[BNC-all] REMINDER: Seminar: F.D. Fischer, Institute of Mechanics, Montanuniversität Leoben, Austria, 11/15/06, ME 256, @ 3:30 PM (On the Role of Surface Energy and Surface Stress in Phase-Transforming Nanoparticles)

[Annie Cheever]

DESIGN AREA SEMINAR
November 15, 2006
3:30 pm                ME 256

F.D. Fischer
Institute of Mechanics, Montanuniversität Leoben,
Franz-Josef-Straße 18, A-8700 Leoben, Austria

"On the Role of Surface Energy and Surface Stress in
  Phase-Transforming Nanoparticles"

Abstract

The role of surface energy and surface stresses 
has been a topic in thermodynamics and physics 
since the seminal work by Gibbs. Since both 
quantities take the same values for liquids this 
may have given rise to misconceptions in the 
community in the case of solids. Terms such as 
surface tension have been applied with a double 
meaning as a surface stress state or surface 
energy. These considerations are of special 
importance for phase transforming nanoparticles 
(precipitates, transforming or 
melting/solidifying single particles). A review 
on the relevant literature is presented showing 
that the findings from continuum mechanics, esp. 
the concept of configurational forces (stresses), 
are often either not known or not accepted. 
Therefore, the progress report gives a rather 
detailed introduction into the continuum 
mechanics and thermodynamics of a moving surface. 
The relevant literature is referenced and the 
main findings are reported. Then the terms 
"surface energy", "surface tension" and "surface 
stress" and their relations are discussed. A 
global transformation condition for a sudden 
phase-transforming nanoparticle is explained. The 
concept of configurational forces is applied to 
derive a local transformation condition in a 
material point at the phase interface. In this 
case the transformation process is controlled by 
a moving phase interface. Four different cases 
for nanoparticles (growing precipitate, growing 
solid nucleus in liquid, melting particle, 
solidifying particle) are studied in detail. It 
can be shown that the surface energy and the 
surface stress contribute to the thermodynamic 
force in different ways. The role of both terms 
is quantified in detail and compared with the 
case of a sudden transformation of the 
nanoparticle.

Brief Bio

Dr. Fischer received his PhD at the Technical 
University of Vienna, Austria, in 1965. From 1965 
to 1983 he held various positions in industry. He 
was appointed as a Lecturer in Technical 
Mathematics in 1976 and Lecturer in Technical 
Mechanics in 1981 both at the Technical 
University of Vienna. Since 1983 he has been 
Professor of Mechanics at the Montanuniversität 
Leoben, Austria. He is a Senior Fellow of the 
Christian-Doppler-Forschungsgesellschaft Vienna, 
Austria, a Guest Professor at the Erich Schmid 
Institute of the Austrian Academy of Sciences 
(2002-05) and recently received the Erwin 
Schrödinger Prize of the Austrian Academy of 
Sciences (2005). He is Head of the Christian 
Doppler Laboratory of Micromechanics of 
Materials. He is Author and co-author of more 
than 450 scientific publications in International 
Journals and Conference Proceedings. His current 
research interests include Multicomponent 
diffusion in multiphase systems; non-equilibrium 
thermodynamics; Transformation Induced 
Plasticity; the deformation behaviour of Ti-Al 
Intermetallics; Constitutive laws for 
phase-transforming materials; Damping control of 
structures by means of shape memory alloy 
devices; Fully three-dimensional modelling of 
stable ductile crack growth in heterogeneous 
materials; Straightening of rails - residual 
stresses and optimal strategy; Microstructure of 
the running surface of rails.


--

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Annie Cheever, Area Secretary                      
School of Electrical and Computer Engineering 
	                                                                 
 
acheever at purdue.edu
			  
Purdue University
Birck Nanotechnology Center, Room 2027
1205 West State Street
West Lafayette, IN  47907-2057

Phone: 765-496-8327     Fax: 765-496-6443     http://www.nano.purdue.edu/  
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