Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - Scopus: 1Oxidizer Gases Effects on the Diameter-Controlled Synthesis of Carbon Nanotubes(MIM Research Group, 2021) İnce Yardımcı, Atike; Öğütlü, Ahmet Sabri; Öğütlü, DenizIn this study, the influence of the oxidizers on the synthesis of carbon nanotubes by C2H4 decomposition over Fe catalyst has been investigated. CO2, O2, and H2O have been used as oxidizers, and to control catalyst particle formation and their sizes in the pretreatment stage. The same oxidizers have also been used in the growth stage to maintain the catalyst particle size, remove amorphous carbon formation to keep catalyst particle active. The results of scanning electron microscopy indicated that the average diameters of nanotubes decreased from 13.4±1.2 nm to 6.2±0.5 nm and extremely dense nanotubes were obtained when we added a small amount of CO2. Adding O2 extremely decreased the areal carbon nanotube density while widens the diameter distribution. H2O addition resulted in larger average diameters and made the growth strongly pretreatment dependent. Within the parameters tried for catalyst pretreatment and CNT growth processes, CO2 seemed the best choice for a weak oxidizing assistant. The strong dependency of the average diameter on pretreatment conditions indicated that pretreatment is a very important step in deciding the final diameters and their distribution.Article Citation - WoS: 2Dimensions of Polystyrene Particles Deposited on Mica From Dilute Cyclohexane Solution at Different Temperatures(American Chemical Society, 2002) Demir, Mustafa Muammer; Erman, BurakUsing atomic force microscopy, the height, diameter, and volume of polystyrene particles deposited on mica from dilute cyclohexane solution at different temperatures are determined. Dimensions exhibit a strong temperature dependence. The heights of the deposited particles are only a few atomic diameters, the major dimension being parallel to the mica surface. The number of single polystyrene molecules in a deposited particle cannot be determined directly by atomic force microscopy. However, the maximum number of molecules that may be present in a particle may be estimated. Below 35 °C, the particles possibly consist of single collapsed molecules. This number increases with temperature and becomes as large as about 30 molecules per particle at 80 °C. The volume occupied by a single chain in solvent is calculated as a function of temperature and compared with observed volumes of dry particles on mica. A linear relationship is observed between single chain volumes in solvent and corresponding particle volumes on mica. On the average, the volume of a single chain in solution is 10 times the volume of a dry particle at the corresponding temperature. Fluctuations of chain volumes that are dominant in solution are also present in the volumes of particles deposited and dried on mica.