Fig. 2.
Changes in particle size, physicochemical properties, and phase abundances as a function of aging. (A) Average particle size from TEM analysis. Bars indicate standard deviations. (B) Density (Open Diamonds) from pycnometry and specific surface area (Light Shade) from N2-BET as a function of aging. (C) Total Fe (Solid Squares) of solid phase and hydration weight losses by TGA (Shaded). Medium and dark shaded regions indicate weight losses after heating to 1,000 °C and 125 °C, respectively. Note that data for t = 14 h are representative of single-phase hematite. (D) Percent phase abundances of precursor ferrihydrite (fh), ferrimagnetic ferrihydrite (ferrifh), and hematite (hm) from chemometric analysis.