May 2004 Efect of YAG Additions on Porous-Alumina-Matrix omposites >s. G. Steel. L P. Zawada, and S. Mall,"Fatigue Behavior of a Nextel Nextel 610 fiber tows were incorporated into matrices contain ing differing amounts of YAG. In all cases, the composites PE. L Brady, "Chemical Nature of Silica Carried by Steam. "/. Phvs. Chem.57 containing YAG in the matrix had greater strengths than the 706-10(1953) composites containing an all-alumina matrix after exposure to CM. C Cheng and 1. B. Cutler. "Vaporization of Silica in Steam Atmosphere. 1200 C for times of up to 100 h. No direct correlation between the D. L Hildenbrand and K. H. Lau, " Thermochemistry of Gaseous SiO(OH) YAG volume fraction of the matrix and strength after heating at 1200C could be made. However, strengths were higher when E J. Opila. D S. Fox and N.S. Jacobson. "Mass dentification of YAG was used as the binder phase. It is believed that the presence 1-O-Hig) Species from the Reaction of Silica with Water Vapor at Atmospheric of YAG in the alumina matrix of the composites acts to inhibit Pressure, J, Am. Ceram Soc., 80 [41 1009-12(199 IM. K. Cinibulk, T. A. Parthasarathy, K. A. Keller. and T. Mah."Porous ocal densification, thereby maintaining a higher level of uniform Rare-Eanth Aluminate Fiber Coatings for Oxide Oxide Composites," Ceran. Eng porosity and weaker interparticle bonding that allows for crack Sc.Pmo,2l141219-28(2000 nergy dissipation. The reduction of grain growth of the fibers by M. K. Cinibulk. K. A Keller, T Mah, and T. A Parthasarathy. "Nextel 610 an the presence of segregated Y may also contribute to higher fiber 650 Fiber Reinforced Porous Aluminn-YAG Matrix Composites, " Ceram. Eng. Sci Pmoc22|31677-86(2001) strength, thereby increasing the retained strengths of the YAG M. K. Cinibulk, K. A. Keller, T. Mah, and T. A. Parthasarathy.""Nextel 6l0 containing composites. The incorporation of YAG into the matrix Fiber-Reinforced Alumina-YAG Porous Matrix Composites, "Ceram. Eng.Sei. may offer a simplified method for obtaining an alumina composite with improved properties similar to that which is obtained with an M. K. Cinibulk, "Effect of Yttria and Yttrium Aluminum Garnet Additions on the Densification and Grain Growth of Alumina at 1200-1300 C. "J. Am. Cern. Soc appropriate fiber coating, thus obviating the need for a separate 8714)692-95 tiber-coating step during composite processing in some instances. M.K. Cinibulk,"Synthesis of Yttrium Aluminum Garnet from a Mixed-Metal Citrate Precursor, "J. Am. Ceram. Soc., 83 15| 1276-78(2000) Acknowledgments 2M. K. Cinibulk, I. R. Welch, and R. S. Hay. "Preparation of Thin Sections of Coated Fibers for Characterization by Transmission Electron Microscopy. "J.Amm Ceran.Soe.7992481-84(1996) We thank T, A, Parthasarathy for fruitful discussions. 2M. K. Cinibulk, J. R. Welch, and R S. Hay. 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