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- MakaleYalnız künye2026Scopus SJRQ2Oxide Dispersion, Microstructure, and Functional Evolution in La2O3 Modified Cu-Al-Mn-Fe Shape Memory Alloys
Karaduman, Oktay; Doğan, Fatih; Dehghanpour, Heydar; Yüzüak, Gizem Durak; Yüzüak, Ercüment; Canbay, Canan Aksu
Cu-Al-Mn-Fe high-temperature shape memory alloys containing 0-1.0 wt.% La2O3 were fabricated by vacuum arc remelting to investigate oxide-dispersion effects on microstructure, martensitic transformation, wear, and corrosion behavior. XRD and SEM analyses revealed that low La2O3 additions (0.2-0.4 wt.%) promoted β1′ martensite refinement and enhanced crystallinity, while higher contents induced structural heterogeneity. The alloy with 0.4 wt.% La2O3 exhibited the highest transformation enthalpy (7.49 J g−1), reduced friction coefficient (~0.55), and the narrowest wear scar (~501 µm). Electrochemical tests in 3.5 wt.% NaCl showed a fivefold decrease in corrosion current density and increased charge-transfer resistance (2512 Ω cm2) for the same composition. Excessive La2O3 led to performance degradation due to particle agglomeration and interfacial defects. The results demonstrated that controlled La2O3 addition enabled microstructural refinement and multifunctional performance enhancement in Cu-based shape memory alloys.
- MakaleAçık Erişim2026Scopus SJRQ2Engineering Superior Soft Magnetic Properties Through FeCo/Cr and FeCo/Fe Nanocrystalline Architectures
Yüzüak, Gizem Durak
Soft magnetic materials are integral to various technologies, including high-frequency transformers, spintronic devices, and magnetic sensors, because of their low coercivity (HC) and high magnetization. This study investigates nanocrystalline Fe70Co30(100 nm)/Cr(2-10 nm) and Fe70Co30(100 nm)/Fe(2-10 nm) thin films, deposited via magnetron sputtering. X-ray diffraction analysis reveals that Fe70Co30 films without buffer layers crystallize in a body-centered cubic phase. The Cr and Fe buffer layers enhance it by minimizing lattice mismatch and promoting a uniform crystalline growth of the Fe70Co30 layer. The most significant particle size variations observed were approximately 24% for the Cr buffer and 31% for the Fe buffer. Microstructural characterization using atomic force microscopy and scanning electron microscopy identified nanograins with an average size of 30–80 nm. Magnetic characterization with a vibrating sample magnetometer showed a marked reduction in HC. Additionally, the remanence-to-saturation magnetization ratio remains nearly constant at 0.95 across all Fe-buffered films, whereas it increases from 0.80 to 0.92 in Cr-buffered films as the Cr thickness increases. The results highlight the importance of buffer layer engineering in enhancing the microstructural and magnetic properties of FeCo thin films, thereby increasing their suitability for advanced magnetic technologies.
- Kitap BölümüYalnız künye2025Magnetic 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.
- MakaleYalnız künye2025Scopus SJRQ1Modifying the magnetic characteristics of ferrimagnetic TbFeCo by adjusting the thickness of the L11-ordered CoPt
Yüzüak, Gizem Durak
This study investigates structural and magnetic properties of 200 nm TbFeCo ferrimagnetic thin films. These films were formed by depositing L11-ordered CoPt buffer layers on Si(100) substrates, followed by (111)-textured Pt layers. The TbFeCo films were produced at room temperature by magnetron sputtering, and their characteristics were analyzed using X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), vibrating sample magnetometry (VSM), atomic force microscopy (AFM), and magnetic force microscopy (MFM). The above-mentioned techniques were used to figure out the films’ crystallographic structure, magnetic properties, and the surface characteristics. XRD analysis showed that TbFeCo films without the CoPt layer were only crystalline in the Pt(111) and Pt(222) directions. Conversely, films that were buffered with a CoPt layer developed the L11-ordered CoPt phase, especially in the CoPt(222) and CoPt(444) directions. This issue was linked to an increase in the CoPt unit cell parameter, indicating bulk-like crystallinity, particularly in the 20 nm CoPt layer, while the TbFeCo layer remained amorphous. The FIB-SEM showed that the layers were all gathered the thickness of 20 nm for Pt, 10 or 20 nm for CoPt, and 200 nm for TbFeCo with homogeneous distributed the elements in the Tb46Fe41Co13 composition matrix. Magnetic characterization from VSM measurements ranged from 5 to 350 K and revealed significant differences based on CoPt thickness. At 300 K, the coercive field (HC) got stronger as the thickness of the CoPt layer risen up. For 0, 10, and 20 nm CoPt, the HC was 2.8, 3.3, and 4.1 kOe, and the MS values were about 205, 229, and 234 emu/cm³, respectively. The L11-ordered CoPt underlayer facilitated strong exchange coupling at the TbFeCo/CoPt interface, which is responsible for these improvements. AFM and MFM measurements indicated that surface roughness, and hence magnetic pinning sites, increased dramatically with CoPt thickness. These pinning sites inhibited magnetic domain wall motion, increasing HC values in the out-of-plane direction. This kind of magnetic stability leads to excellent qualities, like higher HC and better thermal stability up to 350 K, that make these films interesting for use in spintronics and data storage, where HC and thermal resilience are important.
