Yazar "Koc, Erkan" seçeneğine göre listele
Listeleniyor 1 - 17 / 17
Sayfa Başına Sonuç
Sıralama seçenekleri
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 Characterization and in vitro bioactivity analysis of apatite growth on modified calcium borate silicate ceramic(Elsevier Sci Ltd, 2023) Saud, A. Najah; Koc, Erkan; Ozdemir, OlcayBioactive glasses are considered biocompatible materials that form a hydroxyapatite-like layer on the surface that allows strong adhesion to soft and hard tissues. This study aims to develop a method to fabricate a borate silicate ceramic biomaterial with a chemical composition of Ca11Si4B2O22 using sodium metaborate (NaBO2) as a flux. X-ray diffraction (XRD), scanning electron microscopy energy distribution spectrometer (SEM-EDS), and Fourier transform infrared spectrometer (FTIR) were used to analyze the structure, surface composition and chemical bonding of the bioactive borate silicate. In addition, the pH measurements and biodegradability behavior of the fabricated glass structures were investigated after immersion in simulated body fluid for 2, 7, 14, and 21 days, respectively. The results showed that the glass-ceramic structure, which was transferred from the crystalline phase Ca11Si4B2O22 to a hydroxyapatite phase after incubation, started on the second day. In addition, the formed hydroxyapatite crystals developed due to the prolonged immersion time, reflecting biodegradable behavior. The antimicrobial activity of the prepared ceramic showed high inhibitory activity against Enterococcus faecalis and Streptococcus mutans.Öğe Comparative Study on Dry and Bio-Corrosive Wear Behavior of Mg-xAl-3Zn Alloys (x=0.5-1-2-3 wt.%)(Springer, 2022) Koc, Erkan; Incesu, Alper; Saud, Amir N.In this study, Mg-xAl-3Zn alloys (x=0.5-1-2-3 wt.%) were produced by the permanent mold casting method. Microstructural characterization of alloys was done with the help of optical microscope (OM) and scanning electron microscope with energy-dispersive spectroscopy (SEM/EDS). Dry and bio-corrosive wear behaviors of alloys were investigated comparatively. Depending on the amount of Al in the alloys, the intermetallic phases were differentiated. Mg17Al12 phase was only observed in Mg-3Al-3Zn alloy distributed along the grain boundary as a continuous or semicontinuous network. The Mg-3Al-3Zn alloy hardness value was about 61.60 +/- 4.23 HV and approximately 30% higher than the other alloys. Dry wear and bio-corrosive (in simulated body fluid (SBF)) wear performances of the alloys were also compared. The abrasive wear mechanism was evident in dry ambient wear due to the intermetallic phases in the structure. Still, the liquid's lubrication effect is much more dominant in the bio-corrosive wear tests carried out in SBF. While Mg-3Al-3Zn wear rate was the lowest in dry wear, it was determined to be the highest in bio-corrosive wear for all applied load conditions. It had been understood that a large amount of Mg17Al12 phase in the structure caused such a result.Öğe Current Bio-based Cements and Radioactive Opacifiers in Endodontic Approaches: A Review of the Materials Used in Clinical Practice(Pera Yayincilik Hizmetleri, 2023) Saud, A. Najah; Koc, Erkan; Ozdemir, OlcayObjective: This study aims to evaluate the importance of endodontic root canal sealers in filling cavities and irregularities in root canals with the primary goal of minimizing or eliminating bacterial residues. Despite this crucial objective, it's noteworthy that several conventional sealers have been linked to adverse effects, such as impaired wound healing, inflammation, and bone resorption. Therefore, there is a constant search for an optimal sealer that can effectively mimic the properties of lost tissue while maintaining an acceptable level of biological, physicochemical and biocompatible properties. The present study analyzes bioceramic cement's properties in endodontics through a comprehensive review of the available literature. Also, to evaluate the beneficial properties and characteristics of the biomaterials highlighted in this work. Methods: The present study used a systematic