Browsing by Author "Albayrak S."
Now showing 1 - 14 of 14
Results Per Page
Sort Options
Item Effect of Gr Contents on Wear Properties of Al2024/MgO/Al2O3/Gr Hybrid Composites(EDP Sciences, 2018) Ovall I.; Esen C.; Albayrak S.; Karakoç H.In the present study, hybrid metal matrix composites, Al2024/10Al2O3, Al2024/10Al2O3/3MgO, Al2024/10Al2O3/6MgO, Al2024/10Al2O3/3MgO/1.5 Gr, Al2024/10Al2O3/3MgO/3Gr, and reinforcement samples (AA 2024) produced with powder metallurgy process. AA 2024 and reinforcement powders were determined mixture rations and separately mixed during 30 minutes in a three-dimensional Turbula mixer. The mixed compositions were pressed at 300 MPa and sintered at 550°C during 1 h. After that, three materials were extruded at the same temperature. Experimental results show that hybrid metal matrix composites (HMMCs) a better wear resistance than the reinforcement samples because of higher hardness. Gr behave as a lubricant during wear process. The wear resistance of HMMCs can be optimized with controlling of the reinforcement content and type. © 2018 The Authors.Item Characterization of Tantalum Oxide Sol–Gel-coated AZ91 Mg Alloys(Springer, 2020) Gül C.; Albayrak S.; Çinici H.Abstract: Synthesis of tantalum oxide (Ta2O5) powders via sol–gel method and Ta2O5 coating ability onto AZ91 Mg alloy were investigated, in this study. AZ91 Mg alloy was chosen as substrate because of its low density and similar mechanical properties to bone. However, some surface treatments are needed, because the Mg alloy cannot maintain its mechanical integrity in the biological environment for long periods of time. Ta2O5 is a promising coating layer for biomedical applications, because of its excellent corrosion and wear resistance and biocompatibility. In the case of Ta2O5 coatings applied on AZ91 Mg alloy, which is advantageous in many respects, it can be used in long-term applications within the body. The novel study aims for the characterization of Ta2O5-coated AZ91 Mg alloys. AZ91 Mg alloy samples were produced using a powder metallurgy method. The Ta2O5 solution was prepared by sol–gel method. The prepared solution was used for both powder producing and coating processes. For the powder producing process, the solution was aged, dried and sintered sequentially. Then, Ta2O5 powders were obtained. For the coating process, the solution was applied to the AZ91 Mg alloy samples’ surfaces using a dip coater. Coated samples were dried and sintered. The morphologies of the samples were investigated by using scanning electron microscope with energy-dispersive spectroscopy (SEM–EDS, Jeol JSM 6060 LV) and X-ray diffraction (XRD, Bruker D8 Advance). The dried Ta2O5 powders were analyzed using combined thermogravimetry–differential thermal analysis (TG–DTA, Hitachi STA 7300). The coating ability of the tantalum oxide layer on the AZ91 Mg alloy surface has been discussed. The results demonstrate that an optimum amount of deflocculating chemicals must be added to the coating in order to optimize the surface morphology. Graphic Abstract: [Figure not available: see fulltext.]. © 2020, The Indian Institute of Metals - IIM.Item Characterization of SiO2 Sol-Gel Coated Ti6Al4V Alloy Obtained by using TEOS and GPTMS(International Institute for the Science of Sintering (IISS), 2021) Gül C.; Albayrak S.; Durmuş H.; Çömez N.Synthesis of silicon oxide (SiO2) via the sol-gel method and SiO2 coating ability on to Ti6Al4V alloy were investigated, in the novel study. Ti6Al4V alloy is the most used alloy in biomedical applications due to its many advantages. However, it has a minor disadvantage like releasing ions into the human body. In this study, the substrate material Ti6Al4V alloy samples were coated using the sol-gel method with alkoxysilane solutions (tetraethyl orthosilicate, TEOS; Si(OC2H5)4 and glycidoxypropyltrimethoxysilane, GPTMS; C9H20O5Si) containing the unit of prepared Si(OR)n after the surface preparations were made. The prepared solutions were examined using thermal analysis methods and the process temperatures to be applied to the coatings were determined according to the results of the analysis. Coated samples were subjected to aging, drying, and sintering processes at specified temperatures. The morphologies and structures of the samples were investigated by using a scanning electron microscope with energy-dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The sol-gel coating ability of the silicon oxide on the surface of the Ti6Al4V alloys has been discussed. The results demonstrate that cracks were observed in coating produced by TEOS precursor whereas the coatings used GPTMS precursor exhibited crack-free surface independently of dipping number. The crack formation