Seminars

David Clarke
Harvard University

Materials Challenges for the Next Generation Thermal Barrier Coatings
One of the major successes of engineered ceramics has been the development of the thermal protection system for high-temperature gas turbines. For the last twenty-five years, the ceramic material of choice as a thermal barrier coating has, and continues to be, yttria-stabilized zirconia containing 8 weight percent yttria (8YSZ).  As the development of more efficient gas turbines proceeds there is a need for an oxide coating that can sustain higher operating temperatures than 8YSZ.  However, no existing oxide has the required combination of low thermal conductivity, adequate fracture toughness, low optical absorption in the infra-red and high temperature stability as well as compatibility with alumina that forms on superalloys at high temperatures. In this presentation, I will discuss the design requirements for the next generation gas turbines as well as the new, additional challenges that coatings must meet to operate at the higher temperatures of the next generation engines.

About Dr. Clarke:
David Clarke is the inaugural holder of the Extended Tarr Family Professorship of Materials and Applied Physics at Harvard University and currently Area Chair for Mechanical Engineering and Materials Science in the School of Engineering and Applied Sciences.  He is best known for his work in ceramics, thermal barrier coatings, high temperature materials and, increasingly, dielectric elastomer devices. Amongst his best known work is the discovery of nanometer thick wetting films in ceramics, the explanation for their existence and their consequences on high-temperature properties, the development of photo-stimulated luminescence spectroscopy (PSLS) for non-contact measurement of stresses in aluminum oxide and thermally grown oxides, his extensive studies of varistor surge protectors, and the discovery of a wide range of low thermal conductivity ceramics for thermal barrier coatings of turbine materials.