In situ x-ray investigations of staging and sequencing potassium-graphite intercalation compounds

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Misenheimer, Mark Eugene

Contributors dc:contributor

• Zabel, Hartmut

• in situ x-ray investigations
• staging
• sequencing
• potassium-graphite intercalation compounds

Statement dc:rights

• 1985 Mark Eugene Misenheimer

Language dc:language

en

Identifier

864938

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25293