Flexible electromagnetic shielding composites have a great potential for wide range applications. In this study, two flexible composites were produced by plating Ni nanoparticles on CNTs (Ni@CNT/SA/PDMS composites) or infiltrating CNF/PDMS polymer into CNT/SA sponge skeleton (CNT/SA/CNF/PDMS composites). The electromagnetic interference shielding effectiveness values of the above two composites are almost as twice as that of CNT/SA/PDMS composite at a same CNT loading. Introducing nano-sized Ni particles on CNT improved the microwave absorption capacity of the composite, while adding CNF on the PDMS matrix enhanced the conductivity of these composites. Under 10% strain, both flexible composites show stable conductivity. Simulation and calculation results shown that increasing the cladding rate of Ni nanoparticles on the surface of CNT, reducing the average size of Ni particles, and increasing the loading of CNF in PDMS matrix can significantly improve conductivity and then EMI performance of the materials. All of these could benefit for the design of flexible electromagnetic shielding composites.
A novel NiTi/vapor grown carbon fiber (VGCF)/polydimethylsiloxane flexible film is successfully prepared, of which the resistivity can keep stable under various strain deformation. By introducing NiTi particles with appropriate phase transition temperature, the resistivity change value of the composite in the temperature range can be doubled without affecting the flexibility of the composite. A computer simulation based on percolation network (PN) theory and Monte Carlo (MC) calculation is developed to understand the mechanisms of resistivity temperature curves. The simulation results agree with experiments quantitatively, which reveal that the inhomogeneous martensitic transformation of NiTi particles is a dominant mechanism for the enlarged and nonlinearity resistivity temperature variation of the composite. Parametric studies have been conducted and the calculation results show that selecting NiTi particles with smaller particle diameter, VGCF with higher conductivity, and polymer with larger coefficient of thermal expansion is conducive to further obtain flexible composite films with better temperature sensitivity.
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