جستجوی مقالات مرتبط با کلیدواژه "zno" در نشریات گروه "مکانیک"

In this paper, the effect of impurity injection on the structural, optical and magnetic properties of ZnO nanostructures prepared by sol-gel method was investigated. The Ultraviolet spectroscopy (UV-Vis), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and vibrometer magnetometer (VSM) were used to analyze the samples. The experimental results showed that the addition of impurities caused the displacement of the adsorption peak and the reduction of the band gap. From the XRD spectrum, it appears that all specimens are formed in the Versatite structure. No additional peaks are seen in the spectrum, indicating complete phase formation without creating any secondary phases. The absence of additional peaks indicates the high solubility of iron in oxidation, and the results show that the addition of impurities increased the size of the nanocrystals, while the increase in the percentage of impurities did not affect the size of the nanocrystals. Also, iron impurity has caused ferromagnetic properties in the samples so that with increasing the amount of impurity, the induction field decreases. Ultraviolet spectroscopy (UV-Vis), scanning electron microscopy (SEM) and vibrometer magnetometer (VSM) were used to analyze the samples.

Different catalysts have been developed for in-situ hydrogen production via steam methanol reforming reaction. Attempts are focused on producing catalysts with high conversion and selectivities to produce maximum hydrogen content and minimum amount of carbon monoxide. In the meantime, there are several ways to improve the catalytic properties which can be classified into two major categories: a) addition of promoters; b) change in the synthesis parameters. The purpose of this study is to determine the effects of alumina precursor in the combustion synthesis method for synthesizing nanocatalysts promoted with 5%wt cerium oxide. Two samples with boehmite and aluminum nitrate precursors were synthesized and analyzed via XRD, BET, FESEM, EDX and FTIR to determine their physicochemical properties. CuO and ZnO were detected in XRD patterns and alumina presence was proved via SED-EDX and FTIR, because no peaks could be detected in XRD patterns. FESEM images showed that particles of synthesized samples were in nano range. FESEM analysis also revealed that the particle size of the sample with aluminum nitrate precursor was reduced and a more porous structure was obtained. Catalytic performance studies also exhibited that the sample with aluminum nitrate precursor yields better results in terms of conversion and product selectivities.

The aim of the present study is to investigate the effects of shear rate on dynamic viscosity of MWCNT-ZnO/engine oil hybrid nanofluid. Using two-step method and without using any surfactant, the studied nanofluid has been produced in different solid concentration (0.125, 0.5, and 1%) as the experimental sample. All the experiments were conducted in the temperatures ranging from 5 to 55°C and shear rates ranging from 50 to 1000 RPM. Based on the experimental results, although the base fluid showed Newtonian behavior in all the studied temperatures and shear rates, in the temperatures of 5 and 15°C, the studied nanofluid shows Non-Newtonian behavior while it shows Newtonian behavior in the temperatures of 25, 35, 45, and 55°C.