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Toughening additive manufactured Zr-based bulk metallic glass composites by martensite phase transformation

Journal of Materials science & Technology 2024年第3期170卷 95-102页

作者： Pengcheng Zhang Cheng Zhang Jie Pan Di Ouyang Lin Liu State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

Additive manufacturing technology based on laser powder bed fusion(LPBF)offers a novel approach for fabricating bulk metallic glass(BMG)products without restriction in size and ***,the BMGs prepared by LPBF usually suffered from less plasticity and poorer fracture toughness as compared to their cast counterparts due to partial crystallization in heat-affected zones(HAZs).Since crystallization in HAZs is hard to avoid completely in LPBF BMGs,it is desirable to design a suitable alloy system,in which only ductile crystalline phase,instead of brittle intermetallics,is formed in *** unique structure could effectively increase the toughness/plasticity of the LPBF *** achieve this goal,a quaternary BMG system with a composition of Zr_(47.5)Cu_(45.5)Al_(5)Co_(2)is adopted and subjected to *** is found that nearly a single phase of B_(2)-ZrCu is precipitated in HAZs,while a fully amorphous phase is formed in molten pools(MPs).This B_(2)phase reinforced BMG composite exhibits excellent mechanical properties with enhanced plasticity and ***,it is easy to modulate the mechanical properties by altering the amount of the B_(2)phase via adjusting the laser energy ***,the best combination of strength,plasticity,and notch toughness is obtained in the BMG composite containing 27.4%B_(2)phase and 72.6%amorphous phase,which exhibits yield strength(σ_(s))of 1423 MPa,plastic strain(ε_(p))of 4.65%,and notch toughness(K_(q))of 53.9 MPa m 1/***,a notable strain-hardening is also *** improvement of plasticity/toughness and appearance of strain-hardening behavior are mainly due to the martensite phase transformation from the B_(2)phase to the Cm phase during plastic deformation(i.e.,the phase transformation-induced plasticity effect).The current work provides a guide for making advanced BMGs and BMG composites by additive manufacturing.

关键词： Laser powder bed fusion Bulk metallic glass composites Phase transformation-induced plasticity Deformation mechanism

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The rapid densification behavior of powder metallurgy Ti alloys by induction heating sintering

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Journal of Materials science & Technology 2024年第14期181卷 152-164页

作者： Kejia Pan Xiaotao Liu Bao Wang Shuai Gao Shixing Wu Ning Li State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

Micropores are decisive to mechanical properties and thermal deformation capabilities of powder met-allurgy(P/M)Ti alloys sintered *** a result,achieving express densification is of prime im-portance and has attracted increasing attention *** heating owns the merits of high effi-ciency,short process,and low cost,and thus has huge potential to be used as a sintering approach for the fabrication of P/M Ti ***,the facilitated densification behavior associated with induction heating sintering remains unclear so *** address it,powder metallurgy Ti6Al4V is manufactured via induction heating sintering with which the underlying sintering mechanism is investigated *** is found that induction heating could generate a fully densified compact in a remarkably shortened time,demonstrating its superior sintering efficiency as compared with conventional resistance furnace *** finite element analysis reveals that the maximum current density during induction heating can reach 10^(6)A m^(–2)though the magnetic field strength is solely 0.02 T,leading to a slight tempera-ture difference of approximately 30℃between the interior and exterior of the ***,the rapid heating essentially starts at sharp corners of particles due to the potent current concentration ef-fect,which facilitates the cracking of the particle surface oxide film and thus enhances the direct contact between ***,the electromigration effect caused by induction current promotes the diffusion capability of elements,giving rise to expedited densification,alloying,and chemical *** work provides not only critical insight into the sintering mechanism of induction heating sintering but also significant guidance for low-cost powder metallurgy materials preparation.

