8098 J Mater Sci(2006)41:8093-8100 As the main aim of the present study was the EPD of sic with the ap addition on Sic-fibres in further experiments a bundle of Sic-fibres was placed in the 10 cell as the deposition electrode. Due to its small △pH2 effective surface area, the initial current was only 3 mA. The ph of the 口pH10 with the addition of ap was 2. 8 and the solids content X pH2.8 was 35 wt %. Figure 7 presents the current change during the deposition and the image of the bundle with the deposit. Due to the small quantity of the deposit or the fibres. the weight was not monitored. a visual inspection revealed an apparently relatively firm deposit on the Sic-bundle The Sic bundle with the deposit, composed of nano- Sic powder and AP, was sintered in an inert atmo- HILLH sphere at 1450C. The cross-section of the sintered sample was polished and inspected by SEM, TEM and without AP EDS. The microstructures of the matrix were rather dense with a small amount of closed porosity, and good cohesion between the matrix and the fibres is evident ( Figs. &a and b). Due to a low firing temperature, the 0 1 2 3 4 56 789 10 SiC-particle size remained practically unchanged, i time [min 50 nm(Fig. &c). The EDS spectrum reveals a certain Fig.5 The current during the deposition of um-SiC suspension amount of oxygen in the matrix material, probably with the addition of aluminium phosphate as a function of solids resulting primarily from the oxygen-containing layer content in the starting suspensions(60 V, steel electrode) on the nano-SiC particles. 70 mA, and a significant current drop was observed Conclusions during the deposition (Fig 6a). This could explained by the reduced active surface of the elec- In the present investigation the effect of the compo- trode due to the presence of bubbles. As shown in sition of Sic-based suspensions on EPD was studied Fig 6b, the bubbles were concentrated by the elec- with the aim of establishing the conditions for depo- trode, while the bulk deposit appears rather dense. sition on SiC-fibres. Ethanol suspensions of two Dilution of the suspension with ethanol diminished the different grades of Sic powders, with and without the current, as was also observed for the nano-Sic addition of AP (as a sintering aid), were used for suspension without the AP addition. depositing on steel electrodes Fig. 6(a)-The current change during the depositie a b of the suspension of nano-SiC hosphate as a function of solids content; (b)-image of the inner side of the deposi bubble 1 cm me [min 2 Springer70 mA, and a significant current drop was observed during the deposition (Fig. 6a). This could be explained by the reduced active surface of the elec￾trode due to the presence of bubbles. As shown in Fig. 6b, the bubbles were concentrated by the elec￾trode, while the bulk deposit appears rather dense. Dilution of the suspension with ethanol diminished the current, as was also observed for the nano-SiC suspension without the AP addition. As the main aim of the present study was the EPD of SiC with the AP addition on SiC-fibres, in further experiments a bundle of SiC-fibres was placed in the cell as the deposition electrode. Due to its small effective surface area, the initial current was only 3 mA. The pH of the suspension of nano-SiC powder with the addition of AP was 2.8 and the solids content was 35 wt.%. Figure 7 presents the current change during the deposition and the image of the bundle with the deposit. Due to the small quantity of the deposit on the fibres, the weight was not monitored. A visual inspection revealed an apparently relatively firm deposit on the SiC-bundle. The SiC bundle with the deposit, composed of nano￾SiC powder and AP, was sintered in an inert atmo￾sphere at 1450 C. The cross-section of the sintered sample was polished and inspected by SEM, TEM and EDS. The microstructures of the matrix were rather dense with a small amount of closed porosity, and good cohesion between the matrix and the fibres is evident (Figs. 8a and b). Due to a low firing temperature, the SiC-particle size remained practically unchanged, i.e., 50 nm (Fig. 8c). The EDS spectrum reveals a certain amount of oxygen in the matrix material, probably resulting primarily from the oxygen-containing layer on the nano-SiC particles. Conclusions In the present investigation the effect of the compo￾sition of SiC-based suspensions on EPD was studied with the aim of establishing the conditions for depo￾sition on SiC-fibres. Ethanol suspensions of two different grades of SiC powders, with and without the addition of AP (as a sintering aid), were used for depositing on steel electrodes. 0 1 2 3 4 5 6 7 8 9 10 11 12 02 57 10 time [min] pH 2 pH10 pH2.8 current (mA) without AP 1 3 4 6 8 9 Fig. 5 The current during the deposition of lm-SiC suspension with the addition of aluminium phosphate as a function of solids content in the starting suspensions (60 V, steel electrode) 0 10 20 30 40 50 60 70 80 024 time [min] Current [mA] 50 w.t % 25 wt.% 15 wt. % 1 3 5 1 cm a b Fig. 6 (a) - The current change during the deposition of the suspension of nano-SiC powder and aluminium￾phosphate as a function of solids content; (b) - image of the inner side of the deposit with bubbles 8098 J Mater Sci (2006) 41:8093–8100 123