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İncele - BildiriYalnız künye2024Exploring Triboelectric Properties in Sputtered Si(100)/SiO2/Cr/ZnO Thin Films - Ag/FEP Using Contact Speration Technique for Renewable Energy Harvesting
Yüzüak, Gizem Durak; Benhala, B.; Raihani, A.; Qbadou, M.
Currently, there is an ongoing inquiry into triboelectric nanogenerators (TENG), which use the triboelectric phenomenon to capture electrical energy from mechanical vibrations. The work aims to figure out the magnetron sputtered Cr/ZnO-based films on SiO2/Si(100) substrates with the construction of a Cr/ZnO-Ag/FEP tribo-based nanogenerator (TENG) and a specific emphasis on measuring TENG properties. The structural investigation of these films was conducted using X-ray diffraction (XRD) photoluminescence (PL), attenuated total reflectance fourier-transform infrared spectroscopy (AT-FTIR), and current - voltage (I-V) analysis in contact-separation mode (CSM). The Cr/ZnO-Ag/FEP TENG has a notable instantaneous maximum output voltage of around 63 V and a current density of 7 μA/cm2 when compared to other nanogenerators based on semiconductors, as determined by a comparative analysis. The results of this study provide useful information on the possible application of optimized magnetron sputtered Cr/ZnO-based films in triboelectric and energy harvesting systems, which might contribute to the progress of sustainable and renewable energy technologies.
- MakaleYalnız künye2024Scopus SJRQ2Optimizing the thermoelectric performance of Bi-Sb-Te thin films through compositional engineering
Yüzüak, Gizem Durak; Çetin, Mehmet; Yüzüak, Ercüment
The objective of the present investigation was to systematically investigate the structural and thermoelectric (TE) properties of BixSb2-xTe3 thin films with varying content of Bi. We investigated the impact of different atomic percentages of Bi (4, 6, 8 at. %) on the properties of carrier transport and TE performance. In general, the Seebeck coefficient remained consistent across the thin films. For the 8 at. % Bi thin film, the Seebeck coefficient and electrical conductivity were measured at 230 μV/K and 730 S/cm, respectively, at room temperature. These values were more than 20 times greater than the electrical conductivity observed in the thin films with compositions of 6 and 4 at. % Bi. As a result, the Bi-Sb-Te compound exhibited a TE power factor (PF) of 38x10−4 W/mK2 at 40 °C, surpassing the PFs observed in previous compositions. The analysis of surface microstructure, combined with atomic force microscopy and Kelvin probe microscopy images, revealed that the transport of carriers in films with high Bi content was impeded by the size of particles and scattering sites. On the other hand, an augmentation in Bi content promoted the transfer of charge through crystalline regions, hence improving the mobility of carriers and the total electrical conductivity. The aforementioned results emphasize the significant influence of Bi content on the electrical properties of semiconductors and demonstrate the effectiveness of compositional engineering based on Bi content in the development of TE materials with superior performance. The present study investigates the influence of Bi content on the electrical properties of Bi-Sb-Te thin films, demonstrating that compositional adjustments based on Bi content can impact the performance of TE materials. These findings contribute to the understanding of material optimization in the field of TE.
