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Bio-inspired tetracarbene compounds as a new family of energy saving catalysts

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journal of Energy Chemistry 2023年第4期79卷 559-561页

作者： Bo Zhang Fritz E.Kühn CAS Key Laboratory of Science and Technology on Applied Catalysis Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina' University of Chinese Academy of Science Beijing 100049China Molecular Catalysis Catalysis Research Center and Department of ChemistrySchool of Natural SciencesTechnical University of MunichLichtenbergstr 485748 Garching bei MünchenGermany

Efficient use of energy is a pressing *** of chemical processes is currently an important target for energy *** chemical processes are independent of pathways with respect to the final energy output or consumption,the application of catalysts can reduce involved activation energies considerably and therefore save large amounts of energy.

关键词： Catalysis Iron Carbenes Multidentate ligands

Compositional complexity dependence of dislocation density and mechanical properties in high entropy alloy systems

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Progress in Natural Science:Materials International 2020年第4期30卷 545-551页

作者： P.Thirathipviwat G.Song j.Bednarcik U.Kühn T.Gemming K.Nielsch j.Han Leibniz Institute of Solid State and Materials Research (IFW Dresden) Frontier Research Center for Applied Atomic Sciences Ibaraki University Division of Advanced Materials Engineering and Institute for rare metals Kongju National University Institute of Physic Pavol Jozef Safarik University in Ko?ice Deutsches Elektronen-Synchrotron (DESY) Institute of Materials Science Technische Universit?t Dresden Institute of Applied Physics Technische Universit?t Dresden Korea Institute for Rare Metals Korea Institute of Industrial Technology (KITECH)

This study focuses on a quantitative analysis of dislocation accumulation after cold plastic deformation and mechanical properties of Fe Ni Co Cr Mn and Ti Nb Hf Ta Zr high entropy alloys(HEAs) which are single phase fcc and bcc solid solutions, respectively. In order to study the role of compositional complexity from unary to quinary compositions on dislocation accumulation and mechanical properties after plastic deformation, the single solid solution phase forming sub-alloys of the two HEAs were investigated. All studied samples revealed a large plastic deformability under cold-rotary swaging process by 85–90% area reduction without intermediate annealing. The dislocation density of all studied samples, determined by Williamson-Hall method on synchrotron X-ray diffraction patterns, were between 1014-1015m-2dependent on the alloy composition. The level of dislocation density after plastic deformation is not only affected by the number of constituent element but the lattice distortion and intrinsic properties in terms of stacking fault energy, modulus misfit, and melting point also impact the dislocation storage. The level of dislocation density determines the level of mechanical properties because of a resistance to dislocation motions. The hardness and yield compressive strength of the studied samples are proportional to the level of dislocation density.

关键词： High entropy alloys Dislocation density Synchrotron XRD Mechanical properties

Hydromechanical behaviors of andesite under different stress states during fluid injection

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journal of Rock Mechanics and Geotechnical Engineering 2021年第4期13卷 727-744页

作者： Miao He Qi Li Xiaying Li Liang Xu Michael Kühn State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China Fluid Systems Modelling Section GFZ German Research Centre for GeosciencesPotsdamGermany Institute of Earth and Environmental Science University of PotsdamPotsdamGermany

Water reinjection into the formation is an indispensable operation in many energy engineering *** operation involves a complex hydromechanical(HM)coupling process and sometimes even causes unpredictable disasters,such as induced *** is acknowledged that the relative magnitude and direction of the principal stresses significantly influence the HM behaviors of rocks during ***,due to the limitations of current testing techniques,it is still difficult to comprehensively conduct laboratory injection tests under various stress conditions,such as in triaxial extension stress *** this end,a numerical study of HM changes in rocks during injection under different stress states is *** this model,the saturated rock is first loaded to the target stress state under drainage conditions,and then the stress state is maintained and water is injected from the top to simulate the formation injection *** attention is given to the difference in HM changes under triaxial compression and extension *** includes the differences in the pore pressure propagation,mean effective stress,volumetric strain,and stress-induced *** numerical results demonstrate that the differential stress will significantly affect the HM behaviors of rocks,but the degree of influence is different under the two triaxial stress *** HM changes caused by the triaxial compression stress states are generally greater than those of extension,but the differences decrease with increasing differential stress,indicating that the increase in the differential stress will weaken the impact of the stress state on the HM *** addition,the shear failure potential of fracture planes with various inclination angles is analyzed and summarized under different stress *** is recommended that engineers could design suitable injection schemes according to different tectonic stress fields versus fault occurrence to reduce the risk of

关键词： Water reinjection Stress state Hydromechanical(HM)coupling Injection-induced seismicity Numerical modeling

Laser additive manufactured high-performance Fe-based composites with unique strengthening structure

