جستجوی مقالات مرتبط با کلیدواژه "grain size" در نشریات گروه "شیمی"

The research presents the synthesis and fabrication of dye-sensitized solar cells (DSSCs) on the influence of sodium arsenic on the enhancement of TiO2/dye as photosensitizers, where Hibiscus sabdariffa (roselle) and Vernonia amygdalina (bitter leaf) were used as a source of the chlorophyll, sodium arsenic (NaAs) material of different concentration (0.1-0.4 mol), was synthesized as a layer on top of TiO2. The surface morphology study of TiO2/NaAs0.1, TiO2/NaAs0.2/ bitter leaf dye, TiO2/NaAs0.3/ roselle dye, and TiO2/NaAs0.4/the mixture of bitter leaf dye and roselle dye revealed that the micrograph is usually defined with the granular shape of nanotubes. The grain size of TiO2/NaAs0.1 is not too large and delineated by an immense sum of aggregated nanoparticles. The cells structure is polycrystalline with a most outstanding peak at 2 theta angles of 26.73° and 51.84o corresponding to hkl index numbers (111) and (202). The films have a very high absorbance from the plot, and the absorbance of the films increases as the dye molecules vary. The high absorbance of the films shows that the DSSCs will be a good material for photovoltaic applications. The fill factor of the films is 0.54, 1.24, 1.23, and 0.99 respectively while the conversion efficiency of 0.86%, 4.48%, 3.44%, and 1.81% was recorded.

Additive interfacial engineering is a strategy to enhance the performance of perovskite solar cells (PSCs). The high-quality perovskite active layer, with defect-free, plays a key role in the performance of the solar cells. In this paper, dopamine hydrochloride (DA), as an organic ligand was incorporated into the CH3NH3PbI3 perovskite precursor solution, and the effects of DA addition on the microstructure of perovskite films and the photovoltaic properties of the PSCs have been studied. It is found that the addition of DA in perovskite precursor is a promising strategy for obtaining compact and uniform CH3NH3PbI3 film, whic can effectively reduce the recombination of charge carriers. The PSCs grown with DA additive in perovskite precursor, significantly show enhanced photovoltaic performance. An optimum power conversion efficiency (PCE) of 13.57% with Voc (1.03 V), and good producibility compared to the pristine one was achieved in the PSCs with 0.6 wt% DA additive in the perovskite precursor.

The catalytic reaction of iridium nanoparticles was carried out over gamma aluminagranules to investigate the factors controlling the catalytic activities.The evaluation of iridium nanoparticle activity in the laboratory reactor wasdone for support grains with different diameters between 1 mm to 4 mm. Thecharacterization of three iridium catalysts was evaluated by XRD, FESEM andEDX before and after catalytic activity. The rate of hydrazine decomposition andhydrogen selectivity increased to 306 h-1 and 42% with the better distributionof nanoparticles, regardless of the grain size of catalyst support, whereas thehydrazine decomposition rate was larger for smaller supported catalysts. Theprobability of hydrazine monohydrate molecules in contact with active sitesbecomes higher and the movement of reactants and gas products will be easyinside and outside the pores, leading to the increase in reactivity. The rate of thehydrazine monohydrate decomposition and H2 selectivity decreased to 216 h-1and 26% with the lower catalyst grains and the higher size of support along withworse distribution on the surface. The remarkable results of results prove thatsupport granule size is a dominant factor in catalytic decomposition.

Abstract. Cubic crystalline oxides such as Y2O3 and MgO is used to stabalized zirconia phases at high temperature. In this paper the Y2O3 powder was added to stabilized zirconia and preparing a mixture of MgAl2O4 Spinel by mixing 1mol of nano-MgO with 1 mol of nano-Al2O3 powders. The spinel was added to the Y2O3-ZrO2 by various weight percentage (5, 10, 15, 20 and 25 wt%), and after that the specimens was prepared by axial pressing and sintered at 1550 oC for 4 hours as soaking time. The grain size was tested by using Atomic Force Microscopy (AFM) and calculated for surface of specimens and it was found to be decreasing (> 0.6 µm) to (~ 108 nm). The thermal properties were clearly influenced by the structural characteristics of the MAS. The thermal conductivity and thermal diffusion was decreased slightly from 5.7 to 5.5 W/m.K and from 2.5 to 1.5 mm2/s, respectively. The thermal capacity was increased from 483 to 615 J/kg.K, and thermal expansion coefficient was increased from 10 to 7.510-6 oC-1 due to the compatibility of thermal expansion coefficients of (Y-PSZ)-MAS oxides. Thermal properties values are compatible with thermal insulation requirements in energy storage applications.

Nanostructured ZnO thin films were prepared by sol-gel dip coating technique. Zinc acetate and ammonium hydroxide were used as precursors and ethanol was as solvent. Ammonium hydroxide (NH4OH) solution was added drop-wise under vigorous stirring to obtain the sol-gel of different pH (varying from 6.9 to 7.2). ZnO thin films were obtained by dipping the glass substrates for few seconds and then dried in air at room temperature. This process was repeated for different number of coats for the typical sol. Different numbers of coating cycle was employed to obtain the films with varying thicknesses. These films were annealed at 5000C and were characterized by x-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis of x-rays (EDAX). ZnO thin films obtained from sol-gel dip-coating technique were observed to nanostructured. Average particle size was observed to be smaller than 50 nm. The most of the particles were observed to be spherical in shape. ZnO films were observed to be nonstoichiometric (Zinc deficient) in nature. The results were discussed and interpreted.