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    Effect of Boron and its Influence on Mechanically Alloyed FeCo Nanocrystals
    (Springer India, 2024) Simsek, Tuncay; Ozgur, Damla; Simsek, Telem; Avar, Baris; Yildiz, Bugra; Chattopadhyay, Arun K.
    This study investigates the effect of adding boron as a ternary addition to binary FeCo alloys. Fe-Co-B ternary alloys with varying boron concentrations between 0 and 2 wt% were synthesized through mechanical alloying. The study aims to analyze the structural, morphological, and magnetic properties of the Fe-Co alloy matrix with the inclusion of boron. The XRD results showed a single solid solution phase of Fe-bcc structure for all alloys, regardless of the boron concentration. It was seen that the low solubility of boron in Fe-Co caused the formation of hard structures at the grain boundaries, resulting in an increase in hardness with an increase in boron concentration. On the other hand, a decreasing trend was observed in coercivity, which is ascribed to the formation of FeB at the grain boundaries, as proved from XRD analysis. An increase in boron concentration did not seem to significantly affect the saturation magnetization, which remained in the range of 190 +/- 10 emu/g for all Fe-Co-B alloys. The experimental data was cross checked and further insights were gained; DFT calculations were performed using Vienna Ab Initio Simulation Package.
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    Effect of Cu, Sn and Sb addition on the structural, thermal and magnetic properties of body-centered cubic structured CoNiMnGaSi high entropy alloy
    (Springer Heidelberg, 2022) Simsek, Telem; Ozkul, Iskender; Canbay, Canan Aksu; Avar, Baris; Simsek, Tuncay; Guler, Seval Hale; Ozcan, Sadan
    In this study structural, morphological, thermal and magnetic properties of equiatomic CoNiMnGaSi (base), CoNiMnGaSiCu, CoNiMnGaSiSn and CoNiMnGaSiSb alloys are discussed. The formation of solid-solution nanocrystalline bcc structure of the alloys was determined by XRD and DTA techniques. SEM-EDS analyses also revealed the homogeneous distribution of the elements. The room temperature magnetic hysteresis loops showed that as-casted alloys reached saturation easily with coercivity less than or equal to 35 Oe. As the Cu and Sn were added to the alloy, the saturation magnetization was decreased from 112 emu/g to 50 emu/g, which was mainly due to the substitution of non-magnetic atoms to the magnetic Co in the base CoNiMnGaSi alloy, whereas the addition of Sb to the base alloy did not have a significant effect on the M-s. The CoNiMnGaSiSb was found to have the highest Curie Temperature of 670 K, which makes the alloy a promising candidate for power industry-related applications.
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    Experimental investigation of the effects of different quaternary elements (Ti, V, Nb, Ga, and Hf) on the thermal and magnetic properties of CuAlNi shape memory alloy
    (Springer Heidelberg, 2022) Ozkul, Iskender; Karaduman, Oktay; Simsek, Telem; Simsek, Tuncay; Canbay, Canan Aksu; Ibrahim, Pshdar Ahmed; Arpa, Ipek A. K.
    To discover cheaper and functional species of shape memory alloys (SMAs) is one of the main objectives for interested researchers. In this work, five different alloys were produced by adding different quaternary alloying elements (Ti, Ga, V, Hf, and Nb) into the ternary CuAlNi-base (C-) alloy.The thermal and structural properties of the produced alloys were investigated. The phases of Al7Cu23Ni, AlNi, CuNi2Ti, Al80V20, AlNbNi2, Cu3Ga, and NiSHf were observed by X-ray powder diffraction (XRD) analyses after arc melting processes. The average crystallite sizes of the produced alloys were calculated as 17.1, 18.9, 19.4, 20.8, and 23.7 nm for CV, CNb, CHf, CTi, and CGa alloys, respectively. The highest lattice strain was found at about % 0.572 for CGa alloy. Measuring the magnetic properties of the produced alloys revealed the paramagnetic behavior of the alloys at room temperature.
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    Experimental investigation of the effects of different quaternary elements (Ti, V, Nb, Ga, and Hf) on the thermal and magnetic properties of CuAlNi shape memory alloy (Jun, 10.1557/s43578-022-00625-y, 2022)
    (Springer Heidelberg, 2022) Ozkul, Iskender; Karaduman, Oktay; Simsek, Telem; Simsek, Tuncay; Canbay, Canan Aksu; Ibrahim, Pshdar Ahmed; Arpa, Ipek Ak
    [Abstract No tAvailable]
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    FeCoNiMnCr high-entropy alloys (HEAs): Synthesis, structural, magnetic and nuclear radiation absorption properties
    (Elsevier Sci Ltd, 2023) Simsek, Telem; Kavaz, Esra; Guler, Omer; Simsek, Tuncay; Avar, Baris; Aslan, Naim; Almisned, Ghada
    We report the synthesis and structural, magnetic and Radiation shielding properties of High Entropy Alloy (HEA) produced through mechanical alloying method. Using an X-Ray Diffractometer (PanalyticalEmpryan) with CuK radiation at 45 kV and 40 mA, the phase identification starting elements and as-milled powders are identified. Scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX), morphological and microstructural investigations were conducted (FEI Quanta FEG 450). EDX and elemental mapping analyses are conducted to assess the purity and elemental distributions of the synthesized alloys. Using the Quantum Design Physical Characteristics Measurement System (PPMS) with vibrating sample magnetometer (VSM) and a magnetic field of 30 kOe at room temperature, magnetic properties are examined. Using Cs-137 radioisotope and mathematical methods, gamma-ray and neutron shielding properties of HEA are investigated in a conventional transmission setup using experimental and theoretical approaches. In the presence of a 3 T applied field, the sample exhibits a low magnetization of 5.30 emu/g at 300 K. Moreover, Ms is raised to 22 emu/g at 10 K owing to decreased thermal effects. The temperature dependence of the magnetization is recorded in the presence of a 1 T applied field. HEA exhibits superior neutron attenuation properties than conventional absorption materials such as B4C, graphite, and water. Our results showed that the synthesized HEA has superiority over other alloys and conventional neutron absorption materials. It can be concluded that the proposed novel HEA might be investigated further in terms of broadening its characterization and clarifying its other crucial properties to extend the scope of the current investigation.
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    High Entropy Materials for CO2 Conversion
    (CRC Press, 2024) Simsek, Telem; Guler, Seval H.; Guler, Omer; Simsek, Tuncay
    Metal-based oxides, ceramics, and composite catalysts are commonly used for CO2 conversion. To increase the efficiency of these catalysts, strategies such as heterostructure, defect engineering, nanolayers, mesoporous structure development, and oxygen vacancy engineering are used. In recent years, highly stable high entropy alloys (HEAs), which include at least five different elements in equimolar or nearly equimolar ratios, have recently come to be recognized as promising CO2 conversion catalysts. Their unique properties enable enhanced reactivity and selectivity, making them highly valuable in addressing CO2 emissions and climate change challenges. When several elements are included in a catalyst, surface microstructures with different atomic configurations and active catalytic sites are produced. As a result, different adsorption modes arise for reactants and intermediates. In addition, the mixing of metal elements in varying atomic ratios causes changes in the electronic structure of metals. The distinct catalytic characteristics of HEAs are a result of modifications to their electronic structure brought on by lattice stretching, distortion, and compositional alterations. © 2024 Anuj Kumar and Ram K. Gupta.