Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 50Citation - Scopus: 53Nanoscale Oxide Growth on Al Single Crystals at Low Temperatures: Variable Charge Molecular Dynamics Simulations(American Physical Society, 2006) Hasnaoui, A.; Politano, O.; Salazar, J. M.; Aral, GürcanWe investigate the oxidation of aluminum low-index surfaces [(100), (110), and (111)] at low temperatures (300-600 K) and three different gas pressure values. We use molecular dynamics (MD) simulations with dynamic charge transfer between atoms where the interaction between atoms is described by the Es+ potential composed of the embedded atom method (EAM) potential and an electrostatic contribution. In the considered temperature range and under different gas pressure conditions, the growth kinetics follow a direct logarithmic law where the oxide thickness is limited to a value of ∼3 nm. The fitted curves allow us to determine the temperature and the pressure dependencies of the parameters involved in the growth law. During the adsorption stage, we observe a rotation of the oxygen pair as a precursor process to its dissociation. In most cases, the rotation aligns the molecule vertically to the Al surface. The separation distance after dissociation ranges from 3 to 9. Atomistic observations revealed that the oxide presents a dominant tetrahedral (Al O4) environment in the inner layer and mixed tetrahedral and octahedral (Al O6) environments in the outer oxide region when the oxide thickness reaches values beyond ∼2 nm.Article Citation - WoS: 98Citation - Scopus: 108Capacity and Mechanism of Phenol Adsorption on Lignite(Elsevier Ltd., 2006) Polat, Hürriyet; Molva, Murat; Polat, MehmetA raw lignitic coal from Soma, Turkey was investigated to determine its potential as an adsorbent for phenol removal from wastewaters. Kinetic batch tests demonstrated that phenol could be completely removed from solution given sufficient solids loading and reaction time. The adsorption capacity of 10 mg/g obtained with the lignite is low compared to those achievable with activated carbons (around 300 mg/g). However, when normalized for the surface area, the adsorption capacity was much larger for the lignite (1.3 mg/m2) than that generally observed with activated carbons (0.05-0.3 mg/m2). Hydrogen-bonding of the phenolic -OH with the oxygen sites on the lignite surface is the most likely mechanism for adsorption. Though water molecules also have affinity for the same oxygen sites, lateral benzene ring interactions make phenol adsorption energetically more favorable. Since phenol molecules adsorbed in this fashion would project their benzene rings into solution, formation of a second layer through the action of the dispersive π-π interactions between the benzene rings is very likely. Residual water quality with respect to major elements and heavy metals was within acceptable limits defined by the ASTM standards. Dissolution of organic matter from the lignite was also observed to be negligible.Conference Object Citation - WoS: 76Citation - Scopus: 80Stability of Microcrystalline Silicon for Thin Film Solar Cell Applications(Institute of Electrical Engineers, 2003) Finger, Friedhelm; Carius, Reinhard; Dylla, Thorsten; Klein, Stefan; Okur, Salih; Güneş, MehmetThe development of microcrystalline silicon (μc-Si:H) for solar cells has made good progress with efficiencies better than those of amorphous silicon (a-Si:H) devices. Of particular interest is the absence of light-induced degradation in highly crystalline μc-Si:H. However, the highest efficiencies are obtained with material which may still include a-Si:H regions and light-induced changes may be expected in such material. On the other hand, material of high crystallinity is susceptible to in-diffusion of atmospheric gases which, through adsorption or oxidation, affect the electronic transport. Investigations are presented of such effects concerning the stability of μc-Si:H films and solar cells prepared by plasma-enhanced chemical vapour deposition and hot wire chemical vapour deposition.