Laser-Induced Thermal Expansion of H2SO4-Intercalated Graphite Lattice

Intercalated graphite materials allow studying reactions occurring in confined chemical conditions. In this work, we investigate the sulfuric acid intercalated graphite exfoliation process using a simple technique based on the continuous-wave (CW) infrared (IR) laser irradiation of graphite flakes. Using Kissinger and Ozawa methods, the activation energy of H2SO4-intercalated graphite was determined to be less than 100 kJ mol–1. The laser-assisted reaction process was found to be characterized by a threshold temperature of about 140 °C followed by a fast rate of heating. The large amount of volatilized hot gases caused a violent expansion of the graphite flake. Morphological changes undergone by irradiated graphite flakes have been analyzed using a combination of thermal and visible imaging techniques, which allowed for the quantitative determination of temporal evolution of the thermal field during the heating stage and expansion of the flake.