Events - Daily
|Wednesday, October 03|
Seminar 10/3/2012 - Qiming Zhang, Penn State University: Beyond the Traditional Polarization Response in Polar-polymers
Full Title: Beyond The Traditional Polarization Response in Polar-polymers:
Some Amazing Properties of The Ferrorelaxor Polymers
Bio: Dr. Qiming Zhang is a distinguished Professor of Electrical Engineering and Materials Science and Engineering at Penn State University. He obtained a BS degree from Nanjing University in 1981 and Ph.D. from Penn State in 1986. He joined the Penn State faculty in 1991. His research interests include material developments and device applications of electronic and electroactive materials. Research activities in his group cover solid state actuators, sensors, transducers, dielectrics and energy storage and conversion devices, polymer thin film devices, polymer MEMS, electrocaloric effect and solid state cooling devices and electro-optic and photonic devices. His group has discovered and developed a class of ferroelectric relaxor polymer actuators which exhibit a large electrostrictive strain (>5%) with a high elastic modulus (~ 1 GPa). The polymer has been commercialized by Arkema and in 2006, he and Mr. Ralph Russo co-founded Strategic Polymer, Inc. at State College, PA, to commercialize the polymer actuators as well as dielectric capacitors, another invention from his group. More recently, his group discovered a giant electrocaloric effect over a broad temperature range in a class of ferrorelaxor polymers where a temperature change of 20 degree C can be induced under application of electric fields, attractive for on-chip cooling as well as for high efficiency compact heat pumps. He is the recipient of the 2008 Penn State Engineering Society Premier Research Award and a Fellow of IEEE.
Abstract: The direct and efficient coupling between the electric signals and the elastic, thermal, optical and magnetic signals in ferroelectric based electroactive polymers makes them attractive for exploiting a broad range of cross-coupling phenomena and applications which have great promise for new device technologies (see the figure). This talk will present the recent advances in developing electroactive polymers for solid state cooling. One major engineering challenge in this century is to develop alternative cooling technology to replace the century old vapor compression cycle (VCC) based cooling which employs strong greenhouse gases as the refrigerants and to provide thermal management of microelectronic components and computers. Electrocaloric effect (ECE), which is the temperature and entropy change of insulating dielectric materials under electric fields, is attractive to realize efficient cooling devices. However, the relatively small ECE observed in dielectrics in the last century make it unimpressive for any practical applications. By making use of phase transitions and the high dipolar entropy in these polymers in the dipolar disordered state we demonstrated that a giant ECE can be achieved in a class of ferroelctric polymers. Moreover, by employing defects modifications to convert the normal ferroelectric into a ferroelectric relaxor, a large ECE over a broad temperature range about room temperature can be obtained. This talk will also discuss considerations on further enhancing the ECE as well as solid state cooling device concepts, exploiting the newly discovered large ECE in ferrorelaxor polymers.
All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.
Bowen Hall Auditorium · 12:00 p.m.– 1:00 p.m.