关键词： Titanium alloy Powder metallurgy Induction heating sintering Radiation heating sintering Current field Simulation

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Deducing the internal interfaces of twisted multilayer graphene via moiré-regulated surface conductivity

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National science Review 2023年第8期10卷 194-202页

作者： Huan Wang Sen Wang Shuai Zhang Mengzhen Zhu Wengen Ouyang Qunyang Li Applied Mechanics Laboratory Department of Engineering Mechanics Tsinghua University Department of Engineering Mechanics School of Civil EngineeringWuhan University State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University State Key Laboratory of Tribology in Advanced Equipment Tsinghua University

The stacking state of atomic layers critically determines the physical properties of twisted van der Waals materials. Unfortunately, precise characterization of the stacked interfaces remains a great challenge as they are buried internally. With conductive atomic force microscopy, we show that the moiré superlattice structure formed at the embedded interfaces of small-angle twisted multilayer graphene(tMLG) can noticeably regulate surface conductivity even when the twisted interfaces are 10 atomic layers beneath the surface. Assisted by molecular dynamics(MD) simulations, a theoretical model is proposed to correlate surface conductivity with the sequential stacking state of the graphene layers of tMLG. The theoretical model is then employed to extract the complex structure of a tMLG sample with crystalline defects. Probing and visualizing the internal stacking structures of twisted layered materials is essential for understanding their unique physical properties, and our work offers a powerful tool for this via simple surface conductivity mapping.

关键词： twisted graphene electrical conductivity embedded interface atomic reconstruction moiré pattern

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High-temperature creep rupture behavior of dissimilar welded joints of RAFM steel and 316L steel by friction stir welding

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Journal of Iron and Steel Research International 2024年第10期31卷 2438-2447页

作者： Xin Ji Bin He Wei Guan Chen-xi Liu Hui-jun Li Lei Cui Yong-chang Liu Tianjin Key Laboratory of Advanced Joining Technology School of Materials Science and EngineeringTianjin UniversityTianjin300354China State Key Lab of Hydraulic Engineering Simulation and Safety School of Materials Science and EngineeringTianjin UniversityTianjin300350China

Creep rupture of the reduced activation ferritic/martensitic(RAFM)steel and 316L steel dissimilar joint by friction stir welding was *** creep rupture time of the dissimilar joint was 1941 h at 600℃/100 MPa and 120 h at 650℃/100 *** creep fracture occurred in heat affect zone(HAZ)of RAFM steel side where coarse Laves phase was *** formation and coarsening of the Laves phase particles in HAZ of RAFM steel side were the main reasons that caused the creep fracture of the dissimilar *** Laves phase particles nucleated adjacent to the large M_(23)C_(6) particles at the grain boundaries where W element segregated and grew fast during creep *** large Laves phase would deteriorate the pinning effect of M_(23)C_(6) carbides and weaken the solid solution strengthening ***,the size of the Laves phase in HAZ of RAFM steel side was bigger than that in stir zone of RAFM steel *** reasons explain the creep fracture in HAZ of RAFM steel side of dissimilar joint.

关键词： Creep behavior Dissimilar joint Friction stir welding Laves phase M23C6 carbide

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Hydrodynamic Performance of An Integrated System of Breakwater and A Multi-Chamber OWC Wave Energy Converter

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China Ocean engineering 2024年第4期38卷 543-556页

作者： NING De-zhi ZHANG Xiang-yu WANG Rong-quan ZHAO Ming State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China Dalian Key Laboratory of Offshore Renewable Energy Dalian University of TechnologyDalian 116024China School of Computing Engineering and MathematicsUniversity of Western SydneyPenrith NSW 2751Australia

A multi-chamber oscillating water column wave energy converter(OWC-WEC)integrated to a breakwater is *** hydrodynamic characteristics of the device are analyzed using an analytical model based on the linear potential flow theory.A pneumatic model is employed to investigate the relationship between the air mass flux in the chamber and the turbine *** effects of chamber width,wall draft and wall thickness on the hydrodynamic performance of a dual-chamber OWC-WEC are *** results demonstrate that the device,with a smaller front wall draft and a wider rear chamber exhibits a broader effective frequency *** device with a chamber-width-ratio of 1:3 performs better in terms of power ***,results from the analysis of a triplechamber OWC-WEC demonstrate that reducing the front chamber width and increasing the rearward chamber width can improve the total performance of the *** the number of chambers from 1 to 2 or 3 can widen the effective frequency bandwidth.

