Browsing by Author "Ada H."

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Characterization of the CoFe2O4/Cu displacement effect in the Y123 superconductor matrix on critical properties
(2020-11-01) Safran S.; Bulut F.; Nefrow A.R.A.; Ada H.; Ozturk O.
In this study, CoFe2O4 (x = 0, 5, 10 and 20 wt%) doped YBa2Cu3−x(CoFe2O4)xO7−δ bulk samples were produced using solid state reaction (SSR) method and sol–gel(SG) methods. Oxide-form and acetate-form powders were preferred for SSR method and SG method, respectively. The heat treatment of the produced samples was carried out in two stages. Firstly, the samples were annealed at 950 °C for 24 h, after which they were kept in oxygen at 500 °C for 5 h and allowed to be cooled down to room temperature. Characterization of all samples was performed using methods such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, temperature-dependent resistance measurement (R–T) and Vickers microhardness analysis. Superconducting behavior was observed in all the produced samples, but as a result of the addition, a decrease was observed with the increase of the doping ratio at the critical transition temperature. As a result of the characterization, it is concluded that the doping ions can be replaced with Cu atoms in Y123 structure. In addition, doping led to significant changes in Vickers microhardness results.
Comparison of the effects of b4C and SiC Reinforcement in Al-Si Matrix Alloys Produced via PM Method
(2019-01-01) Kaplan Y.; Tan E.; Ada H.; Aksöz S.
Reinforcement kind and ratios have significant effects on the metal matrix composite (MMC) materials. In this study, two different (B4C and SiC) reinforcement compounds between 5 and 15 wt% reinforcement ratios were used in Al-Si main matrix composite materials. Samples were produced via powder metallurgy (PM) method and were subjected to metallographic investigation with; SEM, EDS, FASTMAP, Optical Microscope analyzing methods. Microvickers measurements were carried out as HV1 load. The effects of B4C and SiC reinforcement in MMC were compared in details with these investigations.
Comparison of Vickers microhardness of undoped and Ru doped BSCCO glass ceramic materials
(2018-03-01) Ozturk O.; Asikuzun E.; Tasci A.; Gokcen T.; Ada H.; Koralay H.; Cavdar S.
In this study, effect of substitution ratio on the mechanical and structural properties of Bi1−xRuxPb0.2Sr2CaCu2O10+δ system, that is prepared in the ratios of x = 0.0, 0.025, 0.050, 0.075, is investigated. Samples are prepared with glass ceramic method and sintered at 845 °C. XRD and SEM measurements are performed for structural analyses, and Vickers micro-hardness measurements are carried out at different applied load (0.245 ≤ F ≤ 2.940 N) in order to investigate the mechanical performance of the Ru doped Bi1−xRuxPb0.2Sr2CaCu2O10+δ system. Experimental results of Vickers micro-hardness analyses are performed using the Meyer’s law, the proportional samples resistance model, the elastic/plastic deformation model, the Hays–Kendall approach and the indentation induced cracking (IIC) model. All analyses results are exhibited reverse indentation size effect behavior. The measured hardness values increase with increasing the applied load. Finally, IIC model is determined as the most successful model describing the mechanical properties of our samples.
Effect of Co/Cu partial replacement on fundamental features of Y-123 ceramics
(2020-05-01) Ozturk O.; Nefrow A.R.A.; Bulut F.; Ada H.; Turkoz M.B.; Yildirim G.
This study is liable for the effect of sample production processes including the standard solid-state reaction (SSR) and classical sol–gel (SG) preparation methods on the fundamental characteristic features, namely electrical, superconducting, crystal structure quality, crystallinity, morphological, strength quality of grain boundary couplings, and interaction between the grains of YBa2Cu3−xCoxO7−δ (Y-123) advanced ceramic compounds within the weight ratio intervals x = 0–20%. The main heat treatments are exerted at two main steps: (I) annealing at 950 °C for 24 h in air medium conditions and (II) annealing at 500 °C during 5 h under the oxygen annealing ambient. The standard measurement methods such as powder X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, temperature-dependent electrical resistance, and Vickers hardness measurements are performed for the characterization of materials. It is found that the samples prepared at SSR route present much more superior characteristic features as compared to those fabricated at SG technique, being one of the most striking points deduced this work. In more detail, every material prepared crystallizes in the orthorhombic symmetry and exhibits the superconducting nature but considerable decrement in the critical transition temperatures. The onset and offset transition temperatures are noted to decrease regularly from 92.96 K (92.28 K) to 90.20 K (83.59 K); and 90.05 K (90.03 K) to 45.97 K (30.49 K) for the materials prepared by the SSR (SG) route. Similarly, the variation in the lattice cell and average grain size parameters confirm that the Co/Cu substitution damages Y-123 superconducting phase. Additionally, the Co/Cu partial replacement mechanism leads to increase significantly the Vickers hardness results. To sum up, the Co/Cu partial substitution (produced by either SSR or SG method) is plowed to improve the fundamental characteristic features for new, novel, and feasible market application areas of Y-123 cuprate ceramics in the universe economy.
