Güler, Ömer; Güler, Seval Hale; Yayla, Nihal; Baykal, Duygu Sen; Durmus, Hasan; Tekin, Huseyin Ozan; ALMisned, Ghada

This study investigates the structural, microstructural, surface-chemical, and radiation attenuation behaviour of high-entropy rare-earth oxide (HEO) powder compositions synthesized as TBC-related candidate coating materials, whose radiation attenuation potential was assessed within a computational Inconel-718-based sandwich model. Four compositions, namely (GdErSmEuYb)2Hf2O7, (GdErSmEuYb)2Ce2O7, (GdErSmEuYb)2Zr2O7, and (GdErSmEuYb)2Si2O7, were synthesized via high-energy ball milling followed by calcination at 1200 °C. X-ray diffraction results revealed the formation of distinct crystal structures depending on B-site chemistry, including defective fluorite and silicate-type phases. SEM-EDS mapping confirmed homogeneous elemental distribution, while XPS analysis demonstrated mixed valence states and different oxygen vacancy concentrations across the compositions. To evaluate radiation attenuation performance, a sandwich-type geometry consisting of a 10 mm Inconel-718 core with symmetrically defined simulated HEO layers was modelled using Monte Carlo simulations. Gamma-ray transmission was analyzed over an energy range of 0.276-1.332 MeV, and fast neutron attenuation was assessed at 4.5 MeV. The results showed that transmission factors decreased with increasing coating thickness, with the effect being more pronounced at lower photon energies. Among the investigated compositions, the Hf-based system exhibited the most favorable predicted attenuation response for both gamma rays and fast neutrons under the defined simulation conditions. Theoretical half-value layer calculations also showed good agreement with the simulation results. Overall, the findings indicate that high-entropy rare-earth oxide coatings may provide an additional radiation attenuation contribution when incorporated as layers in Inconel-718-based systems. However, since direct thermal-barrier properties such as thermal conductivity, thermal diffusivity, thermal cycling resistance, and thermal-stress behavior were not evaluated in the present work, the present study should be interpreted as a structural and radiation-transport assessment of TBC-related coating candidates rather than a direct demonstration of thermal-barrier performance.

İncele

Albayrak, Muhammet Gökhan; Güler, Ömer; Güler, Seval Hale; Evin, Ertan; ALMisned, Ghada; Sen Baykal, Duygu; Alkarrani, Hessa; Susoy, Gulfem; Kilic, Gokhan; Tekin, Hüseyin Ozan

This 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.

İncele

Güler, Ömer; Güler, Seval Hale; Özkul, İskender; ALMisned, Ghada; Baykal, Duygu Sen; Tekin, Huseyin Ozan

This study represents an initial investigation toward exploring the multifunctional potential of the (ErSmGdYPr)2Hf2O7 high-entropy oxide as a thermal barrier coating (TBC) material in radiation environments. Therefore, the evaluated parameters should be considered as a preliminary step rather than a complete representation of the material’s overall performance in such complex applications. In this context, (ErSmGdYPr)₂Hf2O7 powders were synthesized through high-energy ball milling of commercial rare-earth oxide precursors followed by calcination at different temperatures. Structural evolution during synthesis was investigated using X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, and thermal analysis techniques. The results confirmed the formation of a defective fluorite-type high-entropy oxide structure after calcination at elevated temperatures, accompanied by homogeneous elemental distribution and stable ceramic microstructures. In addition to structural characterization, the radiation interaction behaviour of the synthesized material was evaluated through gamma-ray attenuation parameters and fast neutron removal cross-section analysis. The obtained results indicate that the presence of multiple rare-earth elements provides favorable interaction characteristics with both photons and fast neutrons. These findings highlight the potential of this high-entropy oxide as a precursor for multifunctional coating materials. However, it should be noted that this work represents a preliminary powder-level investigation, and further research on actual coating deposition and thermal testing is required to validate its service performance.

İncele

Özkul, İskender; Kalay, Ece; Güler, Seval Hale; Karaduman, Oktay; Şimşek, Telem; Bülbül, Zeynel Abidin; Aksu Canbay, Canan; Sen Baykal, Duygu; ALMisned, Ghada; Tekin, H.O.

