TITLE

Shock temperatures in calcite (CaCO[sub 3]): Implication for shock induced decomposition

AUTHOR(S)
Gupta, Satish C.; Love, Stanley G.; Ahrens, Thomas J.
PUB. DATE
April 2000
SOURCE
AIP Conference Proceedings;2000, Vol. 505 Issue 1, p1263
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The temperatures induced in crystalline calcite upon planar shock compression (95-160 GPa) are reported from two-stage light gas-gun experiments. The temperatures are obtained fitting 6-channel optical pyrometer radiances in the 450 to 900 nm range, to a Planck radiation law temperature varied from 3300 to 5400 K. Calculations demonstrate that the temperatures are some 400 to 1350 K lower than if either shock-induced melting and/or disproportionation of calcite behind the shock front was not occurring. Here calcite is modeled as disproportionating into a molecular liquid, or a solid CaO plus CO[SUP2] gas. For temperature calculations, specific heat at constant volume for one mole of CO[SUP2] is taken to be 6.7R as compared to 9R in the solid state; whereas calcite and CaO have their solid state values (15R and 6R). Calculations also suggest that the onset of decomposition in calcite to CaO and CO[SUP2] during loading occurs at ~ 75±10GPa, along the Hugoniot whereas decomposition begins upon unloading from 18 GPa. The 18 GPa value is based on comparison of VISAR measurements of particle velocity profiles induced upon isentropic expansion with one-dimensional numerical simulation.
ACCESSION #
5985578

 

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