Dependency of tunable microwave absorption performance on morphology-controlled hierarchical shells for core-shell Fe3O4@MnO2 composite microspheres

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 304; pp. 552 - 562
• Main Authors: Qiao, Mingtao, Lei, Xingfeng, Ma, Yong, Tian, Lidong, Su, Kehe, Zhang, Qiuyu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.11.2016
• Subjects: Core-shell; Fe3O4; Hierarchical structure; Microwave absorption; MnO2; Fe3O4; MnO2; Microwave absorption; Core-shell; Hierarchical structure
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2016.06.094

[Display omitted] •Hierarchical core-shell Fe3O4@MnO2 composite microspheres have been synthesized.•The mushroom, honeycomb and corolla-like morphologies of composites are controlled.•Tailoring microwave absorption performance depends on various hierarchical shells.•Suitable surface area and pore volume conduce to improving absorbing capability.•Corolla-like composites possess the strongest absorption of −48.5dB (11.2GHz). Core-shell Fe3O4@MnO2 composite microspheres with three different surface architectures, namely mushroom-, honeycomb- and corolla-like morphologies, have been synthesized through a facile two-step method. The components, microstructure, size and morphologies of composite microspheres were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The N2 adsorption-desorption isotherms were employed to demonstrate the specific surface areas and porosity. Moreover, vibrating sample magnetometer results manifest that these three composites possess the specific saturation magnetization of 33.7emu/g, 27.2emu/g and 23.0emu/g, respectively. Investigations of microwave absorbing properties indicate that both mushroom-like and corolla-like Fe3O4@MnO2 composite microspheres have very broad absorbing bandwidth in the frequency range of 2–18GHz, and the corolla-like composites exhibit the strongest absorbing capability with the minimum reflection loss value of −48.5dB (11.2GHz), which has rarely been reported yet. In addition, analysis of microwave absorption mechanism reveals that electromagnetic energy absorption mainly derives from matching impedance, conductive loss, multiple scattering and absorption in the cavities, and interfacial polarizations between Fe3O4 cores and MnO2 shells in the composites. Therefore, it is believed that hierarchically structured dielectric shells contribute to the enhancement of microwave absorption performance.