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Electrophoretic deposition of functionally-graded NiO-YSZ composite films
, Article Journal of the European Ceramic Society ; Volume 33, Issue 10 , 2013 , Pages 1815-1823 ; 09552219 (ISSN) ; Yar, A. Y ; Vafaeenezhad, S ; Sani, M. A. F ; Simchi, A ; Sharif University of Technology
2013
Abstract
Functionally-graded NiO-8. mol % YSZ composite films were prepared by a controlled voltage-decay electophoretic deposition (EPD) process. The films consisted of three layers with varying NiO concentrations and porosities. Effects of different parameters including the type of the organic media, solid concentration, NiO:YSZ ratio, and iodine on the stability of EPD suspensions and deposition kinetics were studied. A stable NiO-YSZ suspension was attained in isopropanol with NiO-YSZ ratio of 60:40 and iodine concentration of 0.5. mM. The composite film contained varying NiO concentration from 46. wt.% near the substrate to 32. wt.% close to the electrolyte with 42. wt% NiO in the intermediate...
Numerical study of oxy-fuel MILD (moderate or intense low-oxygen dilution combustion) combustion for CH4-H2 fuel
, Article Energy ; Volume 99 , 2016 , Pages 136-151 ; 03605442 (ISSN) ; Fazlollahi Ghomshi, A ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
This paper demonstrates a numerical study on the combination of Oxy-Fuel and MILD (moderate or intense low-oxygen dilution combustion) combustions, i.e. OXY-MILD. The N2 of a hot oxidizer was replaced with CO2 and H2O in a MILD combustion test case. The study was conducted using a CFD analysis, a zero-dimensional well-stirred reactor analysis, and a reactors network analysis. In the CFD analysis, RANS equations with modified k-ε equations were solved for a 2D-axisymmetric computational domain. Results showed a decrease in temperature gradient, reaction rate, and Damköhler number under the OXY-MILD condition in comparison with the MILD one. It seems the higher the oxygen level in the...
Pressureless sintering of 3Y-TZP/stainless-steel composite layers
, Article Journal of the American Ceramic Society ; Volume 91, Issue 11 , 2008 , Pages 3493-3503 ; 00027820 (ISSN) ; Simchi, A ; Tamjid Shabestary, E ; Hartwig, T ; Sharif University of Technology
2008
Abstract
A pressureless sintering method was utilized to fabricate metal/ceramic joints out of yttria-stabilized zirconia (3Y-TZP) and stainless steels (SS). Ultrafine (150 nm) and nanoscale (75 nm) 3Y-TZP particles and micrometric 17-4PH, 316L, and 420 SS (<31 μm) powders were tested. Isothermal and nonisothermal sintering behaviors of the powders and composite layers in hydrogen, argon, and vacuum atmospheres were examined. It was found that the mismatch strain between the zirconia ceramic and SS during cosintering is significant, which leads to bond cracking and joint failure. Nevertheless, interlayer diffusion of Zr, Fe, and Cr and the formation of a reaction zone, particularly during vacuum...
Numerical simulation of nano-carbon deposition in the thermal decomposition of methane
, Article International Journal of Hydrogen Energy ; Volume 33, Issue 23 , December , 2008 , Pages 7027-7038 ; 03603199 (ISSN) ; Saboohi, Y ; Firoozabadi, B ; Sharif University of Technology
2008
Abstract
A comparison of various hydrogen production processes indicates that the thermal decomposition of methane (TDM) provides an attractive option from both economical and technical points of view. The main problem for this process is the deposition of the nano-carbon particles on the reactor wall (or catalyst surface). This research concentrates on the numerical simulation of the TDM process without use of a catalyst to find a technique that decreases the carbon accumulation in a tubular reactor. In this model, the produced carbon particles are tracked with the Lagrangian method under thermophoretic, Brownian, van der Waals, Basset, drag, lift, gravity, pressure and virtual mass forces. In...