Science Direct E噩≈RS ELSEVIER Joumal of the European Ceramic Society 30(2010)1131-1137 r. com/loca Fabrication of cnt-SiC/Sic composites by electrophoretic deposition Katja Konig Sasa Novak a,, Aljaz Ivekovic a, Katja Rade Decheng Meng Aldo r Boccaccini, Spom Department for Nanostructured Materials, Jozef Stefan Institute, Ljubljana, Slovenia Available online 20 August 2009 Due to the outstanding mechanical and thermal properties of carbon nanotubes( CNTs), they are considered suitable reinforcement for structural materials. In this study, for the first time, electrophoretic deposition(EPD)was used to deposit(multi-walled) CNTs onto SiC fibres(SiCt) orm an effective CNT interphase layer for SiC:/SiC composites. This deposition was followed by electrophoretic infiltration of the CNT-coated Sic fibre mats with Sic powder to fabricate a new CNT-SiC-fibre-reinforced Sic-matrix(SiC/SiC)composite for fusion applications. In these EPD experiments, a commercial aqueous suspension of negatively charged CNTs and an optimized aqueous suspension of negatively charged Sic particles were used. The CNT-coatings on the SiC fibres were firm and homogenous, and uniformly distributed nanotubes were observed on the fibre surfaces. In a following step of EPD, a thick Sic layer was formed on the fibre mat when the CNT-coated SiC fibres were in contact with the positive electrode of the EPD cell; however, spaces between the fibres were not fully filled with SiC. Conversely, when CNT-coated SiC fibres were isolated from the electrode, the Sic particles were able to gradually fill the fibre mat resulting in relatively high infiltration, which leads to dense composites 2009 Elsevier Ltd. All rights reserved. Keywords: Electrophoretic deposition; SiC:/SiC composite; Carbon nanotubes(CNTs) Coatings: Interphase 1. Introduction an interphase layer, typically pyrolitic carbon of 100-500nm that is usually deposited by a chemical vapour deposition(CVD) Continuous SiC-fibre-reinforced Sic composites have been process, and has the main task to protect the material from catas- recognized as promising materials for use in the structural parts trophic fracture by deflecting the propagating crack and inducing of future fusion reactors due to the high thermal stability of Sic fibre pull-out, which is the most efficient toughening mechanism offering the possibility of high temperature operation of the reac- in this class of composites tor and hence more economic energy production. In addition, However, no state-of-the-art material meets all of the due to the low neutron activation of pure SiC, these composites highly demanding requirements for use in fusion reactors. The represent a way to minimise the amount of radioactive waste ceramic composites, for example, are associated with several generated during reactor operation in comparison with ferrous still unresolved issues, including gas permeability, insufficient materials. To ensure sufficient fracture toughness and reliabil- mechanical properties at high temperature, too high neutron ty of the material, Sic is proposed to be used in the form of activation, too low thermal conductivity, and instability of the continuous SiC-fibre-reinforced SiC ceramics, i.e., a( SiCr/Sic) fibres at high temperatures. The thermal conductivity and the composite. The composite is composed of SiC fibres woven mechanical properties of a composite are highly dependent on in a 2D or 3D architecture, filled with a matrix material that is the chemical composition of its three constituents(the matrix either pure Sic produced by chemical vapour infiltration or by material, the fibres, and the interphase layer), and on its porosity infiltration of a polymer precursor, or with a particulate com- Among the strategies to improve the overall performance of posite of a liquid phase sintered SiC. The fibres are coated with SiCrSiC composites, in particular to increase their mechani cal strength and thermal conductivity, incorporation of carbon nanotubes(CNTs)is highly promising, due to their outstanding Corresponding author at: Jamova cesta 39. SI-1000 Ljubljana. Sloveni mechanical and thermal properties. The CNTs are characterised Te.:+38614773271;fax:+38614773221l not only by a very high thermal conductivity(2000 W/mkp-7 E-mail address: sasa. novak@ijs si(S. Novak) and ability to increase the toughness of intrinsically brittle 0955-2219 front matter@ 2009 Elsevier Ltd. All rights reserved. doi: 10. 1016/j-jeurceramsoc. 