1. Faculty of Applied Chemistry and Materials Science University 'Politehnica' of Bucharest, Polizu Street, no. 1, 011061, Bucharest, Romania;, Email: ioana_laca@yahoo.com
2. Faculty of Applied Chemistry and Materials Science University 'Politehnica' of Bucharest, Polizu Street, no. 1, 011061, Bucharest, Romania
3. Faculty of Materials Science and Engineering University 'Politehnica' of Bucharest, Splaiul Independentei Street, no. 313, Bucharest, Romania