tended to reduce with increasing dipping number of coatings produced by TEOS precursor. Distances between coating islets gradually became smaller as the number of dippings increased, and the continuity of the coatings increased. It has been observed that SiO2 coating layers produced with GPTMS are obtained in a more continuous and crack-free form than the layers produced with TEOS. © 2021 Authors. Published by association for ETRAN Society.Item Improvement in Corrosion Resistance of Tantalum Oxide and Tantalum Oxide with Diethanolamine Sol–Gel Coated Magnesium Alloys(Pleiades Publishing, 2022) Gül C.; Albayrak S.; Çinici H.; Aytaç A.Abstract: In this study, corrosion resistance was developed to ensure that AZ91 Mg alloy remains stable in the body for longer periods. For this purpose, tantalum oxide and tantalum oxide with diethanolamine coatings were made by sol–gel method on AZ91 magnesium alloy surfaces. The structural analyses of tantalum oxide and tantalum oxide with diethanolamine obtained by sol–gel method were carried out. By using the dip coating method, coatings with different concentrations of solutions and different dipping numbers were applied on AZ91 Mg alloy surfaces. Thus, the effects of dipping numbers and chemical content of the solution on the coating thicknesses, surface roughnesses, morphologies and corrosion resistances of coating layers were examined. As a result, it was determined that the coating thicknesses increased with the dipping number. The low number of dipping could not provide sufficient protective layer formation on the surface. Better results were obtained in samples with a high dipping numbers. It was observed that needle-like structures were formed in the solution using diethanolamine. As the amount of diethanolamine increased, a more homogeneous and dense coating layer was observed. Accordingly, an increase in corrosion resistance has been observed. It was determined that the corrosion rate of AZ91 Mg alloy has decreased by 86% with increasing dipping number and diethanolamine amount. © 2022, Pleiades Publishing, Ltd.Item Mechanical Properties of Al2024/Al2O3/MgO/Graphite composites via hydro-thermal hot pressing route(Elsevier Ltd, 2023) Ovalı İ.; Esen C.; Albayrak S.; Karakoç H.; Saravana Kumar M.; Yang C.-H.Currently, the research community is focused on hybrid composites with two different reinforcements. However, it's difficult to attain both mechanical strength and wear resistance simultaneously. So, the prime novelty of this research work is to enhance both the mechanical strength and wear performance of the composites by adding three reinforcement particles effectively through the hydro-thermal hot pressing technique. In this research, Al2024 alloy was reinforced with Al2O3–MgO-Gr particles in five different reinforcement combinations. With the help of a 3D mixer, the reinforcements were mixed in determined ratios for 30 min. The mixed powders were cold pressed under 50 MPa pressure, and then hot pressed at 550 °C under 200 MPa pressure. The fabricated hybrid composite materials were evaluated for their density and porosity. Further, hardness, transverse rupture strength and wear performance were investigated. The predominant wear mechanism was examined by wear mechanism maps under various sliding and normal conditions. The outcome shows that the inclusion of excess (>3%) nano MgO and (>1.5%) Gr particles decrease the density of the composite materials by forming micropores. The optimum reinforcement combination of 10% Al2O3, 3% of MgO and 1.5% of Gr particles shows improved cross-fracture strength of 132.6 MPa, minimum volume loss of 0.55 mm3 and decreased frictional coefficient of 0.18. Further, the smoothness in the worn-out surface SEM images of the composites substantiates the enhanced wear performance. © 2023 Elsevier B.V.Item A Retrospective Analysis of 83 Patients with Testicular Mass Who Underwent Testis-Sparing Surgery: The Eurasian Uro-oncology Association Multicenter Study(S. Karger AG, 2023) Keske M.; Canda A.E.; Karadag M.A.; Çiftçi H.; Erturhan S.; Kactan C.; Soytas M.; Özkaya F.; Ozbey I.; Ordek E.; Atmaca A.F.; Yildirim A.; Sahin S.; Colakoglu Y.; Boylu U.; Erol B.; Caskurlu T.; Kiremit M.C.; Cakici O.U.; Sonmez G.; Klllçarslan H.; Akbulut Z.; Kayglslz O.; Bedir S.; Vuruskan H.; Bozkurt Y.E.; Aydin H.R.; Oguz U.; Basok E.K.; Gumus B.H.; Tuncel A.; Aslan Y.; Hamidi N.; Müslümanoǧlu A.Y.; Dinçer M.; Balbay D.; Albayrak S.; Laguna M.P.Introduction: Herein, we analyzed the histopathological, oncological and functional outcomes of testis-sparing surgery (TSS) in patients with distinct risk for testicular cancer. Methods: This is a multicenter retrospective study on consecutive patients who underwent