Interface coatings

In summary, for the reference case the cost to produce the fiber is estimated to be 10.3/lb. Multiplying this by a value of five to account for overhead and profit suggests that the fiber could be sold for about 50/lb. This is sufficiently low to promote much wider use of composites in both the commercial and defense sectors. 

Fibers used as reinforcements in ceramic or metal matrix composites are usually coat- 

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A multiphase system consisting of a hydrocarbon solvent, a strong alkaline solution, and a quaternary onium salt, in the presence of a Pd/C catalyst with hydrogen that was bubbled at atmospheric pressure through the organic phase, allows the rapid displacement of chlorine from polyhalogenated benzenes. The onium salt, insoluble in both phases, is localized in the interfaces, coats the Pd/C catalyst, and constitutes the phase in which the reaction takes... 

Wider use of fiber-reinforced ceramic matrix composites for high temperature structural applications is hindered by several factors including (1) absence of a low cost, thermally stable fiber, (2) decrease in toughness caused by oxidation of the commonly used carbon and boron nitride fiber-matrix interface coatings, and (3) composite fabrication (consolidation) processes that are expensive or degrade the fiber. This chapter addresses how these shortcomings may be overcome by CVD and chemical vapor infiltration (CVI). Much of this chapter is based on recent experimental research at Georgia Tech. 

Segadaes et al. [79] Cooper and Hall [80] and Morgan and Marshall [81] have proposed the use of j3-aluminas, the related magnetoplumbite oxides, micaceous materials, and monazites as interface coatings for ceramic matrix composites. The principle... 

More recently, Morgan and Marshall have suggested that compounds having the monazite crystal structure may be useful oxidation interface coatings. Specifically, they recommend the compound LaP04. Their sol-gel experiments with this compound are encouraging. 

R. H. Richards, The Chemical Vapor Deposition of Hexagonal Aluminates as a Fiber-Matrix Interface Coating for Oxide-Oxide Composites, M.S. Thesis, School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, February 1995. 

Continuous-length ceramic fibers used to reinforce CMCs must have optimal mechanical, physical, and chemical properties (described in Chapter 2). This chapter reviews the characteristics of fibers that are commercially available and fibers that are at an advanced stage of development. The performance characteristics of interest include stiffness (i.e.. Young s modulus), strength, thermal and electrical conductivity, creep and rupture resistance, oxidation resistance, all as a function of temperature, and strength and stiffness retention as a fimetion of serviee history. The critical issue of chemical compatibility with prospective interface coatings and the eeramie matrix is addressed in Chapter 4 and Chapter 6. 

The utility of oxide fibers in composites can also be enhanced by using heat treatments to produce in-situ interface coatings. For instance, Nextel 312 (which contains 14 percent... 

Chayka, Y.P.V. 1997. Liquid MOCVD precursors and their application to fiber interface coatings. Ceramic Engineering and Science Proceedings 18(3) 287-294. ... 

Keller, K.A., T. Mah, C M. Cooke and T.A. Parthasarathy. 1997. High-temperature, long-term stability of oxide-oxide composites with fugitive interface coatings. Presented at the 21st Annual Cocoa Beach Conference and Exposition on Composites, Advanced Ceramics, Materials and Structures, January 12-16, 1997, Cocoa Beach, Florida. 

Mah, T., K. Keller, T.A. Parthasarathy, and J. Guth. 1991. Fugitive interface coating in oxide-oxide composites aviability study. Ceramic Engineering and Science Proceedings 12(9-10) 1802-1815. ... 

Sambasivan, S., J.A. Morris., and W.T. Petuskey. 1996. Rb P-Alumina as an interface coating in oxide CMCs. Ceramic Engineering and Science Proceedings 17(4) 250-257. ... 

S. T. Gonczy, E. P. Butler, N. R. Khasgiwale, L. Tsakalakos, W. R. Cannon, and S. C. Danforth, Blackglas-Nicalon composites with CVD boron nitride fiber interface coatings,... 

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