Green approach in the sol–gel synthesis of defect free unsupported mesoporous alumina films

Abstract

Sol–gel synthesis of defect free alumina films by the hydrolysis of metal alkoxide precursors require proper drying and calcination procedures. In the present paper an attempt has been made to gain control over the difficult process of sol–gel synthesis of plain, porous, defect free alumina films through proper design and selection of parameters like contact angle (120°), viscosity (1–2 Pa s), drying and calcination temperature. SANS, AFM, TEM probes were used to investigate porous alumina film (α alumina) made up of parallel channels with cylindrical shape. Nitrogen adsorption studies (BET method) were carried out to determine porosity and surface area of the film. The SEM and X-ray diffraction studies were done to characterize the alumina film. The kind of technique used during synthesis of alumina film is not only cost affective but has an added advantage of controlling the shape and geometry of alumina film. The novel technique of disc furnace introduced here has overcome the difficulties of cracking and deformation in the sol–gel synthesis of alumina film during calcination. It has been shown that various sizes of porous, plain unsupported alumina films with a diameter of 30–50 mm and thickness of 0.5–5 mm were prepared by using sol–gel method.