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Öğe Analysis of data on indentation load against penetration depth for bulk MgB2 crystal using indentation work and Oliver-Pharr approaches(Elsevier Science Sa, 2008) Uzun, O.; Guclu, N.; Kolemen, U.; Sahin, O.Vickers microindentation tests were carried out on a bulk MgB2 superconductor with the load of ranging from 300 to 1500 mN at a room temperature. The load-penetration depth curves and the energy data (the absolute, the total, the plastic, and the elastic energy) were analyzed to evaluate the mechanical properties. Hardness and elastic modulus values were calculated by the Oliver-Pharr method and the work of indentation approach. The work of indentation hardness and elastic modulus were calculated directly from the energy of indentation without the need for estimating displacement, areas or volumes, which can be time consuming and inaccurate. It was found that the hardness and elastic modulus increased with decreasing load (i.e. indentation size effect). In addition, the hardness and elastic modulus calculated from the work of indentation approach seem to correlate very well with Oliver-Pharr method at high peak load. Some specific material constant describing the properties of materials were also calculated as total energy, plastic energy, elastic energy, elastic-total energy, plastic-total energy and elastic-plastic energy constants. (C) 2008 Elsevier B.V. All rights reserved.Öğe Comparison of mechanical properties of boronized and vanadium carbide coated AISI 1040 steels(Natl Inst Science Communication-Niscair, 2009) Calik, A.; Taylan, F.; Sahin, O.; Ucar, N.Comparison of mechanical properties of medium carbon steel AISI 1040 for vanadium carbide coated (VCC) and boronized conditions has been studied by means of microhardness, tensile and impact tests. For the treated steels, the boriding and vanadizing processes have been carried out in the same conditions, i.e., at a temperature of 1210 K for 4 h. The thickness of diffusion layer has been measured as 5 pm and 100 mu m for the VCC and the boronized steels, respectively. In laboratory conditions, the VCC steels show considerably higher strength and surface hardening with respect to the untreated and the boronized steels. At the same time, Charpy V-notch impact tests have also been carried out for the steels with and without surface hardening. It is concluded that coating is effective in improving the mechanical performance of AISI 1040 steels.Öğe Detection and survival of Campylobacter in chicken eggs(Blackwell Publishing Ltd, 2003) Sahin, O.; Kobalka, P.; Zhang, Q.Aims: Campylobacter jejuni, a food-borne human pathogen, is widespread in poultry; however, the sources of infection and modes of transmission of this organism on chicken farms are not well understood. The objective of this study was to determine if vertical transmission of C. jejuni occurs via eggs. Methods and Results: Using a temperature differential method, it was shown that Campylobacter had limited ability to penetrate the eggshell. When C. jejuni was directly inoculated into the egg yolk and the eggs were stored at 18°C, the organism was able to survive for up to 14 days. However, viability of C. jejuni was dramatically shortened when injected into the albumen or the air sac. When freshly laid eggs from Campylobacter-inoculated specific pathogen-free (SPF) layers were tested, C. jejuni-contamination was detected in three of 65 pooled whole eggs (5-10 eggs in each pool) via culture and PCR. However, the organism was not detected from any of the 800 eggs (80 pools), collected from the same SPF flock, but kept at 18°C for 7 days before testing. Likewise, Campylobacter was not recovered from any of 500 fresh eggs obtained from commercial broiler-breeder flocks that were actively shedding Campylobacter in faeces. Also, none of the 1000 eggs from broiler breeders obtained from a commercial hatchery were positive for Campylobacter. Conclusions: These results suggest that vertical transmission of C. jejuni through the egg is probably a rare event and does not play a major role in the introduction of Campylobacter to chicken flocks. Significance and Impact of the Study: Control of Campylobacter transmission to chicken flocks should focus on sources of infection that are not related to eggs.Öğe Effects of ZnO addition on mechanical properties of Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06O10 prepared by a wet technique(Elsevier Science Sa, 2009) Karaca, I.; Uzun, O.; Koelemen, U.; Yilmaz, F.; Sahin, O.In this study, ZnO molar wt% 0, 5,10,20,30, and 50 added Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06O10 superconductors were prepared by wet technique. The experimental works consist of powder X-ray diffraction (XRD) for phase analyses and c-axes parameters, scanning electron microscopy (SEM) for microstructure examination, and microhardness measurements for mechanical properties. These measurements showed that Zn-added material, in comparison with the pure sample, had increased c-axes parameters and decreased grain size. In addition, the experimental results of microhardness measurements were analyzed using Oliver-Pharr model. It was observed that the change of indentation hardness (H-rr) and reduced elastic modulus (E-r) values showed an increasing trend with ZnO addition and exhibited peak load dependence (i.e., indentation size effect (ISE)). (C) 2008 Elsevier B.V. All rights reserved.