Availableonlineatwww.sciencedirect.com Science Direct E噩≈RS ELSEVIER Joumal of the European Ceramic Society 28(2008)2801-2807 www.elsevier.comlocate/jeurceramsoc Electrophoretic deposition in the production of Sic/Sic composites for fusion reactor applications Sasa Novak a, * Katja Rade a, Katja Konig a, Aldo R. Boccaccinib Department for Nanostructured Materials, Jozef Stefan Institute, Ljubljana, Slovenia b Department of Materials, Imperial College London, South Kensington Campus, London SW72BP UK Received 5 January 2008: received in revised form 25 March 2008: accepted 4 April 2008 Available online 2 June 2008 Abstract This paper presents the results of a study aimed at developing a technique for the infiltration of a SiC-fibre fabric with a low-activation SiC-based matrix material by aid of electrophoretic deposition from aqueo ensions. To achieve the best possible particle packing in the infiltrated matrix and hence to minimise the shrinkage during drying, the effect of the suspensions composition was analysed. Besides the ph change, different types of surfactants-PEL, CTAB, citric acid and Dolapix-were included in the investigation. As a result, during the deposition onto a metallic electrode, the best deposits were obtained with the addition of CTAb or by increasing the ph, while the infiltration of the Sic-fibre fabric wa more effective with negatively charged particles in the suspension o 2008 Elsevier Ltd. all rights reserved. Keywords: Silicon carbide; Aqueous suspensions; Surfactants; Electrophoretic deposition; Electrophoretic infiltration; SiC/SiC composites; Fusion 1. ntroduction limit the potential for SiC-based composites to be seriously con- sidered as suitable materials for the next generation of fusion Continuous Sic-fibre-reinforced SiC-matrix composites reactors. For this reason, efforts are being made worldwide (SiC/SiC) are recognised as promising materials to solve the demanding issues related to processing of SiC/Sic demanding applications due to their ability to resist composites. One key issue is related to the feasibility of achiev- conditions, for example, in heat-engine components in full infiltration of the sic-fibre fabric with a low-activation propulsion and in the structural parts of future fusion reactors. 2 matrix material The aim of this investigation is to develop a Sic-based compos- The infiltration of Sic-fibre woven fabric with a sic-matrix ite that will effectively substitute the currently favoured ferrous material has been undertaken by various techniques, notably materials, which are proposed to be used in future fusion reac- chemical vapour infiltration(CVI) and polymer infiltration and tors mainly due to the high degree of present technological pyrolysis(PIP). Unfortunately, these are very slow and costly development of relevant alloys. On the contrary, the fusion- processes and/or result in an incomplete filling of the gaps relevant SiC-based composites are the least well developed between the fibres in the tows. In addition to CVI and PIP, among the candidate materials for a reactor; however, using which result in incomplete filling and the formation of highly SiC/SiC composites for the blanket structural component could amorphous SiC, further attempts have been based on using lead to a significant increase in the maximum operating tem- ceramic routes. Among them, the recently introduced NT perature and, moreover, the material would not decay under process, based on a transient eutectic-phase route, , seems neutron irradiation to produce long-lived radioactive waste. to be the best suited to meet the requirements for a mate- There are. however some critical issues. such as insufficient rial to be used in a fusion reactor The infiltration in this hermeticity, swelling and various technological obstacles, that process is performed by slip infiltration, followed by assisted liquid-phase sintering of the SiC matrix using Al2O3 and Y2O3 as the sintering aids. Most recently, there have orresponding author. been attempts to avoid or at least minimise these additives E-lmail address: sasa. novak @ijssi(S. Novak) with the aim to produce a material with the lowest pos 0955-2219/S-see front matter o 2008 Elsevier Ltd. All rights reserved. doi: 10. 1016/j-jeurceramsoc. 2008.04.004Available online at www.sciencedirect.com Journal of the European Ceramic Society 28 (2008) 2801–2807 Electrophoretic deposition in the production of SiC/SiC composites for fusion reactor applications Sasa Novak ˇ a,∗, Katja Rade a, Katja Konig ¨ a, Aldo R. Boccaccini b a Department for Nanostructured Materials, Joˇzef Stefan Institute, Ljubljana, Slovenia b Department of Materials, Imperial College London, South Kensington Campus, London SW7 2BP, UK Received 5 January 2008; received in revised form 25 March 2008; accepted 4 April 2008 Available online 2 June 2008 Abstract This paper presents the results of a study aimed at developing a technique for the infiltration of a SiC-fibre fabric with a low-activation SiC-based matrix material by aid of electrophoretic deposition from aqueous suspensions. To achieve the best possible particle packing in the infiltrated matrix and hence to minimise the shrinkage during drying, the effect of the suspension’s composition was analysed. Besides the pH change, different types of surfactants – PEI, CTAB, citric acid and Dolapix – were included in the investigation. As a result, during the deposition onto a metallic electrode, the best deposits were obtained with the addition of CTAB or by increasing the pH, while the infiltration of the SiC-fibre fabric was more effective with negatively charged particles in the suspension. © 2008 Elsevier Ltd. All rights reserved. Keywords: Silicon carbide; Aqueous suspensions; Surfactants; Electrophoretic deposition; Electrophoretic infiltration; SiC/SiC composites; Fusion 1. Introduction Continuous SiC-fibre-reinforced SiC-matrix composites (SiC/SiC) are recognised as promising materials for many demanding applications due to their ability to resist extreme conditions, for example, in heat-engine components in aerospace propulsion and in the structural parts of future fusion reactors.1,2 The aim of this investigation is to develop a SiC-based compos￾ite that will effectively substitute the currently favoured ferrous materials, which are proposed to be used in future fusion reac￾tors mainly due to the high degree of present technological development of relevant alloys. On the contrary, the fusion￾relevant SiC-based composites are the least well developed among the candidate materials for a reactor; however, using SiC/SiC composites for the blanket structural component could lead to a significant increase in the maximum operating tem￾perature and, moreover, the material would not decay under neutron irradiation to produce long-lived radioactive waste.3 There are, however, some critical issues, such as insufficient hermeticity, swelling and various technological obstacles, that ∗ Corresponding author. E-mail address: sasa.novak@ijs.si (S. Novak). limit the potential for SiC-based composites to be seriously con￾sidered as suitable materials for the next generation of fusion reactors.4–6 For this reason, efforts are being made worldwide to solve the demanding issues related to processing of SiC/SiC composites. One key issue is related to the feasibility of achiev￾ing full infiltration of the SiC-fibre fabric with a low-activation matrix material. The infiltration of SiC-fibre woven fabric with a SiC-matrix material has been undertaken by various techniques, notably chemical vapour infiltration (CVI) and polymer infiltration and pyrolysis (PIP). Unfortunately, these are very slow and costly processes and/or result in an incomplete filling of the gaps between the fibres in the tows. In addition to CVI and PIP, which result in incomplete filling and the formation of highly amorphous SiC, further attempts have been based on using ceramic routes. Among them, the recently introduced NITE process, based on a transient eutectic-phase route,7,8 seems to be the best suited to meet the requirements for a mate￾rial to be used in a fusion reactor. The infiltration in this process is performed by slip infiltration, followed by pressure￾assisted liquid-phase sintering of the SiC matrix using Al2O3 and Y2O3 as the sintering aids. Most recently, there have been attempts to avoid or at least minimise these additives with the aim to produce a material with the lowest pos- 0955-2219/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2008.04.004