Cu suffers from oxidation and corrosion during application due to its active chemical properties.Graphene⁃modified Cu can significantly improve its stability during application.However,copper is easily sintered at hig...Cu suffers from oxidation and corrosion during application due to its active chemical properties.Graphene⁃modified Cu can significantly improve its stability during application.However,copper is easily sintered at high temperatures,so that graphene cannot be grown inside.We demonstrate two kinds of spacers,graphite and SiO_(2),which are effective in preventing the sintering of copper and are used to assist in the growth of graphene.In the Cu⁃C system,the nucleation of graphene is scarce,and it tends to nucleate and grow on the concave surface of copper first,and then grow epitaxially to the convex surface of copper.Eventually,the obtained graphene is relatively thick.In the Cu⁃SiO_(2) system,due to the oxygen released by SiO_(2) at high temperatures,the surface of copper becomes rough.This leads to an increase in the number of graphene nucleation sites without preferred orientation,and relatively thin graphene is obtained.Two different growth mechanisms have been established for spacerseffects on graphene growth.It provides insights for graphene engineering for further applications.展开更多
During the operation of electronic devices,a considerable amount of heat and electromagnetic radiation is emitted.Therefore,the investigation of materials with electromagnetic shielding and thermal management abilitie...During the operation of electronic devices,a considerable amount of heat and electromagnetic radiation is emitted.Therefore,the investigation of materials with electromagnetic shielding and thermal management abilities has significant importance.Hybrid materials of three-dimensional graphene networks containing both carbon nanotubes(CNTs)and SiC whiskers(3D graphene-CNT-SiC)were synthesized.Using an aqueous-phase reduction method for the self-assembly of the graphene oxide,a three-dimen-sional porous graphene structure was fabricated.SiC whiskers,inserted between the graphene layers,formed a framework for longit-udinal thermal conduction,while CNTs attached to the SiC surface,created a dendritic structure that increased the bonding between the SiC whiskers and graphene,improving dielectric loss and thermal conductivity.It was found that the thermal conductivity of the hybrid material reached 123 W·m^(-1)·K^(-1),with a shielding effectiveness of 29.3 dB when the SiC addition was 2%.This result indic-ates that 3D graphene-CNT-SiC has excellent thermal conductivity and electromagnetic shielding performance.展开更多
Developing lightweight and flexible thin films for electromagnetic interference(EMI)shielding is of great importance.Porous thin films of reduced graphene oxide containing SiC whiskers(SiC@RGO)for EMI shielding were p...Developing lightweight and flexible thin films for electromagnetic interference(EMI)shielding is of great importance.Porous thin films of reduced graphene oxide containing SiC whiskers(SiC@RGO)for EMI shielding were prepared by a two-step reduction of graphene oxide(GO),in which the two steps were chemical reduction by HI and the solid phase microwave irradiation.A significant increase of the film thickness from around 20 to 200μm was achieved due to the formation of a porous structure by gases released during the 3 s of solid phase microwave irradiation.The total shielding effectiveness(SET)and the reflective SE(SE_(R))of the SiC@RGO porous thin films depended on the GO/SiC mass ratio.The highest SET achieved was 35.6 dB while the SE_(R) was only 2.8 dB,when the GO/SiC mass ratio was 4∶1.The addition of SiC whiskers was critical for the multi-reflection,interfacial po-larization and dielectric attenuation of EM waves.A multilayer film with a gradient change of SE values was constructed using SiC@RGO porous films and multi-walled carbon nanotubes buckypapers.The highest SET of the multilayer films reached 75.1 dB with a SE_(R) of 2.7 dB for a film thickness of about 1.5 mm.These porous SiC@RGO thin films should find use in multilayer or sand-wich structures for EMI absorption in packaging or lining.展开更多
文摘Cu suffers from oxidation and corrosion during application due to its active chemical properties.Graphene⁃modified Cu can significantly improve its stability during application.However,copper is easily sintered at high temperatures,so that graphene cannot be grown inside.We demonstrate two kinds of spacers,graphite and SiO_(2),which are effective in preventing the sintering of copper and are used to assist in the growth of graphene.In the Cu⁃C system,the nucleation of graphene is scarce,and it tends to nucleate and grow on the concave surface of copper first,and then grow epitaxially to the convex surface of copper.Eventually,the obtained graphene is relatively thick.In the Cu⁃SiO_(2) system,due to the oxygen released by SiO_(2) at high temperatures,the surface of copper becomes rough.This leads to an increase in the number of graphene nucleation sites without preferred orientation,and relatively thin graphene is obtained.Two different growth mechanisms have been established for spacerseffects on graphene growth.It provides insights for graphene engineering for further applications.
文摘During the operation of electronic devices,a considerable amount of heat and electromagnetic radiation is emitted.Therefore,the investigation of materials with electromagnetic shielding and thermal management abilities has significant importance.Hybrid materials of three-dimensional graphene networks containing both carbon nanotubes(CNTs)and SiC whiskers(3D graphene-CNT-SiC)were synthesized.Using an aqueous-phase reduction method for the self-assembly of the graphene oxide,a three-dimen-sional porous graphene structure was fabricated.SiC whiskers,inserted between the graphene layers,formed a framework for longit-udinal thermal conduction,while CNTs attached to the SiC surface,created a dendritic structure that increased the bonding between the SiC whiskers and graphene,improving dielectric loss and thermal conductivity.It was found that the thermal conductivity of the hybrid material reached 123 W·m^(-1)·K^(-1),with a shielding effectiveness of 29.3 dB when the SiC addition was 2%.This result indic-ates that 3D graphene-CNT-SiC has excellent thermal conductivity and electromagnetic shielding performance.
文摘Developing lightweight and flexible thin films for electromagnetic interference(EMI)shielding is of great importance.Porous thin films of reduced graphene oxide containing SiC whiskers(SiC@RGO)for EMI shielding were prepared by a two-step reduction of graphene oxide(GO),in which the two steps were chemical reduction by HI and the solid phase microwave irradiation.A significant increase of the film thickness from around 20 to 200μm was achieved due to the formation of a porous structure by gases released during the 3 s of solid phase microwave irradiation.The total shielding effectiveness(SET)and the reflective SE(SE_(R))of the SiC@RGO porous thin films depended on the GO/SiC mass ratio.The highest SET achieved was 35.6 dB while the SE_(R) was only 2.8 dB,when the GO/SiC mass ratio was 4∶1.The addition of SiC whiskers was critical for the multi-reflection,interfacial po-larization and dielectric attenuation of EM waves.A multilayer film with a gradient change of SE values was constructed using SiC@RGO porous films and multi-walled carbon nanotubes buckypapers.The highest SET of the multilayer films reached 75.1 dB with a SE_(R) of 2.7 dB for a film thickness of about 1.5 mm.These porous SiC@RGO thin films should find use in multilayer or sand-wich structures for EMI absorption in packaging or lining.
