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Öğe A study on the phase transformation behaviour of Cu-20wt.Sn alloy produced using powder metallurgy method: Experimental and molecular dynamics modelling(Elsevier B.V., 2020) Özel, Serkan; Çelik, Fatih Ahmet; Kaya, MehmetIn this study, Cu-20wt.Sn alloy was produced by powder metallurgy (PM) method by using high purity element powders. The phases in the microstructure of the produced alloy were determined by XRD study. The phase transformation behaviour of the alloy was investigated by DSC and modelling method. Moreover, the Cu-20wt.Sn alloy system was modelled with molecular dynamics (MD) simulation based on modified Embedded Atom Method (MEAM). The radial distribution function (RDF) was calculated to determine the structural properties of system during the phase transformations. The experimental results showed that the transformation (?+?) ? (?+?) occur at temperature above 500°C. The simulation results showed that the phase transformation ?+???+? occurs at 550°C temperature. Our simulation results are in reasonable agreement with the experimental data. © 2020 Elsevier B.V.Öğe Assessing Microstructural, Biomechanical, and Biocompatible Properties of TiNb Alloys for Potential Use as Load-Bearing Implants(Mdpi, 2024) Karakurt, Eyyup Murat; Huang, Yan; Cetin, Yuksel; Incesu, Alper; Demirtas, Huseyin; Kaya, Mehmet; Yildizhan, YaseminTitanium-Niobium (TiNb) alloys are commonly employed in a number of implantable devices, yet concerns exist regarding their use in implantology owing to the biomechanical mismatch between the implant and the host tissue. Therefore, to balance the mechanical performance of the load-bearing implant with bone, TiNb alloys with differing porosities were fabricated by powder metallurgy combined with spacer material. Microstructures and phase constituents were characterized with energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The mechanical properties were tested by uniaxial compression, and the corrosion performance was determined via a potentiodynamic polarization experiment. To evaluate a highly matched potential implant with the host, biocompatibilities such as cell viability and proliferation rate, fibronectin adsorption, plasmid-DNA interaction, and an SEM micrograph showing the cell morphology were examined in detail. The results showed that the alloys displayed open and closed pores with a uniform pore size and distribution, which allowed for cell adherence and other cellular activities. The alloys with low porosity displayed compressive strength between 618 MPa and 1295 MPa, while the alloys with high porosity showed significantly lower strength, ranging from 48 MPa to 331 MPa. The biological evaluation of the alloys demonstrated good cell attachment and proliferation rates.Öğe Effect of Relative Density on Microstructure, Corrosion Resistance and Mechanical Performance of Porous Ti–20Zr Alloys Fabricated by Powder Metallurgy(Institute for Ionics, 2024) Karakurt, Eyyup Murat; Huang, Yan; Kaya, Mehmet; Demirtas, Hüseyin; Acikgoz, Abuzer; Demircan, GokhanThe microstructure, corrosion resistance and mechanical properties of a binary Ti–20Zr (at. %) alloy with differing porosities were investigated. The alloys were produced following a standard powder metallurgy with sintering at 1200 °C for 4, 6, and 8 h. A space holder agent was used to obtain two ranges of relative density, i.e., 74.8–89.3% and 54.6–66.7%. Metallographic examinations were conducted by using optical microscopy and scanning electron microscopy. The confirmation of chemical composition was performed by energy dispersive spectrometry and elemental mapping analysis. Electron backscatter diffraction analysis was conducted to investigate microstructure morphology. Phase identifications were detected by X-ray diffraction. Uniaxial compressive tests were carried out and also potentiodynamic polarization was employed to understand the corrosion performances of the alloys. Experimental results showed that the pore size and pore connectivity were able to be controlled by the sintering time and a fixed amount of space holder agent. The phase constituents of the alloys were characterized as a mixture of predominant hcp ? phase and some distorted hcp ?? phase. As foreseen, the ultimate compressive strength and elastic modulus of the alloys increased with increasing relative density. Results of corrosion resistance revealed adding space holder reduced the polarization resistance of Ti–20Zr (at. %) sintered for 6 h from 15.4 to 14.09 ?. However, volume fraction of general porosity did not affect the microstructure of the alloys. In conclusion, the relative density of the alloys achieved in this study played a crucial role on the mechanical properties and corrosion properties. © King Fahd University of Petroleum & Minerals 2023.