Sadriye Küçükbayrak

Istanbul Technical University, İstanbul, Istanbul, Turkey

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Publications (64)72.42 Total impact

  • Melek Erol, Ayşe Özyuğuran, Özlem Özarpat, Sadriye Küçükbayrak
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    ABSTRACT: In this study, it was aimed to fabricate and characterize three-dimensional composite scaffolds derived from Sr-doped bioactive glass for bone tissue engineering applications. The scaffolds were fabricated by using polymer foam replication technique and coated with gelatin to be able to improve the properties of them. The porous scaffolds were successfully synthesized using optimized process parameters. Both coated and uncoated scaffolds favored precipitation of calcium phosphate layer when they were soaked in simulated body fluid (SBF). Gelatin coating improved the mechanical properties of the scaffold and also it did not change the bioactive behavior of the scaffold. It was observed that there was a good pore interconnectivity maintained in the scaffold microstructure. Results indicated that scaffolds can deliver controlled doses of strontium toward the SBF medium. That is the determinant for bone tissue regeneration, as far as strontium is known to positively act on bone remodeling.
    Journal of the European Ceramic Society 08/2012; 32(11):2747–2755. · 2.36 Impact Factor
  • M. Erol, S. Küçükbayrak, A. Ersoy-Meriçboyu
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    ABSTRACT: The crystallization behavior and kinetics of glasses produced from coal fly ashes, red mud and silica fume were investigated by using differential thermal analysis, X-ray diffraction and scanning electron microscopy techniques. The kinetic parameters of the glass-crystallization transformation were estimated under non-isothermal conditions applying three different equations, namely, Kissinger, Matusuta-Sakka and Ozawa. Non-isothermal differential thermal analysis curves were obtained using both coarse and fine glass samples. The crystallization activation energies of coarse glasses are in the range of 233–439kJ/mol while the activation energies of fine glasses change in the range of 369–450kJ/mol. Avrami exponent, n, values of coarse glasses indicated the three-dimensional bulk crystallization. This result is in well agreement with the cross-sectional scanning electron microscopy investigations. The values of the n obtained experimentally are in the range of 1.24–1.36 for fine glasses which show the one-dimensional surface crystallization. The crystallized phase of the glass-ceramic samples produced from waste glasses by applying the controlled heat treatment process was identified as diopside by X-ray diffraction analysis.
    Journal of Non-Crystalline Solids 01/2011; 357(1):211-219. · 1.72 Impact Factor
  • N. Karatepe, A. Ersoy-MeriÇboyu, S. Küçükbayrak
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    ABSTRACT: Siliceous materials such as silica fume, bentonite and diatomite were mixed with Ca(OH)2 and hydrated at different conditions to produce reactive SO2 sorbents. Two different hydration methods were used; namely atmospheric and pressure hydration. The effects of the hydration temperature, time and siliceous material/Ca(OH)2 weight ratio on the physical properties of the activated sorbents were investigated. A statistical design technique was applied by use of a two-level factorial design matrix to interpret experimental results. In atmospheric hydration, it was found that increasing the temperature and hydration time caused an increase in the total surface area of the sorbents. But, increasing the siliceous material/Ca(OH)2 weight ratio caused a decrease in the total surface area of the sorbents. The relative surface area increments of sorbents are also influenced by the chemical composition of the siliceous material. In pressure hydration, mathematical analysis showed that the surface area of the activated sorbents was positively affected by the hydration variables. The activated sorbents were characterized by using thermogravimetry, x-ray diffractometer and scanning electron microscope. Thermogravimetric measurements showed that increasing the amount of reacted Ca(OH)2 during hydration, which was presumably converted to Ca-containing reactive speciesies caused an increase in the surface area of the sorbent. X-ray diffraction studies also indicated that calcium silicate hydrates were the principal Ca-containing species formed during hydration.
    Environmental Technology 05/2010; April 1(1999):377-385. · 1.61 Impact Factor
  • M. Erol, H. Haykiri-Acma, S. Küçükbayrak
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    ABSTRACT: Different 13 new formulae have been developed for estimating the calorific values of 20 different biomass samples from their proximate analyses data. In order to obtain these formulae, 20 biomass samples from different types were analyzed to determine calorific values and proximate analyses. The measured net heating values of the biomass samples varied between 15.41 and 19.52MJ/kg. All correlations were developed by means of least squares regression analyses. Regression coefficients of the correlations range from 0.829 to 0.898. Standard deviations of the heating values determined from 13 different correlations are between 0.4419 and 0.5280.
    Renewable Energy. 01/2010; 35(1):170-173.
  • M. Erol, S. Küçükbayrak, A. Ersoy-Meriçboyu
