Synthèse et caractérisation d’un nouveau matériau hybride à base de polyvinyle alcool-gel de silice dopé par le dioxyde de titane et préparé par la méthode sol-gel

Abstract

This thesis focuses on the synthesis and characterization of a hybrid material based on poly (vinyl alcohol)/silica gel/NanoTiO2 (1%). This new material was prepared by the sol-gel method using poly (vinyl alcohol) powder with tetraethyl orthosilicate (TEOS) as a precursor silica source. On the other hand, we use an ab-initio approach for the structural analysis, electronic band structure and thermoelectric properties of titanium dioxide (TiO2) in rutile phase. The hybrid films were characterized by different techniques including Fourier transform infrared (FT-IR), water absorption, water contact angle, ultraviolet-visible spectrometry (UV-VIS) and thermogravimetric analysis (TGA). The thermoelectric properties of the resulting hybrid films were characterized by the measurements of Seebeck coefficient, electrical and thermal conductivities. Through FT-IR analysis, the chemical bonds clearly showed that the PVA backbone is linked to the (SiO2-TiO2) network. UV-VIS tests indicated that the UV shielding properties of the hybrid films were significantly improved by the addition of TiO2. According to TGA tests, the hybrid films are more heat resistant than pure PVA films. The results of water contact angle revealed that TiO2 nanoparticles used as dopant have a significant influence on the hydrophilicity of PVA/SiO2 in the form of thin layers. The water resistance of the film was also improved. The best results are obtained in the cases of mechanical, thermal and electrical insulation when both nanofillers are integrated into the polymer matrix. The results show that the thermoelectric performances of PVA/SiO2 hybrid films are improved by the addition of rutile- TiO2 nanoparticles in the rutile phase.