The analysis of materials using Fourier transform infrared (FTIR) spectroscopy has a unique area called the fingerprint region for each compound. However, this area is almost never discussed because of its complexity due to the large number of signals that appear in it. In this work, the fingerprint region analysis of the ethylene–vinyl acetate copolymer (EVA) with different percentages of vinyl acetate (VA) (18%, 28%, 40%) was performed. In comparison with other instrumental techniques, the crystallinity and structural arrangement of the EVA copolymers were determined simply and economically. The crystallinities for EVA18, EVA28 and EVA40 were 24.39%, 6.95% and1.03%, respectively. In terms of structural ordering, the number of linear chains of EVA copolymer decreases as the concentration of VA increases, which favors the reduction of degrees of freedom and the formation of hydrogen bonds.
Nanocomposites of reduced graphene oxide (RGO) with ferromagnetic α-Fe2O3 nanoparticles have been prepared in-situ by thermal treatment. The structure and morphology of the hybrid material were studied by X-ray photoelectron spectroscopy, Raman, X-ray diffraction, and transmission electron microscopy. The results show a hybrid material highly modified with α-Fe2O3 nanoparticles distributed on the graphene surface. The adsorption kinetics show the presence of α-Fe2O3 nanoparticles on the RGO surface, and the amount of remaining functional groups dominated by ionization and dispersion. The adsorption kinetics of this adsorbent was characterized and found to fit the pseudo-second-order model. The α-Fe2O3 nanoparticles on RGO modify the electrostatic interaction of RGO layers and tetracycline, and adsorption properties decreased in the hybrid material. Adsorption isotherms fit with the Langmuir model very well, and the maximum capacity adsorption was 44.23 mg/g for RGO and 18.47 mg/g for the hybrid material. Magnetic characterization of the hybrid material shows ferromagnetic behavior due to the nanosize of α-Fe2O3 with a saturation magnetization, Ms = 7.15 Am2/kg, a remanence Mr = 2.29 Am2/kg, and a coercive field, Hc = 0.02 T.
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