2.2. Synthetic Procedure for the Preparation of the TiO2@SiC Core–Shell Nanoparticles

The synthesis of the TiO₂@SiC core–shell nanoparticles is based on the method described by Cernaux et al. [13] and was undertaken by initially dispersing 10 g of SiC (50 nm) in 78 mL of isopropanol at room temperature. In order to diminish the agglomeration of the SiC particles, sonication of the mixture for 15 min was performed. Although some agglomeration of the SiC nanoparticles was still observed after the sonication, no additional dispersant was used to avoid the possible increase in impurities when using these particles in composite materials. Then, 7.8 mL of the titanium precursor Ti(OⁱPr)₄ were added dropwise to the previous suspension, and the mixture was maintained with stirring for another 10 min. Once the mixture was properly homogeneous, 7.8 mL of acetic acid and 4.7 mL of distilled water were added to produce the hydrolysis and condensation of the Ti(OⁱPr)₄ precursor. The mixture was stirred in air at room temperature, and the solvent was removed by heating under reduced pressure. The resulting dry powder was heat-treated in air at 450 °C for 2 h in a muffle furnace to allow the combustion of the remaining organic material in the titanium precursor. In addition, this heating process allowed completing the dehydration of the primary hydrated oxide and the consequent crystallization of the TiO₂ as the desired shell onto the SiC nanoparticles.

In order to get a material with a thicker shell without increasing the amount of oxygen in the final core–shell system, we also assayed the same procedure as for TiO₂@SiC (50 nm SiC), maintaining the weight proportion between the titanium precursor and the SiC, but this time using bigger SiC nanoparticles of an average size of 500 nm.