UC Santa Barbara
Role of Electrostatic Forces on Non-Equilibrium Processes at Confined Inorganic Solid-Liquid-Solid Interfaces
- Author(s): Dobbs, Howard Andrew
- Advisor(s): Israelachvili, Jacob N
- Chmelka, Bradley F
- et al.
Non-equilibrium processes at confined solid-liquid-solid interfaces are prevalent in a wide range of naturally occurring and technologically relevant phenomena such as corrosion, molecular network formation, dissolution and restructuring. Nevertheless, the complex intermolecular interactions involved in the development of macroscopic properties inhibits a fundamental understanding of the evolution of the interface. This is largely due to the difficulties associated with characterizing the role of surface and intermolecular interactions on macroscopic changes within the solid-liquid-solid interface as it evolves over time. In this dissertation, a combination of the surface forces apparatus (SFA), nuclear magnetic resonance (NMR) spectroscopy, and standard materials characterization techniques are used to characterize the intermolecular forces present in confined solid-liquid-solid interfaces and the resultant molecular and macroscopic changes. A new method for producing ultra-smooth (< 3 nm) composite surfaces for the SFA and other optical/interferometric techniques is presented which overcomes the limitations of traditional mica interferometry surfaces while broadening the functionality to achieve characterization of surface and interfacial phenomena in previously unattainable systems. Using this unique combination of characterization methods and tools, the molecular-level measurements establish the influence of electrostatic forces on dissolution-based processes at confined, asymmetric solid-liquid solid interfaces. The results demonstrate that dissolution at confined solid-liquid-solid interfaces can be dramatically enhanced through the manipulation of local electrostatic forces (i.e., electrochemically enhanced dissolution) which offers a new avenue for manipulating dissolution processes in many technological applications such as chemical mechanical polishing and electrochemical corrosion. Additionally, molecular network formation processes initialize through the dissolution and subsequent reaction of surface species which are heavily influenced by surface interactions which direct local ion behavior. Measurement of the molecular structure and surface interactions indicate that only a small portion (<5%) of the material is involved in the network formation process. These results demonstrate the significant impact that initial dissolution processes have on the macroscopic properties of the network, highlighting the importance of the role of molecular-level interactions in the development of macroscopic properties. The methods, analyses, and resulting insights in characterizing the influence of molecular interactions on macroscopic changes are expected to be broadly relevant for non-equilibrium processes at confined solid-liquid-solid interfaces and help establish critical parameters to directly influence the evolution of macroscopic properties at the interface.