Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 1Citation - Scopus: 1Electrochemical Evaluation of Strontium-Doped Micro-Arc Oxidation Surfaces on Titanium(Mdpi, 2025) Alves, Alexandra C.; Duraes, Carolina; Toptan, FatihTitanium (Ti) alloys are widely used in biomedical applications but face challenges like poor biological activity and corrosion at modular interfaces. Strontium (Sr)-doped micro-arc oxidation (MAO) surfaces are proposed to improve biocompatibility and tribocorrosion resistance. This study examines the electrochemical behaviour of Ti surfaces treated with 0.0013 M and 0.13 M Sr-doped MAO via open circuit potential, potentiodynamic polarisation, and electrochemical impedance spectroscopy in a basic physiological solution at 37 degrees C. The results indicate that higher Sr concentrations led to lower passivation current densities (more than two times lower than at the lowest Sr concentration) and reduced barrier layer capacitance (more than one and a half times lower than at the lowest Sr concentration), suggesting improved corrosion resistance for Sr-enriched MAO treatments on Ti implants.Review Citation - WoS: 14Citation - Scopus: 16Advancing Titanium-Based Surfaces Via Micro-Arc Oxidation With Solid Substance Incorporation: a Systematic Review(Elsevier, 2024) Ogur, Ezgi; Alves, Alexandra C.; Toptan, FatihDespite possessing numerous superior properties, titanium, and its alloys exhibit inadequacies in terms of tribocorrosion, bioactivity, and antimicrobial characteristics. In recent years, there has been a rapid increase in research focusing on micro-arc oxidation (MAO) surface treatments to enhance these properties. In the traditional MAO approach, researchers commonly investigate the introduction of additional functionalities to the surface through ion doping. However, over the past decade, studies have indicated that the inclusion of solid substances, either as substitutes for or in conjunction with ion doping, can provide further advantages in terms of multifunctionality. Therefore, this review comprehensively and systematically examines the characteristics of solid substances used during MAO, their incorporation mechanisms, and their influence on resulting biological and degradation behaviors, as well as properties such as photocatalytic activity, magnetic features, hightemperature oxidation resistance, electrical insulation, and thermal shock resistance. This review showed that the integration of solid substances during MAO represents a promising avenue for achieving multifunctional surface enhancements in titanium and its alloys. This review highlights the diverse range of properties and behaviors influenced by these solid substances, offering insights for future research and applications in the field of surface engineering and biomaterials science.Article Citation - WoS: 5Citation - Scopus: 8Micro-Arc and Thermal Oxidized Titanium Matrix Composites for Tribocorrosion-Resistant Biomedical Implants(Elsevier Science Sa, 2024) Sousa, Luis; Costa, Natalia A.; Rossi, Andre; Simoes, Sonia; Toptan, Fatih; Alves, Alexandra C.Superior tribocorrosion resistance is offered by titanium matrix composites (TMCs) compared to their unreinforced matrix metal, but bioactivity concerns are raised for biomedical applications. Simple methods such as micro -arc oxidation (MAO) and thermal oxidation (TO) are employed to enhance the bioactivity and degradation resistance of Ti. However, the impact of those surface treatments on TMC surfaces is poorly understood. Therefore, the present work aimed to explore the influence of MAO and TO treatments on the surfaces of in - situ Ti-TiB-TiC and ex - situ Ti-B 4 C composites, and to assess their corrosion and tribocorrosion performance. Corrosion and tribocorrosion tests were conducted in phosphate-buffered saline solution (PBS) at body temperature. Electrochemical assays were performed by means of potentiodynamic polarization scans while additional potentiostatic tests were performed for the untreated ex - situ composites. Tribo-electrochemical assays were conducted under open circuit potential (OCP) and under normal loads of 0.5 and 10 N against a 10 mm diameter alumina ball in a reciprocating ball -on -plate tribometer. Results revealed reinforcement detachments in ex - situ composites after both treatments. This was primarily attributed to oxide layer growth at the reinforcement/reaction zone interface. Hence, the use of MAO and TO on ex - situ Ti-B 4 C composites may not be appropriate for biomedical applications, mainly because the B 4 C particles tend to detach during the treatment. In contrast, TOtreated in - situ composites displayed excellent combination of corrosion and tribocorrosion performance, even under elevated applied loads, mainly due to the existence of the oxygen diffusion zone (ODZ) beneath the oxide surface produced by TO, together with the more stable electrochemical properties observed during steady -state conditions.Article Citation - WoS: 8Citation - Scopus: 8Crystallization and Additional Oxide Interlayers Improve the Tribocorrosion Resistance of Tio2 Nanotubular Surfaces Formed on Ti6al4v(Elsevier, 2023) Çaha, İhsan; Türü, İrem Cemre; Erdoğan, Ece; Pinto, Ana Maria Pires; Cansever, Nurhan; Deepak, Francis Leonard; Toptan, Fatih; Alves, Alexandra C.TiO2-based nanotubular surfaces have promising properties for various industrial applications, such as solar cells, fuel cells, photocatalysis, energy storage, gas sensors, and biomedical applications. However, they have very limited use in real applications, and one of the major limiting factors is the weak adhesion of