Influence of nanoparticle concentration on the frequency domain spectroscopy properties of transformer oil-based nanofluids

In order to explore the relationship between microstructure and macroscopic performance of transformer oil-based nanofluids, the transformer oil modified by silicon dioxide nanoparticles were prepared whose stability and moisture content were measured. Then the dielectric spectroscopy of the pure oil and transformer oil-based nanofluids were measured and the influence of nanoparticle concentration on the frequency domain spectroscopy of transformer oil-based nanofluids were investigated. The results indicate that compared with pure oil, two obvious polarization peaks can be observed in the imaginary part of the complex permittivity of transformer oil-based nanofluids in the whole measured frequency domain and the value of low frequency polarization peak is higher than the high frequency one. No obvious polarization peak is presented in the whole measured frequency range for pure oil. As the nanoparticle concentration increase, the value of two polarization peaks both increase, and the low frequency polarization peak has the tendency of moving to the high frequency. The electrical double layer theory was used to explain this phenomenon.