Browsing by Subject "Pyrolysis"
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Item Open Access Analysis of polymers using evolved-gas and direct-pyrolysis techniques(Royal Society of Chemistry, 1994) Fares, M. M.; Yalcin, T.; Hacaloglu, J.; Gungor, A.; Süzer, ŞefikThermal analysis of polystyrene, poly(p-methylstyrene) and poly(α-methylstyrene) has been carried out using evolved-gas analysis by infrared and mass spectrometry, and direct-pyrolysis analysis by mass spectrometric techniques. Evolved-gas analysis, both by infrared and mass spectrometry, reveals features due mainly to the corresponding monomers or stable, volatile, and low relative molecular mass degradation products. In direct-pyrolysis mass spectrometry, however, primary decomposition products and heavier fragments such as dimers and trimers can also be detected. The ion-temperature profiles of the corresponding monomer ions reveal information about the thermal stability of the polymers.Item Open Access Characterization of degradation products of polyethylene oxide by pyrolysis mass spectrometry(Pergamon Press, 1994) Fares, M. M.; Hacaloglu, J.; Süzer, ŞefikThe techniques of direct and indirect (evolved gas analysis) pyrolysis MS are used to characterize the thermal degradation products of polyethylene oxide. Using direct pyrolysis MS technique the main degradation process is determined to be due to CO and CC scissions yielding fragments characteristic of the polymer. Evolved gas analysis indicates formation of small molecular stable compounds such as C2H5OC2H5, CH3CHO, CO2, CO and C2H4. © 1994.Item Open Access Cyclodextrin functionalized poly(methyl methacrylate) (PMMA) electrospun nanofibers for organic vapors waste treatment(Elsevier BV, 2010) Uyar, Tamer; Havelund, R.; Nur, Y.; Balan, A.; Hacaloglu, J.; Toppare, L.; Besenbacher, F.; Kingshott, P.Poly(methyl methacrylate) (PMMA) nanofibers containing the inclusion complex forming betacyclodextrin (_-CD) were successfully produced by means of electrospinning in order to develop functional nanofibrous webs for organic vapor waste treatment. Electrospinning of uniform PMMA nanofibers containing different loadings of _-CD (10%, 25% and 50% (w/w)) was achieved. The surface sensitive spectroscopic techniques; X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed that some of the _-CD molecules are present on the surface of the PMMA nanofibers, which is essential for the trapping of organic vapors by inclusion complexation. Direct pyrolysis mass spectrometry (DP-MS) studies showed that PMMA nanowebs containing _-CD can entrap organic vapors such as aniline, styrene and toluene from the surroundings due to inclusion complexation with _-CD that is present on the fiber surface. Our study showed that electrospun nanowebs functionalized with cyclodextrinsmayhave the potential to be used as molecular filters and/or nanofilters for the treatment of organic vapor waste and air filtration purposes.Item Open Access FT-IR spectroscopic investigation of the surface reaction of CH4 with NOx species adsorbed on Pd/WO3–ZrO2 catalyst(2007) Kantcheva, M.; Cayirtepe, I.The interaction of methane at various temperatures with NO x species formed by room temperature adsorption of NO + O2 mixture on tungstated zirconia (18.6 wt.% WO3) and palladium(II)-promoted tungstated zirconia (0.1 wt.% Pd) has been investigated using in situ FT-IR spectroscopy. A mechanism for the reduction of NO over the Pd-promoted tungstated zirconia is proposed, which involves a step consisting of thermal decomposition of the nitromethane to adsorbed NO and formates through the intermediacy of cis-methyl nitrite. The HCOO- formed acts as a reductant of the adsorbed NO producing nitrogen. © Springer Science+Business Media, LLC 2007.Item Open Access Thermal degradation of polythiophene-natural rubber and polythiophene-synthetic rubber conducting polymer composites(1997) Hacaloǧlu J.; Yiǧit, S.; Akbulut, U.; Toppare L.Thermal degradation of conducting polymer composites of polythiophene and rubbers was studied by direct and indirect pyrolysis mass spectrometry techniques. The samples were prepared by electrooxidation of polythiophene using natural rubber or synthetic rubber as the insulating matrix. Presence of decomposition products which were not observed during pyrolysis of pure polythiophene and rubbers, and disappearance of rubber-based pyrolysis mass peaks, together with changes in thermal stability and behaviour, may directly be related to a chemical interaction between the components of the composites. The pyrolysis data were used to propose possible polymerization and degradation mechanisms. © 1997 Elsevier Science Ltd.Item Open Access Use of saccharides as solid-state precursors for the synthesis of carbon nanotubes(Materials Research Society, 2008) Küçükkayan, Gökçe; Kayacan, Serim; Baykal, Beril; Bengu, ErmanSaccharides, ranging from simple table sugar (sucrose) to lactulose were successfully used as solid-state precursors for the synthesis of multi-walled carbon nanotubes (MWCNT). Dehydrated saccharide residues mixed with catalyst powders were subjected to pyrolysis at high temperatures (up to 1300°C) under flowing Argon atmosphere. Pyrolysis products were investigated using TEM, SEM, Raman spectroscopy and EDS. Images taken using the S/TEM and bright field mode of TEM showed the presence of helical multi-walled carbon nanotube (H-MWCNT) and regular MWCNT formation. More than two or three catalyst particles were observed to be present inside the hollow core of some of the nanotubes synthesized, suggesting a high level of capillary activity inside the tubes during synthesis. © 2008 Materials Research Society.