Thermal Conductivity Enhancement Through Kinetically Arrested Dispersion—Breaking Dispersion Barriers of Highly Conductive Carbon Allotropes in Aqueous Solutions

Carbon-based nanomaterials such as graphene are usually produced industrially as powder-like materials. Harnessing the incredible potential of these nanocarbons (e.g., high electrical and thermal conductivities) in many applications (e.g., conductive inks and heat transfer fluids) requires their dispersion. However, when the highly hydrophobic graphene sheets are dispersed in water, they tend to aggregate and precipitate due to strong van-der-Waals attraction. Surface treatment of graphene (via surfactant adsorption or chemical modification) results in a low concentration of dispersed graphene (<0.2wt%) of relatively small lateral size (<0.5μm), or in high defect density, both are detrimental for thermal management applications. In this work, we disperse graphene in water by adding fibrous clay mineral - sepiolite - a negatively charged particle, which kinetically arrests the system. The “trapped” graphene cannot re-aggregate and precipitate. The trapping mechanism makes it possible to disperse high graphene concentration (1wt%) with high lateral size (>5μm). This approach applies to all three dimensionalities of carbon, that is, 1D-carbon nanotubes, 2D-graphene and 3D-graphite. The thermal conductivity (TC) of liquids, an essential parameter in heat dissipation applications, could be enhanced by 31% via loading graphene as a filler material both in water, and in commercial cooling liquids such as water-ethylene glycol mixtures. The proposed dispersion approach is filler independent, and could be employed in enhancing composite properties both in liquid and solid states for thermal managment applications of electronics.