10.45 5.6 The SEM images of catalysts with MnO 2 -Co 3 O 4 -CeO 2 loading on cordierite were shown on figure 3.40 and 3.41. At low magnification, the distribution of active phase on substrates was observed. Both catalysts MnO 2 -Co 3 O 4 -CeO 2 /AlCe 0.2 Zr 0.05 O 2 / cordierite (Ca.7) and MnO 2 -Co 3 O 4 -CeO 2 /cordierite (Ca.4) had the substrates covered completely by active phase. Because the mixed oxides were loaded on cordierite from homogeneous solution of Mn, Co and Ce, the surface of catalysts were very porous with many pores. However, the differences between the catalysts with and without supports of two catalysts was noticed at high magnification. When the active phase was impregnated on cordierite directly from solution, there was formation of clusters which had a size of approximately 50 – 200 nm (fig.3.40b). It is difficult to estimate the size of particle which formed cluster when capturing the cluster‟s surface, but when observing the edge of a cluster, particles of about 30 nm gathering to yield cluster (fig. 3.40c). Especially, the particles forming cluster in catalyst using support AlCe 0.2 Zr 0.05 O 2 was smaller than 30 nm, may be just a few nm (fig. 3.41 b and c). The active phase was distributed uniformly on the surface of DD-ACZ (AlCe 0.2 Zr 0.05 O 2 / cordierite), in addition, the cluster was formed with smaller particles and more porous, which made an advantage in increasing contact‟s area between catalyst and exhausted gases. Therefore, the catalyst deposited on AlCe 0.2 Zr 0.05 O 2 /cordierite will be studied further.