TSS. Patients were categorized in high- or low-risk testicular germ cell tumor (TGCT) according to the presence/absence of features compatible with testicular dysgenesis syndrome. Histology was categorized per size and risk groups. Results: TSS was performed in 83 patients (86 tumors) of them, 27 in the high-risk group. Fifty-nine patients had a non-tumoral contralateral testis present. Sixty masses and 26 masses were benign and TGCTs, respectively. No statistical differences were observed in mean age (30.9 ± 10.32 years), pathological tumor size (14.67 ± 6.7 mm) between risk groups or between benign and malignant tumors (p = 0.608). When categorized per risk groups, 22 (73.3%) and 4 (7.1%) of the TSS specimens were malignant in the high- and low-risk patient groups, respectively. Univariate analysis showed that the only independent variable significantly related to malignant outcome was previous history of TGCT. During a mean follow-up of 25.5 ± 22.7 months, no patient developed systemic disease. Local recurrence was detected in 5 patients and received radical orchiectomy. Postoperative testosterone levels remained normal in 88% of those patients with normal preoperative level. No erectile dysfunction was reported in patients with benign lesions. Conclusion: TSS is a safe and feasible approach with adequate cancer control, and preservation of sexual function is possible in 2/3 of patients harboring malignancy. Incidence of TGCT varies extremely between patients at high and low risk for TGCT requiring a careful consideration and counseling. © 2023 S. Karger AG, Basel.Item Tribological Characteristics of Tantalum-Oxide Coating Fabricated on Pre-Treated 2024 Aluminum Alloys(American Society of Mechanical Engineers (ASME), 2023) Albayrak S.; Gul C.; Ci̧nici H.; Şahin Ö.Aluminum has many advantages, such as being lightweight, but it may not provide sufficient wear resistance for some applications. Tantalum oxide is a ceramic-based coating layer that can improve wear resistance. In this study, 2024 aluminum alloy samples with different surface treatments were coated with amorphous Ta2O5 using the RF spraying method under the same conditions. Polishing, 10% HCl solution, 5% NaOH solution, and 50% HNO3 solution, as well as sandblasting, were applied to the surfaces of aluminum alloys separately, and the sample groups were coated. The effects of pre-coating surface treatments on coating morphology and wear resistance were investigated. The surface morphologies of the coatings were examined using scanning electron microscopy, electron dispersion spectroscopy, and X-ray diffraction. Wear tests were then conducted to determine the mechanical properties, and after the tests, scanning electron microscopy examinations and volume loss calculations were performed using a profilometer. The wear test results were discussed and compared. The investigation yielded continuous, homogeneous, and crack-free coatings on the 2024 aluminum alloy surfaces. However, the wear resistance of these coatings was compromised by acid etching. Following polishing and sandblasting, the coated surfaces experienced a decrease in volume losses from abrasion by 4.3% and 44.8%, respectively, compared to the uncoated samples. Copyright © 2023 by ASME.Item Electrochemical, mechanical, and antibacterial properties of the AZ91 Mg alloy by hybrid and layered hydroxyapatite and tantalum oxide sol-gel coating(Walter de Gruyter GmbH, 2023) Albayrak S.; Gül C.; Emin N.; Gökmen U.; Karakoç H.; Uzun A.; Çinici H.The corrosion and bacterial behavior of AZ91 magnesium alloy coated with sol-gel-deposited amorphous tantalum oxide and hydroxyapatite have been investigated. The objective was to assess the potential suitability of AZ91 for permanent prosthesis applications. The coatings were applied in layered and hybrid configurations and characterized using various techniques including X-ray diffractometry, Fourier transform infrared spectroscopy, scanning electron microscopy/energy dispersive spectrometry, and drop analyses. The antibacterial properties were evaluated through interactions with Staphylococcus aureus and Escherichia coli strains. Mechanical properties and adhesion were determined via linear scratch tests, and electrochemical corrosion tests were conducted in different media. The release of aluminum ions from the samples in Dulbecco's Modified Eagle's Medium was monitored over 28 days. The findings revealed that the amorphous tantalum oxide coating, particularly in combination with hydroxyapatite, improved antibacterial properties and positively influenced corrosion and scratch resistance. The layered and hybrid coatings demonstrated the highest corrosion resistance. The release of aluminum ions remained