Page 296 - 00. Complete Version - Progress Report IPEN 2014-2016

296 Materials and Nanotechnology | Progress Report

Chemical Synthesis thesis of graphene layers. CVD has been pro-
and Processing of posed for production of large area films and

Ceramic Powders wet-chemical treatment of graphite has been
indicated for preparation of small graphene-
based platelets. The latter is suitable for appli-
Graphene synthesis for energy cations in energy conversion and storage sys-
and biomedical applications tems and ceramic biocomposites, which is the

focus of the researches developed at Ceramic
Graphene is an allotropic form of carbon Raw Materials Laboratory of IPEN. Besides the
packed in two-dimension layer (2D) with hon- experimental facilities concerning the use of
eycomb lattice structure that can be isolated homogeneous colloidal suspensions, the low-
from graphite (Figure 13). Its remarkable tech- cost production makes this method an attrac-
nological importance is due to the outstanding tive choice.
physical and chemical properties such as elec-
trical and thermal conductivity, elastic modu- The graphene synthesis procedure employed
lus, fracture strength, flexibility, surface area, by Ceramic Raw Materials group was adapt-
adsorption and desorption capacity of gases ed from the method developed by Hummers
and biocompatibility. Experimental and the- and Offeman in 1958 and improved by Mar-
oretical studies on the synthesis and proper- cano et al in 2010 in order to enhance safety.
ties of graphene have been carried out since Typically, graphite flakes (G) is oxidized with a
the nineteenth century, but its popularity was mixture of concentrated sulphuric and phos-
motivated from the paper of Nobel Laureates phoric acids followed by addition of potassi-
Geim and Novoselov, published in 2004, in um permanganate and hydrogen peroxide un-
which the physical effects predicted in theo- der specific conditions of stirring and heating.
retical studies were confirmed experimental- The mixture is centrifuged and the remaining
ly. Using a simple method of mechanical ex- solid material is sonicated with deionized wa-
foliation of graphite sheets by adhesive tapes, ter. This material, denominated graphene ox-
it was produced a material with high mobili- ide (GO), is further reduced with acid ascorbic
ty of charge carriers at room temperature. As solution. The obtained black suspension is cen-
the scale-up of this procedure is very difficult, trifuged and the resultant reduced graphene
other methods have been proposed for syn- oxide (rGO) is treated with hydrochloric acid

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