Environmental barrier coatings

Environmental barrier coatings are a type of laminar composite. As with heat transfer, diffusion in laminar composites can be modeled as steady state diffnsion throngh a composite wall, as iUnstrated in Fignre 4.56. Here, hydrogen gas is in contact with solid material A at pressnre Pi and in contact with solid B at pressnre P2. At steady state, the molar flux of hydrogen throngh both walls mnst be the same (i.e., Jh ax = Bj) and Fick s Law [Eq. (4.4)] in the x direction becomes... 

Increase Temperature Stability Fiber-reinforced CMCs have been demonstrated to survive in the severe environment of a gas turbine engine for 2500 hours at temperatures up to 1200°C. The use of environmental barrier coatings (EBCs) such as oxide layers on SiC appears to help extend durability, but more research is needed to determine whether they present a long-term solution. 

Endurance testing in Solar s Centaur 505 engine has demonstrated that CVI SiC/SiC components can be introduced in Industrial Gas Turbines (Solar Turbines). To date, more than 47,000 hours of engine field test experience has been accumulated with protective environmental barrier coatings (EBCs). The longest single test duration was 15144 hours in Solar s Centaur 505 engines at industrial sites [4]. 

K.N. Lee, D.S. Fox, R.C. Robinson, and N.P. Bansal, Environmental Barrier Coatings for Silicon-Based Ceramics, in High Temperature Ceramic Matrix Composites, W. Krenkel, R. Naslain, and H. Schneider, Eds, Wiley-VCH, Weinheim, Germany, (2001), pp. 224-229. 

D. Zhu, N. P. Bansal, K. N. Lee, and R. A. Miller, Thermal Conductivity of Ceramic Thermal Barrier and Environmental Barrier Coating Materials, NASA/TM-2001-211122, Sept. 2001. 

Steve D, Eric B, Jim K, Andy W, Curt J (2003) Weibull strength parameter requirements for Si3N4 Turbine rotor reliability. Paper presented at the environmental barrier coatings workshop, Gaylord Opryland Resort Convention Center, Nashville, TN, USA, 18-19 Nov 2003 http //www.oml.gOv/sci/de materials/documents/DuffyEBC2003 000.pdf. Accessed on 18 May 2010... 

R.C. Robinson and J.L. Smialek, SiC recession caused by SiO scale volatility under combustion conditions 1, Experimental results and empirical model, Journal of the American Ceramic Society 82 1817-1825,1999 E.f. OpUa, f.L. Smialek, R.C. Robinson, D.S. Fox, andN.S. Jacobson, SiC recession caused by SiO scale volatility under combustion conditions II, Thermodynamics and gaseous-diffusion model. Journal of the American Ceramic Society 82 1826-1834,1999 P.F. TortoreUi and K.L. More, Use of very high water-vapor pressures to evaluate candidate compositions for environmental barrier coatings. Proceedings oftheASME Turbo Expo 2005 1 363-367,2005. 

The need for even higher engine efficiencies and performance requires materials that show extraordinary stability and resistance to degradation at environmental extremes of temperature, pressures, and reactive species. Increasingly robust environmental barrier coatings will be needed, or failures as those described in Box 1.3 will continue to occur. These coatings will require the development of even more advanced mechanistic knowledge and models. 

S. Ueno, N. Kondo, T. Ohji, S. Kanzaki, J. Doni, High Temperature Hydro Corrosion Resistance of Silica Based Oxide Ceramics , American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTl, v 1, 2003, p 625-632. K. N. Lee, Key Durability Issues With Mullite-Based Environmental Barrier Coatings for Si-Based Ceramics , Journal of Engineering for Gas Turbines and Power, Vol. 122, 632-636, October (2000). 

K. N. Lee, Current Status of Environmental Barrier Coatings for Si-Based Ceramics, Surf. Coatings Tech. 133-134 1-7 (2000). 

FABRICATION OF SLURRY BASED Y-Si-Al-0 ENVIRONMENTAL BARRIER COATING ON THE POROUS SI3N4 CERAMICS... 

KEY WORDS Environmental barrier coatings (EBC) Porous Si3N4 ceramics Y-Si-Al-O coatings Water absorption Flexural strength Dielectric constant and loss. 

Fabrication of Slurry Based Y-Si-AI-0 Environmental Barrier Coating... 

CREEP AND ENVIRONMENTAL DURABILITY OF ENVIRONMENTAL BARRIER COATINGS AND CERAMIC MATRIX COMPOSITES UNDER IMPOSED THERMAL GRADIENT CONDITIONS... 

Creep and Environmental Durability of Environmental Barrier Coatings... 

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