HR: 17:15h
AN: MR24A-06    [Abstracts]
TI: Material Composite Behavior Under High-Pressure
AU: * Conil, N
EM: nconil@ess.ucla.edu
AF: UCLA Earth and Space Sciences Department, 4839 Geology Building 595 Charles E. Young Drive East, Los Angeles, CA 90095-1567 United States
AU: Kavner, A
EM: akavner@ess.ucla.edu
AF: UCLA Earth and Space Sciences Department, 4839 Geology Building 595 Charles E. Young Drive East, Los Angeles, CA 90095-1567 United States
AB: In situ x-ray diffraction techniques under relevant pressure and temperature conditions provide unique information about phase stability, elasticity and deformation behavior of Earth materials. Often samples consist of a calibrated standard intermixed with the material of interest. Accurate measurements of equation of state are based on two assumptions: that the equation of state of the calibrant is known precisely, and that the pressures of these two materials are the same. However, except under strict conditions of hydrostaticity, pressures are not necessary equal. To provide a detailed examination of the pressure relationship in the diamond anvil cell sample chamber, we analyzed two standard materials mixed together in a controlled geometry. Our samples consisted of unidirectional Al$_{2}$O$_{3}$ ceramic fibers ($\sim$ 1$\mu$m diameter) distributed in an Al metal matrix. This was ideal because both materials are existing high-pressure standards and the oxide/metal mixture is similar to many experiments. We conducted room temperature radial x-ray diffraction experiments using a diamond anvil cell at the X17C beamline at National Synchrotron Light Source. We studied two different fiber orientations with respect to the diamond anvil cell compression axis: one with fibers oriented vertically and the second, horizontally. In each case we measured the d-spacing of lattice planes as a function of rotation angle between principle stress axes and diffraction geometry. From these data, we calculated pressure and supported differential stress of both Al and Al2O3. We found that geometry plays an important role in determining the relative pressure and strength behavior of the two materials. At comparable pressures, in the vertical fibers case, P$_{Al}$ $\sim$ 8.7 GPa, P$_{Al2O3}$ $\sim$ 10.2 GPa and in the horizontal fibers case, P$_{Al}$ $\sim$ 9.6 GPa when P$_{Al2O3}$ $\sim$ 10.2 GPa. Thus, when the fibers are oriented vertically, aluminum pressure is always smaller than alumina pressure; whereas in the horizontal case; fibers and matrix pressures are almost the same (not more than 0.6 GPa in difference in our experiments). In addition, we present finite element modeling of behavior of composite materials in the diamond cell sample chamber that are in excellent agreement with experiments results. With this study we show that the geometry of samples in the diamond cell must be understood in order to properly interpret measurements. Our ultimate goal is to use this information to design samples that are optimized for better measurements of rheological behavior of Earth interior materials.
DE: 3902 Creep and deformation
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting