Event
MSE Seminar - Professor Helen M. Chan, Lehigh University
Friday, October 10, 2008
1:00 p.m.
Rm. 2108, Chemical and Nuclear Engineering Bldg.
Annette Mateus
301 405 5207
amateus@umd.edu
Compositional Influences on Boundary Transport in Alumina: Applications to Scale Growth
Many commercial high temperature alloys are alumina-formers, i.e., they oxidize to form a slow-growing, protective alumina surface layer. The rate of growth of this layer is critical to the degree of oxidation resistance of such alloys, as well as to the lifetime of thermal barrier coatings. It is well recognized that certain reactive elements (e.g. Y, Hf) can have a beneficial effect on the oxidation rate. To elucidate the role of the dopant ions, model experiments have been carried out to probe the effect of ppm levels of Y on grain boundary transport in dense alumina samples, in the temperature range 1100 1500 deg. C. The grain boundary diffusion coefficient for Cr diffusion in alumina was extracted from the measurement of Cr concentration profiles. The oxygen transport kinetics were investigated separately using alumina samples containing a fine dispersion of Ni particles, which acted as markers of the oxidation front. The results showed that transport is suppressed in both cases, however, interesting differences in the behavior were observed. Possible mechanisms for the role of the dopant ion will be discussed.
Biography
Helen M. Chan, graduated from Imperial College (London) with a B.Sc. First Class Honours degree in Materials Science, and was the recipient of the Governors' Prize for most outstanding graduate. She was subsequently awarded a Ph.D. and D.I.C. from the same institution. Dr. Chan joined the faculty of the Dept. of Materials Science & Engineering, Lehigh University, in 1986. She subsequently spent 18-months at the National Institute of Standards and Technology, where she worked in the Mechanical Properties Group of the Ceramics Division. She was promoted to Full Professor in 1995, and currently holds the New Jersey Zinc Chair. In 2006, Dr. Chan was appointed Chairperson of the department. Her current research interests include the application of reactive processing to fabricate unique ceramic/metal structures, including cellular and nanopatterned materials. She is also actively involved in research on the role of dopants and interfacial chemistry on diffusion limited processes in ceramics. Dr. Chan is the author of more than 160 publications, and has received the American Ceramic Society Roland B. Snow award on five separate occasions (1986, 1990, 1992, 1999 and 2000). In 1990, Chan was awarded the Alfred Noble Robinson Award for "outstanding performance and unusual promise of professional achievement", and she has received Lehigh University's "Service Teaching Excellence Award" for two consecutive years (1991 and 1992). Chan was named the 1992 recipient of ASM International's Bradley Stoughton Award for outstanding young faculty in the field of Materials Science & Engineering. Dr. Chan was inducted as a Fellow of the American Ceramic Society in 2005, and chaired the 2008 Gordon Research Conference in Solid State Ceramics.
For more information, contact Annette Mateus at (301) 405-5207 or amateus@umd.edu.
