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Öğe Aqueous degradation and atomic layer deposition (ALD) stabilization of BaAl2O4: Eu2+, Dy3+long afterglow phosphors(Elsevier, 2023) Karacaoğlu, Erkul; Uyaner, Mesut; Okyay, Ali Kemal; Losego, Mark D.This paper presents the aqueous degradation mechanisms of BaAl2O4:Eu2+, Dy3+ phosphors and demonstrates an ability to prevent degradation via Al2O3 nano encapsulation of powders by atomic layer deposition (ALD) technique. Phosphor powder is synthesized from the solid-state reaction method. The aqueous degradation of this phosphor is systematically studied. This phosphor is found to hydrolyze and degrade within just 30 min of exposure in water. The degradation of BaAl2O4 host lattice directly affects the blue-green light emission at 497 nm, producing blue-and red-emissions that are peaked at 429 nm and 687 nm, respectively. Hydrated and structural decomposed BaAl2O4 reveals a continuous change in the phase assemblage over 30 days of immersion. To prevent this rapid degradation, use of a protective nanocoating was investigated. 10 nm Al2O3 coatings were applied to the surface of the phosphor powder via ALD. ALD coated BaAl2O4:Eu2+,Dy3+ phosphor retains its phosphorescence for at least 7 days of water exposure. Successful encapsulation of such phosphor particles will make them possible to use in aqueous applications or store in long-term humid environments.Öğe Atomic layer deposition (ALD) of nanoscale coatings on SrAl2O4-based phosphor powders to prevent aqueous degradation(Wiley, 2020) Karacaoglu, Erkul; Ozturk, Esra; Uyaner, Mesut; Losego, Mark D.The aqueous degradation of Eu2+-activated and Dy3+-codoped strontium aluminate (SrAl2O4:Eu2+, Dy3+, SA2-Green) long afterglow phosphors synthesized from solid-state reaction and coated with nanoscale metal oxide protective layers (<= 12 nm) via atomic layer deposition (ALD) is investigated. Uncoated phosphor powders degrade rapidly upon water immersion and lose their green phosphorescence within 48 hours of water exposure. Postmortem investigations reveal hydration and decomposition of the SrAl2O4 phase. ALD of 10 nm Al2O3 or 12 nm TiO2 is found to significantly improve the powder's resistance to aqueous degradation. All ALD-coated powders show minimal structural and chemical degradation and retain phosphoresence after 48 hours of water immersion. This enhanced durability offers a new pathway for applying long afterglow phosphors to outdoor applications like roadway markings or safety signage and for their incorporation into more eco-friendly waterborne coatings.Öğe E-camı/epoksi kompozit boruların darbe cevabına vurucu geometrisinin etkisi(2016) Uyaner, Mesut; Kara, MemduhBu çalışmada filaman sarım yöntemiyle üretilmiş 55 sarım açısına sahip 10 tabakalı E-camı/epoksi kompozit boruların düşük hızlı darbe cevabına vurucu geometrisinin etkisi deneysel olarak araştırılmıştır. V yatağı üzerine yerleştirilen kompozit boru numunelerine düşük hızlı darbe cihazı kullanılarak, 24 mm ve 12 mm çaplı yarı-küresel ve 120 piramit uca sahip vurucularla düşük enerjili darbe yapılmıştır. Düşük enerjili darbe deneyleri 5 J, 10 J ve 15 J enerji seviyelerinde yapılmıştır. Vurucu geometrisine ve enerji seviyesine bağlı olarak elde edilen kuvvet-zaman ve kuvvet yer değiştirme değişimleri incelenmiştir. Ayrıca farklı geometrilere sahip vurucuların kompozit boru numunesinde meydana getirmiş olduğu hasarlar haritalanmış, vurucu geometrisine bağlı olarak değişen hasar alanları tetkik edilmiştirÖğe Effect of Co addition on microstructure and mechanical properties of new generation 3Cr-3W and 5Cr-3W steels(Elsevier - Division Reed Elsevier India Pvt Ltd, 2021) Arici, Gokhan; Acarer, Mustafa; Uyaner, MesutIn this study, the effect of Cr and Co on microstructure and mechanical properties of low Cr-W steels was investigated. For this goal, 3% Cr-3%W and 5% Cr-3%W steels, this may be an alternative to new generation low Cr steels, containing 0%, 0.5%, 1.5%, 3%, 4.5% Co, produced by casting and hot