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    ABSTRACT: Sintered glass-ceramics were produced from coal fly ashes, red mud from aluminum production and silica fume. The capabilities of Tunçbilek fly ash and a mixture of Orhaneli fly ash, red mud and silica fume to be vitrified and devitrified by sintering process were investigated by means of scanning electron microscopy and X-ray diffraction analysis. To determine the effect of binder in the sintering technique, glass powders were pressed without or with the addition of polyvinyl alcohol. Owing to microstructural observations, density and hardness measurements, it can be said that physical properties and the hardness of the produced samples strongly depended on the crystallization degree of the samples. Toxicity characteristic leaching procedure test results showed that glass-ceramic samples produced by using sintering technique could be considered as non-hazardous materials. Chemical durability of the sintered glass-ceramic samples was also good. Microstructural investigations, hardness and physical properties of the samples indicated that the addition of polyvinyl alcohol improved the properties of sintered glass-ceramics obtained from Orhaneli fly ash, red mud and silica fume.
    Ceramics International. 01/2009;
  • M. Erol, S. Küçükbayrak, A. Ersoy-Meriçboyu
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    ABSTRACT: The crystallization kinetics of glasses obtained from coal fly ash was investigated by both isothermal and non-isothermal methods using differential thermal analysis (DTA) data. In DTA experiments, glass samples having coarse (800–1000μm) and fine (
    Journal of Non-Crystalline Solids 01/2009; 355(9):569-576. · 1.72 Impact Factor
  • M Erol, S Küçükbayrak, A Ersoy-Meriçboyu
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    ABSTRACT: Glass, glass-ceramic and ceramic materials were produced from thermal power plant fly ash without any additives. X-ray diffraction (XRD) analysis revealed the amorphous phase of the glass sample. Augite phase was detected in the glass-ceramic sample, while the enstatite and mullite phases occurred in the ceramic samples. Scanning electron microscopy (SEM) investigations showed that tiny crystallites homogeneously dispersed in the microstructure of the glass-ceramic sample and elongated crystals formed in the ceramic samples. Density values of the obtained samples are comparable to those of the commercially produced glass, glass-ceramic and ceramic samples. Toxicity characteristic leaching procedure (TCLP) results indicated that the produced samples could be taken as non-hazardous materials. Produced samples showed high resistance to alkali solutions in contrast to acidic solutions. Microstructural, physical, chemical and mechanical properties of the produced glass-ceramic samples are better than those of the produced glass and ceramic samples.
    Journal of Hazardous Materials 06/2008; 153(1-2):418-25. · 3.93 Impact Factor
  • M. Erol, S. Küçükbayrak, A. Ersoy-Meriçboyu
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    ABSTRACT: Çan, Çatalağzı, Seyitömer and Afşin-Elbistan thermal power plant fly ashes were used to investigate the sintering behavior of fly ashes. For this purpose, coal fly ash samples were sintered to form ceramic materials without the addition of any inorganic additives or organic binders. In sample preparation, 1.5 g of fly ash was mixed in a mortar with water. Fly ash samples were uniaxially pressed at 40 MPa to achieve a reasonable strength. The powder compacts were sintered in air. X-ray diffraction analysis revealed that quartz (SiO2), mullite (Al6Si2O13), anorthite (CaAl2Si2O8), gehlenite (Ca2Al2SiO7) and wollastonite (CaSiO3) phases occurred in the sintered samples. Scanning electron microscopy investigations were conducted on the sintered coal fly ash samples to investigate the microstructural evolution of the samples. Different crystalline structures were observed in the sintered samples. The sintered samples were obtained having high density, low water adsorption and porosity values. Higher Al2O3 + SiO2 contents caused to better properties in the sintered materials.
    Fuel. 01/2008;
  • M. Erol, S. Küçükbayrak, A. Ersoy-Meriçboyu
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    ABSTRACT: Glass-ceramic materials were produced from coal fly ashes obtained from Tunçbilek and Orhaneli thermal power plants in Turkey without or with the addition of red mud from aluminum production and silica fume. The nucleation and crystallization experiments were carried out on the basis of differential thermal analysis (DTA) results to produce glass-ceramic materials. X-ray diffraction (XRD) analysis of the produced glass-ceramic materials revealed that the main crystalline phases were diopside (Ca(Mg,Al)(Si,Al)2O6) and aluminum augite (Ca(Mg,Fe3+,Al)(Si,Al)2O6). The microstructure of the glass-ceramic materials was examined by scanning electron microscopy (SEM). Microstructural observation clearly indicated that the crystallization volume increased when the length of thermal treatment time increased. Glass-ceramic samples produced from industrial wastes had high density and microhardness values with a zero porosity and negligible water adsorption. Toxicity characteristic leaching procedure (TCLP) results showed that the produced glass-ceramic samples are non-toxic materials. Glass-ceramic sample showed high resistance to alkali solutions in contrast to acidic solutions. Overall results indicated that the glass-ceramic samples produced from waste materials with several desirable properties that would make them attractive to industrial use in construction, tiling and cladding applications.