Öğe Effect of sintering procedure on microstructure and mechanical properties of biomedical TiNbSn alloy produced via powder metallurgy(Springer Science and Business Media Deutschland GmbH, 2021) Çakmak, Ömer; Kaya, MehmetNew Ti-based alloys have recently attracted great attention in biomedical implementations due to their high strength, good biocompatibility, shape memory feature, low density and corrosion resistance. In this study, Ti-16 at% Nb-4 at% Sn alloy was produced by powder metallurgy for use as a biomaterial. In addition, the effects of sintering temperature and sintering time on the microstructure and mechanical properties of the alloy were investigated. The results indicated that ? phase was dominate and ? phase was seen as secondly phase in the microstructures of the sintered samples. As sintering temperature and sintering time increase, the porosity decreases, and compressive strength raised depending on decreasing porosity. Elastic modules of samples produced via powder metallurgy (PM) are close to that of natural bone; hence, the samples do not cause bone abrasion when combined with bone. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.Öğe Effect of Zr Concentration on the Microstructure and Mechanical Performance of Porous Ti-Zr System by Powder Metallurgy(Trans Tech Publications Ltd, 2022) Karakurt, E.M.; Huang, Y.; Kaya, Mehmet; Demirtaş, H.; Çakmak, O.In this study, porous binary Ti-(x)Zr alloys of nominal Zr contents (x=10, 20 and 30 at. %) with differing porosities were manufactured, using powder metallurgy with compaction conducted under a pressure of 300MPa and sintering at 1200 ?C for 6 h. A space holder agent was employed to control the general porosity. The microstructures were characterized by scanning electron microscopy and energy dispersed spectroscopy. The phase constitution was done by X-ray diffractometer. Uniaxial compressive tests were performed to determine the mechanical behaviours. Microstructural studies revealed macro/micro pores generated were mostly irregularly shaped with a uniform pore size distribution in all Ti-(x)Zr (at. %) alloys. The finer microstructure was obtained with increasing Zr contents. The mechanical performances of the porous Ti-(x)Zr (at. %) binary systems were strongly influenced by Zr and general porosity. © 2022 Trans Tech Publications Ltd, Switzerland.Öğe Fabrication, characterization, and in vivo biocompatibility evaluation of titanium-niobium implants(SAGE Publications Ltd, 2021) Yolun, Abdurrahman; Şimşek, Murat; Kaya, Mehmet; Elibol Annaç, Ebru; Köm, Mustafa; Çakmak, ÖmerIn this study, biocompatible titanium-niobium (Ti-Nb) alloys were fabricated by using powder metallurgy methods. Physical, morphological, thermal, and mechanical analyses were performed and their in vivo compatibility was evaluated. Besides ?, ?, and ?? martensitic phases, ?+? Widmanstätten phase due to increasing sintering temperature was seen in the microstructure of the alloys. Phase transformation temperatures of the samples decreased as Nb content increased. The ratio of Nb in the samples affected their mechanical properties. No toxic effect was observed on implanted sites. This study shows that Ti-Nb alloys can be potentially used for orthopedic applications without any toxic effects. © IMechE 2020.Öğe İmplantasyon Uygulamaları İçin Toz Metalurjisi ile Üretilen Ti-16Nb-4Sn Alaşımının Mikroyapı ve Biyouyumluluk Özelliklerinin İncelenmesi(2022) Annaç, Ebru; Köm, Mustafa; Çakmak, Ömer; Kaya, MehmetBu çalışmada, Ti-16Nb-4Sn alaşımları az gözenekli ve çok gözenekli olarak geleneksel toz metalürjisi yöntemi ile üretildi. Sinterlenen numunelerin faz analizleri ve mikroyapılarında meydana gelen değişimler; XRD, optik mikroskop, SEM-EDS teknikleri kullanılarak incelendi. XRD analiz sonuçlarında yapının ? ve ? fazlarından oluştuğu tespit edildi. SEM-EDS incelemeleri sonucunda yapının, ? fazın ait koyu gri ve ? fazına ait açık gri olmak üzere iki tür morfolojiden oluştuğu tespit edildi. Gözenek oranı azaldıkça daha homojen bir yapının oluştuğu görüldü. Numunelerin gözenek oranının artması ile basma dayanımlarının azaldığı görülmektedir. Çok gözenekli numunelerin in vivo ortamda biyouyumluluk özellikleri incelendiğinde implantasyon bölgesinde toksik ve alerjik etkileşimin olmadığı görülmekte ve böylece numunelerin biyouyumluluk açısında ideal bir implant malzemesi olarak kullanılabileceği öngörülmektedir.