FEATURES OF ULTRASONIC SPLITTING OF THERMALLY EXPANDED GRAPHITE

Thermally expanded graphite is obtained from crucible graphite by treatment with oleum in the presence of an oxidizing agent.  The obtained samples of thermally expanded graphite were subjected to ultrasonic dispersion (splitting up) in four liquid media (water, toluene, benzene, acetone). It was shown that in the process of ultrasonic dispersion (splitting), the initial thermally expanded graphite is split into plates with a thickness of several tens to hundreds of nanometers. However, the plates are not single, but are in chaotic clusters with each other. The free bonds of carbon atoms, which are located at the edges of the plates, can play an important role in chemical processes and in the adsorption of substances on the surface of particles of split graphite. It was found that a high degree of perfection of the crystal structure, which is typical of the original graphite, is retained during ultrasonic treatment as compared with mechanical splitting. The change in the specific surface of graphite samples is presented. The main increase in the specific surface of the particles during ultrasonic splitting is created by increasing the area of the surfaces formed during interplanar splitting of graphite plates. Based on the comparison of this parameter, the effect of the used liquids on the splitting process is considered. The high values of the specific surface of the samples split in benzene and toluene are explained by the low values of the surface tension. The good wettability of the graphite surface with benzene, toluene and acetone compared with water allows these liquids to penetrate deep into the pores of graphite. Due to this, maximum splitting is achieved with ultrasonic processing of the mixture. Conclusions on the choice of the optimal liquid medium for dispersing graphite are made.