Yazar "Kaya, Gulcihan Guzel" seçeneğine göre listele

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    Preparation and characterization of pH-sensitive semi-interpenetrating network hybrid hydrogels with sodium humate and kaolin
    (ELSEVIER SCIENCE BV, 2018) Yilmaz, Elif; Kaya, Gulcihan Guzel; Deveci, Huseyin
    Poly(acrylamide-co-methacrylic acid) semi-interpenetrating network (semi-IPN) hybrid hydrogels including sodium humate and kaolin were successfully synthesized as confirmed with X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FTIR) analyses. Scanning electron microscopy (SEM) analysis indicated uniform dispersed morphology of the hydrogels. It was specified with thermogravimetric-derivative thermogravimetric analysis (TGA-DTG) that the addition of kaolin provided to increase thermal decomposition temperatures of the hydrogels. The semi-IPN hybrid hydrogel exhibited highest equilibrium swelling percent (ESP) of 28,700% and 3440% in distilled water and 0.1 M NaCl, respectively. The hydrogels had better swelling behavior in basic medium compared to acidic medium. While the ESP value of semi-IPN hybrid hydrogel was about 1590% at pH 2, it was determined as 7046% at pH 9. Each hydrogel showed non-Fickian type diffusion and excellent biocompatibility (> 0.94). The results suggested that the obtained pH-sensitive semi-IPN hydrogels with unique properties can be used as biomaterial, adsorbent, membrane, sensor component and so on.
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    Sustainable bean pod/calcined kaolin reinforced epoxy hybrid composites with enhanced mechanical, water sorption and corrosion resistance properties
    (ELSEVIER SCI LTD, 2018) Kaya, Gulcihan Guzel; Yilmaz, Elif; Deveci, Huseyin
    The industrial and academic world is becoming more interested in advanced composite materials owing to the increasing global awareness on environmental and social issues. From this point of view, novel epoxy hybrid composites were prepared by utilizing bean pod as an agricultural waste and calcined kaolin with the addition of varying ratios (0.5-5.0 wt%) to fixed weight of 3 wt% bean pod. The resulting hybrid composites were characterized by different analyses and tests to evaluate physico-mechanical and thermal properties. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses showed uniform dispersion of hybrid filler in the neat epoxy resin which revealed better compatibility between hybrid filler and epoxy resin. Tensile strength of hybrid composite including 2 wt% calcined kaolin (39.8 MPa) was higher than those of the other hybrid composites. The water sorption percentage of the hybrid composites was effectively decreased until 0.87% with increasing amount of calcined kaolin. The hybrid composite including 5 wt% calcined kaolin exhibited highly corrosion resistance to alkali and salty solutions compared to acidic reagents. Thermogravimetric analyses (TGA) and vicat softening temperature (VST) tests revealed that an important improvement was not observed in degradation temperatures of the hybrid composites; however, residue at 650 degrees C increased up to 21.0% in the presence of calcined kaolin. It can be said that the hybrid composites mentioned above came into prominence with high tensile strength, quite low water uptake and excellent corrosion resistance in alkali and salty environments. (C) 2017 Elsevier Ltd. All rights reserved.
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    Sustainable nanocomposites of epoxy and silica xerogel synthesized from corn stalk ash: Enhanced thermal and acoustic insulation performance
    (ELSEVIER SCI LTD, 2018) Kaya, Gulcihan Guzel; Yilmaz, Elif; Deveci, Huseyin
    The synthesis of silica xerogel from corn stalk ash in ambient pressure drying was carried out by sol-gel method. With the usage of silica xerogel (0.5, 1.0 and 1.5 wt%) in epoxy resin (ER), silica xerogel/epoxy nanocomposites were successfully prepared. The uniform dispersion of silica xerogel in neat ER was observed except nano composite including 1.5 wt% silica xerogel. The low density nanocomposites showed high thermal stability and low thermal conductivity. The char residue at 600 degrees C and thermal conductivity of nanocomposite including 1.5 wt% silica xerogel were specified as 20.30% and 0.220 W/mK, respectively. The acoustic velocity of the nanocomposites was decreased with increasing amount of silica xerogel. The water sorption of the nano composites was slightly higher than neat ER. The water contact angle of the nanocomposites were between 75 degrees and 70 degrees. The study provided a new thermal and acoustic insulation material instead of expensive and health risk traditional materials.