Sharif Digital Repository

Nanocrystalline Al-4 wt% Cu alloy reinforced with nanometric Al2O3 particles was synthesized by in situ reactive milling of Al and CuO powder mixture. X-ray diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM) techniques were employed to study the mechanically induced solid state reaction between the blended powders. The mechanical milling stages were studied by scanning electron microscopy (SEM), bulk density measurement and laser particle size analyzer. It was shown that the reaction between Al and CuO occurs progressively as the mechanical milling continues, leading to formation of nanoscaled alumina particles. The grain refinement of the... 

Electrocatalytic activity of electrodeposited nanocrystalline CoNiFe alloy in hydrogen evolution reaction (HER) was studied in 1 M NaOH solution. The steady-state polarization measurement and electrochemical impedance spectroscopy were used to determine the Tafel slope, the exchange current density and the activation energy. The simulation of the data obtained from these two methods, using a nonlinear fitting procedure, allowed us to determine the surface coverage and the rate constants associated with the mentioned reaction. The ac-impedance spectra measured at various overpotentials in the HER region exhibited three semicircles in the complex plane plots. The high-frequency semicircle was... 

WO3-SiO2 compound thin films were deposited on glass substrates using the sol-gel method, and then all the samples were dried at 100 °C and annealed at 400 °C in air. The effect of WO3 concentration on the hydrophilicity of WO3-SiO2 compound films was studied for the first time and it was shown that the films containing 85 mol% of the concentration possessed a superhydrophilic surface without UV or visible irradiation. Optical properties of the films such as transmittance, reflectance and bandgap energy were investigated using a UV-visible spectrophotometer. According to atomic force microscopy, the surface ratio was maximized in 85 mol% concentration of WO3 similar to hydrophilicity.... 

The nitrate-citrate gel exhibits auto-catalytic behavior, which can be used to synthesize nanocrystalline YIG powders. In this study, yttrium iron garnet (Y3Fe5O12) nanocrystalline powders were prepared by a sol-gel auto-combustion process. The influence of metal nitrates to citric acid molar ratio (MN/CA) of the precursor solution on the combustion behavior and crystallite size of synthesized powders was investigated by scanning electron microscopy (SEM), thermal analyses (DTA/TGA) and X-ray diffraction (XRD). The results show that with increasing MN/CA value, the combustion rate increases and the single-phase YIG forms at a higher temperature. The crystallite size of the single phase YIG... 

The nitrate-citrate gels exhibit auto-catalytic behavior, which can be used to synthesize the nanocrystalline YIG powders. In this study yttrium iron garnet (Y3Fe5O12) nanocrystalline powders were prepared by a sol-gel auto-combustion process. The influence of pH value of the precursor solution on the combustion behavior and the garnet phase formation of synthesized powders were investigated by scanning electron microscopy (SEM), thermal analysis (DTA/TGA), infrared (IR) spectroscopy and X-ray diffraction technique (XRD). The results show that with increasing pH value, the combustion rate increases. The as-burnt powder prepared with pH 1 yielded a single phase YIG after calcination at 800... 

TiO2 and transition metal (Cr, Mn, Fe, Co, Ni, Cu, and Zn) doped TiO2 nanoparticles were synthesized by the sol–gel method using 2-hydroxylethylammonium formate as an ionic liquid. All the prepared samples were calcined at 500 °C and characterized by X-ray diffraction (XRD), BET surface area determination, energy dispersive X-ray (EDX) analysis, diffuse reflectance spectroscopy (DRS), and Fourier transformed infrared (FT-IR) techniques. The studies revealed that transition metal (TM) doped nanoparticles have smaller crystalline size and higher surface area than pure TiO2. Dopant ions in the TiO2 structure caused significant absorption shift into the visible region. The results of... 

TiO2 nanoparticles were prepared by the sol - gel process using 2-hydroxylethy- lammonium formate as an ionic liquid. Nanoparticles were crystallized at various temperatures (300-700°C). The products were characterized using X-ray diffraction (XRD), nitrogen adsorption - desorption isotherms and scanning electron microscopy (SEM) techniques. It was found that the resulting TiO2 nanoparticles had good thermal stability either to resist collapse or the anatase-to-rutile phase transformation during heat treatment. The photocatalytic activity of the nanocrystalline TiO2 was evaluated by the degradation of Acid Blue 92 (AB92) which is\ commonly used as a textile dye. The results showed that the... 

