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E. Laarz et al / Journal of the European Ceramic Society 21(2001)1027-1035 TiG 1000 Shear Rate [s"] Fig. 5. Steady-shear flow curves of 20 vol. TiN and TiC suspensions in 0.01 M NaCl electrolyte in the range D101 O ALO-10%TiN 口A2Q25%Ti Shear Rate [s] Fig. 6. Steady-shear flow curves of 20 vol. composite suspensions containing 0.5 wt. PAA at pHA9. 3.3. Hot-pressing and microstructure evaluation However, their number decreased with increasing PAA concentration and at 0.5 wt. Paa addition the From TG studies, it was found that PAA was burned- microstructure was homogeneous with almost no out completely at 600oC in an Ar-6% H2 atmosphere. agglomerates(Fig. 7a). This may be related to the effect Accordingly, this temperature was chosen to burn out of pH changes on the colloidal stability of the secondary the organic content prior to sintering Tin phase as discussed in the foregoing section; the After hot-pressing, the TiC and TiN particle compo- higher buffer capacity of the suspension at higher PAA sites were fully densified( Table 3). The amount of PAa concentrations probably reduces the pH change that added was found to be more critical for microstructure induced by addition of the acidic Tin phase. The col- homogeneity of AlO3-TiN composites than for Al2O lodal stability of the secondary TiC phase is not sensi- TiC composites Agglomerates of Tin particles could be tive to pH changes in the alkaline range as indicated detected in the microstructure of Al2O3-TiN composites by rheology measurements (Fig. 5). Accordingly,5,5, 9 $ % " ' ? H A ) M-- 0M: 8 2 ) 2 ) ; 6 72 A ) 0 0 2 0 2 8 ' A -29 2: A 6? 2 C72 ) I 8 ) ) . I ) A ) 8 ) 2 ) ) ' 8 ) ) 6? 2 972 ) ? 2 92 < ) U ' - '2: -2-/ ! ) 8RC0/-2 ? 2 M2 < ) U ' - '2: -29 2: A 8,2 /- ., / - , 0 1 . $ + 2+ 3 +4 5