Öğe Evaluation of Surface Properties of Four Tooth-Colored Restorative Materials(Polish Acad Sciences Inst Physics, 2015) Arslanoglu, Z.; Altan, H.; Sahin, O.; Tekin, M. G.; Adiguzel, M.The aim of this study is to compare microhardness, roughness and micromorphology of the examined materials of a newly developed glass carbomer dental filling material to two different resin modified glass ionomers and a glass ionomer dental filling material. Specimens tested were prepared from a glass carbomer without gloss (Glass Carbomer, GCP), a glass carbomer (Glass Carbomer, GCP) with gloss, two different resin modified glass ionomers (Fuji II LC, GC and Riva LC, SDI) and a glass ionomer (Equia, GC). Seven specimens of each material were prepared according to manufacturer's recommendations. After setting, samples were polished and stored in 37 degrees C distilled water for 24 h. Indentation microhardness of examined restorative materials was measured using the Vickers indenters. In addition surface roughness of the materials was measured using surface profilemeter. Surface morphology was analyzed by using scanning electron microscopy. There was a significant difference in microhardness and roughness between the restorative materials (p < 0.05). The highest microhardness was measured for Equia and lowest for glass carbomer with gloss. The roughness was fully definite for the glass carbomer with gloss and indefinite for the glass carbomer without gloss. Small cracks and voids were observed in all groups. High viscosity glass ionomer cement Equia exhibits the high physical strength than RMGIC. Gloss application does not influence the hardness behavior of GCP.Öğe Fabrication and mechanical characterization of rare earth permanent magnet SmCo5 films(Elsevier Science Sa, 2017) Kuru, M.; Sahin, O.; Ozarslan, S.; Ozmetin, A. E.This study reports mechanical properties of rare earth permanent magnet (REPM) SmCo5 thin films fabricated by RF magnetron sputtering technique. 1 mu m thick SmCo5 thin films were grown on Si (100) substrate at room temperature, and later they were annealed at 400 degrees C. Great care has been taken to decrease O-2 in the chamber throughout deposition. Mechanical and Structural properties of SmCo5 thin films were researched using the nanoindentation and in situ scanning probe microscopy (SPM), Grazing Incident X-ray Diffraction (GIXRD) and Scanning Electron Microscopy (SEM) techniques. Nanoindentation-induced plasticity of SmCo5 thin film was characterized by in situ SPM imaging of indented cross-sections. Nanoindentation results show load-displacement curves are continuous and smooth that there is no pile-up and sink-in behavior. Furthermore, both elastic modulus and nano hardness values of REPM SmCo5 exhibit peak load dependence. Nanohardness increases with increasing indentation test load, while the reduced modulus decrease with increasing indentation test load. The obtained values of the intrinsic nanohardness and intrinsic reduced modulus are 3.47 +/- 0.07 GPa and 43.09 +/- 1.60 GPa, respectively. (C) 2016 Elsevier B.V. All rights reserved.Öğe Hardness Behavior of Alumina-Zirconia Nanocomposites Synthesized by Gel Process(Polish Acad Sciences Inst Physics, 2013) Sahin, O.; Hasde, A.; Gocmez, H.; Tuncer, M.; Cetinkara, H. Ali; Guder, H. Salih; Sahin, E.The alumina-zirconia composites are one of the relatively good and promising candidates for biomaterials application, due to biocompatibility and their mechanical properties that combines high flexural strength with a high toughness. The aim of the present work is to analyze the mechanical properties of these composites, where zirconia content was varied from 5 to 50 wt%. The citrate gel method, similar to the polymerized complex method, was used to synthesize these ceramics. Scanning electron microscopy, X-ray diffraction and microhardness tests are used to characterize synthesized materials. The examined material exhibits the behaviour of indentation size effect. Modified proportional resistance model are used to analyze the load dependence of the microhardness. X-ray diffraction analysis was used to calculation of the grain size and dislocation density. It is found that hardness is decreased when the zirconia content increases with enlargement of grain size. DOI: 10.12693/APhysPolA.123.299Öğe Influence of CaO on the Nanohardness Behaviour of AZ63 Magnesium Alloys Produced by Mechanical Alloying Method(Polish Acad Sciences Inst Physics, 2016) Boztas, M.; Ozarslan, S.; Sahin, O.In