Fusion Engineering and Design 83(2008)1490-1494 Contents lists available at Science Direct Fusion engineering and design ELSEVIER journalhomepagewww.elsevier.com/locate/fusengdes Oxidation behavior of SiC/Sic composites for helium cooled solid breeder blanket S Nogami,, N Otake A Hasegawa,Y Katoh, A Yoshikawa, M. Satou Y Oya, K Okino Mepterime sc e and mech ence and Energy Tohoku University, 6-6-01, Aramaki-oza-Aoba, Aoba-ku, Sendai 980-8579, Japan nology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6138 USA Radiochemistry Research Laboratory, Faculty of Science, Shizuoka University, 836, Ohya, Suruga-ku, Shizuoka 422-8529, Japan ARTICLE INFO A BSTRACT In order to evaluate the oxidation behavior and mechanism of Sic/Sic com with conventional Available online 25 July 2008 pyroliticgraphite interface(Pyc-SiC/SiC)and advanced multilayer interface( ML-Sic/SiC)in a HCSB blanket environment, a thermal gravimetric analysis(tga)in He O2 environment at 1000C and 1200. was erformed. The Pyc-SiC/ SiC at 1200 Cand the MI at1000°Cand1200° showed relatively smaller eight change during oxidation because Sio2 formed on the Sic-matrix and Sic-fiber sealed the specime surface before the Pyc interface recession by gasification of graphite due to relatively high Sioz formation hermal gravimetric analysis rate. While the Pyc-SiC/Sic at 1000C showed significant weight loss because the specimen surface was Helium cooled solid breeder blanket not sealed by Sio2 and significant Pyc interface recession occurred due to relatively slow Sioz formation. O 2008 Elsevier B V. All rights reserved. 1. Introduction The purpose of this study is to evaluate the oxidation behavior nd mechanism of SiC/Sic composites with conventional pyrolite Silicon carbide(Sic) fiber reinforced Sic matrix composite graphite interface(PyC-SiC/SiC) and advanced multilayer inter- (SiC/SiC composite)is one of the candidate structural materials for face(ML-Sic/Sic)in He+O2 environment. A thermal gravimetric fusion reactor blanket because of its low induced radioactivity, analysis(TGa)was performed as an experimental approach for excellent high temperature mechanical properties and excellent evaluation. diation resistance [1]. Helium(He)gas cooled solid breeder blan ket(HCSB)has been considered as one of the blanket desig concepts using the sic/Sic composite for relatively high tempera- 2. Experimental ure plant operation[2. Chemical stability, especially an oxidation resistance, might be a key issue to be solved for the HCSB struc- Sic/SiC composites used in this work were fabricated by Hy therm. Reinforced Sic fiber was 1D Hi-Nicalon Type-S fiber. tural material because He gas in the HCSB might include partial sic matrix was p-SiC fabricated using an isothermal chemi oxygen. cal vapor infiltration (Cvi) process. The average thickness of The desired strength of SiC/Sic composite can be given by an optimised interface layer between the fiber and matrix In order to interface layers(pyrolitic graphite and Sic/c multilayer) 1000nm. mprove its mechanical properties, advanced interfaces such as a Monolithic B-SiC and monolithic pyrolitic graphite were also Sic/C multilayer and a porous SiC have been developed [3]. How- examined for comparison with the composite. They were fabricated oy oxidation under fusionreactor operating condition, for example, neering and Shipbuilding Company, Ltd. and by TOYO TANSO, Ltd C(s)+O2(g)=CO2(g) ith shape shown Table 1. The"ax b surface"in Table 1 of the block specimens 2C(s)+O2(g)=2c(g) was mechanically polished using 0.5 um diamond slurry. The axis"direction in the left figure of Table 1 corresponds to the fiber axis direction of the composite, crystalline growth direction of the orresponding author. Tel: +81 22 795 7924: fax: +81 22 7957924 monolithic B-SiC and a-axis of graphite structure of the monolithic pyrolitic grap 'S-see front matter 2008 Elsevier B.v. All rights reserved. 