报告题目： Advanced Dielectrics with Tailored Nanostructures for Energy Conversion and Storage
报告人：Prof.Qiming Zhang，The Pennsylvania State University, University Park Pennsylvania, USA
报告时间：2016年11月19日（星期六） 下午 15:00
联系人： 胡凤霞研究员 （电话：8264 9233）
Qiming Zhang is a Distinguished Professor of Electrical Engineering, Materials Science and Engineering, and Mechanical engineering of Penn State University.
The research areas in his group include fundamentals and applications of electronic and electroactive materials. During the 25 years stay at Penn State,
his group has conducted research covering actuators, sensors, transducers, dielectrics and charge storage devices, polymer thin film devices, polymer MEMS,
electrocaloric effect and solid state cooling devices and electro-optic and photonic devices. He has over 430 publications and 10 patents in these areas.
His group has discovered and developed a ferroelectric relaxor polymer which possesses room temperature dielectric constant higher than 50 with high
electrostrictive strain and elastic energy density (~1 J/cm3).1 His group demonstrated a new class of polar-polymer with electric energy density over 25 J/cm3
and has worked on nanocomposites and blends to achieve very low losses.2 More recently, his group discovered a giant electrocaloric effect over a broad
temperature range in a class of defects modified ferroelectric 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.3 He is the recipient of the 2008 Penn State Engineering Society Premier Research Award,
2015 Faculty Scholar Medal of Penn State, and a Fellow of IEEE and a Fellow of APS.
1. Q. M. Zhang, Vivek Bharti, and X. Zhao. Science, 280, 2101-2104 (1998).
2. Baojin Chu, Xin Zhou, Kailiang Ren, Bret Neese, Minren Lin, Qing Wang, F. Bauer, Science, 313, 334 (2006).
3. Bret Neese, Baojin Chu, Sheng-Guo Lu, Yong Wang, E. Furman, and Q. M. Zhang, Science, 321, 821-823 (2008).
The direct and efficient coupling between the electric signals and the elastic, thermal, optical and magnetic signals in dielectrics makes them attractive for exploring a broad
range of cross-coupling phenomena which have great promise for new device technologies. This talk will present recent advances in my group on dielectrics with controlled
nanostructures for energy conversion and storage. For example, electrocaloric (EC) materials with giant EC response which may provide alternative cooling technology to the
century old vapor compression cycle (VCC) based cooling. Electrocaloric effect (ECE), which is the temperature and/or entropy change of dielectric materials caused by the
electric field induced polarization change, is attractive to realize efficient cooling devices. Recently, we demonstrated that large ECE can be achieved in several classes of
ferroelectric materials with tailored nano- and meso-structures. Experimental results on the ECE in the relaxor ferroelectric polymers and general theoretical considerations
for achieving large ECE will be presented. This talk will also discuss general considerations on and present recent works of ECE in ferroelectric ceramics near the invariant
critical point. The works related to develop the EC cooling devices, making use of the newly developed large ECE and featuring high cooling power density and high efficiency,
will also be presented. As another example, I will also present that employing nanostructure engineering can lead to some amazing and unexpected dielectric responses and
significantly enhanced performances in dielectric energy storage materials.