E Stoll et al. /Joumal of the European Ceramic Society 26(2006 )1567-1576 573 Oxide fibre mat lextel 720 High quality Al,o nd al, o, particles between single fibre Electrophoretic lamination technique particles High-quality intra tow Infiltration achieved by EPD Homogeneous AL,O, matrix between (a) Fig. 8.(a) Schematic diagram depicting the mechanism of interlocking of Al2O3 particles during the lamination process between two electrophoretically infiltrated fibre mats; and (b) SEM micrograph of a sintered multilayer composite sample(1300 C for 1 h)consisting of three fibre mats layers cost in comparison with the standard procedure of infiltrating 4. Discussion single fibre mats in different EPD cycles. As Fig. 9 shows, I intra-tow and inter-tow infiltration has been achieved and 4.1. Mechanism of epd of a 203 particles onto oxide a very compact structure with high fibre volume fraction was fibre mats obtained without the need for subsequent processing steps Moreover, it is seen(Fig. 9) that the gap between adjacent In the following, a phenomenological description is pre- fibre mats is 50 um, which is much smaller than that ob- sented of the mechanism of electrophoretic infiltration of ox- tained in the laminated Matrix-rich ide fibre mats by ceramic particles exhibiting the same surface gions, which are prone to microcracking and microstructural charge polarity, as in the present experiments defects, are thus minimised. It should be also pointed out that As schematised in Fig. 10, it is proposed that the total these samples had a diameter of 10 cm, being therefore the trajectory of the particles before reaching the electrode can largest ceramic composite components fabricated by EPD to be divided in two regions. The first region, namely the"ap date, as far as the authors are aware proaching trajectory", occurs in the suspension at a given Fig9. SEM micrograph of a Nextel M 720 fibre-reinforced alumina matrix composite containing four fibre layers(fibre mats) fabricated by simultaneous electrophoretic deposition. The sample was sintered at 1300.C for 1 hE. Stoll et al. / Journal of the European Ceramic Society 26 (2006) 1567–1576 1573 Fig. 8. (a) Schematic diagram depicting the mechanism of interlocking of Al2O3 particles during the lamination process between two electrophoretically infiltrated fibre mats; and (b) SEM micrograph of a sintered multilayer composite sample (1300 ◦C for 1 h) consisting of three fibre mats layers. cost in comparison with the standard procedure of infiltrating single fibre mats in different EPD cycles. As Fig. 9 shows, full intra-tow and inter-tow infiltration has been achieved and a very compact structure with high fibre volume fraction was obtained without the need for subsequent processing steps. Moreover, it is seen (Fig. 9) that the gap between adjacent fibre mats is ∼50
m, which is much smaller than that ob￾tained in the laminated composites (Fig. 8). Matrix-rich re￾gions, which are prone to microcracking and microstructural defects, are thus minimised. It should be also pointed out that these samples had a diameter of 10 cm, being therefore the largest ceramic composite components fabricated by EPD to date, as far as the authors are aware. 4. Discussion 4.1. Mechanism of EPD of Al2O3 particles onto oxide fibre mats In the following, a phenomenological description is pre￾sented of the mechanism of electrophoretic infiltration of ox￾ide fibre mats by ceramic particles exhibiting the same surface charge polarity, as in the present experiments. As schematised in Fig. 10, it is proposed that the total trajectory of the particles before reaching the electrode can be divided in two regions. The first region, namely the “ap￾proaching trajectory”, occurs in the suspension at a given Fig. 9. SEM micrograph of a NextelTM 720 fibre-reinforced alumina matrix composite containing four fibre layers (fibre mats) fabricated by simultaneous electrophoretic deposition. The sample was sintered at 1300 ◦C for 1 h