Doping Modification Of Low-Dimensional Carbon Materials And Their Electromagnetic Properties

With the rapid development of mobile communication and electronic devices,electromagnetic pollution is causing more and more serious impacts on human health and the normal operation of electronic devices.An effective strategy to address these contaminants is to explore superior electromagnetic wave absorbing materials,which has become a research hotspot.In general,the ideal electromagnetic wave absorbing material requires four characteristics:thinness,lightness,strength and width.Carbon nanomaterials such as porous carbon,carbon nanotubes and graphene have received widespread attention in the research of wave absorbing materials due to their light weight,low density,excellent electrical conductivity,corrosion resistance and tunable dielectric constants.In this thesis,the properties of two different types of carbon nanocomposites for electromagnetic wave absorption were investigated through doping modification.The main studies are divided into three parts as follows:(1)A three-dimensional encapsulation of nickel nanoparticles in boron and nitrogen co-doped carbon nanotube composites(3D Ni@BNCNTs)was designed to enhance electromagnetic wave absorption.The results show that at a filling ratio of only 20 wt.%,the composite obtained at 700°C has a maximum absorption intensity of-63.7 d B at a thickness of 1.7 mm,while the composite obtained at 900°C has an effective absorption bandwidth of 4.56 GHz at at a thickness of 1.5 mm and a maximum absorption intensity of-43.5 d B.(2)Undertaking work(1),a series of catalysts such as Co₂B,Ni_0.6Co_1.4B,Ni Co B and Ni_1.4Co_0.6B were constructed and cobalt metal was introduced to prepare multi-metal composite carbon nanotube materials.The results show that Co@BNCNTs-900 exhibits extremely good absorption performance,with a maximum absorption bandwidth of 4.56GHz at a thickness of 1.45 mm and a maximum absorption intensity of-55.5 d B,matching a thickness of 2.7 mm.At the same time,reflection loss values of-20 d B can be achieved at all thicknesses.Ni_1.4Co_0.6@BNCNTs-900 has a maximum absorption bandwidth of4.72 GHz at a thickness of 1.4 mm.Compared to Co@BNCNTs-900,Ni_0.6Co_1.4@BNCNTs-900 has a higher overall absorption intensity and a higher degree of impedance matching.As the relative content of Ni increases,the electromagnetic wave absorption intensity in turn decreases.(3)Ni₂B was used as a microwave absorber graphite oxide was used as a precursor for the solid phase microwave assisted rapid preparation of nickel loaded microwave graphene(Ni@MWRGO).The results show that with fillings as low as 5 wt.%,Ni@MWRGO-100 exhibits the strongest absorption properties,showing excellent absorption at low frequencies,with a maximum absorption intensity of-43.5 d B corresponding to a thickness of 5.0 mm and a maximum effective absorption band of 5.84GHz at 2.2 mm.Ni@MWRGO-200 has a maximum absorption bandwidth of a staggering6.16 GHz and a maximum absorption intensity of-33.6 dB at at a thickness of 2.3 mm.