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journal of Materials Science & Technology 2021年第30期89卷 242-252页

作者： Hongyu Chen Dongdong Gu Liang Deng Tiwen Lu Uta Kühn Konrad Kosiba College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China jiangsu Provincial Engineering Laboratory for Laser Additive Manufacturing of High-Performance Metallic Components Nanjing University of Aeronautics and AstronauticsNanjing 210016China Leibniz IFW Dresden Institute for Complex MaterialsP.O.Box 270116D-01069 DresdenGermany

Steel matrix composites(SMCs),reinforced by ceramic particles,have received a consistent attention in recent *** conventional methods to prepare SMCs is generally challenging,and the mechanical properties of conventionally fabricated SMCs are *** this study,we successfully fabricated highperformance SMCs by laser powder bed fusion(LPBF)of a composite powder consisting of Fe-based alloy powder and submicron-sized WC *** effect of laser energy density on the phase formation,microstructural evolution,overall density and resulting mechanical properties of LPBF-fabricated composites was *** present results show that a novel Fe_(2)W_(4)C carbidic network precipitates in the solidified microstructure entailing segregations along the boundaries of cellular *** presence of this carbidic network hampers the growth of sub-grains even at elevated temperatures,and hence,stabilizes the grain size though prepared at a broad range of different energy *** exact distribution of the Fe_(2)W_(4)C carbides depends on the employed laser energy densities,as for instance they are more uniformly distributed at higher energy *** density of LPBF samples reaches the maximum value of 99.4%at 150 j/mm^(3).In this parameter set,high microhardness of~753 HV,compression strength of~3350 MPa and fracture strain of~24.4%are *** enhanced mechanical properties are ascribed to less metallurgical defects,higher volume fraction of the martensitic phase and increasing pile-up dislocations resulting from the pinning effect by Fe_(2)W_(4)C carbide.

关键词： Laser additive manufacturing Laser powder bed fusion Steel matrix composite Microstructures Mechanical properties

Harnessing coherence of area decomposition and semantic shared spaces for task allocation in a robotic fleet

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Information Processing in Agriculture 2014年第1期1卷 23-33页

作者： Domagoj Drenjanac Slobodanka Dana Kathrin Tomic Lukas Klausner Eva Kühn The Telecommunications Research Center Vienna(FTW) Donau-City-Strasse 11220 ViennaAustria Institute of Computer Languages Vienna University of TechnologyArgentinierstrasse 81040 ViennaAustria

Task allocation is a fundamental problem in multi-robot systems where heterogeneous robots cooperate to perform a complex mission.A general requirement in a task allocation algorithm is to find an optimal set of robots to execute a certain *** paper presents the work that harnesses an area decomposition algorithm,and a space-based middleware to facilitate task allocation process in unstructured and dynamic *** reduce spatial interference between robots,area decomposition algorithm divides a working area into cells which are then dynamically assigned to *** addition,coordination and collaboration among distributed robots are realized through a space-based *** this purpose,the space-based middleware is extended with a semantic model of robot capabilities to improve task selection in terms of flexibility,scalability,and reduced communication overhead during task *** this way a framework which exploits the synergy of area decomposition and semantically enriched space-based approach is *** conducted performance tests in a specific precision agriculture use case focusing on the utilization of a robotic fleet for weed control introduced in the European Project RHEA–Robot Fleets for Highly Effective Agriculture and Forestry Management.

关键词： Task allocation Area decomposition Space-based computing Semantics Robotic fleet

Microstructural Evolution and Mechanical Behaviour of Metastable Cu-Zr-Co Alloys

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journal of Materials Science & Technology 2014年第6期30卷 584-589页

作者： S.Pauly K.Kosiba P.Gargarella B.Escher K.K.Song G.Wang U.Kühn j.Eckert IFW Dresden Institut für Komplexe Materialien HelmholtzstraBe 20D-01069 Dresden Germany Laboratory for Microstructures Shanghai University TU Dresden Institut für WerkstoffwissenschaftD-01062 Dresden Germany

Three different Cu-Zr-Co alloys, namely Cu40Zr37.5Co22.5, Cu42.5Zr45Co12.5 and Cu49Zr49Co2, were obtained by rapid cooling. The microstructure and phase formation of as-cast rods with diameters of 2 mm are compared with those of the respective ingots. An increasing Co content stabilises the B2 CuZr phase and leads to the precipitation of a ternary Cu-Zr-Co phase. The variation of the cooling rate affects the size of the B2 dendrites as well as the volume fraction and the morphology of the interdendritic phases. The mechanical properties were determined in compression and all alloys show a certain plastic deformability despite the presence of several binary and ternary intermetallic phases. The deformation mechanisms are discussed on the basis of the microstructures and the constituent phases.

