Towards understanding the thermoanalysis of water sorption on lithium orthosilicate (Li4SiO4)

A systematic thermogravimetric study of hygroscopic and reactivity behaviors, at low temperatures of lithium orthosilicate (Li4SiO4), are presented. Li4SiO4 sample was prepared by solid-state reaction and then treated at different temperature-humidity conditions. Li4SiO4 samples previously treated under different temperature-humidity conditions were characterized by Fourier transform infrared spectroscopy and thermogravimetric analyses. Different processes, adsorption and absorption, take place between the Li4SiO4 and water vapor. Absorbed water produces superficial hydroxylated species such as Si–OH and Li–OH. In addition, a kinetic analysis was performed, and the different water absorption activation enthalpies were calculated. It was found that activation enthalpy (ΔH‡) values decrease when the relative humidity is incremented, from 5528.6 J/mol to 2074.2 J/mol at relative humidity levels of 60% and 75% respectively. These results show the impact of different humidity and temperature conditions on the stability and/or chemical reactivity of Li4SiO4, if this ceramic is used in different application fields, such as carbon dioxide captor or as a breeder ceramic into the fusion reactors.