Chemical Engineering / Kimya Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/14

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Subject: search.filters.subject.Zinc

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Now showing 1 - 4 of 4
  • Article
    Citation - WoS: 12
    Citation - Scopus: 14
    Zinc Electrode Morphology Evolution in High Energy Density Nickel-Zinc Batteries
    (Hindawi Publishing Corporation, 2016) Payer, Gizem; Ebil, Özgenç
    Prismatic Nickel-Zinc (NiZn) batteries with energy densities higher than 100 Wh kg-1 were prepared using Zn electrodes with different initial morphologies. The effect of initial morphology of zinc electrode on battery capacity was investigated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) reveal that initial morphology of zinc electrode changes drastically after a few charge/discharge cycles regardless of initial ZnO powder used. ZnO electrodes prepared using ZnO powders synthesized from ZnCl2 and Zn(NO3)2 lead to average battery energy densities ranging between 92 Wh kg-1 and 109 Wh kg-1 while using conventional ZnO powder leads to a higher energy density, 118 Wh kg-1. Average discharge capacities of zinc electrodes vary between 270 and 345 mA g-1, much lower than reported values for nano ZnO powders in literature. Higher electrode surface area or higher electrode discharge capacity does not necessarily translate to higher battery energy density.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 12
    The Effect of Zn Substitution of Ca in Bipbsrcacuo Superconductors Sintered at 830°c
    (Springer Verlag, 2009) Kocabaş, Kemal; Şakiroğlu, Serpil; Çiftçioğlu, Muhsin; Ercan, İsmail; Epik, Hakan; Bilgili, Özlem
    The effect of partial substitution of Ca by Zn in Bi 1.7Pb 0.3Sr 2Ca 2-x Zn x Cu 3O y at x=0.00, 0.05, 0.10, 0.15 and 0.20 levels on the electrical and structural properties was investigated in this work. The characterization of the ceramics prepared by the conventional solid-state reaction method were done by resistance-temperature measurements, XRD, SEM and density analysis. Low levels of Zn substitution of Ca caused significant changes in the properties of the ceramics. The low-T c superconducting properties were enhanced and the fraction of the low-T c (2212) phase were found to increase at x=0.15 level of Zn substitution at 830°C sintering temperature. Zero resistance was observed only in sample D with x=0.15 and the T c was determined as 92 K. The SEM micrographs and the density analysis have shown that this was the densest packed ceramic.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 15
    Supercritical Carbon Dioxide Drying of Methanol-Zinc Borate Mixtures
    (American Chemical Society, 2009) Gönen, Mehmet; Balköse, Devrim; Gupta, Ram B.; Ülkü, Semra
    Supercritical carbon dioxide (CO 2) drying of zinc borate species was investigated to evaluate possible chemical alterations in the product during the drying. Methanol-wetted zinc borates produced either from borax decahydrate and zinc nitrate hexahydrate (2ZnO · 3B 2O 3 ·7H 2O) or from zinc oxide and boric acid (2ZnO · 3B 2O 3 ·3H 2O) were dried by both conventional and supercritical carbon dioxide drying methods. Zinc borate samples dried by both techniques were characterized using analytical titration, X-ray powder diffraction (XRD), thermo gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, elemental analysis, and scanning electron microscopy (SEM). It was found that while zinc borate obtained from zinc oxide and boric acid did not have any chemical interaction with CO 2, carbonates were formed on the surface of zinc borate obtained from borax decahydrate and zinc nitrate hexahydrate. The main factor for the carbonate formation during supercritical CO 2 drying is anticipated as the structural differences of zinc borate species. CO 2 is a nonpolar solvent, and it does not usually react with polar substances unless water is present in the medium. While 2ZnO · 3B 2O 3 ·3H 2O had three bound OH groups, 2ZnO · 3B 2O 3 ·7H 2O had five bound OH groups and one mole of water of crystallization. It is proposed that the water of crystallization reacts with CO 2 forming carbonic acid. Then, carbonic acid, which is stronger than boric acid, substitutes borate ions from their zinc salts.
  • Article
    Citation - WoS: 249
    Citation - Scopus: 268
    Silver, Zinc, and Copper Exchange in a Na-Clinoptilolite and Resulting Effect on Antibacterial Activity
    (Elsevier Ltd., 2004) Top, Ayben; Ülkü, Semra
    Ag+-Na+, Zn2+-Na+, and Cu2+-Na+ equilibria for clinoptilolite-rich mineral from Gördes (Western Anatolia) were investigated at 25 °C and 0.1 N total solution normality. While silver exchange was favorable over the whole concentration range, zinc and copper were partially exchanged and preferred only at low concentrations. The standard free energies of exchanges for Ag+-Na+, Zn2+-Na+, and Cu2+-Na+ pairs were found as -6.0, 2.03, and 3.09 kJ/equiv., respectively. From these values, selectivity sequence was determined as Ag+>Na+ >Zn2+>Cu2+. Antibacterial activities of the exchanged samples were measured as a function of exchange level against Pseudomonas aeruginosa and Escherichia coli. Considering the selectivity sequence of the clinoptilolite and antibacterial activity results, Ag-clinoptilolite seemed to be promising antibacterial material.