rolling. The samples were annealed at 1100 degrees C for 1 h, followed by quenching in air and tempering for 2 h at 710 degrees C. Ferrite, bainite, and martensite phases were determined in various volume fractions according to the chemical composition. Carbides precipitated within the grain and grain boundaries during tempering. Co bearing caused an increase of A1, A3, and Curie temperatures. Co slightly increased hardness and strength in both 3 Cr and 5 Cr alloys. However, the hardness and strength of 5 Cr alloys with all Co ratios were almost same that of 3 Cr alloys. The Charpy-V impact energies of 5 Cr steel are lower than 3 Cr steel with the same Co amount. The addition of Co up to 1.5% in steels with 3 Cr did not make any major changes in the notch toughness. However, the addition of 3% Co to the alloy significantly reduced impact energy. In 5 Cr steel, notch toughness generally decreased with the increase of Co amount. (C) 2021 Karabuk University. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Öğe The Effect of Hydrothermal Aging on the Low-Velocity Impact Behavior of Multi-Walled Carbon Nanotubes Reinforced Carbon Fiber/Epoxy Composite Pipes(Springer, 2021) Kara, Memduh; Ak, Safa; Uyaner, Mesut; Gunoz, Alper; Kepir, YusufChemical transmission lines, petroleum and natural gas lines, pressure vessels, and pipes used in thermal facilities are expected to maintain their mechanical properties for many years without being damaged and not to be corroded in working conditions. The composite materials are the right candidate for these harsh conditions due to their superior properties. Reinforcement of nanoadditives to composite materials improves both the mechanical properties and the resistance to environmental conditions, thereby increasing the lifetime. In this study, multi-walled carbon nanotube (MWCNT) reinforced [+/- 55 degrees] carbon fiber/epoxy composite pipes produced with filament wound method were used. It was hydrothermally aged in 80 degrees C distilled water for 1, 2, 3 weeks in order to examine the effect of environmental conditions. In order to investigate its resistance against loads that may occur in working conditions, ring tensile tests (ASTM D 2290-16 procedure A), and low-velocity impact tests at 5, 10, 15 J, energy levels were carried out. The effect of hydrothermal aging on neat and MWCNT added epoxy composite had been examined by considering the aging period. Consequently, the impact resistance of neat and MWCNT added samples decreased with the aging process. Besides, tangential tensile strength loss was 17% in MWCNT reinforced sample and 13% in the neat sample.Öğe Effects of nano reinforcing/matrix interaction on chemical, thermal and mechanical properties of epoxy nanocomposites(Sage Publications Ltd, 2021) Yazman, Sakir; Uyaner, Mesut; Karabork, Fazliye; Akdemir, AhmetThis article investigates the impact of addition various types of nanoparticles with different structural, dimensional, and morphological properties on the interphase region formed between the particle/matrix and the curing behavior of the epoxy affect the nanocomposite material properties. For this purpose, epoxy nanocomposites (NCs) were produced by adding multi-walled carbon nanotube (MWCNT) and alumina (Al2O3) nanoparticles (NPs) into the epoxy matrix at different rates (0.5-2.0 wt.%). The effects of the particle/matrix interaction on the properties of the composite have been revealed by chemical, thermal, mechanical analyzes and microstructure investigations. An increase in the absorption density, which reveals the physical interaction of nanoparticles with the epoxy matrix, was observed in Fourier-transform infrared spectroscopy. Absorption vibration peak intensities in nanocomposite samples were at most 1.0 wt.% Al2O3 and 1.25 wt.% CNT added nanocomposites. It was observed that the T-g value increased depending on the number of nanoparticles. The addition of Al2O3 increased T-g values more than CNT. Besides, the mechanical properties of NCs were determined by tensile tests. The highest increase in mechanical properties was achieved by adding 1.25 wt.