Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleAçık Erişim2026Scopus SJRQ2Design of Fe–35Ni/PCL nanocomposites with coupled magnetic and shape memory properties
Kök, Mediha; Çirak, Z Deniz; Aydin, Handan; Coşkun, Meltem
In this study, poly(ϵ-caprolactone) (PCL)-based nanocomposite films reinforced with a Fe–35%Ni alloy, which possesses a low coefficient of thermal expansion and distinct magnetic properties, were produced. The composites were prepared using the solvent casting method, with the Fe–Ni alloy incorporated into the PCL matrix at different weight ratios (10%–50%). The structural, morphological, thermal, and magnetic properties of the resulting nanocomposites were comprehensively investigated using FTIR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), SEM (scanning electron microscopy/energy dispersive x-ray spectroscopy), differential scanning calorimetry, TGA (Thermogravimetric analysis) ve (vibrating sample Magnetometry). FTIR results indicated that the Fe–Ni addition does not form chemical bonds with the PCL matrix and that the composite structure is formed through physical interactions. XRD analyses confirmed that the semi-crystalline structure of PCL is preserved and that the Fe–Ni alloy exhibits a face-centered cubic (FCC) crystal structure. SEM images revealed that while a homogeneous distribution is achieved at low doping levels, partial agglomeration occurs at high levels. Thermal analyses showed that Fe–Ni particles increase the degree of crystallization through a nucleation effect and provide a significant increase in melting temperature and crystallinity values, particularly in the 10%–40% range. TGA results revealed that the thermal stability of the composites increased and their decomposition behavior became multi-stage. Magnetic measurements showed that the saturation magnetization increased significantly with increasing Fe–Ni content, and the composites acquired ferromagnetic character. Furthermore, it was determined that the developed composites exhibit distinct shape memory behavior and can return to their original form upon thermal stimulation. The findings indicate that Fe–35%Ni-doped PCL nanocomposites are a promising candidate for multifunctional applications due to their enhanced thermal, magnetic, and smart material properties.
- MakaleAçık Erişim2026Scopus SJRQ1Comparative effects of La2O3 and Sm2O3 on structural and radiation shielding properties of WO3 enriched borate glassy-ceramics
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 - MakaleAçık Erişim2026Scopus SJRQ3Functional magnetic polymer nanocomposites: Fe2O3/Fe3O4-enhanced PCL-PVA materials
Deniz Çirak, Zehra; Aydin, Handan; Coşkun, Meltem; Kök, Mediha
In this study, magnetic polymer nanocomposites based on PCL/PVA PCL(Polycaprolactone)-PVA(Polyvinyl alcohol) (80/20) reinforced with Fe2O3 and Fe3O4 nanoparticles were successfully produced, and their thermal, structural, morphological, and magnetic properties were comparatively investigated. The systematic evaluation of the effects of Fe2O3 and Fe3O4 additions on the same biodegradable polymer matrix at 20% and 40% loading levels constitutes the main novelty of this study. The nanocomposites were characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and physical property measurement system (PPMS) analyses. The TGA results demonstrated that the decomposition onset temperature increased with the addition of nanoparticles and, particularly in the composite with 40% Fe3O4 content, the residual mass reached 15.81%, indicating a significant improvement in thermal stability. DSC analyses showed that the melting peak temperature increased at high loading levels and that Fe2O3 loading supported crystallization more than Fe3O4. FTIR and XRD results confirmed that the nanoparticles dispersed successfully in the polymer matrix without forming chemical bonds and provided strong interfacial interactions. The SEM images revealed a homogeneous distribution at low loading levels, while significant agglomeration formed at high Fe3O4 content. Magnetic measurements indicated that the pure PCL/PVA blend exhibited diamagnetic behavior, Fe2O3-containing composites displayed hard ferromagnetic behavior, and Fe3O4-containing composites exhibited soft ferromagnetic behavior. The highest saturation magnetization of 10.4 emu/g was obtained in the composite with 40% Fe3O4 content. The findings indicate that Fe2O3- and Fe3O4-doped PCL/PVA nanocomposites are functional materials with high potential for applications in sensors, actuators, magnetically controlled systems, and biomedical applications.
- MakaleAçık Erişim2026Scopus SJRQ1Change in phase stability and transformation kinetics of NiTiCuW alloy after heat treatment at 650–850 °C
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.
