Synthesis and characterization of lamellar-structured silica thin films with high thermal stability greater than 450 °C

Abstract

We synthesized lamellar-structured silica thin films with various repeating distances in the range 5.9–8.8 nm. The synthesis was achieved through the self-assembly of a silica precursor (tetraethoxyorthosilicate) and a non-ionic triblock copolymer F-127 ((EO)₁₀₆(PO)₇₀(EO)₁₀₆, EO = ethylene oxide, PO = propylene oxide), followed by calcination. The lamellar structure was unambiguously confirmed by small angle X-ray diffraction, grazing incidence small angle X-ray scattering, transmission electron microscopy, and atomic force microscopy. The lamellar structure can be understood as being composed of alternating high density and low density silica layers. The successful synthesis requires the right compositions of the coating solutions and a high spin-speed (≥6000 rpm) during the spin-coating of the solutions. Mechanisms for the formation of the lamellar structure and its maintenance after the surfactant removal were proposed. Such a structure exhibits remarkable properties, including very high thermal stability up to 800 °C and unusually high mechanical properties for nanostructured silica films.