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Matthew L. WhitakerMay 21, 2008Future Directions of High P Research High Pressure Synchrotron and Ultrasonic Interferometry Study of  -FeSi Future Directions.

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Presentation on theme: "Matthew L. WhitakerMay 21, 2008Future Directions of High P Research High Pressure Synchrotron and Ultrasonic Interferometry Study of  -FeSi Future Directions."— Presentation transcript:

1 Matthew L. WhitakerMay 21, 2008Future Directions of High P Research High Pressure Synchrotron and Ultrasonic Interferometry Study of  -FeSi Future Directions of High Pressure Research NSLS User Meeting – May 21, 2008 Matthew L. Whitaker Wei Liu, Qiong Liu, Liping Wang, and Baosheng Li

2 Matthew L. WhitakerMay 21, 2008Future Directions of High P Research The Problem of Planetary Cores No access to deep interiorNo access to deep interior Seismic data indicate light element presenceSeismic data indicate light element presence Must ascertain properties of iron/light-element alloys under extreme conditionsMust ascertain properties of iron/light-element alloys under extreme conditions Local facilities utilizing different techniques allow for detailed study of these materialsLocal facilities utilizing different techniques allow for detailed study of these materials Si strongly suggested to be in planetary cores both isotopically and cosmochemicallySi strongly suggested to be in planetary cores both isotopically and cosmochemically Study  -FeSi using combined synchrotron X- radiation and ultrasonic interferometryStudy  -FeSi using combined synchrotron X- radiation and ultrasonic interferometry

3 Matthew L. WhitakerMay 21, 2008Future Directions of High P Research Ultrasonic & X-Ray Experiment

4 Matthew L. WhitakerMay 21, 2008Future Directions of High P Research Ultrasonic Interferometry Dual Mode TransducerDual Mode Transducer MHz20-70 MHz –60 MHz – P Wave –35 MHz – S Wave Pulse Echo OverlapPulse Echo Overlap

5 Matthew L. WhitakerMay 21, 2008Future Directions of High P Research Experimental Conditions

6 Matthew L. WhitakerMay 21, 2008Future Directions of High P Research Data Collection X-Ray DiffractionX-Ray Diffraction –Monitor sample structure; no phase transition (B20) –Cell refinement gives unit cell volumes/densities –Minimal deviatoric stress X-Radiographic ImagingX-Radiographic Imaging –Sample length in pixels –Recovered sample length gives pixel/mm ratio Ultrasonic InterferometryUltrasonic Interferometry –P and S Wave two-way travel times

7 Matthew L. WhitakerMay 21, 2008Future Directions of High P Research Finite Strain Equations K S /K T = (1 +  T) ≈ 1.03, where the thermal expansion coefficient  (300K) = 4.85 ×10 -5 K -1, the Grüneisen parameter  = 2.33 (Vocadlo et al., 2002)K S /K T = (1 +  T) ≈ 1.03, where the thermal expansion coefficient  (300K) = 4.85 ×10 -5 K -1, the Grüneisen parameter  = 2.33 (Vocadlo et al., 2002)

8 Matthew L. WhitakerMay 21, 2008Future Directions of High P Research Experimental Results

9 Matthew L. WhitakerMay 21, 2008Future Directions of High P Research Experimental Results

10 Matthew L. WhitakerMay 21, 2008Future Directions of High P Research Comparison of Results Comparison of elastic properties of e-FeSi with previous studies Ref.P (GPa)K S0 (GPa)K S0 'K T0 (GPa)K T0 'V 0 (Å 3 )MethodG0G0 G0'G0' A (17)6.0(3) (3) Ultrasonics w/ X-Ray113.1(8)2.7(1) B (8)6.5(3) (3) Ultrasonics w/ X-Ray116.3(4)3.0(1) Sarrao et al *---- Resonant Ultrasonics116*- Knittle & Williams XRD-DAC-- Wood et al (fixed)90.21(2)Neutron-- Guyot et al (fixed)90.39(4)X-Ray-- Lin et al X-Ray-- Vocadlo et al 1999Calculated227 (0K) Calculation-- Caracas & Wentzcovitch 2004Calculated Calculation (LDA)-- Caracas & Wentzcovitch 2004Calculated Calculation (GGA)-- A: This study, cold compression. B: This study, decompression after heating. *Estimates based on graphical data

11 Matthew L. WhitakerMay 21, 2008Future Directions of High P ResearchDiscussion First data available on shear properties of  -FeSiFirst data available on shear properties of  -FeSi Difference between cold compression and decompression after heating caused by porosity collapse during heating at peak pressureDifference between cold compression and decompression after heating caused by porosity collapse during heating at peak pressure Data agree reasonably well with previous experimental results; significantly different from calculationsData agree reasonably well with previous experimental results; significantly different from calculations Higher K’ than previous studiesHigher K’ than previous studies –Most fixed at 4.0 –Did not take shear properties into account To assess feasibility of  -FeSi as possible core constituent, elastic properties at high T must be determinedTo assess feasibility of  -FeSi as possible core constituent, elastic properties at high T must be determined

12 Matthew L. WhitakerMay 21, 2008Future Directions of High P ResearchAcknowledgements Baosheng LiBaosheng Li Wei LiuWei Liu Qiong LiuQiong Liu Liping WangLiping Wang Carey KoledaCarey Koleda Mike VaughanMike Vaughan Bob LiebermannBob Liebermann Ben VitaleBen Vitale Bill HeubschBill Heubsch Mineral Physics InstituteMineral Physics Institute COMPRES Don Weidner John Parise Cathy Tarabrella Lars Ehm Yanbin Wang Sara Huggins


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