- MakaleAçık Erişim2026Scopus SJRQ1Radiation shielding performance of (SmEuYbLaEr)2TaO4 high-entropy oxide reinforced Cu matrix composites
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.
AtıfScopus1OpenAlex1İncele - MakaleAçık Erişim2026Scopus SJRQ2Pressure-induced transformation in NiTi-CuAg shape memory alloys: investigation of microstructural and thermodynamic changes
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.
- MakaleAçık Erişim2026Scopus SJRQ2Investigation of the Mechanical and Metallographic Effects of Adding 2-3% Al-Ti-Mo Elements to High-Entropy CoCrFeNi Alloys
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.
- MakaleAçık Erişim2026Scopus SJRQ2Structural and optical properties of Bi- and Sn-doped Sb2Se3 thin films prepared by thermal evaporation
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.
- MakaleAçık Erişim2026Scopus SJRQ1Comparative and systematically analysis of the effects of single and high-entropy rare earth oxide additives on the some physical properties and radiation shielding properties of copper composites
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.
AtıfScopus1OpenAlex1İncele - MakaleAçık Erişim2026Scopus SJRQ1Structural and radiation shielding properties of high-entropy rare-earth oxide-doped borosilicate glass
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.
AtıfScopus1WoS1OpenAlex1İncele - MakaleAçık Erişim2026Scopus SJRQ1Investigation of the structural, thermal and radiation shielding properties of (Er0.2Yb0.2Sm0.2La0.2Eu0.2)2Zr2O7 high entropy oxide reinforced tin matrix composite
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.
- MakaleYalnız künye2025Scopus SJRQ2The effect of WC addition on CrMnFeCoNi high entropy alloys: crystal-micro structure, hardness and wear behavior
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.
- MakaleAçık Erişim2025Scopus SJRQ2Effects of multiple element doping in NiTi based SMAs: Variation of phase transition and structural properties with Cu and Ag doping
Tatar, Cengiz; Mohammed, Safar Saeed; Kanca, M Sait; Qadir, Rezhaw Abdalla; Kök, Mediha
In this study, Ni41−2xTi49Cu7+xAg3+x (x = 0, 1, 2, 3) shape memory quaternary alloys were synthesized by arc melting, and their thermal, structural and mechanical properties were extensively investigated. Systemically, investigations have been carried out on the phase transformation behavior, thermodynamic properties, microstructure and oxidation resistance of the alloys with increasing Cu and Ag content. Differential Scanning Calorimetry (DSC) showed the shape memory effects of all alloys at low temperature. The transformation temperatures increased with increasing Cu and Ag concentrations. Thermodynamic analysis showed that Gibbs free energy trends and entropy were attributed to increased thermal stability at higher doping levels. XRD analysis confirmed the presence of martensitic (β19, β19′) and intermetallic Ti2(NiCu) phases, and grain refinement was found in higher doped samples. Microhardness measurements showed more homogeneous and stabilized microstructures at increasing doping, while SEM imaging showed that the hardness increased significantly. Thermogravimetric analysis showed that Cu and Ag slightly compromised the oxidation resistance due to the destabilization of the passive oxide layers. These results suggest that varying the Cu and Ag content in NiTi-based alloys is an effective method for improving mechanical strength and thermomechanical performance in advanced engineering applications.
AtıfScopus1WoS1OpenAlex1İncele - MakaleYayıncıda açık erişim2024Scopus SJRQ2Selenium Inhibitor Coating on NiTi Shape Memory Alloys by Using Thermal Evaporation System
Kök, Mediha; Kanca, Muhammed Sait; Say, Yakup; Saydam, Sinan; Dağdelen, Fethi; Qader, Ibrahim Nazem
NiTi-based memory alloys are often used as intracorporeal implant materials because of their superelasticity and shape memory properties. However, over time, the release of nickel from the NiTi alloy into the body becomes unfavorable; therefore, studies should be conducted to reduce the negative impact of nickel leakage. In this study, the biocompatible selenium element was used to coat NiTi alloys with different thicknesses. The coating process was performed using the thermal evaporation technique. Scanning electron microscopy-Energy Dispersive X-ray Analysis measurements revealed that the surfaces of the samples were well covered. Also, the atomic force microscope device determined the surface roughness of the alloys. The roughness of the surface increased after the coating process. The Tafel test was accomplished to determine the biocompatibility of the coated and uncoated alloys in an artificial body fluid. The corrosion test reveals that Se-coated NiTi alloys have high corrosion resistance.