AtıfScopus4WoS5OpenAlex5İncele - MakaleYalnız künye2024Scopus SJRQ1Preparation and characterization of the highly efficient tetraphenylimidazole substituted Phthalocyanine/ZnO composite and investigation of its effect on the photocatalytic degradation of Rhodamine B and 2,4,6-trichlorophenol
Karaoğlu, Kaan; Yüzüak, Gizem Durak; Yüzüak, Ercüment; Turan, Hanife; Akçay, Hakkı Türker
Growing concerns about industrial waste-induced environmental degradation have driven research towards sustainable solutions. Photocatalytic degradation, fueled by light and avoiding harmful chemicals, offers a promising avenue due to its minimal environmental impact. ZnO, TiO₂, and their derivatives are particularly effective and widely studied photocatalysts. This study aims to prepare new composite materials bearing phthalocyanine and investigate the photocatalytic properties on the degradation of Rhodamine B dye and 2,4,6-trichlorophenol (TCP) as the model compounds. In the initial step, ZnO materials were synthesized using the solvothermal method. Subsequently, a novel Zn(II) complex, including peripherally tetra phenyl imidazole substituted phthalocyanine, was successfully prepared. The composite catalysts were prepared from ZnO materials produced with the tetraphenyl imidazole phthalocyanine Zn(II) complex, called TFI-Zn. The were characterized using instrumental techniques. The photocatalytic characteristics of the composite materials developed were further examined under varying quantities of catalyst and Rhodamine B, variable pH conditions, and varying intensities of UV-A light. In addition, the reusability of the catalyst was investigated. With the new composite photocatalyst prepared within the scope of this study, 98% degradation efficiency and 8.0 × 10−4 min−1 degradation rate was obtained on Rhodamine B solution in 40 min. The newly developed photocatalyst displayed remarkable catalytic activity that remained virtually unchanged for five consecutive cycles, indicating excellent reusability and operational stability. The photocatalytic degradation performance of ZnO-TFI-Zn (1) was also examined on TCP and 90% degradation activity was obtained at the end of 80 min.
AtıfScopus7WoS7OpenAlex7İncele - MakaleAçık Erişim2023Reclaim of Wrecked Bi-Te Based Materials In Peltier Modules In Thermopower Properties By Mechanical Milling
Yüzüak, Ercüment; Cetin, Mehmet; Yüzüak, Gizem Durak
We thoroughly evaluated the effects of various treatments on the structural and electrical properties of the two as-cast materials, “Sb-doping Bi-Te (p-type)” and “Se-doping Bi-Te (n-type)” which are frequently present in abandoned Peltier modules. To investigate the thermoelectric properties of Bi2Te3-based materials, waste alloys characterized by electrical conductivity using the hot-end method. Alloys were purified by performing arc melting on a water-cooled copper crucible in a vacuum of at least 10-3 mbar, with five times melting sessions to assure homogeneity. A single and long milling period of 144 hours is applied. After the compressing operation, the resulting discs with nanostructures were annealed for an hour at 600 K under vacuum conditions. The discs' structural properties were characterized using X-ray diffraction (XRD) and their surfaces and stoichiometries were determined using scanning electron microscopy with an energy dispersive feature. The Seebeck coefficient of the nanoparticle formed n-type Bi-Te based sample is -35.3 μV.K-1 and p-type Bi-Te based sample is 100 μV.K-1 (15% of mean error margin). It was found that a notable improvement was attained in comparison to the initial state with the addition of nanoparticles.
- MakaleAçık Erişim2023Self-Powered Mechanical Energy Sensor Application of SnO2/Ag and PMMA/ITO Nanocomposites via Triboelectric Effect
Yüzüak, Ercüment; Cetin, Mehmet; Yüzüak, Gizem Durak
The triboelectric nanogenerator is a state-of-the-art device for addressing the growing problem of meeting the world's ever-increasing energy needs by converting mechanical energy into electrical energy. Using the popular semiconductor SnO2 nanostructured thin films as a triboelectric layer over contact regions, as opposed to polymers with lesser performance, increases the output power and life time of nanogenerators. In order to design a triboelectric nanogenerator, deposited thin film SnO2 is used as a friction layer with Ag electrode after heat-treatment at 623 K with a contrary layer of PMMA poly (methyl-methacrylate) with ITO electrode. The structural and electrical properties were analyzed by using scanning electron microscopy (SEM), electro-impedance spectroscopy (EIS) and atomic force microscopy (AFM) measurements. The increased output power of the triboelectric nanogenerator is attributed to the nanoscale PMMA contact charge created by tunneling electrons in the SnO2/Ag nanocomposite thin film layer. Due to its proximity to the PMMA/ITO surface, the SnO2/Ag layer causes electron field emission, and tapping the SnO2/Ag layer may result in electron cloud overlap. Similar to a semiconductor/insulator interface, the Fermi level of SnO2 plays a crucial role in electron transport. The system efficiency stated as a touch detector in a conventional keyboard that generates its own power is revealed in part by an analysis of its operating state up to the 4V.
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