Nowadays,magnesium(Mg)alloys are promising lightweight structural materials,especially in transportation and aerospace fields,due to their inherent low density and high specific strength.Most of the high-strength Mg a...Nowadays,magnesium(Mg)alloys are promising lightweight structural materials,especially in transportation and aerospace fields,due to their inherent low density and high specific strength.Most of the high-strength Mg alloys exhibit poor formability and ductility at room temperature,which limit their wide applications.However,by proper alloying design and/or delicate microstructural control,some newly developed Mg alloys,including rare-earth(RE)and RE-free ones,show enhanced ductility without significant loss of strength.To identify the critical reasons,recent researches on ductile Mg alloys have been reviewed from the aspects of alloying design strategies and microstructural control via advanced processing technologies.Moreover,some outlooks on enhanced ductility of Mg alloys are suggested,e.g.enhancing the beneficial effect of solute atoms,introducing second phase particles,tailoring bimodal-grained structures,introducing pre-twinning structures,etc.The current research progresses in alloying design and/or novel microstructural control have shed some lights on designing and producing Mg alloys with enhanced ductility.展开更多
High-performance organic composite thermoelectric(TE)materials are considered as a promising alternative for harvesting heat energy.Herein,composite films of poly(3,4-ethyienedioxythiophene):poly(styrene sulfonate)/si...High-performance organic composite thermoelectric(TE)materials are considered as a promising alternative for harvesting heat energy.Herein,composite films of poly(3,4-ethyienedioxythiophene):poly(styrene sulfonate)/single-walled carbon nanotubes(PEDOT:PSS/SWCNTs)were fabricated by utilizing a convenient solution mixing method.Thereafter,the as-prepared hybrid films were treated using sulfuric acid(H_(2)SO_(4))to further optimize the TE performance.Film morphological studies revealed that the sulfuric acid treated PEDOT:PSS/SWCNTs composite samples all possessed porous structures.Due to the successful fabrication of highly conductive networks,the porous nano-architecture also exhibited much more excellent TE properties when compared with the dense structure of the pristine samples.For the post-treated sample,a high power factor of 156.43μW·m^(-1)·K^(-2)can be achieved by adjusting the content of CNTs,which is approximately 3 orders of magnitude higher than that of the corresponding untreated samples(0.23μW·m^(-1)·K^(-2)).Besides,the obtained films also showed excellent mechanical flexibility,owing to the porous nanostructure and the strong p–p interactions between the two components.This work indicates that the H_(2)SO_(4) treatment could be a promising strategy for fabricating highly-flexible and porous PEDOT:PSS/SWCNTs films with high TE performances.展开更多
In this paper,a three-dimensional(3D)hierar-chical ZnO structure consisting of nanosheets modified with ultrafine NiO particles was synthesized via a facile two-step chemical precipitate method.Various techniques char...In this paper,a three-dimensional(3D)hierar-chical ZnO structure consisting of nanosheets modified with ultrafine NiO particles was synthesized via a facile two-step chemical precipitate method.Various techniques characterized the as-synthesized ZnO/NiO composites and pure ZnO.The p-NiO/n-ZnO junctions formed between adjacent ZnO and NiO nanoparticles,improving the gas sensing performance.The ZnO/NiO composite with the Ni:Zn atomic ratio of 7.42:100 exhibited the best iso-propanol sensing properties.Compared to pure ZnO,it showed high selectivity and sensitivity(R_(a)/R_(g)=221.3 toward 400×10^(-6)isopropanol),fast response rate(less than 10 s),short recovery time,and simultaneously low operating temperature.Also,the ZnO/NiO composite exhibited a wide sensing range(1×10^(-6)-1000×10^(-6))to isopropanol and processed good long-term stability.The experimental results suggested the potential application in fabricating efficient isopropanol sensors using this ZnO/NiO composite.The enhanced isopropanol sensing mech-anism is also discussed in charge transfer between heterojunctions,surface area,and surface defects.展开更多