% CNT and 1.0 wt.% Al2O3, respectively. Mechanical properties tended to decrease at higher addition rates. The shape, size, amount, and distribution of nanoparticles added into the epoxy matrix directly affected the NCs' properties. It has been determined that homogeneously dispersed spherical Al2O3 nanoparticles are more effective than fiber-shaped CNTs in the properties of NCs.Öğe Filaman Sarım ile Üretilen CTP Kompozit Borularda Tabaka Sayısının Teğetsel Gerilme Dayanımına Etkisi(2017) Kara, Memduh; Uyaner, MesutCam takviyeli plastik (CTP) kompozit boruların diğer boru çeşitlerine göre birçok üstün özelliği vardır. Bunlar, kimyasal maddelerin oluşturacağı korozyona karşı dayanım, olumsuz hava koşullarına ve UV ışınlara karşı dayanım, istenilen boyutlarda seri üretim imkânı ve uzun ömürlü olması gibi özelliklerdir. Bütün bu özellikleri nedeniyle petrol ve doğalgaz iletim hatlarında ve kimyasal akışkanların iletim hatlarında yaygın olarak kullanılmaktadır. Kullanım alanı hızla artmakta olan CTP kompozit boruların mekanik özelliklerinin belirlenmesi için birçok test yöntemi geliştirilmiştir. Cam takviyeli plastik boruların teğetsel gerilme dayanımı; ASTM D 1599 standardına göre hidrolik basınç testi ve ASTM D 2290 standardına göre halka çekme testi ile tespit edilmektedir. Bu çalışmada 6, 8 ve 10 tabakalı olacak şekilde filaman sarım yöntemiyle 55 sarım açısında üretilen Ecamı/epoksi kompozit boruların teğetsel gerilme dayanımı her iki yöntem kullanılarak belirlenmiştir. Her iki yöntemden elde edilen sonuçlar birbirleriyle karşılaştırılarak değerlendirilmiştir. Ayrıca CTP kompozit borularda statik iç basınç patlatma testi esnasında ve halka çekme testi esnasında oluşan hasar gelişimi değerlendirilmiştir.Öğe Low velocity impact response and damages of GFRP composite tubes under room and cryogenic temperatures(Sage Publications Ltd, 2021) Kara, Memduh; Arat, Mustafa; Uyaner, MesutIn this paper, we have investigated the damages of glass fiber reinforced plastic (GFRP) composite tubes under the effect of low-velocity impact (LVI) at cryogenic environment conditions and room temperature. A GFRP composite tube consists of 6 layered E-glass/epoxy samples with a +/- 55 degrees winding angle, which produced by the filament winding method. Composite tubes either at room temperature or conditioned by liquid nitrogen at different temperature values (273 K, 223 K, 173 K, and 77 K) were impacted at 5, 7.5, and 10 J. Also, force-time and force-displacement graphs were plotted. The damaged regions of the samples were scrutinized. The damage areas of the GFRP composite tubes were smaller as the temperature decreased. However, the energy absorbed at low-temperature conditions was slightly higher than that absorbed in room temperature. Besides, no micro-cracks developed in the composite tubes after cryogenic conditioning.Öğe Metal tabakalı kompozitlerin düşük hızlı enine darbeye karşı davranışlarının incelenmesi(2016) Kara, Memduh; Uyaner, MesutBu çalışmada metal kompozit levhaların düşük hızlı enine darbe davranışları incelenmiştir. 1 mm kalınlığında St37 DKP çelik ve 1050-H14 alaşımlı alüminyum plakalar kullanılarak dört farklı yerleşim düzeninde oluşturulan üç katmanlı kompozit levhalar farklı enerji seviyelerinde düşük hızlı darbe testlerine maruz bırakılmışlardır. 150x150 mm ebatlarında kesilen metal levhalar üç alüminyum, üç çelik, aliminyumçelikalüminyum ve çelikalüminyumçelik olacak şekilde dizilerek dört tarafı ankastre olacak şekilde bağlanmıştır. Deneylerde kullanılan vurucu kütlesi 6,35 kg olup 24 mm yarı küresel geometriye sahiptir. Hazırlanan her bir deney numunesinin ortasına 10J, 20J, 30J, 40J ve 50J enerji seviyelerinde darbe testleri yapılmıştır. Darbe testleri sonucu elde edilen kuvvet-zaman, hız-zaman ve kuvvet-yer değiştirme değişimleri grafikler halinde incelenmiştir. Her bir deney numunesinde meydana gelen hasarların boyutları ve hasar şekilleri değerlendirilmiştir.