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Öğe A Different Approach: Effect of Mechanical Alloying on Pack Boronizing(Springer, 2024) Albayrak, Muhammet Gokhan; Evin, ErtanSurface coating processes are carried out at high temperatures, so high heat input is applied to the material to be coated and may cause internal structure deterioration. In order to overcome this situation, the ability to reduce the coating temperature with a pretreatment such as Mechanical Activation was investigated in this study. In order to minimize the effect of alloying elements, DIN St28 steel is used. Powders containing B+SiC+KBF4 were mechanically alloyed by planetary ball milling devices to 10 and 20 h, respectively. By mixing boron-containing powder and sodium silicate, the samples were boronized at 923-1173 K temperature and 3-12 h. At the end of the mechanical alloying process, it was determined that the powder particle sizes were in the nanometer scale. According to the microstructure analysis, a single-layer Fe2B structure was successfully obtained on the samples surfaces. While no boride layers were formed on the sample surfaces at temperatures below 1023 K without MA pretreatment, boride layers were formed under these temperatures with MA pre-treatment. It has been observed that the depth of the Fe2B boride layer, which has achieved high diffusivity by creating many defects in the form of nanometer-sized crystal particles, increased with repeated fracture and cold welding of the powder particles with increasing mechanical alloying times. By calculating the activation energies of the powders, their relations with the mechanically unalloyed samples were compared and empirical formulas that could be used for similar experimental conditions were produced. The highest microhardness value was measured as 2200 HV and above.Öğe Design and Characterization of Y2O3/Pr2O3-Enriched Inconel-718 Alloys for Nuclear Applications(Taylor & Francis Inc, 2026) Albayrak, Muhammet Gokhan; Guler, Omer; Guler, Seval Hale; Evin, Ertan; Almisned, Ghada; Sen Baykal, Duygu; Tekin, Huseyin OzanThis study explores the physical, structural, and radiation shielding enhancements in Inconel 718 superalloys reinforced with 1 wt% Y2O3 and varying Pr2O3 contents from 0 to 10 wt%, respectively. X-ray diffraction analysis confirmed preservation of the face-centered cubic structure, with increasing Pr2O3 inducing peak broadening and partial amorphization. The scanning electron microscopy/energy-dispersive X-ray spectroscopy results verified the homogeneous dispersion of oxides without agglomeration. Gamma-ray shielding parameters, including the mass attenuation coefficient (MAC), half-value layer, and effective atomic number, significantly improved with higher Pr2O3 content, particularly at low to mid photon energies.The 718Y-10PO sample exhibited the lowest transmission factors and the highest MAC values across all the tested energies. Buildup factors decreased in the Pr-rich samples, confirming reduced photon scattering. Notably, the fast neutron removal cross section for 718Y-10PO as 0.15521 cm-1 exceeded the benchmark materials like graphite and B4C. These findings establish the 718Y-10PO alloy as a promising candidate for advanced nuclear shielding applications, combining structural integrity with promising gamma and neutron attenuation capabilities.Öğe Designing a novel FeCoNiMnCu high-entropy Alloy: Synthesis, structural evolution, magnetic behavior, and radiation shielding performance(Pergamon-Elsevier Science Ltd, 2026) Guler, Omer; Simsek, Telem; Simsek, Tuncay; Evin, Ertan; Sen Baykal, Duygu; ALMisned, Ghada; Tekin, H. O.In this study, a novel FeCoNiMnCu HEA was synthesized via mechanical alloying and exhibited a single-phase face-centered cubic (FCC) structure with a crystallite size of 11.7 nm and a lattice strain of 0.81 %. Magnetic characterization revealed soft ferromagnetic behavior with a saturation magnetization of 32 emu/g at 300 K, increasing to 53 emu/g at 10 K. The alloy demonstrated excellent gamma-ray attenuation, with lower half-value layer (HVL) and mean free path (MFP) values than conventional shielding materials. Notably, its fast neutron removal cross-section (Sigma R = 0.1654 cm- 1) outperformed standard materials such as B4C, graphite, and water in the fast neutron energy range. These findings underline the multifunctional performance of FeCoNiMnCu HEA, highlighting its strong potential for use in advanced nuclear reactor components and radiation shielding technologies.Öğe The effect of graphene nanoplatelets on technical properties of micro- and nano-sized TiO2 matrix: a comparative research study on electrical and optical characteristics(Springer, 2020) Güler, Ömer; Ayhan, Hakan; Başgöz, Öyküm; Başgöz, Öyküm; Yavuz, Çağdaş; Albayrak, Muhammet Gökhan; Evin, Ertan; Safa, Hasan; Ibrahim S. YahiaIn this study, titanium dioxide (TiO2)-based graphene nanoplatelets (GNPs)-reinforced composite materials were produced and the electrical and optical properties of the composite materials were investigated. Graphene, which was used as a reinforcing material, was produced by using liquid-phase exfoliation method. While the TiO2 used as matrix material was commercially available for the first group of samples, it was produced by using the sol–gel method for the second group of the samples. Different rates of graphene were added to the TiO2 powders which were commercially available and produced by using sol–gel method. GNPs used as a reinforcing material were subjected to TEM analysis. The resulting composite materials were structurally examined in SEM and XRD. Then, the changes in electrical conductivity of these composites under the impact of temperature were measured. UV–Vis spectrometers of the samples were taken and their optical properties were determined. When temperature-based electrical examination of the produced composite materials was performed, an increase was observed on the electrical conductivity values in both groups of samples as a result of addition of the reinforcing element. In addition, TiO2-containing composites produced by using sol–gel method had lower electrical conductivity comparing with commercially purchased TiO2-containing composites especially at high temperatures. In the optical measurements, it was observed that there was an increase in the optical bandgap energy range values with GNPs reinforcement but a decrease in the reflectance values.