Date of Award

2014

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Physics

Keywords

Pure sciences, Electrochemistry, Electroless, Electroplating, Hybrid electro-electroless deposition, Magnesium, Multi-layers

Supervisor

Schlesinger, M.

Rights

info:eu-repo/semantics/openAccess

Abstract

This dissertation is composed of three distinct but closely related topics on the electrochemical metallization of substrates. The first topic solves the longstanding problem of galvanic corrosion in connection with exploiting the advantageous properties of magnesium {Mg} alloys and is of vital interest to the automotive and aerospace sectors. The second topic provides a new approach to the selective electroless metallization of silicon {Si} in connection with solar cells and other electronic devices. The third topic details a novel method of metal thin film formation using wet chemistry techniques which allow for the deposition of alternating metal layers of different and similar nobility from a single electrolyte. Future possible avenues of investigation are suggested for each of the three topics. The resolution of the galvanic corrosion issue, as presented within herein, is based on the direct electroless deposition of metal thin films less active than the Mg alloy substrates. Claddings of copper {Cu}, nickel boron {Ni-B}, and phosphorous {P} alloys including: nickel {Ni-P}, cobalt {Co-P}, nickel-zinc Ni-Zn-P}, and other ternary alloys, were successfully deposited directly on Mg alloy surfaces. The electroless coating of Mg alloys was accomplished using minimal pre-treatments and made use of the naturally active properties of Mg-based substrates. Qualitative measures of the corrosion resistance of Ni-Zn-P coatings on Mg alloys demonstrated superior resistance to galvanic corrosion compared to uncoated surfaces. The selective electroless metallization of Si is accomplished with the selective removal of the silicon oxide {SiO x } by means of mechanical scribing thereby exposing Si. The exposure of Si provides a catalytic surface for the electroless deposition of gold {Au}, and silver {Ag}, and other metals. The mechanical scribing provides an inexpensive avenue for the selective metallization of Si for solar cells. The novel method of depositing alternating metal layers of both different and similar nobility is achieved by combining electroplating and electroless deposition within a single electrolyte. The technique, termed here "hybrid electro-electroless deposition" (HEED), provides coatings previously unobtainable using wet electrochemical techniques. The application of HEED is of interest for the provision of sacrificial coatings on Mg alloys for corrosion protection within the transportation sector.

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