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Now showing 1 - 10 of 56
  • Article
    Citation - WoS: 9
    Citation - Scopus: 9
    Sr addition and its effect on the melt cleanliness of A356
    (Iop Publishing Ltd, 2020) Atakav, Baturalp; Gursoy, Ozen; Erzi, Eray; Tur, Kazim; Dispinar, Derya
    Strontium modification of Al-Si alloys has known to have several beneficial effects such as increased feedability, the formation of fibrous Si and increased mechanical properties. However, in the presence of Sr, during melting and holding durations, the oxide structure of the dross may change which leads to several problems during casting operations. In this work, the amount of Sr was changed and the melt was held for 1 h. Reduced Pressure Test (RPT) was used to asses melt quality change and it was found that cleanliness was increased due to the fading of Sr.
  • Article
    Citation - Scopus: 1
    Samarium and Yttrium Doping Induced Phase Transitions and Their Effects on the Structural, Optical and Electrical Properties of Nd2sn2< Ceramics
    (Iop Publishing Ltd, 2019) Saleh, Adli A.; Qasrawi, A. F.; Hamamera, Hanan Z.; Khanfar, Hazem K.; Yumusak, G.
    In this work, the effects of Sm+3 and Y+3 doping onto the structural, optical and electrical properties of Nd2Sn2O7 are investigated. An atomic content of 3.49% and 4.29% of Sm and Y, respectively, were sufficient to alter the physical properties of the Nd2Sn2O7. Particularly, the Y+3 ionic substitution decreased the lattice constant, narrows the energy band gap, changed the conductivity type from n- to p- type and increased the electrical conductivity by 73 times without changing the cubic nature of structure of the pyrochlore ceramics. On the other hand, Sm+3 ionic substitutions changed the cubic structure to hexagonal or trigonal and forced optical transitions in the infrared range of light. The energy band gap shrunk from 3.40 to 1.40 eV, the defect density is reduced and the electrical conductivity increased by 47 times via Sm doping. These doping agents' makes the neodymium stannate pyrochlore ceramics more appropriates for optoelectronic applications.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 7
    Construction of Self-Assembled Vertical Nanoflakes on Cztsse Thin Films
    (Iop Publishing Ltd, 2019) Terlemezoglu, M.; Surucu, O. Bayrakli; Colakoglu, T.; Abak, M. K.; Gullu, H. H.; Ercelebi, C.; Parlak, M.
    Cu2ZnSn(S, Se)(4) (CZTSSe) is a promising alternative absorber material to achieve high power conversion efficiencies, besides its property of involving low-cost and earth-abundant elements when compared to Cu(In, Ga) Se-2 (CIGS) and cadmium telluride (CdTe), to be used in solar cell technology. In this study, a novel fabrication technique was developed by utilizing RF sputtering deposition of CZTSSe thin films having a surface decorated with self-assembled nanoflakes. The formation of nanoflakes was investigated by detailed spectroscopic method of analysis in the effect of each stacked layer deposition in an optimized sequence and the size of nanoflakes by an accurate control of sputtering process including film thickness. Moreover, the effects of substrate temperature on the formation of nanoflakes on the film surface were discussed at a fixed deposition route. One of the main advantages arising from the film surface with self-assembled nanoflakes is the efficient light trapping which decreases the surface reflectance. As a result of the detailed production and characterization studies, it was observed that there was a possibility of repeatable and controllable fabrication sequence for the preparation of CZTSSe thin films with self-textured surfaces yielding low surface reflectance.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Dispersive Optical Constants of Tl2ingase4< Single Crystals
    (Iop Publishing Ltd, 2007) Qasrawi, A. F.; Gasanly, N. M.
    The structural and optical properties of Bridgman method grown Tl2InGaSe4 crystals have been investigated by means of room temperature x-ray diffraction, and transmittance and reflectance spectral analysis, respectively. The x-ray diffraction technique has shown that Tl2InGaSe4 is a single phase crystal of a monoclinic unit cell that exhibits the lattice parameters of a = 0.77244 nm, b = 0.64945 nm, c = 0.92205 nm and beta = 95.03 degrees . The optical data have revealed an indirect allowed transition band gap of 1.86 eV. The room temperature refractive index, which was calculated from the reflectance and transmittance data, allowed the identification of the dispersion and oscillator energies, static dielectric constant and static refractive index as 28.51 and 3.45 eV, 9.26 and 3.04, respectively.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Structural and Dielectric Performance of the Ba(zn1/3< Perovskite Ceramics
    (Iop Publishing Ltd, 2019) Qasrawi, A. F.; Sahin, Ethem Ilhan; Emek, Mehriban; Kartal, Mesut; Kargin, Serdar
    In this work, we have explored the antimony doping effects on the structural and dielectric properties of Ba(Zn1/3Nb2/3)O-3 ceramics (BZN). The ceramics displayed perovskite structures with a lattice constant that decreases with increasing Sb content. The antimony solubility limit of the BZN ceramics is x < 0.50. Belowthis limit and in the range of 0.30 <= x <= 0.40, the microstrain, the dislocation density and the stacking faults decreased and the crystallite size increases with increasing Sb content in the composition of BZN. When the limit is exceeded minor phases are predicted by software analysis and confirmed by the experimental techniques. The presence of these phases is also verified by the scanning electron microscopy and energy dispersive x-ray spectroscopy techniques. Increasing the Sb content is observed to decrease the value of the dielectric constant. The Sb doped BZN ceramics exhibits high dielectric quality factors that nominate it for applications in electronics as radio waves resonators.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Electron-Lattice Interaction Scattering Mobility in Tl2ingase4< Single Crystals
    (Iop Publishing Ltd, 2008) Qasrawi, A. F.; Gasanly, N. M.
