Decoration of Fe_3O_4 nanoparticles on the surface of poly(acrylic acid) functionalized multi-walled carbon nanotubes by covalent bonding

摘要

Fe_3O_4 nanoparticles were indirectly implanted onto functionalized multi-walled carbon nanotubes (MWCNTs) leading to a nanocomposite with stronger magnetic performance. Poly(acrylic acid) (PAA) oligomer was first reacted with hydroxyl-functionalized MWCNTs (MWCNTs-OH) forming PAA-grafted MWCNTs (PAA-g-MWCNTs). Subsequently, Fe_3O_4 nanoparticles were attached onto the surface of PAA-g-MWCNTs through an amidation reaction between the amino groups on the surface of Fe_3O_4 nanoparticles and the carboxyl groups of PAA. Fourier transform infrared spectra confirmed that the Fe_3O_4 nanoparticles and PAA-g-MWCNTs were indeed chemically linked. The morphology of the nanocomposites was characterized using transmission electron microscope (TEM). The surface and bulk structure of the nanocomposites were examined using X-ray diffraction, X-ray photoelectron spectrometer (XPS), and thermogravimetric analysis (TGA). The magnetic performance was characterized by vibrating sample magnetometer (VSM) and the magnetic saturation value of the magnetic nanocomposites was 47 emu g~(-1). The resulting products could be separated from deionized water under an external magnetic field within about 15 s. Finally, the magnetorheological (MR) performances of the synthesized magnetic nanocomposites and pure Fe_3O_4 nanoparticles were examined using a rotational rheometer.