Availableonlineatwww.sciencedirect.com journal吖 ScienceDirect nuclear ELSEVIER Journal of Nuclear Materials 367-370(2007)1139-1143 materials www.elsevier.com/locate/jnucmat Coatings and joining for SiC and Sic-composites for nuclear energy systems C.H. Henager Jr. a.,Y. Shin a, Y. Blum b, L A Giannuzzi c B W. Kempshall d S.M. Schwarz d a Pacific Northwest National Laboratory, 902 Battelle Bled, MS P8-15, Richland, WA99352-0999, US.A SRI International Menlo Park. CA 94025. US. FEI Company, 5350 NE Dawson Creek Drive, Hillsboro, OR 97124, USA niversity of Central Florida and Nano Spectre, Inc, Orlando, FL 32826, USA Abstract atings and joining materials for SiC and Sic-based composites for nuclear energy systems are being developed using preceramic polymers filled with reactive and inert powders, and using solid-state reactions. Polymer-filled joints and coat ings start with a poly(hydridomethylsiloxane) precursor, such that mixtures of Al/AlO3/polymer form a hard oxide coat ing, coatings made with Al/SiC mixtures form a mixed oxide-carbide coating, while coatings made with SiC/polymer form a porous, hard carbide coating Joints made from such mixtures have shear strengths range from 15 to 50 MPa depending on the applied pressure and joint composition. The strongest joints were obtained using tape cast ribbons of Si/TiC pow ders such that a solid state displacement reaction at 1473 K and 1673 K using 30 MPa applied pressure resulted in shear trengths of 50 MPa, which exceeds the shear strength of SiC/SiC composite materials. However, the polymer joints are much easier to apply and could be considered for field repair Published by elsevier B.V. 1. Introducti of the fine-grained SiC fibers and of the fiber-matrix interphase material [2]. Further, joining of simple It is widely considered to be a weakness of Sic- shapes into more complex structures is also appar- based composites that they are not fully dense and ently required, particularly for fusion reactor first can, as yet, only be fabricated into simple shapes wall vessels that cannot possibly be made as a single that require development of attachment technolo- section [3]. Thus, a significant effort has gone into gies in order to achieve more complex configura- development and understanding of protective coat- tions. The implication of the lack of full density is ings and joining for SiC/SiC composites [1, 2, 4-12 that external coatings are required, both for herme- The Nano-powder infiltration and transient eutec- ticity considerations [1]and for corrosion protection toid(NITE) process, however, produces a SiC/SiC posite material with high densit Corresponding author. Tel +1 509 376 1442: fax: +1 509 376 ability, and has been used to demonstrate high-per 0418 formance hot-pressed joining [13-15]. The purpose E-mail address. chuck. henager @pnl gov (C.H. Henager Jr.). of this study is to help develop a wider range of 0022-3115/S see front matter Published by elsevier B v doi:10.1016 i-jnucmat2007.03.189Coatings and joining for SiC and SiC-composites for nuclear energy systems C.H. Henager Jr. a,*, Y. Shin a , Y. Blum b , L.A. Giannuzzi c , B.W. Kempshall d , S.M. Schwarz d a Pacific Northwest National Laboratory, 902 Battelle Blvd., MS P8-15, Richland, WA 99352-0999, USA b SRI, International Menlo Park, CA 94025, USA c FEI Company, 5350 NE Dawson Creek Drive, Hillsboro, OR 97124, USA d University of Central Florida and NanoSpective, Inc., Orlando, FL 32826, USA Abstract Coatings and joining materials for SiC and SiC-based composites for nuclear energy systems are being developed using preceramic polymers filled with reactive and inert powders, and using solid-state reactions. Polymer-filled joints and coat￾ings start with a poly(hydridomethylsiloxane) precursor, such that mixtures of Al/Al2O3/polymer form a hard oxide coat￾ing, coatings made with Al/SiC mixtures form a mixed oxide–carbide coating, while coatings made with SiC/polymer form a porous, hard carbide coating. Joints made from such mixtures have shear strengths range from 15 to 50 MPa depending on the applied pressure and joint composition. The strongest joints were obtained using tape cast ribbons of Si/TiC pow￾ders such that a solid state displacement reaction at 1473 K and 1673 K using 30 MPa applied pressure resulted in shear strengths of 50 MPa, which exceeds the shear strength of SiC/SiC composite materials. However, the polymer joints are much easier to apply and could be considered for field repair. Published by Elsevier B.V. 1. Introduction It is widely considered to be a weakness of SiC￾based composites that they are not fully dense and can, as yet, only be fabricated into simple shapes that require development of attachment technolo￾gies in order to achieve more complex configura￾tions. The implication of the lack of full density is that external coatings are required, both for herme￾ticity considerations [1] and for corrosion protection of the fine-grained SiC fibers and of the fiber–matrix interphase material [2]. Further, joining of simple shapes into more complex structures is also appar￾ently required, particularly for fusion reactor first￾wall vessels that cannot possibly be made as a single section [3]. Thus, a significant effort has gone into development and understanding of protective coat￾ings and joining for SiC/SiC composites [1,2,4–12]. The Nano-powder infiltration and transient eutec￾toid (NITE) process, however, produces a SiC/SiC composite material with high density, low perme￾ability, and has been used to demonstrate high-per￾formance hot-pressed joining [13–15]. The purpose of this study is to help develop a wider range of 0022-3115/$ - see front matter Published by Elsevier B.V. doi:10.1016/j.jnucmat.2007.03.189 * Corresponding author. Tel.: +1 509 376 1442; fax: +1 509 376 0418. E-mail address: chuck.henager@pnl.gov (C.H. Henager Jr.). Journal of Nuclear Materials 367–370 (2007) 1139–1143 www.elsevier.com/locate/jnucmat