Person: KÜÇÜK, NİL
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KÜÇÜK
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NİL
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Publication Synthesis and characterization of graphene nanoplatelet-La₀.₇Ca₀.₃MnO₃ composites(Taylor & Francis, 2019-07-11) Küçük, İlker; Tekgül, Atakan; Sarlar, Kağan; Civan, Ersin; Küçük, Nil; Macan, Barış; KÜÇÜK, İLKER; Tekgul, Atakan; Sarlar, Kağan; KÜÇÜK, NİL; Macan, Barış; Fen Edebiyat Fakültesi; Fizik Bölümü; 0000-0001-6737-3838; 0000-0002-8871-2357; 0000-0002-9193-4591; AAI-6808-2021; P-2124-2016; B-8159-2016; GXN-2736-2022; CCH-1761-2022; DGC-7162-2022La₀.₇Ca₀.₃MnO₃ perovskite and its composites with graphene nanoplatelet (GNP) were prepared using a wet chemical method. The structural, magnetic and magnetocaloric properties of La₀.₇Ca₀.3MnO₃: GNP composites were investigated to determine the effect of GNPs. The results of XRD analysis show that the synthesised powders can be almost indexed to pure phase orthorhombic La₀.₇Ca₀.₃MnO₃. The magnetic measurements demonstrate that 0.7 and 1% GNP amounts cause an increase in the Curie temperature (T-C), and for larger amounts of GNP, the T-C monotonically decreases, except for the sample with 10% GNP. The results obtained from the Arrott plots show that the magnetic phase transition of the samples transforms from the first to second order with increasing GNP amount. The changes in the magnetocaloric properties are interpreted in terms of perovskite phase formations via structural analysis. The amounts of graphene nanoplatelets in the oxide powders are correlated with the observed magnetocaloric properties. The best magnetocaloric performance with the maximum magnetic entropy change of 3.99 Jkg(-1)K(-1) and refrigeration capacity of 90 Jkg(-1) was obtained at a 2 T magnetic field.Publication The structural, magnetic and magnetocaloric properties of mncrnigesi high-entropy alloy(Iop Publishing Ltd, 2022-07-01) Sarlar, Kağan; KÜÇÜK, NİL; ETEMOĞLU, AKIN BURAK; Tekgül, Atakan; Mühendislik Fakültesi; Fizik Bölümü; 0000-0001-6737-3838; 0000-0002-8871-2357; 0000-0002-9193-4591; 0000-0001-8022-1185; ABE-9423-2020; GXN-2736-2022; AAI-6808-2021; P-2124-2016The structural, magnetic and magnetocaloric properties of Mn20Cr14Ni33Ge25Si8 and Mn24Cr10Ni33Ge25Si8 high entropy alloys (HEAs) were investigated. The HEAs were prepared by arc melting method. The structural analysis indicates that the structure of HEAs is orthorhombic with Pnma space group. In magnetic measurements, the maximum saturation magnetization was found to be 56.7 A m(2)kg(-1). The Curie temperature of HEAs is 361 and 387 K, respectively. The Curie temperature shifts to the high temperature, when 4% Mn is added, resulting the long-range orientation of the magnetic moments. The magnetic entropy change of Mn24Cr10Ni33Ge25Si8 is 3.6 Jkg(-1)K(-1) at around 387 K. Consequently, Large magnetic entropy change is achieved with low hysteresis and soft magnetic property at high temperature.Publication Comparative studies on thermoluminescence characteristics of non-doped Mg 2 SiO 4 prepared via a solid-state reaction technique and wet-chemical method: An unusual heating rate dependence(Elsevier, 2019-07-30) Doğan, T.; Akça, S.; Yüksel, M.; Küçük, Nil; Ayvacıklı, M.; Karabulut, Y.; Canımoglu, A.; Topaksu, M.; Can, N.; KÜÇÜK, NİL; Fen Edebiyat Fakültesi; Fizik Bölümü; 0000-0002-9193-4591; AAI-6808-2021Magnesium orthosilicate (Mg2SiO4) was synthesized via a traditional solid-state reaction and a wet chemical route. This study primarily reported the thermoluminescence (TL) behavior of Mg2SiO4 host. X-ray