SOLAR SELECTIVE COATINGS BASED ON FE-CR-A L OXIDE - TEXTURAL AND PHYSICAL-CHEMICAL STUDY

Optical selective surfaces have been prepared by superficial chemical conversion of refractory steel containing aluminium. The texture has b een analysed by scanning electron microscopy (S.E.M.) and by electroch emical impedance spectrometry. The physical-chemical characterization has been achieved by S.I.M.S., E.S.C.A./XPS and R.H.E.E.D. These surfa ces are rough and mesoporous. The films present a fractal character an d a composition gradient. The nature and the distribution of the main components in the coating are close to that observed in the coating ob tained from non-refractory ferritic steel. One of the differences betw een the coatings is related to the presence of magnetite substituted b oth with chromium and aluminium.