The electrodeposition of composite materials using deep eutectic solvents
thesisposted on 08.07.2011, 12:42 by Khalid El ttaib
Composite materials are important for their improved strength and wear resistance compared to pure materials. Metal composites have been electrodeposited from aqueous solutions although the instability of colloidal dispersions makes it difficult to obtain reproducible composite compositions. In this thesis metal composites are prepared using Deep Eutectic Solvents, DESs, which are a type of ionic liquid. The electro-deposition of copper and copper composites from DESs based on ethylene glycol and urea were investigated. The mass transport in both electrolytes was found to be diffusion controlled. The mechanism of copper nucleation is studied using chronoamperometry and it is shown that 3D progressive nucleation leads to bright nanostructure deposits. It was found that dispersed colloidal particles are stable over a prolonged period of time in DESs. This work uses an electrochemical quartz crystal microbalance (EQCM) to monitor both the current efficiency and the inclusion of inert particles into the copper co-deposits. The technique showed the majority of second phase was dragged onto the surface instead of sedimented. The effect of the addition of surfactants was also studied. DESs were also used in the electro-deposition of silver composites with alumina and silicon carbide. It was found that improved mechanical properties such as hardness and wear resistance could be obtained. The addition of LiF to the Type 3 deep eutectic solvents was also found to further improve the quality of the mechanical properties and led to smoother surfaces with lower friction coefficients. The final part of this study involved the deposition of nickel composites with the aim of producing coatings with hardness similar to chromium. The addition of organic additives as brighteners (ethylene diamine) leads to smooth and bright finishes. Two types of composites were added to the nickel electrolytes; SiC 1-3μm and Teflon μm. The surface morphology was found to change with particle size and type. The mechanical properties were studied and found to be affected by the type and the concentration of particulate incorporated in the nickel deposits.