Nucleation of a solid phase from an aqueous phase at solid-liquid interfaces is an important process in many fields, such as material synthesis, thin film deposition, nanoparticle formation, and geochemistry. However, over the years, focus has been on thermodynamic parameters governing the nucleation process, yet there has much less work on understanding of kinetic factors despite their controlling roles in nucleation. In this study, we developed a method to quantitatively measure the kinetic factors (i.e., the pre-exponential factor and activation energy) in the nucleation rate equation, J=exp(-Ea/RT)exp(-ΔG*/RT), which have not been available in the past. Calcium carbonate was chosen to be the nucleating phase, and quartz was used as substrates. The relative nucleation rates were measured using in situ grazing incidence small angle X-ray scattering at 11, 25, and 31 oC with a fixed supersaturation of IAP/Ksp=101.65. The absolute nucleation rates were calibrated with AFM images of freshly reacted substrates on which nuclei could be observed distinctly. We obtained the activation energy Ea as 45 ± 7 kJ/mol, and the pre-exponential factor A as 101.0 ± 1.3 mol/m2/s. These parameters are important for numerically modeling nucleation as an explicit step in mineral precipitation to improve our understanding of geomedia alteration under geologic CO2 sequestration conditions.

Experimental quantification of kinetic factors in the nucleation rate equation

253rd National Meeting (2017)

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