Copper oxide-titania catalysts with nanocrystalline mesoporous structure were prepared by sol-gel technique using tetra isopropyl ortho titanate (TiPT) as the inorganic precursor and amino-2 ethanol as the swelling agent. Characterization was performed using X-ray diffraction (XRD), fourier transformed infrared spectra (FTIR), scanning electron microscopy (SEM), diffuse reflectance UV-Vis spectroscopy (DRS), and N2 adsorption-desorption measurements. It was found that CuO (0.025-0.1 mol ratio) has some effect on the particle size, surface area, pore-volume, pore-diameter, crystallinity of the particles, and crystalline phase of TiO2 nanocrystalline. The results indicated that 0.1 CuO-TiO2... 

Nanocrystalline and nanostructured TiO2-Cr2O3 thin films and powders were prepared by a facile and straightforward aqueous particulate sol-gel route at low temperature of 400°C. The prepared sols showed a narrow particle size distribution with hydrodynamic diameter in the range of 17.7 nm to 19.0 nm. Moreover, the sols were stable over 4 months, with constant zeta potential measured during this period. The effect of the Cr:Ti molar ratio on the crystallization behavior of the products was studied. X-ray diffraction (XRD) analysis revealed that the powders crystallized at low temperature of 400°C, containing anatase-TiO2, rutile-TiO2, and Cr2O3 phases, depending on the annealing temperature... 

This work aims to develop a chemically modified sol–gel synthesis pathway for obtaining various barium titanate nanostructures. The method is able to prepare different BaTiO3 nanostructures such as highly stable nanoparticle embedded colloids, highly transparent amorphous nanolayers, nanocrystalline BaTiO3 powders and ultrathin BaTiO3 nanostructured films directly from a precursor solution. All the products have been prepared at a lower temperature and in a more cost-effective way in contrast to other established sol–gel methods. The results show that the optical transparency of the thin films has been significantly improved in contrast to the similar researches. The deposited thin film is... 

Undoped and copper doped nanostructured zinc oxides were synthesized by using a series of synthetic layered material, undoped and copper doped zinc hydroxide nitrates at various molar percentages of copper (2-10) within the layers as precursors. The layered materials were heat-treated at 500 °C to produce zinc oxide nanostructures with crystallite sizes in the range of 23-35 nm. Optical studies of the nanostructured copper doped zinc oxides showed the decrease in band gap with increasing content of the doping agent, copper  

TiO2 thin films containing different concentrations of Ag nanoparticles have been synthesized by sol-gel method. According to UV-visible spectra, presence of an intense surface plasmon resonance peak at 490 nm of wavelength indicated formation of silver nanoparticles in the TiO2 films. Based on atomic force microscopy (AFM) analysis, the surface roughness and the effective surface ratio increased by increasing the Ag mol%. Moreover, scanning electron microscopy (SEM) images showed formation of Ag nanoparticles on the surface for the samples containing high Ag concentration. X-ray diffraction (XRD) patterns revealed that the size of Ag nanocrystals increased by increasing the Ag content in... 

The aim of this study was to investigate the thermal behavior of Mg-doped calcium phosphate compounds. Nanocrystalline HA and β-TCP mixtures containing different magnesium contents were synthesized via an alkoxide sol gel method. The ratio of (Ca+Mg)P was kept constant at 1.67, and the Mg content ranged between 0 and 3 mol%. The influence of magnesium on the phase composition, chemical structure, thermal behavior and morphological characteristics of nanopowders was analyzed using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Simultaneous Thermogravimetry and Differential Thermal Analysis (STA/DTA), Scanning Electron Microscopy (SEM) and Transmission Electron... 

A modified plastic yield function is proposed to predict the consolidation behavior of nanostructured metal powders and metal-matrix nanocomposite powders under uniaxial compaction. The validity of the model is verified for nanocrystalline Al6063 (~100nm) alloy reinforced without and with 0.8vol.% Al2O3 nanoparticles (~25nm). The plastic deformation propensity of these powders is analyzed by linear compaction equations. The yield stress of the powder compacts is shown to be influenced by the nano-scale grains and the reinforcement nanoparticles  

Microstructural development and phase formation at the interface of yttria stabilized zirconia (3Y-TZP)/430L stainless steel composite layers produced by co-sintering method were studied by SEM, HRTEM, micro-focus XRD, and EPMA. Formation of a rich chromium boundary layer at the interface was noticed, which revealed Cr aggregation at the interface at the elevated temperatures. Misfit dislocations were also observed at the joint interface to tackle the mismatch crystallographic orientations between the ceramic and metal layer. The results of the micro-focus XRD showed formation of no new phases at the boundary zone. Microstructural studies also revealed a retarded grain growth in the...