Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Author: search.filters.author.Balköse, DevrimScopus Q: search.filters.scopusQuartile.Q4

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  • Article
    Lubricants Having Zinc Borate by Homogeneous Precipitation and Span 60 in Spindle Oil
    (Turkish Energy Nuclear and Mining Research Institute, 2021) Gönen, Mehmet; Alp, Burcu; Savrık, Sevdiye; Balköse, Devrim; Alp, Fatma Burcu; Balkose, Devrim
    Nano particles of zinc borate were obtained by homogeneous precipitation method which is based on dissolving zinc borate in ammonia and precipitating it as nano particles by slow evaporation of ammonia. The synthesized zinc borates were characterized by advanced analytical techniques. Zinc borate nano particles were used as a lubricant additive to spindle oil having Span 60 dispersant. The particles were well dispersed in spindle oil as shown by optical microscopy of the oils. Four ball tests of the lubricants indicated zinc borate lowered (61.8%) the wear scar diameter significantly. The hardness of wear surfaces of test balls was reduced from 688 HV to 618 HV and presence of zinc borate particles embedded on the surface indicated a flexible skin was formed. Therefore the pressure was decreased due to increase of the contact area of the balls. The surface roughness was also decreased from 35.63 nm to 27.60 nm by the addition of zinc borate to spindle oil having Span 60. Zinc borate prepared by homogeneous precipitation technique lowered the wear of the surfaces that rub to each other.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 7
    Effect of the Zeolite Filler on the Thermal Degradation Kinetics of Polypropylene
    (Scibulcom Ltd., 2006) Tıhmınlıoğlu, Funda; Pehlivan, Hilal; Balköse, Devrim; Ülkü, Semra
    In this study, the thermal degradation behaviour of polypropylene (PP) and polypropylene-zeolite composites was investigated. Clinoptilolite, a natural zeolitic tuff, was used as the filling material into the composites. Effect of both pure clinoptilolite and silver ion exchanged form of clinoptilolite addition on the thermal degradation kinetics of polypropylene composites was studied by using differential scanning calorimetry (DSC) and thermal gravimetry analysis (TGA) techniques. Polymer degradation was evaluated by using DSC with heating rates of 5, 10, and 20 degrees C/ min from room temperature up to 500 degrees C. Silver concentration (4.36, 27.85 and 183.8 mg Ag/g zeolite) was the selected parameter under consideration. From the DSC curves, it was observed that the heat of degradation values of the composites containing 2-6% silver exchanged zeolites (321-390 kJ/kg) were larger compared to that of the pure PP free of silver and zeolite (258 kJ/kg). From the DSC results it was confirmed that PP-zeolite composites can be used at higher temperatures compared to the pure PP polymer because of its higher thermal stability. The thermal decomposition activation energies of the composites were calculated by using both the Kissenger and Ozawa models. The values predicted from these two equations were in close agreement. From the TGA curves, it was found that zeolite addition into the PP matrix speeds down the decomposition reaction, however, silver exchanged zeolite addition into the matrix accelerates the reaction. The higher the silver concentration, the lower the thermal decomposition activation energies were obtained. As a result, PP was found to be much more susceptible to thermal decomposition in the presence of silver exchanged zeolite.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 5
    Dynamic Heat of Adsorption of Water Vapour on Zeolitic Tuff and Zeolite 4a by Flow Microcalorimetry
    (Scibulcom Ltd., 2006) Ülkü, Semra; Balköse, Devrim; Alp, Burcu
    In this study a practical method for measurement of heat of adsorption of water vapour on adsorbents was developed to evaluate the feasibility of substitution of a zeolitic tuff with zeolite 4A in air drying and heat pumps. The change of heat of adsorption with inlet humidity of the air passing through the calorimeter was investigated. Samples were characterised by X-ray diffraction and thermal gravimetric analysis techniques. Specific heats of the zeolitic tuff and zeolite 4A were measured as 1.01 and 1.42 J/g K, respectively. Adsorption isotherms fitted to the Langmuir model with regression coefficient 0.93 and 0.94 with monolayer capacities, Xm 9.68% and 26.35% H 2O for the zeolitic tuff and zeolite 4A, respectively. The energy storage intensity was measured in the range 48-97 J/g and 464-201 J/g for the tuff and zeolite 4A, respectively. Heat of adsorption of zeolite decreased with surface coverage and it was in the range 1750-2835 and 1104-2640 J/g H 2O for the zeolitic tuff and zeolite 4A, respectively.