Preparation Of Three-dimensional Porous C/Ni/CNTs Composites Derived From Natural Wood And Their Electromagnetic Properties

In recent years,with the development of 5 G technology,the application of various electronic products and devices has been popularized in all aspects of life and work.Traditional magnetic metal electromagnetic shielding materials have been difficult to meet the requirements of current military equipment and civilian protection due to their large specific gravity,easy to fall off,and poor resistance to extreme environments.The shielding body is required to have the characteristics of resistance to extreme environments,good thermal stability,mechanical properties,and absorption-dominant characteristics.Therefore,the development of new electromagnetic shielding materials is an urgent problem to be solved in the current research on shielding materials.Wood-based carbon materials are widely used in the field of electromagnetic shielding materials due to their light weight,high electrical conductivity,low cost and easy preparation.First,anisotropic carbon scaffolds were prepared by chemical treatment and high-temperature carbonization.Due to the structural anisotropy of the carbon scaffold,the longitudinal carbon scaffold has a high specific surface area（655.14 m~2/g）and electrical conductivity（17.5 S/cm）,and has an excellent electromagnetic shielding performance of 54.9 d B in the K-band.Its compressive strength reaching 23.2 MPa,thermal conductivity of 0.58 W/m·K and superhydrophilic（contact angle of about 0°）;while the specific surface area（461.47 m~2/g）and electrical conductivity（13.4 S/cm）of the lateral carbon scaffolds were lower than the longitudinal carbon scaffolds,and had an electromagnetic shielding performance of 46.4 d B in the K-band,its compressive strength was only 2.9 MPa,and its thermal conductivity was0.14 W/m·K,showing good hydrophobic properties.Under the dual action of the internal conductivity loss of the carbon scaffold and the multiple reflections in the aperture,the carbon scaffold is transformed from an electromagnetic shielding material dominated by a reflection mechanism to an electromagnetic shielding material dominated by an absorption mechanism through lateral to vertical regulation.Furthermore,porous C/Ni/CNTs composites were prepared by dipping method and chemical vapor deposition（CVD）method to recombine porous C with magnetic metal Ni and grow carbon nanotubes（CNTs）.When the concentration of Ni Cl₂ solution is 1.5 mol/L,the electrical conductivity of the composite（C-Ni-1.5）is 2.58 S/cm,the electromagnetic shielding performance is 35.9 d B,and the excellent hydrophobicity（water contact angle is 141°）;The electric field accelerates the movement of electrons in the material,which can enhance the electromagnetic shielding performance.When the applied voltage is 4 V,the electromagnetic shielding performance of the C-Ni-1.5sample is 45.8 d B.The composite material also has high-efficiency electrothermal conversion,magnetic traction,crude oil adsorption,thermal stability,and recyclability,which enhances its applicability as a block electromagnetic shielding material and provides a new theoretical support for cleaning sea surface crude oil pollution.In this paper,natural wood is selected to construct three-dimensional porous C by compounding with magnetic metal Ni and then growing CNTs.First,the problem of impedance mismatch of traditional single carbon materials is solved;secondly,a new composite interface is introduced into the porous structure.Microstructure and morphology control,the preparation of multiphase composite materials,the exploration of the influence of different interface bonding methods and microstructure on the electromagnetic shielding performance and the formation process principle of composite materials and other scientific issues,revealed the interface polarization,multiple reflection,Electromagnetic shielding mechanism under multiple complex effects such as multiple scattering,electron polarization,and electromagnetic synergy.It provides a new theoretical basis for the research of new carbon-based electromagnetic shielding materials with extreme environment resistance,good thermal stability,mechanical properties,and absorption-dominated materials,and provides new ideas for the intelligent application of new electromagnetic shielding materials.It plays a certain role in promoting the application of electromagnetic shielding materials in military and civilian fields.