    Chemical Engineering Journal. 01/2007;
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    M. Erol, S. Küçükbayrak, A. Ersoy-Meriçboyu
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    ABSTRACT: The recycling of three different fly ashes obtained from the coal fired thermal power plants has been studied. Coal fly ashes were vitrified by melting them at 1773K for 5h without any additives. After the glass production, glass samples were subjected to a heat treatment process to be able to see whether or not the glasses could be transformed into a microcrystalline structured materials. Produced glass samples were heated to 1423K and held at this temperature for 2h to determine the effect of heat treatment process on the properties of glasses. The properties of glass and the heat treated glass samples produced from coal fly ash were investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. DTA study indicated that there were only inflection points of the endothermic peaks in the DTA curves of the glass samples. XRD analysis showed the amorphous state of the glass samples and also the presence of only the diopside phase in the heat-treated glass samples. SEM investigations revealed that small amount of crystallites occurred in the microstructure of the heat treated glass samples in contrast to the amorphous structure of the glass samples. The mechanical, physical and chemical properties of the heat-treated glass samples are found better than those of the glass samples. Toxicity characteristic leaching procedure (TCLP) results showed that the heavy metals of fly ashes were successfully immobilized into both glass and heat treated glass samples. It can be said that glass and heat treated glass samples obtained by the recycling of coal fly ash can be taken as a non-hazardous material. Overall, results indicated that the vitrification technique is an effective way for the stabilization and recycling of coal fly ash.
    Fuel. 01/2007; 86(5):706-714.
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    ABSTRACT: The recycling of fly ash obtained from the combustion of coal in thermal power plant has been studied. Coal fly ash was vitrified by melting at 1773 K for 5 hours without any additives. The properties of glasses produced from coal fly ash were investigated by means of Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. DTA study indicated that there was only one endothermic peak at 1003 K corresponding to the glass transition temperature. XRD analysis showed the amorphous state of the glass sample produced from coal fly ash. SEM investigations revealed that the coal fly ash based glass sample had smooth surface. The mechanical, physical and chemical properties of the glass sample were also determined. Recycling of coal fly ash by using vitrification technique resulted to a glass material that had good mechanical, physical and chemical properties. Toxicity characteristic leaching procedure (TCLP) results showed that the heavy metals of Pb, Cr, Zn and Mn were successfully immobilized into the glass. It can be said that glass sample obtained by the recycling of coal fly ash can be taken as a non-hazardous material. Overall, results indicated that the vitrification technique is an effective way for the stabilization and recycling of coal fly ash.
    Journal of Environmental Science and Health Part A 02/2006; 41(9):1921-9. · 1.25 Impact Factor
  • M. Erol, S. Küçükbayrak, A. Ersoy-Meriçboyu, T. Ulubaş
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    ABSTRACT: In this study, the removal of Cu2+ and Pb2+ ions by precipitation from aqueous solutions by using six fly ashes with different compositions was achieved. The effect of four parameters on the removal of Cu2+ and Pb2+, which are contact time, fly ash composition, pH of the solution and fly ash concentration, were investigated. The fly ash concentrations required to achieve maximum Cu2+ and Pb2+ removal were found to vary between 0.2–10 and 0.075–3.5 g/l, respectively. It was also observed that both the Cu2+ and Pb2+ removal capacities of the fly ashes depend strongly on their CaO content.
    Energy Conversion and Management 05/2005; 46(s 7–8):1319–1331. · 3.59 Impact Factor
  • Key Engineering Materials - KEY ENG MAT. 01/2004;
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    ABSTRACT: Mixtures of Ca(OH)2 and diatomite were hydrated at different conditions to produce reactive SO2 sorbents. Two different hydration techniques were used; namely, atmospheric and pressure hydration. The effect of the hydration temperature, time and diatomite/Ca(OH)2 weight ratio on the physical properties of the activated sorbents were investigated. In atmospheric hydration, it was found that increasing the temperature and hydration time caused an increase in the total surface area of the sorbents. However, surface area values of the sorbents prepared from mixtures which have different diatomite/Ca(OH)2 weight ratio were generally not changed significantly. In pressure hydration, the surface area of the activated sorbents was positively affected from the hydration temperature and pressure. Finally, Ca(OH)2 and two diatomite/Ca(OH)2 sorbents were sulphated at constant temperature using a synthetic gaseous mixture consisting of 5% O2, 10% CO2, and the balance of nitrogen with a 55% relative humidity. The sulphation reaction of these sorbents were investigated and modelled. The unreacted shrinking core model was chosen to describe this non-catalytic solid/gas (hydrated sorbent/SO2) reaction mechanism. The experimental results were found to be correlated successfully by this model.