Öğe Production of Bioactive Various Lattices as an Artificial Bone Tissue by Digital Light Processing 3D Printing(Springer, 2021) Dokuz, M. Enes; Aydin, Mustafa; Uyaner, MesutThis study aims to find which lattice type and which ingredient is the best for the bone lattice for future grafting operations. Four types of lattice parts with micro and high porosity were designed to resemble the human bone structure and reach its light-weight and high surface area properties. Hydroxyapatite (HA) and tricalcium phosphate (TCP) were used in the photopolymer resin mixture for (Digital Light Processing) DLP 3D printing to give high bioactivity capability to the parts. In conclusion, microporosity HA- and TCP-doped parts were printed successfully with the DLP technique. Bioactivity tests were carried out with parts that were soaked in simulated body fluid (SBF). There is no significant weight difference in lattice parts in the time. Four weeks are sufficient time for the test. End of 2 weeks, calcium phosphate particles with around a diameter of 50-75 mu m, and end of 4 weeks, calcium phosphate particles with around a diameter of 80-225 mu m were observed. Apatite precipitation areas were grown on the surface in time. SEM and XRD results indicate that HA-doped and TCP-doped specimens are bioactive. A more mass increase was observed in the HA-doped specimen compared to the TCP-doped specimen.Öğe Repairing impact damaged fiber reinforced composite pipes by external wrapping with composite patches(Elsevier Sci Ltd, 2015) Kara, Memduh; Uyaner, Mesut; Avci, AhmetRepairs made with composite patches on impact damaged fiber reinforced composite pipes offer distinct advantages over traditional repairs in addition to reduced cost. In this study, effects of number of patch layers on the burst pressure of low velocity impact damaged tubes that have been repaired with composite patches were investigated. The tubes were pressurized up to 32 bar prior to impact. The pre-stressed glass fiber reinforced plastic tubes were damaged by applying low velocity impacts at different energy levels (5, 10 and 15 J). The damaged areas of the affected tubes were repaired with 2, 4 and 6 layers of glass/epoxy fabrics. The repaired tubes were then failed catastrophically by being subjected to monotonic internal burst tests based on ASTM D 1599-99 standards. Changes in the tubes' burst pressures were recorded and the resulting damages on the tubes were studied. It was found that, for all the energy levels employed in this study, a six-layered patch repairing is suitable for the retrofitting of impact damaged tubes. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Solid particle erosion behavior of thermal barrier coatings produced by atmospheric plasma spray technique(Taylor & Francis Inc, 2019) Kaplan, Mustafa; Uyaner, Mesut; Avcu, Egemen; Avcu, Yasemin Yildiran; Karaoglanli, Abdullah CahitThermal barrier coatings (TBCs) are commonly applied specifically for aerospace applications in which they are subjected to air-borne particles. Therefore, solid particle erosion behavior of all coating layer has been an important phenomenon and erosion behavior of various TBCs has been widely investigated in literature. In the present study, CoNiCrAlY and yttria stabilized zirconia (ZrO2 + 8% Y2O3) powders were deposited on Inconel 718 nickel based super alloy substrate. Atmospheric plasma spraying technique was applied for the deposition of the metallic bond coat and the ceramic top coats. Erosion tests were carried out under various particle impingement angles with an air jet erosion tester. Afterwards, eroded surfaces of the specimens were investigated with a three-dimensional (3D) optical surface profilometer (noncontact) and scanning electron microscope. The erosion rates, the areal surface roughness values, the 3D surface topographies, and the surface morphology of the specimens were evaluated based on the particle impingement angle to understand the solid particle erosion behavior of the produced coatings. The maximum erosion rates occurred at 60 degrees impingement angle which is an indication of semi-ductile/semi-brittle erosion behavior. Furthermore, the surface roughness values and surface topographies also dramatically varied depending on the impingement angle. Deeper and wider erosion craters formed at 60 degrees impact angle and the erosion craters were visualized by profilometer analysis.