Showing 4 results for Concentration
Mirbagheri S.m.h., Chirazi A.,
Volume 2, Issue 3 (9-2005)
Abstract
A numerical model has been developed for the determination of liquid flow permeability through columnar dendrite during growth. The model is inclusive two stages, first numerical evolution of the dendrite shape during growth, and second numerical determination of the interdendritic liquid permeability. Simulation results shown which solute concentration by evolution of dendrite shape could result to reduction of the permeability during solidification time. Comparison between the experimental data from other authors and the present numerical model data, for the low and high solid fractions, has shown a good agreement rather than current numerical models. Therefore present permeability model, in this investigation, could be used for all of the micro solidification codes by coupling on the segregation and the Fick's equations in domain of the inter-dendritic liquid for mushy alloys.
Hosseini Sh., Arabi H., Tamizifar M., Zeyaei A.a.,
Volume 3, Issue 1 (6-2006)
Abstract
In this research, rotating bending fatigue test at minimum to maximum stress ratio of R=-1 was used for investigating the fatigue behavior of Ti-6Al-4V alloy. Both smooth and notched specimens, with elastic concentration factor, kt, of approximately 3.6 and 4.1 were used for this purpose.In addition, the effect of variation in ultimate tensile strength, UTS, on the fatigue behavior of this alloy was studied. S-N curves were drawn and the value of notch sensitivity was obtained or each case.The results showed that the presence of notch in Ti-6Al-4V alloy has a different amount of sensitivity when the notched specimens were subjected to high cycle fatigue (HCF) and low cycle fatigue (LCF) tests. However, the notch sensitivity of this alloy was shown generally to be much lower than steel alloys with similar UTS values. Thus, considering the high compatibility of this alloy with the body environment and its low sensitivity to notch, one can strongly recommend this alloy for use in biomedical application.
A. Fattah-Alhosseini, H. Farahani,
Volume 10, Issue 4 (12-2013)
Abstract
The effects of H2SO4 concentration on the electrochemical behaviour of passive films formed on AISI 304 stainless steel were investigated using by potentiodynamic polarization, Mott–Schottky analysis and electrochemical impedance spectroscopy (EIS). Potentiodynamic polarization indicated that the corrosion potentials were found to shift towards negative direction with an increase in solution concentration. Also, the corrosion current densities increase with an increase in solution concentration. Mott–Schottky analysis revealed that the passive films behave as n-type and p-type semiconductors at potentials below and above the flat band potential, respectively. Also, Mott– Schottky analysis indicated that the donor and acceptor densities are in the range 1021 cm-3 and increased with solution concentration. EIS data showed that the equivalent circuit Rs(Qdl[Rct(RrQr)]) by two time constants is applicable.
M. Ghamari, M. Ghasemifard,
Volume 17, Issue 2 (6-2020)
Abstract
In this research, the dependence of the optical band gap of nano gamma alumina on the OH/Al ratio and concentration of aluminum sulfate is measured through diffuse reflectance spectroscopy (DRS) in the range of 900-1100nm. The samples were prepared via sol-gel method. The results showed that the band gap is pH and concentration-dependent but in a different way. The direct band gap of alumina was determined to be 3.40, 4.37, 3.90, and 3.65 eV for samples prepared at pH 6, 7, 8, and 9, respectively. A decreasing trend was observed with increasing pH (except for pH6). The lowering of the band gap may be associated with the variations in particles size during synthesis due to the quantum size effect. The values of the band gap increased significantly through increasing concentration from 3.90 to 5.65 eV for 0.1M to 0.3M. The role of concentration in band gap control is remarkably more than pH.
