Co/carbon nanofiber with adjustable size and content of Co nanoparticles for tunable microwave absorption and thermal conductivity

Electromagnetic pollution and heat dissipation problems are becoming increasingly worthy of attention due to the rapid development of electronic devices,which puts forward an urgent demand for microwave absorbers with excellent thermal management performance.Herein,high-performance Co/carbon nanofiber(Co/CNF)microwave absorbers with high thermal conductivity were fabricated by facile step-by-step method.The microwave absorption properties can be readily tuned by adjusting the content and size of Co nanoparticles through concentration gradient adsorption.Benefiting from the formation of dielectric and magnetic coupling network,Co/CNF composites possess intensive dipole polarization,interface polarization,and magnetic loss.The optimal Co/CNF composites exhibit outstanding microwave absorption performance with a minimum reflection loss(RL)of−53.0 dB at 11.44 GHz,and a maximum effective absorption bandwidth(EAB)of 5.5 GHz.In addition,the thermal conductivities of the Co/CNF-natural rubber(Co/CNF-NR)composites are significantly improved.This work may inspire the exploration of high-efficiency heat-conduction microwave absorbers based on CNF.

Rationally tailoring interface characteristics of ZnO/amorphous carbon/graphene for heat-conduction microwave absorbers

With the increasingly severe electromagnetic interference issue and the huge heat dissipation demand caused by the miniaturized and integrated electronic devices,exploring the heat-conduction microwave absorption(MA)materials is highly desired and remains a great challenge.Herein,we reported the fabrication of ZnO/amorphous carbon(ZnO/AC)hybrid films covered on the surface of graphene(ZnO/AC/Graphene)to simultaneously apply as the MA and thermal management materials.The ZnO/AC coatings synthesized with the auxiliary of an atomic layer deposition(ALD)method are highly uniform and controllable,which can significantly improve the MA performance and thermal conduction properties of graphene.The reflection loss(RL)of−55.4 dB and the effective absorption bandwidth of 5.3 GHz were achieved with thickness of 2.0 mm for ZnO/AC/Graphene at a low loading content(3 wt.%).The minimum RL of−57.9 dB can be obtained in the ZnO/AC/Graphene composites at a low frequency(7.8 GHz).Moreover,the absorption frequency can be regulated by changing the ZnO/AC which can be readily implemented by adjusting the ALD cycles of ZnO.The thermal conductivity of ZnO/AC/Graphene is up to 257.8 mW·m^(−1)·K^(−1),increased by 53.2%compared with natural rubber.The enhancement mechanisms of microwave loss and heat conduction are systematically studied in detail.This work not only develops an excellent candidate,but also provides a novel strategy to design functional materials for heat-conduction MA application.