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High-pressure phase transition in silicon carbide under shock loading using ultrafast x-ray diffraction

Urheber*innen

Tracy,  Sally June
External Organizations;

Smith,  Ray F.
External Organizations;

Wicks,  June K.
External Organizations;

Fratanduono,  Dayne E.
External Organizations;

Gleason,  Arianna E.
External Organizations;

Bolme,  Cynthia
External Organizations;

/persons/resource/speziale

Speziale,  S.
4.3 Chemistry and Physics of Earth Materials, 4.0 Geomaterials, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Appel,  Karen
External Organizations;

Prakapenka,  Vitali B.
External Organizations;

Fernandez Panella,  Amalia
External Organizations;

Lee ,  Hae Ja
External Organizations;

MacKinnon,  Andy
External Organizations;

Eggert,  Jon
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Duffy,  Thomas S.
External Organizations;

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Zitation

Tracy, S. J., Smith, R. F., Wicks, J. K., Fratanduono, D. E., Gleason, A. E., Bolme, C., Speziale, S., Appel, K., Prakapenka, V. B., Fernandez Panella, A., Lee, H. J., MacKinnon, A., Eggert, J., Duffy, T. S. (2017): High-pressure phase transition in silicon carbide under shock loading using ultrafast x-ray diffraction - Abstracts, AGU 2017 Fall Meeting (New Orleans, USA 2017).


Zitierlink: https://gfzpublic.gfz-potsdam.de/pubman/item/item_3305900
Zusammenfassung
The behavior of silicon carbide (SiC) under shock loading was investigated through a series of time-resolved pump-probe x-ray diffraction (XRD) measurements. SiC is found at impact sites and has been put forward as a possible constituent in the proposed class of extra-solar planets known as carbon planets. Previous studies have used wave profile measurements to identify a phase transition under shock loading near 1 Mbar, but crystal structure information was not obtained. We have carried out an in situ XRD study of shock-compressed SiC using the Matter in Extreme Conditions instrument of the Linac Coherent Light Source. The femtosecond time resolution of the x-ray free electron laser allows for the determination of time-dependent atomic arrangements during shock loading and release. Two high-powered lasers were used to generate ablation-driven compression waves in the samples. Time scans were performed using the same drive conditions and nominally identical targets. For each shot in a scan, XRD data was collected at a different probe time after the shock had entered the SiC. Probe times extended up to 40 ns after release. Scans were carried out for peak pressures of 120 and 185 GPa. Our results demonstrate that SiC transforms directly from the ambient tetrahedrally-coordinated phase to the octahedral B1 structure on the nanosecond timescale of laser-drive experiments and reverts to the tetrahedrally coordinated ambient phase within nanoseconds of release. The data collected at 120 GPa exhibit diffraction peaks from both compressed ambient phase and transformed B1 phase, while the data at 185 GPa show a complete transformation to the B1 phase. Densities determined from XRD peaks are in agreement with an extrapolation of previous continuum data as well as theoretical predictions. Additionally, a high degree of texture was retained in both the high-pressure phase as well as on back transformation. Two-dimensional fits to the XRD data reveal details of the orientational relationships between the low- and high-pressure phases that can be interpreted to provide information about transformation pathways between tetrahedral and octahedral coordination structures.