, G. Rosano-Ortega

The proportion of urea in the modified combustion method to prepare lithium metasilicate (Li2SiO3) powders was investigated. Reactions were performed using LiOH:H2SiO3:CH4N2O in molar ratios of 1:1:1, 1:1:2, 1:1:3, 1:1:4 and 1:1:5 which were heated at 450 C during 5 min. It was found, by X-ray diffraction, that LiOH:H2SiO3:CH4N2O in the ratio of 1:1:3 was the more adequate molar ratio to produce mainly Li2SiO3. It was observed that excess of urea produced mainly silicium dioxide (SiO2) in coesite phase instead Li2SiO3. Thermogravimetric analyses showed that decomposition products of urea, such as biuret, cyanic acid and cyanuric acid, were found in samples prepared with high proportions of urea (1:1:4 and 1:1:5). Carbonates identified by IR spectroscopy were found in samples prepared with LiOH:H2SiO3:CH4N2O in 1:1:1, 1:1:2, 1:1:3, 1:1:14 and 1:1:5 molar ratios