Chemical Engineering / Kimya Mühendisliği

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

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Access type: Open accessInstitution Author: search.filters.institutionAuthor.Okur, Salih

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  • Article
    Citation - WoS: 60
    Citation - Scopus: 66
    Preparation and Characterization of Calcium Stearate Powders and Films Prepared by Precipitation and Langmuir-Blodgett Techniques
    (American Chemical Society, 2010) Gönen, Mehmet; Öztürk, Serdar; Balköse, Devrim; Okur, Salih; Ülkü, Semra
    The preparation of calcium stearate (CaSt2) using precipitation and Langmuir-Blodgett techniques was investigated in this study. While sodium stearate and calcium chloride were used in the precipitation process, calcium stearate nanofilms were produced from stearic acid and calcium chloride in sodium borate buffer with the Langmuir-Blodgett technique. Fourier transform infrared (FTIR) spectroscopy indicated carboxylate bands at 1577 and 1543 cm-1 in equal intensity in the powder form, but the films had a higher intensity 1577 cm-1 band than the 1543 cm-1 band. This showed the calcium ions associated with the COO- ions in the monodendate and bidendate structures in powders, and it was mainly in the bidendate structure in films. While characteristic peaks of CaSt2 at 2θ values of 6.40° and 19.58° were obtained in the X-ray diffraction (XRD) pattern of the dried powdered product, no sharp peaks were present in the 13 layer CaSt2 film. From scanning electron microscopy (SEM) micrographs, it was seen that calcium stearate powder had lamellar structure and the average particle size was 600 nm. The AFM picture of the CaSt2 film indicated the surface was not smooth with a peak to valley distance of 6 nm. © 2010 American Chemical Society.
  • Article
    Citation - WoS: 20
    Citation - Scopus: 23
    Effect of Humidity on Electrical Conductivity of Zinc Stearate Nanofilms
    (Elsevier Ltd., 2007) Öztürk, Serdar; Balköse, Devrim; Okur, Salih; Umemura, Junzo
    In this work, stearic acid (StAc) and zinc stearate (ZnSt2) nanofilms were deposited on glass and silver substrates using Langmuir-Blodgett (LB) film technique and their structural and electrical properties were investigated. X-ray diffraction and IR techniques revealed that more crystalline and better films were obtained from ZnSt2 compare to StAc. Electrical conductivity of ZnSt2 LB films with 13 layers having 28 nm thickness were measured in the range of humidity of 20-60% and it is seen that the conductivity was very sensitive to relative humidity (RH) above 40% at 25 °C and showed no hysteresis during adsorption and desorption of water vapor. Water vapor adsorption isotherm of ZnSt2 powders was determined and conductivity increase with humidity was attributed to water vapor adsorption. Constant electrical conductivity of the ZnSt2 films at low relative humidities and at low voltage values is an advantageous property which allows using them as organic nanofilms with insulating properties.