Yazarlar

• ALMisned, Ghada(2)
• Karaduman, Oktay(2)
• Özkul, İskender(2)
• Şimşek, Telem(2)
• Aksu Canbay, Canan(1)
• Baykal, Duygu Sen(1)
• Bülbül, Zeynel Abidin(1)
• Canbay, Canan Aksu(1)
• Dinçer, İlker(1)
• Elerman, Yalcin(1)
• Güler, Seval Hale(1)
• Güler, Ömer(1)
• Kalay, Ece(1)
• Sen Baykal, Duygu(1)
• Tekin, H.O.(1)
• Tekin, Huseyin Ozan(1)
• Yüzüak, Ercüment(1)
• Yüzüak, Gizem Durak(1)
• Şimşek, Tuncay(1)

• MakaleYalnız künye2026Scopus SJRQ2/r/munzur/1422
  Compositional control of structural, magnetic, and gamma-ray attenuation properties in rare-earth substituted Ho-based double perovskite oxides synthesized via mechanical alloying and oxidation

  Özkul, İskender; Kalay, Ece; Güler, Seval Hale; Karaduman, Oktay; Şimşek, Telem; Bülbül, Zeynel Abidin; Aksu Canbay, Canan; Sen Baykal, Duygu; ALMisned, Ghada; Tekin, H.O.

  Rare-earth substitution provides a route for tailoring the structural, magnetic, and gamma-ray attenuation behaviour of Ho-based Co-Mn double perovskites; however, the combined effects of rare-earth ionic size, magnetic character, and substitution level remain insufficiently understood. In this study, Ho1.5La0.5CoMnO6, Ho1.2Er0.8CoMnO6, Ho1.3Sm0.7CoMnO6, and Ho2CoMnO6 were synthesized through a two-step route involving mechanical alloying to obtain precursor powders, followed by annealing at 1000 °C in air to promote oxidation and double-perovskite phase formation. Their structural, thermal, surface-chemical, magnetic, and gamma-ray attenuation properties were examined by X-ray diffraction, thermal analysis, X-ray photoelectron spectroscopy, SEM-EDS, vibrating-sample magnetometry, and theoretical shielding calculations based on half-value layer (HVL) and transmission factor (TF) parameters. The XRD patterns were consistent with predominantly monoclinic P21/n type double-perovskite structures, while weak additional reflections suggested possible minor secondary phases. SEM-EDS showed homogeneous elemental distributions, and XPS analysis indicated Co2+ dominated and mixed Mn-valence characteristics in the spectra where reliable component analysis was possible. All compositions exhibited a low-temperature ferromagnetic-like field response but did not reach magnetic saturation at 3 T. Ho2CoMnO6 and Ho1.3Sm0.7CoMnO6 showed the highest field-dependent magnetization values at 10 K, whereas Ho1.2Er0.8CoMnO6 displayed the lowest response. The theoretical gamma-ray attenuation calculations showed clear composition-dependent differences. At 0.662 MeV, the HVL values were 1.0650, 0.9972, 1.0438, and 0.9967 cm for Ho1.5La0.5CoMnO6, Ho1.2Er0.8CoMnO6, Ho1.3Sm0.7CoMnO6, and Ho2CoMnO6, respectively. At the same photon energy and a thickness of 1.0 cm, the corresponding TF values were 0.0896, 0.0858, 0.0882, and 0.0860. Thus, Ho1.2Er0.8CoMnO6 and Ho2CoMnO6 exhibited the lowest HVL and TF values among the investigated compositions. The shielding calculations identified Ho1.2Er0.8CoMnO6 and Ho2CoMnO6 as the most effective attenuators, with lower HVL and TF values across the investigated energy range. These results show that rare-earth substitution enables compositional tuning of magnetic and theoretical gamma-ray attenuation behaviour, with the observed trends reflecting the combined influence of rare-earth ionic size, magnetic character, substitution level, and valence-state complexity.

