The linear shrinkage of the alumina ceramic foam filter
The linear shrinkage of the alumina ceramic foam filter is shown in Table1. It can be seen that the linear shrinkage rate of alumina ceramic foam filters is below 1% under different aluminum dihydrogen phosphate content, and the linear shrinkage rate increases slightly with the increase of aluminum dihydrogen phosphate content. Generally speaking, when alumina ceramic foam filters are sintered at a higher temperature (above 1300 ℃), due to the liquid phase sintering and densification process, the linear shrinkage rate of ceramic foam filters is above 10%. In this paper, aluminum dihydrogen phosphate is used as a binder. The ceramic foam filter fired at 800 ℃ did not reach the liquid-phase sintering conditions, and only the pyrolysis products of aluminum dihydrogen phosphate bonded the fused alumina particles, so the linear shrinkage rate was low.
Sintered alumina ceramic foam filters with different contents of aluminum dihydrogen phosphate
The bulk density is shown in Figure 3. It can be seen that the bulk density of alumina foam ceramics increases with the increase of aluminum dihydrogen phosphate content, from 0.79 g/cm3 with 5% aluminum dihydrogen phosphate content in the slurry to 30% aluminum as 1.21 g/cm3 dihydrogen phosphate in the slurry.
Combined with the analysis of Figure 1 and Figure 2, it can be seen that the high content of aluminum dihydrogen phosphate in the slurry makes the slurry have excellent hanging performance and excellent cohesion, which in turn makes the cells and ribs of the foamed ceramics coarser and denser. higher bulk density.
Fig.3 Effect of Al(H2PO4)3 content on volume density
2.3 Flexural strength of the ceramic foam filter
The flexural strengths of fired alumina ceramic foam filter with different contents of aluminum dihydrogen phosphate are shown in Figure 4. It can be seen that when the content of aluminum dihydrogen phosphate is 5%, the flexural strength of the foamed ceramics is 0, indicating that the lower content of aluminum dihydrogen phosphate in the slurry has poor adhesion and cannot bond the alumina particles together. When the content of aluminum dihydrogen phosphate in the slurry is 10%, the flexural strength of the sintered foamed ceramics is 0.61 MPa. When it is 30%, the flexural strength of foamed ceramics is 4.55 MPa. Combining the micro-morphological analysis of Fig. 1 and Fig. 2 and the bulk density analysis of Fig. 3, it can be seen that the high content of aluminum dihydrogen phosphate makes the alumina particles well bonded together, which not only improves the bulk density but also increases the density of aluminum oxide. Mechanical properties of foamed ceramics. The literature uses high-temperature sintering technology to prepare alumina foam ceramics, which have excellent sintering properties of alumina ceramic foams. Based on the excellent performance of the aluminum dihydrogen phosphate low-temperature bonding method, the foam ceramic has application prospects in the field of molten metal filtration.
Fig.4 Effect of Al(H2PO4)3 content on flexural strength