1. Institute of Energetics and Interphases, National Research Council (IENI-CNR), Via De Marini 6, I-16149 Genoa, Italy
2. Centre des Matériaux, Ecole des Mines de Paris, BP 87, 91000 Evry, France
3. Department of Process and Chemical Engineering, University of Genoa, Fiera del Mare, Pad.D., I-16129 Genoa, Italy