## 3 Results and Discussions
### Effects of Changes in the Types and Amounts of Binder and Dispersants
Each  
Figure 6: Effects of the addition of a binder (0–1.5 wt.% PVA) on the (**a**) viscosities, (**b**) densities and compressive strength, and the (**c**) pore size distribution of reticulated porous zirconia specimens. dispersant was added in the range of 0-1.5 wt.% to determine the optimal amount in the zirconia slurry. Figure 7a shows the viscosity of the zirconia slurries prepared with 0-1.5 wt.% DARVAN C-N. Particles in the zirconia slurry are dispersed by electric repulsive force by adding DARVAN C-N; thus, as the amount of DARVAN C-N is increased, the viscosity of the zirconia slurry decreases gradually. However, because the distance between the dispersed particles at the same volume is limited, the viscosity did not decrease further, even when an amount of 1.5 wt.% of DARVAN C-N or more was added. The density and compressive strength of the reticulated porous zirconia specimens with different amounts of DARVAN C-N are shown in Figure 7b. In comparison, the density and compressive strength decreased as the amount of DARVAN C-N was increased. These results indicate a decrease in the viscosity in the zirconia slurry upon the addition of DARVAN C-N as a dispersant, with no effect on or increase in the compressive strength. The pore size distributions of the reticulated porous zirconia specimens upon the addition of DARVAN C-N are shown in Figure 7c. Regardless of the amount of DARVAN C-N, it is believed that the pore size distribution ranged from approximately 10 to 100 \(\upmu\)m.  
Figure 7: Effects of the addition of a dispersant (0–1.5 wt.% DARVAN C-N) on the (**a**) viscosities, (**b**) densities and compressive strength outcomes, and the (**c**) pore size distributions of reticulated porous zirconia specimens. To compare the dispersion effect, the authors conducted a study of Dolapix CE 64, which has also been studied in the literature [20]. Figure 8a shows the viscosity of the zirconia slurries prepared with 0-1.5 wt.% of Dolapix CE 64. As the amount of Dolapix CE 64 increased, the viscosity of the zirconia slurry gradually decreased; these results are similar to the results for DARVAN C-N. The density and compressive strength with different amounts of Dolapix CE 64 are shown in Figure 8b. An important aspect here is that a different outcome arose when DARVAN C-N was used. As the amount of Dolapix CE 64 increased, the density remained constant but the compressive strength peaked at 1 wt.% of Dolapix CE 64. In this case, the density makes it difficult to predict the compressive strength. Therefore, the viscosity and pore properties should be analyzed at the same time. The pore size distributions with 0-1.5 wt.% of Dolapix CE 64 are shown in Figure 8c. When 1 wt.% of Dolapix CE 64 was added, the pore size decreased slightly, indicating that the pore size decreased and the compressive strength increased when preparing reticulated porous zirconia with few macro voids of the strut walls under the optimized dispersant condition (in this study, 1 wt.% Dolapix CE 64). When the dispersant was 1.5 wt.% Dolapix CE 64, the pore size was similar to when 1 wt.% Dolapix CE 64 was used, but the density and compressive strength decreased. This result indicates that the viscosity of the zirconia slurry increased again without full penetration into the polymer template, leading to simultaneous reductions in the density and compressive strength. Figure 8: Effects of the addition of a dispersant (0–1.5 wt.% Dolapix CE 64) on the (**a**) viscosities, (**b**) densities and compressive strength outcomes, and the (**c**) pore size distributions of reticulated porous zirconia specimens. Additionally, it was inferred that the addition of Dolapix CE 64 had a stronger effect of dispersing the particles in the zirconia slurry compared to when DARVAN C-N was added. When a dispersant was not added to the zirconia slurry, the viscosity was 101,400 m\(\cdot\)Pas at a shear rate of 0.003.