S Novak et al. Journal of the European Ceramic Society 28 (2008)2801-2807 2805 in this study were seen to be negatively charged(Fig. 4, open was used as the anode. The infiltrated green samples were dried square symbols)exhibiting similar behaviour to the Sic pow- slowly and examined with an optical microscope. Further they der(see Fig. 1). The fibres were then treated with the anionic were vacuum infiltrated with a resin and examined by SEM to surfactant SDOSS in order to improve the wetting with aqueous estimate the success of the infiltration slurries, which also resulted in a slight increase in the negative Fig. 5a illustrates the as-received Sic-fibre fabric before ZP value(Fig. 4, close square symbols) infiltration, while Fig. 5b and c show the surfaces of the fab- The Sic-fibre fabric was first used as a deposition electrode, rics electrophoretically infiltrated with negatively or positively but no deposit was formed within 5 min. The current during the charged SiC particles, respectively. In the first case the fibres deposition was very low, probably due to the conductivity of the were pre-treated with SDOSs. In this case most of the large fibres being too low. Then, one or several layers of the fabric voids between the fibre tows were filled and the particles homo- were placed in front of the steel electrode, so that the particles geneously coated the surface of the fabric(Fig. 5b), while the were forced to travel through the fabric towards the electrode. positively charged suspension seems to flocculate on contact In order to prevent the formation of bubbles in the deposit a with the negatively charged fibres. sEM observations(Fig. 6a membrane was placed in front of the fabric at the cathode or, and b) suggest that in the case of positively charged particle in the case of negatively charged particles, a copper electrode they attach themselves to the fibres rather than entering the fibre tows interspaces. This is in agreement with a previously pro- by EPD, which indicates that a more efficient infiltration can be achieved by using equal-sign charges of the fibres and particles rather than using opposite charges A low-angle cross-section of a green part prepared with negatively charged suspension, infiltrated with a polymer and carefully polished, was also observed by' distinguish the means of sem as shown in Fig. 7, taking special care to Sic-infiltrated parts(the light phase in Fig. 7a) from the polymer- infiltrated parts(dark areas in Fig. 7a, see the arrows).As illustrated in Fig. 7b and c, which show the light areas, SiC particles have effectively filled the narrow gaps between the (a)圆 0,2mm Fig. 5. Optical micrographs of the starting fibre fabric (a), the fabric infiltrated with a TMAH-dispersed SiC suspension(b) and the fabric infiltrated with the Fig. 6. SEM micrographs of the surface of the fabric infiltrated with an alkaline CTAB-dispersed suspension(c) SiC suspension(a and b: different magnificationsS. Novak et al. / Journal of the European Ceramic Society 28 (2008) 2801–2807 2805 in this study were seen to be negatively charged (Fig. 4, open square symbols) exhibiting similar behaviour to the SiC pow￾der (see Fig. 1). The fibres were then treated with the anionic surfactant SDOSS in order to improve the wetting with aqueous slurries, which also resulted in a slight increase in the negative ZP value (Fig. 4, close square symbols). The SiC-fibre fabric was first used as a deposition electrode, but no deposit was formed within 5 min. The current during the deposition was very low, probably due to the conductivity of the fibres being too low. Then, one or several layers of the fabric were placed in front of the steel electrode, so that the particles were forced to travel through the fabric towards the electrode. In order to prevent the formation of bubbles in the deposit a membrane was placed in front of the fabric at the cathode or, in the case of negatively charged particles, a copper electrode Fig. 5. Optical micrographs of the starting fibre fabric (a), the fabric infiltrated with a TMAH-dispersed SiC suspension (b) and the fabric infiltrated with the CTAB-dispersed suspension (c). was used as the anode. The infiltrated green samples were dried slowly and examined with an optical microscope. Further they were vacuum infiltrated with a resin and examined by SEM to estimate the success of the infiltration. Fig. 5a illustrates the as-received SiC-fibre fabric before infiltration, while Fig. 5b and c show the surfaces of the fab￾rics electrophoretically infiltrated with negatively or positively charged SiC particles, respectively. In the first case the fibres were pre-treated with SDOSS. In this case most of the large voids between the fibre tows were filled and the particles homo￾geneously coated the surface of the fabric (Fig. 5b), while the positively charged suspension seems to flocculate on contact with the negatively charged fibres. SEM observations (Fig. 6a and b) suggest that in the case of positively charged particles, they attach themselves to the fibres rather than entering the fibre tows interspaces. This is in agreement with a previously pro￾posed mechanism for particle infiltration of fibrous substrates by EPD, which indicates that a more efficient infiltration can be achieved by using equal-sign charges of the fibres and particles rather than using opposite charges.24 A low-angle cross-section of a green part prepared with a negatively charged suspension, infiltrated with a polymer and carefully polished, was also observed by means of SEM, as shown in Fig. 7, taking special care to distinguish the SiC-infiltrated parts (the light phase in Fig. 7a) from the polymer￾infiltrated parts (dark areas in Fig. 7a, see the arrows). As illustrated in Fig. 7b and c, which show the light areas, SiC particles have effectively filled the narrow gaps between the Fig. 6. SEM micrographs of the surface of the fabric infiltrated with an alkaline SiC suspension (a and b: different magnifications)