Interface Engineering Strategy in Bimetallic Carbide and Cobalt Nanoparticles Encapsulated in N-Doped Carbon Nanotubes for Excellent Microwave Absorption

Abstract

In this paper, bimetallic Zn/Co zeolitic imidazole frameworks (Zn/Co-ZIFs) with various Zn/Co ratios have been successfully synthesized via a facile coprecipitation method, and then were converted into a series of N-doped bamboo-like carbon nanotubes (CNTs) encapsulated in Co nanoparticles with the aid of dicyandiamide after an annealing process. Results show that when the Zn/Co ratios in the Zn/Co-ZIF are 2:1 and 1:2, the morphology of ZIFs is hexagonal-star-like shape while it presents rod-like shape at the Zn/Co ratio of 1:1. The corresponding derivatives of these ZIFs after carbonization are identified as Co3ZnC/Co@CNTs, Co@CNTs-12, and Co@CNTs-11, and their microwave absorption performances are investigated at the same time. Among these as-synthesized composites, Co3ZnC/Co@CNTs shows the best microwave absorption behavior with a minimum reflection loss (RLmin) of -65.3 dB and an effective absorption bandwidth (EAB) of 5.3 GHz at a low filler content of 15 wt% and a thickness of 2.2 mm. Moreover, using CST to analyze Co3ZnC/Co@CNTs the radar cross section (RCS) was simulated, and the reduction value of RCS was -31.95 dB m2, and effective absorption can achieve full angle coverage. The outstanding microwave absorption capabilities of Co3ZnC/Co@CNTs can be credited to the effective impedance matching, robust interface polarization, and significant conduction loss. This paper also provides a strategy for strengthening the microwave absorption ability of absorbers through the interface engineering.

Keywords: Bimetallic ZIFs, Dielectric loss, Magnetic loss, Microwave absorption, Interfacial engineering