Browsing by Subject "X ray analysis"

Now showing 1 - 7 of 7

Open Access
Effects of laser ablated silver nanoparticles on Lemna minor
(Elsevier, 2014) Üçüncü, E.; Özkan, A. D.; Kurşungöz, C.; Ülger, Z. E.; Ölmez, T. T.; Tekinay, T.; Ortaç, B.; Tunca E.
Open Access
Fabrication of flexible polymer–GaN core–shell nanofibers by the combination of electrospinning and hollow cathode plasma-assisted atomic layer deposition
(Royal Society of Chemistry, 2015) Ozgit Akgun, C.; Kayaci, F.; Vempati S.; Haider A.; Celebioglu A.; Goldenberg, E.; Kizir S.; Uyar, Tamer; Bıyıklı, Necmi
Here we demonstrate the combination of electrospinning and hollow cathode plasma-assisted atomic layer deposition (HCPA-ALD) processes by fabricating flexible polymer-GaN organic-inorganic core-shell nanofibers at a processing temperature much lower than that needed for the preparation of conventional GaN ceramic nanofibers. Polymer-GaN organic-inorganic core-shell nanofibers fabricated by the HCPA-ALD of GaN on electrospun polymeric (nylon 6,6) nanofibers at 200 °C were characterized in detail using electron microscopy, energy dispersive X-ray analysis, selected area electron diffraction, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence measurements, and dynamic mechanical analysis. Although transmission electron microscopy studies indicated that the process parameters should be further optimized for obtaining ultimate uniformity and conformality on these high surface area 3D substrates, the HCPA-ALD process resulted in a ∼28 nm thick polycrystalline wurtzite GaN layer on polymeric nanofibers of an average fiber diameter of ∼70 nm. Having a flexible polymeric core and low processing temperature, these core-shell semiconducting nanofibers might have the potential to substitute brittle ceramic GaN nanofibers, which have already been shown to be high performance materials for various electronic and optoelectronic applications.
Open Access
Homogeneity range of ternary 11-type chalcogenides Fe1 + yTe1−xSex
(Springer, 2017) Koz, C.; Rößler, S.; Wirth, S.; Schwarz, U.
The 11-type Fe-chalcogenides belong to the family of Fe-based superconductors. In these compounds, the interstitial Fe is known to strongly influence the magnetic and superconducting properties. Here, we present the chemical homogeneity range of ternary compounds Fe1 + yTe1−xSex based on powder x-ray diffraction, energy dispersive x-ray analysis, and magnetization measurements. Our investigations show that the maximum amount of excess Fe in homogeneous Fe1 + yTe1−xSex decreases with increase in Se substitution for Te. Using our synthesis procedure, single-phase Fe1 + yTe1−xSex, with 0.5 ≤ x < 1 could not be formed for any amount of excess Fe. Further, the superconducting volume fraction in the material is found to be strongly suppressed by excess Fe.
Open Access
Platinum-palladium loaded polypyrrole film electrodes for the electrooxidation of D-glucose in neutral media
(Elsevier Sequoia SA, Lausanne, Switzerland, 1999) Becerik, İ.; Süzer, Ş.; Kadirgan, F.
Modified polymer films with metal particles incorporated into the films by electrodeposition are known as possible electrocatalysts for various electrode reactions such as fuel cell applications. This work presents some results concerning the electrooxidation of D-glucose at modified polymer film electrodes prepared on a platinum substrate. This reaction has a great deal of interest in view of its applications to detection systems (glucose sensor), fuel cells (pacemakers) and electroorganic systhesis. The modified polymer film electrodes contain platinum and/or palladium particles dispersed in the polypyrrole film by electrodeposition in neutral media. Addition of palladium to platinum modifies the electrocatalytic behaviour of the electrode drastically. The modification is thought to involve minimization of the poisoning of the catalyst, hence increasing its electrode activity.
Open Access
Surface spectroscopic studies of Cs+, and Ba2+ sorption on chlorite-illite mixed clay
(De Gruyter Oldenbourg, 2000) Shahwan, T.; Sayan, S.; Erten, H. N.; Black, L.; Hallam, K. R.; Allen, G. C.
The sorption behavior of Cs+, and Ba2+ on natural clay was investigated using ToF-SIMS, XPS, and XRD. The natural clay was composed mainly of chlorite and illite in addition to quartz and calcite. Depth profiling up to 70 Å was performed at 10 Å steps utilizing ToF-SIMS to study the amount of sorbed Cs+ and Ba2+ as a function of depth in the clay matrix. The results suggest that Cs+ and Ba2+ ions were sorbed primarily by ion exchange coupled with hydrolytic sorption. According to ToF-SIMS and XPS results, the total sorbed amount of Ba2+ was larger than that of Cs+. Quantitative determination of the primary cations within the analyzed clay before and after sorption indicated that for Ba2+ sorption, Ca2+, Mg2+ and for Cs+ sorption Ca2+, K+ were the major exchanging ions. The XRD spectra of Ba-sorbed clay contained new peaks that were identified as BaCO3.
Open Access
Synthesis and size differentiation of Ge nanocrystals in amorphous SiO 2
(Springer, 2006) Aǧan, S.; Çelik-Aktaş, A.; Zuo, J. M.; Dana, A.; Aydınlı, Atilla
Germanosilicate layers were grown on Si substrates by plasma enhanced chemical vapor deposition (PECVD) and annealed at different temperatures ranging from 700-1010 °C for durations of 5 to 60 min. Transmission electron microscopy (TEM) was used to investigate Ge nanocrystal formation in SiO 2:Ge films. High-resolution cross section TEM images, electron energy-loss spectroscopy and energy dispersive X-ray analysis (EDX) data indicate that Ge nanocrystals are present in the amorphous silicon dioxide films. These nanocrystals are formed in two spatially separated layers with average sizes of 15 and 50 nm, respectively. EDX analysis indicates that Ge also diffuses into the Si substrate.
Open Access
TEM studies of Ge nanocrystal formation in PECVD grown SiO 2: Ge / SiO2 multilayers
(Institute of Physics, 2006) Aǧan, S.; Dana, A.; Aydınlı, Atilla
We investigate the effect of annealing on the Ge nanocrystal formation in multilayered germanosilicate-oxide films grown on Si substrates by plasma enhanced chemical vapour deposition (PECVD). The multilayered samples were annealed at temperatures ranging from 750 to 900 °C for 5 min under nitrogen atmosphere. The onset of formation of Ge nanocrystals, at 750 °C, can be observed via high resolution TEM micrographs. The diameters of Ge nanocrystals were observed to be between 5 and 14 nm. As the annealing temperature is raised to 850 °C, a second layer of Ge nanocrystals forms next to the original precipitation band, positioning itself closer to the substrate SiO2 interface. High resolution cross section TEM images, electron diffraction and electron energy-loss spectroscopy as well as energy-dispersive x-ray analysis (EDAX) data all indicate that Ge nanocrystals are present in each layer. © 2006 IOP Publishing Ltd.