In our present work, a novel controlled radical polymerization system is developed based on xanthene-9-thione （XT）. It was found that the radical polymerization of styrene （St） became controlled in the presence of...In our present work, a novel controlled radical polymerization system is developed based on xanthene-9-thione （XT）. It was found that the radical polymerization of styrene （St） became controlled in the presence of a small amount of XT. At the early stage of the polymerization, the polymerization rate was relatively low and the as-formed polystyrene （PS） had low number-average molecular weight （Mn） and narrow polydispersity （D）. After XT was consumed, the polymerization rate increased dramatically and the Mn of PS increased gradually with polymerization proceeding. When the polymerization of St was carried out with a proper molar ratio of initiator to XT and at an appropriate temperature, shortened slow polymerization stage and good control over Mn could be achieved. To further improve the regulating ability of XT, a series of substituent groups （-CF3, --CH（CH3）2, --N（CH3）2） were introduced onto the xanthene ring of XT, and the effects of these derivatives on the polymerization of St were investigated in detail. UV-Vis spectroscopy was carried out to monitor the concentration of XT during the polymerization and the chemical structure of the as-formed PS was fully characterized by IH- NMR and ESI-MS analysis. A possible mechanism involving the formation and evolution of the cross-termination products was proposed to interpret the observed polymerization behavior.展开更多
A new dual plldium/scandium catalysis starting fromβ-alkynyl ketones and o alkynyl anilines is reported for the first time,leading to the atom-economic synthesis of rotationally hindered C3-naphthylated indoles in mo...A new dual plldium/scandium catalysis starting fromβ-alkynyl ketones and o alkynyl anilines is reported for the first time,leading to the atom-economic synthesis of rotationally hindered C3-naphthylated indoles in moderate to good yields and high regioselectivi-ty.This method can tolerate normal air conditions,and features the use of palladium/scandium cooperative catalysts without any ligand,facile double annulation involving various internal alkynes,and good functional group tolerance.展开更多
基金The Natural Science Foundation of China under Grant Nos.51922048,51871108 and 51625402Partial financial support came from the Fundamental Research Funds for the Central Universities,JLU,Program for JLU Science and Technology Innovative Research Team(JLUSTIRT,2017TD-09)The Science and Technology Development Program of Jilin Province(No.20200201193JC)。
文摘Nowadays,magnesium(Mg)alloys are promising lightweight structural materials,especially in transportation and aerospace fields,due to their inherent low density and high specific strength.Most of the high-strength Mg alloys exhibit poor formability and ductility at room temperature,which limit their wide applications.However,by proper alloying design and/or delicate microstructural control,some newly developed Mg alloys,including rare-earth(RE)and RE-free ones,show enhanced ductility without significant loss of strength.To identify the critical reasons,recent researches on ductile Mg alloys have been reviewed from the aspects of alloying design strategies and microstructural control via advanced processing technologies.Moreover,some outlooks on enhanced ductility of Mg alloys are suggested,e.g.enhancing the beneficial effect of solute atoms,introducing second phase particles,tailoring bimodal-grained structures,introducing pre-twinning structures,etc.The current research progresses in alloying design and/or novel microstructural control have shed some lights on designing and producing Mg alloys with enhanced ductility.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2004174,51773118,and 51673044)。
文摘High-performance organic composite thermoelectric(TE)materials are considered as a promising alternative for harvesting heat energy.Herein,composite films of poly(3,4-ethyienedioxythiophene):poly(styrene sulfonate)/single-walled carbon nanotubes(PEDOT:PSS/SWCNTs)were fabricated by utilizing a convenient solution mixing method.Thereafter,the as-prepared hybrid films were treated using sulfuric acid(H_(2)SO_(4))to further optimize the TE performance.Film morphological studies revealed that the sulfuric acid treated PEDOT:PSS/SWCNTs composite samples all possessed porous structures.Due to the successful fabrication of highly conductive networks,the porous nano-architecture also exhibited much more excellent TE properties when compared with the dense structure of the pristine samples.For the post-treated sample,a high power factor of 156.43μW·m^(-1)·K^(-2)can be achieved by adjusting the content of CNTs,which is approximately 3 orders of magnitude higher than that of the corresponding untreated samples(0.23μW·m^(-1)·K^(-2)).Besides,the obtained films also showed excellent mechanical flexibility,owing to the porous nanostructure and the strong p–p interactions between the two components.This work indicates that the H_(2)SO_(4) treatment could be a promising strategy for fabricating highly-flexible and porous PEDOT:PSS/SWCNTs films with high TE performances.
