SiC/SiO2 Coating on Matrix Graphite Spheres of HTR Fuel Element Produced by a Two-Step Pack Cementation/High-Temperature Oxidation Process


Article Preview

Graphite is one of the most important material for the reactor core and fuel elements of high temperature gas-cooled reactor (HTR). Improving the oxidation resistance of graphite is very essential for the research of new fuel elements and the development of HTR. In this study, a gradient SiC layer of 500~700 μm was prepared on matrix graphite spheres by a two-step pack cementation, and the outer SiO2 layer prepared by the high-temperature oxidation process. The phases, microstructure, bonding strength and oxidation resistance of SiC/SiO2 coated matrix graphite spheres were investigated. The SiC/SiO2 coated matrix graphite spheres were carried on rapid thermal shocking tests from 1773 K to room temperature for 50 times without any cracks. The SiC/SiO2 coated matrix graphite spheres exhibits excellent anti-oxidation properties. No obvious weight loss was found after isothermal oxidation in air at 1273 K for 50 h and the weight gain was less than 1% at 1773 K in air for 50 h due to the oxidation of SiC layer.



Edited by:

Yu Xun Wang, Gui Chun Huang and Linqing Luo




P. Zhou et al., "SiC/SiO2 Coating on Matrix Graphite Spheres of HTR Fuel Element Produced by a Two-Step Pack Cementation/High-Temperature Oxidation Process", Materials Science Forum, Vol. 852, pp. 952-958, 2016

Online since:

April 2016




[1] Virgiliev Y S, Avramenko P Y, Grebennik V N. Structural graphite for high-temperature gas-cooled reactors [J]. Energy. 1991, 16(1-2): 309.


[2] Nickel H, Schubert F, Breitling H. Development and qualification of materials for structural components for the high-temperature gas-cooled reactor [J]. Nucl Eng Des. 1990, 121(2): 183.


[3] Thomas C R. The Royal Society of Chemistry, Science Park, Cambridge: Thomas Graham House[M]. 1993: 33.

[4] Dong Z J, Liu S X, Li X K, et al. Influence of infiltration temperature on the microstructure and oxidation behavior of SiC–ZrC ceramic coating on C/C composites prepared by reactive melt infiltration [J]. Ceramics International, 2015, 41: 797-811.


[5] Habuka H, Tsuji M. Chemical vapor deposition of amorphous silicon carbide thin films on metal surfaces using monomethylsilane gas at low temperatures [J]. Surface and Coatings Technology, 2013, 217: 88-93.


[6] Si-An CHEN, Chang-Rui ZHANG, Yu-Di ZHANG, et al. Effects of polymer derived SiC interphase on the properties of C/ZrC composites [J]. Materials & Design, 2014, 58: 102-107.


[7] Albano M, Morles R B, Cioeta F, et al. Coating effects on thermal properties of carbon carbon and carbon silicon carbide composites for space thermal protection systems [J]. Acta Astronautica, 2014, 99: 276-282.


[8] Chun-He TANG. Fuel Element of High Temperature Gas-cooled Reactors [M]. Beijing: Chemical Industry Press, 2007. (in Chinese).

[9] Cromarty R D, van Rooyen G T, de Villiers J P R. Crush strength of silicon carbide coated TRISO particles: Influence of test method and process variables [J]. Journal of Nuclear Materials, 2014, 445(1-3): 30-36.


[10] Jie GUAN. Study of Reaction-Coated SiC Coating on Graphite Matrix [D]. Tsinghua University, 1992. (in Chinese).

[11] Qing-Shan ZHU, Xue-Liang QIU, Chang-Wen MA. Oxidation resistant coating for matrix graphite of HTR-10's fuel elements [J]. High Technol lett. 1998, (03): 53. (in Chinese).

[12] Hong-Sheng ZHAO, Zhi-Qiang FU, Chun-He TANG, et al. Study of SiC/SiO2 oxidation-resistant coatings on matrix graphite for HTR fuel element [J]. Nucl Eng Des, 2014, (271): 217.

[13] Zhi-Qiang FU, Tong-Xiang LIANG, Jean-Charles Robin, et al. The stability of SiC coating and SiO2/SiC multilayer on the surface of graphite for HTGRs at normal service condition [J]. Appl Surf Sci. 2005, 240(1-4): 349.


[14] Knorr J, Kerber A, Moormann R. Upgrading (V) HTR fuel elements for generation IV goals by SiC encapsulation [J]. Kerntechnik [0932-3902]. 2012, 77(5): 351.


[15] Qian-Gang FU, He-Jun LI, Yong-Jie WANG, et al. A Si-SiC oxidation protective coating for carbon/carbon composites prepared by a two-step pack cementation [J]. Ceram Int. 2009, 35 (6): 2525.


[16] Xue-Jin ZHENG, A Rapp Robert. Siliconizing carbon fabrics at 1600°C [J]. Mater Sci Eng A. 1998, 255 (1-2): 75.

[17] Ling YIN, Shun GUO, Xiang XIONG, et al. High temperature anti-oxidation mechanism of residual Si in SiC coating prepared by pack cementation [J]. Acta Materiae Compositae Sinica. 2012, 29(1): 91. (in Chinese).

[18] Narushima T, Goto T, Iguchi Y, et al. High-temperature active oxidation of chemically vapor-deposited silicon carbide in an Ar-O2 atmosphere [J]. J Am Ceram Soc. 1991, 74(10): 2583.


[19] Wu-Zhuang ZHANG, Xiang XIONG, Yi ZENG. Preparation of SiC coating by pack cementation and effect of vacuum heating treatment on SiC coated C/C composites [J]. Materials Science and Engineering of Powder Metallurgy. 2011, 16(2): 231. (in Chinese).

[20] Geng-Sheng JIAO, He-Jun LI, Ke-Zhi LI, et al. Mechanism of defect formation and control of silicon carbide coating for carbon/carbon composites made by the pack cementation method [J]. J Chin Ceram Soc. 2007, 35(6): 721. (in Chinese).

[21] Vaughn W L, Maahs H G. Active-to-passive transition in the oxidation of silicon carbide and silicon nitride in air [J]. J Am Ceram Soc. 1990, 73(6): 1540.