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  • Author: Arman Sedghi x
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Abstract

Nickel-cobalt ferrite spinels are ferrimagnetic ceramic materials that possess a great potential for application in highdensity magnetic media, recording, color imaging, ferrofluids, and high-frequency devices. A change of their structure from micro- to nano- improves their properties drastically, therefore many methods have been investigated to fabricate nanopowder of these spinels. Gel combustion method is one of them. In this research, Ni0.5Co0.5Fe2O4 nanoparticles were fabricated via gel combustion method using metallic nitrates as an oxidant and citric acid, glycine and urea as fuels and the effects of fuel type on the reaction behavior, structure and morphology of Ni0.5Co0.5Fe2O4 nanoparticles were investigated. The reaction behavior was studied by thermal analysis method (TGA-DTA), crystallite size of powders was characterized by X-ray diffraction (XRD) and their morphology was studied by FE-SEM. The results revealed that the reaction was initiated in urea, glycine and citric at 219 °C, 197 °C, 212 °C, respectively. Samples fabricated from glycine and citric acid had a pure spinel structure but the others fabricated with urea fuel had iron oxide impurity. The crystallite size of nickel cobalt ferrite nanoparticles was in the range of 58 nm to 64 nm and the nanoparticles were agglomerated.

To evaluate phytohormones effects on stomatal conductance, chlorophyll fluorescence, membrane stability, relative water content and chlorophyll content under salinity, a factorial experiment with 4 replicates was conducted. Treatments were salinity (0, 3.5 and 7 dS/m), phytohormones (control, gibberellic acid and abscisic acid) and wheat cultivars (Gascogen, Zagros, and Kuhdasht). Results showed that a high level of salinity increased chlorophyll fluorescence and relative water content, while membrane stability, chlorophyll content, and stomatal conductance were decreased. Abscisic acid treatment had more effective role in membrane stability. Although membrane stability was much more under gibberellic acid treatment, restoration of membrane stability was considerable under abscisic acid treatment for Gascogen and Kuhdasht cultivars. Spraying of gibberellic acid induced the highest chlorophyll content in the three salinity levels and all of the cultivars. The maximum amount of stomatal conductance was achieved under gibberellic acid treatment. Abscisic acid caused less chlorophyll fluorescence in comparison to gibberellic acid. About relative water content, abscisic acid was effective in high salinity levels so that it caused stomatal closure, which reduced water loss and maintained turgor in plants.