Structure and Phase Transition
of the Perfluoroalkane Monolayers
Adsorbed on Graphite
X-ray diffraction and heat capacity measurements have been performed for
the monolayers of perfluoroalkanes
n-CnF2n+2
(n = 6 ~ 16, except for
n = 11) adsorbed on graphite to investigate
the structure and phase behavior. The monolayer of
n-C7F16, for instance,
exhibits 2D solid-solid phase transitions at 131.4 K and 134.3 K
below the melting point of 147.9 K. The monolayers of
n-C8F18,
n-C10F22, and
n-C15F32
also showed the 2D solid-solid phase transition.
(by K. Shimada & A. Inaba)
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Fig. 1.
X-ray diffraction patterns obtained from the sub-monolayer of
n-C7F16
adsorbed on graphite, showing that there is
a 2D solid-solid phase transition between 130 K and 135 K and
a 2D melting between 145 K and 150 K.
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Fig. 2.
2D structure of the monolayer of
n-C7F16 (schematic).
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Fig. 3.
Molar heat capacity of the sub-monolayer of
n-C7F16
adsorbed on graphite. The monolayer exhibits 2D solid-solid transitions
at 131.4 K and 134.3 K and the 2D melting at 147.9 K.
The enthalpies and entropies are given in the figure.
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