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Öğe Biodegradability of ?-Mg17Al12 phase in simulated body fluid(Elsevier, 2012) Kannan, M. Bobby; Koc, Erkan; Unal, MehmetIn vitro degradation behaviour of beta phase (Mg17Al12), commonly present in AZ series magnesium alloys, was studied using electrochemical techniques in simulated body fluid. The experimental results suggested that the degradation rate of beta phase was significantly lower than that of pure magnesium. Scanning electron microscopy (SEM) analysis of the polarized beta phase revealed localized corrosion. (C) 2012 Elsevier B.V. All rights reserved.Öğe A COMPARATIVE STUDY ON THE MECHANICAL AND CORROSION PROPERTIES OF THE ZM20 AND ZM21 ALLOYS AFTER CASTING AND ROLLING(Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2022) Goren, Haul Ahmet; Unal, Mehmet; Turen, Junus; Ahlatci, Hayrettin; Sun, YavuzIn this study, the effects of grain refinement and production methods on the corrosion, corrosive wear and mechanical properties of the as-cast and as-rolled Mg-2 wt.% Zn (ZM20) and Mg-2 wt.% Zn-0,51 wt.% Mn (ZM21) alloys were examined by using OM, XRD, SEM, hardness and uniaxial tensile test. Additionally, the potentiodynamic polarization, immersion corrosion test and corrosive wear properties of the ZM20 and ZM21 alloys were compared. According to the XRD results, MgZn and MgZn2 phases were found in the alloys and also MnZn3 phase occurred in the ZM21 alloy with the addition of manganese. Both during solidification forming nucleation points with the added manganese and during rolling the broken secondary phase particles distributed into the matrix prevented grain growth and led to the formation of a more refined structure. The tensile test results showed that the strength of the as-cast ZM21 alloys were better than that of the as-cast ZM20 alloys and further improvement in mechanical properties occurred with the rolling of the both alloys. The most superior hardness was found in the as-rolled ZM21 alloy. In the total 400-m recipro-cal corrosive wear test in the 3.5% NaCl solution, the lowest mass loss was in the as-rolled ZM21 alloys. In the potentiodynamic corrosion test, the highest corrosion resistance was occurred by the as-cast ZM20 alloy.Öğe Ecological Footprint Reduction Behaviors of Individuals in Turkey in the Context of Ecological Sustainability(Mdpi, 2023) Unal, Mehmet; Unal, FatmaWhile people consume natural resources by interacting with the environment, they also cause some environmental changes. Environmental pollution and construction are among the most important reasons for these changes. In addition, the rate of renewal of natural resources remains slow while consumption is increasing. Thus, biocapacity is slow to renew itself compared to consumption, leading to the emergence of an ecological deficit. The largest share in the ecological deficit belongs to personal consumption. Based on this, the attitudes and behavior of individuals in Turkey to reduce their ecological footprint were examined in the context of ecological sustainability. The survey model was adopted in the study. The data collected from 773 people via the scale and various forms were analyzed. The results of the analysis show that the ecological footprint size in Turkey is above the world average in personal consumption. It has been determined that the participants have significant behavioral deficiencies in the behaviors towards reducing the ecological footprint, such as recycling, reusing the product by repairing, composting, not wasting water, food and clothing, and they tend to use packaged products excessively.Öğe The effects of Nd, La, and Ca addition on the corrosion properties of as-cast and as-rolled ZM21 Mg alloys(Edp Sciences S A, 2024) Unal, Mehmet; Goren, Halil AhmetIn this study, the effects of Nd, La, and Ca elements added to ZM21 alloy was investigated in terms of parameters such as microscopic, mechanical, and corrosion properties. The content of each of the elemental constituents was 0.5% by weight. The microstructural and mechanical behaviours of the investigated alloys were examined by XRD, EDX, SEM, OM, hardness surveys, tensile tests, and corrosion experiments. According to the XRD results, Ca5Zn3, Ca2Mg6Zn3, LaZn2, LaMg3, Mg41Nd5, and Mg12Nd phases emerged on the investigated alloys. The grain sizes of the alloys were refined by element addition and rolling process, thus increasing their mechanical properties. Ca increased the hardness of the ZM21 alloys, but this had a negative effect on the rolled specimens. The tensile value of ZM21 alloy as cast decreased by 39.702%, 48.080%, 45.678% with the addition of (0.5% La+0.5% Nd), (0.5% La+0.5% Ca), (0.5% La+0.5% Nd+0.5% Ca), respectively. The tensile value of ZM21 alloy with (0.5% La+0.5% Nd) addition increased by 58.302% as rolled. Tensile test could not be performed because the rolled alloys with 0.5% Ca addition were fragmented during rolling. Ca contributed positively to the corrosion behaviour of the casting ZM21 alloy, but it worsened it in the rolled alloys. White oxide areas on the surface of the rolled alloys indicated an increased degree of corrosion formation.Öğe Influence of zinc on the microstructure, mechanical properties and in vitro corrosion behavior of magnesium-zinc binary alloys(Elsevier Science Sa, 2015) Koc, Erkan; Kannan, M. Bobby; Unal, Mehmet; Candan, ErcanMagnesium-zinc alloy is a potential base material for biodegradable implant applications. In this study, the influence of zinc content (0.5-3 wt.