1. Department of Chemical Engineering, School of Engineering; Federal University of Minas Gerais; Avenida Presidente Antônio Carlos, 6627, Belo Horizonte Minas Gerais 31270-901 Brazil
2. Department of Physics; Federal University of Minas Gerais; Avenida Presidente Antônio Carlos, 6627, Belo Horizonte Minas Gerais 31270-901 Brazil