Reversing and non-reversing melting of n-hexatriacontane: In situ optical observation study

The small crystal of n-hexatriacontane was observed by polarizing microscope in the melting transition temperature region. In the region, the area expansion which started from the surface defects appeared. It gradually grew. The area of the small crystal changed reversibly with the temperature modulation. The angle of the axis of optical anisotropy also changed with the temperature modulation but did not change reversibly. After the entire region of the sample was expanded, the area hardly increased though the sample was heated. When the temperature was reached at the upper-end of the melting temperature region, the sample melted immediately.

► The area expansion which started from the surface defects appeared in pre-melting.
► Area of small crystal changed reversibly with temperature modulation in pre-melting.
► The density of defects changed non-reversibly with the area change in pre-melting.
► The small crystal melted after the entire region of the sample was expanded.
► Lattice was assumed to be distorted by growth of lowest energy phase in pre-melting.