within acceptable levels in the tested medium. Overall, the study provides valuable insights into the potential of sol-gel coatings on AZ91 for prosthetic applications, considering antibacterial behavior, corrosion resistance, and aluminum release. © 2023 Walter de Gruyter GmbH, Berlin/Boston.Item The effects of alkali, alkali-acid and sandblasting surface treatments applied before Tantalum-Oxide coating with magnetron sputtering on the wear behavior of 7075 Aluminum alloys; [Magnetron sıçratma ile Tantal-Oksit kaplama öncesi uygulanan alkali, alkali-asit ve kumlama yüzey işlemlerinin 7075 Alüminyum alaşımlarının aşınma davranışlarına etkileri](Gazi Universitesi, 2023) Gül C.; Albayrak S.; Çinici H.; Algan Şimşek İ.B.Aluminum alloys are alloys that are widely used in many sectors due to their high specific strength and are constantly being developed to adapt to today's developing technology. Among these alloy groups, the use of 2XXX and 7XXX series alloys, which are alloy groups that can be hardened by precipitation hardening, is even more common. In this study, an amorphous tantalum-oxide layer was coated by magnetron sputtering method in order to improve the wear resistance of 7075 aluminum alloys. It was applied to the sample groups after polished, sandblasted, alkali, and alkali acid treatments, and the effect of the surface treatments applied before coating on the wear performances after coating was investigated. The effect on the surface morphologies after coating was investigated using scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS), and their structural analysis was investigated by the X-ray diffraction (XRD) method. The wear behavior of the samples was determined by the ball-on disc wear test performed at room temperature under dry sliding conditions and by SEM examinations, wear track profile measurements, average volume loss calculations and friction coefficient evaluations performed after wear. After the coating process, Ta2O5 coating was obtained in an amorphous structure without cracks, voids, and heterogeneity. Coating thicknesses were measured as ≅2.5-5µm. The highest wear resistance among all samples was observed in the samples coated after alkali and alkali acid treatments, and it was observed that the volume losses after wear decreased by 69-77% compared to the polished and untreated sample. © 2023 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.Item Elastomeric nanocoatings(Elsevier, 2023) Gül C.; Albayrak S.Elastomers and elastomeric nanocoatings have become used in many applications, from reflective coatings to wearable technology applications, superhydrophobic surfaces, self-cleaning, and even self-healing surfaces in today's developing technology applications. Recent research in nanocoatings and nanomaterials lead the fabrication of elastomeric nanomaterials and elastomeric nanocoatings. The unique properties of these coatings attract the incredible attention of researchers. Materials to be used after being coated with nanocoatings, which can be encountered in different areas, have been developed more recently and have gained an important place in our lives. In this section, information about elastomeric nanocoating structures, physical and mechanical properties of these structures, classifications, and usage areas are given. The production of the elastomers used, and a large part of the processes applied afterwards, vary according to the place of use, and these differences are also mentioned in this section. Surface structures, properties of surfaces obtained with nanocoating, chemical differences, multifunctional coatings are also included in this section. © 2023 Elsevier Inc. All rights reserved.Item Contact angle studies of nanoscale polymer based coatings(Elsevier, 2023) Albayrak S.; Gül C.The contact angle and surface/interface energies are a measure of the wetting ability of liquids. This criterion is evaluated especially when developing a material to modify it to what we want the surface to have. In this section, general information about contact angle measurements and techniques used for these evaluation and development methods are given. © 2023 Elsevier Inc. All rights reserved.Item Wear and corrosion resistance of zinc-oxide and zirconium-oxide coated WE43 magnesium alloy(AVS Science and Technology Society, 2023) Gül C.; Durmuş H.; Albayrak S.; Çömez N.Magnesium alloy, which draws attention with its lightness and high specific strength, is frequently preferred due to its advantages. However, it is necessary to improve the wear and corrosion properties in order to develop the areas of use in the automotive, aircraft, and space industries. For this purpose, after the surface preparation of the main material