Taşgın, Yahya; Yılmaz, Demet; Kanca, M. Sait; Yayla, Nihal; Kök, Mediha; Güler, Ömer

This research comprehensively investigates the impact of incorporating rare earth oxides ‑samarium oxide (Sm2O3) and lanthanum oxide (La2O3)- into a borate glassy-ceramic system enriched with tungsten oxide (WO3), with a focus on both structural characteristics and radiation shielding performance. SEM-EDS, elemental mapping, and XRD analyses conducted on the synthesized glassy-ceramic samples revealed that the incorporated rare earth oxides, Sm2O3 and La2O3, were uniformly distributed throughout the glassy-ceramic matrix. The results also confirmed that the glassy-ceramic retained its inherently amorphous structure. Moreover, the nominal doping levels of the rare earth elements were found to be in agreement with both the qualitative and quantitative results obtained from EDS measurements. Also, the gamma ray shielding parameters of synthesized glassy-ceramic samples were measured in absorption geometry with Am-241, Ba-133 and Ra-226 radioactive sources. The neutron shielding parameters were theoretically calculated. The 241Am-Be fast neutron source was used to measure the equivalent dose of neutron absorption. At an incident photon energy of 74.8 keV, the mass attenuation coefficient of the tungsten oxide–enriched borate glassy-ceramic exhibited a remarkable improvement—rising by 17.98 % with the addition of 3 wt% Sm2O3 and by 11.58 % with the addition of 3 wt% La2O3. Notably, the N4 sample demonstrated a significant reduction in neutron-equivalent dose rate, reaching 19.80 % (μSv/h). The lead equivalent thicknesses (Pbeq) calculated at 356 keV were 0.02397 cmPb for N0, 0.0391 cmPb for N1, 0.0403 cmPb for N4, and 0.0389 cmPb for N7. When benchmarked against the undoped N0 sample, the N4 and N7 compositions exhibited reductions in Pbeq values by approximately 68 % and 62 %, respectively, indicating a marked improvement in gamma shielding efficiency. Among all tested formulations, the Sm2O3-doped variant demonstrated superior gamma-ray attenuation capability relative to the La2O3-doped glassy-ceramic. Furthermore, the N4 sample achieved an impressive thermal neutron attenuation rate of 96.46 %, underscoring its strong potential as an effective dual-purpose shielding material against both thermal neutrons and ionizing gamma radiation.

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İncele

Tatar, Cengiz; Kök, Mediha; Kanca, M. Sait

In this study, the effects of different heat treatment temperatures (650 °C, 750 °C, and 850 °C) on the phase transformation behavior, microstructure, thermodynamic parameters, and microhardness of the NiTiCuW alloy, produced by adding tungsten (W) to the NiTiCu shape memory alloy, were investigated. The crystal structure change was determined by X-ray diffraction (XRD), the transformation temperatures were determined by differential scanning calorimetry (DSC), the microstructure was examined by scanning electron microscopy (SEM), and the mechanical properties were evaluated by Vickers microhardness measurements. XRD results showed that the reference and 850 °C samples were predominantly in the B2 (austenite) phase at room temperature, while martensitic phases (B19/B19′) became prominent at 650 °C and 750 °C. DSC analyses revealed that the transformation peaks became sharper at 650 °C and the R-phase transformation could be observed; at 750 °C, the peaks broadened, indicating a decrease in transformation stability. The austenite finish temperature (Af) increased from 2.1 °C (reference) to 52.9 °C at 650 °C and 60.3 °C at 750 °C, while it remained low (4.5 °C) at 850 °C. Thermodynamic evaluations showed that ΔS increased at 650 °C (0.053 J/g K) and decreased at 750–850 °C (≈0.032 J/g K). Microhardness reached its maximum value at 650 °C (398 Hv), decreased at 750 °C (271 Hv), and showed an upward trend again at 850 °C (351 Hv), compared to the reference value (243 Hv). These results indicate that the heat treatment temperature critically determines the functional and mechanical performance of the NiTiCuW alloy.

İncele

Taşgın, Yahya; Yılmaz, Demet; Kanca, M. Sait; Kök, Mediha; Yayla, Nihal; Güler, Ömer

High-entropy oxides (HEOs) containing rare earth elements are attracting increasing interest due to their thermal stability and potential for use in radiation shielding applications. In this study, the high-entropy oxide (SmEuYbLaEr)2TaO4 was synthesized via mechanical alloying (MA) followed by calcination and incorporated into a Cu matrix at different reinforcement levels to produce volumetric composites. Structural, thermal, and microstructural analyses confirmed the successful formation of a stable HEO phase and its effective dispersion within the Cu matrix. The radiation shielding performance of the composites was experimentally evaluated over a wide range of photon energies using standard gamma-ray sources. The results showed that shielding performance depends largely on both photon energy and HEO content. Increasing the HEO concentration significantly reduced the half-value layer (HVL) while substantially increasing the mass attenuation coefficient (MAC) and radiation protection efficiency (RPE), particularly in the low- and medium-energy regions where the photoelectric effect is dominant. Among the materials studied, the Cu composite containing 20 wt% HEO exhibited the best overall shielding performance. These results demonstrate that (SmEuYbLaEr)2TaO4 is an effective additive for improving the radiation shielding capability of Cu-based composites and highlight its potential for advanced radiation protection applications.

