Seminar Schedule – Spring 2015

Tuesday, February 17, 2015
Time: 3:30pm
Place: WRW 102

Compatibility, hysteresis and the direct conversion of heat to electricity

Richard James – University of Minnesota

Big first order phase transformations in solids can be highly reversible, if the lattice parameters are “tuned” to satisfy certain relations that promote the compatibility between phases. We outline the basic theory behind this tuning and give examples of recently discovered alloys. Some of these alloys have thermal hysteresis as low as 0.2 C despite having an 8% transformation strain. The lowered hysteresis correlates with the reversibility of the transformation under repeated cycling. We use this kind of tuning, together with the lattice parameter sensitivity of magnetic properties and the presence of a jump of lattice parameters at the phase transformation, to find some interesting new multiferroic Heusler alloys: briefly, multiferroism by reversible phase transformation. These alloys can be used in diverse ways for the direct conversion of heat to electricity, and provide interesting possible ways to recover the vast amounts of energy stored on earth at small temperat ure difference.

For more information, contact Dr. K. Ravi-Chandar at (512) 471-4213.