Recubrimientos de Pd (Ag)-ZrO2 obtenidos por CVD para electrodos utilizados en la purificación electroquímica de aguas de desecho

Abstract

In this research Pd – ZrO2 composite thin films were synthetized by Metalorganic Chemical Vapor Deposition (MOCVD) in order to obtain anticorrosive coatings for electrodes used in the technique of water treatment called Electrodyalisis. Coatings were deposited on AISI 304L stainless steel substrates in ratios of 10 – 90, 20 – 80 and 30 – 70 wt % Pd and Zr precursors (acetylacetonates) respectively, and temperatures of 450, 500 and 550 °C. Gas flows were adjusted at 130 cm3min-1 at ratio of 20 – 80 % vol of O2 – Ar, and pressure was maintained at less than 1 Torr. Structural characterization was carried out through X-Ray Diffraction (XRD) showing the presence of metallic palladium and zirconia in cubic and tetragonal phases; palladium diffusion inside zirconia matrix was influenced by deposition temperatures and compositions. Topographic characterization was performed by Atomic Force Microscopy (AFM), films showed a uniform and columnar growth; dome size and roughness were acquired with this technique too. Temperature effect on morphology and electrochemical behavior was clearly demonstrated by Scanning Electron Microscopy (SEM) and Electrochemical techniques respectively: highly compact and crackless morphology was showed at lower temperatures and medium compositions, the highest charge-transfer resistance was also obtained at this temperature; whereas mores stresses appeared in the film and the charge-transfer resistance decreased significantly at higher temperatures.