Porous boron nitride nanostructures infused transformer oil nanofluids with superior thermal and insulating properties.

This study investigates the impact of porosity on the multifunctional performance of transformer oil (TO) nanofluids infused with porous boron nitride (PBN) nanofillers. Two variants of PBN, namely PBN 950 and PBN 1050, are synthesized via heat treatment at 950 °C and 1050 °C, respectively. Both the variants are composed of 2D porous nanoflakes of quasi-crystalline hexagonal BN, arranged in different patterns. PBN 950 resembles a rod-like pattern with low specific surface area (SSA) and high aspect ratio (AR), whereas PBN 1050 appears as a flowerlike morphology with higher SSA and lower AR. TO nanofluids consisting both the PBN variants in the 0.0025–0.01 wt. % range demonstrate noteworthy improvements in dielectric and thermal performances. A linear correlation is observed between the porosity-induced SSA and the AC breakdown strength of the TO nanofluid. Around ~26–39% increment in the AC breakdown voltage as well as the volume resistivity is observed. Both PBN 950 and PBN 1050 exhibit enhanced thermal conductivity of TO by ~32.5% and ~28%, respectively at 50 °C. The flash point and the pour point of the oil remain unchanged, whereas a negligible increase in acidity is detected over several months. This indicates a long-term chemical stability of the nanofluids. These findings propose that PBN with optimized SSA aids as a superior nanofiller for next-generation TO nanofluids, offering improved thermal and dielectric performance at lesser filler loadings compared to other BN-based materials described in the literature.