AtıfScopus1·OpenAlex1

İncele

Tatar, Cengiz; Kök, Mediha; Kanca, M Sait; Balci, Esra; Qader, Ibrahim Nazem

Shape memory alloys (SMAs), particularly nickel-titanium (NiTi) based systems, are widely recognized for their unique shape memory effect and superelastic behavior, driven by reversible martensitic phase transformations. To enhance these functional properties for advanced applications, alloying with elements such as copper (Cu) and silver (Ag) has been explored. This study investigates the synthesis and characterization of a novel quaternary NiTiCuAg shape memory alloy. The alloy was fabricated via arc-melting from high-purity elemental powders, followed by application of varying uniaxial compressive pressures to assess their effects on phase transformation behavior. Thermal, structural, and microstructural properties were evaluated using Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy coupled with Energy-Dispersive x-ray Spectroscopy (SEM-EDX), and x-ray Diffraction (XRD). The results aim to elucidate the combined effects of compositional tailoring and mechanical processing on the functional performance of NiTiCuAg SMAs, with implications for their use in high-performance, pressure-sensitive applications.

İncele

Dilek, İlhan; Taşgın, Yahya; Kanca, Muhammed Sait; Kök, Mediha; Güler, Ömer

Recently, high-entropy alloys (HEAs) have attracted significant attention due to their unique multicomponent composition and exceptional mechanical properties, such as high wear and corrosion resistance, making them superior to conventional alloys for advanced engineering applications. The effects of Al, Ti, and Mo addition on the microstructural and mechanical properties of CoCrFeNi-based HEAs were investigated. The alloys were produced via powder metallurgy and vacuum arc melting, with the addition of 2 and 3% Al, Ti, and Mo, respectively. Scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD) were used to perform microstructural characterization, while microhardness and wear tests were used to evaluate mechanical performance. The addition of Al and Ti enhanced the face-centered cubic phase stability and increased the hardness by improving the lattice structure. In contrast, the addition of Mo contributed to solid solution and precipitation hardening, resulting in a simpler microstructure and superior tribological performance. Among all compositions, the alloy with 3% Mo addition exhibited the highest hardness value (≈ 233.8 HV) and the lowest mass loss (4.3 mg) was observed, indicating a significant improvement in the wear resistance and mechanical strength. In conclusion, the addition of Ti and Mo to CoCrFeNi HEAs promotes solid solution, precipitation, and grain boundary hardening mechanisms, thereby enhancing microstructural integrity, hardness, and wear resistance. These findings suggest that such alloys are promising candidates for use as next-generation structural and tribological materials under demanding operational conditions.

İncele

Kök, Mediha; Öztürk, Yunus; Sait Kanca, M.

In this study, Sb2Se3-based semiconductor thin films, both pure Sb2Se3 and those doped with Bi and Sn, were produced using the thermal evaporation method. The structural, morphological, and optical properties of the obtained films were investigated using XRD, SEM, and UV–Vis spectroscopy. While films without annealing exhibited an amorphous structure, significant crystallization was observed after annealing at 350 °C, especially at high doping levels. SEM analyses showed significant changes in surface morphology and grain structure depending on the doping level. Optical measurements revealed that absorption increased and the band gap changed with increasing doping level. The band gap for the undoped Sb2Se3 thin film was found to be 1.54 eV. An increase due to the Burstein–Moss effect was observed at low additive ratios, while band narrowing was observed at high additive ratios. The results obtained indicate that Bi and Sn additives improve the optoelectronic properties of Sb2Se3 thin films and hold potential for photovoltaic applications.

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

Güler, Ömer; Yılmaz, Demet; Kanca, Muhammed Sait; Kök, Mediha; Taşgın, Yahya

In this study, the incorporation of a high-entropy rare-earth oxide, (GdLaEuPrDyY)2O3 (RE-HEO), into a borosilicate glass matrix was investigated with the aim of improving radiation shielding performance while preserving the structural integrity of the glass. The RE-HEO was first synthesized by high-energy mechanical alloying and then introduced into the glass system at concentrations ranging from 0 to 8 wt% using a conventional melt-quenching process. The structural and microstructural properties of the prepared samples were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy combined with energy-dispersive spectroscopy (SEM–EDS). The analyses confirmed that the amorphous nature of the borosilicate glass was maintained and that the rare-earth elements were homogeneously distributed within the matrix. The radiation shielding performance was evaluated experimentally using Am-241, Ba-133, and Ra-226 gamma sources, and supported by theoretical calculations of key parameters including mass attenuation coefficient (MAC), half-value layer (HVL), mean free path (MFP), effective atomic number (Zeff), exposure buildup factor (EBF), and fast neutron removal cross-section (ΣR). The results showed that increasing RE-HEO content leads to a noticeable improvement in gamma-ray attenuation. In particular, the sample containing 8 wt% RE-HEO exhibited a MAC value of 0.131 cm2/g and an HVL of 2.03 cm at 356 keV, indicating shielding performance comparable to that of conventional lead-containing glasses. In addition, irradiation tests performed using a Co-60 gamma source revealed that the amorphous structure remains stable after exposure. Overall, the findings suggest that RE-HEO-doped borosilicate glass can be considered a promising lead-free alternative for radiation shielding applications.

AtıfScopus1·WoS1·OpenAlex1

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

Taşgın, Yahya; Kanca, M Sait; Kök, Mediha; Anik, Kerem

High entropy alloys are produced by combining four or more elements in close percentage ratios. Recently, these alloys have become the preferred group due to their superior mechanical and thermal properties. In this study, tungsten carbide (WC) was doped into CrMnFeCoNi alloys at different ratios, and the effects of WC and heat treatment on the doped alloys were investigated. XRD, SEM, and EDS analyses, wear tests, and microhardness measurements were performed on the produced samples to examine their microstructural properties. When comparing the heat-treated samples with WC (3%, 5%, and 10% additions) to the untreated samples, it was found that the average hardness values of the heat-treated samples were higher. Although the grain structures of the samples, as observed through XRD, SEM, and EDS, were preserved, their ratios were altered, and the wear tests revealed that the mass losses of the heat-treated samples increased.

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