Preparation of M41S family mesoporous silica thin films on porous oxides

The preparation of thin films of silicate MCM-41 and silicate MCM-48 on porous oxides have been studied using spin-coating, hydrothermal deposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption-desorption and thermogravimetry (TG). The work has included the template removal conducted on both supported thin films and powder samples via supercritical fluid extraction (SFE) at 85 °C and calcination at 540 °C. XRD and SEM observations show that films of both mesoporous molecular sieves are synthesized on the substrates with cetyltrimethylammonium bromide (CTMABr)-tetraethyl orthosilicate (TEOS) gels and beneficially formed on the substrates with pore sizes of 0.15 μm upwards. XRD and N2 adsorption-desorption studies reveal that removing the template via calcination leads to mesoporous structural distortion of supported MCM-41 and large pore contraction of supported MCM-48 thin films, whereas removing the template via SFE results in stable supported thin films with uniform mesopores. TG analysis indicates that the template SFE efficiency attains to 78% upwards. The behavior of supported thin films and powder samples in synthesis and in template removal are compared. The effects of the substrate on the formation and structural stability of thin films are observed.