Study of thermal stability of hierarchical structured carbon composite flakes

Abstract

The hierarchical structured carbon flakes (HSCF) consisting of sp-, sp2- and sp3-hybridised carbon with highly evolved crystal structure on one side and smooth on the other side synthesised. XRD and photoelectron spectroscopy studies reveal that annealing in the air up to the temperature of 450 °С brings about a decrease in the content of sp3-hybridised carbon. At the same time, the surface area increases from 547 m2/g to 761 m2/g. Visually this is manifested in the “flattening” of the carbon flakes on SEM images. After annealing at 500 °С, the film loses practically all its developed hierarchical structure, which is related primarily to a further decrease in the content of sp3-hybridised carbon compared to lower temperatures. DSC and thermogravimetry measurements indicate that the loss of HSCF mass under purified argon flow is due to the removal of the oxygen-containing functional groups from the surface of the carbon nanocomposite, their amount expectedly increases after annealing in air at 450 °С. The temperature at which HSCF completely burns out under flowing air is much higher than such a temperature for other carbon nanomaterials with a similar specific surface, which may be related to a high content of sp-hybridised carbon generated by annealing.