基金financially supported by the Distinguished Taishan Scholars in Climbing Plan (No. tspd20161006)the Major-Special Science and Technology Projects in Shandong Province(Nos.2019JZZY010303 and 2019JZZY010360)Shandong Provincial Natural Science Foundation (No. ZR2019MEM049)。
文摘In this paper,a three-dimensional(3D)hierar-chical ZnO structure consisting of nanosheets modified with ultrafine NiO particles was synthesized via a facile two-step chemical precipitate method.Various techniques characterized the as-synthesized ZnO/NiO composites and pure ZnO.The p-NiO/n-ZnO junctions formed between adjacent ZnO and NiO nanoparticles,improving the gas sensing performance.The ZnO/NiO composite with the Ni:Zn atomic ratio of 7.42:100 exhibited the best iso-propanol sensing properties.Compared to pure ZnO,it showed high selectivity and sensitivity(R_(a)/R_(g)=221.3 toward 400×10^(-6)isopropanol),fast response rate(less than 10 s),short recovery time,and simultaneously low operating temperature.Also,the ZnO/NiO composite exhibited a wide sensing range(1×10^(-6)-1000×10^(-6))to isopropanol and processed good long-term stability.The experimental results suggested the potential application in fabricating efficient isopropanol sensors using this ZnO/NiO composite.The enhanced isopropanol sensing mech-anism is also discussed in charge transfer between heterojunctions,surface area,and surface defects.
基金financially supported by the National Natural Science Foundation of China (Nos. 21404004 and 21474006)the Innovation and Promotion Project of Beijing University of Chemical Technology
文摘In our present work, a novel controlled radical polymerization system is developed based on xanthene-9-thione （XT）. It was found that the radical polymerization of styrene （St） became controlled in the presence of a small amount of XT. At the early stage of the polymerization, the polymerization rate was relatively low and the as-formed polystyrene （PS） had low number-average molecular weight （Mn） and narrow polydispersity （D）. After XT was consumed, the polymerization rate increased dramatically and the Mn of PS increased gradually with polymerization proceeding. When the polymerization of St was carried out with a proper molar ratio of initiator to XT and at an appropriate temperature, shortened slow polymerization stage and good control over Mn could be achieved. To further improve the regulating ability of XT, a series of substituent groups （-CF3, --CH（CH3）2, --N（CH3）2） were introduced onto the xanthene ring of XT, and the effects of these derivatives on the polymerization of St were investigated in detail. UV-Vis spectroscopy was carried out to monitor the concentration of XT during the polymerization and the chemical structure of the as-formed PS was fully characterized by IH- NMR and ESI-MS analysis. A possible mechanism involving the formation and evolution of the cross-termination products was proposed to interpret the observed polymerization behavior.
基金We are grateful for financial support from the National Natural Science Foundation of China(Nos.21871112 and 21971090).
文摘A new dual plldium/scandium catalysis starting fromβ-alkynyl ketones and o alkynyl anilines is reported for the first time,leading to the atom-economic synthesis of rotationally hindered C3-naphthylated indoles in moderate to good yields and high regioselectivi-ty.This method can tolerate normal air conditions,and features the use of palladium/scandium cooperative catalysts without any ligand,facile double annulation involving various internal alkynes,and good functional group tolerance.