this study we aimed to produce AZ63 magnesium alloys containing different amounts of CaO, to investigate the nanohardness behaviour of the resulting alloys. These alloys were produced by mechanical alloying under argon atmosphere. Magnesium based alloys with the initial CaO content of 0.1%, 0.3%, and 0.5% were produced by high-energy ball milling, followed by process that involved cold pressing and sintering. These alloys were characterized using scanning electron microscopy, scanning probe microscopy, X-ray diffraction, and nanoindentation methods. Unloading segments of nanoindentation curves were analyzed using Oliver-Pharr method. Experimental results show that measured nanohardness exhibits a peak load dependence. As a result, in these alloys the microstructure and nanohardness depend on the content of CaO.Öğe Influence of Pd Addition of CoCrMo Biomedical Alloys on the Microhardness Behaviour(Polish Acad Sciences Inst Physics, 2015) Sahin, O.; Uzunoglu, S.; Sahin, E.CoCrMo alloys are often used as the material for metal artificial joint because of their high corrosion resistance and mechanical properties. In this study CoCrMo alloys having different palladium amount of produced by investment casting method. Scanning electron microscopy, X-ray diffraction method and indentation tests were used to examine the mechanical properties of the alloys. Indentation experiments were carried out using Vickers indenter that the loads range from 0.245 to 9.8 N. The alloys exhibit significant load-dependence (i.e., indentation size effect). Meyer's law, proportional specimen resistance model, and Hays-Kendall model were used to analyze the load dependence of the hardness. As a results for load-independent determination of the CoCrMo alloys, the Hays-Kendall model is found to be more effective than the proportional specimen resistance model and microhardness values decreases with increase of the Pd content.Öğe Influence of Rare Earth Element on the Mechanical Properties of ZE41 Magnesium Alloys Produced by Mechanical Alloying(Polish Acad Sciences Inst Physics, 2016) Sahin, O.; Ertsak, F. Haluk; Oztekin, K.; Ozarslan, S.In this work, we have intended to synthesize ZE41 Magnesium alloys having varying content of Ce of 0.3, 0.6 and 0.9 wt.% and to investigate mechanical properties of these alloys. Alloys were produced by mechanical alloying under argon atmosphere. Structural, and mechanical properties of these alloys were investigated by means of XRD, SEM and nanoindenter analysis. From the XRD data it is found that as the Ce content increases, the crystallite size also increases. On the other hand, the hardness of the alloys decreases with the increasing Ce content. Indentation results show that the measured hardness displays a peak load dependence. Load-independent hardness was calculated by Hays-Kendall approach. As a results, it was found that Ce-doping modifies the microstructure and hardness of the alloy.Öğe Mechanical and structural properties of Li-doped CuO thin films deposited by the Successive Ionic Layer Adsorption and Reaction method(Elsevier Science Sa, 2020) Bayansal, F.; Sahin, O.; Cetinkara, H. A.Lithium-doped CuO thin films with different concentrations are deposited by the Successive Ionic Layer Adsorption and Reaction technique on glass substrates. The films are characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, UV-Vis. Spectroscopy, nanoindentation and in-situ scanning probe microscopy. Scanning electron microscopy showed uniform film surface and smaller particle size with increasing Li concentration. X-ray diffraction patterns revealed decreasing crystallite size with increasing Li concentration. The Raman spectra revealed CuO phases and a secondary phase of Cu2O at high doping concentrations especially after the concentration of 1.0 at.% Li. UV-Vis. Spectroscopy results indicated that the transmittance and bandgap values could be modified with Li-doping. Both of them are found to be increasing with increasing Li concentration. All indentation test load curves exhibited a smooth shape without any detected pop-in. The results of the nanoindentation test revealed that the nanohardness and elastic modulus increased with Li-doping.Öğe Mechanical Characterization of CoCrMo Alloys Consisting of Different Palladium Ratios Produced by Investment Casting Method(Polish Acad Sciences Inst Physics, 2015) Sahin, O.; Uzunoglu, S.; Sahin, E.CoCrMo alloys are one of the most commonly used materials for hip arthroplasty, knee and dental because of its mechanical properties, corrosion resistance, wear resistance and biocompatibility. In this study, CoCrMo alloys consisting of 1.68 to 4.33% Pd are produced by investment casting process under argon atmosphere. The microstructures and mechanical properties of CoCrMo alloy were studied using X-ray diffraction, optical microscopy, scanning electron microscopy, Knoop indentation hardness tests, focusing on the influences on the different palladium additives. The measured microhardness values of CoCrMo alloys having different palladium ratio are seen to be load-dependent. The observed load dependence was rationalized using the Hays-Kendall model and it was found that the resultant load-independent hardness decreases with increase of palladium ratios. As a results, microhardness decreases with increase of palladium amount.