Dielectric study of self assembled nanofluids by means of AC breakdown tests and dielectric relaxation spectroscopy

In this paper a detailed study of two types of nanofluids is performed by means of AC breakdown voltage tests (IEC 60156) and Dielectric Relaxation Spectroscopy. The first under tested nanofluid (pNF) is composed from natural ester oil matrix and purchased nanoparticles (Aldrich) ensuant to surface modification coating. Accordingly, the second nanofluid (colNF) aparted from colloidal hydrophobic self-assembled nanoparticles with in-situ surface coating technique, inserted adequately into natural ester oil matrix. The aforementioned nanofluids (pNFcolNF) are studied under AC breakdown voltage wherein an interesting increase of the dielectric strength is demonstrated. Accordingly the dielectric response of the aforesaid nanofluids has been investigated by employing dielectric measurements, wherein the nanofluid's dielectric permittivity is studied isothermally, as a function of frequency in the range of 10^-1 to 10⁶ Hz at temperatures from 20-100 °C under dry nitrogen atmosphere. Finally a thermal response study is performed, wherein the response of the nanofluids is compared with the natural ester oil matrix.