    In this work, the dark electrical resistivity, charge carrier density and Hall mobility of Tl(2)InGaSe(4) single crystal have been recorded and analyzed to investigate the dominant scattering mechanism in the crystal. The data analyses have shown that this crystal exhibits an extrinsic n-type conduction. The temperature-dependent dark electrical resistivity analysis reflected the existence of two energy levels as 0.396 and 0.512 eV, being dominant above and below 260 K, respectively. The temperature dependence of the carrier density was analyzed by using the single-donor-single-acceptor model. The latter analysis has shown that the above maintained 0.512 eV energy level is a donor impurity level. The compensation ratio for this crystal is determined as 0.96. The Hall mobility of Tl(2)InGaSe(4) is found to be limited by the scattering of electron-acoustic phonon interactions. The calculated theoretical acoustic phonon scattering mobility agrees with the experimental one under the condition that the acoustic deformation potential is 12.5 eV.
  • Article
    Citation - WoS: 15
    Citation - Scopus: 16
    Electrical Parameters of Al/Inse Rf Sensors
    (Iop Publishing Ltd, 2014) Qasrawi, A. F.
    An Al/InSe/C Schottky device is designed on the surface of amorphous InSe thin films. The device is observed to exhibit a switching property at particular biasing voltages. The 'on/off' current ratio is found to be 7.9 and 9.3 at forward and reverse biasing voltages of 2.0 and 2.25 V, respectively. The 'off' and 'on' operational modes are ascribed to the domination of the tunneling of charged particles through a barrier height of 0.83 eV with a depletion region width of 64 nm and due to the domination of the thermionic emission of charged carriers over a barrier height of 0.53 eV, respectively. In addition, the spectral analysis of the capacitance of the device which was carried in the frequency range of 10.0 k-3.0 GHz reflected dc voltage biasing-dependent high quality resonating peaks. The strongest one appeared at a frequency of 36.8 MHz for a biasing voltage of 0.70 V. Furthermore, the loss tangent of the Al/InSe/C device is found to be of the order of 10(-7) at 3.0 GHz. Consistently, the capacitance-voltage spectra of these sensors reflected pronounced tunability up to 100 MHz. The Al/InSe/C device performance, the switching properties and the quality of the resonance peaks indicate the possibility of using these sensors in RF technology.
  • Article
    Citation - WoS: 20
    Citation - Scopus: 20
    Properties of the Pc(4312) pentaquark and its bottom partner
    (Iop Publishing Ltd, 2021) Azizi, K.; Sarac, Y.; Sundu, H.
    We present an analysis of the newly observed pentaquark P-c(4312)(+) to shed light on its quantum numbers. To do that, the QCD sum rules approach is used. The measured mass of this particle is close to the Sigma D-++(c)- threshold and has a small width, which supports the possibility of its being a molecular state. We consider an interpolating current in a molecular form and analyze both the positive and negative parity states with spin-. We also consider the bottom counterpart of the state with similar molecular form. Our mass result for the charm pentaquark state supports that the quantum numbers of the observed state are consistent with J(P) = 1/2(-).
  • Article
    Citation - WoS: 13
    Citation - Scopus: 15
    Induced Scattering Limits on Fast Radio Bursts From Stellar Coronae
    (Iop Publishing Ltd, 2016) Lyubarsky, Yuri; Ostrovska, Sofiya
    The origin of fast radio bursts remains a puzzle. Suggestions have been made that they are produced within the Earth's atmosphere, in stellar coronae, in other galaxies, or at cosmological distances. If they are extraterrestrial, the implied brightness temperature is very high, and therefore the induced scattering places constraints on possible models. In this paper, constraints are obtained on flares from coronae of nearby stars. It is shown that the radio pulses with the observed power could not be generated if the plasma density within and in the nearest vicinity of the source is as high as is necessary to provide the observed dispersion measure. However, one cannot exclude the possibility that the pulses are generated within a bubble with a very low density and pass through the dense plasma only in the outer corona.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Optoelectronic Properties of Ga4se3< Single Crystals
    (Iop Publishing Ltd, 2008) Qasrawi, A. F.; Gasanly, N. M.; Ilaiwi, K. F.
    The optoelectronic properties of Bridgman method-grown Ga(4)Se(3)S single crystals have been investigated by means of room temperature electrical resistivity, temperature-dependent photosensitivity and temperature-dependent optical absorption. The photosensitivity was observed to increase with decreasing temperature, the illumination dependence of which was found to exhibit monomolecular recombination in the bulk at 300 K. The absorption coefficient, which was calculated in the incident photon energy range of 2.01-2.35 eV, increased with increasing temperature. Consistently, the absorption edge shifts to lower energy values. The fundamental absorption edge corresponds to an indirect allowed transitions energy gap (2.08 eV at 300 K) that exhibits a temperature coefficient of -95 x 10(-4) eVK(-1).