Electrochemical Impedance Spectroscopy and Corrosion Behavior of Co/CeO 2 Nanocomposite Coatings in Simulating Body Flui
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IN recent years, much attention has been focused on the research and development of metal matrix composite coatings (MMC) because such materials offer outstanding mechanical and multifunctional properties. Composite coatings are produced by codeposition of inert particles into a metal matrix from an electrolytic or electroless bath being considered as MMC coatings. This technique is receiving increased interest because of its ability to produce films with excellent mechanical properties such as wear resistance, corrosion resistance, and lubrication.[1–8] There are reports on the incorporation of nanosized SiC, ZrO2, Al2O3, TiO2, La2O3, and CeO2 in the nickel matrix forming composites.[3,5,9–16] The incorporated inert particles have played an important role in either enhancing the corrosion resistance or the wear resistance, a lot of work is being done on the nickel matrix. There are reports on the synthesis and properties of Ni/Al2O3 and Ni/ZrO2 composite coatings.[5,6,10] However, to the best of our knowledge, there are no reports on the synthesis and properties of cobalt composite coatings containing a bioceramic oxide powder like CeO2 at 25-nm size. When organized well, the benefits of the individual components play a synergistic role in the final properties of the metal matrix composite coatings obtained.[17–25] When speaking about composite coatings used as biocoatings LIDIA BENEA, University Professor, is with Research (Competences) Centre Interfaces Tribocorrosion and Electrochemical Systems (CC-ITES), Materials Science and Environment, Dunarea de Jos University of Galati, 800008 Galati, Romania. Contact e-mails: Lidia. [email protected]; [email protected] Manuscript submitted November 21, 2011. Article published online October 2, 2012 1114—VOLUME 44A, FEBRUARY 2013
materials, metals are generally chosen for their mechanical properties, whereas ceramics may offer bioactivity, resorption, or hardness. Cobalt is already used in biomedical applications. Cerium oxide (ceria), CeO2, is considered one of the most important ceramic materials in modern technology. Combining the cobalt as a metal matrix with cerium oxide as a dispersed phase, the resulting composite coating could give some interesting properties with possibilities to use them as biomaterials or wear- and corrosion-resistant coatings. Moreover, there are very few references in the literature regarding the electrodeposition of ceramic particles in the cobalt matrix[26,27]; many studies are done on electrodeposited nickel matrix.[10–16,19–25] In the current work, efforts have been made to characterize surface-modified cobalt with CeO2 nanosized bioceramic particles (mean diameter 25 nm), in order to improve the corrosion resistance in simulating body fluid solutions. In the literature, there are very limited studies in the dispersion of inert nanoparticles in the cobalt matrix and the corrosion properties of obtained coatings. Recently, cobalt–carbon nanotubes composite and their electrochemical properties[28] were studied. The preparation of cobalt-perfluor
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