Effects of MOFs-derived Ni@NC/CNT nanocomposites on impermeability and microwave absorption of modified epoxy resin coatings on cement-based materials

Abstract

Human health and information security are harmed by electromagnetic wave (EMW) energy’s constant increase and various reflections. In this study, Metal-organic frameworks (MOFs) derived metal nickel@nitrogen-doped porous carbon/carbon nanotube (Ni@NC/CNT) nanocomposites with excellent EMW absorption performance were utilized to modify epoxy resin coatings on the cement-based materials. Surprisingly, when the dosage is 3 wt%, the cement-based materials coated with the modified epoxy resin coatings show outstanding permeability resistance and EMW absorption properties. The capillary water absorption coefficient and the chloride ion diffusion coefficient are 37.583 and 2.42 × 10-12 m2 s−1, which are 88.05% and 73.2% respectively lower than that of the uncoated specimen. The excellent EMW absorption performance was concretely manifested that the minimum reflection loss (RLmin) value is −45.76 dB, the effective absorption bandwidth (EAB) value is 12.88 GHz, and the effective practical application bandwidth (EPB) value is 15.04 GHz. Additionally, the modified epoxy resin coatings also exhibit exceptional thermal stability and mechanical properties, which are further analyzed with TGA and SEM results. These outstanding properties are attributed to the good compatibility between Ni@NC/CNT nanocomposites and epoxy resin, higher cross-linking densities, favorable nano-size effect, and the excellent EMW performance of Ni@NC/CNT nanocomposites. This work is extremely helpful for improving EMW absorption and other properties of epoxy resin coatings on cement-based materials.