Structural study by transmission and scanning electron microscopy of the time-dependent structural change in M41S mesoporous silica (MCM-41 to MCM-48,and MCM-50)

摘要

High resolution transmission electron microscopy and field emission scanning electron microscopy are used to provide direct evidence for the solid-state transformations from cubic CMC-48 to lamellar mesophases.The structural chnge from MCM-41 to MCM-48 and MCM-50 with temperature is described in this report.Initially,a meta-stable MCM-41 is formed at room temperature,which turns into MCM-48 after a few hours at 140degC.Thermal treatment over longer periods of time leads to the formation of a lamellar phase.Thermogravimetric studies are presented for a better understanding of the surfactant-silica system and its modifications with temperature.