This paper reports on experimental investigations dealing with the influence of titanium dioxide nanoparticles on the breakdown voltage of transformer oil. TiO 2 particles with the nano size could be synthesized by the sol-microwave method. The materials characterized by XRD, SEM and TEM techniques. In this study, we have measured the dielectric breakdown voltage of transformer oil-based nanofluids in accordance with IEC 156 standard. The concentrations of TiO 2 nanoparticles in transformer oil are in the range from 0.001 g/l to 0.01 g/l. These concentrations for fresh oil (before and after the physical purification) and used oils for about 4 and 15 years, evaluated separately and the results were compared. Experiment results indicated that the addition of TiO 2 nanoparticles to transformer oil can enhance its dielectric strength and the surface compositions of the TiO 2 nanoparticles play an important role in its dielectric performance. When the volume concentration of nanoparticles is above 0.003 g/l, the dielectric breakdown voltage decreases. Based on test results and Due to the weather conditions in Gilan that has about 80 percent humid, titanium dioxide can be increase the breakdown voltage of transformer oils in free of moisture as well as humidity conditions.

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magnetic nanocompsites with 0.1-1 at% of Fe 3+ content were synthesised by sol-gel method. The surface morphology, structure and crystalline phase of the nanocomposite were characterised by using XRD, SEM, HRTEM, EDX, BET, Diffuse reflectance spectroscopy (DRS) and VSM techniques. Photocatalytic activity experiments confirmed that as-prepared nanocomposite had good photodegradating behaviour to Direct Blue 71 under visible-light irradiation. 99.6% decomposition of dye was achieved within 50 min in the presence of the prepared photocatalyst. The nanocomposite could be easily recovered from the reaction solution by using a permanent magnetic bar and its photocatalytic activity remained 90% after five cycles of repetitious reusing. Then 0.5% Fe 3+ /TiO 2 @Fe 3 O 4 nanocomposite can be used as highly efficient reusable catalysts.