PhD thesis defense of Shova Neupane
Jul 05, 2019 - 14.00 uur
Agoralaan Gebouw D
Lokaal auditorium H5
Mevrouw Shova NEUPANE
Shova Neupane invites you to the public defense of her doctoral thesis entitled:
"Well-Controlled Organic Monolayers as Model Inhibitors for Dealloying Corrosion of Noble Metal Alloys".
Promoter is Prof. Dr. Frank Uwe Renner.
In my PhD, I have achieved a better understanding at a molecular level of fundamental processes in corrosion initiation and development in the presence of well-controlled organic surfactant inhibitors. Corrosion naturally degrades materials costing annually 3% of the world’s GDP. Many researchers have been devoted to finding possible organic inhibitors to protect metallic surfaces, also because up to 40% of the cost and material’s life could be saved by a proper knowledge of corrosion protection and applied inhibitors. Selected organic molecules such as alkanethiols protect the surface but they finally also create local corrosion, presumingly around molecular defect areas. If it occurs, localized corrosion is more dangerous than homogeneous corrosion and the mechanism behind the initial progress still remains largely unexplored. In this regard, I have both prepared complex alkanethiol self-assembled monolayers as model systems and used a novel mode of force spectroscopy to unravel the molecular processes. The inhibitor layers where prepared on ultraflat gold as well as on Cu3Au alloys by multiple microcontact printing (μCP) and solution immersion steps, finally creating spatially well-controlled monolayers. The Cu3Au samples clearly exemplified the interplay between the nanoscale surface morphology and the effect of the well-controlled complex alkanethiol films on local corrosion initiation. Moreover, to study the layer stability mercapto-based imidazole molecules, widely used for copper corrosion protection, were exposed on pure copper surfaces by solution immersion and characterized by force spectroscopy AFM and XPS. These experiments provide unprecedented information on the foundations of corrosion efficiency. The achievements of this thesis can be taken as a reference example to study corrosion processes at an atomic and molecular level. The used protocol will help to explore a novel approach to spatially control nanoporosity formation and help and help to enable the design of functional nanoporous surfaces for various alloy surfaces.