Transformation between nanosheets and nanowires structure in MnO2 upon providing Co2+ ions and applications for microwave absorption
phase transitions, self-assembly, impedance matching, microwave absorption
The phase transition process of the MnO2 phase with increases in Co2+ doping can be described by the Ouroboros symbol. The undoped sample is pure δ-MnO2 with nanosheets structures. Then a small amount of Co2+ ions changes the final products and generates α-MnO2 nanofibres in the δ-MnO2 matrix. The products become pure α-MnO2 with an appropriate amount of Co added. However, when the Co amount continues to increase, the amount of α-MnO2 decreases in the products and turns back to form pure δ-MnO2 in the end. Analysing the electromagnetic absorption performance, the relationship between the properties and the proportion of δ-MnO2/α-MnO2 in the powders adjusted by Co2+ doping has been explored, and the composites of δ-/α-MnO2 show better absorption ability than the single-phase samples. As a result, the optimal reflection loss (RL) is –54.8 dB, and the effective absorption bandwidth can cover the Ku band at a thickness of 2.2 mm and the X band at a thickness of 3.1 mm with 50 wt.% filler loading ratios. This research might shed new light on the improvement of novel microwave absorption materials.
Tsinghua University Press
Lulu Song,Yuping Duan,Jia Liu,Huifang Pang, Transformation between nanosheets and nanowires structure in MnO2 upon providing Co2+ ions and applications for microwave absorption. NanoRes.2020, 13(1): 95–104