Influence of crystalline phase evolution of shells on microwave absorption performance of core-shell Fe3O4@TiO2 nanochains

Core-shell electromagnetic nanostructures with dielectric-magnetic dual-loss mechanisms are promising candidates for highly efficient microwave absorption attenuation. Herein, chain-like Fe3O4@TiO2 nanomaterials have been first prepared, and the crystalline phase composition of TiO2 shells has been regulated through controlling the sintering temperatures as 450 °C, 550 °C, and 650 °C. According to XRD patterns, the components of Fe3O4, TiO2, and FeTiO3 are ascertained, and the proportion of amorphous, anatase, and rutile phases is approximately determined. XPS results confirm the existence of Ti4+ and absence of oxygen vacancy in three samples. Investigation of microwave absorption properties indicates that S650 can possess the minimum reflection loss value of −21.29 dB (5.58 GHz) and the maximum effective absorption bandwidth of 5.09 GHz (11.83–16.92 GHz), superior than two other samples. Analyses of electromagnetic parameters reveal that dielectric loss plays a major role in the microwave absorption, heterogeneous interfaces are more conducive to strengthening dielectric loss than heterophase interfaces in the TiO2 shells, and increasing crystal phases is beneficial for improving impedance matching. This work first reports the influence of crystalline phase evolution on dielectric loss and impedance matching, which delivers a new approach to optimize the microwave absorption performance.