1. Department of Materials Science and Envoronment, “DUNĂREA DE JOS” University of Galaţi, Domnească 111, 800201, Galaţi, Romania, flmarin@ugal.ro
2. Department of Materials Science and Envoronment, “DUNĂREA DE JOS” University of Galaţi, Domnească 111, 800201, Galaţi, Romania