Sharif Digital Repository

This study was focused on the heavy metal (Ni, Co, Mo, V, Mn, Fe, W and Zn) tolerance of fungi strains Aspergillus niger, Aspergillus foetidus and Penicillium simplicissimum. Aspergillus niger was exposed to a mixture of Mo, V and Mn at a mass ratio of 1:2:6 as approximately present in the spent refinery processing catalyst. This study highlights the adaptation of fungi strains to Tungsten and Vanadium to high concentration. The effect of different metals and metal concentration on different strains of fungi was evaluated. Results showed that Ni was one of the most toxic metals for strains of Aspergillus and Penicillium. Aspergillus foetidus was the least tolerant, in particular for Ni, Co... 

The objective of this work was to study the influence of titanium on API 5L-X70 steel weld metal properties at manganese levels of 1.4 and 2%. The best mechanical properties in the weld series were obtained in two compositions, i.e. 1.92%Mn-0.02%Ti and 1.40%Mn-0.08%Ti. In both groups of welds, acicular ferrite in the microstructure was increased with addition of titanium in the range of 0.02-0.08%. Manganese helped to refine and homogenize weld microstructures. Increased hardenability of the weld due to further addition of titanium or manganese encouraged grain boundary nucleation of bainite with greater frequency than intragranular nucleation of acicular ferrite. Also, the amount of... 

Partial substitutions of Pr and Ce are known to suppress the superconducting state in REBa2Cu3O7-δ systems. We have substituted Ce for Gd in Gd1-xCexBa 2Cu3O7-δ compounds with x = 0.0-0.6 by the standard solid-state reaction technique. X-ray diffraction (XRD) experiments are performed and their results are refined by the Rietveld method. XRD analysis shows a predominantly single-phase perovskite structure with few impurity phases. Our resistivity results show that, by increasing the Ce content, Tc decreases, the transition temperature width increases, and in the normal state a metal-insulator transition (MIT) occurs at x c = 0.12. The normal state resistivity of the samples and their slopes... 

This paper reports on the recovery of zinc, cobalt and manganese by two-step leaching of zinc-plants purification residue with sulfuric acid. The residue, hot filter press cake (HFC), contains 14 % ZnO, 4.8 % Co 3O4 and 22.9 % MnO. Effects of different parameters are determined and used to optimize the process. With acid to hot filter press cake (HFC) stoichiometry of 0.85, acid concentration of 30 g/L and temperature of 25°C, it took two minutes to separate zinc from zinc plant residue. Hydrogen peroxide (H2O2) was used as an oxidation agent. The most suitable acid concentration for leaching of both cobalt and manganese was 50 g/L. Recovery of cobalt and manganese increased with peroxide... 

A series of nano-polycrystalline alkali metal doped in La-based manganites (La1 - y Ky)0.7 Ca0.3 MnO3 samples (y = 0.0, 0.1, 0.2, and 0.3) were synthesized using the polymerical complex sol-gel method. The structural properties are studied via the X-ray diffraction experiments, and results are refined by the Rietveld method. The electrical transport properties of the polycrystalline samples have been investigated in the temperature range 50-300 K and a magnetic field up to 10 kOe. The metal-insulator transition temperature (Tp) changes with doping due to the difference between the electron configuration and ionic radius of the dopants and manganese trivalent ions. Characteristic grain... 

In this research, an attempt was made to investigate the potential of nanophotocatalysts for treatment of hazardous wastewater streams. Titanium dioxide nanoparticles (as photocatalyst) were immobilized on a porous and low-density support called "perlite" using a very simple and inexpensive method. TiO2-coated perlite granules were used in a "Floating-bed photoreactor" to study the photocatalytic purification process of a typical wastewater polluted by furfural. The effects of initial concentration, catalyst mass/solution volume ratio, oxidant molar flow, residence time, and light intensity on process removal efficiency, and kinetics of the reactions were studied. SEM analyses showed a... 

The aim of this work is to study the effect of cooling rate and subsequent hot consolidation on the microstructural features and mechanical strength of Al-20Si-5Fe-2X (X = Cu, Ni and Cr) alloys. Powder and ribbons were produced by gas atomization and melt spinning processes at two different cooling rates of 1 × 105 K/s and 5 × 107 K/s. The microstructure of the products was examined using optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The particles were consolidated by hot pressing at 400 °C/250 MPa/1 h under a high purity argon atmosphere and the microstructure, hardness and compressive strength of the compacts were evaluated....