weathered crust elution-deposited rare earth ores,the mass transfer in heap leaching with Al_(2)(SO_(4))_(3) solution was simulated with column elution and experimentally *** results indicate that the leaching yield is also up to 99%for leaching with aluminum sulfate instead of ammonium *** optimal flow rate is 60 mL/h,the height equivalent to a theoretical plate(HETP)is 1.29 mm *** peak value position of RE^(3+)is 60 mL/h,Fe^(3+)is 100 mL/h,however,Al^(3+)is 150 mL/h,and the heap leaching process has kinetic separation effect.

关键词： Raree arths Mass transfer Process optimization Heapleaching Weathered crust elution-deposited rare earth ore

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Second-order error analysis of the averaged L1 scheme L1 for time-fractional initial-value and subdiffusion problems

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Science China Mathematics 2024年第7期67卷 1641-1664页

作者： Jinye Shen Fanhai zeng Martin Stynes School of Mathematics Southwestern University of Finance and EconomicsChengdu611130China School of Mathematics Shandong UniversityJinan250100China Applied and Computational Mathematics Division Beijing Computational Science Research CenterBeijing100193China

Fractional initial-value problems(IVPs) and time-fractional initial-boundary value problems(IBVPs), each with a Caputo temporal derivative of order α ∈(0, 1), are considered. An averaged variant of the well-known L1 scheme is proved to be O(n^(-2)) convergent for IVPs on suitably graded meshes with n points, thereby improving the O(n^(-(2-α))) convergence rate of the standard L1 scheme. The analysis relies on a delicate decomposition of the temporal truncation error that yields a sharp dependence of the order of convergence on the degree of mesh grading used. This averaged L1 scheme can be combined with a finite difference or piecewise linear finite element discretization in space for IBVPs, and under a restriction on the temporal mesh width, one gets again O(n^(-2)) convergence in time, together with O(h^(2)) convergence in space,where h is the spatial mesh width. numerical experiments support our results.

关键词： time-fractional subdiffusion averaged L1 scheme

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Strain-tuned electronic and valley-related properties in Janus monolayers of SWSiX_(2)(X=n,P,As)

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Chinese Physics B 2024年第9期33卷 487-492页

作者： Yunxi Qi Jun Zhao Hui zeng new Energy Technology Engineering Laboratory of Jiangsu Province&School of Science Nanjing University of Posts and TelecommunicationsNanjing 210023China School of Microelectronics Nanjing University of Science and TechnologyNanjing 210094China

Exploring novel two-dimensional(2D)valleytronic materials has an essential impact on the design of spintronic and valleytronic *** first principles calculation results reveal that the Janus SWSiX_(2)(X=n,P,As)monolayer has excellent dynamical and thermal *** to strong spin–orbit coupling(SOC),the SWSiX_(2)monolayer exhibits a valence band spin splitting of up to 0.49 eV,making it promising 2D semiconductor for valleytronic *** opposite Berry curvatures and optical selection rules lead to the coexistence of valley and spin Hall effects in the SWSiX2 ***,the optical transition energies can be remarkably modulated by the in-plane *** tensile(compressive)in-plane strains can achieve spin flipping in the SWSin2 monolayer,and induce both SWSiP_(2)and SWSiAs_(2)monolayers transit from semiconductor to *** research provides new 2D semiconductor candidates for designing high-performance valleytronic devices.