Rare-earth substitution provides a route for tailoring the structural, magnetic, and gamma-ray attenuation behaviour of Ho-based Co-Mn double perovskites; however, the combined effects of rare-earth ionic size, magnetic character, and substitution level remain insufficiently understood. In this study, Ho1.5La0.5CoMnO6, Ho1.2Er0.8CoMnO6, Ho1.3Sm0.7CoMnO6, and Ho2CoMnO6 were synthesized through a two-step route involving mechanical alloying to obtain precursor powders, followed by annealing at 1000 °C in air to promote oxidation and double-perovskite phase formation. Their structural, thermal, surface-chemical, magnetic, and gamma-ray attenuation properties were examined by X-ray diffraction, thermal analysis, X-ray photoelectron spectroscopy, SEM-EDS, vibrating-sample magnetometry, and theoretical shielding calculations based on half-value layer (HVL) and transmission factor (TF) parameters. The XRD patterns were consistent with predominantly monoclinic P21/n type double-perovskite structures, while weak additional reflections suggested possible minor secondary phases. SEM-EDS showed homogeneous elemental distributions, and XPS analysis indicated Co2+ dominated and mixed Mn-valence characteristics in the spectra where reliable component analysis was possible. All compositions exhibited a low-temperature ferromagnetic-like field response but did not reach magnetic saturation at 3 T. Ho2CoMnO6 and Ho1.3Sm0.7CoMnO6 showed the highest field-dependent magnetization values at 10 K, whereas Ho1.2Er0.8CoMnO6 displayed the lowest response. The theoretical gamma-ray attenuation calculations showed clear composition-dependent differences. At 0.662 MeV, the HVL values were 1.0650, 0.9972, 1.0438, and 0.9967 cm for Ho1.5La0.5CoMnO6, Ho1.2Er0.8CoMnO6, Ho1.3Sm0.7CoMnO6, and Ho2CoMnO6, respectively. At the same photon energy and a thickness of 1.0 cm, the corresponding TF values were 0.0896, 0.0858, 0.0882, and 0.0860. Thus, Ho1.2Er0.8CoMnO6 and Ho2CoMnO6 exhibited the lowest HVL and TF values among the investigated compositions. The shielding calculations identified Ho1.2Er0.8CoMnO6 and Ho2CoMnO6 as the most effective attenuators, with lower HVL and TF values across the investigated energy range. These results show that rare-earth substitution enables compositional tuning of magnetic and theoretical gamma-ray attenuation behaviour, with the observed trends reflecting the combined influence of rare-earth ionic size, magnetic character, substitution level, and valence-state complexity.

İncele

Özkul, İskender; Güler, Ömer; Kavaz, E.; Kalay, Ece; Güler, Seval Hale; ALMisned, Ghada; Tekin, H.O.

This study investigates three newly designed Ti-Zr-Hf-based high-entropy alloys such as TiZrHfGdSm (N1), TiZrHfEr (N2), and TiZrHfGdEuB (N3), with the aim of understanding how selected rare-earth and boron additions influence microstructural evolution and dual γ-ray/fast-neutron shielding performance. All alloys were synthesized by arc melting and evaluated through thermodynamic modelling, X-ray diffraction, scanning electron microscopy with elemental mapping, and mixed-field attenuation measurements. The results show that each composition forms an HCP-type solid-solution matrix with composition-dependent lattice distortion and secondary phase formation. Among the studied systems, the Er-modified alloy N2 develops the most spatially uniform elemental distribution and demonstrates the most balanced combination of γ-ray attenuation, effective atomic number, buildup behaviour, and fast-neutron removal efficiency. N1 and N3, containing multiple rare-earth elements and, in the case of N3, boron-induced borides, exhibit distinct grain features and provide valuable insights into how multi-element additions shape photon and neutron interaction pathways. Comparative examination confirms that shielding performance in these HEAs is governed by the interplay of elemental cross sections, density, and microstructural uniformity. The findings highlight Ti-Zr-Hf-RE(B) alloys as promising platforms for multifunctional radiation-shielding materials and provide a compositional framework for future optimization in nuclear, medical, and aerospace applications.

