Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Ti-Cu Dry Electrodes for Biomedical Sensing: Tribocorrosion Performance Under Simulated Skin Conditions(Elsevier, 2025) Alves, A. C.; Lopes, C.; Camarinha, A.; Geraldo, D.; Toptan, F.; Ferreira, A.; Vaz, F.Monitoring electromyographic (EMG) activity is crucial for diagnosing musculoskeletal disorders and understanding neuromuscular systems. Dry electrodes represent a significant advancement over traditional wet electrodes by eliminating the need for gels, thereby extending lifespan, simplifying skin preparation, and facilitating prolonged remote monitoring. However, challenges such as higher impedance and susceptibility to motion artifacts, along with issues of user discomfort and signal distortion, persist with existing metal-coated or entirely metal dry electrodes. This study explores an alternative approach using Ti-Cu thin films deposited on polymeric substrates to enhance electrical, electrochemical, and tribo-electrochemical properties. The research specifically investigates the corrosion and tribocorrosion behaviour of these Ti-Cu thin films in an artificial sweat environment, comparing them to pure Ti and Cu films. Chemical, microstructural, topographical, and electrical characterizations were conducted, alongside evaluations of electrochemical and tribo-electrochemical behaviour. The results indicate that while all films showed rupture under sliding, TiCu0.34 thin films exhibited superior corrosion resistance due to their unique microstructure. This study suggests that TiCu0.34 electrodes may offer a promising balance between corrosion resistance and electrical performance for wearable applications, although improvements in adhesion are necessary to withstand mechanical loads.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: 10Impact of Simulated Inflammation and Food Breakdown on the Synergistic Interaction Between Corrosion and Wear on Titanium(Elsevier Ltd, 2024) Lima,A.R.; Pinto,A.M.P.; Toptan,F.; Alves,A.C.This paper investigates the impact of lactic acid and phosphoric acid additives in artificial saliva (AS), simulating inflammation and food breakdown, on the electrochemical and tribo-electrochemical behavior of titanium. The results showed that, unlike lactic acid, phosphoric acid significantly reduced corrosion resistance, mainly due to local damage and heterogeneities on the passive film. Non-additivated AS caused greater wear volume loss, with mechanical wear identified as the main mechanism. However, when additives were present, a synergistic interplay between corrosion and wear was observed. The study concludes that prolonged exposure to food breakdown could accelerate material degradation in titanium. © 2024 Elsevier LtdArticle Citation - WoS: 8Citation - Scopus: 10Impact of Simulated Inflammation and Food Breakdown on the Synergistic Interaction Between Corrosion and Wear on Titanium(Elsevier, 2024) Lima, A.R.; Pinto, A.M.P.; Toptan, F.; Alves, A.C.This paper investigates the impact of lactic acid and phosphoric acid additives in artificial saliva (AS), simulating inflammation and food breakdown, on the electrochemical and tribo-electrochemical behavior of titanium. The results showed that, unlike lactic acid, phosphoric acid significantly reduced corrosion resistance, mainly due to local damage and heterogeneities on the passive film. Non-additivated AS caused greater wear volume loss, with mechanical wear identified as the main mechanism. However, when additives were present, a synergistic interplay between corrosion and wear was observed. The study concludes that prolonged exposure to food breakdown could accelerate material degradation in titanium. © 2024 Elsevier LtdArticle Citation - WoS: 14Citation - Scopus: 20Influence of Al2o3 Reinforcements and Ti-Al Intermetallics on Corrosion and Tribocorrosion Behavior of Titanium(Elsevier, 2023) Sousa, Luis; Antunes, Rui D. M.; Fernandes, Joao C. S.; Alves, Alexandra Cruz; Toptan, FatihTi-Al2O3 composites have demonstrated favorable characteristics for use in load-bearing biomedical implant applications; however, the influence of Al2O3 reinforcement particles and Ti-Al intermetallics on the electrochemical and tribo-electrochemical responses of Ti are not well-understood. This study explored the corrosion and tribocorrosion characteristics of powder metallurgy-manufactured Ti-Al2O3 composites in a simple physiological saline solution at body temperature. Electrochemical analysis was performed by electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization and tribo-electrochemical mechanisms were explored under open circuit potential (OCP) against a 10 mm diameter alumina ball in a ball-on-plate tribometer with reciprocating configuration. Results revealed that the corrosion behavior of Ti was adversely affected by the development of a heterogeneous oxide film on the Ti matrix and the Ti-Al intermetallic phases formed by the interaction of Ti and Al2O3 particles. However, there was a drastic improvement in tribocorrosion behavior, evidenced by decreased corrosion tendency under sliding and a marked reduction in wear volume, primarily as a result of the decreased wear damage resulting from the load-bearing reinforcements.