According to phase transition theory, a solid crystal will fluctuate between two equilibrium structures near the phase transition point before reaching a stable configuration, and that this region of transition broadens in small crystals. To test this theory, Zheng, Alivisatos and their co-authors zapped copper sulphide nanorods with an electron beam from the TEAM 0.5 microscope then watched for and saw the predicted fluctuations.
"Before the TEAM microscopes, such details of the fluctuations between two solid-state phases in a nanocrystal could not have been observed," says Zheng. "Our results should be of interest to theorists attempting to simulate structural transformations in solids as neither a study on bulk materials nor on the ensemble of nanomaterials has the capability of revealing such specific features of the phase transition pathways."
TEAM stands for Transmission Electron Aberration-corrected Microscope. TEAM 0.5 and its sister instrument TEAM 1.0 are capable of producing images with half angstrom resolution - less than the diameter of a single hydrogen atom. Both microscopes are housed at Berkley Lab in DOE's National Center for Electron Microscopy (NCEM).
The next step for her, Zheng says, will be to address questions concerning the transport of ions with battery material changes at the electrode/electrolyte interface, and structural changes of nanoparticle catalysts.
"Such studies share the same aim of developing microscopic understanding of the structural transformations of materials, especially th
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory