To solve the pollution problem of electromagnetic waves, new electromagnetic shielding materials should meet the requirements of being lightweight with high electrical conductivity. In this work, the combination of silver (Ag) nanoparticles and nitrogen doping (N-doping) was expected to tune the electromagnetic and physical properties of Ti₃C₂T_x MXene, and the Ag@N-Ti₃C₂T_x composites were fabricated through the hydrothermal reactions. The nitrogen doped (N-doped) Ag@Ti₃C₂T_x composites showed a hollow structure with a pore size of 5 μm. The influence of N-doped degrees on the electromagnetic interference (EMI) shielding performance was investigated over 8–18 GHz. Therefore, the controlled N-doping composites exhibited reflection-based EMI shielding performance due to the electrical conductivity and the special three-dimensional (3D) honeycomb-like structure. The achieved average EMI shielding values were 52.38 dB at the X-band and 72.72 dB at the K_u-band. Overall, the Ag@N-Ti₃C₂T_x foam, due to its special 3D honeycomb-like structure, not only meets the characteristics of light weight, but also exhibits ultra-high-efficiency EMI shielding performance, revealing great prospects in the application of electromagnetic wave shielding field.

Lightweight corundum-mullite thermal insulation materials were successfully prepared by microwave sintering at low temperature. The effects of sintering temperatures, PMMA microspheres and SiC particles on structure and properties of as-prepared corundum-mullite materials were investigated. The SiC became a hot spot under the action of microwave field, and these local high temperature areas promoted the formation and growth of mullite whiskers. The PMMA microspheres were burn out, leaving pores which could provide space for the growth of mullite whiskers. It was found that the optimal sintering temperature was 1400?C and corresponding porosity, density and bending strength of the samples were 71.2%, 0.99 g/cm3 and 3.85MPa, respectively. The thermal conductivity was from 0.201 to 0.313W/(m?K) between 30?C and 950?C. This work demonstrated that lightweight corundum-mullite materials with low density, high porosity, good thermal shock resistance and excellent thermal insulation properties could be successfully prepared by microwave sintering.