AtıfScopus2·OpenAlex2

İncele

Kanca, Muhammed Sait; Yılmaz, Demet; Tasgın, Yahya; Kök, Mediha; Güler, Seval Hale

In this study, the effects of rare earth oxides (Gd₂O₃, La₂O₃, Eu₂O₃, Pr₂O₃, Dy₂O₃, and Y₂O₃) and high-entropy oxide (GdLaEuPrDyY)₂O₃ additives on the structural, mechanical, and radiation shielding properties of copper matrix composites were investigated. XRD and SEM-EDS analyses showed that the high-entropy oxide successfully formed in a single-phase bixbyite structure after mechanical alloying and was homogeneously distributed within the copper matrix. The rare earth oxide additive significantly reduced the crystal grain size of the Cu matrix and improved its mechanical properties. Specifically, the microhardness value reached 68.3 Hv in the composite with 20% high-entropy oxide additive, representing an increase of approximately 111% compared to pure copper (32.3 Hv). Gamma shielding results showed that the rare earth oxide additive significantly increased the photon attenuation capacity. Specifically, at 242 keV energy, the Dy₂O₃ additive increased the MAC value from 0.141 cm²/g to 0.246 cm²/g, providing a 74.5% improvement. The most important result is that the composite with 20% high-entropy oxide additive showed the highest shielding performance, achieving a MAC value of 0.278 cm²/g, which is significantly superior to pure copper. Furthermore, this composite exhibited the lowest HVL and MFP values, demonstrating the highest photon shielding efficiency. Neutron shielding analyses revealed that Gd₂O₃ and high-entropy oxide additives, in particular, increased thermal neutron attenuation performance to approximately 100%. These results demonstrate that high-entropy oxide additives provide a stronger impact compared to single oxide additives, offering superior performance in both gamma and neutron shielding. Consequently, copper composites doped with (GdLaEuPrDyY)₂O₃ stand out as promising alternative shielding materials for nuclear facilities, radiation protection systems, and advanced engineering applications due to their high shielding efficiency, improved mechanical properties, and non-toxic composition.

AtıfScopus1·OpenAlex1

İncele

Kuluöztürk, Zehra Nur; Kuluöztürk, Muhammed Fatih; Güler, Seval Hale; Doğru, Mahmut; Güler, Ömer

Refractory High Entropy Alloys (RHEAs) have become an attractive alternative for radiation shielding applications due to their high mechanical strength, thermal resistance, structural stability, and compositional diversity. In this study, Cu-based composites containing 0–20 wt% RHEAs were prepared, and the crystal structure, morphological properties, and radiation shielding performance of the synthesized Cu-RHEA were investigated experimentally and theoretically. Measurements were performed using a NaI(Tl) detector system with point sources of 133Ba, 137Cs, 22Na and 60Co emitting gamma energies in the range of 0.356–1.333 MeV. In addition, theoretical calculations were carried out using the FLUKA and Phy-X/PSD, showing good agreement with the experimental data. Linear attenuation coefficient (LAC) values were found to decrease with increasing photon energy and to increase with increasing RHEA content. In the 0.356–1.333 MeV energy range, the experimental LAC values ranged from 0.7599 to 0.3818 cm−1 for Cu-RHEA0 and from 0.9594 to 0.4221 cm−1 for Cu-RHEA20. At 0.662 MeV, the LAC value increased from 0.5426 cm−1 for Cu-RHEA0 to 0.6183 cm−1 for Cu-RHEA20. In terms of half-value layer (HVL), the Cu-RHEA20 sample exhibited a value of 0.729 cm at 0.356 MeV, approximately 20% lower than the 0.912 cm value of Cu-RHEA0. Compared with conventional shielding materials reported in the literature, the Cu-RHEA20 sample reached a maximum mass attenuation coefficient (MAC) of 76.279 cm2⋅g−1 at 0.015 MeV, demonstrating clear superiority over ordinary concrete with a value of 7.079 cm2⋅g−1. These findings demonstrate that increasing RHEA content improves gamma-ray attenuation performance, highlighting Cu-RHEA20 as a promising next-generation shielding material.

