Influence of FeSiAl content on the morphological evolution and electromagnetic properties of FeSiAl/CaO–B2O3–SiO2 microwave-absorbing coatings

CaO–B 2 O 3 –SiO 2 (CBS) is a promising lightweight, low-dielectric matrix material for high-temperature microwave-absorbing coatings. However, the comprehensive study of absorbent morphology evolution within such coatings and its influence on electromagnetic (EM) performance has not been conducted. In this work, a series of FeSiAl (FSA)/CBS composite coatings with various FSA contents were fabricated using atmospheric plasma spraying . The morphological evolution of the FSA phase and the resulting EM properties of the coatings were systematically analyzed. Experimental findings show that during the spraying process, when the size of FSA clusters in the composite powder exceeds the thickness of CBS splats, FSA clusters form a rigid contact with the underlying solidified coating, leading to the development of a lamellar structure . This lamellar FSA phase creates local conductive networks, which significantly increase the complex permittivity of the coating. These results provide valuable guidance for controlling absorbent morphology and optimizing the EM properties of CBS-based coatings.