Constructing 3D cross-connected networks in spongy MgO/Ni/MWCNT composites to synchronously boost microwave absorption and thermal conductivity

Abstract

To address the issues of electromagnetic (EM) radiation and waste heat engendered in modern electrics, we pioneer the utilization of 3D cross-connected MgO/Ni/MWCNT networks as a magnetic-dielectric-dual-loss filler with electron-phonon dual thermal carriers to synchronously boost EMW absorption and thermal conductivity. The carbothermic reduction of magnesium oxalate/nickel oxalate core-shell hexahedra produced from a cryogenic precipitation/precipitate transfer route causes the in-situ self-catalytic growth of MWCNTs on the surfaces of porous MgO/Ni composites. The component, microstructure, and texture of the composites and their resulting performance can be tuned by some dynamic factors (i.e., [Ni2+], Ts, etc.). The spongy MgO/Ni/MWCNT composites formed under [Ni2+] = 1.6 M and Ts = 600 ℃ exhibit the optimal EMW absorption and thermal conductivity. Compared with the most previously reported materials, they have a larger thermal conductivity (3.61 W/(m⋅K)), a larger EAB/d value (∼4.61 GHz/mm), stronger absorption (−51.33 dB), and a smaller thickness (1.7 mm). The synchronously enhanced properties are attributed to magnetic/dielectric dual losses, electron/phonons dual thermal carriers, and 3D interconnected networks in MgO/Ni/MWCNT composites, which generate the strong attenuation, good low-frequency matching performance, and continuous heat transfer path. Noteworthy, spongy MgO/Ni/MWCNT composites are promising as a multifunctional filler to address the issues of EMI and thermal dissipation.