High-Temperature Oxidation-Resistant ZrN_0.4B_0.6/SiC Nanohybrid for Enhanced Microwave Absorption

Most microwave absorbers lose their function under harsh working conditions, such as a high temperature and an oxidative environment. Here, we developed a heterogeneous ZrN_0.4B_0.6/SiC nanohybrid via combined catalytic chemical vapor deposition (CCVD) and chemical vapor infiltration (CVI) processes using ZrB₂ as the starting material. The composition and structure of the ZrN_0.4B_0.6/SiC nanohybrid were controlled by tuning the CCVD and CVI parameters, such as reaction temperature, time, and reactant concentration. The optimal heterogeneous ZrN_0.4B_0.6/SiC nanohybrids were obtained initially by preparing ZrB₂@C via the CCVD process at 650 °C for 30 min and the subsequent CVI at 1500 °C, where the ZrB₂@C reacted with Si under N₂. The ZrN_0.4B_0.6/SiC nanohybrid exhibited enhanced microwave absorption ability with a minimum reflection loss value of approximately -50.8 dB at 7.7 GHz, a thickness of ∼3.05 mm, and antioxidation features at a high temperature of 600 °C. The heterogeneous ZrN_0.4B_0.6/SiC nanohybrid possessed reasonable conductivity, leading to dielectric loss, whereas SiC nanofibers formed a three-dimensional network that brought higher dipole moments, whereas a small part of the ZrN_0.4B_0.6/SiC nanohybrid structure generated an effective interface for higher attenuation of microwaves. Therefore, these material features synergistically resulted in a well-defined Debye relaxation, Maxwell-Wagner relaxation, dipole polarization, and the quarter-wavelength cancellation, which accounted for the enhanced microwave absorption.