My research often involves powder diffraction methods, including the Rietveld method, a powerful technique that facilitates extraction of a tremendous amount of quantitative information from diffraction patterns of solids. I have clarified the structures of a number of important fine-grained minerals using a combination of X-ray and neutron powder diffraction methods with spectroscopic techniques
Much of my recent work has focused on understanding the structures, properties, and origins of fine-grained minerals, such as clay minerals and natural zeolites, using a multidisciplinary approach. For example, in a recent study of kaolinite origin, I focused on an analysis of the degree of crystalline order present within samples using computer simulation of powder diffraction patterns, showing that kaolinite order varies greatly as a function of particle size (some samples showing the best order in the finest fractions). I later combined these studies with trace-element (REE) analyses as a function of size fraction to gain a more complete picture of kaolinite genesis (and also showing that the trace-element content of natural kaolins is attributable mostly to their trace mineral content). My recent studies of the surface properties of smectites were similar, including diffraction, spectroscopic, and surface chemistry analyses. Although fundamental in nature, these surface property studies are of great importance in understanding many applied aspects of smectite behavior, from their ability to swell osmotically, to uses in landfills, to predicting new uses of surface-modified smectites as organic adsorbents. Other applied mineralogical studies include my work on the behavior of fluorine in brick raw materials (clay minerals), the measurement of trace erionite in natural zeolite products, and a variety of studies on the importance of clay and zeolite minerals in radioactive waste applications. Surface properties, crystallography and geochemistry of clay minerals. Applications of clay and zeolite minerals and interactions with organic pollutants. Rheology of clay suspensions.
