Mineral-Water Interactions: Fluid Cell Applications of Scanning Force Microscopy
Published:January 01, 1994
Patricia M. Dove, John A. Chermak, 1994. "Mineral-Water Interactions: Fluid Cell Applications of Scanning Force Microscopy", Scanning Probe Microscopy of Clay Minerals, Kathryn L. Nagy, Alex E. Blum
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Mineral-water interactions are of fundamental importance in controlling the behavior of many natural and engineered earth systems. The processes of weathering and soil development, secondary precipitation and dissolution associated with diagenesis, oil field reservoir behavior, swelling properties of clay liners, and sorption of organic and inorganic contaminants are each influenced by mineral chemistry and physical properties. Until recently, investigations of processes occurring at mineral-water interfaces have necessarily relied upon experimental studies which measured changes in bulk solution chemical composition and/or made comparisons of initial mineral reactants with final reaction products. These methods give our current understanding of mineral solution interactions and behavior while also showing the tremendous complexity and heterogeneity of reacting mineral surfaces. Even from this knowledge base, our understanding of reaction processes continues to be severely limited at every scale from the time-dependent dynamics of macroscopic growth processes to the detailed kinetics and mechanisms of mineral-water reactions at the molecular level. With the recent invention of scanning force microscopy (SFM) and Fluid Cell attachments, it is now possible to span length scales from topographic to molecular and directly observe many different kinds of interfacial processes as they occur in aqueous solutions.
The purpose of this chapter is to introduce the use of the Fluid Cell in SFM as a promising technique that complements traditional surface analysis and bulk geochemical methods in studies of mineral-water interactions. Our focus on the Fluid Cell necessarily limits us from considering other scanning probe techniques such as tapping mode, non-contact mode, magnetic or
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Scanning Probe Microscopy of Clay Minerals
A set of surface-sensitive analytical techniques, collectively called scanning probe microscopy (SPM), has been developed and applied to a wide variety of materials. With SPM one can image nearly any surface in vacuum, in air, or in solution, and often can actually observe surfaces during reaction. Scanning tunneling microscopy (STM) and scanning force microscopy (SFM) have been used successfully in the geosciences to characterize mineral surface structure and topography, surface reactivity, and the rates and mechanisms of mineral-water reactions. SPM techniques are most easily applied to materials with nearly flat surfaces, and minerals with good cleavage, particularly clays, which are excellent prospects for investigation. However, there have been relatively few applications of SPM to geologic materials, particularly in comparison to applications in physics, chemistry, material science, or even biological sciences. The purpose of this volume is to introduce the theory and operation of SPM to clay mineralogists, summarize previous work using STM and SFM in mineralogy, and outline the advantages and limitations of SPM for future research applications.