Loading...
Search for:
multilayer-coating
0.005 seconds
Immobilization of functionalized gold nanoparticles in a well-organized silicon-based microextracting chip followed by online thermal desorption-gas chromatography
, Article Microchemical Journal ; Volume 143 , 2018 , Pages 205-211 ; 0026265X (ISSN) ; Bagheri, H ; Zamani, C ; Sharif University of Technology
Elsevier Inc
2018
Abstract
In this survey, firstly, a silicon wafer-based microchip, possessing a 50-cm microchannel with the dimensions of 120 and 60 μm, was manufactured by chemical etching technique. Subsequently, the inner surface of the microchannel was coated with a primary layer of gold nanoparticles synthesized by galvanic displacement. Then a self-assembled monolayer of 3-mercaptopropyltriethoxysilane was immobilized on the first layer. Eventually, a polydimethylsiloxane film with a thickness of 16 ± 1 μm was formed on the walls of the microchannel by means of sol-gel method. Field emission scanning electron microscopy and atomic force microscopy were extensively employed to investigate the status of both...
Electrodeposition and Characterization of Zn-Ni-P/Zn-Ni Multilayer from Citrate Bath
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
The aim of this study was electrodeposition of Zn-Ni-P/Zn-Ni multilayer coatings by single-bath method from a citrate bath to produce a sacrificial coating with high barrier properties compared to Zn-Ni monolayer coating. The coatings that were prepared at 10 mA/cm2 was Zn-Ni-P (Ni-rich and percentage of zinc, nickel and phosphorus, respectively: 40, 50 and 10 %), and the alloy deposited in 60 mA/cm2 were practically Zn-Ni (Zn-rich, 85% zinc) and almost phosphorus free. Galvanostatic pulse deposition method through switching of the current density between the two values mentioned in monolayers (10 and 60 mA/cm2) in different time periods to create bilayers corresponding to the monolayers,...
Electrodeposition of Ni-P/Cu Multilayer, Mechanism Study, Corrosion and Wear Properties
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor) ; Dolati, Abolghassem (Supervisor)
Abstract
The aim of this project is electrodeposition of Cu/Ni-P multi-layer coating and investigating the nucleation and growth mechanisms of the deposits. To evaluate the effect of the selected bath on the kinetics of the process and deposition, cyclic voltammetry and chronoamperometry studies were conducted and electrodeposition mechanism was obtained three-dimensional instantaneous nucleation and growth controlled by diffusion. Potentiostatic pulse-deposition method with potential steps -0.3 and -1.1 V vs SCE was selected for deposition of Cu/Ni-P multi-layers. In order to demonstrate the effect of monolayer thickness on the properties of the final coating, multiple layers with various monolayers...
Evaluation of hot corrosion behavior of plasma sprayed thermal barrier coatings with graded intermediate layer and double ceramic top layer
, Article Surface and Coatings Technology ; Volume 288 , 2016 , Pages 36-45 ; 02578972 (ISSN) ; Javadi, A. H ; Ghasali, E ; Shahbazkhan, A ; Shakhesi, S ; Sharif University of Technology
Elsevier
2016
Abstract
In the present work, the hot corrosion behavior of two types of multilayer plasma sprayed TBC were investigated and compared with functionally graded and conventional TBCs. These kinds of multilayer coatings consisted of nano/μ alumina as a top coat on YSZ layer, a metallic bond coat and a functionally graded intermediate layer deposited between YSZ and bond coat layers. All the layers were sprayed on the Ni-base super alloy substrate. The hot corrosion resistance of the plasma sprayed coatings was examined at 1050 °C for 40 h, using a fused mixture of 45 wt% Na2SO4 + 55wt%V2O5. Before and after hot corrosion, the microstructure and phase analysis of the coating were studied using scanning...
Ni-P/Zn-Ni compositionally modulated multilayer coatings – part 2: corrosion and protection mechanisms
, Article Applied Surface Science ; Volume 442 , 2018 , Pages 313-321 ; 01694332 (ISSN) ; Ghorbani, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
The Ni-P/Zn-Ni compositionally modulated multilayer coatings CMMCs were electrodeposited from a single bath by switching the deposition current density. The corrosion resistance of the deposits was studied and compared with that of monolayers of Ni-P and Zn-Ni alloys via Tafel polarization, EIS and salt spray tests. Characterization of corrosion products by means of EDS and XRD revealed more details from the corrosion mechanism of the monolayers and multilayers. The corrosion current density of Ni-P/Zn-Ni CMMCs were around one tenth of Zn-Ni monolayer. The CMMC with incomplete layers performed lower polarization resistance and higher corrosion current density compared to the CMMC with...
Ni-P/Zn-Ni compositionally modulated multilayer coatings – part 1: electrodeposition and growth mechanism, composition, morphology, roughness and structure
, Article Applied Surface Science ; Volume 442 , 2018 , Pages 275-287 ; 01694332 (ISSN) ; Ghorbani, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
The Ni-P/Zn-Ni compositionally modulated multilayer coatings CMMCs were electrodeposited from a single bath by switching the cathodic current density. The composition, surface morphology, roughness, layers growth pattern as well as the phase structure of deposits were extensively studied via SEM, EDS, AFM and XRD analysis. Effects of bath ingredients on the electrodeposition behavior were analyzed through cathodic linear sweep voltammetry. Although the concentration of Zn2+ in bath was 13 times higher than Ni2+, the Zn-Ni deposition potential was much nearer to Ni deposition potential rather than that of Zn. Addition of NaH2PO2 to the Ni deposition bath considerably raised the current...