Stability and thermal conductivity enhancement of aqueous nanofluid based on surfactant-modified TiO2

The surface modified-titania (TiO2) nanoparticles were prepared by hydrothermal treatment by two kinds of surfactants, CTAB and SDS. The produced nanoparticles were characterized by XRD, FESEM/EDS, TEM and FTIR analysis techniques. The surfactant modified-TiO2 nanoparticles were dispersed into distilled water to achieve good dispersion stability and enhanced thermal conductivity. The stability of distilled water based nanofluid was checked by sediment photograph capturing. The nanofluid including modified TiO2 nanofluid with a volume fraction of 1.25% stayed up to two weeks without apparent sedimentation contrary to the unmodified TiO2 nanofluid. The UV-Vis spectral results revealed that the decrease in the concentration rate was only about 12% and 20% in case of CTAB treated-TiO2 and for SDS treated-TiO2, respectively. The results obtained from the Laser diffraction particle size analysis showed the existence of thermodynamically stable clusters. The nanofluids made with CTAB-treated and SDS-treated nanoparticles with volume fraction of 1.25% indicated an improvement in thermal conductivity as 15% and 10%, respectively. The transient thermal conductivity measurement allowed monitoring the stability behavior of the nanofluid.