Study On Preparation And Microwave Absorption Properties Of Cobalt-based MOFs Derived Composites

The new radio technology was widely used in civil and military fields,such as wireless communication,medical treatment,scientific research,especially in the military industry.However,excessive electromagnetic radiation had been regarded as a new dangerous source of pollution,which seriously threatened human health and interfered with the normal operation of precision instruments.Therefore,the design and development of high-performance microwave absorption materials were increasingly urgent.As the precursors of microwave absorption materials,metal-organic frames（MOFs）with unique microstructure and electronic states have become a research hotspot in the field of microwave absorption.In general,MOFs-derived composites exhibit excellent microwave absorption properties due to their unique three-dimensional（3D）structure and magnetodielectric synergies.In this paper,cobalt-based MOFs（Co-MOFs）were combined with low-dimensional and high-conductivity carbon materials to build the 3D conductive network.The electromagnetic parameters were effectively adjusted through the composition and structure design,and the composites with excellent microwave absorption performance was synthesized.The results of this study are expected to provide reference for the microstructure design and microwave absorption property regulation of MOFs-derived composites.The research contents are as follows:（1）Graphitic carbon nitride nanotubes/Cobalt-@carbon（GCNNs/Co@C）composites were prepared by solvothermal method and in situ carbonation pyrolysis.The mass ratio of Co-MOFs to melamine（C₃N₆H₆）significantly affected the microstructure and dielectric loss properties of GCNNs/Co@C composites.When the mass ratio of Co-MOFs to C3N6H6 is 1:3,GCNNs/Co@C composites show excellent microwave absorption performance.The minimum reflection loss(RL_min)was-63.90d B（1.96 mm）,and the effective absorption bandwidth（EAB,RL<-10 d B）was 4.44GHz（1.51 mm）.In addition,EAB can cover the entire X and Ku bands（6.96-18.00GHz）by adjusting the thickness（1.51 to 2.50 mm）.（2）The Co₃O₄/carbon cloth（Co₃O₄/CC）flexible composites like blanket were prepared by static growing method and annealing process.The micro-morphology and electromagnetic parameters of Co₃O₄/CC flexible composites were effectively adjusted by adjusting the static reaction time.When the static reaction time was 8 h,the Co₃O₄/CC flexible composites had the best microwave absorption performance,with RL_min reached-54.43 d B（2.46 mm）and EAB reached 4.54 GHz（1.28 mm）.The results show that the array Co₃O₄ loaded on the surface of the carbon cloth can reduce the dielectric loss and increase the polarization loss to achieve impedance matching,so as to improve the microwave absorption performance.（3）Biomass carbon was used as carbon source,and luffa sponge carbon/Co（CLS/Co）composites were prepared by static growth method and high temperature pyrolysis.The microstructure and electromagnetic parameters of CLS/Co composites were effectively controlled by changing the pyrolysis temperature.The RL_min of CLS/Co composites reached-60.81 d B（2.61 mm）at 700 ^oC pyrolysis temperature,and the EAB width reached 5.56 GHz at the ultra-thin thickness of 1.68 mm.Figure[42]Table[5]Reference[164]...