Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
2 results
Search Results
Article Citation - WoS: 73Citation - Scopus: 77Zinc Oxide and Zinc Hydroxide Formation Via Aqueous Precipitation: Effect of the Preparation Route and Lysozyme Addition(Elsevier Ltd., 2015) Top, Ayben; Çetinkaya, HayrullahAqueous precipitation products of Zn(NO3)2 and NaOH obtained by changing the method of combining the reactants and by using lysozyme as an additive were investigated. In the case of single addition method, octahedral ε-Zn(OH)2 and plate-like β-Zn(OH)2 structures formed in the absence and in the presence of lysozyme, respectively. Calcination of these Zn(OH)2 samples at 700 °C yielded porous ZnO structures by conserving the template crystals. When zinc source was added dropwise into NaOH solution, predominantly clover-like ZnO crystals were obtained independent of lysozyme addition. Mixed spherical and elongated ZnO morphology was observed when NaOH was added dropwise into Zn(NO3)2 solution containing lysozyme. Lysozyme contents of the precipitation products were estimated as in the range of ∼5-20% and FTIR indicated no significant conformational change of lysozyme in the composite. These results suggest that lysozyme-ZnO/Zn(OH)2 composite materials may have a value as an antibacterial material.Article Citation - WoS: 19Citation - Scopus: 17Preparation and Characterization of Nanocrystalline Titania Powders by Sonochemical Synthesis(Elsevier Ltd., 2012) Çağlar Duvarcı, Özlem; Çiftçioğlu, MuhsinNanocrystalline mesoporous titania powders were synthesized by hydrolyzing titanium isopropoxide in ethanol-water mixtures which were ultrasonically treated without using any templates or chemicals. Titanium isopropoxide-ethanol mixture was added dropwise to a water-ethanol mixture placed in an ultrasonic bath. The properties of the sonochemically synthesized powder were compared with those of the powders prepared without ultrasonic treatment along with Degussa P-25 titania powder. The phase structure, crystallite size, surface area, particle size, powder density were determined and sintering behavior was analyzed in this work. The nanotitania powder prepared during ultrasonic induced hydrolysis (TiO 2-U) was determined to be formed from a mixture of anatase and brookite phases at 25°C. The brookite phase in nanotitania powder prepared without ultrasonic treatment (TiO 2-NoU) was detected at 70°C. The anatase-rutile phase transformation was completed in the 500-700°C range for both powders. The average crystallite sizes of the powders at 25°C were determined as 10 and 5nm for TiO 2-NoU and TiO 2-U, respectively. The surface area decreased from 238 to106m 2/g for TiO 2-NoU and from 287 to 82m 2/g for TiO 2-U when the calcination temperature was increased from 200 to 500°C. The evolution of the N 2 adsorption-desorption behavior with calcination temperature and the corresponding pore size distributions/volumes was attributed to the formation of closely packed submicron aggregates during powder synthesis and calcination. The sintering behavior was concluded to be controlled by 7-10nm crystallites and the submicron aggregates. The determination of the densification behavior of titania powders prepared by different methods with various levels of dopants may prove to be very useful for a better understanding of the phase/pore structure evolution which is crucial for a significant number of applications.