%) in as-cast magnesium-zinc binary alloys towards the microstructure, mechanical properties and in vitro corrosion behaviour was studied. Increase in zinc content reduced the grain size of magnesium-zinc alloy. Mechanical properties such as yield strength, tensile strength and hardness improved with increase in zinc content. Potentiodynamic polarization results suggest that increase in zinc content enhanced the in vitro corrosion resistance of the alloy, which could be attributed to the combined effect of grain size refinement and even distribution of zinc on the alloy surface resulting in better passive film formation. (C) 2015 Elsevier B.V. All rights reserved.Öğe INVESTIGATION OF MICROSTRUCTURE, MECHANICAL AND CORROSION PROPERTIES OF BIODEGRADABLE Mg-Ag ALLOYS(Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2022) Elen, Levent; Turen, Yunus; Ahlatci, Hayrettin; Sun, Yavuz; Unal, MehmetIn this study, microstructure, mechanical, corrosion and corrosive wear properties of Mg-xAg the as-cast and extruded alloys (x: 1, 3 and 5 wt. %Ag) were investigated. According to the experimental results, as the amount of Ag added in the casting alloys increases, the secondary phases (Mg4Ag, Mg54Ag17) emerging in the structure have become more clarified. Furthermore, it was observed that as the amount of Ag increased, the grain size decreased and thus the mechanical properties of the alloys increased. Similarly, the extrusion process enabled the grains to be refined and the mechanical properties to be increased. As a result of the in vitro tests performed, the Mg-1Ag exhibited very bad corrosion properties compared to other alloys. On the other hand, according to corrosive wear tests results, a high wear rate and friction coefficient were found for Mg-5Ag alloys.Öğe Investigation of wear behaviors of C95200-C95300 Cu-Al-Fe alloys(Emerald Group Publishing Ltd, 2009) Yasar, Mustafa; Demiral, Mustafa; Ozyurek, Dursun; Unal, MehmetPurpose - The paper's aim is to examine dry friction properties of the wear behaviors of the manufactured aluminum bronzes (C9500 and C95300) by using pin-on-disk type wear test device. Design/methodology/approach - In this study, alloys were produced by casting C95200 and C95300 aluminum bronzes norms. Produced aluminum bronzes ingot after homogeneous were formed for wearing specimen. These test were conducted on two different alloys, in the sliding velocities 1, 1.5 and 2 m/s, with four different load (25, 37.5, 50 and 62.5 N) and for four different space (500, 1,000, 2,000 and 4,000 m). Wearing specimens tested for hardness and investigated in order to spectral electron microscope photographs. Findings - After investigation, C95200 grain size was bigger than C95300. Furthermore, C95300 alloys were harder than C95200 because of more aluminum. Increasing load, sliding velocity and distance causes increasing wear. Coefficient of C95200 alloys was higher than C95300. Research limitations/implications - Aluminum bronzes show different properties according to the additional elements in them. Reliability of aluminum bronzes can be achieved by the control of chemical composition and the manufacturing method. Practical implications - Very useful information for industries using or planning to produce C95200 and C5300 alloys is provided. Originality/value - This paper identifies a resource need and offers practical help for a manufacturing operation.Öğe Long-term isotretinoin use does not cause parenchymal liver change: Ultrasonographic study in 50 patients(Wiley, 2019) Aktas, Habibullah; Ertugrul, Goksen; Parlak, Muharrem; Unal, MehmetThe effect of isotretinoin on liver enzymes and lipid profile is reported as rare and reversible. However, possible parenchymal liver changes have not been demonstrated so far. The aim of this study was to evaluate the ultrasonography findings of the liver in patients receiving long-term isotretinoin therapy. We examined ultrasonographic findings of the liver together with serum alanin aminotransferase (ALT), aspartate aminotransferase (AST), and total cholesterol and triglyceride levels in 50 consecutive patients who have taken isotretinoin 10-40 mg daily for at least 6 months between January and December 2017. Of 50 patients examined, 40 were female, 10 were male. Mean age of the patients was 24.8 years. Five patients aged between 42 and 62 were found to have Grade 1 hepatosteatosis. Despite a moderate elevation, serum ALT, AST, and total cholesterol and triglyceride levels were in normal range in these five patients. Moreover, one patient had elevated ALT, and one another patient had elevated triglyceride level although both have normal liver ultrasonographic findings. Isotretinoin did not cause parenchymal liver changes as well as serum ALT, AST, and total cholesterol and triglyceride levels in patients who take it 10-40 mg daily for at least 6 months.Öğe Microstructural, mechanical, and in vitro corrosion properties of biodegradable Mg-Ag alloys(Aip Publishing, 2022) Elen, Levent; Turen, Yunus; Ahlatci, Hayrettin; Unal, Mehmet; Ergin, DenizIn this study, casting, extrusion, biocorrosion, and corrosive wear properties of 0.5 wt. % (Zn, Ca, and Nd) element added Mg-3 wt. % Ag alloys were investigated. According to the test results, it was observed that the grain refinement occurred with the effect of Zn and Ca element additions in the as-cast alloys and thus some mechanical properties of the alloys improved. Similarly, the extrusion process provided grain refinement and improved mechanical properties. As a result of in vitro corrosion tests, similar results were also obtained in the as-cast alloys, while this situation became more apparent in the extruded alloys and exhibited more homogeneous corrosion properties. In the corrosive wear tests, the wear rate of the extruded alloys generally showed a decreasing trend. However, both the as-cast and extruded Mg-3 wt. %Ag-0.5 wt. % Ca alloys exhibited the lowest wear rate. Published under an exclusive license by the AVS.