关键词： Bulk metallic glasses Microstructural evolution Mechanical behaviour

Glass-forming ability, phase formation and mechanical properties of glass-forming Cu-Hf-Zr alloys

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Progress in Natural Science:Materials International 2019年第5期29卷 576-581页

作者： K.Kosiba Kaikai Song U.Kühn Gang Wang S.Pauly Leibniz IFW Dresden Institute for Complex Materials School of Mechanical Electrical & Information Engineering Shandong University (Weihai) Laboratory for Microstructures Institute of Materials Shanghai University

The influence of Hf additions on the glass-forming ability（GFA）,phase formation and mechanical properties of Cu;Hf;Zr;（x=2,5,10,20 at.%）alloys has been systematically *** report on a distinct correlation between phase formation and GFA of Cu;Zr;-based *** additions of Hf reduce the thermal stability of the high-temperature B2Cu（Hf,Zr）phase,while the thermal stability of the corresponding undercooled melt is *** GFA of these alloy series gradually raises up to 10 at.%Hf,whereas at 20 at.%Hf,the GFA is drastically lowered,since the B2Cu（Hf,Zr）phase becomes unstable and the precipitation of the lowtemperature equilibrium phases is *** interrelation determines the microstructure and results in the formation of Cu-Hf-Zr-based bulk metallic glass *** composites not only show appreciable macroscopic plastic strain,but also high yield strength.

关键词： Metallic glasses Glass-forming ability Composites Continuous cooling transformation (CCT) diagram Mechanical properties

Plastic deformation of a Zr-based bulk metallic glass fabricated by selective laser melting

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journal of Materials Science & Technology 2021年第1期60卷 139-146页

作者： L.Deng K.Kosiba R.Limbach L.Wondraczek U.Kühn S.Pauly IFW Dresden Institute for Complex MaterialsHelmholtzstraße 20D-01069DresdenGermany Otto Schott Institute of Materials Research University of JenaFraunhoferstraße 6D-07743JenaGermany University of Applied Sciences Aschaffenburg Würzburger Straße 45D-63743AschaffenburgGermany

Fully amorphous Zr_(52.5)Cu_(17.9)Ni_(14.6)Al_(10)Ti_(5) bulk metallic glass(BMG) samples with a relative density exceeding 98% were fabricated via selective laser melting(SLM).High fracture stresses of around1700 MPa and a reproducible plastic strain of about 0.5% were obtained for cylindrical SLM *** analysis of the observed serrations during compressive loading implies that the shear-band dynamics in the additively manufactured samples distinctly differ from those of the as-cast *** phenomenon appears to originate from the presence of uniformly dispersed spherical pores as well as from the more pronounced heterogeneity of the glass itself as revealed by instrumented *** these heterogeneities,the shear bands are straight and form in the plane of maximum shear *** manufacturing,hence,might not only allow for producing large BMG samples with complex geometries but also for manipulating their deformation behaviour through tailoring porosity and structural heterogeneity.

关键词： Powder bed fusion Selective laser melting Bulk metallic glass Serrated flow Heterogeneity

CuZr-based bulk metallic glass and glass matrix composites fabricated by selective laser melting

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journal of Materials Science & Technology 2021年第22期81卷 139-150页

作者： Liang Deng Long Zhang Konrad Kosiba RenéLimbach Lothar Wondraczek Gang Wang Dongdong Gu Uta Kühn Simon Pauly Leibniz IFW Dresden Institute for Complex MaterialsHelmholtzstraße 20D-01069DresdenGermany Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang110016China Otto Schott Institute of Materials Research University of JenaFraunhoferstraße 6D-07743 JenaGermany Laboratory for Microstructure Institute of MaterialsShanghai UniversityShanghai200444China College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing210016China University of Applied Sciences Aschaffenburg Würzburger Straße 45D-63743AschaffenburgGermany

Monolithic bulk metallic glass and glass matrix composites with a relative density above 98%were produced by processing Cu_(46)Zr_(46)Al_(8)(at.%)via selective laser melting(SLM).Their microstructures and mechanical properties were systematically examined.B2 CuZr nanocrystals(30-100 nm in diameter)are uniformly dispersed in the glassy matrix when SLM is conducted at an intermediate energy *** B2 CuZr nanocrystals nucleate the oxygen-stabilized big cube phase during a remelting *** presence of these nanocrystals increases the structural heterogeneity as indirectly revealed by mircrohardness and nanoindentation *** corresponding maps in combination with calorimetric data indicate that the glassy phase is altered by the processing *** the formation of crystals and a high overall free volume content,all additively manufactured samples fail at lower stress than the as-cast glass and without any plastic *** inherent brittleness is attributed to the presence of relatively large pores and the increased oxygen content after selective laser melting.

关键词： Selective laser melting CuZr-based glass Bulk metallic glass matrix composites Phase formation Mechanical properties