İncele

Güler, Ömer; Güler, Seval Hale; Özkul, İskender; ALMisned, Ghada; Sen Baykal, Duygu; Tekin, H.O.

Spinel high-entropy oxides (HEOs) can stabilize multiple transition-metal cations within a single lattice, yet their radiation-interaction behavior is scarcely explored. Here, a (FeNiCoCrMn)3O4 spinel HEO was produced via an alloy-to-oxide route: 40 h mechanical alloying of equiatomic FeNiCoCrMn powders followed by mechano-oxidation (1000 °C/3 h) and high-energy grinding. HEA-derived thermodynamic metrics were used to rationalize the stability of the equiatomic metallic precursor prior to mechano-oxidation, rather than to directly predict the formation of the final oxide phase. XRD evidenced progressive amorphization of the HEA and its conversion to a crystalline spinel oxide, while SEM–EDS confirmed homogeneous elemental distribution. XPS indicated a defect-rich, multivalent surface (Co2+/Co3+, Cr3+/Cr6+, Fe3+, mixed Mn states, Ni2+) with lattice oxygen and vacancy-related components. Moreover, the spinel oxide showed higher linear attenuation coefficients than 316L stainless steel, Inconel-718, and several lightweight Al-based entropy alloys, yielding lower HVL values, especially at low energies. Zeff exhibited the expected energy dependence and exceeded Al-dominant alloys across the spectrum. EBF/EABF at 1 and 40 mfp displayed Compton-region peaks and strong depth effects, consistent with attenuation behavior. It can be concluded that a (FeNiCoCrMn)3O4 spinel high-entropy oxide, produced via an alloy-to-oxide transformation route, exhibits structurally stable and compositionally homogeneous characteristics together with favorable gamma-ray attenuation behavior.

İncele

Durmus, Hasan; Özkul, İskender; Güler, Ömer; Güler, Seval Hale; Baykal, Duygu Sen; ALMisned, Ghada; Tekin, H.O.

In this study, a novel high-entropy rare-earth tungstate, (PrEuYLaSm)2(WO4)3, was synthesized by high-energy ball milling followed by calcination, and its structural, microstructural, thermal, gamma-ray, and neutron shielding properties were systematically investigated. X-ray diffraction results revealed that ball milling induced partial amorphization of the initial oxide mixture, while calcination at 1100 °C promoted the formation of a single-phase monoclinic A2W3O12-type structure without detectable secondary phases. SEM-EDS mapping showed the homogeneous distribution of Pr, Eu, Y, La, Sm, W, and O throughout the synthesized material. Differential thermal analysis showed sequential desorption, crystallization, and structural ordering processes, together with the absence of sharp decomposition up to 1100 °C, indicating good thermal stability. Radiation shielding evaluation demonstrated that the synthesized high-entropy tungstate exhibited strong gamma-ray attenuation performance, with high mass attenuation coefficient values, low half-value layer values, and stable effective atomic number behaviour over a wide photon energy range. Although some individual oxides showed superior performance at specific energies, the high-entropy composition provided a more balanced shielding response overall. In neutron shielding, the material showed competitive fast neutron removal capability among oxide systems. It can be concluded that the multifunctional potential of (PrEuYLaSm)2(WO4)3 for competitive high-temperature and radiation shielding applications.

İncele

Güler, Ömer; Yılmaz, Demet; Kanca, M. Sait; Kök, Mediha; Güler, Seval Hale; Taşgın, Yahya

