فصلنامه نانو مواد
پیاپی 14 (تابستان 1392)

To clarify the role of nanostructuring process on performance of Ni/GDC cermet anode for low temperature solid oxide fuel cell (LT-SOFC), the anode microstructure of NiO/Ce0.8Gd0. O2-δ (NiO/GDC20) was modified by infiltration of palladium chloride solution. By employing electrochemical Impedance spectroscopy analysis, the effect of Pd-infiltrating on the anodic performance was examined using a symmetric Ni–GDC20/GDC20/Pt electrolyte-supported cell at 400-600 °C. Microstructural development during the infiltrating was investigated by AFM, SEM, TEM, and XPS techniques. The results showed effectiveness of Pd-infiltrated nano particles on the decrease of anodic polarization resistance. It is found that the nanostructural development of Ni/GDC anode via nano-network formation significantly improves the anodic performance.

In this paper, the effect of MgCl2 addition on the formation of MA spinel nanoparticles at 400 °C was investigated. For this reason, the stoichiometric mixture of MgCO3 and calcined aluminum was calcined at 1100 °C for 1 h. Then, the calcined composition was wet-milled and after addition of 6% MgCl2 the compositions were pressed and fired at 400 °C. The thermal behavior of compositions was evaluated by STA. Besides, the phase composition and microstructure of sintered samples were studied by XRD and FE-SEM, respectively. The results showed that MgCl2 addition leads to formation of spinel at 400 °C. The microstructural evaluations confirmed the formation of spinel nanoparticles with addition of MgCl2.

In this paper the effect of Al-water nanofluid, as working fluid, on the efficiency of a parabolic solar collector was investigated numerically. The temperature field, thermal efficiency, mean-outlet temperatures have been evaluated and compared for the conventional parabolic collectors and nanofluid based collectors. Further, the effect of various parameters such as concentration ratio, volume fraction of nanoparticles, receiver length and fluid velocity has been studied. The results show that, in comparison with water as absorption medium using the nanofluids as working fluid increase the efficiency.

Co3O4 and NiO nanoparticles with the particle size of 17-20 nm were successfully synthesized through a simple sol-gel method by using aliphatic dicarboxylic acids as precursors. The effect of organic acids (succinic and glutaric acids) as a chelating agent on morphology of nanoparticles was investigated. Nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD) analysis. The examination of (TEM) also showed that the nanocrystallites were closely bonded and homogeneously distributed at the nanometric scale. It was indicated that the kind of acid played an important part in overcoming the agglomerations and the prepared nanocrystallites have better morphology and uniform granularity. The chemical structure information of the products was studied by Fourier transform infrared (FT-IR) spectroscopy. A possible mechanism was showed which proposed an optimum temperature to remove nickel impurity from composite in calcinations of nickel salt.

In this study, titanium dioxide nanostructures have been synthesized via hydrothermal method. Also the influence of various parameters on how to approach the synthesis of this compound was studied. Phase development and morphology of powder was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. According to the results, synthesized of nanostructures titanium dioxide in anatase phase at temperatures below 200 °C were performed. Increase in temperature leaded to increase in the degree of crystallinity of the powder, however had not much impact on the average of grain size. According to the studied the most important parameter in the carried out the phase transformation in the low temperature, is the initial pH of the solution, reduce of that will be increase the anatase to rutile transformation process.

NiTi matrix composites reinforced with Al2O3 nanoparticles have been synthesized by mechanical alloying of Ni and Ti in the presence of Al2O3 nanoparticles and consolidated by hot isostatic pressing (HIP). Microstructural studies revealed that the sintered composites have a complex phase structure including B2 and B19’ NiTi and Ni-rich (Ni3Ti) and Ti-rich (NiTi2) phases. Nanoindentation test results demonstrated that both hardness and elastic modulus were considerably increased in the composite samples in comparison with pure NiTi, while the pseudoelasticity was not significantly reduced. The wear test results confirmed the improved wear performance of NiTi matrix after the addition of nanoparticles under both low and high loads can be mainly attributed to superior mechanical properties combined with pseudoelasticity effect of the composite samples.

Effect of magnesium on phases and chemical structures, unit cell parameters and biocompatibilityof sol-gel derived calcium phosphates has been studied in this research. The ratio of (Ca)/P was kept constant at 1.67 and the Mg content ranged between 0 and 3% mol. The phase composition, chemical structure and morphological analyses were performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Transmission electron microscopy (TEM). According to the XRD results, the presence of Mg led to the formation of Mg-doped tricalcium phosphate (β -TCMP) and Mg-doped hydroxyapatite (Mg-HA). However, a small amount of MgHPO4.3H2O and MgO were formed at low and high magnesium content samples, respectively. The measured lattice parameters of apatite phase decreased in both a and c-axis with respect to the pure HA phase. Also the specific peaks of β-TCP phase shifted significantly to higher 2 theta in the Mg-doped sample. TEM experiments revealed distinct nanoparticles and aggregates composed of nanoparticles with a size ranging from 80-140 nm.