Investigation of microhardness properties of the multi-walled carbon nanotube additive MgB2 structure by using the vickers method
(2021-06-01) Kaya N.; Çavdar Ş.; Öztürk Ö.; Ada H.; Koralay H.
In this study, the effect of multi-walled carbon nanotube doping to MgB2 compound on microhardness properties of MgB2 was investigated by using solid-state reaction method. The amount of multi-walled carbon nanotubes was chosen as 0, 1, 2, 3 and 4% by weight of total MgB2. All samples were obtained by sintered at 650 °C temperatures. The microhardness properties of the samples obtained were examined using the Vickers method. At the same time, the samples obtained were analyzed according to Meyer's Law, proportional sample resistance (PSR) model, Hays-Kendall (HK) approach and elastic/plastic deformation (EPD) model. Samples were found to exhibit indentation size effect (ISE) behavior. It was understood that the multi-walled carbon nanotubes doped to the samples made MgB2 softer by reducing the intergranular bonding of the MgB2 structure. In addition, it was found that the force applied to the samples caused both plastic and elastic deformation on the samples.
Investigation of QStE 420 TM steel materials weldability using different basic electrodes by electric arc welding method
(2022-01-01) Harman M.; Ada H.; Çetinkaya C.
QStE 420 TM quality steel sheet plate materials, which are widely used in sectors such as defense industry and automotive industry, are made of fine-grained and micro-alloyed structure and are joined separately using the shielded metal arc welding method with the help of basic type rod electrodes with 3 different chemical compositions (E11018-G H4, E7018-1 H4R and E7018 H8 AWS coded). Mechanical and metallurgical effects on the welding zone (base material, heat-affected zone and weld metal) formed after the melting of electrodes with different chemical compositions in specified parameters; the samples were examined by applying macrostructure and microstructure examinations, as well as mechanical tests by applying tensile, bending, notch impact and hardness tests. As a result of the tests, the mechanical and metallurgical effects occurring in the weld zone were investigated by performing macro-micro structure examinations and applying tensile, bending, notch impact and hardness tests. In these tests, the fulfillment of the expected mechanical and metallurgical properties of the welded joints obtained from the basic electrodes of different compositions was examined in terms of weldability. Based on the comparative test results, the most appropriate results are; It was obtained from test samples that were combined in 4 passes with the electrode coded E7018 H8, at an average current intensity of 190 A, an arc voltage of 33 V and an average welding speed of 2.93 mm/second.
Optimization of maximum tensile strength of welded joints of API 5L X65 pipes by Taguchi method
(2019-03-01) Ada H.; Cetinkaya C.
In this study, the joint performance of API 5L X65 steel pipes welded using shielded metal arc welding method was examined using the Taguchi method. As performance indicators, strength of current, welding direction, and electrode type were considered as input parameters, and the maximum tensile strength of the welded samples was considered as the output parameter. The optimum input parameters were determined to be 'cellulosic electrode,' 'upward direction,' and '150-180 Ampere range strength of current'. In the optimization process, it was observed that the difference between the maximum tensile strength results obtained from the experiments and the estimated results was insignificant. Thus, it is assumed that this difference can be neglected. Consequently, we concluded that Taguchi optimization can be applied successfully to the estimation of maximum tensile strength.
Production of the aa2196-tib2 MMCs via PM Technology
(2019-01-01) Tan E.; Kaplan Y.; Ada H.; Aksöz S.
In this study, metal matrix composite (MMC) materials were produced via powder metallurgy (PM) technology. Main matrix was obtained with AA2196 (Al-Li Alloy) and TiB2 was used as reinforcement materials. In study; TiB2 reinforcements ratio were chosen between 5 and 15%wt. The metallographic investigation was realized with; SEM, EDS, FASTMAP, Optical Microscope analyzing techniques. Hardness values were obtained with HV1. In the study, the reinforcements could be distributed in main matrix homogeneously, via PM technique. The MMCs hardness values increased with the edition of TiB2 reinforcement.
The effect of aging processes on tribo-metallurgy properties of al based ternary alloys product by p/m technique
(2020-01-01) Kaplan Y.; Aksöz S.; Ada H.; İnce E.; Özsoy S.
In this study, Al matrix composites consisting of different amounts of Zn, Cu, and Mg were produced using the powder metallurgy technique. In the alloying, powders were ball milled for 120 min via mechanical alloying. After alloying process, the powders were pressed at 800 MPa at room temperature. Sintering (2 h at 600 °C in argon atmosphere), solution treatment (2 h at 480 °C), and aging processes (3, 6, 9, and 12 h, respectively, at 120 °C) were applied to the samples. The hardness and tribo-metallurgy properties of the products were investigated. After sintering, the hardness values of the three alloys were close to each other; however, the solution treatment after sintering caused the hardness values to increase significantly. It was determined that the Al-2Zn-5Cu-4Mg alloy had the highest hardness increase with the 6-h aging heat treatment. The wear resistance of the materials in all the compositions had increased. The highest wear resistance and lowest friction coefficient were obtained for the Al-2Zn-5Cu-4Mg alloy with the 6-h aging heat treatment.