This study investigates the structural, thermal, and radiation shielding properties of (Er0.2Yb0.2Sm0.2La0.2Eu0.2)2Zr2O7 high entropy oxide (HEO) reinforced tin (Sn) matrix composites. In the first stage of the study, HEO powders were synthesized by grinding at 350 rpm for 30 h using a solid-state method with mechanical alloying assistance, and then calcining at 1100 °C for 8 h. In the second stage, composites were produced by mixing HEO-reinforced Sn matrix materials containing 1%, 5%, and 10% reinforcement, pelleting them under 200 MPa pressure, and then sintering them at 300 °C for 3 h. In the first stage of the study, (Er0.2Yb0.2Sm0.2La0.2Eu0.2)2Zr2O7 HEO powders were synthesized using a mechanical alloying-assisted solid-state route. In the second stage, HEO-reinforced Sn matrix composites containing 1 wt%, 5 wt%, and 10 wt% reinforcement were produced. The phase formation and crystallographic structure of the synthesized powders and composites were characterized using X-ray diffraction. Thermal behavior and phase stability were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermal analysis results revealed dehydration and structural stabilization processes at intermediate temperatures, while crystallization of the HEO phase was observed at elevated temperatures. In addition, oxidation behavior of the Sn matrix composites was evaluated, showing that the presence of HEO particles significantly suppresses mass gain during high-temperature oxidation, indicating improved thermal stability. Finally, the radiation shielding performance of the samples was experimentally evaluated within the photon energy range of 59.54–609.2 keV using Am-241, Ba-133, and Ra-226 radioactive sources together with a Ultra-Low Energy Germanium (ULEGe) detector. The results demonstrate that the incorporation of HEO particles leads to minor, energy-dependent variations in the radiation attenuation capability of the tin matrix, influenced by the presence of high atomic number rare-earth elements and modified microstructural characteristics. The gamma radiation protection coefficient (RPC) values indicate strong attenuation in the low photon energy region, decreasing to approximately 16–19% at 609.3 keV. Moreover, the measured neutron equivalent dose rates increase from 0.054 µSv/h for pure Sn to 0.285 µSv/h for the Sn–10%HEO composite, indicating that HEO incorporation modifies the neutron interaction behavior of the Sn matrix composites.

İncele

Güler, Ömer; Güler, Seval Hale; Özkul, İskender; Baykal, Duygu Sen; Tekin, H.O.; ALMisned, Ghada

A spinel-structured high-entropy alloy-oxide (HEAO) with the nominal composition (Fe30Cr30Mn20Ni10V10)3O4 was synthesized via mechanical alloying followed by thermo-mechanical oxidation X-ray diffraction indicated the formation of a predominantly spinel-type cubic oxide phase after oxidation, with the observed reflections being consistent with the Fd-3m spinel structure, while SEM-EDS mapping showed a homogeneous cation distribution at the examined scale. XPS analysis revealed mixed valence states of Fe2+/Fe3+, Cr3+/Cr4+, Mn3+/Mn4+, Ni2+/Ni3+, and V4+/V5+. Thermodynamic parameters supported phase stability, with ΔSmix = 12.51 J K−1·mol−1 and Ω = 2.68. Gamma-ray attenuation properties were evaluated over 0.015-15 MeV. The linear attenuation coefficient decreased from 193.685 cm−1 at 0.015 MeV to 0.309 cm−1 at 1 MeV and stabilized near 0.137 cm−1 at 15 MeV. Correspondingly, the half value layer increased from 0.004 cm to 5.068 cm across the same energy range. The effective atomic number decreased from 24.58 at 0.015 MeV to approximately 15.37 at 1 MeV, followed by a moderate increase to 17.71 at 15 MeV. Comparative analysis with commercial stainless steel, titanium alloys, nickel-based superalloys, ferro-boron systems, and lightweight entropy alloys demonstrated that the synthesized HEAO exhibits intermediate yet stable attenuation performance, positioning it between low-density Al-based systems and high-density Ni-rich alloys. It can be concluded that the alloy-to-oxide strategy enables the production of a structurally stable spinel HEAO with consistent and competitive gamma-ray attenuation behaviour across a broad photon energy spectrum.

AtıfScopus1·OpenAlex1

İncele

Güler, Seval Hale

In this study, high entropy FeCoNiMnMoV and FeCoNiMn (Ferro Mo-Ferro-V) alloys were produced by arc melting method. After the arc melting process, the samples were annealed at 1000ᵒC under argon atmosphere for 15 hours physical and thermodynamic calculations were performed to determine the properties of the alloy. In the study, both alloys were characterized. For characterization, XRD, SEM, EDS and Micro hardness were taken from the samples. The aim of my study is to examine the effect of using low-priced starting materials on the microstructure of HEA. For this purpose, ferro-alloys were added to the alloy. As a result, similar properties were obtained for the microstructure of both alloys. However, it has been determined that the hardness of samples containing ferro-alloys decreases more due to their chemical composition, especially after heat treatment.

