Pyrolysis Effect on Physical Properties of Carbon–Silica Nano-composites Elaborated by Sol–Gel Method

Abstract

In this work, nanocomposites have been developed from the incorporation of silica nanoparticles with a 70% of the started mass material into a carbon matrix based on resorcinol and formaldehyde (RF) by the sol–gel system, then the samples are put in an oven for slow drying by step of 10 °C/day until 150 °C then pyrolysed at 675 °C (RF–SiO₂-0.70–675), 700 °C (RF–SiO₂-0.70–700) and 725 °C (RF–SiO₂-0.70–725) under inert atmosphere for 2 h. We are interested in the percolation zone from 675 °C to 725 °C, where the behaviour of the matter changes from an insulating state to a semiconductor state as a function of the pyrolysis temperature, we carry out the structural and morphological and electrical characterization of these nanocomposites. The XRD analysis shows that all samples have amorphous phases the existence of two phases: insulating silica (SiO₂) and graphite (C).The TEM images of samples show that the materials were mainly composed by spherical nanoparticles of 26 to 32 nm in diameter. Nevertheless, the same transition was also observed for the sample RF–SiO₂-0.70–700 when the measurement temperature varied between 140 and 160 K. The carbon–silica nanocomposites can be synthesized with engineered conductivity and morphology and thus can be used in several technological domains.