Three dimensional porous MXene/CNTs microspheres: Preparation, characterization and microwave absorbing properties

•Three dimensional porous MXene/CNTs microspheres (C-MCM) are first developed.•The folded microspheres are formed by simple and rapid ultrasonic spray technology.•C-MCM have large specific surface area and abundant pores.•The optimal ratio of MXene and CNTs in C-MCM is verified.•The RLmin of C-MCM is −45 dB@10 GHz with a thickness of 2.7 mm. In this paper, a simple ultrasonic spray technology is used to assemble one-dimensional (1D) carboxylated carbon nanotubes (C-CNTs) and two-dimensional (2D) Ti3C2Tx MXene nanosheets into three-dimensional (3D) porous MXene/C-CNTs microspheres (MCM). After vacuum carbonization, C-MCM with excellent microwave absorbing properties are obtained. It finds that the synergy of MXene and CNTs makes C-MCM have good impedance matching and microwave attenuation capabilities. Under the best mass ratio (MXene: CNTs = 3:1) and filler content (30%), the minimum reflection loss (RLmin) is −45 dB@10 GHz, and the corresponding matching thickness is 2.7 mm. When the thickness is 1.9 mm, the effective absorption bandwidth (EAB) reaches 4.9 GHz. By adjusting the thickness of the absorber, almost all electromagnetic waves in the C, X and Ku bands can be completely absorbed. Therefore, C-MCM provides a new way to manufacture electromagnetic wave absorbers with light weight, thin thickness, high efficiency and broadband.