Interfacial polarization dominant CNTs/PyC hollow microspheres as a lightweight electromagnetic wave absorbing material

For the non-magnetic materials, polarization and conductivity loss are the keys to affect the electromagnetic wave absorption properties. The heterogeneous interfacial polarization is an important scientific issue in research of electromagnetic wave absorbing materials. Carbon nanotubes/pyrolytic carbon hollow microspheres (CNTs/PyC HMs) are prepared by in-situ growth of CNTs growing on the surface of zero-dimensional PyC HMs carrier. A large number of heterogeneous interface between CNTs and PyC HMs are constructed. The crystallization degree of CNTs can be significantly regulated in a small temperature range. When the reaction temperature increases from 600 to 700 °C, CNTs gradually change from amorphous to crystalline state. The higher crystallization degree of CNTs leads to a greater conductivity differences in heterogeneous interfaces, which results in an enhancement of interfacial polarization intensity. CNTs/PyC HMs with special hollow structure and a large number of heterogeneous interfaces exhibit excellent dielectric loss capability. When the thickness is 2.3 mm and reaction temperature is 650 °C, the minimum reflection coefficient is −56 dB and the effective absorption bandwidth reaches 4 GHz. The polarization loss induced by heterogeneous interfaces is an important avenue to enhance electromagnetic wave absorption properties, and a design strategy of interfacial polarization dominant electromagnetic wave absorbing material is explored.