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: 3Citation - Scopus: 6Investigation of the Influence of High-Pressure Torsion and Solution Treatment on Corrosion and Tribocorrosion Behavior of Cocrmo Alloys for Biomedical Applications(MDPI, 2023) Yılmazer, Hakan; Caha, İhsan; Dikici, Burak; Toptan, Fatih; Işık, Murat; Niinomi, Mitsuo; Nakai, Masaaki; Alves, Alexandra CruzIn this study, the influence of the high-pressure torsion (HPT) processing parameters and solution treatment (ST) on the corrosion and tribocorrosion behavior of CoCrMo (CCM) alloys was investigated for possible usage in biomedical applications. The corrosion behavior of the CCM alloys was investigated by using potentiodynamic scanning (PDS) and electrochemical impedance spectroscopy (EIS) tests. Tribocorrosion tests were carried out in a reciprocating ball-on-plate tribometer at 1 Hz, 1 N load, and 3 mm stroke length for 2 h. All electrochemical measurements were performed using a potentiostat in standard phosphate-buffered saline (PBS) solution at body temperature (37 +/- 2 degrees C). The samples were characterized by using a scanning electron microscope (SEM), transmission electron microscope (TEM), optical microscope (OM), and X-ray diffraction (XRD). The deepness and width of wear tracks were examined by using a profilometer. The results showed that HPT and ST processes did not affect significantly the corrosion resistance of samples. However, the ST-treated samples had a higher material loss during sliding in standard phosphate-buffered saline (PBS) at body temperature as compared to HPT-treated samples.Article Citation - WoS: 6Citation - Scopus: 6Tribocorrosion-Resistant Ti40nb-Tin Composites Havingtio(2)-Based Nanotubular Surfaces(American Chemical Society, 2022) Çaha, İhsan; Alves, Alexandra Cruz; Chirico, Caterina; Pinto, Ana Maria; Tsipas, Sophia; Gordo, Elena; Toptan, FatihA novel multifunctional material was developed byhard TiN particle reinforcement addition to a beta-type Ti40Nb alloy,followed by surface functionalization, yielding the formation of ananotubular layer. Corrosion and tribocorrosion behaviors wereinvestigated in a phosphate-buffered saline solution at bodytemperature. The results revealed that the Ti40Nb-TiNcomposites presented similaripassandE(i=0)values together withrelatively similarRoxandCox. However, its tribocorrosion resistancedrastically improved (wear volume is almost 15 times lower than anunreinforced alloy) as a consequence of the load-carrying effectgiven by the reinforcement phases. The corrosion and tribocorro-sion behaviors were further improved through surface functionaliza-tion as observed by significantly loweripassand higherRoxvalues andalmost undetectable wear volume loss from tribocorrosion tests dueto the formation of a well-adhered anatase-rutile TiO2-based nanotubular layer.Article Citation - WoS: 10Citation - Scopus: 11Improved Tribocorrosion Behavior Obtained by In-Situ Precipitation of Ti2c in Ti-Nb Alloy(MDPI, 2022) Gonçalves, Vinícius Richieri Manso; Çaha, İhsan; Alves, Alexandra Cruz; Toptan, Fatih; Rocha, L. A.Novel in-situ Ti-based matrix composites (TMCs) were developed through the reactive hot pressing of Ti + NbC powder blends. Due to the chemical reaction that occurred in the solid-state during processing, the produced samples were composed of an Nb-rich β-Ti phase that formed a metallic matrix along with Ti2C as a reinforcing phase. By employing different proportions of Ti:NbC, the phase composition of the alloys was designed to contain different ratios of α-Ti and β-Ti. The present work investigated the corrosion and tribocorrosion behavior of the composites, compared to unreinforced Ti, in a phosphate-buffered solution (PBS) at body temperature. Corrosion tests included potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Tribocorrosion tests were carried out using a ball-on-plate tribometer with sliding performed at open circuit potential (OCP) and under anodic potentiostatic conditions. Results showed that the stabilization of the β phase in the matrix led to a decrease in the hardness. However, the formation of the in-situ reinforcing phase significantly improved the tribocorrosion behavior of the composites due to a load-carrying effect, lowering the corrosion tendency and kinetics under sliding. Furthermore, localized corrosion was not observed at the interface between the reinforcing phase and the matrix.Article Citation - WoS: 10Citation - Scopus: 10Influence of Calcium Acetate Concentration in Electrolyte on Tribocorrosion Behaviour of Mao Treated Titanium(MDPI Multidisciplinary Digital Publishing Institute, 2021) Sousa, Luis; Mendes, Ana Rita; Pinto, Ana Maria Pires; Toptan, Fatih; Alves, Alexandra CruzTi-based materials are widely used for dental and orthopaedic implant applications due to their adequate mechanical properties, corrosion behaviour and biocompatibility. However, these materials are biologically inert and display poor wear resistance. In one of the most studied processes that aims to overcome these drawbacks, Ti surfaces are often covered by anodic oxide films with the incorporation of bioactive agents such as Ca and P. Although there are several works on the tribocorrosion behaviour of MAO-treated Ti surfaces, the influence of electrolyte composition on the corrosion kinetics under sliding is yet to be fully understood. In the present work, anodic oxide films were produced on cp-Ti surfaces with different calcium acetate concentrations in the electrolyte. Tribocorrosion behaviour was investigated by reciprocating sliding tests performed in 8 g/L NaCl solution at body temperature, under potentiostatic conditions. The results showed that higher concentrations of calcium acetate had a detrimental effect on tribocorrosion kinetics, however, they resulted in less mechanical damage due to alterations in the topography and structure of the MAO layer.