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Xiang Wen,Lizhen Hou,Lianwen Deng,Daitao Kuang,Heng Luo,Shiliang Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.7
CoNi magnetic nanoparticles (NPs) and hybrid architectures have attracted tremendous attention from numerous applications. In this study, a facile approach based on one-step metal-organic chemical vapor deposition (MOCVD) was developed to fabricate CoNi/C core/shell NPs with an extremely small core size of ~3.7 nm and an ultrathin shell thickness of 1–3 nm. Only 10 wt.% CoNi/C core/shell NP-filled composites with thickness of 1.6 mm exhibit an optimal reflection loss value of -25.7 dB and an absorbing bandwidth value up to 6.2 GHz. The extremely small core/shell NPs are demonstrated to have enhanced electromagnetic parameters (i.e., complex permittivity and permeability), reflection loss and broadened effective absorption bandwidth, as compared to the relatively larger NPs. The superior microwave absorbing performance should be attributed to the increased specific area with enriched interfacial polarization. The as-synthesized extremely small CoNi/C core/shell NPs are expected to be a fascinating candidate for efficient microwave absorption material with lightweight and thin thickness.
Zhang Xuejun,Peng Sen,Huang Han,Guo Xiao,Boukhachem Abdelwaheb,Deng Lianwen 한국물리학회 2023 Current Applied Physics Vol.50 No.-
The infrared emissivity of Co doped α-MoO3 was tested, and the resistivity was tested according to the relationship between infrared emissivity and electrical conductivity. In order to further explore the influencing factors of infrared emissivity, the oxygen vacancy concentration was tested according to the relationship between electrical conductivity and oxygen vacancy. It is found that annealing temperature has a significant effect on the infrared emissivity of Co doped α-MoO3. The infrared emissivity, resistivity and oxygen vacancy concentration first decrease and then increase with the increase of annealing temperature. The infrared emissivity is the minimum when the annealing temperature is 500 ◦C. The oxygen vacancy concentration is characterized and analyzed by XPS and Raman. The results show that the oxygen vacancy concentration can be changed by controlling the annealing temperature, thus the conductivity can be changed, and the infrared emission can be controlled.