Öğe Virtual Investigation on the Response of Glare to Low Velocity Impact(IEEE, 2023) Dag, Tolunay; Yildirim, Nur; Senturk, Gokhan; Durmazoglu, Metin; Yildirim, Serap; Uyaner, MesutDue to the increasing cost of experiments and the increased time required to complete the experimental process, it is more economical to conduct experiments in the form of virtual tests. Therefore, low velocity impact simulation was carried out on fiber metal laminates, FMLs with an impactor with various weights in our study. LS-DYNA software was selected to perform the simulation. Fiber metal laminate is composed of 2024-T3 Aluminum and Glass/Epoxy layers. The layers are modeled as isotropic, and anisotropic material. The stacking sequence of FML is (Al/0/90/Al). Two opposite sides of the square shaped FML are fixed and the other sides are left free. Steel strikers with masses of 0.15 kg, 0.30 kg and 0.45 kg were used in the analyses, respectively. The speed of the striker at first contact with the FML is 10 mm/ms. As a result of the tests, force-time, force-displacement, velocity-time and energy - time variations were also obtained. The results were presented as graphs. It has been found that the FML structure absorbs an average of 73.4% of the impact energy because of the low-velocity impact, thus preserving the integrity and functionality of the designed structure. Thanks to such numerical experiments carried out before production, the mechanical properties of the designed structure can be evaluated.Öğe Virtual Testing of Laminated Composites Subjected to Low-Velocity Impact(Springer, 2023) Uyaner, Mesut; Kara, Memduh; Kepir, Yusuf; Gunoz, AlperComposite materials have many superior properties compared to traditional materials. However, due to its high cost, the composite structure must be designed correctly at the beginning. Composite structures are particularly sensitive to impact loads. Predicting the damages that will occur in the composite structure due to impact and designing accordingly will contribute significantly to the reduction of the negative situation caused by the high cost. In this study, the dynamic response of E-glass fiber-reinforced polymer (GFRP) laminated composites subjected to low-velocity impact was studied experimentally and numerically. Thus, it is aimed to determine the damage behavior with virtual tests before the composite structures are produced. Low-velocity impact tests were performed on composite samples that have different dimensions at impact velocities of 2.0, 2.5, and 3.0 m/s. Low-velocity impact tests were carried out by a vertical drop weight testing machine. A cylindrical impactor with a semispherical nose having a mass of 30 kg and a radius of 12 mm was utilized in the low-velocity impact tests. The impact was applied to the center of the composite laminates, the short sides of which are fixed. Numerical analyses were performed using the LS-DYNA finite element method package program with Tsai-Wu matrix failure criterion damage mechanics-based material model MAT 055. In addition, mesh optimization for the failure modeling parameters of the material model Mat_Enhanced_Composite_Damage (MAT 055) was realized. An agreement of up to 90% was observed between the numerical analysis and the experimental results. According to the results obtained from the experimental and numerical studies, it was seen that the size of composite plates significantly affects the impact behavior of the materials. In addition, it was observed that the ratio of the absorbed energy to the total energy increased and the damage to the samples increased with the increase of the impact energy.
