1. PETROBRAS S.A./CENPES, Research and Development Centre, Cidade Universitaria, Avenida Jequitiba, 950, 21941-598, Rio de Janeiro-RJ, Brazil, Department of Materials Science and Metallurgy, Pontifical Catholic University, C.P.: 38008, 22453-900 Rio de Janeiro-RJ, Brazil, and Department of Chemistry, University of Rio Grande do Norte, CP 1662, 59078-970, Natal-RN, Brazil