Jelena Gulicovski

Protective ability and impedance response of sol–gel reversely transformed ceria conversion coating on aluminium

Ceria coating is formed on Al from the ceria sol prepared exclusively by forced hydrolysis of Ce(NO3)4, in order to test their ability to protect Al from corrosion. The characterization of sol–gel-processed ceria coating and coating/Al assembly brings new issues on Al corrosion and protection caused by unique properties of the sol–gel coating. The corrosion behaviour of bare Al and Al/CeO2 is investigated by the electrochemical impedance spectroscopy (EIS) during the exposure to NaCl aqueous solution. The morphology and composition of the samples are examined by scanning electron microscopy and energy dispersive spectroscopy. EIS data showed greater corrosion resistance of CeO2-coated aluminium in comparison to bare Al at long exposure times. CeO2 coating does not hinder completely the corrosion processes on Al. The Al beneath CeO2 coating is subjected to intrinsic formation of a uniform protective coating/Al interphase, cross-linked by AlO(OH) fibre-like structures. They appear created by corrosive medium from the coating reversely gelled by NaCl solution. As the fibre network is created during exposure, Al becomes better protected than by spontaneous formation of porous passive layer of Al(OH)3 on bare aluminium. Sol–gel ceria coatings thus improve corrosion resistance of aluminium during prolonged exposure to corrosive medium.

Studies on Structural and Morphological Properties of Multidoped Ceria Ce0.8Nd0.0025Sm0.0025Gd0.005Dy0.095Y0.095O () as Solid Solutions

The nanopowdery solid solutions of multidoped ceria Ce0.8Nd0.0025Sm0.0025Gd0.005Dy0.095Y0.095 () with the fluorite type crystal structure of CeO2 were synthesized for the first time. Two synthesis procedures were applied: the modified glycine-nitrate procedure (MGNP method) and room temperature self-propagating reaction (SPRT method). All nanopowders were characterized by XRPD analysis, Raman spectroscopy, low temperature nitrogen physisorption, TEM, and SEM methods. According to the XRPD and Raman spectroscopy results, single phase solid solutions of fluorite structure were evidenced regardless of the number of dopants and synthesis procedure. Both XRPD and TEM were analyses evidenced nanometer particle dimensions. The SPRT method results in obtaining sample with higher specific surface area, smaller crystallite and particles sizes, and the same values of the lattice parameter in comparison to pure CeO2. Raman spectroscopy was confirmed to the oxygen vacancies introduced into the ceria lattice when Ce4