Kinetic analysis of the thermal stability of lithium silicates (Li4SiO4 and Li2SiO3)

✍ Scribed by Daniel Cruz; Silvia Bulbulian; Enrique Lima; Heriberto Pfeiffer

• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 696 KB
• Volume: 179
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1016/j.jssc.2005.12.020

✦ Synopsis

The kinetics describing the thermal decomposition of Li 4 SiO 4 and Li 2 SiO 3 have been analysed. While Li 4 SiO 4 decomposed on Li 2 SiO 3 by lithium sublimation, Li 2 SiO 3 was highly stable at the temperatures studied. Li 4 SiO 4 began to decompose between 900 and 1000 1C. However, at 1100 1C or higher temperatures, Li 4 SiO 4 melted, and the kinetic data of its decomposition varied. The activation energy of both processes was estimated according to the Arrhenius kinetic theory. The energy values obtained were À408 and À250 kJ mol À1 for the solid and liquid phases, respectively. At the same time, the Li 4 SiO 4 decomposition process was described mathematically as a function of a diffusion-controlled reaction into a spherical system. The activation energy for this process was estimated to be À331 kJ mol À1 . On the other hand, Li 2 SiO 3 was not decomposed at high temperatures, but it presented a very high preferential orientation after the heat treatments.