Karaduman, Oktay

Rare earth compounds, including lanthanide hydroxides, have been greatly interested for their promising uses, such as in optoelectronics or photonics, due to their unique electronic and optical transitions properties based on their 4f electron shells. In this work, for the first time new transparent flower-like lanthanum(III)hydroxide (La(OH)3) with borate (LaB3O6) composite nanosheets having a semiconducting band gap suitable for optoelectronics were synthesized by a very simple one-step solvothermal method from a mixture of pure lanthanum oxide and boron without using water or any acidic solvent or surfactant. The practical synthesis was made for two different solvothermal time durations. The synthesized nanocomposites were investigated by XRD, FIB-SEM imaging, EDS, FTIR, UV-vis absorbance, Raman, Ellipsometry, and TG-DTA analyses. The pure precursors lanthanum oxide (La2O3) and boron converted to La(OH)3 and LaB3O6. EDS elemental mapping showed the homogeneous distribution of elements in the nanocomposites. A strong deep-UV absorbance band was detected. The very low reflectance and excellent visible transmittance (exceeding 86% for the sample with a longer solvothermal process time) reaching infrared region were achieved. The direct and indirect band gap energies were estimated by the Tauc plot method for both of the composite samples. Adding boron reduced the literature given direct band gap value (around 4.5-5.5 eV) of pure La(OH)3. DTA and TGA results revealed the steps of mass losses, including decomposition of La(OH)3. FTIR analyses confirmed the presence of the formed compounds. All results showed that the La(OH)3+LaB3O6 nanocomposites can be suitably used in related applications, including electro-optic, photonic, solar cell, catalysts etc.

İncele

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.

İncele

Aslan, Naim; Şükrü Kurt, Mustafa; Mehmet Koç, Mümin; Yilmazer, Yasemin; Coskun, Burhan; Aksakal, Bünyamin

DLC films represent a promising class of materials that can be used in various applications due to their optical, optoelectronic, tribological, and biomedical characteristics. In this work, GeAg- and TiO2-modified DLC thin films were prepared using the magnetron sputtering method under ultrahigh vacuum conditions. DLC thin film characteristics and addition of GeAg and TiO2 into the DLC structure were confirmed and subsequently assessed via scanning electron microscopy (SEM), atomic force microscopy, energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, and Raman spectroscopy. DLC thin film thicknesses were determined via SEM and found to be 235 nm and 380 nm for DLC/TiO2 and DLC/GeAg thin films, respectively. Contact angle and surface wettability analyses were performed for uncoated glass, GeAg- and TiO2-modified DLC thin films. The antibacterial properties of the DLC films were assessed for E. coli and S. aureus. The biocompatibility of these same films was confirmed using the L929 cell line, where no toxic effect was evidenced. To elucidate the optical characteristics of the thin films, a UV–vis spectrum was obtained, and band gap energies were proposed using these data. Photoresponse characteristics of the DLC thin films were assessed under varying illumination using current–time plots. It could be seen that DLC thin films’ responsiveness to light was dependent on illumination intensity. The results demonstrate that nanostructures are good candidates for multifunctional applications exhibiting good antibacterial and photoresponsive characteristics with outstanding biocompatibility.

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

Yayla, Nihal; Albayrak, M Gökhan; Güler, Ömer; Sen Baykal, Duygu; Alkarrani, Hessa; ALMisned, Ghada; Issa, Bashar; Tekin, H.O.

This study investigates the multi-dimensional effects of increasing Gd2O3 reinforcement on the structural, mechanical, and gamma-ray shielding properties of AISI 316L stainless steel composites. Samples with varying Gd2O3 content (1%, 5%, 10%, and 20% by weight) were synthesized and characterized through x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to assess the microstructural changes and homogeneity of Gd2O3 dispersion after mechanical milling. The addition of Gd2O3 significantly enhanced the gamma-ray shielding properties, with the mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), and half-value layer (HVL) improving as the Gd2O3 content increased, particularly in low to moderate photon energy ranges. Simultaneously, the elastic modulus exhibited an inverse relationship, decreasing with higher Gd2O3 content due to the lower stiffness of gadolinium compared to iron. Transmission factor (TF) values also decreased, indicating enhanced photon attenuation with higher Gd2O3 content across various thicknesses. The experimental characterization confirmed improved Gd2O3 dispersion and material uniformity after mechanical milling, contributing to the composites’ superior radiation shielding performance. It can be concluded that Gd2O3-reinforced AISI 316L stainless steel composites offer a promising balance between enhanced radiation shielding properties and reduced mechanical stiffness, making them ideal candidates for applications requiring efficient and adaptable radiation protection especially for portable and non-structural shielding applications.