AtıfOpenAlex3

İncele

Güler, Seval Hale; Güler, Ömer; Kavaz, E.; ALMisned, Ghada; Albayrak, M. Gökhan; Issa, Bashar; Tekin, H.O.

We report a comprehensive investigation on customization process of Oxide Dispersion-Strengthened alloys through Sm2O3, Pr2O3, and Er2O3 incorporation into 316L stainless steel matrix in terms of a desired enhancement in structural, physical, and nuclear radiation shielding properties. Oxide powders are incorporated into 316L stainless steel powder all with the same purity of 99.5%. These were Erbium oxide (Er2O3), Praseodymium oxide (Pr2O3), and Samarium oxide (Sm2O3). First, X-Ray diffraction and Scanning Electron Microscope/Energy-dispersive X-ray spectroscopy analyses are conducted in order to investigate their physical and structural properties. Next, two different experimental setups are employed using a133Ba and 241Am/Be sources for the measurements of gamma-ray and neutron transmission properties of Oxide Dispersion-Strengthened alloys. The maximum density increment is achieved through Er2O3 compared to other reinforced oxides. The detector counting value reached its minimum level when a 5% Er2O3 oxide dispersion was introduced into the 316L SS matrix. Similarly, the most significant degree of photon absorption, the highest values of mass attenuation coefficient, lowest half value layer, and most effective atomic number, were all attained by the same sample. Based on the findings derived from the investigation, it can be concluded that incorporating Er2O3 oxide into 316L steel can be considered as a viable option in terms of enhancing the critical properties of Oxide Dispersion-Strengthened alloys for extreme conditions such as nuclear reactors and other similar fields, where the behavioral attributes of the utilized materials are at utmost importance.

AtıfScopus22·OpenAlex25

İncele

Karaduman, Oktay; Özkul, İskender; Güler, Seval Hale; Aksu Canbay, Canan

In this study, two high-temperature shape memory alloys (HTSMAs) of CuAlV with unprecedented chemical compositions were fabricated using the arc melting technique, followed by traditional ice-brine water quenching after the melting process. To characterize the shape memory properties and structure of the alloys, a series of tests including differential calorimetry (DSC and DTA), EDS, optical microscopy, and XRD were conducted. The DSC tests, performed at different heating and cooling rates, demonstrated highly stable reversible martensitic phase transformation peaks at high temperatures, which were also confirmed by the results of DTA tests. Microstructural XRD and optical microscopy tests were conducted at room temperature, revealing the martensitic structure of the alloys in both cases. Based on all the results, the effects of different minor amounts of vanadium additives directly on the CuAlV alloy were discussed.

AtıfScopus2·WoS2·OpenAlex3

İncele

Güler, Ömer; Boyrazlı, Mustafa; Albayrak, Muhammet Gökhan; Güler, Seval Hale; Ishihara, Tatsumi; Edalati, Kaveh

One of the most promising solutions to slow down CO2 emissions is the use of photocatalysis to produce hydrogen as a clean fuel. However, the efficiency of the photocatalysts is not at the desired level, and they usually need precious metal co-catalysts for reactions. In this study, to achieve efficient photocatalytic hydrogen production, a high-entropy oxide was synthesized by a mechano-thermal method. The synthesized high-entropy oxide had a bandgap of 2.45 eV, which coincided with both UV and visible light regions. The material could successfully produce hydrogen from water under light, but the main difference to conventional photocatalysts was that the photocatalysis proceeded without a co-catalyst addition. Hydrogen production increased with increasing time, and at the end of the 3 h period, 134.76 µmol/m2 h of hydrogen was produced. These findings not only introduce a new method for producing high-entropy photocatalysts but also confirm the high potential of high-entropy photocatalysts for hydrogen production without the need for precious metal co-catalysts.

