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Electrochemical Synthesis of Macroporous Oxide Coatings on Stainless‐Steel Substrates
Author(s) -
Prasad Belavalli E.,
Kamath P. Vishnu,
Upadhya Sarala
Publication year - 2008
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2008.02792.x
Subject(s) - oxide , materials science , hydroxide , chemical engineering , micrometer , porosity , electrochemistry , crystallite , lamellar structure , aqueous solution , thermal decomposition , deposition (geology) , metal , inorganic chemistry , metal hydroxide , metallurgy , composite material , chemistry , organic chemistry , electrode , paleontology , physics , optics , sediment , engineering , biology
Cathodic reduction of aqueous metal nitrate solutions leads to the deposition of micrometer‐thick coatings of metal hydroxides. Heat treatment of the green hydroxide deposits results in the formation of adherent oxide coatings. The synthesis of a number of oxides such as MgO, Co 3 O 4 , and RE 2 O 3 (RE=Y, Dy, and Eu) is reported. These oxides as well as their hydroxide precursors belong to different structure types, showing that electrochemical deposition is a general method of fabrication of oxide coatings. The distinctive feature of all the precursor coatings is that they are macroporous, with the pore size in the micrometer range. The pores arise from the truncation of lamellar crystallites. The porosity is morphological rather than structural and is caused by aggressive gas evolution that takes place simultaneously with the deposition process at the cathode. The oxide coatings obtained by the thermal decomposition of the hydroxide precursors are also macroporous. The porosity is conserved as the pore size is larger than the diffusion length at the decomposition temperature.