The effects of gradient nanostructures induced by supersonic fine particle bombardment(SFPB)on the surface integrity,microstructural evolution,and mechanical properties of a Ni-W-Co-Ta medium-heavy alloy(MHA)were syst...The effects of gradient nanostructures induced by supersonic fine particle bombardment(SFPB)on the surface integrity,microstructural evolution,and mechanical properties of a Ni-W-Co-Ta medium-heavy alloy(MHA)were systematically investigated.The results show that gradient nanostructures are formed on the surface of Ni-W-Co-Ta MHA after SFPB treatment.At a gas pressure of 1.0 MPa and an impact time of 60 s,the ultimate tensile strength and yield strength of the alloy reached the maximum values of 1236 MPa and 758 MPa,respectively,which are 22.5%and 38.8%higher than those of the solid solution treated alloy,and the elongation(46.3%)is close to that of the solid solution treated alloy,achieving the optimal strength–ductility synergy.However,microcracks appear on the surface with excessive gas pressure and impact time,generating the relaxed residual stress and decreased strength.With the increase of the impact time and gas pressure,the depth of the deformation layer and the surface microhardness gradually increase,reaching the maximum values(29μm and HV 451)at 1.0 MPa and 120 s.The surface grain size is refined to a minimum of 11.67 nm.Notably,SFPB treatment has no obvious effect on elongation,and the fracture mode changes from the ductile fracture before treatment to ductile–brittle mixed fracture after treatment.展开更多
Multiple laser shock processing （LSP） impacts on microstructures and mechanical properties were investigated through morphological determinations and hardness testing. Microscopic results show that without equal cha...Multiple laser shock processing （LSP） impacts on microstructures and mechanical properties were investigated through morphological determinations and hardness testing. Microscopic results show that without equal channel angular pressing （ECAP）, the LSP-treated lamellar pearlite was transferred to irregular ferrite matrix and incompletely broken cementite particles. With ECAP, LSP leads to refinements of the equiaxed ferrite grain in ultrafine-grained microduplex structure from 400 to 150 nm, and the completely spheroidized cementite particles from 150 to 100 nm. Consequentially, enhancements of mechanical properties were found in strength, microhardness and elongations of samples consisting of lamellar pearlite and ultrafine-grained microduplex structure. After LSP, a mixture of quasi-cleavage and ductile fracture was formed, different from the typical quasi-cleavage fracture from the original lamellar pearlite and the ductile fracture of the microduplex structure.展开更多
Metal halide perovskites have emerged as novel and promising photocatalysts for hydrogen generation.Currently,their stability in water is a vital and urgent research question.In this paper a novel approach to stabiliz...Metal halide perovskites have emerged as novel and promising photocatalysts for hydrogen generation.Currently,their stability in water is a vital and urgent research question.In this paper a novel approach to stabilize a bismuth halide perovskite[(CH_(3))_(2)NH_(2)]_(3)[Bil_(6)](DA_(3)Bil_(6))in water using dimethylammonium iodide(DAI)without the assistance of acids or coatings is reported.The DA3Bil6 powder exhibits good stability in DAI solutions for at least two weeks.The concentration of DAI is found as a critical parameter,where the I^(-)ions play the key role in the stabilization.The stability of DA3Bil6 in water is realized via a surface dissolution-recrystallization process.Stabilized DA3Bil6 demonstrates constant photocatalytic properties for visible light-induced photo-oxidation of I^(-)ions and with PtCI4 as a co-catalyst(Pt-DA_(3)Bil_(6)),photocatalytic H2 evolution with a rate of 5.7μmol·h^(-1)from HI in DAI solution,obtaining an apparent quantum efficiency of 0.83%at 535 nm.This study provides new insights on the stabilization of metal halide perovskites for photocatalysis in aqueous solution.展开更多
Spirothiopyran(STP)is particularly attractive when used as a mechanophore to endow polymers with both damage-signaling and.self-reinforcing capacity.It is,however,not clear the actual force required to induce the cycl...Spirothiopyran(STP)is particularly attractive when used as a mechanophore to endow polymers with both damage-signaling and.self-reinforcing capacity.It is,however,not clear the actual force required to induce the cycloreversion of STP into ring-opened thiomerocyanine(TMC),which reacts spontaneously with activated C=C bonds.Here,we used atomic force microscopy(AFM)-based single molecule force spectroscopy(SMFS)to study the mechanochemistry of STP mechanophore.It is found that the ring-opening of STP at room temperature requires forces of-200-400 pN,depending on the pulling speed.In addition,the reversibility of STP to TMC isomerization is demonstrated.Finally,mechanochemically induced intermolecular Click addition is achieved in single'molecule level by pulling STP in the presence of maleimide.展开更多
基金supported by the National key Research and Development Program of China(No.2022YFB3705200)the National Natural Science Foundation of China(Nos.U1804146,51905153,52111530068)+1 种基金the Science and Technology Innovation Team Project of Henan University of Science and Technology,China(No.2015XTD006)the Major Science and Technology Project of Henan Province,China(No.221100230200)。
文摘The effects of gradient nanostructures induced by supersonic fine particle bombardment(SFPB)on the surface integrity,microstructural evolution,and mechanical properties of a Ni-W-Co-Ta medium-heavy alloy(MHA)were systematically investigated.The results show that gradient nanostructures are formed on the surface of Ni-W-Co-Ta MHA after SFPB treatment.At a gas pressure of 1.0 MPa and an impact time of 60 s,the ultimate tensile strength and yield strength of the alloy reached the maximum values of 1236 MPa and 758 MPa,respectively,which are 22.5%and 38.8%higher than those of the solid solution treated alloy,and the elongation(46.3%)is close to that of the solid solution treated alloy,achieving the optimal strength–ductility synergy.However,microcracks appear on the surface with excessive gas pressure and impact time,generating the relaxed residual stress and decreased strength.With the increase of the impact time and gas pressure,the depth of the deformation layer and the surface microhardness gradually increase,reaching the maximum values(29μm and HV 451)at 1.0 MPa and 120 s.The surface grain size is refined to a minimum of 11.67 nm.Notably,SFPB treatment has no obvious effect on elongation,and the fracture mode changes from the ductile fracture before treatment to ductile–brittle mixed fracture after treatment.
