Alumina (Al2O3) and silica (SiO2) materials are prevalent in geological environments and complex materials used for device fabrication (for example, chemical-mechanical polishing, CMP), structural materials, and heterogeneous catalysts. In each of these systems, the solid-liquid-solid interface plays a crucial role in determining material properties and interactions in aqueous environments, especially with regards to dissolution. In particular, both the “Pressure Solution” phenomenon (relevant in geologic environments) and CMP demonstrate that the dissolution of alumina and silica materials can be drastically enhanced in aqueous environments; however, the cause of enhancement is still highly debated or unknown. Dissolution enhancement in both of these systems share similar mechanisms – asymmetric, or distinct, materials in close proximity in a saline, aqueous environment. In this work, we study the mechanism of enhanced dissolution of alumina and silica in alkaline environments as affected by the presence of an asymmetric surface. Using the surface forces apparatus (SFA) to characterize the enhanced dissolution in proximity to muscovite mica surfaces, we found that the dissolution is enhanced to varying degrees depending on the relative surface potentials of the asymmetric surfaces. The impact of key parameters of the electrostatic double-layer, such as the Debye (decay) length and surface potentials, were explored to provide insights into the electrochemical enhancement mechanism. Transport processes within the confined interface (lateral contact zones), such as diffusion and shearing-induced convection, are shown to influence the maximum achievable enhanced dissolution rates. Our findings highlight the importance of the asymmetric solid-liquid-solid interface and suggest new methods for a variety of technological applications, including for structural materials and chemical mechanical polishing.

Electrochemically enhanced dissolution of silica and alumina in alkaline environments

255th National Meeting (2018)

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