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Tribological and Corrosion Properties of Ni-SiC (FGM) Coatings
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
Ni-SiC nanocomposite coatings are considered as corrosion resistant coatings with better tribological properties. In order to get superior properties, the amount of added particles should be increased. But high concentration of particles has some drawbacks such as low adhesion to substrate, probability of cracking in coating due to heat expansion coefficient difference between substrate and coating and also embrittlement of coating and low elasticity. In this study, the possibility of producing Ni-SiC nanocomposite coatings with FGM structure was investigated. SiC particles concentration was 5 to 80 g/l and the current density was between 3 to 5 A/dm¬2. The pH of bath and temperature was...
Scaled nonlinear conjugate gradient methods for nonlinear least squares problems
, Article Numerical Algorithms ; 2018 ; 10171398 (ISSN) ; Mahdavi Amiri, N ; Sharif University of Technology
Springer New York LLC
2018
Abstract
We propose a modified structured secant relation to get a more accurate approximation of the second curvature of the least squares objective function. Then, using this relation and an approach introduced by Andrei, we propose three scaled nonlinear conjugate gradient methods for nonlinear least squares problems. An attractive feature of one of the proposed methods is satisfication of the sufficient descent condition regardless of the line search and the objective function convexity. We establish that the three proposed algorithms are globally convergent, under the assumption of the Jacobian matrix having full column rank on the level set for one, and without such assumption for the other...
Scaled nonlinear conjugate gradient methods for nonlinear least squares problems
, Article Numerical Algorithms ; Volume 82, Issue 1 , 2019 ; 10171398 (ISSN) ; Mahdavi Amiri, N ; Sharif University of Technology
Springer New York LLC
2019
Abstract
We propose a modified structured secant relation to get a more accurate approximation of the second curvature of the least squares objective function. Then, using this relation and an approach introduced by Andrei, we propose three scaled nonlinear conjugate gradient methods for nonlinear least squares problems. An attractive feature of one of the proposed methods is satisfication of the sufficient descent condition regardless of the line search and the objective function convexity. We establish that the three proposed algorithms are globally convergent, under the assumption of the Jacobian matrix having full column rank on the level set for one, and without such assumption for the other...
Synthesis of SiOC/Al2O3 nano/macro composites through PDC method; investigation of potentials as layers of a packed bed reactor membrane
, Article Ceramics International ; Volume 46, Issue 11 , 2020 , Pages 19000-19007 ; Paryab, A ; Rahmani, S ; Akbari, M ; Sarpoolaky, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Thanks to a wide range of pore sizes by nano/macro composites of SiOC/Al2O3, such composites can serve as different layers of the structure of Packed Bed Reactor Membranes (PBRM). In the present study, the Polymer-Derived Ceramics method (PDC) has been used to synthesize nano/macro structures. Firstly, the effect of toluene as an extra carbon source on structure and microstructure of SiOC glass-ceramics was evaluated, such that, 4% (Vol) toluene was recognized as the proper amount to facilitate the synthesis of β-SiC at 1300 °C proved by XRD, Raman spectroscopy, and HR-TEM. Moreover, the presence of micro/meso-porosities was assessed by BET and TEM, indicating the capability of SiOC to serve...