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Rezaeivala M.,Hamedan University of Technology | Keypour H.,Bu - Ali Sina University
Coordination Chemistry Reviews | Year: 2014

In this paper, there is an attempt to review the developments in the design and synthesis of pyridine containing [1+1] and [2+2] macrocyclic Schiff base ligands, formed by condensations of 2,6-diacylpyridine or 2,6-diformylpyridine and appropriate polyamines, which utilize the templating capability of different metal ions to direct the synthetic pathway. The reduction of the cyclic Schiff bases to their related amine derivatives is also considered since this leads to more flexible ligands capable of structural elaboration through donor groups. Attention is mainly paid to the synthetic and structural aspects of the resulting metal complexes, particularly to the role of the coordination preferences of the different metal ions in directing the synthesis totally or preferentially toward mono-, di- or poly-nuclear entities. The preparation of functionalized ligands, containing pendant arms, capable of promoting rapid complexation and decomplexation and their use in selective metal ion transportation and separation are also paid attention to. Furthermore, a summary of the new approach of these compounds such as mechanically interlocked molecules, catalytic properties and cofactors and artificial metalloenzymes is reviewed. © 2014 Elsevier B.V. Source

The influence of drying temperature, T on the surface structure of polyaniline (PANI) nanostructured films dried at temperatures less than the glass transition temperature, Tg and between Tg and melting temperature, Tm was investigated by atomic force microscopy (AFM) and ZeScope optical profilometry. The expected power law behavior associated with surface roughness over small length scales was confirmed at different drying temperatures. To correlate the value of the film thickness determined based on AFM with that obtained from ZeScope measurements, a model of height correcting factor is introduced. The variation in saturated roughness of the PANI film was determined to follow a power law model in the range of T < Tg, with a saturated roughness exponent of 4.48 ± 0.4. The structure of the PANI film has been investigated based on molecular dynamics simulation. The applicability of power law model was confirmed by simulations, based on which the saturated roughness exponent was determined to be 4.90 ± 0.5. © 2014 Elsevier B.V. Source

Momeni A.,Hamedan University of Technology | Ebrahimi G.R.,Hakim Sabzevari University | Jahazi M.,Ecole de Technologie Superieure of Montreal | Bocher P.,Ecole de Technologie Superieure of Montreal
Journal of Alloys and Compounds | Year: 2014

A physical model based on the evolution of subgrains size is proposed to describe the nucleation and growth processes during discontinuous dynamic recrystallization. The evolution of subgrains to viable recrystallization nuclei was found possible at very low strains. Afterwards, the number of stable nuclei considerably increased on a sigmoidal trend with strain and reached a saturated state at about 0.6 times the peak strain. The dependence of nucleation rate on strain was modeled using an Avrami-type equation and the driving force for the growth of recrystallized nuclei was similarly modeled in terms of strain. It is also shown that "site saturation" is the governing mechanism for the initiation of the discontinues dynamic recrystallization at the grain boundaries. The flow stress of the material was calculated using the law of mixture of recrystallized and unrecrystallized regions with fractional softening as the stress-partitioning factor. Satisfactory agreement between predicted and experimental results was obtained, thereby confirming the validity of the proposed model. © 2013 Published by Elsevier B.V. Source

Afkhami A.,Bu - Ali Sina University | Ghaedi H.,Bu - Ali Sina University | Madrakian T.,Bu - Ali Sina University | Rezaeivala M.,Hamedan University of Technology
Electrochimica Acta | Year: 2013

A new chemically modified electrode was constructed for rapid, simple, accurate, selective and highly sensitive simultaneous determination of lead and cadmium using square wave anodic stripping voltammetry (SWASV). The electrode was prepared by incorporation of new synthesized Schiff base and multi-walled carbon nanotubes (MWCNT) in carbon paste electrode. The limit of detection was found to be 0.25 ng mL-1 and 0.74 ng mL-1 for Pb 2+ and Cd2+, respectively. The stability constants of the complexes of the ligand with several metal cations in ethanol medium were determined. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective. The proposed chemically modified electrode was used for the determination of lead and cadmium in several foodstuffs and water samples. © 2012 Elsevier Ltd. All Rights Reserved. Source

Effects of the deposition process parameters on the thickness of TiO 2 nanostructured film were simulated using the molecular dynamics (MD) approach and modeled by the artificial neural network (ANN) and regression method. Accordingly, TiO2 nanostructured film was prepared experimentally with the sol-gel dip-coating method. Structural instabilities can be expected, due to short- and/or long-range intermolecular forces, leading to the surface inhomogeneities. In the MD simulation, the Morse potential function was used for the inter-atomic interactions, and equations of motion for atoms were solved by Verlet algorithm. The effect of the withdrawal velocity, drying temperature and number of deposited layers were studied in order to characterize the film thickness. The results of MD simulations are reasonably consistent with atomic force microscopy, scanning electron microscopy and Dektak surface profiler. Finally, the outputs from experimental data were analyzed by using the ANN in order to investigate the effects of deposition process parameters on the film thickness. In this case, various architectures have been checked using 75% of experimental data for training of the ANN. Among the various architectures, feed-forward back-propagation network with trainer training algorithm was found as the best architecture. Based on the R-squared value, the ANN is better than the regression model in predicting the film thickness. The statistical analysis for those results was then used to verify the fitness of the complex process model. Based on the results, this modeling methodology can explain the characteristics of the TiO2 nanostructured thin film and growth mechanism varying with process conditions. © 2013 John Wiley & Sons, Ltd. Source

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