Browsing by Subject "Decomposition temperature"

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    Molecular entrapment of volatile organic compounds (VOCs) by electrospun cyclodextrin nanofibers
    (Elsevier, 2016-02) Celebioglu A.; Sen, H. S.; Durgun, Engin; Uyar, Tamer
    In this paper, we reported the molecular entrapment performance of hydroxypropyl-beta-cyclodextrin (HPβCD) and hydroxypropyl-gamma-cyclodextrin (HPγCD) electrospun nanofibers (NF) for two common volatile organic compounds (VOCs); aniline and benzene. The encapsulation efficiency of CD samples were investigated depending on the various factors such as; CD form (NF and powder), electrospinning solvent (DMF and water), CD (HPβCD and HPγCD) and VOCs (aniline and benzene) types. BET analysis indicated that, electrospun CD NF have higher surface area compared to their powder form. In addition DMA measurement provided information about the mechanical properties of CD NF. The encapsulation capability of CD NF and CD powder was investigated by 1H-NMR and HPLC techniques. The observed results suggested that, CD NF can entrap higher amount of VOCs from surroundings compared to their powder forms. Besides, molecular entrapment efficiency of CD NF also depends on CD, solvent and VOCs types. The inclusion complexation between CD and VOCs was determined by using TGA technique, from the higher decomposition temperature of VOCs. Finally, our results were fortified by the modeling studies which indicated the complexation efficiency variations between CD and VOC types. Here, the inclusion complexation ability of CD molecules was combined with very high surface area and versatile features of CD NF. So these findings revealed that, electrospun CD NF can serve as useful filtering material for air filtration purposes due to their molecular entrapment capability of VOCs.
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    ItemOpen Access
    Nature of the Ti-Ba interactions on the BaO/TiO2/Al 2O3 NOx storage system
    (2009) Andonova, S. M.; Şentürk, G. S.; Kayhan, E.; Ozensoy, E.
    A ternary oxide-based NO* storage material in the form of BaOZTiO2Zy-Al2O3 was synthesized and characterized. Thermally induced structural changes occurring on the surfaces of the TiO2Zy-Al2O3 and BaOZ TiO 2Zy-Al2O3 systems were studied in a comparative manner within 300-1273 K via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and BET surface area analysis. The surface acidity of the studied oxide systems was also investigated via pyridine adsorption monitored by in-situ Fourier transform infrared (FTIR) spectroscopy. BaO/TiO2γ-Al 2O3 ternary oxide was synthesized by incorporating different loadings of (8-20 wt %) BaO onto the TiO2/γ Al 2O3 support material, which was originally prepared using the sol-gel method. In the TiO2Zy-Al2O3 binary oxide support material, anatase phase exhibited a relatively high thermal stability at T < 1073 K. The presence of TiO2 domains on the surface of the alumina particles was found to alter the surface acidity of alumina by providing new medium-strength Lewis acid sites. SEMZEDX results indicate that in the BaO/TiO2γ-Al2O3 system, TiO2 domains present a significant affinity toward BaO and/or Ba(NO3) 2 resulting in a strong Ti-Ba interaction and the formation of overlapping domains on the surface. The presence of TiO2 also leads to a decrease in the decomposition temperature of the Ba(N03) 2 phase with respect to the Ti-free Ba(N03) 2ZyAl2O3 system. Such a destabilization is likely to occur due to a weaker interaction between Ba(N03) 2 and y-Al203 domains in the ternary oxide as well as due to the change in the surface acidity in the presence of TiO 2. At relatively high temperatures (e.g., 873-1273 K) formation of complex structures in the form of BaTiO3, Ba1.23Al 2.46Ti5.54O16, BaTiO5, andor Ba x:AlyTizOn., were also observed. © 2009 American Chemical Society.
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    ItemOpen Access
    Polymer/clay nanocomposites through multiple hydrogen-bonding interactions
    (John Wiley and Sons Inc., 2015) Aydin, M.; Uyar, Tamer; Tasdelen, M. A.; Yagci Y.
    An 2-ureido-4[1H]pyrimidinone (UPy) motif with self-association capability (through quadruple hydrogen bonds) was successfully anchored onto montmorillonite clay layers. Polymer/clay nanocomposites were prepared by specific hydrogen bonding interactions between surface functionalized silica nanoclays and UPy-bonded supramolecular poly(ethylene glycol) or poly(É-caprolactone). The mixed morphologies including intercalated layers with a non-uniform separation and exfoliated single layers isolated from any stack were determined by combined X-ray diffraction and transmission electron microscopic measurements. Thermal analyses showed that all nanocomposites had higher decomposition temperatures and thermal stabilities compared with neat polymer. The differential scanning calorimetric data implied that the crystallinity of polymers did not show essential changes upon introduction of organomodified UPy clays.