Graphene-based thermally conductive composites have been proposed as effective thermal management materials for cooling high-power electronic devices.However,when flexible graphene nanosheets are assembled into macros...Graphene-based thermally conductive composites have been proposed as effective thermal management materials for cooling high-power electronic devices.However,when flexible graphene nanosheets are assembled into macroscopic thermally conductive composites,capillary forces induce shrinkage of graphene nanosheets to form wrinkles during solution-based spontaneous drying,which greatly reduces the thermal conductivity of the composites.Herein,graphene nanosheets/aramid nanofiber(GNS/ANF)composite films with high thermal conductivity were prepared by in-plane stretching of GNS/ANF composite hydrogel networks with hydrogen bonds andπ-πinteractions.The in-plane mechanical stretching eliminates graphene nanosheets wrinkles by suppressing inward shrinkage due to capillary forces during drying and achieves a high in-plane orientation of graphene nanosheets,thereby creating a fast in-plane heat transfer channel.The composite films(GNS/ANF-60 wt%)with eliminated graphene nanosheets wrinkles showed a significant increase in thermal conductivity(146 W m^(−1)K^(−1))and tensile strength(207 MPa).The combination of these excellent properties enables the GNS/ANF composite films to be effectively used for cooling flexible LED chips and smartphones,showing promising applications in the thermal management of high-power electronic devices.展开更多
Herein,we reasonably designed MOF-derived Co_(9)S_(8)polyhedrons coated on NiCo_(2)S_(4)nanowire compo-sites for high performance hybrid supercapacitors.The NiCo_(2)S_(4)nanowires have one-dimensional struc-ture that ...Herein,we reasonably designed MOF-derived Co_(9)S_(8)polyhedrons coated on NiCo_(2)S_(4)nanowire compo-sites for high performance hybrid supercapacitors.The NiCo_(2)S_(4)nanowires have one-dimensional struc-ture that can provide better electronic transmission characteristics and Co_(9)S_(8)polyhedrons modified on nanowires can further expand the contact surface area and increase active sites of the Faraday reaction.Besides,the proportion of components can be adjusted and optimized by controlling the reaction time.The synergistic effects between the two components significantly improve their pseudocapacitance.The test results indicated that the specific capacitance of the NiCo_(2)S_(4)/Co_(9)S_(8)electrode with an optimal ratio can reach up to 2390.2 F g^(−1)(331.8 mA h g^(−1))at a current density of 1 A g^(−1).Even when the current density increased to 10 A g^(−1),its rate performance was still maintained at 88.2%.A hybrid supercapacitor was assembled with NiCo_(2)S_(4)/Co_(9)S_(8)and activated carbon shows a high energy density of 47.7 W h kg^(−1) when the power density is 1275 W kg^(−1),as well as good cycle stability(84.1%capacitance retention after 8000 charging/discharging cycles).Therefore,this device has a potential practical space in portable energy storage devices.展开更多
基金the National Natural Science Foundation of China(No.51972162).
文摘Graphene-based thermally conductive composites have been proposed as effective thermal management materials for cooling high-power electronic devices.However,when flexible graphene nanosheets are assembled into macroscopic thermally conductive composites,capillary forces induce shrinkage of graphene nanosheets to form wrinkles during solution-based spontaneous drying,which greatly reduces the thermal conductivity of the composites.Herein,graphene nanosheets/aramid nanofiber(GNS/ANF)composite films with high thermal conductivity were prepared by in-plane stretching of GNS/ANF composite hydrogel networks with hydrogen bonds andπ-πinteractions.The in-plane mechanical stretching eliminates graphene nanosheets wrinkles by suppressing inward shrinkage due to capillary forces during drying and achieves a high in-plane orientation of graphene nanosheets,thereby creating a fast in-plane heat transfer channel.The composite films(GNS/ANF-60 wt%)with eliminated graphene nanosheets wrinkles showed a significant increase in thermal conductivity(146 W m^(−1)K^(−1))and tensile strength(207 MPa).The combination of these excellent properties enables the GNS/ANF composite films to be effectively used for cooling flexible LED chips and smartphones,showing promising applications in the thermal management of high-power electronic devices.
基金upported by Jiangsu Province Postdoctoral Science Foundation(2020Z247)the Innovation Entrepreneurship Program of Jiangsu Province(Suren caiban[2016]32)+1 种基金the National Natural Science Foundation of China(21878129)the Industry Prospect and Key Core Technology(Competition Project)of Jiangsu Province(BE2019093)。
文摘Herein,we reasonably designed MOF-derived Co_(9)S_(8)polyhedrons coated on NiCo_(2)S_(4)nanowire compo-sites for high performance hybrid supercapacitors.The NiCo_(2)S_(4)nanowires have one-dimensional struc-ture that can provide better electronic transmission characteristics and Co_(9)S_(8)polyhedrons modified on nanowires can further expand the contact surface area and increase active sites of the Faraday reaction.Besides,the proportion of components can be adjusted and optimized by controlling the reaction time.The synergistic effects between the two components significantly improve their pseudocapacitance.The test results indicated that the specific capacitance of the NiCo_(2)S_(4)/Co_(9)S_(8)electrode with an optimal ratio can reach up to 2390.2 F g^(−1)(331.8 mA h g^(−1))at a current density of 1 A g^(−1).Even when the current density increased to 10 A g^(−1),its rate performance was still maintained at 88.2%.A hybrid supercapacitor was assembled with NiCo_(2)S_(4)/Co_(9)S_(8)and activated carbon shows a high energy density of 47.7 W h kg^(−1) when the power density is 1275 W kg^(−1),as well as good cycle stability(84.1%capacitance retention after 8000 charging/discharging cycles).Therefore,this device has a potential practical space in portable energy storage devices.
