E Stoll et al. /Joumal of the European Ceramic Society 26(2006 )1567-1576 Stainless stee AKP-50/Al2O3 (Ethanol) (NexrelTM720 SS)substrate Fibre mat(s) strongly ultrasonically fixed to ss substrate EPD EPD of multilayer (single fibre mat (Three or more fibre mats (air, room temperature) nats) T<80C) “滥 more layers of 20 fibre mats (CMC) aau:08 arT<1300°) ar,T<1300°c) CMC Fig. 2. Flow chart describing the two methods developed to produce ceramic matrix composites(CMCs) with alumina matrix and three or more layers of Nextel TM 720 fibre mats as reinforcement a pressureless sintering process was used to densify the ng polyvinylalcohol(PVA)with a-Al2O3 particles and composites. deionised water according to the composition described in Table 1. The paste coating on wet surfaces of fibre mats previously infiltrated by EPD was applied using a Doc 2.3.2. Process 1: EPD of single fibre mats and subsequent lamination tor Blade type method(see Fig 3). The thickness of the Fibre mats of square shape with an effective area for in- peated for three l: oating was between 0.5 and 1 mm. The procedure was re yers and subsequently the composite(green iltration of 45 mm x 45 mm were used. The stable suspen- body) was consolidated, forming a three-layer"sandwich filt sion was incorporated in a typical(standard)electrophoretic packet, by warm-pressing. The application of heat during deposition cell, as the one shown in Fig. 1. Under the application of the external electrical field, the positively pressing was required to reduce the viscosity of the paste and thus to generate better conditions for impregnation and charged Al2O3 particles in the suspension moved towards the oppositely charged electrode, before which the non- conductive Nextel M 720 fibre mat was placed. The elec- Table 1 tric field of 50 V/cm was kept constant for all experiments Composition of the paste used in the lamination procedure for CMCs fabri and the deposition time was 3 min. Electrophoretically in- cation(see Fig 3) filtrated single fibre mats were dried in air at normal pres- Concentration ure and stored at room temperature in dissicators for later Non-ionized water Owt.%c use Owt.%c icaly the lamination process, the procedure shown schemat- Polyvinilalcohol binder( Polyviol LL 6035) 10-20w%of in Fig. 3 was used. A paste was made by mix- (20% solutionE. Stoll et al. / Journal of the European Ceramic Society 26 (2006) 1567–1576 1569 Fig. 2. Flow chart describing the two methods developed to produce ceramic matrix composites (CMCs) with alumina matrix and three or more layers of NextelTM 720 fibre mats as reinforcement. a pressureless sintering process was used to densify the composites. 2.3.2. Process I: EPD of single fibre mats and subsequent lamination Fibre mats of square shape with an effective area for in- filtration of 45 mm × 45 mm were used. The stable suspen￾sion was incorporated in a typical (standard) electrophoretic deposition cell, as the one shown in Fig. 1. Under the application of the external electrical field, the positively charged Al2O3 particles in the suspension moved towards the oppositely charged electrode, before which the non￾conductive NextelTM 720 fibre mat was placed. The elec￾tric field of 50 V/cm was kept constant for all experiments and the deposition time was 3 min. Electrophoretically in- filtrated single fibre mats were dried in air at normal pres￾sure and stored at room temperature in dissicators for later use. For the lamination process, the procedure shown schemat￾ically in Fig. 3 was used. A paste was made by mix￾ing polyvinylalcohol (PVA) with -Al2O3 particles and deionised water according to the composition described in Table 1. The paste coating on wet surfaces of fibre mats previously infiltrated by EPD was applied using a Doc￾tor Blade type method (see Fig. 3). The thickness of the coating was between 0.5 and 1 mm. The procedure was re￾peated for three layers and subsequently the composite (green body) was consolidated, forming a three-layer “sandwich” packet, by warm-pressing. The application of heat during pressing was required to reduce the viscosity of the paste, and thus to generate better conditions for impregnation and Table 1 Composition of the paste used in the lamination procedure for CMCs fabri￾cation (see Fig. 3) Composition of the paste Concentration Non-ionized water 50 wt.% -Al2O3 (AKP-50) powder 50 wt.% Polyvinilalcohol binder (Polyviol LL 6035) (20% solution) 10–20 wt.% of solid content