Date

2017

Author

Acet, Nurcan

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Due to their high hardness, anti-corrosion and anti-wear properties, Nickel/ceramic particle composites have gained significant attention as environmentally-friendly alternatives to chromium and cadmium based coatings typically used in the aerospace industry. Electrodeposition of these Ni/ceramic particle composites has the advantage of lower operating cost and operating temperature than the conventional production methods. Incorporation of ceramic nanoparticles into the Ni matrix has a significant effect on the tribological and mechanical properties of these composites. However, high and uniform particle incorporation into the deposit depends greatly on the dispersion of these nanoparticles in the electrolyte. Therefore, to get superior properties, the agglomeration of the nanoparticles in the electrolyte should be decreased while increasing the nanoparticle incorporation into the deposit. However, a major challenge in this regard is that the dispersants that are used to stabilize the particles in the electrolyte can significantly affect the electrodeposition kinetics. The aim of this study is to investigate the effect of a cationic dispersant which is polyethyleneimine (PEI) on the electrodeposition of Ni/TiC nanocomposites. The effect of the dispersant on the particle stability in the electrolyte, on the nanoparticle incorporation rate into the deposit as well as on the electrodeposition kinetics were investigated. Firstly, zeta potential measurements were performed in order to determine the effect of PEI on the particle dispersion in the electrolyte. Secondly, the effect of PEI on the electrodeposition kinetics was investigated using Linear Sweep Voltammetry (LSV) technique and current efficiency measurements. Finally, the amount of TiC in the nanocomposite was analyzed using Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM/EDS). The optimum PEI bath concentration that increases particle dispersion in the electrolyte and TiC vol.% in the nanocomposite without suppressing the electrodeposition was determined as 125 ppm. In addition, the effect of particle bath concentration on the Ni/TiC electrodeposition was characterized and the optimum TiC concentration was determined as 5 g L-1. Moreover, the effect of current density on the Ni/TiC electrodeposition was investigated and it was seen that TiC incorporation decreases with increasing current density. The effect of rotation speed on TiC incorporation was also characterized and the highest incorporation was achieved at 900 rpm rotation speed. Finally, morphological and mechanical characterization of produced nanocomposites were done and compared to pure Ni coating. Uniform distribution of TiC particles in the metal matrix was observed with the addition of 125 ppm PEI into the electrolyte. Furthermore, the hardness of Ni/TiC nanocomposites was higher than pure Ni coating. 

Subject Keywords

Electroforming., Electrochemistry., Nickel-titanium alloys., Nanocomposites (Materials).

URI

http://etd.lib.metu.edu.tr/upload/12621038/index.pdf
https://hdl.handle.net/11511/26480

Collections

Graduate School of Natural and Applied Sciences, Thesis