Browsing by Subject "Solid solutions"

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Open Access
Characterization of niobium-zirconium mixed oxide as a novel catalyst for selective catalytic reduction of NO x
(2009) Cayirtepe, I.; Naydenov, A.; Ivanov, G.; Kantcheva, M.
The performance of mixed niobium-zirconium oxide in the SCR of NO x with propene in excess oxygen has been studied. The mixed oxide is prepared by impregnation of hydrated zirconia with acidic solution (pH 0.5) of peroxoniobium(V) complex, [Nb2(O2)3] 4+, ensuring ZrO2:Nb2O5 mole ratio of 6:1. The calcined sample (denoted as 25NbZ-P) has the structure of Zr 6Nb2O17. According to the catalytic test, the conversion of NO x over the 25NbZ-P catalyst passes through a maximum at 220 °C. Based on the in situ FT-IR results, a reaction mechanism is proposed with nitroacetone and NCO species as the key reaction intermediates. The results of the investigation show that the catalytic properties of the Zr6Nb2O17 solid solution could be of interest regarding the development of low-temperature catalyst for the SCR of NO x with hydrocarbons. © 2009 Springer Science+Business Media, LLC.
Open Access
Investigation on the formation of Cu-Fe nano crystalline super-saturated solid solution developed by mechanical alloying
(2013) Mojtahedi, M.; Goodarzi, M.; Aboutalebi, M.R.; Ghaffari, M.; Soleimanian V.
In this study, the formation of super saturated solid solution in the binary Cu-Fe system was investigated. Three powder blends with 30, 50 and 70 wt.% of Fe were milled for different times to 96 h. The variations of lattice parameter and inter-planar spacing were calculated and analyzed using X-ray diffraction analysis (XDA). The anisotropy of lattice deformation in the FCC phase was studied and the obtained results were compared to milled pure Cu powder. Furthermore, crystallite size was calculated using Scherer formula in comparison with Rietveld full profile refinement method. Considering the previous studies about the formation of non-equilibrium FCC and BCC phases, the phase evolution has been discussed and the proportion of each phase was calculated using Rietveld refinement method. Supplementary studies on the evolution of microstructure and formation of solid solution were carried out using high resolution transmission electron microscopy (HRTEM). Finally, high angle annular dark field (HAADF) imaging was utilized to find out the level of homogeneity in the resulting phases. While true alloying takes place in each phase, the final structure consists of both FCC and BCC nano-crystallites. © 2012 Elsevier B.V. All rights reserved.
Open Access
Synthesis of solid solutions of Cd1-xZnxS nanocrystals in the channels of mesostructured silica films
(Royal Society of Chemistry, 2006) Akdoğan, Y.; Üzüm, Ç.; Dag, O.; Coombs, N.
In this contribution, we introduce the use of metal ion (Cd(ii) and Zn(ii)) modified mesostructured silica as a reaction medium, to produce a solid solution of Cd1-xZnxS nanocrystals as a thin film. With this approach, a true liquid crystalline templating (TLCT) and liquid crystalline mesophase of transition metal salt oligo(ethylene oxide) non-ionic surfactant (((1 - x)[Cd(H2O)4](NO3)2 + x[Zn(H2O)6](NO3)2) CH 3(CH2)11(OCH2CH2) 10OH, (MLC)), systems were collectively used to synthesise mesostructured silica films. The film samples were reacted at room temperature (RT) in an H2S atmosphere to produce zinc blend Cd 1-xZnxS nanocrystals in the channels of mesostructured silica. The initial Zn(ii) and Cd(ii) ion concentrations in the reaction media determine the final composition and band gap of the Cd1-xZn xS nanocrystals. The growth process of the Cd1-xZn xS nanocrystals in the pores is influenced by the silica walls. If the walls are rigid (well polymerized, obtained by aging the samples before H2S treatment), then the Cd1-xZnxS nanoparticles are smaller in size and more uniform in size distribution. © The Royal Society of Chemistry 2006.