Page 12 - PR 2014 2016 10 Materials and Nanotechnology

288 Materials and Nanotechnology | Progress Report

Chemical Synthesis and graphene layers. CVD has been proposed for
Processing of Ceramic production of large area films and wet-chemi-

Powders cal treatment of graphite has been indicated for
preparation of small graphene-based platelets.
The latter is suitable for applications in energy
Graphene synthesis for energy and conversion and storage systems and ceramic
biomedical applications biocomposites, which is the focus of the re-

searches developed at Ceramic Raw Materials
Graphene is an allotropic form of carbon Laboratory of IPEN. Besides the experimental
packed in two-dimension layer (2D) with hon- facilities concerning the use of homogeneous
eycomb lattice structure that can be isolated colloidal suspensions, the low-cost production
from graphite (Figure 13). Its remarkable tech- makes this method an attractive choice.
nological importance is due to the outstand-
ing physical and chemical properties such as The graphene synthesis procedure employed
electrical and thermal conductivity, elastic by Ceramic Raw Materials group was adapted
modulus, fracture strength, flexibility, surface from the method developed by Hummers and
area, adsorption and desorption capacity of Offeman in 1958 and improved by Marcano et
gases and biocompatibility. Experimental and al in 2010 in order to enhance safety. Typically,
theoretical studies on the synthesis and prop- graphite flakes (G) is oxidized with a mixture of
erties of graphene have been carried out since concentrated sulphuric and phosphoric acids
the nineteenth century, but its popularity was followed by addition of potassium perman-
motivated from the paper of Nobel Laureates ganate and hydrogen peroxide under specific
Geim and Novoselov, published in 2004, in conditions of stirring and heating. The mix-
which the physical effects predicted in theo- ture is centrifuged and the remaining solid
retical studies were confirmed experimentally. material is sonicated with deionized water.
Using a simple method of mechanical exfoli- This material, denominated graphene oxide
ation of graphite sheets by adhesive tapes, it (GO), is further reduced with acid ascorbic
was produced a material with high mobility solution. The obtained black suspension is cen-
of charge carriers at room temperature. As the trifuged and the resultant reduced graphene
scale-up of this procedure is very difficult, other oxide (rGO) is treated with hydrochloric acid
methods have been proposed for synthesis of solution, deionized water and methanol. After

Figure 13: Schematic representations of graphite (a) and graphene (b) structures. Adapted from https://br.pinterest.com/nonikatz/graphene/

Instituto de Pesquisas Energéticas e Nucleares