Öğe Experimental and artificial intelligence approaches to measuring the wear behavior of DIN St28 steel boronized by the box boronizing method using a mechanically alloyed powder source(Pergamon-Elsevier Science Ltd, 2023) Albayrak, Muhammet Gokhan; Evin, Ertan; Yigit, Oktay; Togacar, Mesut; Ergen, BurhanWear in moving materials in contact with each other is an inevitable cause of damage. To prevent this damage, various processes are applied to the material surfaces. The most widely used method is the surface hardening method. This study aims to examine the wear properties of the samples by forming a hard boride layer on the surface of low-carbon steel such as St28 with experimental and artificial intelligence approaches. In this context, it is aimed to obtain the boride layer at relatively low temperatures by pre-processing the powder mixture to be used as a boron source, such as Mechanical Alloying (MA). The boronizing process was carried out using the box boronizing technique. The wear behavior of the obtained samples was investigated by the block-on-disk method. In artificial intelligence approaches; The dataset is divided into three categories as 10N, 20N, and 40N. There are 39 sample types and attributes in each category. In this study, feature selection algorithms such as linear regression (LR), ridge, recursive feature elimination (RFE), f-regression, and multiple inclusion criterion (MIC) were used to select the most efficient samples. Then the best samples were classified according to their force types. Ensemble learning methods, machine learning methods, and Bayesian neural networks were used in the classification processes. Thanks to the proposed approach and feature selection algorithm, the best performance has been shown up to 10 feature selection. By ignoring 29 inefficient features, classification was performed with 10 efficient features. In the classification process, 100% overall accuracy was achieved.Öğe Synthesis and structural, electrical, optical, and gamma-ray attenuation properties of ZnO-multi-walled carbon nanotubes (MWCNT) composite separately incorporated with CdO, TiO2, and Fe2O3(Elsevier Sci Ltd, 2022) Basgoz, Oykum; Guler, Omer; Evin, Ertan; Yavuz, Cagdas; ALMisned, Ghada; Issa, Shams A. M.; Tekin, H. O.In this study, Fe2O3, TiO2, and CdO semiconductor metal oxides were separately incorporated into the ZnO-MWCNT composite at different weight percentages. Accordingly, several experimental analyses on electrical, optical, and radiation shielding characteristics of coupled semiconductor metal oxides nanocomposites were performed to determine their monotonic impact on the investigated material properties. Moreover, gamma-ray shielding properties of these novel materials were determined using MCNPX general-purpose Monte Carlo code. At 5% oxide addition, the maximum electrical conductivity was found in all groups for all temperatures. Moreover, 5% oxide reinforcement resulted in the maximum reflection characteristics in all groups. Among the CdO doped materials, the CZnOCd5 sample exhibits the highest electrical conductivity behaviour at room and high temperatures. The Eg value calculated for the CZnOCd5 sample was 3.284 eV. The CZnOCd2.5 and CZnOCd5 samples had the greatest Eg values when compared to the pure sample and the samples from other groups. The CZnOCd5 sample has the highest reflectance value in the CZnOCd group's reflectance graph. On the other hand, the maximum gamma-ray attenuation properties were reported for CZnOCd5 sample. Among the analysed samples, the CZnOCd5 sample's characteristics provide a preliminary motivation for a more comprehensive analysis of this material and assessment of potential radiation protection applications.Öğe The synergistic effect of CNTs-polymeric surfactant on the properties of concrete nanocomposites: Comparative study(Sage Publications Ltd, 2021) Guler, Omer; Cacim, Nazli N.; Evin, Ertan; Yahia, Ibrahim S.Carbon nanotubes (CNTs) have been used as reinforcing material for many different matrices. There are many studies in the literature reporting that reinforcement of CNTs into concrete matrix improved the properties of the concrete. In this study, first unmodified CNTs were reinforced to concrete and it was seen that there were partial decreases in strength despite the increasing rate of CNTs. Thereon, the surfaces of CNTs to be used as reinforcing material were modified with water-soluble surfactants (Polyvinyl alcohol-PVA, Polyvinylpyrrolidone-PVP, Poly (ethylene glycol)-PEG, Dodecylamine-DDA) and reinforced with concrete. In previous studies, many different surfactants were tried to functionalise the surfaces of CNTs. However, in this study, water-soluble polymeric surfactants were preferred without the need for an additional process in order to modify the surfaces of CNTs. In addition, the effect of the surfactants used on the mechanical properties of concrete was examined comparatively. Although the amount of CNTs reinforcement is very low like 0.05 wt%, the increase in strength was seen to be above 60%. The highest strength values were obtained in the sample in which PVA was used as surfactant. Through the surfactants used, bundles of CNTs were fully opened and distributed homogeneously into the concrete matrix, and all of the CNTs were embedded into the matrix by getting wet by the matrix. In the real application, it will be possible to use new generation concretes with higher strength and lighter weight by providing the ease of reinforcing CNTs to the concrete matrix.