关键词： oscillating water column power extraction efficiency potential flow theory wave energy converter multi-chamber

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Emerging applicability of two-dimensional boron for energy catalysis

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Journal of Zhejiang University-science A(Applied Physics & engineering) 2024年第10期25卷 877-888页

作者： Dake ZHANG Chengcheng ZHANG Shenghua WANG Wei SUN State Key Laboratory of Silicon Materials and Advanced Semiconductor Materials School of Materials Science and EngineeringZhejiang UniversityHangzhou 310027China

Due to their unique physical and chemical properties,two-dimensional(2D)boron nanosheets have received tremendous research attention and demonstrated substantial value in electronic devices,biomedicine,and energy *** the preparation of boron nanosheets,compared with the bottom-up synthesis predominantly employed for electronics,the top-down synthesis route offers more facile and scalable *** this mini-review,we mainly discuss the recent advances in the synthesis of boron nanosheets using the top-down strategy and the relevant applications in energy ***,inspired by our recent works on the novel applications of 2D silicon,we put forward prospects for designing boron nanosheets,providing insights into developing viable techniques for high-performance heterogeneous catalysis.

关键词： Two-dimensional(2D)boron nanosheets Top-down method Catalytic applications

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Efficient design of non-shrinkage xerogels via metal coordination and triazine steric hindrance for activated carbon xerogels with interconnected hierarchical structure

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材料科学技术（英文版） 2025年第3期206卷 153-163页

作者： Kunming Li Xuepeng Ni Dong Li Jiaoli Hu Huifang Chen Yonggen Lu Anqi Ju State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai 201620PR China State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai 201620PR China Key Laboratory of High-Performance Fibers & Products Ministry of EducationDonghua UniversityShanghai 201620PR China

Designing xerogels at the molecular level to overcome volume shrinkage is a promising strategy for car-bon xerogels with desirable structure and ***,we design a xerogel with non-shrinkage by introducing ZnCl2 into resorcinol-melamine-formaldehyde *** gel network consist-ing of micrometer pores and large particles(0.26-1.35 μm)is constructed by the coordination of Zn2+with oxygen/nitrogen-containing groups,which is attributed to the structural support of the rigid triazine skeleton with large steric ***,the reinforced gel network possesses enough strength to withstand capillary forces during atmospheric drying,and special drying and solvent exchange are *** xerogels show non-shrinkage and a short preparation time of 24 *** resulted activated carbon xerogels with interconnected hierarchically micro-meso-macropores exhibit an optimal specific surface area of 1520 m2/g(through xerogels pyrolysis and the pore-forming of ZnCl2),high adsorption(methylene blue,I-,Cu2+,etc.),and repeated adsorption *** work provides novel thought for porous nanomaterials with non-shrinkage and desirable structures in adsorption and energy storage.

关键词： Xerogels Non-shrinkage Resorcinol-melamine-formaldehyde Zinc chloride Activated carbon xerogels

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Self-assembled aerogel sheet electrodes of thermocells for low-grade heat harvest

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science China Chemistry 2024年第5期67卷 1672-1679页

作者： Ziwei Mo Shouhao Wei Daibin Xie Kaihua Zhu Hongxiong Li Xin Lu Lirong Liang Chunyu Du Zhuoxin Liu Guangming Chen College of Materials Science and Engineering Shenzhen UniversityShenzhen 518055China State Key Laboratory of Polymer Materials Engineering Sichuan UniversityChengdu 610065China

