Optical absorption characteristics for ultra-fine bismuth particles having dimensions around 10 nm and dispersed in both silicate and vanadium phosphate glass matrices have been investigated in the wavelength range 300 to 700 nm. Bismuth particles in vanadium phosphate matrix show an absorption peak around 440 nm whereas in silicate glass matrix they give two peaks in the ranges 500 to 530 nm and 420 to 430 nm respectively. The peak positions in all the glass-bismuth metal systems are predicted in fair agreement with experiment by Maxwell-Garnett (mg), as extended by Polder and van Santen (mg-pvs) and Bruggeman (br) effective medium theories. It is observed, however, thatmg-pvs andbr models give the best fit to experimental data over the entire wavelength range studied.

Optical absorption characteristics in a glass-metal nanocomposite system involving bismuth metal have been analysed using effective medium theories with a model incorporating single strand chains andfcc clusters of metallic bismuth particles. The computed values show fair agreement with experimental data.

Gel has been prepared with nickel chloride and glucose in the starting solution followed by heat treatment at higher temperature, where glucose decomposes to carbon and water vapour, which in turn react to form hydrogenin situ to reduce nickel chloride to metallic nickel. The presence and distribution of nickel granules in the microcomposite, has been established by transmission electron microscopy, selected area diffraction and electron paramagnetic resonance analysis.

Glass-silver microcomposites have been prepared through sol-gel route by reducing the gel-containing AgNO₃ with alkaline formaldehyde solution. The product has been characterized by atomic absorption spectroscopy and X-ray diffraction technique. Optical spectroscopy of thin films has been studied.

Isothermalin situ reduction kinetic study of NiCl₂-containing gel was carried out. The detailed statistical as well as reduced time analysis show that contracting geometry and nucleation and growth type of mixed mechanisms are operative. The activation energy for reduction is in the range 158–193 kJ/mol. Thermal analysis on NiCl₂-containing gel was carried out in the temperature range 800°C to 900°C.

The present investigation deals with the synthesis of monolithic NiCl₂-silica gels obtained by hydrolysis and polycondensation of tetraethoxy silanes. This sol to gel formation can mainly be controlled by adjusting some variables e.g. acid content of the solution, ageing and leaching times. A minimum acid content was found necessary to prepare uncracked gel while ageing and leaching times were found to be not that sensitive for the formation of uncracked gels.