Browsing by Author "Kanbur K."

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    Investigation of in vitro behavior of plasma sprayed Ti, TiO2 and HA coatings on PEEK
    (Elsevier B.V., 2021) Sargin F.; Erdogan G.; Kanbur K.; Turk A.
    Orthopedic implants are one of the most reliable and widely used equipments to increase the quality of human life by enhancing or replacing damaged body parts and ensuring the problematic parts of the body to become operative after a short time period. Polyether ether ketone (PEEK) is a semi-crystal high-performance thermoplastic polymeric implant material which emerged as an alternative for metallic implants that used in orthopedic surgery. Although PEEK has some superior properties such as high melting point, superb wear resistance, excellent fatigue behavior, non-toxicity for bone tissue and elasticity modulus similar to human bone, PEEK has some disadvantages such as biologically inert behavior and low bioactivity. In this context, coating the implant surface to improve its osteointegration behavior is widely accepted. Coating PEEK polymers with bioactive materials such as Hydroxyapatite (HA) is among one of the solutions for this problem. In this study, in order to increase surface bioactivity of PEEK biomaterials, Titanium (Ti), Titanium dioxide (TiO2) and Hydroxyapatite (HA) powder combinations was coated on PEEK samples by using Atmospheric Plasma Spray (APS) method. Morphological and chemical characterization showed produced coatings are suitable for implantation process. Also in vitro tests performed in Simulated Body Fluid (SBF) revealed that HA, Ti + HA and TiO2 + HA coatings have bioactive property. © 2021 Elsevier B.V.
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    Characteristics of boronized Ti6Al4V alloy using boric acid based boronizing mixture
    (Elsevier Inc., 2022) Türkmen İ.; Kanbur K.; Sargin F.
    Boronizing processes of Ti alloys are generally performed in atmosphere-controlled furnaces. In this study, it is aimed to carry out boronizing process under atmospheric conditions by using an alternative boronizing mixture containing boric acid and to better the surface characteristics of Ti6Al4V alloy by boronizing. The efficiency of the boronizing mixture was evaluated by performing boronizing at different process temperatures (900-1100 °C) and durations (12 and 20 h). Microstructural (OM, SEM) and chemical (XRD, EDS, XPS) analyzes were performed to characterize the boride layers formed on the surfaces of the boronized samples. As a consequence of these analyzes, it was found out that a two-phase boride layer (TiB2 + TiB) was obtained in the samples. In addition, in vitro tests were done for specifying the bioactivity of boronized samples. In order to determine the effect of boronizing on the corrosion resistance of Ti6Al4V alloy, corrosion tests were performed by the Tafel extrapolation method. The adhesion behavior of the boride layers was determined by the Daimler-Benz Rockwell C indentation test. As a result, boronizing studies have been performed successfully without atmospheric-controlled conditions and it has been defined that surface characteristics of the Ti6Al4V alloy have bettered through the boride layers formed on the alloy surface. © 2022 Elsevier Inc.
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    Investigation of surface-modified EBM printed Ti-6Al-4V alloys for biomedical applications
    (Elsevier B.V., 2022) Demirci S.; Dikici T.; Tünçay M.M.; Dalmış R.; Kaya N.; Kanbur K.; Sargın F.; Güllüoğlu A.N.
    This work aimed to comprehensively assess the influence of various surface modifications on the formation of apatite ability for EBM Ti-6Al-4V alloy. Sandblasting (S), acid-etching (E), sandblasting and acid-etching (SE), anodization (NA), micro-arc oxidations in 1 M H2SO4 solution (SM) and 1 M H3PO4 solution (PM) methods were applied to modify electron beam melted (EBM) Ti-6Al-4V surface. The α/α’-Ti structures and TiO2 phases were detected by XRD. The surface roughness (Ra) values ranged from 0.25 μm and 2.86 μm. The wettability of samples was between around 25° and 104° The SM sample possessed the lowest contact angle. In vitro tests were employed in the simulated body fluid (SBF) solution for 28 days. The samples with different surface textures demonstrated bioactive behaviors. In vitro test results showed that apatite layers formed on the surfaces. The SM sample exhibited good apatite formation ability when the Ca/P ratios were considered. The apatite formation for the SM sample might derive from high roughness, low contact angle value, the existence of Ti-OH groups, and anatase and rutile phases. The SM can be implemented to boost bioactivity on EBM Ti-6Al-4V alloys. © 2022
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    Failure analysis of copper pipes used in the heat exchangers in fan coil units
    (CSIC Consejo Superior de Investigaciones Cientificas, 2023) Sargın F.; Kanbur K.; Türkmen İ.
