Decorating untreated carbon nanotubes with Fe3O4@SiO2 nanoparticles and its microwave absorption property

Abstract

In order to decorate carbon nanotubes, we must pass through the functionalization stage. Acid treatment is a common method of modifying the surface of carbon nanotubes to make them suitable for accepting other nano-objects. Since, acidic functionalization of carbon nanotubes creates many defects in its structure, leads to lose most of their superior physical properties such as thermal conductivity, electrical conductivity and mechanical strength. On another hand, untreated multi-walled carbon nanotubes (UTCNTs) have a weak ability to be decorated with other nanomaterials due to the absence of a sufficient amount of functional groups. Therefore, it is very important to plan some strategy to solve this problem. Here, we propose a new approach to decorate non-functionalized carbon nanotubes by magnetic attraction. First, UTCNTs are decorated by small amounts of Fe3O4 nanoparticles (Fe3O4-UTCNTs). Next, the magnetically modified MWCNTs (Fe3O4-UTCNTs) are decorated by Fe3O4@SiO2 core-shell nanoparticles via magnetic attraction between these two magnetic components (Fe3O4-UTCNTs and Fe3O4@SiO2). We prepared three Fe3O4@SiO2/Fe3O4-UTCNTs samples with different weight ratios of Fe3O4-UTCNTs to Fe3O4@SiO2 core-shell nanoparticles, named S1 [1:0.5], S2 [1:1], and S3 [1:2.5]. The saturation magnetization of S1, S2 and S3 are 35.27, 44.45 and 57.68 emu/g, respectively. All samples which were characterized by FT-IR spectroscopy, X-Ray diffraction, scanning and transmission electron microscopy, applied as a microwave absorber. After measuring the electromagnetic parameters of each sample and calculating their reflection losses (RLs), we found that all samples exhibit strong RLs (between −33 and −50 dB) and wide absorption bands (between 7.2 and 8.1 GHz), with low thicknesses of 1–3 mm, at the range of 2–12 and 8–12 GHz. The results also show that, by increasing the weight ratio of Fe3O4@SiO2 core-shell in the composite, the minimum RL increases for some thicknesses of samples, while the absorption band widths are broadened for all thicknesses.