Dehydroxylation of dioctahedral smectites in water vapor atmosphere

The dehydroxylation behavior of Na+-exchanged montmorillonites in water vapor atmosphere was compared to dehydroxylation in dry synthetic air. Water vapor at atmospheric pressure delays dehydroxylation of montmorillonites by 50 °C. The temperature boundary for dehydroxylation of trans-vacant and cis-vacant layers shifts by 50 to 75 °C to higher temperatures. Interlayer Na+ acts as flux and partial melting results in hollow spheres and bubbles that delayed dehydroxylation and entrapped water after dehydroxylation, which is suddenly discharged at higher temperatures. The formation of high temperature phases after heating to 1000 °C is controlled by the montmorillonite composition.