nanotubular surfaces to the substrate. In this study, nanotubular surfaces are formed on Ti6Al4V alloy by anodic treatment followed by a heat treatment at 500 °C for 3 h under an open atmosphere. Microstructural investigations revealed self-organized nanotubes grown on both ? and ? phases. High-resolution TEM/STEM analysis showed crystallization of the nanotubular layer and formation of additional oxide interlayers resulting in a drastic improvement in tribocorrosion resistance. These findings indicated that a simple heat treatment can significantly alter the properties of nanotubular layers and can widen their usage mainly for load-bearing implant applications in corrosive environments. © 2023 Elsevier B.V.Article Citation - WoS: 24Citation - Scopus: 27Atomic–scale Investigations of Passive Film Formation on Ti-Nb Alloys(Elsevier, 2023) Çaha, İhsan; Alves, Alexandra C.; Chirico, Caterina; Maria Pinto, Ana; Tsipas, Sophia; Gordo, Elena; Bondarchuk, Oleksandr; Leonard Deepak, Francis; Toptan, FatihThis study extensively investigates the passive film formation mechanisms on Ti-xNb alloys by using several electrochemical techniques, including electrochemical impedance spectroscopy (EIS) before and after potentiostatic polarization at the passive zone, and Mott-Schottky (MS) measurements in 9 g/l NaCl electrolyte at 37 °C, together with X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis. Overall, the Ti40Nb presented lower corrosion resistance due to a thinner passive film as compared to commercial pure Ti (grade 2) and Ti12Nb. The passive film formed on Ti12Nb and Ti40Nb alloys at a steady-state condition (+0.5 VAg/AgCl for 60 min) is composed of amorphous phases of TiO, Ti2O3, TiO2, Nb2O5 and crystalline phases of TiO2 (anatase) and Nb2O5. © 2022 Elsevier B.V.Article Citation - WoS: 1Citation - Scopus: 1Influence of Processing Method of Cocrmo Dental Alloy on the Corrosion Behavior in Artificial Saliva(Wiley, 2022) Pontes, Joana R.; Pinto, Ana M. P.; Ariza, Edith; Alves, Alexandra C.; Toptan, FatihRemovable or fixed dental frameworks are usually made of CoCr alloys. The CoCr dental alloys are produced traditionally by lost-wax casting. However, alternative processing routes, such as hot-pressing, are being studied for dental applications. The purpose of the present work was to assess the corrosion resistance of CoCrMo dental alloy produced by conventional lost-wax casting and hot-pressing. The corrosion behavior was studied in artificial saliva at 37°C by potentiodynamic polarisation tests. Immersion tests were performed to evaluate the growth of the passive film where electrochemical impedance spectroscopy was used at different immersion periods. Results showed slightly better corrosion resistance in terms of ipass for CoCrMo samples obtained by hot-pressing. On the other hand, the immersion tests showed a more stable and thicker passive film formed on hot-pressed CoCrMo dental alloy, pointing out that hot-pressing may be considered a promising technique to produce CoCrMo dental structures.Article Citation - WoS: 20Citation - Scopus: 20Preliminary Tribo-Electrochemical and Biological Responses of the Ti-Tib In-Situ Composites Intended for Load-Bearing Biomedical Implants(Elsevier, 2022) Sousa, Lia; Toptan, Fatih; Alves, Alexandra C.; Costa, N. A.; Gemini Piperni, Sara; Rossi, Andre Linhares; Ribeiro, Ana R.; Simöes, Sönia; Toptan, FatihPoor tribocorrosion resistance of Ti and its alloys remains as a concern for load-bearing biomedical implants. Despite being an effective method to improve tribocorrosion resistance, titanium matrix composites (TMCs) have yet to be used in this type of applications. In-situ TiB (titanium boride) and TiC (titanium carbide) reinforcement phases have been considered as one of the best options to produce TMCs once these phases present high compatibility and strong interfacial bonding with Ti. Although the effect of these phases on the mechanical properties of Ti has been thoroughly researched in the last years, their effect on corrosion, tribocorrosion and biocompatibility of Ti is yet to be fully understood. In this work, in-situ Ti-TiB-TiCx composites obtained by reactive hot pressing showed identical corrosion response compared to the unreinforced Ti but displayed improved tribocorrosion behaviour. Under 0.5 N load, composites presented as average a reduction of 51% in wear volume loss and under 10 N the reduction was up to 93%. Early biological tests showed promising results, as composites were biocompatible and induced osteoblasts spreading and possibly proliferation most probably due to composite chemistry and surface hardness.Article Citation - WoS: 22Citation - Scopus: 27Improved Tribocorrosion Behavior on Bio-Functionalized Β-Type Titanium Alloy by the Pillar Effect Given by Tin Reinforcements(Elsevier, 2021) Çaha, İhsan; Alves, Alexandra C.; Chirico, Caterina; Pinto, Ana Maria; Tsipas, Sophia; Gordo, Elena; Toptan, FatihA novel multi-functional material was developed by hard TiN particle reinforcement addition to a beta-type Ti alloy, following by bio-functionalization of its surface through Ca and P rich oxide layer. Corrosion and tribocorrosion behavior of this multi-functional material was investigated in phosphate buffer solution at body temperature. Bio-functionalization drastically improved the corrosion and tribocorrosion behavior of the unreinforced and reinforced samples, where the bio-functionalized beta-type titanium alloy matrix composite presented the best tribocorrosion behavior due to the load-carrying role of the hard reinforcement phase that gave a support to the functionalized surface layer.