Two-dimensional plain-weave silicon carbide fiber fabric reinforced silicon carbide(2D-SiC/SiC)composites were molded by stacking method and densified through precursor infiltration and pyrolysis(PIP)process.SiC coati...Two-dimensional plain-weave silicon carbide fiber fabric reinforced silicon carbide(2D-SiC/SiC)composites were molded by stacking method and densified through precursor infiltration and pyrolysis(PIP)process.SiC coating was deposited as the fiber/matrix interphase layer by chemical vapor deposition(CVD)technique.Fiber/matrix debonding and relatively long fiber pullouts were observed on the fracture surfaces.Additionally,the flexural strength and elastic modulus of the composites with and without fiber/matrix interphase layer were investigated using three-point bending test and single-edge notched beam test.The results show that the fiber fraction and the porosity of 2D-SiC/SiC composites with and without coating are 27.2%(volume fraction)and 11.1%,and 40.7%(volume fraction)and 7.5%,respectively.And the flexural strength and elastic modulus of 2D-SiC/SiC composites with and without coating are 363.3 MPa and 127.8 GPa,and 180.2 MPa and 97.2 GPa,respectively.With a proper thickness,the coating can effectively adjust the fiber/matrix interface,thus causing a dramatic increase in the mechanical properties of the composites.展开更多
As the anode active substance of lithium ions battery(LIB),the low conductivity/ion diffusivity and large volume changes of tungsten oxide(WO_(3))lead to its serious polarization during the lithiation/delithiation pro...As the anode active substance of lithium ions battery(LIB),the low conductivity/ion diffusivity and large volume changes of tungsten oxide(WO_(3))lead to its serious polarization during the lithiation/delithiation process,decreasing the cycling stability.To address these challenges,a binder-free anode consisting of nitrogen-doped tungsten oxide nanosheets,encapsulated in carbon layers(N-doped WO_(3)@CL)and entangled with carbon nanotubes macro-films(CMF),was successfully synthesized through a combination of hydrothermal and online assembly method.Compared with the pristine tungsten oxide entangled with carbon nanotubes macro-films(WO_(3)@CMF),the synthesized N-doped WO_(3)@CL@CMF as a binder-free LIB anode demonstrated better electrochemical performance,which could be attributed to(1)surface defects of WO_(3)created by N dopant providing more channels to improve Li^(+)diffusion,(2)the N-doped WO_(3)@CL with a flower-like structure shortening the diffusion length of Li^(+)ions and further leading to high Li^(+)incorporation,and(3)carbon layers and carbon nanotubes synergistically alleviating the large volume change of the N-doped WO_(3)@CL@CMF electrode during the charging and discharging process.The present study offers insights into employing nitrogen dopant and a carbon matrix to mediate the conductivity and wrapped structure in the WO_(3)semiconductor powder,which provides an important strategy for large-scale design of the binder-free LIB anode with high performance.展开更多
基金Project (2019YFC1907404) supported by the National Key R&D Program of ChinaProject (20202ACBL204002) supported by the Key Project of Natural Science Foundation of Jiangxi Province,China+2 种基金Project (GJJ200813) supported by the Jiangxi Province Education Department of Science and Technology,ChinaProject (205200100509) supported by the Program of Scientific Research Foundation of Jiangxi University of Science and Technology,ChinaProject (JXUSTQJBJ2017004) supported by the Program of Qingjiang Excellent Young Talents of Jiangxi University of Science and Technology,China。
基金Project(NCET-07-0228)support by the New Century Excellent Talents in University
文摘Two-dimensional plain-weave silicon carbide fiber fabric reinforced silicon carbide(2D-SiC/SiC)composites were molded by stacking method and densified through precursor infiltration and pyrolysis(PIP)process.SiC coating was deposited as the fiber/matrix interphase layer by chemical vapor deposition(CVD)technique.Fiber/matrix debonding and relatively long fiber pullouts were observed on the fracture surfaces.Additionally,the flexural strength and elastic modulus of the composites with and without fiber/matrix interphase layer were investigated using three-point bending test and single-edge notched beam test.The results show that the fiber fraction and the porosity of 2D-SiC/SiC composites with and without coating are 27.2%(volume fraction)and 11.1%,and 40.7%(volume fraction)and 7.5%,respectively.And the flexural strength and elastic modulus of 2D-SiC/SiC composites with and without coating are 363.3 MPa and 127.8 GPa,and 180.2 MPa and 97.2 GPa,respectively.With a proper thickness,the coating can effectively adjust the fiber/matrix interface,thus causing a dramatic increase in the mechanical properties of the composites.
基金This study was financially supported by the National Natural Science Foundation of China[Grant No.22062008]Supported by the program of Qingjiang Excellent Young Talents,Jiangxi University of Science and Technology[Grant No.JXUSTQJBJ2020008]+2 种基金the Special Fund for Postgraduate Innovation of Jiangxi Province[Grant No.YC2020-S458 and YC2021-S569]National Training Program for College Students’Innovation and Entrepreneurship[Grant No.202110407005X]the Postdoctoral Science Foundation of Jiangxi Province[Grant No.2019KY56 and 2018RC02].
文摘As the anode active substance of lithium ions battery(LIB),the low conductivity/ion diffusivity and large volume changes of tungsten oxide(WO_(3))lead to its serious polarization during the lithiation/delithiation process,decreasing the cycling stability.To address these challenges,a binder-free anode consisting of nitrogen-doped tungsten oxide nanosheets,encapsulated in carbon layers(N-doped WO_(3)@CL)and entangled with carbon nanotubes macro-films(CMF),was successfully synthesized through a combination of hydrothermal and online assembly method.Compared with the pristine tungsten oxide entangled with carbon nanotubes macro-films(WO_(3)@CMF),the synthesized N-doped WO_(3)@CL@CMF as a binder-free LIB anode demonstrated better electrochemical performance,which could be attributed to(1)surface defects of WO_(3)created by N dopant providing more channels to improve Li^(+)diffusion,(2)the N-doped WO_(3)@CL with a flower-like structure shortening the diffusion length of Li^(+)ions and further leading to high Li^(+)incorporation,and(3)carbon layers and carbon nanotubes synergistically alleviating the large volume change of the N-doped WO_(3)@CL@CMF electrode during the charging and discharging process.The present study offers insights into employing nitrogen dopant and a carbon matrix to mediate the conductivity and wrapped structure in the WO_(3)semiconductor powder,which provides an important strategy for large-scale design of the binder-free LIB anode with high performance.
