Browsing by Author "Ekicibil, Ahmet"

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Effect of Ho Substitution on Structural, Magnetic and Magnetocaloric Properties of Co(crfe)o-4
(SPRINGER, 2021) Kıvrak, Burak; Gülkesen, Semiramis; Ayaş, Ali Osman; Akyol, Mustafa; Ekicibil, Ahmet
In this study, structural, magnetic and magnetocaloric properties of Ho-substituted Co(CrFe)O-4 spinel compounds produced by the sol-gel method were investigated. The Ho concentration in Co(CrFe)O-4 spinel structure was changed from 0 to 20% by 5% steps. It is observed that the Ho3+ ions create a new phase HoCrO3/HoFeO3 in the host spinel lattice. SEM images of samples indicate that the average particle size increases with Ho content. The paramagnetic to ferro-/ferrimagnetic phase transition temperature increases from 312 to 344 K with Ho content. While the fluctuation in saturation magnetization of samples was detected at low temperature, it almost becomes a linear change with the Ho content. The maximum magnetic entropy change under 7 T magnetic field was found as - 1.39, - 1.50, - 1.20, - 0.98 and - 0.91 J/kgK for Ho-free, 5, 10, 15 and 20 wt% Ho content in CoCrFeO4 spinel structure, respectively.
Citation - WoS: 3
Citation - Scopus: 3
Investigation of Structural and Magnetic Characteristic of Pure and M-Doped (m: Fe and Cu) Mos2 Thin Films
(Springer, 2022) Kıvrak, Burak; Akyol, Mustafa; Ekicibil, Ahmet
In this study, structural and magnetic properties of pure and M-doped MoS2 (M: Fe and Cu) thin film were investigated. Two-step film growing process were used to create a thin film which are (i) spin coating and (ii) thermal decomposition. Raman spectroscopy results indicate that two characteristic vibration modes of E-2(g)1 (in-plane) and A(18) (out-of-plane) 2H MoS2 were observed in all samples. The surface morphology of samples studied by scanning electron microscopy (SEM) images shows that MoS2 crystals formed a back-to-back triangle shape. However, the triangle-shaped grains transform to nanorods when M is doped into the MoS2. Pure and Fe-doped samples show magnetic transition temperatures at similar to 247 and 95.5 K, respectively. In constrast, the Cu-doped sample shows strong diamagnetic characteristics in measurements. In addition, the magnetization values increase with the introduction of the Fe atoms into the main structure. According to the magnetic hysteresis curves of samples, pure and Fe-doped samples show ferromagnetic characteristics, while the Cu-doped sample shows weak magnetic characteristics in both 5 and 300 K.
Citation - WoS: 13
Citation - Scopus: 15
Synthesis and Characterization of Nanoparticles Reinforced Epoxy Based Advanced Radar Absorbing Composites
(SPRINGER, 2021) Tümen, Kutluhan Utku; Kıvrak, Burak; Alkurt, Fatih Ozkan; Akyol, Mustafa; Karaaslan, Muharrem; Ekicibil, Ahmet
In this study, the structural and magnetic properties of NixCo1-xFe2O4 (0.0 <= x <= 1.0) and ZnO nanoparticles synthesized by the sol-gel method were investigated. The microwave property of the composite structures produced from the combination of ZnO and NixCo1-xFe2O4 nanoparticles dispersed in the epoxy matrix property was studied in the X-band frequency range. The crystal structures of NixCo1-xFe2O4 have not been disrupted by Ni substitution, however, the lattice parameters of samples decrease due to the smaller ionic radii of Ni+2 compared to Co+2 ions. The magnetic saturation (M-s) and remanence magnetization (M-r) decreased with an increasing amount of Ni in NixCo1-xFe2O4 structure. According to the microwave absorption properties of samples, the maximum reflection loss (RL) value was found as -28.10 dB at 10.23 GHz frequency in RAC(4) sample. On the other hand, maximum bandwidth was found at 2.95 GHz around -10 dB for RAC5 sample. All composites exhibit efficient RL in the X-band indicating that they can be used in potential applications in aviation, radar, and defense vehicles.