Methyl alcohol has been examined at room temperature by means of x-ray diffraction technique. The radial distribution curve straightforwardly shows O ⋅⋅⋅ O interactions at about 2.8 Å, which indicate that extensive hydrogen bonding is occurring in liquid methanol. The other prominent peaks of the radial curve fulfill the zig–zag chain model found in solid methanol. A direct analysis of the structure function leads to the conclusion that the average number of nearest oxygen neighbors per oxygen atom lies between 1.40 and 1.55. On the contrary, no unique conclusion, as far as the shape of the chain is concerned, can be obtained through the x-ray scattering data.

The structural evolution of nanocomposite samples prepared using the solÈgel method have been Fe 2 O 3 ÈSiO 2 studied by EXAFS (extended X-ray absorption Ðne structure) and XANES (X-ray absorption near edge structure) techniques in comparison with pure nanosized and microcrystalline maghemite samples. EXAFS data show that the di †erence between nanosized and microcrystalline maghemite is due to an increase of disorder of the superÐcial sites while no decrease of coordination numbers was detected. EXAFS and XANES data of the nanocomposite thermally treated at 900 ¡C indicate that the sample is constituted by maghemite nanoparticles embedded into amorphous silica while the sample thermally treated at 300 ¡C contains an amorphous precursor which is very likely to be ferrihydrite. No interactions between the metal oxide nanoparticles and the silica network are present since the EXAFS spectra of the nanocomposite samples can be interpreted as only having FeÈO and FeÈFe interactions.

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Two concentrated (5 and 7 mol l−1) aqueous solutions of NaNO3 were investigated by x-ray diffraction. The features of the total radial functions calculated from experimental intensity data show that the positional correlation is not very strong in the systems investigated. However, it is possible to account for experimental data only by using models in which hexahydrated Na+ ions have definite correlations with NO3− ions, even if not through formation of isolated ion pairs. The compatibility of our observations with spectroscopic results is also discussed.

Nanocrystalline gamma-Al2O3 and FeCo-Al2O3 nanocomposite aerogels with high surface areas and pore volumes were prepared by high-temperature supercritical drying of alcogels obtained by a fast sol-gel procedure. The formation of gamma-Al2O3 occurs via a sequence of stages: in the parent aerogel an alkyl derivative of boehmite is observed whose calcination gives rise to a disordered phase and finally to gamma-Al2O3 which is stable up to 1000 degreesC. In the presence of iron and cobalt, calcination of the aerogel gives rise to a spinel phase similar to gamma-Al2O3 where metal ions partially fill the vacancies. Nanocomposites constituted of FeCo alloy nanoparticles dispersed into gamma-Al2O3 matrix are obtained via reduction in hydrogen flow of the aerogels containing iron and cobalt. The amount and average size of the nanoparticles depends both on the temperature and time of the reduction treatment and affects the resulting magnetic properties. All the reduced aerogels show superparamagnetic behavior, but the collective magnetic properties are strongly dependent on the amount and mean size of the alloy nanoparticles