Fabrication, characterisation and stability of TiO2 nanofluids

摘要

TiO2 nanoparticles modified by oleic acid were prepared and dispersed into mineral oil to synthesise TiO2 nanofluids. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) analyses indicated that the TiO2 nanoparticles are single crystals with an average diameter of 6 nm. Measurements on the stability of nanoparticle dispersion in the base oil were performed by testing UV-Vis absorption spectra of nanofluids aged at a working temperature of 80 degrees C for 100 days. In addition, an AC breakdown test was carried out to further evaluate the stability of nanofluids. The obtained results show that the intensity of the UV absorption peak of nanofluid aged for 100 days has no obvious change in comparison with that of the fresh one. In particular, the ratio of the AC breakdown voltage of the aged nanofluid to the fresh one is still up to 98.6%. TiO2 nanofluids exhibit good colloidal stability at the working temperature. Fourier transform infrared spectra (FTIR) and thermogravimetric method (TG) analyses demonstrate that oleic acid anchors on the nanoparticle surface mainly by a chemisorption. This effective surface functionalisation of nanoparticles greatly enhances the stability of TiO2 nanofluids.