0.1016 fusengdes.2008.06004Fusion Engineering and Design 83 (2008) 1490–1494 Contents lists available at ScienceDirect Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes Oxidation behavior of SiC/SiC composites for helium cooled solid breeder blanket S. Nogami a,∗, N. Otakea, A. Hasegawaa, Y. Katohb, A. Yoshikawac, M. Satoua, Y. Oyac, K. Okunoc a Department of Quantum Science and Energy Engineering, Tohoku University,6-6-01, Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579, Japan b Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6138, USA c Radiochemistry Research Laboratory, Faculty of Science, Shizuoka University, 836, Ohya, Suruga-ku, Shizuoka 422-8529, Japan article info Article history: Available online 25 July 2008 Keywords: SiC/SiC composite Oxidation Interface Thermal gravimetric analysis Helium cooled solid breeder blanket abstract In order to evaluate the oxidation behavior and mechanism of SiC/SiC composites with conventional pyrolitic graphite interface (PyC-SiC/SiC) and advancedmultilayer interface (ML-SiC/SiC) in a HCSB blanket environment, a thermal gravimetric analysis (TGA) in He + O2 environment at 1000 ◦C and 1200 ◦C was performed. The PyC-SiC/SiC at 1200 ◦C and theML-SiC/SiC at 1000 ◦C and 1200 ◦C showed relatively smaller weight change during oxidation because SiO2 formed on the SiC-matrix and SiC-fiber sealed the specimen surface before the PyC interface recession by gasification of graphite due to relatively high SiO2 formation rate. While the PyC-SiC/SiC at 1000 ◦C showed significant weight loss because the specimen surface was not sealed by SiO2 and significant PyC interface recession occurred due to relatively slow SiO2 formation. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Silicon carbide (SiC) fiber reinforced SiC matrix composite (SiC/SiC composite) is one of the candidate structural materials for a fusion reactor blanket because of its low induced radioactivity, excellent high temperature mechanical properties and excellent radiation resistance [1]. Helium (He) gas cooled solid breeder blan￾ket (HCSB) has been considered as one of the blanket design concepts using the SiC/SiC composite for relatively high tempera￾ture plant operation [2]. Chemical stability, especially an oxidation resistance, might be a key issue to be solved for the HCSB struc￾tural material because He gas in the HCSB might include partial oxygen. The desired strength of SiC/SiC composite can be given by an optimised interface layer between the fiber and matrix. In order to improve its mechanical properties, advanced interfaces such as a SiC/C multilayer and a porous SiC have been developed [3]. How￾ever, SiC/SiC composites have a possibility of interface degradation by oxidation under fusion reactor operating condition, for example, by the following reactions [4]: C(s) + O2(g) = CO2(g) (1) 2C(s) + O2(g) = 2CO(g) (2) ∗ Corresponding author. Tel.: +81 22 795 7924; fax: +81 22 795 7924. E-mail address: shuhei.nogami@qse.tohoku.ac.jp (S. Nogami). The purpose of this study is to evaluate the oxidation behavior and mechanism of SiC/SiC composites with conventional pyrolitic graphite interface (PyC-SiC/SiC) and advanced multilayer inter￾face (ML-SiC/SiC) in He + O2 environment. A thermal gravimetric analysis (TGA) was performed as an experimental approach for evaluation. 2. Experimental SiC/SiC composites used in this work were fabricated by Hyper￾therm. Reinforced SiC fiber was 1D Hi-Nicalon Type-S fiber. SiC matrix was -SiC fabricated using an isothermal chemi￾cal vapor infiltration (ICVI) process. The average thickness of the interface layers (pyrolitic graphite and SiC/C multilayer) was 1000 nm. Monolithic -SiC and monolithic pyrolitic graphite were also examined for comparison with the composite. They were fabricated using a chemical vapor deposition (CVD) process by Mitsui Engi￾neering and Shipbuilding Company, Ltd. and by TOYO TANSO, Ltd., respectively. Samples were machined into blocks with shape shown in Table 1. The “a × b surface” in Table 1 of the block specimens was mechanically polished using 0.5 m diamond slurry. The “Z￾axis” direction in the left figure of Table 1 corresponds to the fiber axis direction of the composite, crystalline growth direction of the monolithic -SiC and a-axis of graphite structure of the monolithic pyrolitic graphite. 0920-3796/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2008.06.004