Title: Graphite to diamond transformation under shock compression: Role of orientational order

Abstract

To gain insight into the role of orientational order on the shock-induced graphite to diamond phase transformation, three pyrolytic graphite types having different orientational orders were shock-compressed along the average c-axis to peak stresses between 35 and 69 GPa. The materials studied were ZYB-grade highly oriented pyrolytic graphite (HOPG), ZYH-grade HOPG, and as-deposited pyrolytic graphite (PG) having mosaic spreads of 0.8° ± 0.2°, 3.5° ± 1.5°, and ~45°, respectively. Wave profiles, obtained using laser interferometry, show a multiple-wave structure with a distinct, rapid (<10 ns) rise to the high-pressure phase for each graphite type. Multiple-wave profiles, first observed in this study for the less ordered ZYH-grade HOPG and PG samples, show that somewhat poorly oriented pyrolytic graphites also undergo a well-defined phase transformation. Previously, rapid transformation was reported for ZYB-grade but not ZYH-grade HOPG. The measured wave profiles for both HOPG grades are very similar and both grades show a ~22 GPa transformation stress. In contrast, the PG wave profiles are quite different and show a ~46 GPa transformation stress. The continuum results (stress-density states) presented here cannot distinguish between the different high-pressure phases [hexagonal diamond (HD) or cubic diamond] reported in recent x-ray studies. Because ZYB-grade HOPG was recentlymore » shown to transform to HD and due to the similar peak states for both HOPG grades, it seems likely that ZYH-grade also transforms into HD. In conclusion, the very different shock responses of PG and HOPG suggest different transformation mechanisms for PG and HOPG, but the high-pressure PG phase remains unclear in the present work.« less

Authors:

Volz, Travis J.  ^[1];

• Search DOE PAGES for author "Volz, Travis J."
• Search DOE PAGES for ORCID "0000-0001-8224-9368"

Gupta, Y. M.  ^[1]

• Search DOE PAGES for author "Gupta, Y. M."
• Search DOE PAGES for ORCID "0000-0002-2669-3015"

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+ Show Author Affiliations

1. Washington State Univ., Pullman, WA (United States). Inst. for Shock Physics and Dept. of Physics and Astronomy

Publication Date:

Tue Jun 25 00:00:00 EDT 2019

Research Org.:

Washington State Univ., Pullman, WA (United States). Inst. for Shock Physics

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP)

OSTI Identifier:

1545792

Alternate Identifier(s):

OSTI ID: 1529172

Grant/Contract Number:  

NA0002007

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Applied Physics

Additional Journal Information:

Journal Volume: 125; Journal Issue: 24; Journal ID: ISSN 0021-8979

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 58 GEOSCIENCES