Preparation And Electromagnetic Wave Absorption Propertie Of Honeycomb-like C/Co Composites

With the widespread use of electromagnetic equipment and the rapid development of wireless communications,severe electromagnetic pollution has a huge impact on the environment and human health.In addition,in the military field,the rapid development of modern radio technology and radar detection systems has greatly promoted the ability to search and track targets in warfare,and the threats to traditional combat weapons have become increasingly serious.Therefore,it is of great significance to develop new and efficient electromagnetic wave absorbing materials.Among porous carbon materials derived from metal-organic framework materials(MOFs),magnetic metal nanoparticles are embedded in the porous carbon matrix to make them have good conductivity and high electromagnetic wave attenuation rate,which has attracted much attention.In this dissertation,the hierarchical porous structures ZIF-67 and ZIF-67@SiO2 were prepared by ultrasonic chemical method.After further pyrolysis,honeycomb-like C/Co composites(H-C/Co)were prepared.The morphology and absorbing properties of the prepared H-C/Co were studied by changing the pyrolysis temperature and the amount and size of the SiO2 template.The main contents of this dissertation are as follows:(1)Preparation of H-C/Co composites derived from hierarchical pore structure ZIF-67 and study on its absorption propertiesPolyvinylpyrrolidone(PVP)was used as a pore-forming agent and graphene oxide(GO)was used as an auxiliary pore-forming agent to prepare a ZIF-67 with a hierarchical porous structure.After in-situ pyrolysis in an argon(Ar)atmosphere,H-C/Co composites with rich hierarchical pore structure was obtained.This hierarchical porous structure enables H-C/Co composites to have highly efficient wave absorbing properties.When the pyrolysis temperature is 700℃,the maximum reflection loss can reach-50.7 dB,the effective bandwidth is 4.6 GHz,and the fill rate is only 10 wt%.(2)H-C/Co prepared by～60 nm SiO2 as template and study on its absorption propertiesZIF67@SiO2(～60 nm)was prepared by using～60 nm PVP-functionalized SiO2.After in-situ pyrolysis in an argon(Ar)atmosphere and removing the SiO2 template by HF,H-C/Co with regular～60 nm pores was obtained.As the amount of SiO2 added increases,the number of pores of H-C/Co increases and the size of H-C/Co particles increases.When the amount of SiO2 is 1 mL,the maximum reflection loss can reach-56.2 dB,the effective bandwidth is 9.0 GHz,and the fill rate is only 10 wt%.(3)H-C/Co prepared by SiO2 with different particle size as template and study on its absorption propertiesZIF67@SiO2(15,60,130)were prepared by using～15 nm,～60 nm,and～130 nm PVP-functionalized SiO2.ZIF67@SiO2(15,60,130)was pyrolyzed in an Ar atmosphere.After the SiO2 template was removed by HF to obtain H-C/Co with micropores/mesopores,micropores/macropores,micropores/micron-sized pores.H-C/Co-15 and H-C/Co-60 still maintain the original polyhedron morphology.There are～15 nm and～60 nm circular holes on the surface and inside.When the particle size of SiO2 added is～130 nm,the original polyhedron morphology of H-C/Co-130 was slightly damaged,and carbon nanotubes were grown on the surface.When the particle size of SiO2 added is～60 nm,the maximum reflection loss can reach-56.2 dB,the effective bandwidth is 9.0 GHz,and the fill rate is only 10 wt%.(4)H-C/Co prepared by SiO2 with mixed particle size as template and study on its microwave absorption performanceZIF67@SiO2(15/60,15/130,60/130)were prepared by PVP-functionalized SiO2 with mixed particle size as template(mixing at a ratio of 1:1).ZIF67@SiO2(15/60,15/130,60/130)were pyrolyzed in an Ar atmosphere.After the SiO2 template was removed by HF to obtain H-C/Co with micropores/mesopores/macropores,micropores/mesopores/microns-pores,micropores/macropores/microns-pores.H-C/Co-15/60,H-C/Co-15/130 and H-C/Co-60/130 still maintain the original polyhedron morphology.There were～15/60 nm,～15/130 nm,～60/130 nm circular holes on the surface and inside.When the particle size of SiO2 added is～15/60 nm,the maximum reflection loss can reach-85.5 dB,the effective bandwidth is 8.2 GHz,and the fill rate is only 10 wt%.