review approach to conduct a comprehensive literature search to find relevant publications on bioceramic cement properties in the endodontics field. Articles were retrieved using MeSH keywords and digital searches of journal websites. The selected studies were examined to extract data on sealability, bioactivity, pH, cytotoxicity, color change, radiopacity, edge adaptation, adhesive strength, antibacterial properties and biocompatibility. Results: The results of the reviewed research show that bioceramic endodontic cement has favorable properties for the therapeutic treatment of root canals. The literature highlights the material's biocompatibility, low cytotoxicity, bioactivity, radiopacity, appropriate pH value, favorable edge adaptation, high adhesive strength, practical sealability, antibacterial properties and minimal color change. Conclusion: Research results to date indicate that biomaterials used in endodontics have beneficial properties for root canal therapy and mimicking natural tissue regeneration. The beneficial properties of these materials, such as their biocompatibility, bioactivity, radiopacity, pH stability, edge conformability, adhesion strength, sealability and antibacterial properties, make it a promising replacement for traditional sealers. Further studies are needed to investigate the extended clinical effectiveness of the above intervention and to refine its composition to improve the outcomes associated with endodontic therapies.Öğe The Cytotoxic and Genotoxic Assays of Mg-Ag Alloy Doped with Zn, Ca, and Nd Elements(Springer, 2023) Elen, Levent; Turen, Yunus; Cicek, Bunyamin; Bozer, Busra Moren; Saud, A. Najah; Koc, ErkanMagnesium alloys are being studied for their potential as biodegradable metals, and there is a growing need for multipurpose materials, such as those with more than one use. Binary Mg-Ag alloys were developed as implant materials, combining the beneficial qualities of magnesium with silver's well-known compatibility feature. The result shows that as the amount of the added Ag in the cast alloys increased, the secondary phases (Mg4Ag and Mg54Ag17) that appeared in the structure became more pronounced, and the grains became finer. The best percentage of Ag was found to be 3%, so Ca, Zn and Nd were added, and a study of the biocompatible Mg-3Ag alloy's cytotoxicity and genotoxicity showed that the alloy is safe for cells. In conclusion, 1/1 (total material concentration) cell viability for QE-30, QZ-30, QX-30, and QZEX3000 was 79.39 +/- 1.85, 106.46 +/- 1.99, 93.55 +/- 2.4, and 141.76 +/- 2.71%, respectively. Reducing material concentration by 50% (application at 1/2 concentration) raised viability to 96.83 +/- 1.35, 108.40 +/- 1.92, 124.71 +/- 2.76, and 129.05 +/- 3.5%, indicating the as-cast Mg + 3%Ag + 0.5% Nd-Ca-Zn alloy was extremely biocompatible.Öğe Effect of Rolling Deformation on Microstructure and Mechanical Properties of As-Cast and Rolled ZM21 Magnesium Alloy(Springer, 2023) Ozdemir, Umit; Koc, Erkan; Turen, Yunus; Elen, Levent; Cicek, Bunyamin; Saud, A. NajahThe current study aimed to improve the microstructure and mechanical properties of ZM21 magnesium alloy by using the rolling thermomechanical process at various temperatures (275 and 375 degrees C) and rates (40 and 60%). The rolled samples' grain size was examined, and it was found that the grain size decreased by 40% during hot deformation, reaching a grain size of 15.91 mu m. Surface roughness values were examined and found to be the lowest (parallel and perpendicular to the rolling direction) at a 60% rolling rate in 275 degrees C and the highest 40% at 375 degrees C. The highest tensile strength was obtained at a rolling rate of 60% at 375 degrees C, but it showed brittle fracture during testing. Accordingly, while the 275 degrees C rolled samples showed ductile fracture behavior, a slight reduction in mechanical properties was observed when the rolling ratio was set at 60%.