In situ transmission electron microscopy observations of sublimation in silver nanoparticles.
In situ heating experiments were performed in a transmission electron microscope (TEM) to monitor the thermal stability of silver nanoparticles. The sublimation kinetics from isothermal experiments on individual nanoparticles was used to assess the actual temperatures of the nanoparticles by considering the localized heating from the electron beam. For isolated nanoparticles, beam heating under normal TEM operating conditions was found to increase the temperature by tens of degrees. For nominally isothermal experiments, the observed sublimation temperatures generally decreased with decreasing particle size, in agreement with the predictions from the Kelvin equation. However, sublimation of smaller nanoparticles was often observed to occur in discrete steps, which led to faceting of the nanoparticles. This discrete behavior differs from that predicted by conventional theory as well as from experimental observations in larger nanoparticles where sublimation was continuous. A hypothesis that explains the mechanism for this size-dependent behavior is proposed.
Materials Science and Engineering Program and ‡Department of Mechanical Engineering, University of Texas at Austin , Austin, Texas 78712, United States.
Michael A
MA
Asoro
Desiderio
D
Kovar
Paulo J
PJ
Ferreira
D003198:Computer Simulation; D006361:Heating; D008422:Materials Testing / Q000379:methods*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D010316:Particle Size; D044367:Phase Transition; D012834:Silver / Q000737:chemistry*; D013499:Surface Properties; D013814:Thermal Conductivity; D013816:Thermodynamics
D012834:Silver