ИСТИНА

Exfoliated graphite (EG) is a lightweight carbon material with original chemical and physical properties: chemical inactivity, variable heat- and electro- conductivity, developed pore structure etc. The modification of exfoliated graphite with metal compounds leads to formation of so called EG/metal or EG/metal oxides composites which can be used as gas storage materials, catalysts support etc. One of the most interesting applications for such catalysts is catalytic growth of carbon nanofibres, nanotubes and carbon nano-onions by chemical vapor deposition (CVD). Obtained EG/carbon nanostructure composites have a great potential of application as sorbents, heat-resistant materials, catalysts for fuel cells etc. Herein we report the way of preparation and properties of EG/carbon nanostructures composites. EG/FexOy composites were prepared by three various techniques. The first one is graphite oxide modification with iron nitrate (III) and its thermal exfoliation at 250 0C. The second one is graphite nitrate hydrolysis with solutions of iron (III) nitrate and further exfoliation at 900 0C. The third one is exfoliated graphite impregnation with iron (III) nitrate in organic solvents. The prepared EG/iron oxides composites were used for catalytic growth of carbon nanostructures. Experiments were carried out by CVD at temperature of 600 – 900 0C using C6H6/C6H12 mixture. According to XRD, SEM, EDX, TEM analysis and Mossbauer spectroscopy EG/FexOy composites contain α-Fe2O3, γ-Fe2O3 and Fe3O4 particles distributed on the surface of exfoliated graphite. The composition of iron oxides in composites and their particle size depend on the technique and preparation conditions. Depending on particle size and shape of iron oxides in EG/FexOy composites the formation of carbon nanotubes, nano-onions or nanofibres is observed as a result of CVD process. The smaller the particle size the smaller dimension of nanostructures is observed. The presence of carbon nanostructures in composites causes the increase of the material microporosity that was investigated by the low temperature nitrogen adsorption.