Öğe Effect of Zn content and heat treatment on tribological behavior of biodegradable Mg-xZn alloys in simulated body fluid(Iop Publishing Ltd, 2019) Koc, Erkan; Turan, Muhammet EmreIn this study, magnesium alloys with different weight fractions of zinc were fabricated and heat treatment was performed. Microstructure of specimens was characterized by Light Optical Microscope (LOM). Wear tests were applied under different loads in simulated body fluid. Results show that aging process effects tribological behavior of Mg-Zn alloys positively. Mg-3Zn alloy exhibits best wear performance under 2 N load among the samples. Simulated body fluid possesses lubricant properties during wear tests. 16 h heat treated alloys show better wear characteristic than non-heat treatment samples due to decreasing of internal stress. Abrasive and oxidative wear mechanisms are observed by Scanning Electron Microscope (SEM).Öğe Effects of alloying element and cooling rate on properties of AM60 Mg alloy(Iop Publishing Ltd, 2019) Elen, Levent; Cicek, Bunyamin; Koc, Erkan; Turen, Yunus; Sun, Yavuz; Ahlatci, HayrettinMagnesium and its alloys have become important structural materials in the last couple of decades due to their exceptional and mechanical properties. In this study, the effects of the introduction Cd, Bi, and Sn alloying elements were introduced into AM60 alloys produced from Mg-Al-Mn triple junction in order to improve the microstructural and mechanical properties. The weight percent of the alloying elements was chosen as 0.5% wt besides the introduction of the additional alloying elements, the effect of cooling rate on microstructural and mechanical properties of the alloys have been investigated. The results showed that the alloying elements introduced to AM60 resulted in an improvement in the mechanical properties of the alloys, which is attributed to the changes in the microstructure. The higher cooling rate led to the formation of the finer a-Mg master matrix which in turn enhanced the mechanical properties of the alloys. It was observed that the intermetallic phase of beta-Mg17Al12 at the grain boundaries became thinner due to the rapid cooling rate and the introduction of the alloying elements, and the continuity decreased and the intergranular distance shortened. The addition of the alloying element increased the tensile strength of the AM60 alloy from 140 MPa to 210 MPa and the elongation values increased from 5% to 22%. The effects of the alloying elements and the cooling rate on the hardness and yields properties of the samples were also studied.Öğe Experimental study of in-vitro bioanalysis and in-vivo living tissue biocompatibility of Mg-Zn alloys(Springer Heidelberg, 2023) Comba, Bahat; Cicek, Bunyamin; Comba, Arzu; Sancak, Tunahan; Akveran, Gonul Arslan; Koc, Erkan; Sun, YavuzIn this study in-vitro bioanalysis and in-vivo living tissue biocompatibility were evaluated. Pure Mg and Mg + x Zn (x = 1 and 3 wt%) alloys have been used in the study. In vitro immersion and potentiodynamic corrosion were applied to these alloys in Hank's and artificial seawater solution. The materials were kept in living tissue (gluteus-superficial) for 7 weeks in-vivo (albino-rat). After 4 and 7 week, the control and experimental groups' urine parameters, blood mineral substance levels, and radiographic image controls were evaluated. It was observed that the bio-dissolution level decreased as the Zn-ratio increased. As a result, successful results were obtained in the biocompatible and biodegradable material class of Zn-doped Mg alloys used in the study. The dissolution amount of 1.03 mm/y (for Mg + 3Zn alloy) in Hank's solution was calculated. The % vitality was determined at the level of 117%.