Öğe Investigation of structural and optical properties of pure ZnO and co-doped ZnO:Al:Mnx (x=1%, 2%, 3%, 5% at.) semiconductor thin films and electrical properties of produced diodes(Gazi Universitesi, 2023) Demirbilek, N.; Kaya, Mehmet; Yakuphanoğlu, FahrettinIn this work, undoped and co-doped ZnO:Al:Mn semiconductor thin films and p-type Si diodes were produced via sol-gel technique method. The morphological and optical properties of the produced thin films were investigated using SEM, XRD and UV-Spectrophotometer, respectively. It was observed that the crystal structure of the semiconductor samples had a hexagonal wurtzite structure and the forbidden energy gaps of the samples decreased with increasing Mn contribution. The experimental zero-feed current barrier height (?b(I-V)), rectification ratio, ideality factor and Ion/Ioff parameters of the diodes were determined via the thermionic emission model. It was determined that the produced Al/p-Si/ZnO:Al:Mn/Al diode had high rectification ratio and Ion/Ioff values of 1.56x105 and 1.54x104, respectively, and exhibited light-sensitive behaviour. Also, the capacitance barrier height (?b(C-V)), built-in voltage (Vbi), diffusion potential (Vd), donor concentration (Nd) and depletion layer width (Wd) values of Al/p-Si/ZnO:Al:Mn/Al diode were calculated via the C-2-V graph drawn under 1MHz frequency. The results show that the fabricated diodes can be used as photodiodes or photosensors in optoelectronic applications. © 2023 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.Öğe Microstructural, Biomechanical, and In Vitro Studies of Ti-Nb-Zr Alloys Fabricated by Powder Metallurgy(Mdpi, 2023) Karakurt, Eyyup Murat; Cetin, Yuksel; Incesu, Alper; Demirtas, Huseyin; Kaya, Mehmet; Yildizhan, Yasemin; Tosun, MerveThis study investigated the microstructures, mechanical performances, corrosion resistances, and in vitro studies of porous Ti-xNb-10Zr (x: 10 and 20; at. %) alloys. The alloys were fabricated by powder metallurgy with two categories of porosities, i.e., 21-25% and 50-56%, respectively. The space holder technique was employed to generate the high porosities. Microstructural analysis was performed by using various methods including scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, and x-ray diffraction. Corrosion resistance was assessed via electrochemical polarisation tests, while mechanical behavior was determined by uniaxial compressive tests. In vitro studies, such as cell viability and proliferation, adhesion potential, and genotoxicity, were examined by performing an MTT assay, fibronectin adsorption, and plasmid-DNA interaction assay. Experimental results showed that the alloys had a dual-phase microstructure composed of finely dispersed acicular hcp & alpha;-Ti needles in the bcc & beta;-Ti matrix. The ultimate compressive strength ranged from 1019 MPa to 767 MPa for alloys with 21-25% porosities and from 173 MPa to 78 MPa for alloys with 50-56% porosities. Noted that adding a space holder agent played a more critical role in the mechanical behaviors of the alloys compared to adding niobium. The pores were largely open and exhibited irregular shapes, with uniform size distribution, allowing for cell ingrowth. Histological analysis showed that the alloys studied met the biocompatibility criteria required for orthopaedic biomaterial use.Öğe Microstructure characterization and biocompatibility behaviour of TiNbZr alloy fabricated by powder metallurgy(Institute of Physics Publishing, 2019) Kaya, Mehmet; Yakuphanoğlu, F.; Elibol, E.; Köm, MustafaThe purpose of this study is to produce Ti-10Nb-10Zr orthopaedic implant material by adding non-toxic niobium (Nb) and zirconium (Zr) elemental powders into titanium (Ti) powder. In addition, to compare the microstructure, corrosion and biocompatibility properties of the orthopaedic implant produced with those of porous pure Ti produced similarly. Ti-at%10Nb-at%10Zr and pure Ti materials were produced with traditional sintering by using raw metal powders. The microstructures of the materials were investigated with SEM and XRD studies, corrosion properties using electrochemical corrosion test and biocompatibility behaviours in vivo using rats were examined. Commercially pure titanium (cpTi) has ? phase at room temperature and causes stress shielding, which results in bone loss when used as an orthopaedic implant. ? phase structure in the microstructure of the alloy is formed by the addition of Nb into Ti, and it is hoped that this structure will better adapt to the bone structure. Because the ? structure is more flexible than pure titanium with ? phase. In addition, the increase of the corrosion resistance of the alloy formed with addition of Nb and Zr indicates that the alloy will remain long lasting biocompatible within the body. © 2019 IOP Publishing Ltd.