BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Environmental challenges to the implementation of ceramic composit
 es in gas turbines - Carlos G. Levi\, Materials Department\, University of
  California Santa Barbara
DTSTART:20140716T090000Z
DTEND:20140716T100000Z
UID:TALK53340@talks.cam.ac.uk
CONTACT:Ms Helen Gardner
DESCRIPTION:Gas turbine technology is at a cross-roads\, with demands for 
 increased engine performance and fuel flexibility translating into higher 
 material temperatures\, up to 1500°C in some designs\, and more chemicall
 y aggressive environments for the hot gas path components.  One promising 
 strategy to overcome the limitations of Ni-base superalloys is based on th
 e utilization of ceramic composites (CMCs).  Oxide-based composites have s
 uperior environmental stability but are limited by the temperature capabil
 ity of the fibers and thermomechanical concerns.  Hence\, much of the curr
 ent effort is focused on SiCf/SiCm systems\, which are critically dependen
 t on the performance of two types of coating systems.  Fiber coatings enab
 le de-coupling of the fibers and matrix at their interfaces during crack p
 ropagation\, while engineered surfaces protect the CMC from various forms 
 of environmental attack.  This presentation will discuss the challenges to
  the implementation of CMCs arising from issues related to the coating sys
 tems and the associated scientific issues.  Notably\, CMCs are susceptible
  to temperature embrittlement in the 700-900°C range due to the oxidative
  degradation of the fiber-matrix interfaces when cracks propagate in the m
 atrix.  Moreover\, the environmental barrier coatings have a complex archi
 tecture because they must incorporate multiple layers for different functi
 ons\, with attendant implications for the thermo-chemical and thermo-mecha
 nical stability of the system.  While feasible architectures have been ide
 ntified\, these systems are still vulnerable to extrinsic forms of damage 
 associated with the penetration and impact of particulate materials in the
  gas stream.  Strategies based on modified SiC matrices with self-healing 
 capabilities and lower defect densities have been proposed to improve the 
 robustness of the system against damage. The challenges involved in implem
 enting these concepts will be discussed.\nAcknowledgments: The presentatio
 n benefits from various intramural and extramural collaborations and inclu
 des contributions from past and present graduate students (K.M. Grant\, N.
 M. Larson\, M.D. Novak\, D.L. Poerschke\, R.B. Reitz\, E.M. Zaleski) and p
 ost-docs (S. Burk\, R.W. Jackson\, S. Krämer\, N. Verma\, J.Y. Yang).  Re
 search support provided by programs from the P&W Center of Excellence in C
 omposites\, the Office of Naval Research and the Air Force Office of Scien
 tific Research.  \nAbout the speaker:  C.G. Levi received a Ph.D. in Metal
 lurgical Engineering from the University of Illinois at Urbana-Champaign a
 nd has been in the faculty at UCSB since 1984\, where he is Professor of M
 aterials and Mechanical Engineering. The overarching theme of his research
  is the fundamental understanding of microstructure evolution in inorganic
  materials\, and the application of this understanding to the design and s
 ynthesis of improved coatings\, thin films\, composites and monolithic sys
 tems\, with emphasis on high temperature applications.  Current areas of w
 ork include thermal and environmental barrier coatings for advanced gas tu
 rbine components\, self-healing matrices and fibers for CMCs\, environment
 al barrier layers for advanced nuclear energy systems\, novel high tempera
 ture alloys and multi-phase functional materials.  He is a Fellow of the A
 merican Ceramic Society (2012) and has received the TMS Morris Cohen Award
  (2014)\, the 2008 NIMS Award\, the DLR Wissenschaftspreis (2004)\, the Al
 exander von Humboldt Forschungspreis (2002)\, the 1989 Grossman Award and 
 the 1982 Howe Medal from ASM International.
LOCATION: Cambridge University Engineering Department\, LR5
END:VEVENT
END:VCALENDAR