AtıfScopus33·WoS30

İncele

Simsek, Tuncay; Kurtulus, Altug; Avar, Baris; Güler, Seval Hale; Dag, İlker Emin; Chattopadhyay, Arun K.

This study focuses on synthesizing and characterizing mechanically alloyed refractory high entropy alloys (RHEA) containing TiMoNb, Cr, W, and Cr + W. Analytical techniques including XRD, SEM, EDX, DTA, and TGA were employed to explore the influence of Cr and W on the alloys' structure, morphology, and thermal stability towards oxidation. XRD analysis confirmed the formation of a single-phase bcc solid solution in TiMoNbCr, TiMoNbW, and TiMoNbCrW alloys. Crystallite size decreased as milling progressed, yielding average sizes of approximately 7.2 nm, 7.4 nm, and 9.7 nm, with lattice strains of 1.143%, 1.148%, and 1.15%, respectively. Both experimental and calculated values of lattice parameters converged to around 3.1685 ± 0.002 and 3.1791 ± 0.010 Å for all three alloys. The synergy of Cr and W in TiMoNb was observed for the first time, impacting dislocation density, hardness, and oxidation stability. TiMoNbCrW exhibited reduced dislocation density and the highest hardness (502 HV). TGA indicated enhanced oxidation resistance up to 400 °C for TiMoNbCrW compared to the most vulnerable TiMoNbCr alloy.

AtıfScopus2·OpenAlex2

İncele

Güler, Seval Hale; Safa, Hasan

In this study, BNNSs were synthesized via liquid-phase exfoliation method. Hexagonal boron nitride powders were used as the starting material. The production of boron nitride nanosheets was optimized. For this purpose, different sonication parameters and the effects of different solvents have been investigated. Different sonication power and time parameters of the homogenizer (Sonics Vibra-cell VCX, 750 W) used as the sonication parameter have been changed. In this stage, they were subjected to sonication process first for 1-1.5-2 hours at 25% sonication power, 1-1.5-2-4 hours at 50% sonication power, and 1-1.5-2-4-6-8 hours at 75% sonication power. As a result of particle size analysis, time/sonication power parameters were determined as 2 h-75%, 2 h-50%, 4 h-75%, 2 h-50%. The obtained samples were sedimented with centrifuge process, washed with distilled water to remove solvent, and dried. Different solvents were compared in the best power–time relationship. These solvents are dimethylformamide (DMF), isopropyl alcohol, N-methyl pyrrolidone, ethylene glycol. The best results were obtained in DMF. The synthesized BNNS samples were subjected to particle size (Malvern), scanning electron microscope (Zeiss, Gemini Supra 55), transmission electron microscope (Jeol Jem-1011), Fourier transform infrared spectroscopy (Thermo Scientific Nicolet™ iS™ 5), Raman (WITech alpha 300R), x-ray photoelectron spectroscopy (Specs-Flex), and x-ray diffraction analysis (PANalytical Empyrean).

İncele

Günoglu, Kadir; Güler, Seval Hale; Güler, Ömer; ALmisned, Ghada; Ozkavak, Hatice Varol; Albayrak, M. Gokhan; Akkurt, Iskender; Issa, Bashar; Tekin, H.O.

This study explores the impact of integrating varying concentrations of Erbium Oxide (Er2O3) into Oxide Dispersion Strengthened (ODS) alloys, specifically focusing on gamma-ray and neutron attenuation properties. Utilizing a 316L stainless steel matrix, Er2O3 was methodically incorporated in concentrations ranging from 1 % to 21 % by weight. The structural and radiation attenuation properties of the resultant alloys were comprehensively analyzed using techniques such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and experimental gamma-ray transmission studies. The results demonstrate a significant enhancement in gamma-ray shielding with increased Er2O3 content. This enhancement is quantitatively evidenced by increased linear attenuation coefficient, elevated effective Electron Density (Neff), reduced Half-Value Layers (HVL), and higher effective atomic numbers (Zeff). These findings are crucial for nuclear applications where efficient gamma-ray shielding is paramount. Conversely, a decrease in the effective removal cross section (ΣR) for neutron attenuation was observed with higher Er2O3 concentrations. This suggests a potential compromise in neutron shielding efficiency, attributed to the dilution of neutron-absorbing base elements in the alloy. Additionally, the study reveals notable changes in the microstructural properties of the alloys, including alterations in particle size, distribution, and agglomeration, influenced by varying Er2O3 concentrations. In conclusion, this research provides valuable insights into the design of ODS alloys for nuclear radiation shielding, highlighting the balance between gamma-ray attenuation and neutron shielding properties. The study's findings contribute to the development of advanced materials for safer and more efficient nuclear technology applications.

