Sadriye Küçükbayrak

Istanbul Technical University, İstanbul, Istanbul, Turkey

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Publications (70)149.54 Total impact

  • S.Ö. Gönen · Melek Erol Taygun · Sadriye Küçükbayrak
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    ABSTRACT: This article presented a study on the effects of solution properties (i.e., gelatin concentration, alginate concentration, content of alginate solution in the blend solution, and content of acetic acid in the solvent of gelatin solution) on the average diameter of electrospun gelatin/sodium alginate nanofibers, as well as its standard deviation. For this purpose, blend solutions of two natural polymers (gelatin and sodium alginate) were prepared both in the absence and presence of ethanol. Response surface methodology based on a three-level, four-variable Box-Benkhen design was employed to define quadratic relationships between the responses and the solution properties. The individual and interactive effects of the solution properties were determined. Moreover, the adequacy of the models was verified by the validation experiments. Results showed that the average diameters of the resultant nanofibers were 68-166 nm and 90-155 nm in the absence and presence of ethanol, respectively. The experimental results were in good agreement with the predicted response values. Hence, this study provides an overview on the fabrication of gelatin/sodium alginate nanofibers with targeted diameter, which may have potential to be used in the field of tissue engineering.
    No preview · Article · Jan 2016 · Materials Science and Engineering C
  • Seza Özge Gönen · Melek Erol Taygun · Sadriye Küçükbayrak
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    ABSTRACT: This study mainly focuses on fabricating nanocomposite fibrous mats for bone tissue engineering. For this purpose, strontium or copper doped bioactive glass particles were successfully incorporated into gelatin/poly(ε-caprolactone) (Gt/PCL) nanofibers through electrospinning process. As the content of bioactive glass increased, the average diameter of the as-spun nanocomposite fiber mats rised. It was further observed that the in vitro bioactivity of the fiber mats enhanced with the inclusion of BG particles into the polymeric matrix. In addition, the release of therapeutic ions were determined as a function of immersion time in SBF, which was in the range of 5.4–10.1 mg/g scaffold and 0.34–1.87 mg/g scaffold for strontium and copper ions, respectively. Although the results were promising, the amount of SrO and CuO in the composition of bioactive glasses can be increased to improve the osteogenic, angiogenic, and antibacterial potential of the nanocomposite fiber mats. Hence, this study provides an insight for future researchers who aim to create nanocomposite materials as multifunctional scaffolds for bone tissue engineering applications.
    No preview · Article · Nov 2015
  • Seza Özge Gönen · Melek Erol Taygun · Sadriye Küçükbayrak
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    ABSTRACT: An electrospinning procedure was carried out to fabricate gelatin/poly(ϵ-caprolactone) (Gt/PCL) nanofibers. Response surface methodology based on a three-level, four-variable Box-Behnken design technique was used to model the resultant diameter of the as-spun nanofibers. A second-order model was obtained to describe the relationship between the fiber diameter and the electrospinning parameters, namely Gt concentration, PCL concentration, content of acetic acid in the overall solvent, and content of Gt solution in the blend solution. The individual and the interactive effects of these parameters on the fiber diameter were determined. Validation experiments verified the accuracy of the model which provided a simple and effective method for fabricating nanofibers with a controllable and predictable fiber diameter.
    No preview · Article · Mar 2015 · Chemical Engineering & Technology
  • M. Erol · H. Haykiri-Acma · A. Özyuǧuran · B. Kükürtçü · S. Küçükbayrak
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    ABSTRACT: In this study, bioactivity of glass and glass-ceramic in the system SiO2-CaO-Al2O3-P2O5-Na2O-MgO-CaF2 was investigated. The bioactivity of the resultant samples was analyzed by immersion study in simulated body fluid (SBF). Scanning electron microscopy (SEM-EDS), thin film X-ray diffraction (TF-XRD), ultraviolet spectroscopy (UV) and inductively coupled plasma (ICP) techniques were used to monitor changes in the glass and glass-ceramic surfaces and SBF composition. The results revealed that a hydroxyapatite (HA) layer was formed on the glass and glass-ceramic surfaces after 7 days and 1 day immersion, respectively. In addition, Al2O3 content of the bioactive glass and glass-ceramic improved the properties of the samples and did not cause a negative effect on the bioactivity of the samples.
    No preview · Article · Nov 2013 · Advanced Science Letters
  • M. Erol · A. Özyuǧuran · M. Maraşli · S. Küçükbayrak
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    ABSTRACT: In this study, it was aimed to produce bioactive glasses (SiO2-CaO-P2O5-Na2O-CuO and SiO2-CaO-P2O5-Na2O-CuO-SrO) with the substitution of strontium and copper in different weight percentages. Thermal, and in vitro biological properties of the glasses were studied and compared to each other. In vitro simulated body fluid studies were performed to investigate the bioactivity of the produced glass samples. Scanning electron microscopy, X-ray diffraction, ultraviolet spectroscopy and inductively coupled plasma techniques were used to monitor changes in the glass surface and SBF composition. The results showed that all glasses favored precipitation of calcium phosphate layer when they were soaked in SBF; they can also deliver controlled doses of strontium and copper toward the SBF medium that is the determinant for bone tissue regeneration.
    No preview · Article · Nov 2013 · Advanced Science Letters
  • Y. Döşemen · M. Erol · H. Haykırı-Açma · S. Küçükbayrak
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    ABSTRACT: A factorial design analysis was applied to optimize the production of activated carbon from chestnut shell by chemical activation using ZnCl2. The effects of various experimental parameters such as activation temperature, heating rate and holding time on the solid yield and Brauner–Emmet–Teller surface area values of activated carbon were investigated. Analysis of variance method was used to determine the significant factors on each experimental design response. The best activated carbon which was produced at the activation temperature of 873 K, with a heating rate of 15 K min−1 and 45 minutes holding time had the highest surface area (1823 m2 g−1) and acceptable solid yield (33.31%). The overall results showed that the factorial design analysis is an appropriate method to be able to determine the optimum parameters for the activated carbon production.
    No preview · Article · Nov 2013 · Journal of Computational and Theoretical Nanoscience
  • 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.
    No preview · Article · Aug 2012 · Journal of the European Ceramic Society
  • 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.
    No preview · Article · Nov 2011 · Journal of Non-Crystalline Solids
  • M. Erol · A. Özyuğuran · Ö. Özarpat · S. Küçükbayrak
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    ABSTRACT: In this study, it was aimed to produce bioactive glasses (SiO2-CaO-P2O5-Na2O-SrO) with the substitution of strontium in different weight percentages. Physical, thermal, and in vitro biological properties of the glasses were studied and compared to each other. In vitro simulated body fluid studies were performed to investigate the bioactivity of the produced glass samples. Scanning electron microscopy, X-ray diffraction, ultraviolet spectroscopy and inductively coupled plasma techniques were used to monitor changes in the glass surface and SBF composition. The results showed that all glasses favored precipitation of calcium phosphate layer when they were soaked in SBF; however bioactivity of the glasses increased with the increase of strontium content in the glasses.
    No preview · Article · Oct 2011 · Key Engineering Materials
  • Melek Mümine Erol · Sadriye Küçükbayrak · Ayşegül Ersoy-Meriçboyu

