Melting, expansion behavior and electric transport of In-filling in MgO nanotubes.

By using a one-step approach, In-filled MgO nanotubes with diameters of 200-300 nm and lengths of several micrometers are synthesized. A Gatan heating experiment in a transmission electron microscope (TEM) shows that In-filling begins to melt far below the melting point 156.6 degrees C of In and abnormally shrinks upon increasing temperature above 270 degrees C. Massive In-filled MgO nanotubes were pressed into a disk and its resistance starts dramatically decrease upon increasing temperature above -150 degrees C, suggesting a temperature switch with a protective point -150 degrees C. The expansion and I-V characteristics were discussed.