Öğe Mechanical characterization of MgB2 thin films using nanoindentation technique(Elsevier Science Sa, 2015) Ozmetin, A. E.; Sahin, O.; Ongun, E.; Kuru, M.Mechanical properties of MgB2 thin films deposited by RF magnetron sputtering technique have been studied. MgB2 thin films were deposited approximately 300 nm on Si substrate above room temperature, and the thin films were subsequently annealed. Great care has been taken to reduce O-2 in the chamber during deposition. Structural and mechanical properties of MgB2 thin films were investigated using the Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and nanoindentation techniques. Unloading segments of nanoindentation curves analyzed using Oliver-Pharr method. Both reduced elastic modulus and nanohardness values show load dependence, i.e., indentation size effect (ISE). Proportional specimen resistance (PSR) model was used to calculate the load independent nanohardness value. Load-independent hardness value was calculated using the proportional specimen resistance (PSR) model. XRD and SEM results show that the MgB2 thin films have fine grain size. Nanoindentation results show that hardness and elastic modulus values were 11.72 GPa and 178.13 GPa, respectively. (C) 2014 Elsevier B.V. All rights reserved.Öğe Mechanical Properties of Boronized AISI 316, AISI 1040, AISI 1045 and AISI 4140 Steels(Polish Acad Sciences Inst Physics, 2009) Calik, A.; Sahin, O.; Ucar, N.In this study, some mechanical properties of borided and unborided four steels were investigated. Boronizing of steels was performed by powder pack method at 1210 K for 4 h. The hardness of borides, boride layer thickness and room temperature tensile properties were measured and it was observed that hardness and tensile properties strongly depend on chemical composition of steels. In addition, the effect of a notch on impact behavior was examined by conducting the Charpy tests on borided and unborided steels. The greatest notch toughness was found for a steel AISI 316 with a microstructure consisting of different C, Ni and Cr chemical composition compared to AISI 1040, 1045 and 4140 steels.Öğe Mechanical Properties of Nanocrystalline Tetragonal Zirconia Stabilized with CaO, MgO and Y2O3(Polish Acad Sciences Inst Physics, 2013) Sahin, O.; Demirkol, I.; Gocmez, H.; Tuncer, M.; Cetinkara, H. Ali; Guder, H. Salih; Sahin, E.The citrate gel method, similar to the polymerized complex method, was used to synthesize homogeneous tetragonal zirconia at 1000 degrees C. Nanocrystalline tetragonal phase has been fully stabilized at wide temperature range with 10 mol.% CaO, MgO, and Y2O3 addition. Scanning electron microscopy, X-ray diffraction, and microhardness tests are used to characterize synthesized materials. The grain size and dislocation density were calculated from X-ray diffraction data. The examined material exhibits indentation size effect behavior. Results revealed that the Vickers and Knoop microhardness are dependent on indentation test load. Geometrically necessary dislocation model and modified proportional resistance model are used to analyze the load dependence of the microhardness. The highest hardness values were obtained for the samples with CaO addition; however the lowest values were acquired for sample stabilized with Y2O3 by using both Knoop and Vickers techniques. This situation might be explained using the Hall-Fetch relation. DOI: 10.12693/APhysPolA.123.296Öğe Nanomechanical Behaviour and Surface Roughness of New Generation Dental Fissure Sealants(Polish Acad Sciences Inst Physics, 2016) Arslanoglu, Z.; Altan, H.; Kale, E.; Bilgic, F.; Sahin, O.The aim of this study is the comparative evaluation of surface roughness, elastic modulus and hardness values of some new generation fissure sealants using nanoindentation method and triboindenter. In this study, we have tested five different materials of dental fissure sealant in five groups with six specimens in each. Tested specimens were prepared from the following materials; Fuji Triage as a glass ionomer, Glass Seal as a glass carbomer, Ultra Seal XT Hydro, Teethmate F-1 and Defence Chroma as three resin composites. In the study, Hysitron Triboindenter TI 950 machine was used for nanohardness measurements. This machine has load resolution of less than 1 nN and displacement resolution of 0.04 nm. Data were statistically analysed using one-way analysis of variance (ANOVA) and Kolmogorov-Smirnov Z tests. Hardness values of Fuji Triage, Glass Seal, Ultra Seal XT Hydro were fairly close. Same situation was seen between Teethmate F-1 and Defence Chroma. However, hardness values of the Teethmate F-1 and Defence Chroma was lower than in other examined materials. We can also say that the Defence Chroma has the lowest elastic modulus and Fuji Triage has the highest one among the examined materials. Surface of Teethmate F-1 was the roughest. On the other hand, Ultra Seal XT Hydro has the smoothest surface.