Person: TÜNÇAY, MEHMET MASUM
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TÜNÇAY
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MEHMET MASUM
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Publication Metadata only Synthesis, characterization, thermal, and antibacterial activity studies on MgO powders(SPRINGER, 2021) GÜLLÜOĞLU, ARİF NİHAT; Demirci, Selim; Yildirim, Bercem Kiran; Tuncay, Mehmet Masum; Kaya, Nusret; Gulluoglu, Arif NihatIn this study, MgO particles were synthesized via sol-gel technique and calcined at 600 degrees C for 2 h with heating rates of 2, 5, 10, and 20 degrees C/min, respectively, for the first time. Comprehensive characterizations were performed by TGA-DTA, XRD, SEM, Raman spectroscopy, BET analysis, photoluminescence techniques. The kinetic parameters were determined by employing four popular model-free methods: Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sonuse (KAS), Starink, and Tang methods. MgO powders had a high crystalline structure regardless of different heating rates based on XRD results. Surface morphologies and surface areas of MgO powders did not change with heating rates. Surface morphologies of MgO powders were found to be nearly spherical with some rounded shape and exhibiting faceted edges in some regions. The specific surface area of MgO powders was found to be 5.9179, 5.6883, 3.6617, and 4.1942 m(2)/g with increasing heating rate, respectively. According to Raman analysis, MgO particles produced at 2 degrees C/min possessed higher surface defects like oxygen vacancies. The PL emission signals for MgO particles were observed at similar to 500 nm consisting of broad peaks, which might be attributed to oxygen defects on the surface of particles. The antibacterial performances of MgO particles were carried out against gram-negative E. coli and gram-positive B. subtilis by means of the agar disc diffusion method. MgO particles produced at a heating rate of 2 degrees C/min possessed the biggest inhibition zone against gram-positive B. subtilis. Having better antibacterial performances for MgO particles produced at 2 degrees C/min heating rate might be attributed to surface oxygen vacancies and surface area, which led to the generation of more reactive oxygen species (ROS). [GRAPHICS] .Publication Open Access An investigation of 3D printing parameters on tensile strength of PLA using response surface method(2023-01-01) TÜNÇAY, MEHMET MASUM; TÜNÇAY M. M.Additive manufacturing has many techniques and has been frequently used and studied recently. The fused deposition modeling (FDM) method, which is one of these techniques, is a widely used three-dimensional (3D) printing method that works with the extrusion principle. The parameters used during printing affect the properties of the final product. This study investigated the effect of print angle, infill density, and perimeter count parameters on the tensile strength characteristics of FDM-printed PLA samples by the response surface method (RSM), an experimental design method. The tensile strengths of the samples produced according to the test lists obtained using the Box–Behnken design were determined. A model equation showing the effect of the relevant parameters was created. From the experiments, the compatibility of the model equation with the experimental results has been demonstrated. The highest tensile strength values were achieved in cases where the print angle was 90°, the infill density was 100%, and the number of walls was 5-6.Publication Metadata only Effect of surface modifications of additively manufactured Ti-6Al-4V alloys on apatite formation ability for biomedical applications(ELSEVIER SCIENCE SA, 2021) GÜLLÜOĞLU, ARİF NİHAT; Demirci, Selim; Dalmis, Ramazan; Dikici, Tuncay; Tuncay, Mehmet Masum; Kaya, Nusret; Gulluoglu, Arif NihatIn this study, Ti-6Al-4V alloys were additively manufactured (AM) with different laser powers. The goal was to investigate the effect of different surface modifications on apatite formation ability. Four types of surface modifications, namely, sandblasting (S), acid etching (E), anodic oxidation (AO) and anodic spark oxidation (ASO), were achieved on the Ti-6Al-4V samples. The microstructure, phase, morphology, roughness and wettability properties were examined by optical microscope (OM), scanning electron microscope (SEM), Xray diffraction (XRD), surface profilometer and contact angle techniques. The bioactivity analysis was performed in simulated body fluid (SBF) for 2 weeks. The results indicated that the microstructure, surface topography, roughness and wettability influenced the apatite formation were affected by the production laser power. Generally, the samples 3 showed higher Ca and P ion ratio value because of percentage of beta phase amount, the presence of bioactive phases on the surfaces. The E3 sample resulted in the best apatite formation theoretically. The etching procedure of AM Ti-6Al-4V in the acidic solution can be applied to improve the apatite formation ability of Ti-6Al-4V alloys. (c) 2021 Elsevier B.V. All rights reserved.Publication Metadata only Effect of heating rate on structure, morphology and photocatalytic properties of TiO2 particles: thermal kinetic and thermodynamic studies(SPRINGER, 2021) KIRAN YILDIRIM, BERÇEM; Dikici, Tuncay; Demirci, Selim; Tuncay, Mehmet Masum; Yildirim, Bercem Kiran; Kaya, NusretIn this study, TiO2 powders were produced via sol-gel route at 500 degrees C for 2 h with distinct heating rates. TGA-DTA, XRD, SEM, Raman spectroscopy, XPS, UV-vis spectroscopy and photoluminescence characterization techniques were carried out for TiO2 powders. Photocatalytic efficiency of TiO2 powders on degradation of methylene blue (MB) solution was examined in terms of different heating rates. Thermodynamic and non-isothermal kinetic study of TiO2 powders were estimated. TiO2 powders showed anatase phase based on XRD results. Surface morphology of TiO2 powders did not change with different heating rates. It can be concluded that heating rate played important role on band gap and photocatalytic activity. The band gap of the TiO2 particles decreased from 3.25 to 2.95 with increasing heating rate. The photocatalytic activity results exhibit that T1 powders have the highest photocatalytic performances. The kinetic constant and photocatalytic degradation rate were 0.00678 min(-1) and 83.48%, respectively. This could be attributed to high crystalline structure and low bulk vacancies or defects. Furthermore, TiO2 powders showed good stability. This study exhibited a new way to enhance the photocatalytic performances of pure TiO2 powders. [GRAPHICS]Publication Open Access Investigation of surface-modified EBM printed Ti-6Al-4V alloys for biomedical applications(2022-11-01) DEMİRCİ, SELİM; TÜNÇAY, MEHMET MASUM; GÜLLÜOĞLU, ARİF NİHAT; DEMİRCİ S., DİKİCİ T., TÜNÇAY M. M. , DALMIŞ R., KAYA N., Kanbur K., Sargin 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 alpha/alpha\"-Ti structures and TiO2 phases were detected by XRD. The surface roughness (Ra) values ranged from 0.25 mu m and 2.86 mu m. The wettability of samples was between around 25 degrees and 104 degrees 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.Publication Open Access Evaluation of the Particle Bonding for Aluminum Sample Produced by Spark Plasma Sintering(SPRINGER, 2016-10) TÜNÇAY, MEHMET MASUM; Tuncay, Mehmet Masum; Nguyen, Lucie; Hendrickx, Philippe; Brochu, MathieuSpark plasma sintering (SPS) is a powder metallurgy process that sinters powder materials within a short time by simultaneous application of electrical current and pressure. SPS differs from other conventional powder metallurgy processes by its heating mechanism, which is Joule heating of the sample within a graphite die. This study investigates the consolidation of aluminum powder by SPS. Different pressures were used and particle bonding evaluated by means of fracture surface analysis. Electrical resistance, obtained from online monitoring of the variation of voltage and current during the process, showed an enhanced descent at 0.3 T (m), and the area under this drop was associated with ductility: the greater the area, the higher the ductility. This temperature corresponds to a significant increase in the hardness ratio of the oxide layer to