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Title: Kinetics of the B1-B2 phase transition in KCl under rapid compression

Kinetics of the B1-B2 phase transition in KCl has been investigated under various compression rates (0.03–13.5 GPa/s) in a dynamic diamond anvil cell using time-resolved x-ray diffraction and fast imaging. Our experimental data show that the volume fraction across the transition generally gives sigmoidal curves as a function of pressure during rapid compression. Based upon classical nucleation and growth theories (Johnson-Mehl-Avrami-Kolmogorov theories), we propose a model that is applicable for studying kinetics for the compression rates studied. The fit of the experimental volume fraction as a function of pressure provides information on effective activation energy and average activation volume at a given compression rate. The resulting parameters are successfully used for interpreting several experimental observables that are compression-rate dependent, such as the transition time, grain size, and over-pressurization. The effective activation energy (Q{sub eff}) is found to decrease linearly with the logarithm of compression rate. When Q{sub eff} is applied to the Arrhenius equation, this relationship can be used to interpret the experimentally observed linear relationship between the logarithm of the transition time and logarithm of the compression rates. The decrease of Q{sub eff} with increasing compression rate results in the decrease of the nucleation rate, which is qualitatively in agreementmore » with the observed change of the grain size with compression rate. The observed over-pressurization is also well explained by the model when an exponential relationship between the average activation volume and the compression rate is assumed.« less
Authors:
; ; ; ; ; ; ;  [1]
  1. HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States)
Publication Date:
OSTI Identifier:
22494966
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 119; Journal Issue: 4; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ACTIVATION ENERGY; ARRHENIUS EQUATION; COMPRESSION; DIAGRAMS; DIAMONDS; EXPERIMENT RESULTS; GRAIN SIZE; KINETICS; NUCLEATION; PHASE TRANSFORMATIONS; POTASSIUM CHLORIDES; PRESSURE DEPENDENCE; PRESSURE RANGE GIGA PA; PRESSURIZATION; TIME RESOLUTION; X-RAY DIFFRACTION