Zeolitic materials with negatively charged frameworks possess high cation-exchange capacity and selectivity towards ions and/or gases. These materials are potentially useful in separation, contaminant removal, and sequestration applications. It is important to understand the structural basis for any selectivity and changes in crystal structure accompanying ion exchange of known as well as new materials. I am working with John Parise and Aaron Celestinan to explore the cation-exchange capacity of a KAlGe GIS. I am exchanging this GIS, in both powder and crystal form, with solutions containing Na+, Rb+, Cs₂+, Sr₂+, Ag+, and Cd₂₊. I am using powder x-ray diffraction to look at the powder patterns of the exchanged samples. I will then look at a single crystal of the exchanged material using a single crystal x-ray diffractometer; with this apparatus, I will determine the change in the unit cell of the KGIS after ion exchange. Next, I will use the X7B beamline at the National Synchrotron Light Source to do an in situ time resolved diffraction study of my samples. In addition to this ion exchange work, I will be trying to synthesize new materials with ion exchange capacity.

High Pressure Liquid Immiscibility in Barberton Basaltic Komatiites

Bob Rapp and I are working on liquid immiscibility in Barberton basaltic komatiites. Komatiites are very old ultramafic rocks which similar in composition to the Earth's mantle. The presence of small, near circular globules of felsic rock similar in compostion to the Earth's crust found within komatiites in South Africa is nature's way of hinting about crustal formation. Liquid immiscibility is the process of differentiating two liquids from the cooling of a magma. One possibility of how the crust formed is through liquid immiscibility and the two liquids separating further into distinct layers by gravity. The felsic rock being less dense would rise to the surface forming the crust. We want to determine at what temperatures and pressures the komatiite exhibits liquid immiscible behavior in an attempt to understand a bit about the formation of the Earth's crust.

I am working with Don Lindsley and Martin Schoonen, testing phases in the ilmenite group for zeta potential and effectiveness as photocatalysts.

Jeremy Koontz

High Pressure Synthesis of Perovskites

Most multiferroic materials, which posses both ferromagnetic or ferroelectric properties, exhibit complex structures that inhibit property analyses on an atomic level. Bismuth manganate, BiMnO₃, however, is a structurally simple multiferroic perovskite, allowing for association of its properties to the atomic structure. BiMnO₃ will be synthesized by applying high pressure and temperature to mixtures of manganese oxide and bismuth oxide or using sol-gel prepared precursors. Powder x-ray diffractometry will be used to analyze phase variations induced by pressure and temperature manipulation. The synthesized material will then be tested for ferromagnetic and ferroelectric properties.

Andrew Schmidt

Synthesis of Hydrous Wadsleyite

I am using the USSA 2000 press here to synthesize hydrous wadsleyite, the beta phase structural polymorph of olivine. The iron content is the same as that of the San Carlos olivine, and samples will be produced with water content varying from 0.5% to 1.5% by mass. The starting materials are a mixture of finely powdered SiO₂, MgO, Fe₂O₃, Fe, and Mg(OH)₂ which provides the water. In the hydrous form, H₂O replaces MgO in the wadsleyite crystal lattice. These materials are compressed to 15.0 GPa and heated to 1473K where wadsleyite is the thermodynamically stable phase. The phases of the recovered sample are determined with X-ray diffraction, and the chemical composition is determined using electron microprobe analysis. These samples can then be used to study the phase relationship between olivine and wadsleyite.

The hydrous form of wadsleyite has important implications in the detail of the 410km seismic discontinuity. In a pyrolite mantle, the seismic discontinuity is due to the phase transformation of olivine to wadsleyite. However, the region in which olivine and wadsleyite coexist is larger than seismic observation, as is the velocity jump. Iron containing, hydrous wadsleyite may help reduce the observed discrepancy. However, the amount of water in the region where both phases coexist is sketchy at best because hydrous olivine saturates with far less water than hydrous wadsleyite.

Nathan Schmidt

The purpose of this project is to examine the rheological properties of MgO periclase at high pressure (approximately 10 GPa) and low temperature (>200 C). It is understood (Mg, Fe)O composes a significant portion of the earth’s lower mantle, making it necessary to examine its properties under similar pressure temperature conditions. In-Situ x-ray diffraction data of periclase is collected using polychromatic x-rays, generated by the superconductor wiggler beam line at the National Synchrotron Light Source (NSLS). Important structural properties, such as stresses and grain size, are derived by analyzing the diffraction peak width at various pressure and temperature. A Transmission Electron Microscope (TEM) is used to investigate the microstructures of the recovered samples, with the intention of interpreting the stress and grain size values deduced from the diffraction data. This experiment is part of a follow-up investigation of a previous experiment where the rheology of periclase was examined at high pressure and temperature. It was found that periclase exhibits unusual high stress values under high pressure and low temperature. Therefore, this second study is conducted to investigate the cause of these high stresses, i.e. crystalline defects, sample hysteresis, changes in grain size, etc.

Hot-pressing and characterization of pyrope (Mg₃A_l2Si₃O₁₂) – garnet

Garnet is an important constituent of the Earth’s mantle. Petrologic studies show that the stability field of garnet expands with increasing Al content. The elastic properties of garnet are important for interpreting seismic models of the elastic wave velocities and densities in the transition zone. This summer, I will be hot-pressing polycrystalline aggregates of pyrope (Mg₃Al₂Si₃O₁₂)- garnet by subjecting pyrope to high pressures and temperatures using a 2000-ton Uniaxial-Split-Sphere Apparatus. After retrieving the sample from the USSA-2000, it will be tested by X-ray diffraction to determine if the specimen is single-phased. Other tests will be performed on the sample to make sure the sample is fine-grained (<5 ?m), exhibits a density close to the theoretical X-ray density, and is free of microcracks and preferred orientation. If the specimen meets these standards, the shear and compressional velocities will be measured by using ultrasonic interferometry. The goal of my summer research is to measure the acoustic velocities for the pyrope-garnet specimen at high pressures and temperatures in conjunction with synchrotron x-radiation.

Roman Timoshkin

Under the supervision of my mentor, Dr. Baoshang Li, I will be studying the models of ultrasonic wave propagation using "Wave 2000," a stand-alone computer software program for computational ultrasonics. Using this software we will be able to perform real-time parallel computations and visualization of ultrasonic pulses in solids, subjected to user-specified acoustic sources. Particularly, I am interested in simulating ultrasonics that resembles experimental assembly for simultaneous high-pressure and high-temperature velocity measurements. I believe many such models of wave propagation are very important in electromagnetics, acoustics, seismology, medical imaging, and many other areas of physical science.

Dean Vetsikas

We will be conducting experiments to produce a model/fit for the equations of state for Iron and Aluminum enriched Silicate Perovskite, (Al, Mg, Fe) Pv. This form of Perovskite is thought to comprise approximately 70% of the Earth's lower mantle. Accurate representations of the quatitative relationship between this form of Perovskite at various pressures and temperatures will yeild a better understanding of how the Earth was formed. We will gain an understanding of the role which Fe plays in this P-V-T dependency/interaction as we have axcess to similar research on Silicate Perovskites where Fe interplay was neglected.