Showing 4 results for Sadrnezhaad
K. Sadrnezhaad and H. Ahmadian,
Volume 17, Issue 2 (4-1998)
Abstract
In this research a Cu-Zn-Al alloy is produced by melting the raw materials in an electric resistance furnace and then pouring it into a steel mould. The optimum way to achieve the final analysis in the hypo-eutectoid range is determined and the influence of the alloying element, Ti on the grain size and the shape memory properties of the samples are investigated. Solution treatment (done at 850˚C) followed by quenching in ice-water mixture results in the formation of the martensitic structure and the shape memory effect. Aging at temperatures bellow 200˚C results in the reduction of transformation temperatures, while aging at temperatures between 200˚C and 350˚C results in the enhancement of these temperatures and at temperatures above 350˚C results in the destruction of the shape memory properties. Effect of super-elasticity at 40˚C (between Md and Ms) is observed and tensile tests are run at 25˚C and -55˚C to verify the influence of the prevailing phase.
S. Daneshvar E Asl, S. K. Sadrnezhaad,
Volume 36, Issue 3 (Journal of Advanced Materials-Fall 2017)
Abstract
TiO2/MWCNT nanocomposite thin films containing different percentages of multi-walled carbon nanotubes were coated on fluorinated tin oxide substrates by sol-gel dip coating method. Results of X-ray diffraction analysis indicated that the crystal structure of the coatings was anatase TiO2. It was also understood that the size of crystallites reduced with CNT but structural properties and equilibrium phase remain intact. Field emission scanning electron microscope images showed that CNTs dispersed uniformly among 45 nm spherical TiO2 particles of close relations. These images also showed that CNT promoted cracks on the coated surface. Results of the UV-Vis spectroscopy showed that the visible light range adsorption increased with CNT and the absorption edge did not significantly differ with the pure TiO2 layers.. Results of the photoluminescence spectroscopy revealed that the presence of CNT could reduce the pair electron–electron holes recombination which is considered totally undesirable.
S. Daneshvar E Asl, S. Kh. Sadrnezhaad,
Volume 37, Issue 2 (Journal of Advanced Materials-Summer 2018)
Abstract
Rutile-phase titanium dioxide nanorod arrays were prepared by the hydrothermal method. Then, anatase-phase nanoleaves were successfully synthesized on the nanorod arrays via mild aqueous chemistry. Nanorod arrays scanning electron microscopy revealed that the thin film is uniform and crack free and the average diameter and height of the nanorods are 90 nm and 2 µm, respectively. Furthermore, nanorods are vertical to the substrate surface and have desired coverage density due to the predeposition of TiO2 seed layer which leaded to decrease the surface roughness of the substrate. Nanoleafed nanorods scanning electron microscopy indicated that the nanoleaves were grown uniformly on the entire surface of nanorods and the specific surface area and roughness factor of those are significantly improved. Energy dispersive spectrums suggested that F- and Cl- ions are partially doped into TiO2 crystals. Raman and X-ray spectra confirmed the formation of anatase-phase nanoleaves on the rutile-phase nanorods. X-ray diffraction also indicated that the nanorod arrays are highly oriented with respect to the substrate surface. The diffused reflectancetransmittance data revealed the incident light was more efficiently harvested by the nanoleafed nanorod thin film and the values of energy gap are 2.78 and 2.82 eV for rutile TiO2 nanorod and rutile+anatase TiO2 nanoleafed nanorod thin films, respectively. Synthesized nanostructure, having improved charge separation and transfer (due to the presence of the surface anatase/rutile junctions), high specific surface area and light harvesting (due to the presence of the nanoleaves) and low band gap energy (due to the nonmetallic elements doping), is viable alternative to traditional single crystalline TiO2 nanorods for highly efficient photoelectrochemical applications.
T. Rajabi, M. Vahedi, S. K. Sadrnezhaad,
Volume 39, Issue 2 (Journal of Advanced Materials-Summer 2020)
Abstract
Zinc/zinc oxide nanoparticles are used in an increasing number of medical and industrial applications due to their attractive physical, chemical and antibacterial properties. Therefore, achieving a simple and beneficial way to produce them is an important aspect. In this study, zinc/zinc oxide nanopowders were synthesized by fast electric discharges between two electrodes of (a) a spark device in distilled water medium and (b) a handmade high-voltage ignition machine in argon gas medium. The resulting powders were characterized by x-ray diffraction (XRD), dynamic light scattering (DLS) and field emission electron microscopy (FESEM). Using the spark device in distilled water, a mixture of zinc crystals with an average diameter of 11.28 nm and zinc oxide crystals with an average diameter of 22.22 nm was produced. However, using the handmade device in argon, zinc crystals with an average diameter of 7.5 nm were obtained and subsequently oxidized due to their extremely high activity. The production rate of the high voltage discharge method was lower than other conventional methods. On the other hand, its ability in reducing the size and increasing the particle activity was higher than other methods.