diffraction pattern revealed that Mg2SiO4 exhibits orthorhombic structure matched with JCPDS card 900-6398. Dose response, reproducibility and trap parameters of TL glow curves were evaluated to clearly reveal TL features. Two TL glow peaks situated at 81 degrees C and 192 degrees C were monitored at a heating rate of 2 degrees Cs-1. We observed anomalous heating rate effect for the peak centered at 192 degrees C whilst TL intensity of the peak at 81 degrees C decreases with elevating heating rate. Trap depths of the electrons within the trap centers were found to be 1.04 +/- 0.01eV and 1.37 +/- 0.01eV for both methods using peak shape (PS) method. Distribution of trap centers was examined using the T-max - T-stop method and this case indicated that the glow curves consist of single TL peaks. The intensity of TL glow curves exhibited a good linear dose response under total area up to 20 Gy. A comparison of the two preparation techniques revealed that TL characteristics of this phosphor are partly dependent and Mg2SiO4 could be a promising material for dosimetric application. (C) 2019 Elsevier B.V. All rights reserved.Publication Thermoluminescence characteristics of terbium doped zinc borates(Mdpi, 2019-10-23) Küçük, Nil; KÜÇÜK, NİL; Fen Edebiyat Fakültesi; Fizik Bölümü; 0000-0002-9193-4591; AAI-6808-2021In this work, structural and thermoluminescence (TL) characteristics for ZnB2O4:xTb(3+) (x = 0.01, 0.02, 0.03, 0.04, 0.05, and 0.10 mole) phosphors were investigated. The phosphors were prepared via synthesis of nitric acid. The X-ray diffraction (XRD) studies show that the synthesized samples can be indexed to nearly single-phase cubic ZnB2O4. The TL characteristics following Sr-90 beta irradiation (40 mCi) were studied. TL intensity is found to depend on Tb concentration. The optimal concentration of the doped Tb3+ is 0.03 mol in TL measurements. TL dose responses of the phosphors to beta doses of 0.143, 0.715, 1.43, 15, 30 and 60 Gy showed fairly linear behavior. The minimum detectable dose (MDD) value for ZnB2O4:0.04Tb(3+) was found to be 87 mGy. The kinetic parameters of the ZnB2O4:0.03Tb(3+) sample were estimated by the glow curve deconvolution, the initial rise, the curve fitting, and the peak shape methods. The results indicate that these phosphors are thought to be promising candidates as TL materials. The results provide valuable knowledge of the characteristics of Tb-doped ZnB2O4 for use in dosimetry research.Publication Structural and magnetocaloric properties of feni high entropy alloys(IOP Publishing, 2021-12-01) Sarlar, Kağan; Tekgül, Atakan; Küçük, Nil; Etemoğlu, Akın Burak; Tekgül, Atakan; KÜÇÜK, NİL; ETEMOĞLU, AKIN BURAK; Mühendislik Fakültesi; Fizik Bölümü; 0000-0001-6737-3838; 0000-0002-9193-4591; 0000-0001-8022-1185; ABE-9423-2020; GXN-2736-2022; AAI-6808-2021In this study, a new Fe30.7Ni25.7Ga14.6Mn19Si10 without rare earth element high entropy alloy's (HEA) magnetocaloric properties was investigated. The HEA was formed by the suction-casting method. x-ray diffraction (XRD) method was performed for structural analysis. XRD analysis show that both the as-quenched and annealed alloy have a single body centred cubic(bcc) structure. The result obtained from the Arrott plots indicates that the alloys have the second order magnetic phase transition. The transition temperature from paramagnetic to ferromagnetic transition was observed at 442 K and 462 K for the as-quenched and annealed alloy, respectively. The Fe30.7Ni25.7Ga14.6Mn19Si10 HEA shows magnetic entropy change such as 0.75 Jkg(-1) K-1 for as-quenched alloy, 0.90 Jkg(-1) K-1 for annealed alloy at 2 T magnetic field.