    Chemical Engineering Science. 01/2004;
  • Key Engineering Materials - KEY ENG MAT. 01/2004;
  • Key Engineering Materials - KEY ENG MAT. 01/2004;
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    ABSTRACT: Glass-ceramic materials were produced from fly ash samples obtained from the Seyitömer thermal power plant in Turkey. Glass samples were crystallized by suitable nucleation and crystal growth heat treatments on the basis of DTA results. The microstructural analysis of glass-ceramic samples were carried out using SEM and XRD techniques. SEM investigations clearly demonstrated the presence of a tiny crystallized phase dispersed in the microstructure. XRD results revealed that the main crystalline phase was diopside [Ca(Mg,Al)(Si,Al)2O6]. It was observed that the mechanical properties and the thermal expansion coefficient of the glass-ceramic samples depend only on the amount of the crystalline phase. Furthermore, chemical durability of the produced glass-ceramic samples were high.
    Journal of the European Ceramic Society 01/2003; · 2.36 Impact Factor
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    ABSTRACT: In this study, the combustion reactivity of different rank coals, such as peat, lignite, bituminous coal and anthracite samples, was investigated. Non-isothermal thermogravimetry has been used to determine the combustion reactivities of the samples. The differences observed in the burning profile of the samples were studied. The calculated activation energy values of the samples were investigated, regarding carbon content, volatile matter content and burning profile peak temperature. The relationship between ignition temperature and carbon content (dmf) of the coal samples was also studied. The weight loss percentages of the different rank coal samples were discussed, depending on temperature.
    Energy Conversion and Management - ENERG CONV MANAGE. 01/2002; 43(4):459-465.
  • R Yavuz, S Küçükbayrak
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    ABSTRACT: To obtain commercially suitable coal–water slurry (CWS), usage of the appropriate type and amount of chemical additives is necessary from various points of view. Since the properties of coal change from one type to another, it is not possible to find an universal dispersing agent, which is acceptable for all types of coals. Examination of the adsorption behavior of the dispersant and the amount of dispersant which is really necessary to make coal particles disperse in water is very important because of the adverse effect of an excess amount of dispersant on the flow and sedimentation properties of CWS, and the high cost of dispersants. The main objective of our research is to represent how some factors, such as air-oxidation, demineralization, stirring speed, particle size distribution, concentration of slurry and addition stage of dispersant, affect the dispersant adsorption characteristic of formaldehyde condensate sodium salt of naphthalene sulfonic acid. These factors were investigated by using Turkish lignite samples and, consequently, the influence of these factors on the dispersant adsorption behavior was determined and discussed.
    Powder Technology 01/2001; 119(2):89-94. · 2.50 Impact Factor
  • Serdar Yaman, Reha Yavuz, Sadriye Küçükbayrak, Yılmaz Taptık
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    ABSTRACT: The mineral matter of coal contains a number of inorganic constituents, which play an important role in almost all coal utilisation systems. Some techniques have been applied to coal to separate its mineral matter from its organic part. In this study, an alternative method was applied to separate the mineral matter content of a Turkish lignite. For this purpose, Göynük lignite was treated, in sequence, with acetic acid, ammonia, hydrochloric acid, hydrofluoric acid and nitric acid at 70°C for 60 min in order to remove individual mineral species. After each stage, the lignite was treated with performic acid, the product of reaction between hydrogen peroxide and formic acid, at 50°C. The organic coal matrix was decomposed as a result of performic acid oxidation, and consequently, the recovered mineral species were isolated. Ammonia, which has the potential of chemical comminution, was used to increase the effects of the subsequent reagents and enhance the extent of separation between the organic and inorganic phases. In each mineral matter removal stage, the lignite was treated with the reagents of the previous stage, and then, a new reagent was added to investigate whether the last stage has a different effect on the mineral species. FT-IR and X-ray diffractometry techniques were used to determine the constituents of the isolated mineral matter after each stage.
    Energy Conversion and Management - ENERG CONV MANAGE. 01/2001; 42(18):2119-2127.

Publication Stats

359 Citations
72.42 Total Impact Points

Institutions

  • 1988–2012
    • Istanbul Technical University
      • • Department of Chemical Engineering
      • • Faculty of Chemical and Metallurgical Engineering
      İstanbul, Istanbul, Turkey