RESUMO
Developing composite materials with the synergistic effects of heterogeneous structures and multiple components is considered as a promising strategy to achieve high-performance electromagnetic wave (EMW) absorbers. To further satisfy the demand of broadband and strong microwave absorption, a novel NiS/carbon nanofibers (CNFs)/porous carbon composite is successfully synthesized by hydrothermal and chemical vapor deposition using lotus leaves as a biomass carbon source. A few carbon nanotubes (CNTs) and uniformly dispersed Ni nanocrystals have also been found in the hybrid. Benefiting from the porous structure derived from lotus leaves, the combination of dielectric NiS, conductive carbon nanomaterials, and magnetic Ni nanoparticles, together with the three-dimensional conductive network of CNFs and CNTs, the remarkable EMW absorption properties with a minimum reflection loss up to -67.65 dB have been achieved at merely 2.32 mm. Besides, the widest effective absorption band can reach 5.9 GHz with a thin thickness of 2.07 mm, covering almost the entire Ku band. In addition, under the incident angle of 31°, the radar cross-section reduction value of LNSF-600 can reach 42.88 dBm2. Therefore, this work provides an efficient and facile method for manufacturing outstanding biomass-derived EMW absorbers.
RESUMO
Carbon fiber composites as pantograph slide materials are in the development stage, in which copper is the conductive phase, and the addition form and size need to be designed. Herein, the effects of the copper morphology, the size of the copper mesh on the performance, and the influence of the contact mode between the sliding plate and bracket on the temperature rise were compared and analyzed. The resistivity is 11.2 µΩ·m with the addition of 20 wt% copper mesh, a relative reduction of 91.77%. Importantly, the impact strength is increased by 14.19%, and the wear is reduced by 13.21%; hence, the copper mesh laid in layers is the ideal structure. Further study of the distribution and quality of the copper mesh shows that the resistivity is related only to the quality of the copper mesh; in addition, the number of layers of the copper mesh cannot exceed 16, and it is determined that the best type of copper mesh is 5#. Notably, the performance can be improved by appropriately reducing the thickness of the copper mesh and increasing the aperture while the sliding plate and the bracket are connected by copper mesh with conductive adhesive, which has the slowest heating rate of 2.27 °C/min and the smallest resistance. Therefore, the influence of copper content and distribution on the electrical conductivity are systematically investigated, and the mechanical properties and electrical conductivity are optimized through the design of the laminate structure of the compound material.
