Investigation of silica-PVA xerogel microstructure evolution during thermal treatment by sans experiment

Abstract

The purpose of the study was to investigate the appearance of certain microstructures developing in the SiO2/PVA nanocomposite xerogels at different temperatures by small-angle neutron scattering (SANS). The samples were prepared by the alcoxide route of the sol-gel method. The SANS measurements were performed over a q (scattering vector) range from 0.05 to 3.7 nm-1, providing structural information at length scales (2?/q) between approximately 1 and 100 nm. The measured small-angle scattering intensities of silica and silica/PVA samples aged at 60?C and heat-treated at different temperatures, are presented in log-log plots. It is shown that both the molecular mass of organic and the temperature of thermal treatment have strong influence on transition tendency from mass fractal toward surface fractal structures.Cilj ovog rada je ispitivanje razvoja mikrostrukture SiO2/PVA nanokompozitnog kserogela na razlicitim temperaturama, primenom metode rasejavanja neutrona pod malim uglom (SANS). Uzorci su pripremani sol-gel metodom polazeci od alkoksida. SANS merenja su izvrsena preko vektora rasejavanja, q, u intervalu od 0.05 do 3.7 nm-1, cime je omoguceno dobijanje strukturnih informacija na skali (2?/q) priblizno izmedju 1 i 100 nm. Izmereni intenziteti rasejavanja pod malim uglom uzoraka silike i kompozita silika/PVA, posle starenja na 60?C i termicke obrade na razlicitim temperaturama, su predstavljeni u log-log dijagramima. Pokazano je da i molekulska masa i temperatura termicke obrade imaju veliki uticaj na tendenciju prelaska od masenih fraktalnih oblika prema povrsinski fraktalnim oblicima.