Ultra-low energy processing of graphite: a fast-track journey towards carbon neutrality

Graphite is a fascinating material with unique properties, thus making it irreplaceable for a wide range of applications. However, its current processing route is highly energy demanding as it requires dwelling for several hours at high temperatures (2500-3000 degrees C). We report on the near full consolidation (relative density greater than 95%) at room temperature of graphite flakes under a mild uniaxial or isostatic pressure (100-500 MPa). The application of an external pressure promoted the formation of van der Walls bonds between the flakes, and the consolidation (pore removal) was mostly achieved by interplanar slipping. Despite the room temperature processing, with embodied energy below 1 MJ/kg, the resulting compact had in plane electrical and thermal conductivities as high as 0.77x 10(6) S/m and 620 W/m.K (exceeding commercial isotropic graphite approximate to 0.09x 10(6) S/m and 120 W/m.K). The bulks were thermally stable up to 1800 degrees C. Because of the reversible nature on the van der Walls bonding, the cold pressed pellets were fully recyclable (i.e., easily milled and re-shaped) with a mild degradation of the electrical conductivity from 0.77 to 0.19x 10(6) S/m after ten cycles.

Automated summary

Graphite, a material with unique properties, can be consolidated at room temperature using mild pressure. The resulting compact exhibits high electrical and thermal conductivities. Its recyclability is enabled by the reversible nature of van der Walls bonding.