Öğe FABRICATION OF OPEN-PORE BIODEGRADABLE MAGNESIUM ALLOY SCAFFOLD VIA INFILTRATION TECHNIQUE(Springer Int Publ Ag, 2022) Temiz, Abdurrahim; Yasar, Mustafa; Koc, ErkanA casting technology based on the infiltration method was used to fabricate a controllable porous Mg alloy structure. The porous structure was designed as a gyroid structure, which is one of the well-known triply periodic minimal surface structures. The model used as a placeholder was produced in a stereolithography apparatus and embedded in NaCl as a mold. In order to define the mechanical properties, sheep bone was cut to the same size as the gyroid structure and these were then analyzed under compression loads. The compression test results were compared with each other and with the Young's moduli of human trabecular bone as stated in the literature. The results of the compression tests indicated that the Young's modulus of the gyroid structure obtained from experimental data was in the range of the Young's moduli of human trabecular bone but lower than the Young's modulus of the sheep bone obtained from the experimental data. A finite element model of the gyroid structure was designed using the LS-Dyna module in ANSYS Workbench and validated with experimental test results. In addition, finite element analysis of the circular cross-sectional beam was also carried out and compared with the gyroid structure in order to evaluate the deformation and fractures. GraphicÖğe FABRICATION OF OPEN-PORE BIODEGRADABLE MAGNESIUM ALLOY SCAFFOLD VIA INFILTRATION TECHNIQUE (Apr, 10.1007/s40962-021-00604-9, 2021)(Springer Int Publ Ag, 2022) Temiz, Abdurrahim; Yasar, Mustafa; Koc, ErkanA correction to this paper has been published: https://doi.org/10.1007/s40962-021-00616-5Öğe 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 Investigating the oxidation behavior of Mg-Zn alloy: Effects of heating rates, gas flow, protective atmosphere, and alloy composition(Chulalongkorn Univ, Metallurgy & Materials Science Research Inst, 2024) Saracoglu, Tugce Nur; Polat, Safa; Koc, Erkan; Mashra, Muwafaq; Najah Saud, Amir; Michalska-domanska, MartaMagnesium-zinc alloys offer promising lightweight properties but are prone to oxidation during high-temperature processing and usage. In this study, the oxidation behavior of Mg-Zn alloy was examined according to the inert gas type flow rate, heating rate and alloy amount. Initially, alloys were produced by adding zinc at weight percentages of 0.5%, 1.5%, and 2% using the casting method. The alloys were characterized using X-ray fluorescence (XRF), X-ray Diffraction (XRD), and scanning electron microscope (SEM) analyses, revealing the formation of dendritic Mg-Zn intermetallic within the alloy. The oxidation behavior of these alloys was examined via differential thermal analysis (DTA) and thermogravimetric analysis (TGA), considering factors such as heating rate, gas flow rate, type of protective atmosphere, and amount of alloying element. The results indicated that the onset temperature of oxidation decreased with increasing heating rate. The effect of gas flow rate varied depending on the heating rate and the type of gas. Under a nitrogen atmosphere, conditions with a heating rate of 20 degrees C center dot min-1 and a gas flow rate of 5 cm3 center dot min-1 resulted in the least oxidation. In an argon atmosphere, a gas flow rate of 5 cm3 center dot min-1 was found to be sufficient to prevent oxidation. However, at a gas flow rate of 1 cm3 center dot min-1, a heating rate of 20 degrees C center dot min-1 was more effective in preventing oxidation. The alloying element (zinc) likely reduced oxidation, particularly at the 1.5% addition level, possibly due to the formation of intermetallic compounds.Öğe Investigation of Intermetallic Phase Fractions and Dry-corrosive Wear Properties in Mg-Al-Si Ternary Alloy(Springer Int Publ Ag, 2024) Cicek, Bunyamin; Elen, Levent; Koc, Erkan; Saud, A. Najah; Sun, YavuzThis study produced a non-standard alloy of 85% Mg, 13.5% Al, and 1.5% Si by weight. In-depth microstructural, chemical, and morphological analyses of the secondary beta phases formed in the MgAlSi alloy were conducted. The formation processes of the intermetallic phases were also examined. Image processing was applied to the obtained microstructures using the Image-J program. The average alloy had a matrix alpha phase to secondary beta phase ratio of approximately 60/40. Furthermore, a dry and corrosive wear test were applied to the MgAlSi alloy by means of reciprocating motion. The wear rate was calculated to be at least 0.00137 mm(3)/Nm, indicating that the unique MgAlSi ternary alloy produced had very high wear resistance due to the presence of intermetallic phases.