Yan Liao,Dashuang Wang,Wenrui Zhu,Zhilan Du,Fanbo Gong,Tuo Ping,Jinsong Rao,Yuxin Zhang,Xiaoying Liu
Transition metal oxides have been widely used in microwave-absorbing materials, but how to improve impedance matching is still an urgent problem. Therefore, we introduced urea as a polymer carbon source into a three-dimensional porous structure modified by Co3O4nanoparticles and explored the influence of different heat treatment temperatures on the wave absorption properties of the composite. The nanomaterials, when calcined at a temperature of 450 °C, exhibited excellent microwave absorption capabilities. Specifically, at an optimized thickness of 9 mm, they achieved a minimum reflection loss (RLmin) of −97.3 dB, accompanied by an effective absorption bandwidth (EAB) of 9.83 GHz that comprehensively covered both the S and Ku frequency bands. On the other hand, with a thickness of 3 mm, the RLminwas recorded as −17.9 dB, with an EAB of 5.53 GHz. This excellent performance is attributed to the multi-facial polarization and multiple reflections induced by the magnetic loss capability of Co3O4nanoparticles, the electrical conductivity of C, and the unique three-dimensional structure of diatomite. For the future development of bio-based microwave absorption, this work provides a methodology and strategy.
Jin-Cheng Shu,Si-Qi Zhu,Wen-Qiang Cao,Mao-Sheng Cao
A multi-functional electromagnetic (EM) device is an important pillar for promoting the progress of an intelligent society. Herein, a ZIF-67 nanoneedle array assembled on a nickel substrate is used as a precursor to construct a C/Co3O4 nanoarray via a simple thermal treatment approach, integrating the two functions of EM and thermal shielding. Its unique three-dimensional porous structure and integrated components endow this material with an average shielding efficiency of 99.62% and a maximum temperature difference of about 25 K. In addition, this skeleton structure features light weight, low density and small cost, which can be utilized to construct wearable devices to protect human beings from EM and thermal radiation. This study furnishes a novel horizon for the design and construction of multi-functional and wearable EM devices, and promotes the development of the EM field and the progress of multi-disciplinary technologies.
Persulfate-based advanced oxidation process (PS-AOP) is a promising technology for in-depth wastewater treatment. Here, Co 3 O 4 quantum dots (QDs) decorated hierarchical C@Co 3 O 4 (C@Co 3 O 4 -Q5) was prepared by a facile route. The crystalline structure, micrograph and chemical composition of C@Co 3 O 4 -Q5 were characterized by XRD, SEM, TEM and XPS. Taking Rhodamine B (RhB) as a model contaminant, the influences of process parameters on the degradation performance were evaluated. Detailed reaction kinetics investigation indicated that, at elevated temperatures higher than 30 °C, RhB degradation rate approximately follows this expression: r = 1.022 × 1 0 7 e x p ( - 47850 / R T ) [ R h B ] [ P M S ] 0.36 , whereas the real energies for catalytic activation ( Eac ) and heat activation ( Eah ) were 16.231 kJ·mol −1 and 31.62 kJ·mol −1 , respectively. Reactive oxygen species (ROS) quenching experiments and EPR tests suggested that not the general held radical SO 4 − but the downstream OH and the nonradical ROS 1 O 2 co-contribute to RhB mineralization. Meanwhile, PMS activation mechanisms referring to OH and 1 O 2 generation were elaborated based on XPS discussion. It was revealed that Co 3 O 4 quantum dots and oxygen functional groups and/or oxygen defects on carbon surface cooperate to generate ROS. Additionally, 5 successive cycles confirmed C@Co 3 O 4 -Q5′s high stability and reusability. These findings provided new insights into carbon-loaded QDs catalysts for PMS-mediated micropollutants removal.
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