Enhanced antioxidation and microwave absorbing properties of SiO2-coated flaky carbonyl iron particles

Highlights: • SiO₂-coated carbonyl iron particles were prepared by chemical bath deposition method. • The obvious weight gain of carbonyl iron was deferred to 360 °C after SiO₂-coated. • The permeability of the SiO₂-coated particle composite kept almost invariable. • SiO₂-coated carbonyl iron composite reserves a better absorption after heat treatment. SiO₂ was successfully coated on the surface of flaky carbonyl iron particles using a chemical bath deposition method in the presence of 3-aminopropyl triethoxysilane (APTES). The morphologies, composition, valence states of elements, as well as antioxidation and electromagnetic properties of the samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and microwave network analyzer. TG curve shows the obvious weight gain of carbonyl iron was deferred to 360 °C after SiO₂-coated, which can be ascribed to the exits of SiO₂ overlayer. Compared with the raw carbonyl iron, SiO₂-coated sample shows good wave absorption performance due to its impedance matching. The electromagnetic properties of raw and SiO₂-coated carbonyl iron particles were characterized in X band before and after heat treatment at 250 °C for 10 h. It was established that SiO₂-coated carbonyl iron demonstrate good thermal stability, indicating SiO₂-coating is useful in the usage of microwave absorbers operating at temperature up to 250 °C.