Öğe Mechanical, Structural and Thermal Properties of Transparent Bi2O3-Al2O3-ZnO-TeO2 Glass System(Springer, 2017) Kabalci, Idris; Koc, Erkan; Ozturk, Sirri SemihOxide based optical glass materials has important potential material in many applications from fiber optic to sensor due to the high transparency and amourphous structures. The objective of this study is to synthesize the novel optical glass materials based on the bismuth and aluminum contents to be able to determine the physical, chemical and mechanical properties by considering the systematic experimental steps. In this study, Bi2O3-Al2O3 based tellurite optical glasses have been prepared by using conventional melt quenching method as a function of the both Bi2O3 and Al2O3 compositions. There is a strong interactions between the glass former and modifier ions that might effect on the structure and mechanical properties. During the experimental steps, thermal, structural and mechanical properties of the prepared glass materials have been determined considering the DTA/DSC, FT-IR spectroscopy, SEM and Vicker's hardness techniques, respectively. Thermal parameters, like glass transition, T-g, onset, T-x, crystallization, T-p, and melting, T-m, temperatures were obtained by using DTA scan.Öğe Mechanical, tribological, and biological properties of short carbon fiber/ nano hydroxyapatite reinforced hybrid epoxy composites(2024) Aljewari, Iman Fouad Munaf; Koc, Erkan; Akgul, YasinThis investigation intends to examine the mechanical, tribological, and biological properties of hybrid epoxy composites reinforced with nanohydroxyapatite (nHA) and short carbon fiber (SCF). Due to its advantageous mechanical, tribological, and biocompatibility features, the proposed E/SCFs-nHA hybrid composites are meant to be recommended for composite structures that can be used to develop fixation plates used in orthopedic applications. In this study, single-layer hybrid composites reinforced with SCFs and nHA in varying ratios, as well as pure epoxy (E) and epoxy-carbon fiber composites, were all fabricated by hand lay-up method. Tensile tests, 3-point bending tests, and Izod impact tests were performed to investigate their mechanical characteristics. Moreover, the hybrid composite samples were tested for their biological properties in simulation body fluid (SBF). Mechanical and biological properties were found to be enhanced according to the results. Consequently, the hybrid composite (E-10CF-3nHA) of 10% carbon fiber (CF) and 3% nanohydroxyapatite (nHA) performed the best in all tests.Öğe A novel strategy to synthesize bioactive glass based on the eutectic reaction of B2O3-K2O(Elsevier Sci Ltd, 2023) Saud, A. Najah; Koc, Erkan; Ozdemir, OlcayMelt-derived route was used to prepare modified bioactive glass-ceramic based on the 45S5 composition with the same network connectivity. Their phase composition, sinterability, and bioactivity were studied. A modified composition was proposed using potassium tetraborate (K2B4O7) to reduce the melting temperature during manufacture. The phase composition and the bioactivity was determined by X-ray diffraction and Fourier transform infrared spectroscopy. Furthermore, the antibacterial properties were evaluated against Enterococcus faecalis. The result shows that glass-ceramics already had P-O and C-O bond functional groups on day 2. These bonds are responsible for the creation of the HCA layer. Scanning electron microscopy (SEM) pictures and Energy Dispersive X-ray Spectroscopy (EDX) investigations showed that, after being immersed in SBF solution, a layer of hydroxyapatite (HA) formed on both BG surfaces on day 2 and that by day 21, HCA cluster crystals had developed. Inductively coupled plasma-optical emission spectroscopy metrics of ionic release from the prepared glass-ceramic, mainly calcium and phosphorus ions in SBF solution, revealed that HCA formation occurred on both BG surfaces, which correlated to the increasing pH within 2 days of incubation; furthermore, it exhibited good antibacterial behavior against the Enterococcus faecalis.