Öğe Structural and optical properties of pure ZnO and Al/Cu co-doped ZnO semiconductor thin films and electrical characterization of photodiodes(Walter De Gruyter Gmbh, 2021) Demirbilek, Nihat; Yakuphanoğlu, Fahrettin; Kaya, MehmetNano-structured semiconductor thin films and p-type Si photodiodes were fabricated with the sol-gel spin coating technique using pure ZnO and co-doped. ZnO:Al-x:Cu-y with x = 1 at.-%, y = 1, 2, 3, 5 at.-%. The structural and optical properties of thin films were examined using an XRD and a UV-spectrophotometer. The thin films have a hexagonal wurtzite crystal structure, and their optical band gap energies decrease with increasing Cu contribution. The electrical properties of photodiodes were assessed via I-V, C-V, (G/co)-V and phototransient current (14, C-t) measurements. The Phi(b(I-V)), experimental zero-bias barrier height, rectification ratio, ideality factor and I-on/I-off parameters of the diodes were calculated using thermoionic emission model. In addition, Phi(b(C-V)), barrier height, V-bi, built:-in voltage, V-d, diffusion potential, N-d, donor concentration and W-d, depletion layer width of p-SignO:Al-x:Cu-y (x = 1 at.-%, y = 1 at.-%.) photodiodes were obtained using a C-2-V graph plotted at 1 MHz frequency. The photodiodes exhibit rectifying and photosensitive behaviors, and their reverse bias current increases with increasing light intensity. These results indicate that produced diodes can be employed as photodiodes or photosensors in optoelectronic circuits and electronic devices.Öğe The Optical and Structural Properties of Undoped ZnO and Co-doped ZnO:Alx:Cdy x = 1 at %, y = 1, 2, 3, 5 at % Thin Films, and Their Electrical Characteristics as Photodiode(Pleiades journals, 2021) Demirbilek, Nihat; Yakuphanoğlu, Fahrettin; Kaya, MehmetAbstract: ZnO semiconductor thin films with and without Al/Cd additives were produced with sol–gel spin coating technique. Also, photodiodes with and without Al/Cd additives were prepared using the same method. The structural properties of thin films produced were examined with SEM and XRD. Optical properties were tested using UV spectrophotometer, and band gap energies of the films were analyzed using absorbance values obtained. It was observed that the films had hexagonal wurtzite crystal structure, and their band gap energies reduce with increasing amount of Cd added. The electrical characterizations of photodiodes were analyzed with phototransient current (I-t, C-t), current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/w-V) measurements. The barrier height and ideality factor parameters of the diodes were calculated using thermoionic emission model. The photodiodes exhibited photosensitive behavior, and it was seen that reverse bias current raised due to raising the light intensity. The results demonstrated that the produced diodes can be used as photodiodes or photosensors in optoelectronic implementation. © 2021, Pleiades Publishing, Ltd.Öğe Toz Metalurjisi ile Üretilen Gözenekli TiZr Alaşımının Mekanik Özellikleri ve Biyouyumluluğu Üzerine Sinterleme Sıcaklığının Etkileri(2022) Kaya, Mehmet; Annaç, Ebru; Köm, Mustafa; Çakmak, Ömer; Akkuş, AbdurrahmanDünya nüfusunun ortalama yaşam süresi arttıkça implant biyomalzemelerine olan ihtiyaç da artmaktadır. Bu nedenle, bu alandaki araştırmalar son yıllarda artış göstermiştir. Özellikle, gözenekli metaller, ayarlanabilir mekanik ve fiziksel özellikleri ve gözenekli yapısından dolayı implant kemik etkileşimini arttırmasından dolayı daha kullanışlıdır.Bir yenilik olarak, bu çalışmada, sinterleme sıcaklığının Ti-20Zr alaşımlarının mikroyapısı, mekanik ve biyouyumluluk özellikleri üzerindeki etkileri araştırılmıştır.Numunelerin mikroyapılarında meydana gelen değişimler ve faz analizi, taramalı elektron mikroskobu (SEM) ve X-ışını kırınımı (XRD) ile araştırılmıştır.Basma testi kullanılarak numunelerin mekanik özellikleri ve Sprague Dawley dişi ratlar kullanılarak in vivo biyouyumluluk özellikleri incelenmiştir. Deneysel sonuçlara göre, sinterleme sıcaklığı mikroyapı, mekanik özellikler ve biyouyumluluk üzerinde önemli bir rol oynamıştır. Ayrıca implantasyon bölgesinde herhangi bir toksik veya alerjik reaksiyon görülmemiştir. Bu sonuçlar Ti-20Zr alaşımlarının sert doku için umut verici bir implant olduğunu ortaya çıkarmıştır.