基金supported by the National Natural Science Foundation of China(Nos.U1804146,51801054,52111530068)the Program for Science and Technology Innovation Talents in Universities of Henan Province,China(No.17HASTIT026)+2 种基金the Foreign Experts Introduction Project of Henan Province,China(No.HNGD2020009)the Science and Technology Innovation Team of Henan University of Science and Technology,China(No.2015XTD006)the Academy of Finland(No.311934)。
文摘Multiple laser shock processing （LSP） impacts on microstructures and mechanical properties were investigated through morphological determinations and hardness testing. Microscopic results show that without equal channel angular pressing （ECAP）, the LSP-treated lamellar pearlite was transferred to irregular ferrite matrix and incompletely broken cementite particles. With ECAP, LSP leads to refinements of the equiaxed ferrite grain in ultrafine-grained microduplex structure from 400 to 150 nm, and the completely spheroidized cementite particles from 150 to 100 nm. Consequentially, enhancements of mechanical properties were found in strength, microhardness and elongations of samples consisting of lamellar pearlite and ultrafine-grained microduplex structure. After LSP, a mixture of quasi-cleavage and ductile fracture was formed, different from the typical quasi-cleavage fracture from the original lamellar pearlite and the ductile fracture of the microduplex structure.
基金the Kvantum Institute Em erging Project at the University of Oulu and Academy of Finland ELECTRA-project(No.2430291511).We thank Raija Oilunkaniemi and idarkus Riihimaki for the help with XRD and ATR characterization,respectively.We are grateful to the staff from Centre for Material Analysis(University of Oulu)for the characterization.ELI-ALPS is supported by the European Union and co-flnanced by the European Regional Development Fund(No.GINOP-2.3.6-15-2015-00001).M.U.K.also acknow ledgesfundingfrom PaNOSC Europeanproject.
文摘Metal halide perovskites have emerged as novel and promising photocatalysts for hydrogen generation.Currently,their stability in water is a vital and urgent research question.In this paper a novel approach to stabilize a bismuth halide perovskite[(CH_(3))_(2)NH_(2)]_(3)[Bil_(6)](DA_(3)Bil_(6))in water using dimethylammonium iodide(DAI)without the assistance of acids or coatings is reported.The DA3Bil6 powder exhibits good stability in DAI solutions for at least two weeks.The concentration of DAI is found as a critical parameter,where the I^(-)ions play the key role in the stabilization.The stability of DA3Bil6 in water is realized via a surface dissolution-recrystallization process.Stabilized DA3Bil6 demonstrates constant photocatalytic properties for visible light-induced photo-oxidation of I^(-)ions and with PtCI4 as a co-catalyst(Pt-DA_(3)Bil_(6)),photocatalytic H2 evolution with a rate of 5.7μmol·h^(-1)from HI in DAI solution,obtaining an apparent quantum efficiency of 0.83%at 535 nm.This study provides new insights on the stabilization of metal halide perovskites for photocatalysis in aqueous solution.
基金funded by the National Natural Science Foundation of China((Nos.21525418 and 21827805)(W.Z.),(Nos.21774106 and 21574108)(W.W.)).
文摘Spirothiopyran(STP)is particularly attractive when used as a mechanophore to endow polymers with both damage-signaling and.self-reinforcing capacity.It is,however,not clear the actual force required to induce the cycloreversion of STP into ring-opened thiomerocyanine(TMC),which reacts spontaneously with activated C=C bonds.Here,we used atomic force microscopy(AFM)-based single molecule force spectroscopy(SMFS)to study the mechanochemistry of STP mechanophore.It is found that the ring-opening of STP at room temperature requires forces of-200-400 pN,depending on the pulling speed.In addition,the reversibility of STP to TMC isomerization is demonstrated.Finally,mechanochemically induced intermolecular Click addition is achieved in single'molecule level by pulling STP in the presence of maleimide.
