|M.Sc Student||Elad Nussbaum|
|Subject||The Influence of Titanium on Metal-Ceramic Interfaces|
|Department||Department of Materials Science and Engineering||Supervisor||Full Professor Kaplan Wayne D.|
|Full Thesis text|
Metal-ceramic interfaces and joins are used in numerous applications. Active element additions to promote wetting, spreading and adhesion are commonly used for commercial applications. Two leading theories for the role of active elements in reactive wetting/spreading are common today. The first states that the improvement in wetting is due to the creation of a reaction product at the interface while the second states that interface adsorption of the active element(s) alone is responsible for the improvement in wetting. The goal of this work is to identify the mechanism by which Ti (as an active element) influences the solid-solid interface between Au and α-Al2O3 .
Model samples were prepared by dewetting Au-Ti-Au thin films on (0001) α -Al2O3 single crystal substrates under a controlled atmosphere. The as-deposited Au films contained Ti at concentration levels below the solubility limit. The preferred orientation of the films and equilibrated particles was characterized using X-ray diffraction. Conventional and aberration corrected electron microscopy was used to characterize the particle shape and interface structure. Ti was found to decrease the gold-sapphire interface energy by forming a partially ordered ~1nm thick adsorbate at the interface, in addition to forming a thinner adsorbate layer on the surface of sapphire, indicating that Gibbsian segregation plays a key role in the mechanism by which active elements improve metal-oxide wetting .