  İncele
• Kitap BölümüYalnız künye2025/r/munzur/1649
  Magnetic energy conversion

  Yüzüak, Ercüment; Yüzüak, Gizem Durak; Dinçer, İlker; Elerman, Yalcin

  This paper provides a comprehensive and comprehensible analysis of the conversion of magnetic energy in magnetocaloric materials, as well as the application of magnetic refrigeration that relies on the magnetocaloric effect. The magnetocaloric effect (MCE) refers to the phenomenon of cooling or heating that takes place in a magnetic material when an external magnetic field is introduced or removed under adiabatic conditions. This effect also occurs in reverse, when the application or removal of an external magnetic field induces cooling or warming in the material. For a considerable period, the phenomena referred to as “adiabatic demagnetization” has been recognized, wherein the practical use of the magnetocaloric effect (MCE) in magnetic materials is observed. Magnetic materials exhibit the phenomenon known as the magnetocaloric effect close to their critical temperature. The magnetocaloric system exhibits superior environmental friendliness and efficiency compared to conventional refrigeration cycle systems that rely on vapor compression. Magnetic refrigeration is a cooling system that operates by utilizing the magnetocaloric effect. This methodology can be employed to achieve reduced temperatures, including those within the typical operational range of conventional refrigeration systems. In the realm of magnetic and electromagnetic energy conversion, the system's coefficient of performance (COP) attains a theoretical efficiency of 30%–60% of the Carnot cycle. The exploration of magnetic refrigeration is now underway, with a focus on utilizing low magnetic fields in the vicinity of room temperature. The objective is to facilitate the development of commercial devices that employ permanent magnets as the primary source of magnetic field. The utilization of a magnetocaloric heat pump in a magnetic refrigerator is employed as a cooling mechanism, relying on magnetocaloric materials. These materials present a promising substitute for conventional refrigeration technology that relies on compressors. Theoretical investigations have indicated that refrigeration systems utilizing the magnetocaloric effect have the potential to achieve energy efficiency levels that are around 35% higher compared to vapor compression systems. In addition, it should be noted that cooling systems utilizing magnetocaloric materials exhibit reduced noise levels as a result of the lack of a compressor. This particular technological approach involves the utilization of coolants that are water-based, as opposed to the conventional use of gaseous refrigerants.

  İncele
• MakaleAçık Erişim2025Scopus SJRQ2/r/munzur/891
  Multifunctional properties and microstructural correlations of NiCoMnTi-Based high entropy alloys with focus on magnetic, thermodynamic, and radiation shielding characteristics

  Özkul, İskender; Karaduman, Oktay; Şimşek, Tuncay; Şimşek, Telem; Canbay, Canan Aksu; Güler, Ömer; ALMisned, Ghada; Baykal, Duygu Sen; Tekin, Huseyin Ozan

  High-entropy alloys (HEAs) are a novel class of materials known for their complex compositions and exceptional multifunctional properties. In this study, NiCoMnTi-based HEAs were modified with Fe, Cr, and Cu as fifth elements to systematically investigate their structural, magnetic, thermodynamic, and nuclear radiation shielding characteristics. The alloys were synthesized via arc melting and characterized using XRD, SEM-EDS, VSM, and theoretical modeling methods. The findings reveal that each additional element uniquely alters the alloy’s properties. The Fe-containing alloy exhibited a well-defined lamellar microstructure, the highest saturation magnetization (10.79 emu/g), and a Curie temperature near 450 K, along with strong gamma-ray shielding performance across both low and high energy ranges. The Cr-containing alloy demonstrated soft magnetic behavior, featuring the lowest coercivity (29.64 Oe) and the highest fast neutron removal cross-section. In contrast, the Cu-containing alloy enhanced low-energy photon attenuation due to its higher atomic number but exhibited limited magnetic homogeneity. Despite these differences, all samples displayed stable thermodynamic behavior and comparable buildup factor trends. Overall, the addition of Fe led to a synergistic improvement in both magnetic and radiation shielding capabilities of the NiCoMnTi-based HEA system.

  AtıfScopus3·OpenAlex3

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