T.. Wong et al. /Journal of Materials Processing Technology 63(1997)399-404 k Fig. 4. Scanning electron micrographs of fracture surfaces of the compression moulded bars prepared by mixing route 1, (a)5 vol% SiCw,(b)15 vol% SiCw, and (c)30 vol% SiC can be seen in all samples. Moreover, further investigation on Table 5. The average weight percentage of ceramic constituents the fracture surfaces which had the same whisker volume in the injection moulded bars with 0, 5, 15, and 30 vol SiCw fraction showed that there was no noticeable differences in are 83.83, 83.91, 84.94 and 85.30 wt% respectively. The whisker content. It is clear that mixing route 2 provided largest deviation from the expected value 85 wt% of ceramic better whisker dispersion than that of mixing route 1 constituents is 1. 17 wt % So, the weight composition of the The wetting and dispersion of the powder into the binder can ceramic constituents can be maintained during the whole be improved by reducing the contact angle and hence lowering fabrication process which includes twin-screw compounding and the surface energy of the powder/binder interface. Stearic acid injection moulding is a typical surfactant or wetting agent for such purpose. In mixing route 2, stearic acid was used to treat the ceramic 3. 3. Wear of processing equipment wder/whisker mixture. As a result, mixing route 2 provide a better whiskers dispersion structure than that in mixing route The variation of Fe content with Sic content in the I and hence it was chosen for the mixing route prior to the ceramics/polymer blends are shown in Fig. 5. The Fe content compounding of the ceramic/polymer mixtures present in the ceramics/polymer blends after compounding and after injection moulding are shown in the same graph for amic weight lost mples after compounding(curve A in Fig 5)were found to have a higher Fe content in the A/p blend (i.e The weight percentages of the ceramic constituents(alumina no SiCw present)than expected. This is because in extruding and SiCw)in each sample from the ashing results are shown in the a/P blend, a 3 mm diameter die was used. However, the402 T.£. Wong et al. I Journal of Materials Processing Technology 63 (1997) 399-404 (a) (b) (c) Fig. 4. Scanning electron micrographs of fracture surfaces of the compression moulded bars prepared by mixing route I, (a) 5 vol% SiCw ' (b) 15 vol% SiCw ' and (c) 30 vol% SiCw • can be seen in all samples. Moreover, further investigation on the fracture surfaces which had the same whisker volume fraction showed that there was no noticeable differences in whisker content. It is clear that mixing route 2 provided a better whisker dispersion than that of mixing route I. The wetting and dispersion of the powder into the binder can be improved by reducing the contact angle and hence lowering the surface energy of the powder/binder interface. Stearic acid is a typical surfactant or wetting agent for such purpose. In mixing route 2, stearic acid was used to treat the ceramic powder/whisker mixture. As a result, mixing route 2 provided a better whiskers dispersion structure than that in mixing route I and hence it was chosen for the mixing route prior to the compounding of the ceramic/polymer mixtures. 3.2. Ceramic weight lost The weight percentages of the ceramic constituents (alumina and SiCw) in each sample from the ashing results are shown in Table 5. The average weight percentage of ceramic constituents in the injection moulded bars with 0, 5, 15, and 30 vol% SiCw are 83.83, 83.91, 84.94 and 85.30 wt% respectively. The largest deviation from the expected value 85 wt% of ceramic constituents is 1.17 wt%. So, the weight composition of the ceramic constituents can be maintained during the whole fabrication process which includes twin-screw compounding and injection moulding. 3.3. Wear ojprocessing equipment The variation of Fe content with SiCw content in the ceramics/polymer blends are shown in Fig. 5. The Fe content present in the ceramics/polymer blends after compounding and after injection moulding are shown in the same graph for comparison. The samples after compounding (curve A in Fig. 5) were found to have a higher Fe content in the A/P blend (i.e. no SiCw present) than expected. This is because in extruding the A/P blend, a 3 rom diameter die was used. However, the