- MakaleAçık Erişim2024Scopus SJRQ2Zr and V-doped effect on Martensitic transformations and magnetic properties of NiMnIn shape memory alloy
Taşgın, Yahya; Kanca, M. Sait; Kök, Mediha; Öner, Ecem Özen; Güler, Ömer
In this study, the elements vanadium (V) and zirconium (Zr) were doped separately as a fourth element to the ternary NiMnIn Heusler magnetic shape memory alloy and the alloys were produced as ingots by arc-melting method. The shape memory properties, microstructures, magnetic and microstructural changes of these new alloys were investigated in detail. The vanadium (V) and zirconium (Zr) elements doped into the alloy caused a decrease in the transformation temperature values of the alloy, but did not cause a significant change in its magnetic properties. The master sample, which has low hysteresis, undergoes a phase transition from the martensite phase to the austenite phase due to an increase in the nucleation of austenite phases at the twinning boundaries. Here, the vanadium and zirconium doping of the alloy caused an increase in the strength and ductility values of the alloy and this caused the formation of the second phase. Due to the increase of this phase formation in the alloy, it can be said that there is a slight decrease in the shape retention of the alloy.
AtıfScopus3WoS3OpenAlex3İncele - MakaleAçık Erişim2024Scopus SJRQ1Production of Ho2O3 and Dy2O3 rare earth oxides doped selenium thin film and investigation of surface morphology and optical properties
Aydin, Handan; Sait Kanca, M.; Kök, Mediha; Taşgin, Yahya; Tatar, Beyhan
Thin film technology aims to improve and develop the properties of materials by coating technology. In this study, thin films consisting of rare earth element and selenium semiconductor material, which have recently been preferred in technological applications due to their important properties, are examined. Selenium thin films doped with Ho2O3 and Dy2O3 rare earth oxides (REO) were fabricated on glass substrate by thermal evaporation method. The surface morphology and optical properties of the thin films were investigated. As a result of surface morphology examinations, it was determined that homogeneous thin films were obtained and the thickness of the thin films varied between 20 and 30 μm. In addition, the roughness value of the glass substrate decreased as a result of coating with doped selenium thin film. The band energy value obtained by UV-VIS measurements decreased compared to glass and was close to the selenium element value. In the comparison between selenium coatings doped with Ho2O3 and Dy2O3, a notable reduction in the Eg value was observed specifically in the Ho2O3 doped coatings.
AtıfScopus3OpenAlex3İncele - MakaleAçık Erişim2024Scopus SJRQ2External oxide layers formed by the oxidation procedure in FeMnSi and FeMnSiCr shape memory alloys and their effects
Tatar, Cengiz; Kök, Mediha; Kanca, M Sait; Tatar, Beyhan
Shape memory alloys are exposed to high temperatures to improve their properties and functionality. Through this process, oxidation inevitably occurs due to the presence of oxygen in the environment, which interacts with the alloying elements. Oxidation adversely affects the hardness of alloys, leading to a decline in their overall quality. In this study, the oxidation behavior parameters of FeMnSi and FeMnSi-Cr alloys and the oxide layers formed during this process were investigated in Fe-based alloys with high usage potential. Both non-isothermal and isothermal oxidation processes were applied to alloys and the oxidation parameters were determined. Subsequently, the changes in the crystal structure, microstructure, and magnetic properties of the alloys subjected to isothermal oxidation at 400-500-600-700-800 °C were investigated. It was found that the oxidation behavior of both alloys intensified with rising oxidation temperatures, as evidenced by crystal structure and microstructural analyses, which indicated deeper penetration into the alloys at elevated temperatures. Furthermore, an increase in magnetization values was noted alongside the oxidation process. A comparison of the oxidation characteristics between FeMnSi and FeMnSi-Cr alloys revealed that the oxidation parameters for the chromium doped FeMnSi alloy were comparatively lower.
