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   COLLOQUIUM OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS        
                   School of Computational Sciences	
                           (CSI 898-Sec 001) 
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     Surface and Interfacial Energy Effects in Nanocrystalline 
          Materials: Consequences for Materials Processing 
                         and Properties

                        Merrilea J. Mayo
            Dept. Materials Science & Engineering, The 
         Pennsylvania STate University, University Park, PA

Grain boundary and surface energies in solid materials are often not 
large-- on the order of 1 J/m2 However, in a 10 nm grain or particle, the
boundary tension results in an internal compressive stress that can be on
the order of 200 MPa. These large pressures increase the free energy of
the system, thereby skewing the thermodynamic equilibria that depend on
free energy. This presentation links the thermodynamic free energy
changes, derived from fundamental relations, to macroscopic phenomena such
as increased solubility for nanoparticles in suspension and shifts in
phase stability towards denser phases. The practical consequences of the
skewed thermodynamics are also presented, using nanocrystalline zirconia
as an example system: ceramic nanoparticles that dissolve in water,
unexpected phases obtained on synthesis, and factors of 5 change in
fracture toughness.

                         Monday , October 22, 2001
                                  4:30 pm
                        Room 206, Science & Tech. I

Refreshments will be served at 4:15 PM.
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Find the schedule at http://www.csi.gmu.edu/lcdm/seminar/schedule.html