AtıfScopus20·OpenAlex25

İncele

Güler, Seval Hale; Güler, Ömer; Kavaz, E.; Almisned, Ghada; Issa, Bashar; Tekin, H.O.

Refractory-High entropy alloys (RHEAs) are known for their exceptional mechanical and radiation-resistant properties, making them promising materials for use in nuclear reactors. Their high entropy composition, which consists of multiple elements in roughly equal proportions, can create a stable microstructure that withstands high levels of radiation damage. The objective of this work is to further our comprehension of the unique behavioral, physical, structural, and nuclear radiation attenuation characteristics shown by High-Entropy Alloys (HEA) and Refractory-High entropy alloy (RHEA) materials. Accordingly, two high entropy alloy (HEA) samples through two different compositions were produced. The first composition under consideration is the typical high-entropy alloy (HEA) defined as MnCrFeNiCoMo0.5. The second composition under consideration is a refractory high entropy alloy (RHEA) characterized by the following elemental composition: TiZrNbHfVTa0.1. SEM and EDX analyses were conducted in terms of determining their physical and structural attributes. Next, a133Ba radioisotope together with a HPGe detector were utilized for gamma-ray transmission experiments. Finally, a241Am/Be source and a gas proportional detector were used for neutron absorption experiments for HEA and RHEA samples. The alloy structures displayed a unique degree of uniformity. Throughout the RHEA phase, the incorporation of refractory elements did not provide any discernible adverse impacts on the physical stability. The counting spectrum provided a clear explanation of the gamma ray absorption features shown by the RHEA (R) sample, highlighting its exceptional absorption properties. Regarding the absorption properties of neutrons, it was observed that RHEA had a comparatively reduced amount of absorption. Therefore, it can be concluded that the basic structure of RHEA grants it superior gamma-ray attenuation qualities compared to HEA. It can be concluded that RHEA demonstrates superior applicability as a material in comparison to HEA, especially in situations involving the use of fuel rods, where maintaining of neutron quantity has paramount importance for achieving optimum neutron activation.

AtıfScopus26·OpenAlex29

İncele

Simsek, Tuncay; Güler, Seval Hale

In this study, equimolar nanocrystalline Fe-Si-Cu (at.%) and Fe-Si-Nb (at.%) alloys were synthesized under an Argon atmosphere by a mechanical alloying method. Experimental parameters were determined as 350 rpm, 10:1 BPR, 120 hours. Phase structures of the synthesized alloys were investigated by X-Ray diffractometry, morphology and elemental analyzes were investigated by SEM-EDS, and magnetic properties were investigated by vibrating sample magnetometer (VSM) technique at room temperature. The crystallite size of the Fe-Si-Cu alloy was found to be 102.3, 22.5, 15.9 and 8.6 nm at the beginning of grinding, after 30, 60 and 120 hours grinding, respectively, and the lattice strains were 0.164%, 0.510%, 0.672% and 1.165%, while the Fe-Si-Cu alloy For the Nb alloy, the crystallite sizes were calculated as 140.8, 42.9, 16.8 and 7.8 nm, and the lattice strains were calculated as 0.134%, 0.301%, 0.639% and 1.271%. According to the magnetism results, the saturation magnetization (Ms) of the Fe-Si-Cu (at.%) alloy was found to be 3146 emu/g, while the saturation magnetization of the Fe-Si-Nb (at.%) alloy was found to be 8.91 emu/g. It was determined that Nb addition to the Fe-Si alloy system caused an increase in the coercivity values.

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