Ordered graphitic microfoams via shrinkage and catalytic conversion of polymer scaffolds

Abstract

Carbon foams are a highly attractive class of low-density materials whose structural, electrical, thermal, and chemical properties are strongly linked to the level of graphitization and 3D structure. Pyrolytic graphitization requires very high temperatures (>2000 °C), and most current graphitic foams are stochastically arranged with restricted control over pore size and architecture. We report on the shrinkage and catalytic conversion of commercial polymer foams and 3D printed templates as a facile, cost-effective method to scalably reach and control sub-200 μm unit cell sizes and a high level of graphitization at temperatures below 1100 °C. We demonstrate the conversion of 3D printed cubic polymer lattices to an identically shaped carbonaceous network with shrinkage controlled via an atomic layer deposited oxide coating up to a maximum 125 fold decrease in volume and over 95% mass loss through slow carbonization. This is accompanied by a reduction in the unit cell size from 1000 µm to 170 µm and strut widths from 550 µm to 65 µm. The structures are subsequently coated with a sacrificial metal catalyst by electroless deposition to achieve efficient graphitization while maintaining structural order. We discuss the underlying mechanisms and opportunities to tailor the processes and structure to manifold application needs.