[1] Univ Fed Rio Grande do Norte, Dept Theoret & Expt Phys, BR-59072970 Natal, RN, Brazil
[2] Univ Fed Rio Grande do Norte, Postgrad Program Mat Sci & Engn, BR-59072970 Natal, RN, Brazil
[3] Univ Aveiro, Dept Mat & Ceram Engn, CICECO, P-3810193 Aveiro, Portugal