AtıfScopus3·OpenAlex3

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.

İncele

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.

AtıfScopus1·WoS1·OpenAlex1

İncele

Aydin, Handan; Odak, Mehmet

In this study, the structural and optical properties of CdO thin films subjected to heat treatment at different temperatures were investigated. CdO films were deposited on glass substrates by thermal evaporation. X-ray diffraction technique (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and atomic force microscopy (AFM) measurements were taken to investigate the crystal structure and surface morphology of the prepared films UV-vis spectrometer was utilized to measure the optical properties. As a result of XRD measurements, it was observed that the CdO thin film without and with heat treatment has a cubic crystal structure. The increase in the sharpness of x-ray peaks in CdO thin films with heat treatment means an increase in crystallization, and the calculated crystal sizes showed that the crystal size generally tends to increase with a rise in the applied annealing temperature. As can be seen from the SEM images, it was observed that the small grains on the surface were replaced by large grains as a result of the merger of small grains with each other with rising annealing temperature. The optical band gap Eg, which changes with heat treatment, was calculated to be between 2.45 and 2.27 eV. It was concluded that heat treatment improves the conductivity of CdO thin films by reducing the Eg value.

AtıfScopus1·WoS1·OpenAlex3

İncele

ALMisned, Ghada; Guler, Omer; Ozkul, Iskender; Sen Baykal, Duygu; Alkarrani, Hessa; Kilic, G.; Mesbahi, A.; Tekin, H.O.

To qualify for nuclear applications, materials must meet specific criteria, including mechanical properties, high-temperature behavior, corrosion resistance, and high-temperature oxidation resistance. High Entropy Alloys (HEAs) are particularly suitable for these applications due to their unique properties. Consequently, we conducted a theoretical and simulation-based approaches to assess some critical properties including radiation shielding properties of some quinary FeNiCoCr HEAs. In this study, we focused on quinary FeNiCoCr HEAs, whose corrosion properties have been previously examined in the literature. We investigated the thermodynamic and radiation shielding properties of HEAs with sixteen different compositions. Our methodology included evaluating thermodynamic parameters such as Mixing Entropy (∆Smix) and Mixing Enthalpy (∆Hmix), as well as structural characteristics like Valence Electron Concentration (VEC) and Atomic Size Difference (δ). This allowed us to systematically deduce the phase behavior and stability of various HEAs. Through computational modeling, we assessed the radiation shielding capabilities of these alloys, particularly their effectiveness in attenuating gamma ray and fast neutrons. The results identified FeNiCoCrW as the alloy with the lowest fast neutron removal cross-section values, highlighting its potential for nuclear applications. Its high melting point and the synergistic interplay between its elemental composition and thermodynamic properties suggest broad applicability in extreme environments. Thus, FeNiCoCrW emerges as a promising HEA with multifunctional capabilities, warranting further exploration and potential integration into advanced engineering solutions.

AtıfScopus8·OpenAlex10

İncele

Karaduman, Oktay; Özkul, İskender; Aksu Canbay, Canan

Cu-based shape memory alloys (SMAs), except for exhibiting shape recovery, superelasticity, and high damping, are desirable because these smart materials have higher electrical and thermal conductivity and much lower prices than NiTi SMAs. However, they also have some downsides in mechanical strength and brittleness (mostly stemming from their coarse grain structure) and thermal instability. Therefore, adding some grain refining elements to these SMAs to improve their shape memory effect (SME), and thermal, structural, and mechanical properties is a widespread and simple way that significantly affects their martensitic phase transitions, structure, and mechanical properties. One of these grain-refining elements is titanium. Its thermal conductivity is lower than those of Cu and Al elements and has a low solubility in Cu-matrix. Besides the effects of small Al variations, the use of minor amounts of titanium in binary CuAl-base alloys can show impressive effects on all characteristics of these shape memory alloys, such as shape memory effect properties, martensitic transformation kinetics parameters, and microstructural features. In this research work, CuAlTi ternary high-temperature shape memory alloys (HTSMAs) with new compositions were produced by the arc melting method without a complicating use of Mn or Ni components in usual ternary CuAlMn and CuAlNi shape memory alloys. Thermal analyses of the prepared samples of the alloys were investigated by using differential scanning calorimetry (DSC) and differential thermal analysis (DTA) measurements. In contrast, x-ray diffraction (XRD) test results and optical micrographs were used for analyzing the structure of the alloy samples. The effect of different amounts of low soluble and grain refining Ti element on the binary CuAl alloy system was investigated.

AtıfScopus2·WoS2·OpenAlex2

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