Electrically Insulating Thermal Nano-Oils Using 2D Fillers

Abstract

Different nanoscale fillers have been used to create composite fluids for applications such as thermal management. The ever increasing thermal loads in applications now require advanced operational fluids, for example, high thermal conductivity dielectric oils in transformers. These oils require excellent filler dispersion, high thermal conduction, but also electrical insulation. Such thermal oils that conform to this thermal/electrical requirement, and yet remain in highly suspended stable state, have not yet been synthesized. We report here the synthesis and characterization of stable high thermal conductivity Newtonian nanofluids using exfoliated layers of hexagonal boron nitride in oil without compromising its electrically insulating property. Two-dimensional nanosheets of hexagonal boron nitride are liquid exfoliated in isopropyl alcohol and redispersed in mineral oil, used as standard transformer oil, forming stable nanosuspensions with high shelf life. A high electrical resistivity, even higher than that of the base oil, is maintained for the nano-oil containing small weight fraction of the filler (0.01 wt %), whereas the thermal conductivity was enhanced. The low dissipation factor and high pour point for this nano-oil suggests several applications in thermal management.

Low-density three-dimensional foam using self-reinforced hybrid two-dimensional atomic layers

“…The whitish supernatant (top part) is decanted and was vacuum filtered, using a Sartorious PTFE-filter membrane with a pore size of 0.2 mm. After this process, 2D h-BN nanosheets (B500 nm by 500 nm, approximatelyfive layers in thickness) were obtained 33 . The h-BN nanosheets were washed twice with water, ethanol and chloroform to remove any residual DMF and the dried material was then scraped off from the filter paper.…”

“…The heterostructures formed by atomic layer stacking of hexagonal boron nitride (BN) with graphene have led to very interesting optical, electronic and mechanical properties [25][26][27][28][29] . The chemical inertness, high mechanical strength and the ability to withstand extremely high temperature make BN an ideal material for building monolithic and composite 3D scaffolds [30][31][32][33] . BN exists in different crystalline forms of which hexagonal boron nitride (h-BN) is the most structurally compatible form and is an isomorph of graphene 34,35 .…”

Avaliação De Diferentes Rotas De Esfoliação Líquida Para Obtenção De Nanolamelas De Nitreto De Boro Hexagonal

“…4,6 Dessa forma, o processo de separação por meio da esfoliação facilita a exposição desses planos e a exploração do material.…”

“…2,3,7,12 Embora a estrutura geral e os espaçamentos atômicos de ambos sejam muito semelhantes, materiais de nitreto de boro (BN) possuem interações mais fortes entre suas camadas devido à diferença de eletronegatividade de seus átomos, dificultando a separação das lamelas. [6][7][8][9][10]13,14 Inúmeros métodos sintéticos vêm sendo desenvolvidos para a obtenção de uma ou poucas camadas de nanolamelas de BN, tanto em qualidade quanto em quantidade, podendo ser divididos em processos químicos (bottom-up) ou físicos (top-down). 1,2,4,[8][9][10][11] Os métodos químicos são baseados em reações e utilizam precursores moleculares ou atômicos para a obtenção das nanopartículas desejadas.…”

“…1,[9][10][11]16,17 Os métodos físicos manipulam o material em escala macro e por meio de técnicas como clivagem micromecânica, intercalação iônica, esfoliação líquida, fragmentam as partículas até que estas fiquem em escala nanométrica. 1,6,8,11,[13][14][15] Oferecem vantagens em relação às rotas químicas devido à redução de custos, compatibilidade térmica com o …”