AtıfScopus2OpenAlex2İncele - MakaleAçık Erişim2024Scopus SJRQ2Physical and shielding properties of Er2O3 rare earth oxide compound content on PCL/PEG blend
Taşgin, Yahya; Pekdemir, Mustafa Ersin; Yilmaz, Mücahit; Kanca, Muhammed Sait; Kök, Mediha
Rare earth elements (RRE), due to their unique magnetic, electrical, and optical properties, are an important group of elements demanded in many application areas from machine technology to the health industry. In this study, new composites were obtained by mixing Erbium oxide (Er2O3), one of the rare earth element oxides, into PCL–PEG blend, which is also an important material group, in different ratios. The characteristic functional groups of the obtained polymer blend/Er2O3 nanocomposites were determined by the ATR-IR, and as the erbium oxide ratio increased, characteristic peaks of the polymers in the blend as well as characteristic signals of the Er–O–Er bond were found. When the thermal behavior of the obtained composites was examined, it was observed that the polymer blend exhibited miscible blend properties and the melting temperature of the polymer blend increased as the Er2O3 ratio increased. In addition, it was determined that the thermal stability of the composite increased significantly. X-ray measurements of composites at room temperature support other measurement results. It was determined that the presence of Er-RRE oxide increased the crystal structure feature in the polymer blend composite. Gamma radiation shielding capabilities of polymer materials containing different erbium ratios were investigated by calculating shielding parameters such as half value layer (HVL), radiation protection efficiency (RPE), and mean free path (MFP). Cs-137 and Co-60 radioactive sources were used as gamma sources. According to the obtained measurement results, Erbium oxide increased the absorption property of the polymer composite material. Graphical abstract: [Figure not available: see fulltext.].
AtıfScopus26WoS28OpenAlex29İncele - MakaleAçık Erişim2023Scopus SJRQ2B2O3 reinforced polylactic acid/thermoplastic polyethylene glycol shape memory composites
Pekdemir, Mustafa Ersin; Kök, Mediha; Kanca, Muhammed Sait; Özen Öner, Ecem; Pekdemir, Sibel; Inci, Şule; Kirbağ, Sevda; Tatar, Beyhan
Recently, there has been a great demand for boron-containing compounds (BCCs) with unique biological properties. The demand for the use of these compounds not alone but as additives in composite materials is increasing day by day. In this study, the effect of adding B2O3 compound to the blend of PLA and PEG polymers, which is an important biocompatible shape memory polymer, was investigated. In order to examine the effect of increasing B2O3 additive on the thermal properties of PLA-PEG blend, it was determined by using a Differential Scanning Calorimetry (DSC) and thermogravimetric analyzer (TGA), and it was seen that while the melting temperature of PEG decreased, the melting temperature of PLA increased. In addition, when the thermal stability of the composites was examined, increasing of thermal stability was observed with the addition of B2O3 and a three-step degradation occurred. It was determined that the B2O3/PLA-PEG composite was homogeneous by taking X-ray measurements and SEM measurements. The antimicrobial property of the PLA-PEG blend improved with the increasing B2O3 contribution were observed from the antimicrobial activity measurements of the composite against 4 different bacteria. However, it was determined that the PLA-PEG blend preserved its shape memory effect with increasing diboron trioxide contribution.
AtıfScopus13OpenAlex16İncele - MakaleAçık Erişim2023Scopus SJRQ2Silver and Copper Coating Effects on Surface Morphology, Crystal Structure and Corrosion Behavior of NiTinol Shape Memory Alloy Plate
Say, Yakup; Kanca, Muhammed Sait; Kök, Mediha
NiTinol alloy has recently been in high demand in biomaterials applications due to its excellent superelasticity and shape memory properties. This demand has increased the studies on improving the negative properties of the NiTinol alloy, even if it is less. In this study, it was aimed to coat the nickel element in the NiTi alloy with biocompatible elements in order to prevent it from secreting its toxic effect after its implantation into the body. In accordance with this purpose, NiTi shape memory alloys were coated with silver and copper element by using thermal evaporation system, and the surface morphology of the alloys after coating was investigated by SEM–EDX (Scanning Electron microscope), and AFM (Atomic force Microscope). After the measurements, it was observed that the coating was successful and homogeneously distributed on the entire surface of the alloy. In addition, an important and positive result was that, the roughness value of the NiTi alloy was decreased with the coating. The change in the crystal structure of the uncoated and coated NiTi alloy was evaluated using an X-ray device, and it was observed that the silver and copper element peaks were formed along with the B2 phase, which is the main phase of the NiTi alloy. In order to examine the effect of coating on the biocompatibility of NiTi alloy, electrochemical test was performed by rapid measurement method in simulated body fluid and corrosion behavior was investigated. According to these experiments, it was concluded that silver plating is more successful in term of biocompatibility than copper coating.
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