In situ x-ray investigations of staging and sequencing potassium-graphite intercalation compounds
Misenheimer, Mark Eugene
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https://hdl.handle.net/2142/25293
Description
Title
In situ x-ray investigations of staging and sequencing potassium-graphite intercalation compounds
Author(s)
Misenheimer, Mark Eugene
Issue Date
1985
Doctoral Committee Chair(s)
Zabel, Hartmut
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
in situ x-ray investigations
staging
sequencing
potassium-graphite intercalation compounds
Language
en
Abstract
Experimental investigations, us i n9 x-ray diffraction techniques, have been made into the phenomenon of staging in graphite intercalation compounds. These studies have been performed in situ by means of a two-zone, high-temperature, x-ray furnace. The transition from stage 1 to stage 2 is found to be a two-phase process which does not require intermediate steps. For stage n, n > 2, stage mixing is shown to occur in thermodynamic equilibrium. The amount and relative concentration of admixed stages is seen to be a continuous function of the thermodynamic parameters. Hm~ever, the transition between stage n an~ stage n+l still exhibits a discontinuity which can be characterized as a gap in the allowed concentrations for stage admixing. The size of this gap decreases with increasing stage, i.e., the trans i ti on becomes more continuous.
Various proposed theories for staging are discussed. It is concluded that the intercalate-intercalate screened coulomb interaction is the stabilizing force for staging. Stage mixing is seen to be a direct consequence of finite domain size and entropy. It is unclear whether the discontinuous nature of the stage transitions is a true miscibility gap resulting from a first-order transition or whether it is an apparent miscibility gap resulting from the particular form of a predicted
second-order transition for staging transitions.
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