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Wenwu Caophoto-Wenwu Cao

 

Professor of Mathematics and Materials Science

 

164 MRL Bldg.

Penn State University

University Park, PA 16802

Phone: (814) 865-4101

FAX: (814) 865-2326

E-mail: Validate to view contact info

Education:

 

  • Ph.D. in Physics, Penn State University, 1987
  • B.S. in Physics, Jilin University, 1982

 

Research Interests:

 

  • Nano-composites for matching layer in high frequency medical ultrasonic transducers
  • Mode coupling theory in piezoelectric resonators and boundary condition influence to the effective electromechanical coupling coefficients
  • High frequency medical ultrasonic transducers
  • Characterization of elastic, dielectric, and piezoelectric properties of piezoelectric single crystals and ceramics, particularly on the frequency dispersion of velocities and attenuation, using ultrasonic techniques
  • Nondestructive characterization of extremely thin samples and multilayer structures using ultrasonic method
  • Computer simulation of defect induced phase transition process in ferroelectrics, including nucleation, growth, and domain switching.
  • Finite element analysis on vibrational modes, wave propagation, and transient behavior of transducers, piezocomposites, and smart structures
  • Proper- and improper-ferroelastic phase transitions and transformation precursors in martensites

 

Prof. Cao’s research interests span both theoretical and experimental fields. He has formulated a continuum theory that can address domain formation and domain dynamics in ferroelectrics. He has also developed many theoretical models to describe piezoelectric composites, morphotropic phase boundary formation of PZT, defect influence to polarization switching, nonhomogeneous ferroelectric and ferroelastic phase transitions, and aspect ratio dependence of electromechanical coupling coefficients of piezoelectric resonators. His experimental work is mainly focused on the use of ultrasonic method to probe nondestructively the interior of multilayer structures and to characterize material properties of ceramics, single crystals, and thin films. His group has developed a unique method to measure the full matrix properties of piezoelectric materials. His ultrasonic lab is equipped to design and fabricate ultrasonic transducers for medical imaging and for many other ultrasound assisted applications.

 

Technologies Impacted by Research:

 

  • High frequency high resolution medical ultrasonic imaging
  • SONAR
  • Smart structures
  • Multilayer capacitors and actuators
  • Piezoelectric sensors
  • Thin film devices
  • Thin layer nano-composites

 

Professional Experience:

 

2001 to present Professor of Mathematics and Materials Science, Penn State
1995-2001 Associate Professor of Mathematics and Materials Science, Penn State
1993-1995 Senior Research Associate and Associate Professor of Materials, Penn State
1990-1993 Research Associate and Assistant Professor of Materials, Penn State
1989-1990 Postdoc Associate, Lab. of Atomic Solid State Physics, Cornell University
1987–1989 Research Associate, Materials Research Lab. Penn State

 

 

Selected Publications:

 

  1. H. Wang and W. Cao, “Characterize Ultra Thin Matching Layers of High Frequency Ultrasonic Transducer Based on Impedance Matching Principle”, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, vol. 51, pp. 211-215 (Feb. 2004).
  2. M. Kim, J. Kim and W. Cao, “Aspect Ratio Dependence of Electromechanical Coupling Coefficient of Piezoelectric Resonators”, Applied Physics Letters, vol. 87, pp. 132901 (Sep. 19, 2005).
  3. R. Ahluwalia, T. Lookman, A. Saxena and W. Cao, “Domain Size Dependence of Piezoelectric Properties of Ferroelectrics”, Physical Review B, vol. 72, 014112, (Jul. 1, 2005).
  4. Jie Zhu and Wenwu Cao, “Ultrasonic Attenuation and Velocity Changes in Multilayer Structures Containing Multiple Delaminations”, Materials Evaluation, vol. 64, pp 417-422 (April, 2006).
  5. R. Zhang, W. Cao, Q. Zhou, Y. Huang and K. K. Shung, “Properties of Nano-composite Matching Layers”, IEEE Transactions on Ultrosonics, Ferroelectrics and Frequency Control, vol. 54, pp. 467-469 (March, 2007).