Students and Their Projects
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Students and Their Projects
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Strength of crystal structure based upon plane orientation for MgO My proposed project consists of work done at Brookhaven National Lab in the National Synchrotron Light Source. I will be looking at how Magnesium Oxide reacts under extreme pressure and temperature using a SAM85 press, and observing its diffraction pattern after sending x rays through the sample. The cell that will hold the sample will contain two crystals of MgO stacked on top of each other, each crystal with a different orientation. The cell will be put into a D-dia, where it will be placed under pressure and temperature, with an exceeding amount of downward pressure placed on the cell by the press. We will continue with this process until the strength of the crystal, determined by the orientation of each, is overwhelmed and the sample undergoes plastic deformation. |
| How much pyroxene dissolves into garnet at the 410 Km Discontinuity. At depths near the Transition zone in the earths upper mantle the two most common minerals are believed to be both Olivine and Pyroxene. In recent experiments using high pressure and temperature research to simulate conditions similar to that of the earth’s mantle, we have not yet been able to agree with seismic evaluations of the earth’s Interior. Seismic data shows a much thinner gap between alpha-Olivine and the transformation to its beta-Olivine polymorph then current high-pressure research. At pressures ranging between 10-15 Gpa the Mg-poor Majorite garnet phase becomes more abundant. A possible solution to this inconsistency between the seismic data and the high-pressure research is the dissolving of pyroxene into “iron hungry garnets”. If a good deal of pyroxene dissolves into the garnet, accompanied by the transfer of iron from olivine and its polymorphs into the garnet phase, this will result in making a magnesium rich Olivine. If enough Iron is taken from the olivine this could possible help explain the smaller gap observed with the seismic data at the discontinuity. |
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Links to related information: |
| 2H NMR spectroscopy of the “10Å phase” The
research consists of synthesis of 10Å phase from talc and water
under high- pressure, but relatively low temperature conditions (ca.
6.5 GPa, 650°C). During synthesis the water becomes incorporated
with the talc structure and increases the interlayer spacing from 7Å
to 10Å. This incorporation of water into the talc structure is
important because it forms a thermodynamically stable phase (10Å
phase) that is capable of transporting water from subducted oceanic
lithosphere into the deep mantle. In order to understand how the water
is incorporated into the 10Å phase 100% D 2O will be used in combination
with isotopically normal talc. This allows the NMR spectroscopy of 2H
to pick up a signal from the D 2O incorporated into the structure and
determine how the water is interacting with the talc structure. |
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Constraints on the Stability of Olivine near the 410-km Seismic Discontinuity There exists a seismic discontinuity about 410 km beneath the surface of the Earth, at which the velocity of seismic waves sharply increases, indicating a sudden change in the physical properties of the material at this depth. The widely accepted cause for this change is the phase transformation of olivine to one of its high-pressure polymorphs, wadsleyite. However, the percentage of olivine in the upper mantle deduced from the velocity jump at the discontinuity differs significantly from that in a “pyrolite” mantle. Using experimental data, it is found that the pyrolite mantle should be composed of about 60 percent olivine, but seismic data indicates only about 30-40 percent olivine. Furthermore, seismic data indicates that the distance over which the olivine phase transformation occurs is much smaller than the experimentally derived value. Thorough understanding of the seismic discontinuities in the mantle is essential in constraining the chemical composition of the Earth. I will attempt to tackle the problems by theoretically and experimentally examining the possible reactions in which olivine may be partially consumed near 410-km discontinuity, therefore reducing the magnitude of the velocity jump. |
SYNTHESIS OF NOVEL SCANDIUM PHOSPHATE ZEOTYPE TOPOLOGIES I am working with Prof. Ivor Bull to synthesize and characterize scandium phosphate microporous materials. The classical definition of a zeolite is a crystalline, porous aluminosilicate material with tetrahedral connectivity. This definition has been expanded in recent years with the introduction of other elements into the framework over aluminum and silicon know as zeotypes. The realization that most of the elements in the Periodic Table can be incorporated has stimulated the preparation of many new materials containing both tetrahedral and octahedral connectivity. The use of metal phosphates such as gallium and scandium phosphates shows the possibility of producing a wider variety of microporous materials. These new materials show promise in increasing the diversity of topologies thus giving a greater range in applications such as shape selective catalysis, molecular sieving, and ion exchange. Previous reactions with scandium phosphates were performed under acid pH’s with minimal effectiveness. Our goal in synthesis is to vary the pH to alkaline concentrations and also to vary the temperature at which synthesis is conducted. We will also be experimenting with longer molecular- chain templates to facilitate larger pore sizes. From the various synthesis reactions, we hope to produce crystals to be analyzed by single crystal X-ray diffraction to map the material’s structure. This analysis will help determine the synthesized material’s effectiveness to perform as a shape selective catalyst. |
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Earthquakes’ Distribution and Analysis Scientists need a variety of ways to distribute information about earthquakes rather than merely using numbers and graphs. Under the supervision of my mentor, Professor Jiuhua Chen, I will explore a method to visualize data using computer technology. By visualizing these data the distribution of earthquakes becomes clear at a glance. I will write a program in JAVA to plot earthquake distribution over the surface of the Earth and along specific slabs at typical subduction zones where earthquakes occur frequently. After accurately plotting earthquakes in a three dimensional space and projecting them onto several two dimensional planes, we will be able to predict the shape of the slab, the direction it is subducting and the places earthquakes occur on that slab. With this program, users are able to change earthquake variables in order to observe the patterns in which earthquakes occur. I wish this program would also be helpful to determine deep earthquakes’ mechanism. |
Modified October 2, 2003 |
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Mineral Physics Institute
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