关键词： first-principles calculations two-dimensional valleytronic spintronic

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A new class of generalized quasi-variational inequalities with applications to Oseen problems under nonsmooth boundary conditions

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Science China Mathematics 2024年第2期67卷 315-338页

作者： Shengda zeng Akhtar A.Khan Stanislaw Migórski Guangxi Colleges and Universities Key Laboratory of Complex System Optimization and Big Data Processing Yulin Normal UniversityYulin 537000China Faculty of Mathematics and Computer Science Jagiellonian University in Krak´owKrak´ow 30348Poland Center for Applied and Computational Mathematics School of Mathematical SciencesRochester Institute of TechnologyRochesterNY 14623USA College of Sciences Beibu Gulf UniversityQinzhou 535000China

In this paper, we study a generalized quasi-variational inequality (GQVI for short) with twomultivalued operators and two bifunctions in a Banach space setting. A coupling of the Tychonov fixedpoint principle and the Katutani-Ky Fan theorem for multivalued maps is employed to prove a new existencetheorem for the GQVI. We also study a nonlinear optimal control problem driven by the GQVI and givesufficient conditions ensuring the existence of an optimal control. Finally, we illustrate the applicability of thetheoretical results in the study of a complicated Oseen problem for non-newtonian fluids with a nonmonotone andmultivalued slip boundary condition (i.e., a generalized friction constitutive law), a generalized leak boundarycondition, a unilateral contact condition of Signorini’s type and an implicit obstacle effect, in which themultivalued slip boundary condition is described by the generalized Clarke subgradient, and the leak boundarycondition is formulated by the convex subdifferential operator for a convex superpotential.

关键词： generalized quasi-variational inequality existence theorem optimal control Kakutani-Ky Fan theorem Oseen problem non-newtonian fluid nonmonotone slip boundary condition

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Fe-Induced Electronic Transfer and Structural Evolution of Lotus Pod-Like ConiFePx@P,n-C Heterostructure for Sustainable Oxygen Evolution

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Energy & Environmental Materials 2024年第3期7卷 186-193页

作者： xiaoj.n zeng Qingqing Zhang Chulong Jin Hui Huang Yanfeng Gao Advanced Ceramic Materials Research Institute School of Materials Science and EngineeringJingdezhen Ceramic University Singapore Institute of Technology School of Materials Science and Engineering Shanghai University

Transition metal phosphides with metallic properties are a promising candidate for electrocatalytic water oxidation,and developing highly active and stable metal phosphide-based oxygen evolution reaction catalysts is still ***,we present a facile ion exchange and phosphating processes to transform intestine-like ConiPx@P,n-C into lotus pod-like ConiFePx@P,n-C heterostructure in which numerous P,n-codoped carboncoated ConiFePxnanoparticles tightly anchors on the 2D carbon ***,the as-prepared ConiFePx@P,n-C enables a core-shell structure,high specific surface area,and hierarchical pore structure,which present abundant heterointerfaces and fully exposed active ***,the incorporation of Fe can also induce electron transfer in ConiPx@P,IM-C,thereby promoting the oxygen evolution ***,ConiFePx@P,IM-C delivers a low overpotential of 278 mV （vs RHE） at a current density of10 mA cm-1and inherits excellent long-term stability with no observable current density decay after 30 h of chronoamperometry *** work not only highlights heteroatom induction to tune the electronic structure but also provides a facile approach for developing advanced and stable oxygen evolution reaction electrocatalysts with abundant heterointerfaces.

关键词： electronic transfer Fe exchange multi-metal phosphides OER electrocatalysts structural evolution

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Achieving near-infrared-light-mediated switchable friction regulation on MXene-based double network hydrogels

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Friction 2024年第1期12卷 39-51页

作者： Pengxi WU Cheng zeng Jinglun GUO Guoqiang LIU Feng ZHOU Weimin LIU Center of Advanced Lubrication and Sealing Materials State Key Laboratory of Solidification ProcessingNorthwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China

