A5055450039- Radioactive element chemistry and processing
- Nuclear Materials and Properties
- Nuclear materials and radiation effects
- Metal Extraction and Bioleaching
- Minerals Flotation and Separation Techniques
- Calcium Carbonate Crystallization and Inhibition
- Iron oxide chemistry and applications
- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- Electrochemical Analysis and Applications
- Advanced Condensed Matter Physics
- Nuclear reactor physics and engineering
- Hydrocarbon exploration and reservoir analysis
- Transition Metal Oxide Nanomaterials
- Mine drainage and remediation techniques
- Crystallization and Solubility Studies
- Paleontology and Stratigraphy of Fossils
- Electron and X-Ray Spectroscopy Techniques
- Chemical and Physical Properties in Aqueous Solutions
- Gas Sensing Nanomaterials and Sensors
- Radioactive contamination and transfer
- Solid-state spectroscopy and crystallography
- Extraction and Separation Processes
- Enhanced Oil Recovery Techniques
- Bone Tissue Engineering Materials
University of Michigan
2015-2024
Ann Arbor Center for Independent Living
2014-2021
Environmental Earth Sciences
2005-2013
Steacie Institute for Molecular Sciences
2010
National Research Council Canada
2010
The University of Sydney
2009
Institute of Semiconductor Physics
2007-2008
Florida International University
2007
University of Chicago
2007
Sandia National Laboratories
2006
Nucleation in the natural world often occurs presence of organic interfaces. In mineralized tissues, a range macromolecular matrices are found contact with inorganic phases and believed to direct mineral formation. geochemical settings, surfaces, which covered or biological films, surround volume within nucleation occurs. classical picture nucleation, such interfaces is expected have profound effect on rates, simply because they can reduce interfacial free energy, controls height...
Crystals grow in supersaturated solutions. A mysterious counterexample is dolomite CaMg(CO3)2, a geologically abundant sedimentary mineral that does not readily at ambient conditions, even under highly Using atomistic simulations, we show initially precipitates cation-disordered surface, where high surface strains inhibit further crystal growth. However, mild undersaturation will preferentially dissolve these disordered regions, enabling increased order upon reprecipitation. Our simulations...
Tungsten oxide (WO3) thin films have been produced by KrF excimer laser (lambda = 248 nm) ablation of bulk ceramic WO3 targets. The crystal structure, surface morphology, chemical composition, and structural stability the studied in detail. Characterization freshly grown has performed using X-ray diffraction (XRD), atomic force microscopy (AFM), energy-dispersive spectroscopy (EDX), Raman (RS), transmission electron (TEM), selected area (SAED) measurements. results indicate that are nearly...
First-principles calculations and molecular-dynamics simulations are employed in this study to further our understanding of the crystal structure orientational order carbonate ions vaterite, which is least stable polymorph calcium carbonate. The structural details vaterite have been controversial but they prerequisite for investigating processes involving nucleation, growth, stabilization at a molecular level. first-principles calculations, using density functional theory with plane-wave...
Reduction of U(VI) to U(IV) on mineral surfaces is often considered a one-step two-electron process. However, stabilized U(V), with no evidence U(IV), found in recent studies indicates can undergo one-electron reduction U(V) without further progression U(IV). We investigated pathways uranium by reducing electrochemically magnetite electrode at pH 3.4. Cyclic voltammetry confirms the U(V). Formation nanosize precipitates surface potentials and dissolution solids oxidizing are observed situ...
The interaction of gaseous O2, H2O, and their mixtures with clean {100} surfaces pyrite (FeS2) were investigated in ultra-high vacuum using scanning tunneling microscopy spectroscopy (STM-STS), ultraviolet photoelectron (UPS) ab initio calculations. He I UPS spectra O2 exposed show that the density states decreases at top valence band but increases deeper band. These changes indicate oxidative consumption low binding energy electrons occupying dangling bond surface localized on Fe atoms,...
Although significant progress has been made in understanding the behavior of natural nanoparticles Earth's critical zone (i.e., surface and near-surface environment), little is known about nanoparticle stability higher-temperature environments where they are increasingly being found. Here we report first direct observations thermal at near atomic scale, revealing that their dependent on particle size surrounding host mineral. Native Au (mean diameter ∼4 nm) incorporated arsenian pyrite from...
An irreversible structural transformation from the cubic phase to a hexagonal high-pressure was verified in ${\text{Gd}}_{2}{\text{O}}_{3}$ between 7.0 and 15 GPa. The compressibility bond distances of both phases were determined by refinement x-ray diffraction data. is 9.2% denser than at 7 After release pressure, transformed monoclinic structure. pressure-induced transition reversible. Unlike case atmospheric found transform increase temperature high pressures. lattice potential energies...
We report dramatically different behaviors between isostructural Gd2Ti2O7 and Gd2Zr2O7 pyrochlore at pressures up to 44 GPa, in which the substitution of Ti for Zr significantly increases structural stability. Upon release pressure, becomes amorphous. In contrast, high-pressure phase transforms a disordered defect-fluorite structure. First-principle calculations both compositions revealed that response high pressure is controlled by intrinsic energetics defect formation.
Experiments were carried out by reacting H2 gas with N2 hydrate at a temperature of 243 K and pressure 15 MPa. The characterizations the reaction products indicated that multiple molecules can be loaded into both large small cages structure II clathrate hydrates. realization occupancy under moderate conditions not only brings new insights hydrogen clathrates but also refreshes perspective hydrates as storage media.
Clean pyrite {100} surfaces, generated by cleaving in UHV, were investigated using scanning tunneling microscopy and spectroscopy for the purpose of understanding electronic structure at surface. Calculations surface atomic LEED data support a that undergoes very little relaxation can be approximated simple termination bulk along plane cleaved Fe-S bonds. UPS spectra show well defined peak ~1 eV forming top valence band near Calculated densities states crystal suggest this is comprised...
Metastable vaterite crystals were synthesized by increasing the pH and consequently saturation states of Ca2+- CO2-3-containing solutions using an ammonia diffusion method. SEM TEM analyses indicate that grains produced this method are polycrystalline aggregates with a final morphology has sixfold-symmetry. The primary structure develops within hour is almost spherical assemblage nanoparticles (5-10 nm) random orientation, followed formation hexagonal platelets (1-2 μm), which first composed...
Applications of redox processes range over a number scientific fields. This review article summarizes the theory behind calculation potentials in solution for species such as organic compounds, inorganic complexes, actinides, battery materials, and mineral surface-bound-species. Different computational approaches to predict determine electron transitions are discussed along with their respective pros cons prediction potentials. Subsequently, recommendations made certain necessary settings...