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Research is presented describing the effect of using extended X-ray absorption fine structure and X-ray absorption near edge structure on the structural evolution of nanocomposites composed of nickel oxide nanoparticles in an amorphous silica matrix using the sol-gel method.

The structure and the magnetic properties of a series of Fe2O3-SiO2 nanocomposites prepared by sol-gel method and submitted to thermal treatments in the temperature range 300-900 degrees Celsius, were investigated using a multitechnique approach. Findings indicate that the saturation magnetization lowers in the samples with higher Fe2O3 content. Interparticle interactions also contribute to the decrease as shown by fitting magnetic susceptibility values versus temperature.

The magnetic properties of cobalt ferrite–silica nanocomposites with different concentrations (15, 30, and 50 wt %) and sizes (7, 16, and 28 nm) of ferrite particles have been studied by static magnetization measurements and Mössbauer spectroscopy. The results indicate a superparamagnetic behavior of the nanoparticles, with weak interactions slightly increasing with the cobalt ferrite content and with the particle size. From high-field Mössbauer spectra at low temperatures, the cationic distribution and the degree of spin canting have been estimated and both parameters are only slightly dependent on the particle size. The magnetic anisotropy constant increases with decreasing particle size, but in contrast to many other systems, the cobalt ferrite nanoparticles are found to have an anisotropy constant that is smaller than the bulk value. This can be explained by the distribution of the cations. The weak dependence of spin canting degree on particle size indicates that the spin canting is not simply a surface phenomenon but also occurs in the interiors of the particles. [ABSTRACT FROM AUTHOR]

The magnetic properties of cobalt ferrite nanoparticles dispersed in a silica matrix in samples with different concentrations and same particles size are studied by using magnetization and Mossbauer spectroscopy measurements. The results have shown that the particles are very weakly interacting.

A structural investigation by x-ray diffraction is presented on ionic conducting glasses of composition (AgI)x (AgPO3)1-x, with x=0.0, x=0.45, and x=0.55. The radial distribution functions of the AgI-doped glasses, calculated from the experimental diffracted intensities, are dominated by a peak centered at about 2.80–2.85 Å, which can be ascribed to Ag–I pairs. According to this, model interpretations showed that the diffraction effects are essentially due to the shortest and heaviest pair interactions (Ag–I and Ag–O), while there is no evidence of important structural details at medium range. The compatibility of the results obtained with current models of AgI–AgPO3 glasses is examined. [ABSTRACT FROM AUTHOR]

X-ray diffraction measurements have been performed on glasses of the AgX–Ag2O–B2O3 (X=Br,Cl) systems. The only meaningful structural detail of the radial distribution functions is due to Ag–X interactions. The mean numbers of Ag–X contacts has been obtained through analysis of the high-angle partial structure functions si(s), calculated by subtracting experimental structure function of the Ag2O–B2O3 glasses from that of the corresponding AgX–doped glasses. Calculations have been also performed for AgI–Ag2O–B2O3 glasses, and comparison between the results from systems containing different halides is made. The average number of Ag–X contacts is very similar in samples at equimolar composition, thus suggesting a close structural feature in AgX–doped glasses. [ABSTRACT FROM AUTHOR]

X-ray diffraction measurements have been performed on glasses of the Ag2O–B2O3 and AgI–Ag2O–B2O3 systems. When silver iodide is present, the radial distribution function is dominated by a large peak at 2.85 Å, due to Ag–I interactions, with a shoulder at ∼2.40 Å, due to Ag–O pairs. The average number of Ag–I contacts has been calculated through analysis of the high angle structure functions si(s)’s, either by using the total si(s)’s or by using the partial si(s)’s, the latter obtained by subtracting the experimental structure function of the Ag2O–B2O3 glasses from that of the corresponding AgI-doped glasses. The compatibility of the results obtained with recently proposed models of AgI–Ag2O–B2O3 glasses is examined. [ABSTRACT FROM AUTHOR]

The radial distribution functions of cobalt glasses with 6%, 8% and 14% CoO are compared with those of suitable cobalt-free borosilicate matrices leading to ‘‘difference distribution curves’’ representative of the cobalt structural arrangement. Analysis of the curves indicates that cobalt ions are surrounded by approximately four oxygen neighbors at the distance expected for fourfold coordination. [ABSTRACT FROM AUTHOR]

Two concentrated solutions of NiBr2 have been examined by x-ray diffraction. The Fourier transformed scattering data indicate inner complex formation between Ni2+ and Br- ions. Average numbers of bonded bromide ions per nickel atom have been determined for each solution and the reliability of the complexation numbers as well as of the other structural parameters has been critically examined. [ABSTRACT FROM AUTHOR]