Synthesis and characterization of magnetic nanoparticles coated with silica through a sol-gel approach

Abstract

This paper investigates the influence of reaction medium pH on silica-coating of magnetite nanoparticles. Magnetite nanoparticles were prepared by means of a reduction-precipitation method using ferric chloride as a starting material, which was partially reduced to ferrous salts by Na2SO3 before alkalinizing with ammonia. The particles were coated by sol-gel method with either ammonia or HCl aqueous solutions for either base- or acid-catalyzed hydrolysis, respectively. Powder X-ray diffraction, Fourier-transform infrared, and Zeta Potential were used for the characterization of oxides and of the coated magnetic nanoparticles. The observed difference of pH IEP in KCl solution for pure silica (2.0), magnetite (5.0), and silica-coated magnetite (2.3) samples confirms that the coating process was effective since the charge surface properties of coated magnetic nanoparticles are close to that of pure silica, even though the Fourier-transform infrared spectra did not evidence the formation of Fe-O-Si bonds.

X‐ray micro‐computed tomography analysis of accumulated corrosion products in deep‐water shipwrecks

“…In addition, it was found that the vibration band at 1,255 cm −1 is attributed to Fe‐O‐H bending modes in goethite . We are to state further that the peak at 1,023 cm −1 is represented as lepidocrocite . Going by the postulations in Tran et al, the characteristic band at 616 cm −1 could agree to the stretching and bending of Si–O bond for the silica .…”

Synthesis of agar-stabilized nanoscale zero-valent iron particles and removal study of hexavalent chromium

“…Strong bands at \900 cm -1 in the nZVI alone (Fig. 4b), attributable in part to iron oxides on the surface Andrade et al 2009), are weaker in the composite, indicating less oxidation of agar supported Fe 0 . The agar support may have reduced Fe (oxy) hydroxide formation, similar to the effect of montmorillon-ite-supported nZVI (Yuan et al 2009).…”

Magnetic, X-ray and Mössbauer studies on magnetite/maghemite core–shell nanostructures fabricated through an aqueous route

“…1 and 2). The IR absorption bands in the 630-550 cm À1 range is attributed to the vibrations of Fe-O bonds in tetrahedral and octahedral sites 59 and must have been resulted from the split of the n 1 band at $570 cm À1 .…”