فهرست مطالب ali rostamnejadi

In this study, we have investigated the optical and high-temperature thermochromic properties of yttrium iron garnet powder and paint. The powders were produced using the solid-state reaction technique, and the thermochromic paint was sprayed over an Al alloy substrate. X-ray diffraction patterns, optical and field emission scanning electron microscopes, and UV-Vis and FTIR spectrophotometers were used to assess the structural, surface morphology and optical characteristics of the materials. The thermochromic characteristics of the samples were investigated by extracting the chromatic coordinates L*b*a* from digital pictures taken at temperatures ranging from 25 to 210 °C. The results reveal that when the temperature rises, the color of the paint changes from dark green to dark brown. The charge transfer between oxygen and iron ions, as well as the electron transition across the orbitals of the d layer, could be responsible for the observed reversible color change. The paint has strong thermal stability up to 350 °C which is suitable for high-temperature thermochromic applications.

In this paper, the effects of structural parameters and temperature on the thermal emission properties of a square array of cylindrical nano/microcavities on chromium (Cr) slab have been investigated. The obtained results show that the enhancement and selectivity in the emissivity are depended on the coupling between thermally excited radiation with the resonance modes, surface plasmon-polariton and Bragg diffraction from the surface of the periodic nano/microcavities. For nanocavities with radius r

In this research single phaseLa0.7(Sr 1-xBax)0.3MnO3(x =0, 0.1 , 0.2 , 0.3) nanomanganite with crystalline size of 18-28 nm have been prepared by sol gel method. The structural properties have been studied using X-ray diffraction spectra with its Rietveld analysis and scaning electron microscope images. The magnetic and elctrical properties have been investigated by measuring the ac magnetic susceptibility and resistivity in the presence of magnetic fields in the range of 0-20 kOe. The obtained results from ac magnetic susceptibility show that the Curie temperture of the samples are above room temperture. The results of resistivity show that the metal-insulator phase transition temperture of La0.7 Sr0.3 MnO3 and La0.7 (Sr0.3 Ba0.2) MnO3 compounds are below room temperture. The resistivity of the samples strongly decreases and their magnetoresistance almost linearly increases by incrasing the applied magnetic field at different tempertures. The value of magnetoresistance for La0.7 (Sr0.3 Ba0.2) MnO3 Ecompound is 10 % and 14 % at 275 K and 200 K, and for La0.7 Sr0.3 MnO3 Ecompound is 13 % and 27 % at 275 K and 100 K, respectively which are suitable for magnetic field sensing applications. The magneto-transport properties of La0.7 (Sr1-x Bax) MnO3 nanomanganite are described in terms of spin dependent scattering of charge carriers from grain boundaries and their spin dependent tunneling between grains.

A laboratory trial was conducted to determine whether suspensions of ZnO nanoparticles (ZnO NPs) could interfere with the early growth of fenugreek. This plant species is one of the recommended species by Organization for Economic Cooperation and Development (OECD). Nine concentrations of ZnO NPs (10, 50, 100, 500, 1000, 2000, 3000, 4000, and 5000 mg/L) were prepared in deionized (DI) water (considered as a control). Seed soaking and incubation of seeds in ZnO NPs suspensions were compared. We found that ZnO NPs cannot pass through the seed coat, because neither the seed soaking affect seedling growth nor the germination rate was not affected by ZnO NPs. The root and shoot growth were not affected until 100 and 500 mg/L, respectively, but in concentration more than 100 and 500 mg/L, root and shoot growth negatively were affected. Therefore root growth upon exposure to ZnO NPs was more sensitive than shoot growth.