Laser-Induced Thermal Expansion of H₂SO₄-Intercalated Graphite Lattice

Abstract

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 H 2 SO 4 -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.

Graphene Platelets and Their Polymer Composites: Fabrication, Structure, Properties, and Applications

“…c) Series of thermal images recorded at different times during the laser‐induced expansion of a single grain, with the right column relating to temperature. Reproduced with permission . Copyright 2015, American Chemical Society.…”

“…GICs were fabricated through immersing graphite powders into a mixture of ammonium persulfate and sulfuric acid [(NH 4 ) 2 S 2 O 8 –H 2 SO 4 )] . Figure a 1 ,a 2 shows disk‐like H 2 SO 4 –GICs fabricated by Faima company (Italy) having thickness of 25 µm and lateral dimension of 500 µm . According to the Daumas–Herold model, the intercalants cannot occupy the entire graphite surface but form islands .…”

“…After thermal expansion, the GICs were converted into a 3 ) worm like structure with a 4 ) loosely connected graphene platelets. Reproduced with permission . Copyright 2015, American Chemical Society.…”

“…The treatment is often conducted in a crucible placed in a furnace at 700–1050 °C for 15–60 s,[5a,53] where an inert atmosphere may be unnecessary. According to the Kissinger and Ozawa equation, a heat energy of over 97.27 kJ mol −1 would decompose the intercalants of H 2 SO 4 –GIC to create gases including CO 2 , H 2 O, and SO 2 . The gasification should generate a pressure well above 2.5 MPa – the minimum pressure to overcome the interlayer van der Waals for a dramatic volume expansion of at least 80 times.…”

Synthesis and Characterization of Highly Intercalated Graphite Bisulfate

“…In addition, GICs are very important in graphite manufacturing [13] and potentially useful in other industrial fields like that of superconductors [14, 15], heterogeneous catalysts [16], anode materials [17], and pyrophoric reactants stabilization [17]. Currently, GICs are used in the preparation of expandable graphite, graphite nanoplatelets (GNP), and single-layer graphene [18–21]. Graphite nitrate and graphite bisulfate have the ability to significantly expand by thermal heating.…”