Synthesis And Application Of Fe₃O₄/SWCNHs Composite

Single-walled carbon nanohorns（SWCNHs） has attracted an increasing attention because of its unique physical and chemical properties. Speci ally, it was used as a support to load the other nanoparticles or drug molecules. Magnetite, a resourceful ferromagnetic material with the advantages of good magnetism, hypotoxicity and low cost, usually has been applied to the bio-pharmaceutical, catalysis, microwave absorption and so on. Meanwhile, it can be easily separated for recycling utilization using a magnet. In this article, we produce the SWCNHs by arcdischarge evaporation and process it with mixed acid. A lot of oxygen-containing groups are generated on the surface of SWCNHs after oxidization, thereby a high dispersion of SWCNHs solution can be obtained. Fe₃O₄ nanoparticles were prepared through thermal decomposition method. Fe₃O₄/SWCNHs composite was obtained through the combination of Fe₃O₄ and the oxygen-containing groups of SWCNHs. Based on the characterization of morphology, chemical structure, magnetism, electromagnetic parameter and catalytic performance of Fe 3O4/SWCNHs composite, we studied its microwave absorption and Fenton catalytic properties. The main research results are as follows:（1） The morphologies and structures of samples were characterized by TEM, XRD and FTIR. The results showed that the as-prepared SWCNHs was dahlia-like structure. After oxidation by mixed acid, a mass of defects appeared at the top of horns due to the generation of vast hydrophilic groups. Simultaneously, the oxidized SWCNHs could uniformly disperse in water and did not deposit. In addition, the Fe₃O₄ nanoparticles in the size of 8-10 nm were loaded on the surface of SWCNHs dispersedly.（2） The electromagnetic parameters of each sample with different Fe 3O4 content were measured on a vector network analyzer. Through theoretical calculation and data analysis, we studied the microwave absorption and the absorbing mechanism of the composites. The results showed when the Fe₃O₄ content was 35.6%, the composite displayed a significantly enhanced microwave absorption ability because of the improved impedance matching, electric polarization and interfacial polarization. Specifically, the maximum reflection loss of this composite with a thickness of 5.8mm is-38.84 d B at 3.72 GHz in the S-band. The bandwidth of absorption exceeding 10 d B is 9.2GHz（from 3.2GHz to 12.4 GHz） with an absorber thickness of 2–6mm.（3） Orange II was degraded with H₂O₂ by using Fe₃O₄/SWCNHs composite as catalyst and its concentration in the different reaction time was investigated by a UV-VIS spectrophotometer. We found that the catalytic activity of the composite was far better than that of pure Fe₃O₄ nanoparticles. At the same time, we acquired the optimal condition by discussing the effects of Fe₃O₄ content, p H, H2O2 and catalyst concentration.