Figure 1. Phase transition of MG nanorods under in-situ TEM.

(a) TEM image of MG nanorods pressed into a nanomold with 55-nm-diameter holes. They are drop casts on a thin ceramic film, which gets heated inside TEM. (b) Schematics for the morphological change of MG nanorods at different stages of in-situ heating. As-pressed nanorods exhibit uniform TEM image contrast (first panel). As temperature increases above crystallization temperature, T_c, crystalline grains start to grow in MG nanorods (dark brown in the second panel). The grains are identified by TEM imaging or electron diffraction. As temperature increases above the melting temperature, T_m, the crystallized nanorods turn to liquid phase (third panel). (c) TEM characterizations of a nanorod under in-situ heating. At 30 °C, the nanorod is amorphous, confirmed by the uniform TEM image contrast (top left: BF image, bottom left: DF image) and a diffusive ring pattern in SAED (right panel). Above T_c at 350 °C the nanorod is largely crystallized, reflected in contrast changes in the TEM images. The crystalline phase appears dark for BF (top left) and bright for DF (bottom left) TEM images, respectively. The corresponding SAED displays diffraction spots, indicating the presence of crystalline grains (right panel). At 700 °C, which is above T_m, uniform TEM image contrast and diffusive SAED ring similar to those at 30 °C are observed to indicate that the nanorod is back to disordered state. As heating progresses with longer time, the nanorod becomes significantly deformed. At 900 °C, the nanorod becomes greatly shortened and balled-up.