Optical and thermal properties of sol–gel Al(OH)3–Fe(OH)3–PVA composite films

Abstract

In this paper, the evaluation of the interaction forces of Poly(vinyl alcohol) (PVA)-coated nanoparticles of aluminum and iron hydroxides was carried out using the classical and extended Derjaguin–Landau–Verwey–Overbeek (DLVO) theory on the basis of experimentally determined sizes and electrokinetic potentials of sol particles. Calculations of the interaction energy between nanoparticles showed that the steric stability factor has a decisive contribution to the aggregative stability of these sols. Organic-inorganic Al(OH)3–Fe(OH)3–PVA composite films with different ratio of components were obtained by mixing polymer-containing sols of aluminum and iron (III) hydroxides. UV–vis absorbance and specular reflectance spectra of prepared films were recorded, and the optical constants such as absorption coefficient, absorption edge, optical band gap (both direct and indirect), refractive index, CIE coordinates, as well as film thickness were determined. The possibility of varying the color and optical parameters of the films by changing the ratio of aluminum and iron hydroxides is shown. The presence of hydroxide nanoparticles in polymer films leads to a change in the mechanism of thermal-oxidative destruction of PVA, which is manifested in the acceleration of weight loss with the simultaneous appearance of an endothermic effect at a temperature of about 280 °C, as well as in the displacement of thermal effects.