期刊
CHEMICAL ENGINEERING JOURNAL
卷 396, 期 -, 页码 -出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2020.125205
关键词
Microwave absorption; CoO/Co3O4 particles; Annealing; Nanoneedle structure; Phase and morphology evolution
资金
- Key Laboratory of Biomedical Effects of Nanomaterials and Nanosafety, Chinese Academy of Sciences [NSKF201908]
Novel dual phased CoO/Co3O4 particles with Co3O4 nanoneedles on surface are obtained by annealing dual-phased Co (hexagonal and cubic phases) particles. Their phase and morphology evolution are clarified by XRD, SEM and TEM measurements. The early formed CoO and Co3O4 on surface from dual-phased Co promote the outdiffusion process of inside Co with kirkendall effect and restrict the growth of Co3O4 with a specific orientation, leading to the formation of Co3O4 nanoneedles on the surface. The microwave absorption measurement shows that the CoO/Co3O4 particles with annealing time of 1 h possess higher permittivity and better performances than pure Co and Co3O4 particles. An enhanced reflection loss (RL) value of - 38.8 dB is obtained for the CoO/Co3O4-paraffin wax (PW) composite with a thickness of 2.8 mm. The absorption bandwidth for RL below -10 dB reaches 8.7 GHz. The Co3O4 nanoneedles on surface, porous structure and inner dual phased CoO/Co3O4 bring increased multiple reflection, interface/dipolar polarizations, conductive loss and better impedance matching. This clarification of phase and morphology evolution and novel CoO/Co3O4 material with nanoneedles on surface may provide new routes for designing high performance Co-based microwave absorbers with unique structures.
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