    Heat exchangers (HE) consist of copper and steel pipes and are used for heating and cooling the ambient air. One of the main problems seen in HE is the leakage on copper pipes. In this study, failed and properly working copper pipe samples used for different durations were examined in detail. The microstructural analyses were performed using optical microscopy (OM) and scanning electron microscopy (SEM) to detect corrosion occurrences on copper pipe surfaces. In addition, corrosion products of the samples were defined by X-Ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and Fourier-Transform Infrared Spectroscopy (FTIR) analyses. The formation of interconnected tunnels in cross section of the failed copper pipe sample that were in microscopic dimensions and corrosion products were observed. Consequently, all the analyses result that were obtained from the samples pointed out a corrosion mechanism known as ant-nest corrosion. It was concluded that the main reason of corrosion was related to ethylene glycol type additives which were used in HE along with mains water. © 2023 CSIC.
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    Comparative study on the thermal and tribological properties of PA12 and PA11 for coating applications
    (John Wiley and Sons Inc, 2024) Başaran S.; Türkmen İ.; Yağcı T.; Kanbur K.; Baştürk S.B.
    In this study, the performance and potential applicability of polyamide-12 (PA12) as an alternative to polyamide-11 (PA11), which is currently used in the coating processes of sliding tools present in cardan shafts, was investigated. The advantages of PA12 powder instead of PA11 in cardan shafts' coating include ease of supply and cost-effectiveness, while still achieving similar performance. Therefore, PA12 is a more economical choice for coating applications. The PA11 and PA12 neat polymers were characterized via differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Based on the analyses, PA12 demonstrated substantial advantages over PA11. It showed a 16°C improvement in decomposition temperature and a 50% increase in crystallinity, enhancing stability under operational conditions, whereas PA11 exhibited approximately 6–7% higher values in crystallization and melting temperatures. The wettability behavior of the steel substrates coated with those polyamides was measured via contact angle analysis. Wear properties and morphologies of coatings were examined using a ball-on disc test and scanning electron microscopy, respectively and comparatively. Furthermore, PA12 typically displays 30% lower wear rates and similar deformation patterns in tests, thereby presenting itself as a cost-effective and widely accessible option for coating applications in comparison to PA11. © 2024 Wiley Periodicals LLC.
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    The Role of Water on the Oxidation Process of Graphene Oxide Structures
    (Sakarya University, 2024) Kanbur K.; Birlik I.; Sargın F.; Funda Ak Azem N.; Türk A.
    Graphene oxide (GO) has recently attracted attention with its unique chemical and physical properties and serves as a raw material for graphene-based materials. GO has been produced for decades by the Hummers Method with the oxidation process of graphite. The properties and structure of GO are significantly affected by the production parameters of Hummers Method. In this study, the effect of the water content on the oxidation level of GO structure was investigated. GO was produced with different amounts of water in the oxidation stage of Hummers Method. The structural characterizations of produced GO were carried out by X-ray Diffraction Technique (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Energy Dispersive X-ray Spectroscopy (EDS), UV-Visible Spectroscopy (UV-Vis) and Raman Spectroscopy. Additionally, morphological and thermal characterization of the produced GO samples were performed by Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA)/Differential Thermal Analysis (DTA), respectively. According to XRD, FTIR, XPS, and EDS results, it was determined that the oxidation degree of GO decreased with increasing amount of water. Besides, it was revealed that the post-oxidation step generated more defects in the basal plane of graphene according to the results of the Raman Analysis. Also, it was observed that GO had a smoother surface and was found to have higher thermal stability with increasing amounts of water. The results show that the post-oxidation step reduces the oxidation degree of GO, increases the amount of the defect, provides a less wrinkled structure, and improves the thermal stability of GO. © 2024, Sakarya University. All rights reserved.