Phase and morphology evolution of high dielectric CoO/Co3O4 particles with Co3O4 nanoneedles on surface for excellent microwave absorption application

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2020-09, Vol.396, p.125205, Article 125205
• Main Authors: Xie, XiuBo, Ni, Cui, Lin, Zihan, Wu, Dan, Sun, Xueqin, Zhang, Yuping, Wang, Bing, Du, Wei
• Format: Article
• Language: English
• Subjects: Annealing; CoO/Co3O4 particles; Microwave absorption; Nanoneedle structure; Phase and morphology evolution
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2020.125205

[Display omitted] •Novel dual phased CoO/Co3O4 particles with Co3O4 nanoneedles on surface are obtained.•Their phase and morphology evolution are clarified.•The CoO/Co3O4 particles show large bandwidth of 8.7 GHz for RL value below −10 dB.•The nanoneedles, porous structure and CoO/Co3O4 are beneficial for high properties. 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.