Morphic transitions of nanocarbons via laser pyrolysis of polyimide films

- Laser pyrolysis is applied on polyimide films to produce nanocarbon foams.
- Such pyrolytic foams consist of graphene merging into honeycomb networks.
- Surface patterning is controlled by selecting appropriate sets of laser parameters.
- Morphic groups are distinguished by patterning, which controls surface properties.
- By repeated laser pyrolysis, graphene foams convert into carbon nanotube foams.

Attempting a thorough investigation of polyimide pyrolysis via CO2 lasers, we revisit the Laser-Induced Graphene (LIG) method, and determine the optimal operating window for producing pyrolytic nanocarbons. We design an experimental investigation that targets the full parameter space of available laser operating parameters: laser power, scan rate, and step interval. This allows us to produce different morphic groups of nanocarbons with properties depending on their surface morphology by directly controlling surface patterning. We further establish that the base material comprises a network of vertically aligned graphene channels, hereby referred to as graphene foam, thus readdressing the classification of Multi-Layer Graphene (MLG) given in previous research. We show how the laser pyrolysis method can be adapted for the production of carbon nanotubes (CNTs) via repeated pyrolysis of the starting graphene foam over high laser fluence levels. We characterize the pyrolytic nanocarbons via optical and scanning electron microscopy, Raman and UV-vis spectroscopy, surface tension measurements, and thermogravimetric analysis.