Synthesis of Composite Coating Containing TiO 2 and HA Nanoparticles on Titanium Substrate by AC Plasma Electrolytic Oxi
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IN the last decades, titanium alloys have been commonly utilized in medical and biomaterial applications due to their biocompatible properties.[1] Yerokhin et al.[2] studied the effect of both concentration and current density on growth rate, microstructure, and mechanical properties of Ti-6Al-4V alloy processed through various coating methods. Based on their study, growth rate of the coatings was enhanced by increasing electrolyte concentration. Liu et al.[3] examined the effect of voltage, temperature, and time on morphology, elemental composition, and adhesion strength of the applied coatings on Ti-6Al-4V alloys. They demonstrated that size of micropores became larger by raising the voltage, and the Ca/P ratio is independent of applied voltage or current density, and it can be adjusted through solution concentration. In some other studies, the effect of time on microstructure, morphology,
M. SOLEYMANI NAEINI, M. GHORBANI, and E. CHAMBARI are with the Materials Science and Engineering Department, Sharif University of Technology, Tehran, Iran. Contact e-mail: [email protected] Manuscript submitted November 16, 2018. Article published online May 3, 2019 3310—VOLUME 50A, JULY 2019
porosity, and thickness of coatings was investigated.[4–9] It was reported that the oxidation layer thickness would increase and growth rate would experience a decrease by increasing growth time. Furthermore, mechanical defects started to appear in the coatings as growth exceeded beyond a certain point.[10] One of the major parameters in synthesis of plasma electrolytic oxidation (PEO) coatings is applied voltage. It is demonstrated that by increasing voltage, pore size increases, but the number of pores is decreased. Besides, the intensity of applied voltage affects the phase composition of the coating layers. Applying both anodic and cathodic voltage has an undeniable impact on the structural, physical, and chemical properties of the layer formed in PEO in which pulse current power supply is utilized.[3,11] The type and concentration of electrolytes are considered as two effective parameters in the formation of the microstructure and the chemical composition of coating layers. One of the most common electrolyte compositions for PEO of Titanium alloys contains salts including calcium, phosphor, aluminum, and molybdenum ions.[7] Considering the phosphate aluminate coating process, the abrasion resistance of the layer formed in electrolytes containing phosphate is the highest in comparison with others. By comparing the corrosion resistance of different coatings, it is proved that phosphate electrolytes have suitable corrosion properties. METALLURGICAL AND MATERIALS TRANSACTIONS A
Moreover, silicate–phosphate electrolytes result in higher hardness and a lower elastic modulus in comparison with non-coated samples.[10,12] The purpose of this study is the investigation of AC-PEO processing of applied nanocomposite coatings containing TiO2 and hydroxyapatite (HA) nanoparticles on a commercial Ti substrate to characterize nanoparticles by vari
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