aluminum, where breakdown of the oxide layer becomes easier, permitting enhanced metallurgical bonding between the powder particles.Publication Open Access A study of heating rate effect on the photocatalytic performances of ZnO powders prepared by sol-gel route: Their kinetic and thermodynamic studies(ELSEVIER, 2020-03) TÜNÇAY, MEHMET MASUM; Demirci, Selim; Dikici, Tuncay; Tuncay, Mehmet Masum; Kaya, NusretIn this work, ZnO particles were fabricated by sol-gel method at different heating rate at 500 degrees C for 2 h. The ZnO powders were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy and photoluminescence, respectively. The effect of heating rate on photocatalytic activities of ZnO particles was evaluated by degradation of methylene blue (MB). The non-isothermal kinetics and thermodynamic properties were also estimated. The XRD results showed that ZnO had hexagonal wurtzite structure. The different heating rate didn't influence the surface morphology of ZnO powders. It was observed that the heating rate had a profound effect on reduction of band gap and photocatalytic performances. The band gap of the ZnO particles varied from 3.10 to 3.17. The ZnO sample prepared at 1 degrees C/min exhibited the highest photocatalytic activity. Its relative photocatalytic degradation rate and kinetic constant were 92.7% and 1.069x10(-2) min(-1), respectively. The results might be ascribed to low bulk vacancies, high surface oxygen vacancies and narrow band gap energy. Also, ZnO photocatalysts showed good stability after four sequence tests. This study provides a new strategy to improve the photocatalytic performances of ZnO photocatalyst for the degradation of organic contaminant.Publication Open Access Spark plasma sintering and spark plasma upsetting of an Al-Zn-Mg-Cu alloy(ELSEVIER SCIENCE SA, 2017-09) TÜNÇAY, MEHMET MASUM; Tuncay, Mehmet Masum; Muniz-Lerma, Jose Alberto; Bishop, Donald Paul; Brochu, MathieuAl-Zn-Mg-Cu alloy powder Alumix 431D was sintered at 400 degrees C by spark plasma sintering (SPS) and upset forging was applied to the sintered sample through SPS. Densities of 99.1 +/- 0.3% and 99.8 +/- 0.1% of theoretical were obtained for the sintered and forged samples, respectively. T6 temper was carried out on the samples and microstructure analysis and mechanical properties before and after heat treatment were evaluated. Microhardness of 173 +/- 3 and 172 +/- 3 HV were attained in the T6 temper of as-sintered and forged samples, respectively. The flexural strength and strain values were significantly improved after the forging process, which can be mainly attributed to the better particle bonding in addition to the occurrence of some recrystallization. Significant loss in the ductility was observed after the T6 temper.Publication Open Access Spark Plasma Sintering and Upsetting of a Gas-Atomized/Air-Atomized Al Alloy Powder Mixture(SPRINGER, 2017-10) TÜNÇAY, MEHMET MASUM; Tuncay, Mehmet Masum; Muniz-Lerma, Jose Alberto; Bishop, Donald Paul; Brochu, MathieuAl-Zn-Mg-Cu alloy powder, Alumix 431D, was modified by replacing the native air-atomized pure Al particles with gas-atomized pure Al. Samples were sintered using spark plasma sintering (SPS), and upset forging was applied to the sintered samples by SPS. Densities over 98 and 99% of theoretical were obtained for the sintered and forged samples, respectively. Microstructural analysis and characterization of all samples were done using energy-dispersive spectroscopy and x-ray diffraction. Mechanical properties were evaluated using microhardness and flexural strength and strain measurements. The microhardness value of the T6 tempered sample was comparable to that of its wrought counterpart AA7075. Particle bonding after sintering was incomplete and reveals that composite oxide layer of Al-Zn-Mg-Cu alloy powder is difficult to disrupt, and it is necessary to apply a secondary process like forging to improve particle bonding. The loss in ductility following T6 tempering is ascribed to void formation due to the dissolution of the secondary phases, remaining undissolved precipitates, and a localized lack of cohesion between particles.