Methods of Obtaining Graphene Structures from Mineral Graphite

Graphene is an two-dimensional (2D) material with a thickness equal to one atom. Its structure is made up of carbon atoms bonded together in a hexagonal pattern, similar to a honeycomb [1]. Graphene can be obtained by various methods differing in price, ease of production and quality of the resulting product. The most common fabrication techniques include chemical vapor deposition (CVD), mechanical exfoliation, graphene oxide reduction, liquid phase exfoliation, and epitaxial growth on silicon carbide [2]. This work is focused on the methods where for graphene flakes were produced from mineral graphite. They were mainly based on the electrochemical and ultrasound assisted chemical techniques. One of the method was based on the mineral graphite electrodes, which were exfoliated in a electrolyte under the specific conditions. The solution prepared in this way was subjected to ultrasounds and freeze drying. Another approach was the chemical exfoliation of expanded graphite using sulfuric acid and hydrogen peroxide in specific proportions and method of introduction, in the process assisted by ultrasounds. The quality of the obtained materials was examined using X-ray diffraction, Raman and IR spectroscopy and SEM/TEM microscopy. In order to optimize the flakes production method, a series of experiments was performed in which the pH of the solution, the applied voltage and current, the duration of electrolysis, the temperature in the electrolytic system, as well as the time and type of ultrasound interaction were changed. The systematic research allowed to develop scalable and effective methods of obtaining graphene flakes of various quality, which, depending on their physical properties, can be used in various applications. The best quality graphene flakes have been used as a filler for polymers, paints and varnishes. In order to obtain an appropriate dispersion of the flakes in the composites, the functionalisation of the graphene surface was performed. The composites obtained in this way were subjected to mechanical and biological studies.<br/><b>Acknowledgements</b><br/>The project was supported by the National Center for Research and Development, Poland under grant no. LIDER/25/0132/L-10/18/NCBR/2019<br/><b>References</b><br/>E.P. Randviir, D.A.C. Brownson, C.E. Banks, <i>Materials Today</i>, <b>2014</b>, 17, 426–432,<br/>X.-Y. Wang, A. Narita, K. Müllen, <i>Nature Reviews Chemistry</i>, <b>2018</b>, 2, 0100.