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

Durmus, Hasan; Kilic, G.; Ilik, E.; Kavaz, E.; Güler, Ömer; Birdogan, Selcuk; ALMisned, Ghada; Tekin, H.O.

This study investigates the structural evolution and radiation shielding performance of lithium borotellurite glasses reinforced with nano-sized HfO2. We report on the competitive dynamics between the depolymerizing nature of the Li + network modifier and the high field strength Hf4+ nano-dopant, a relationship not previously explored in this matrix. Structural analysis via XRD and TEM reveals that the glass remains fully amorphous with homogeneously dispersed Hf rich nanodomains up to 4 mol%. A critical solubility threshold is identified at 6 mol%, where the precipitation of HfO2 and HfTe3O8 crystalline phases marks a distinct transition from an amorphous state to a glass-ceramic microstructure. Physical property measurements indicate that Hf4+ ions primarily occupy interstitial free volumes, leading to enhanced material density without significant network dilation. The incorporation of nano-HfO2 significantly augments gamma-ray attenuation efficiency, particularly in the low-energy region, by substantially increasing the effective atomic number and reducing the half value layer. Furthermore, the glasses exhibit robust fast-neutron shielding capabilities, outperforming conventional materials such as graphite and B4C. These findings establish nano-HfO2 as a potent structural and radiative modifier, providing a novel roadmap for designing high-density, multifunctional glass-ceramic shields for advanced nuclear applications.

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Güler, Ömer; Şimşek, Telem; Şimşek, Tuncay; Evin, Ertan; Baykal, Duygu Sen; 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 (ΣR = 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.

AtıfScopus10·OpenAlex6

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Kilic, G.; Ilik, E.; Kavaz, E.; Durmus, Hasan; Güler, Ömer; Birdogan, Selcuk; ALMisned, Ghada; Tekin, H.O.

This study investigates the effects of holmium oxide (Ho2O3) microparticle reinforcement on the structural, physical, and radiation shielding properties of borotellurite glasses with compositions ranging from 0 to 12 mol% Ho2O3. X-ray diffraction and TEM analyses confirmed the retention of amorphous structure across all samples, with localized short-range ordering observed at higher Ho contents. Glass density increased from 4.598 to 5.202 g/cm3 with increasing Ho2O3, while molar volume expanded from 27.94 to 30.61 cm3/mol, and oxygen packing density decreased from 0.605 to 0.551 g/cm3, indicating network expansion due to the substitution of lighter Li + ions by heavier Ho3+. Gamma-ray shielding properties significantly improved with Ho incorporation. At 81 keV, the linear attenuation coefficient increased from 8.33 to 13.70 cm−1, and the mass attenuation coefficient improved from 2.066 to 2.735 cm2/g. Moreover, effective atomic number rose from 44.9 to 52.5 and half-value layer decreased by 20.5% at 383 keV, and buildup factors dropped by up to 34% at 0.5 MeV. Neutron dose absorption improved, and the fast neutron removal cross-section increased from 0.1066 to 0.1113 cm−1. These results confirm that Ho2O3 contributes as a highly effective multifunctional dopant, significantly enhancing both gamma-ray and neutron shielding performance of borotellurite glasses, one of the most promising glass systems for advanced radiation protection applications.

AtıfScopus1·OpenAlex1

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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

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; 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.

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ALMisned, Ghada; Susoy, Gulfem; Baykal, Duygu Sen; Alkarrani, Hessa; Güler, Ömer; Issa, Shams A.M.; Zakaly, Hesham M.H.; Tekin, H.O.

This study explores the gamma-ray and neutron shielding properties and mechanical performance of eight Fe-based alloys with varying elemental compositions and densities. Different parameters such as mass attenuation coefficients, linear attenuation coefficients, half-value layer, tenth-value layer, mean free path, fast neutron removal cross-sections, transmission factors were analysed using PHITS and Phy-X/PSD codes. Moreover, elastic modulus values were calculated for each alloy sample. Our results reveal that the S9 alloy, with high density and tungsten contribution, exhibited superior shielding and mechanical properties, achieving the lowest TF, HVL, and TVL values. In contrast, the low-density S1 alloy performed weakest, reflecting its lighter elemental composition. Intermediate alloys like MAR-302 and Cupero-Nickel showed balanced performance, suitable for moderate shielding needs. Strong correlations between elemental compositions, particularly high-Z elements like tungsten and boron, and shielding efficiency were observed. It can be concluded that optimizing elemental composition and density is critical for designing alloys with enhanced multifunctional properties.

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İncele

ALMisned, Ghada; Susoy, Gulfem; Baykal, Duygu Sen; Kilic, G.; Güler, Ömer; Tekin, H.O.

This comprehensive study investigates the radiation attenuation properties of various bismuth (Bi) and lead (Pb) based alloys, with a focus on identifying superior shielding materials for nuclear safety and industrial radiation protection. The research encompasses an in-depth analysis of seven alloys, namely GTSB5, Sn%40Bi, Bi50Sn50, A1, PbAl-4, Safe Alloy, and P1, assessing their efficacy in gamma-ray and neutron attenuation. Utilizing some computational tools, various parameters such as mass and linear attenuation coefficients, half and tenth value layer values, effective atomic and electron numbers, buildup factors, and transmission values were evaluated. Our findings highlight Alloy P1's outstanding performance, attributed to its high density (11.05 g/cm3) and optimized elemental composition, including Silver (Ag). In addition, P1 demonstrates exceptional gamma-ray attenuation across multiple energy spectra and superior neutron shielding capabilities, evidenced by its significant fast neutron removal cross-section (∑R, 0.12003 1/cm). The study revealed that the addition of Ag enhances the photon and beta particle absorption capacity, positioning P1 as a promising material in radiation shielding applications. The correlations between alloy density and gamma-ray shielding properties were particularly notable, with P1's density contributing to its enhanced attenuation capabilities. Furthermore, P1's lower half value layers (1.14469 cm) and tenth value layers (3.80256 cm) at 15 MeV indicate its efficiency in reducing radiation intensity with minimal material thickness.

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İncele

Basgoz, Oykum; Guler, Seval Hale; Guler, Omer; ALMisned, Ghada; Baykal, Duygu Sen; Kilic, G.; Tekin, H.O.

In this study, Al6061–Eu2O3 composites were fabricated via mechanical alloying and systematically characterized using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy to evaluate structural and compositional features. The incorporation of Eu2O3 in varying weight percentages (1–20 wt%) was confirmed by XRD, revealing phase retention and crystallite refinement, while SEM–EDS analyses indicated uniform elemental distribution at low doping and localized clustering at higher reinforcement levels. Radiation shielding properties were comprehensively assessed through mass and linear attenuation coefficients, half value layer, effective atomic number, fast neutron removal cross section, buildup factors, and photon transmission factors. The results demonstrated a strong correlation between increasing Eu2O3 content and improved shielding performance. The E20 composite exhibited a mass attenuation coefficient of 22.33 cm2/g at 0.015 MeV, over threefold higher than the base alloy, and fast neutron removal cross section improved by 22.5 % compared to Al6061 alone. Additionally, EBF and EABF values decreased significantly, confirming reduced secondary photon build-up. These findings validate the effectiveness of Eu2O3 as a reinforcement phase for tailoring Al6061 for multifunctional applications, particularly in nuclear, aerospace, and radiological environments requiring lightweight materials with superior gamma and neutron attenuation.

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