MXene possesses great potential in enriching the functionalities of hydrogels due to its unique metallic conductivity,high aspect ratio,near-infrared light(nIR light)responsiveness,and wide tunability,however,the poor compatibility of MXene with hydrogels limits further *** this work,we report a uniformly dispersed MXene-functionalized poly-n-isopropylacrylamide(PnIPAM)/poly-2-acrylamido-2-methyl-1-propanesulfonic acid(PAMPS)double network hydrogel(M–Dn hydrogel)that can achieve switchable friction regulation by using the nIR *** dispersity of MXene in hydrogels was significantly improved by incorporating the chitosan(CS)*** M–Dn hydrogel showed much low coefficient of friction(COF)at 25℃ due to the presence of hydration layer on hydrogel *** illuminating with the nIR light,M–Dn hydrogel with good photothermal effect rapidly raised the temperature to above the lower critical solution temperature(LCST),which led to an obvious increase of surface COF owing to the destruction of the hydration *** addition,M–Dn friction control hydrogel showed good recyclability and controllability by tuning“on-off”of the nIR *** work highlights the construction of functional MXene hydrogels for intelligent lubrication,which provides insight for interface sensing,controlled transmission,and flexible robotic arms.

关键词： MXene dispersion photothermal hydrogel near-infrared(nIR)light friction modulation

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Simplified quantitative analysis method and its application in the insitu synthesized copper-based azide chips

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Defence Technology（防务技术） 2024年第2期32卷 309-316页

作者： Jie Ren Yunfeng Li Mingyu Li Xingyu Wu Jiabao Wang Qingxuan zeng State Key Laboratory of Explosion and Technology Beijing Institute of TechnologyBeijing 100081China

Copper-based azide(Cu(n_(3))2 or Cun_(3),CA)chips synthesized by in-situ azide reaction and utilized in miniaturized explosive systems has become a hot research topic in recent ***,the advantages of in-situ synthesis method,including small size and low dosage,bring about difficulties in quantitative analysis and differences in ignition capabilities of CA *** aim of present work is to develop a simplified quantitative analysis method for accurate and safe analysis of components in CA chips to evaluate and investigate the corresponding ignition *** this work,Cu(n_(3))2 and Cun_(3)components in CA chips were separated through dissolution and distillation by utilizing the difference in solubility and corresponding content was obtained by measuring n_(3)-concentration through *** spectrophotometry method was optimized by studying influencing factors and the recovery rate of different separation methods was studied,ensuring the accuracy and reproducibility of test *** optimized method is linear in range from 1.0-25.0 mg/L,with a correlation coefficient R^(2)=0.9998,which meets the requirements of CA chips with a milligram-level content *** with the existing ICP method,component analysis results of CA chips obtained by spectrophotometry are closer to real component content in samples and have satisfactory ***,as its application in miniaturized explosive systems,the ignition ability of CA chips with different component contents for direct ink writing CL-20 and the corresponding mechanism was *** study provided a basis and idea for the design and performance evaluation of CA chips in miniaturized explosive systems.

关键词： Copper-based azide chips Spectrophotometry Separation method Quantitative analysis Ignition ability

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Tribological properties of low-temperature time-dependent pretreated graphite for mechanical seal pairs in high-speed turbopump

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Friction 2024年第2期12卷 305-318页

作者： Yangyang ZHAO Guoyuan ZHAnG Junqian WAnG He WAnG Weigang ZHAO Qunfeng zeng School of Mechano-Electronic Engineering Xidian UniversityXi’an 710071China Xi’an Aerospace Propulsion Institute Xi’an 710071China Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System Xi’an Jiaotong UniversityXi’an 710049China

The friction coefficient and wear rate of pretreated graphite with liquid nitrogen were obtained by using a ball-on-disk tester,and the wear of GCr15–graphite seal pairs with the low-temperature time-dependent pretreatment was discussed by comparing the wear *** results show that liquid nitrogen pretreatment can affect the hardness and interlayer spacing of *** range of the friction coefficients of pretreated graphite changes from 0.17 to *** the increase of liquid nitrogen pretreatment time,the wear mechanism of graphite would change from dominated three-body wear to adhesion *** experimental results of the mechanical seal with liquid nitrogen pretreatment show that the wear rate of stator is less than 0.00165 mm^(3)·n^(−1)·m^(−1),and the graphite shows a good low-temperature compatibility.

关键词： graphite low-temperature pretreatment mechanical seal friction and wear

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