Öğe Nanomechanical Properties of Different Dental Restorative Materials(Polish Acad Sciences Inst Physics, 2016) Altan, H.; Bilgic, F.; Arslanoglu, Z.; Kale, E.; Kale, A. Koroglu; Altan, A.; Sahin, O.The aim of this study is to determine the hardness and roughness of glass ionomer cement, glass carbomer, and compomer by nanoindentation. Three different dental restorative materials: glass ionomer cement, glass carbomer cement, and compomer were used. Disc specimens (1 0 mm x 1 mm) were prepared from each material using teflon mold. All specimens were light cured according to the manufacturer's instructions. The specimens were then mounted in polyacrilic resin. After grinding and polishing the specimens were stored in distilled water at 37 degrees C for 1 day. The specimens were investigated using nanoindenter. The highest nanohardness was measured for glass ionomer cement and the lowest for glass carbomer. Regarding roughness, glass ionomer cement and compomer showed the highest mean values. Glass ionomer cement and compomer exhibited similar nanomechanical properties. Glass carbomer had superior ability to be polished up.Öğe Preparation of Fine-Grained Silicon-Nitride Ceramics and their Characterization by Depth-Sensing Indentation Tests(Polish Acad Sciences Inst Physics, 2015) Sahin, O.; Guder, H. S.; Uzun, O.; Sahin, E.; Sopicka-Lizer, M.; Gocmez, H.; Artunc, E.Both pressureless-sintered and dense, fine-grained silicon nitride ceramics were produced from mechanochemically activated nitride-based precursors. Scanning Electron Microscopy (SEM), Transmition Electron Microscopy (TEM), X-Ray Diffraction (XRD) and an ultra-low load microhardness tester were used to characterize these ceramics. Depth-sensing indentation (DSI) tests in the range of 200-1800 mN were performed on the silicon nitride ceramic to determine dynamic hardness (H-d) and reduced elastic modulus (E-r) values. These values were deduced by analyzing the unloading segments of the DSI curves. It was found that both H-d and E-r exhibits a significant indentation load dependence. Nix-Gao (NG) model was used to analyze the dynamic hardness data in the calculation of the load independent hardness value.Öğe Production and Mechanical Behaviour of Biomedical CoCrMo Alloy(Iop Publishing Ltd, 2011) Sahin, O.; Tuncdemir, A. Riza; Cetinkara, H. Ali; Guder, H. Salih; Sahin, E.Cobalt-based alloy (Co-30Cr-5.5Mo) is produced by the investment casting process. This alloy complies with the ASTM F75 standard and is widely used in the manufacturing of orthopedic implants because of its high strength, good corrosion resistance and excellent biocompatibility properties. SEM, XRD and microhardness tests are used to examine the mechanical properties of the material. The examined material exhibits the behaviour of indentation size effect (ISE). Our results reveal that Vickers and Knoop microhardness are dependent on indentation test load. The traditional Meyer's law, the proportional specimen resistance (PSR) model and the Hays-Kendall model (HK) are used to analyze the load dependence of the hardness. As a result, the Hays-Kendall model is found to be the most effective to determine the load-independent hardness H-LI of CoCrMo alloy.Öğe The role of heat treatment on the structural and nano-mechanical properties of SmCo5 thin films grown by RF magnetron sputtering technique(Elsevier Sci Ltd, 2017) Kuru, M.; Ozmetin, A. E.; Ozmetin, A.; Sahin, O.In this study, the influence of annealing temperature on structural, morphological, and nano-mechanical properties of SmCo5 thin films, which was produced by RF magnetron sputtering technique, was investigated. A set of 1 mu m thick SmCo5 thin films were grown on a Si (100) substrate at room temperature, and subsequently annealed at 400 degrees C, 500 degrees C, 600 degrees C, and 700 degrees C in an argon atmosphere. These films have a hexagonal CaCu5 structure with (110) preferential orientation corresponding to SmCo5 films observed. The Structural morphological and nano-mechanical properties of SmCo5 thin films were examined using the Grazing Incident X-ray Diffraction (GIXRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Nano indentation techniques. Results showed that the as-deposited SmCo5 thin films had a polycrystalline structure. Following the heat treatment, both crystallite and grain size increased and thin film crystallinity improved. In addition, nano-hardness and reduced elastic modulus of the SmCo5 thin films were measured with a Berkovich tip. Nano hardness and reduced elastic modulus values decrease with the increasing annealing temperature.