    No preview · Article · Feb 2011
  • 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.
    No preview · Article · May 2010 · Environmental Technology
  • 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.
    No preview · Article · Jan 2010 · Renewable Energy
  • 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.
    No preview · Article · Sep 2009 · Ceramics International
  • 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 (800-1000 μm) and fine (<180 μm) particle sizes were used and the results were compared. The Avrami exponent (n) was calculated by means of Johnson-Mehl-Avrami (JMA) and Ozawa equations. Calculated kinetic parameters indicated that the appropriate crystallization mechanisms were bulk and surface crystallization for coarse and fine particles, respectively. Isothermal and non-isothermal DTA experiments showed that the crystallization activation energies of coarse glasses are changed in the range of 444-578 kJ/mol, while the crystallization activation energies of fine glasses are changed in the range of 610-662 kJ/mol. It was found that crystallization activation energies of fine glasses are higher than those of the coarse glasses. Results showed that isothermal and non-isothermal crystallization kinetics of glasses produced from coal fly ash is in agreement within the experimental error.
    No preview · Article · Apr 2009 · Journal of Non-Crystalline Solids
  • M. Erol · S. Küçükbayrak
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    ABSTRACT: A thermal power plant fly ash was used to produce aceramic material by sintering technique. Coal fly ashsamples were sintered at the temperature range of 1273-1348 K for 2 hours to investigate the effect of firingtemperature on microstructure and physical propertiesof the produced materials. X-ray diffraction (XRD)analysis revealed that quartz (SiO2), mullite (Al6Si2O13),anorthite (CaAl2Si2O8) and enstatite ((Mg,Fe)SiO3)phases detected in the fly ash sample disappeared;wollastonite (CaSiO3) and gehlenite (Ca2Al2SiO7)phases occurred in the ceramic samples. Scanningelectron microscopy (SEM) investigations wereconducted on the produced ceramic materials toinvestigate the microstructural evolution of the samples.The dentritic dense crystalline structure was observed inthe produced samples. Density and hardness values ofthe produced samples increased significantly withincreasing sintering temperature while water adsorptionand porosity values decreased. The overall resultsshowed that it is possible to produce ceramic materialsfrom the coal fly ash with high density, low porosityand water adsorption values.
    No preview · Article · Jan 2009
  • A. Özyuǧuran · M. Erol · S. Küçükbayrak
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    ABSTRACT: Bioglass-ceramic in the system SiO2-CaO-P2O5-Na2O was produced by the sintering technique. A glass sample was produced by the classical melting method. Differential thermal analyses (DTA) measurements were applied to the glass sample to determine the nucleation and crystallization temperatures. Glass powders were cold pressed and then crystallized by suitable nucleation and crystal growth heat treatments on the basis of DTA results. To investigate the morphology of the resultant microstructure, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were conducted to the produced bioglassceramic sample. XRD patterns of the sample showed clearly that the crystalline phases were hydroxyapatite (HA) and sodium calcium silicate. The HA crystallites in the microstructure of the bioglass-ceramic were observed at the SEM micrographs of the sample. The mechanical, physical and chemical properties of the bioglass-ceramic samples were also determined. It was found that the physical, chemical and mechanical properties of the bioglass-ceramic samples depend on the amount of crystalline phase.
    No preview · Article · Jan 2009
  • 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.
    No preview · Article · Jun 2008 · Fuel
  • 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.
    No preview · Article · Jun 2008 · Journal of Hazardous Materials
  • 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.
    No preview · Article · Aug 2007 · The Chemical Engineering Journal
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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.
    Full-text · Article · Mar 2007 · Fuel