Efficiently harvesting low-grade heat is crucial for sustainable energy management. Thermocells(TECs), inducing heat-toelectricity conversion via the thermogalvanic effect, have thus drawn tremendous attention in recent years. This study introduces a self-assembly approach for fabricating aerogel sheet electrodes(ASEs) tailored for TECs. The crafted ASEs retain a remarkable porous architecture with approximately 95% porosity, even with their slimmed-down thickness. Results reveal that the electrode composition has minimal influence on the thermopower of TECs. Notably, the porous ASE with tunned composition demonstrates an optimal effective surface area for the thermogalvanic effect, resulting in enhanced output current density. This balances the desirable traits of electrode compactness with abundant redox active sites, positioning it favorably against conventional bulky electrode designs. The TECs utilizing the optimized ASE achieve a peak output power of 22.10 μW cm^(-2)under a temperature difference of 30 K. Furthermore, a tubular TEC device is readily assembled and specially designed for harvesting heat energy from hot fluids. These findings underscore the potential of composite electrodes in the realm of low-grade heat harvest, paving the way for broader applications in sustainable energy solutions.

关键词： thermocells low-grade heat harvest energy conversion composite electrodes

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A functional hydrogel electrolyte doped with graphene oxide enabling ultra-long lifespan zinc metal batteries by inducing oriented deposition

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Journal of Materials science & Technology 2024年第24期191卷 209-219页

作者： Congyuan Wang Jingjing Jiao Jiaxuan Dai Lu Yu Qibing Chen Xiangyu Xie Xiaoping Yang Gang Sui State Key Laboratory of Organic-Inorganic Composites College of Materials Science and EngineeringBeijing University of Chemical TechnologyBeijing 100029China

The progress of zinc(Zn)metal batteries(ZMBs)is greatly limited by poor cycling stability because of the mutual restrictions of dendrite growth,corrosion reactions,and *** this work,an ultralong lifespan(~7800 h),dendrite-free Zn metal anode is enabled via fabricating a functional hydrogel electrolyte out of polyacrylamide/graphene oxide(GO)/agarose(PGA)with a multifully cross-linked *** synergetic integration of GO nanosheets and double-network structure endows the PGA hydrogel electrolyte with high ionic conductivity and excellent mechanical *** importantly,the abundant hydrophilic groups and stable three-dimensional cross-linked network of PGA electrolyte effectively constrain Zn^(2+)diffusion laterally along the Zn surface,which simultaneously prohibits waterinduced corrosion and thus significantly enhances Zn anode *** theoretical simulations and experiments reveal that the PGA electrolyte is capable of optimizing de-solvation kinetics and harmonizing Zn^(2+)flux at the electrolyte-electrode interface,ensuring uniform Zn^(2+)***,an ultra-long lifespan of 7800 h is achieved in the symmetric cell with the PGA *** at a high Zn utilization of 42.7%,it still delivers stable cycling over 1100 *** work provides a practical and beneficial approach to dramatically extending the lifespan of the Zn anode and thus achieving high-performance ZMBs.

关键词： Zinc metal anode Hydrogel electrolyte Graphene oxide Double-network structure Ultra-long lifespan

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SOLVING OPTIMIZATION PROBLEMS OVER THE STIEFEL MANIFOLD BY SMOOTH EXACT PENALTY FUNCTIONS

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Journal of Computational Mathematics 2024年第5期42卷 1246-1276页

作者： Nachuan Xiao Xin Liu The Institute of Operations Research and Analytics National University of SingaporeSingapore State Key Laboratory of Scientific and Engineering Computing Academy of Mathematics and Systems ScienceChinese Academy of Sciencesand University of Chinese Academy of SciencesChina

In this paper,we present a novel penalty model called ExPen for optimization over the Stiefel *** from existing penalty functions for orthogonality constraints,ExPen adopts a smooth penalty function without using any first-order derivative of the objective *** show that all the first-order stationary points of ExPen with a sufficiently large penalty parameter are either feasible,namely,are the first-order stationary points of the original optimization problem,or far from the Stiefel ***,the original problem and ExPen share the same second-order stationary ***,the exact gradient and Hessian of ExPen are easy to *** a consequence,abundant algorithm resources in unconstrained optimization can be applied straightforwardly to solve ExPen.

关键词： Orthogonality constraint Stiefel manifold Penalty function

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