WE43 Mg alloy, ZnO and ZrO2 coatings were made and characterized in this study. The surface morphology and structural and chemical properties of the samples were investigated using profilometry, contact angle tests, scanning electron microscopy, and x-ray diffraction. Corrosion tests have been carried out. In order to determine the wear performance of the samples, the wear-related volume losses were measured and the friction coefficients were compared. Layers with 2-6 μm coating thickness were obtained homogeneously on the polished and sandblasted sample surfaces. It was determined that the coating layers grew in the form of columns and did not contain capillary cracks. As a result of the study, it was observed that the ZnO-coated samples had the highest wear and corrosion resistance, and the wear and corrosion resistance of the coatings and magnesium alloy substrates improved. © 2023 Author(s).Item Clinical and Demographic Characteristics of Treatment Requiring Retinopathy of Prematurity in Big Premature Infants in Turkiye: Report No. 1 (BIG-ROP Study)(S. Karger AG, 2024) Özdek Å.; Ozdemir H.B.; Ozen Tunay Z.; Bayramoglu S.E.; Alyamac Sukgen E.; Klr N.; Koç E.; Ekinci D.Y.; Sayin N.; Ceylan N.A.; Cebeci Z.; Çelik G.; Kizilay O.; Demir S.T.; Yildiz M.; Öztürk T.; Bekmez S.; Eris E.; Çömez A.; Mayali H.; Kabatas E.U.; Satirtav G.; Ögreden T.; Vural A.; Onur I.U.; Yeter D.Y.; Gönc T.; Tanidir S.T.; Akdogan M.; Çelemler P.; Beyazyildiz E.; Beyazyildiz Ö.; Acar D.E.; Özbay E.K.; Özcan Y.; Keles S.; Yildirim M.; Uzun A.; Dikci S.; Sari A.; Kara C.; Petriçli I.S.; Comba Ö.B.S.; Albayrak S.; Ersan B.A.; Bilgin B.; Çeliker H.; Sahin O.; Seymen Z.; Alaluf A.; Kaymak N.Z.; Oral A.Y.; Kerimoglu H.; Ünsal A.I.A.; Hirfanoglu I.M.; Tayman C.; Mert M.K.; Çetinkaya M.; Karatekin G.; Uslu S.; Özkan H.; Tüzün F.; Yildirim T.G.; Yurttutan S.; Dinlen N.F.; Bezirganoglu H.; Altinhan H.; Salihoglu Ö.; Tun G.; Karakurt D.G.; Bas A.Y.; Demiroglu Ö.B.; Aygün C.; Tekgündüz K.S.; Ceylan M.; Özdemir R.; Zübahiroglu U.; Özkiraz S.; Cömert S.; Akcan A.B.Introduction: The aim of the study was to analyse the clinical and demographic features of infants with gestational age (GA) of 32-37 weeks and birth weight (BW) of >1,500 g who developed treatment requiring retinopathy of prematurity (ROP). Methods: Data on the infants with a GA of 32-37 weeks and BW >1,500 g who developed treatment requiring ROP (TR-ROP) were collected retrospectively from the 33 ROP centres in Turkiye. GA, BW, type of hospital, neonatal intensive care units (NICUs) level, presence of an ophthalmologist and neonatologist in the same hospital, length of stay in NICU, duration of oxygen therapy, comorbidities, type of ROP, and timing for TR-ROP development were analysed. Results: A total of366 infants were included in the study. Mean GA and BW were 33 1 weeks and 1,896 316 g, respectively. Duration of hospitalization was 3-4 weeks in 46.8% of them. The first ROP examination was performed at postnatal 4-5 weeks in 80.3% of infants, which was significantly later in level 2 and lower NICUs and non-university clinics. At the first ROP examination, any stage of ROP was detected in 90.9% and TR-ROP was detected in 15.3% of the infants. The mean postnatal week of TR-ROP development was 6.16 2.04. Conclusion: Routine ROP screening thresholds need to be expanded in hospitals with suboptimal NICU conditions considering the development of TRROP in more mature and heavier preterm infants. The first ROP examination should be earlier than the fourth postnatal week. 2024 S. Karger AG, Basel. © 2024 S. Karger AG. All rights reserved.Item Fe-Cr-C-V hardfacing coatings with molybdenum addition: Wear, corrosion, and cavitation performances(Elsevier B.V., 2024) Çömez N.; Yurddaskal M.; Gül C.; Durmuş H.; Albayrak S.The purpose of this study was to determine how molybdenum content affected the hardfacing coatings made of Fe-Cr-C-V that resist wear, corrosion, and cavitation. The hardfacing process was applied on the S235JR steel by the metal arc welding method. Apart from the chromium-rich M23C6 and M7C3 (M: Cr, Fe) carbides, the presence of molybdenum led to the development of M2C (M: Mo, Fe, Cr) carbides. As molybdenum and carbon concentration decreased, the size and volume fraction of M23C6 and M7C3 carbides tended to reduce. While molybdenum did not significantly alter hardness or wear resistance, it was found to be advantageous in terms of cavitation and corrosion. The coating, including 3 wt% FeMo, demonstrated a 20-fold increase in cavitation resistance compared to the coating devoid of molybdenum. The hardfacing coatings' resistance to corrosion was increased by up to 4.5 times with the addition of molybdenum. © 2024 Elsevier B.V.