Phase Transformations in Confined Nanosystems

Shield, Jeffrey E.¹  Belashchenko, Kirill² 

[1]Department of Mechanical & Materials Engineering

[2]Department of Physics & Astronomy

关键词: Phase transformations;    transmission electron microscopy;   

DOI  :  10.2172/1129757
RP-ID  :  Final Report
PID  :  OSTI ID: 1129757
Others  :  Other: DE-FG02-09ER46621

学科分类：材料科学（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

This project discovered that non-equilibrium structures, including chemically ordered structures not observed in bulk systems, form in isolated nanoscale systems. Further, a generalized model was developed that effectively explained the suppression of equilibrium phase transformations. This thermodynamic model considered the free energy decrease associated with the phase transformation was less than the increase in energy associated with the formation of an interphase interface, therefore inhibiting the phase transformation. A critical diameter exists where the system transitions to bulk behavior, and a generalized equation was formulated that successfully predicted this transition in the Fe-Au system. This provided and explains a new route to novel structures not possible in bulk systems. The structural characterization was accomplished using transmission electron microscopy in collaboration with Matthew Kramer of Ames Laboratory. The PI and graduate student visited Ames Laboratory several times a year to conduct the experiments.