Preparation And Microwave Absorbing Properties Of Novel Porous Carbon Composites Based On In-MOFs

In recent years,carbon materials have attracted much attention because of their universal functionalities in the fields of catalysis,carrier,energy storage and adsorption.Their special microstructure,low density and tunable dielectric properties also led them as popular candidates for high-performance electromagnetic wave absorbing materials to resolve a series of problems caused by electromagnetic pollution.In this thesis,novel porous carbon electromagnetic wave absorbing materials have been prepared though calcining metal-organic framework of Indium,three different methods were used to improve the microwave absorbing properties.1.In this work,uniformly dispersed ITO（indium tin oxide）/NPC（nanoporous carbon）composites were skillfully synthesized by the direct pyrolysis of In/Sn-MOFs（Sn doped into In-MOFs）for the first time.By controlling the carrier concentration in the In/Sn-MOFs,the conductivity and complex permittivity of the ITO/NPC materials were well modulated,and favorable impedance matching was obtained.When the ratio of Sn/In was 1:9,the obtained ITO/NPC composites display excellent electromagnetic wave absorption.Not only did it own a strong reflection loss（RL）of-55.10 dB at 12.56 GHz and 1.65 mm,but also it exhibited outstanding absorbing properties at the low frequency,and a reflection loss of-47.17 dB was reached at 4.74GHz and 4.10 mm,while the RL values less than-8 dB were found from 3.89 to 5.59GHz.2.In order to obtain more efficient absorbing materials in the low frequency.In/Sn-MOFs and magnetic alloy were compounded by two ways to improve the permeability.Most of the incident EM waves on the surface of ITO/NPC/Fe Ni₃composites are reflected,a maximum reflection loss（RL）of-20.06 dB at with the thickness of 5.5 mm at a frequency of 17.44 GHz.In view of the shortcomings of this kind of materials,Fe In（Sn）Ni₃/NPC composite materials were prepared by grinding method,a maximum reflection loss（RL）of-58.56 dB at a frequency of 3.74 GHz and a thickness of 4.76mm.3.More and more studies have been reported to improve the microwave absorption properties by using heteroatom（nitrogen,sulfur and phosphorus）doping method in recent years.The introduction of heteroatoms into the carbon materials not only increased the polarization loss,but also may bring new loss mechanism,so as to further improved the electromagnetic properties of the composites without affecting its structure.In this chapter,{[Me₂NH₂][In（TDA）₂]·DMA}_n/Sn with sulfur-and nitrogen-containing element were selected as the precursor,after pyrolysis,porous carbon composite materials contain nitrogen and sulfur heteroatoms can be obtained,which achieved wide-band absorption effect.By adjusting the carbonization temperature and the filler content to control the dielectric constant,excellent absorption performance can be achieved.When the thickness was 2.00 mm,it had a wide absorption bandwidth of 6.96 GHz（RL≤-8dB）,covered the frequency range of11-17.96 GHz.