Author: Arvind-Pal Singh Mandair
About: The influence of added oxides on the progress of the thermolysis of laponite at 1300°C was investigated. Calcium oxide promotes the depolymerization of the clay silicate lattice and, even at low CaO additions, mixed calcium/magnesium phases were identified; at higher additions akermanite was a dominant crystalline phase. Sodium oxide was even more effective as a depolymerizing agent; when the total molar proportion of Na2O exceeded the total concentration of the other component oxides of laponite (Li2O, MgO), a glass is formed and no crystalline phases were detected. By contrast, evidence was obtained that additions of Al2O3 could increase the degree of connectivity as evidenced by the formation of new alumino-silicate phases such as sillimanite; spinel, MgAl2O4, was a dominant crystalline phase at higher Al2O3 additions. The products of the reactions studied were examined using 29Si, 23Na and 27Al MASNMR spectroscopy and this technique was shown to be particularly powerful for the study of systems in which glassy and crystalline phases co-exist.