2009.07.027Available online at www.sciencedirect.com Journal of the European Ceramic Society 30 (2010) 1131–1137 Fabrication of CNT-SiC/SiC composites by electrophoretic deposition Katja König a, Sasa Novak ˇ a,∗, Aljaz Ivekovi ˇ cˇ a, Katja Rade a, Decheng Meng b, Aldo R. Boccaccini b, Spomenka Kobe a a Department for Nanostructured Materials, Joˇzef Stefan Institute, Ljubljana, Slovenia b Department of Materials, Imperial College London, London, UK Available online 20 August 2009 Abstract Due to the outstanding mechanical and thermal properties of carbon nanotubes (CNTs), they are considered suitable reinforcement for structural materials. In this study, for the first time, electrophoretic deposition (EPD) was used to deposit (multi-walled) CNTs onto SiC fibres (SiCf) to form an effective CNT interphase layer for SiCf/SiC composites. This deposition was followed by electrophoretic infiltration of the CNT-coated SiC fibre mats with SiC powder to fabricate a new CNT-SiC-fibre-reinforced SiC-matrix (SiCf/SiC) composite for fusion applications. In these EPD experiments, a commercial aqueous suspension of negatively charged CNTs and an optimized aqueous suspension of negatively charged SiC particles were used. The CNT-coatings on the SiC fibres were firm and homogenous, and uniformly distributed nanotubes were observed on the fibre surfaces. In a following step of EPD, a thick SiC layer was formed on the fibre mat when the CNT-coated SiC fibres were in contact with the positive electrode of the EPD cell; however, spaces between the fibres were not fully filled with SiC. Conversely, when CNT-coated SiC fibres were isolated from the electrode, the SiC particles were able to gradually fill the fibre mat resulting in relatively high infiltration, which leads to dense composites. © 2009 Elsevier Ltd. All rights reserved. Keywords: Electrophoretic deposition; SiCf/SiC composite; Carbon nanotubes (CNTs); Coatings; Interphase 1. Introduction Continuous SiC-fibre-reinforced SiC composites have been recognized as promising materials for use in the structural parts of future fusion reactors due to the high thermal stability of SiC offering the possibility of high temperature operation of the reac￾tor and hence more economic energy production.1 In addition, due to the low neutron activation of pure SiC, these composites represent a way to minimise the amount of radioactive waste generated during reactor operation in comparison with ferrous materials. To ensure sufficient fracture toughness and reliabil￾ity of the material, SiC is proposed to be used in the form of continuous SiC-fibre-reinforced SiC ceramics, i.e., a (SiCf/SiC) composite.1–3 The composite is composed of SiC fibres woven in a 2D or 3D architecture, filled with a matrix material that is either pure SiC produced by chemical vapour infiltration or by infiltration of a polymer precursor, or with a particulate com￾posite of a liquid phase sintered SiC. The fibres are coated with ∗ Corresponding author at: Jamova cesta 39, SI-1000 Ljubljana, Slovenia. Tel.: +386 1 477 3271; fax: +386 1 477 3221. E-mail address: sasa.novak@ijs.si (S. Novak). an interphase layer, typically pyrolitic carbon of 100–500 nm that is usually deposited by a chemical vapour deposition (CVD) process, and has the main task to protect the material from catas￾trophic fracture by deflecting the propagating crack and inducing fibre pull-out, which is the most efficient toughening mechanism in this class of composites.4 However, no state-of-the-art material meets all of the highly demanding requirements for use in fusion reactors. The ceramic composites, for example, are associated with several still unresolved issues, including gas permeability, insufficient mechanical properties at high temperature, too high neutron activation, too low thermal conductivity, and instability of the fibres at high temperatures. The thermal conductivity and the mechanical properties of a composite are highly dependent on the chemical composition of its three constituents (the matrix material, the fibres, and the interphase layer), and on its porosity. Among the strategies to improve the overall performance of SiCf/SiC composites, in particular to increase their mechani￾cal strength and thermal conductivity, incorporation of carbon nanotubes (CNTs) is highly promising, due to their outstanding mechanical and thermal properties. The CNTs are characterised not only by a very high thermal conductivity (>2000 W/mK)5–7 and ability to increase the toughness of intrinsically brittle 0955-2219/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2009.07.027