Magnetic nanocomposite materials consisting of 5.5 wt% Fe-Co alloy nanoparticles in a silica aerogel matrix, with compositions Fe(x)Co(t-x) of x = 0.50 and 0.67, have been synthesized by the sol-gel method. The high-resolution transmission electron microscopy images show nanoparticles consisting of single crystal grains of body-centered cubic Fe-Co alloy, with typical crystal grain diameters of approximately 4 and 7 nm for Fe(0.5)Co(0.5) and Fe(0.67)Co(0.33) samples, respectively. The energy dispersive X-ray (EDX) spectra summed over areas of the samples gave compositions Fe(x)Co(t-x) with x = 0.48 +/- 0.06 and 0.68 +/- 0.05. The EDX spectra obtained with the 1.5 nm probe positioned at the centers of similar to 20 nanoparticles gave slightly lower concentrations of Fe, with means of < x > = 0.43 +/- 0.01 and < x > = 0.64 +/- 0.02, respectively. The Fe(0.5)Co(0.5) sample was studied using electron energy loss spectroscopy (EELS), and EELS spectra summed over whole nanoparticles gave x = 0.47 +/- 0.06. The EELS spectra front analysis profiles of nanoparticles show a distribution of Fe and Co that is homogeneous, i.e., x = 0.5, within a precision of at best +/- 0.05 in x and +/- 0.4 nm in position. The present microscopy results have not shown the presence of a thin layer of iron oxide, but this might be at the limit of detectability of the methods.
A Transmission Electron Microscopy Study of Fe-Co Alloy Nanoparticles in Silica Aerogel Matrix Using HREM, EDX, and EELS
FALQUI, ANDREA;CORRIAS, ANNA;
2009-01-01
Abstract
Magnetic nanocomposite materials consisting of 5.5 wt% Fe-Co alloy nanoparticles in a silica aerogel matrix, with compositions Fe(x)Co(t-x) of x = 0.50 and 0.67, have been synthesized by the sol-gel method. The high-resolution transmission electron microscopy images show nanoparticles consisting of single crystal grains of body-centered cubic Fe-Co alloy, with typical crystal grain diameters of approximately 4 and 7 nm for Fe(0.5)Co(0.5) and Fe(0.67)Co(0.33) samples, respectively. The energy dispersive X-ray (EDX) spectra summed over areas of the samples gave compositions Fe(x)Co(t-x) with x = 0.48 +/- 0.06 and 0.68 +/- 0.05. The EDX spectra obtained with the 1.5 nm probe positioned at the centers of similar to 20 nanoparticles gave slightly lower concentrations of Fe, with means of < x > = 0.43 +/- 0.01 and < x > = 0.64 +/- 0.02, respectively. The Fe(0.5)Co(0.5) sample was studied using electron energy loss spectroscopy (EELS), and EELS spectra summed over whole nanoparticles gave x = 0.47 +/- 0.06. The EELS spectra front analysis profiles of nanoparticles show a distribution of Fe and Co that is homogeneous, i.e., x = 0.5, within a precision of at best +/- 0.05 in x and +/- 0.4 nm in position. The present microscopy results have not shown the presence of a thin layer of iron oxide, but this might be at the limit of detectability of the methods.
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