Production and characterization of alumina bodies via gelcasting by using pectin

In this study, the physical and mechanical properties of alumina samples formed by the addition of pectin at different ratios were compared. The gel casting process was carried out in non-porous silicone molds. Three point bending strength tests and microstructure analyzes were performed to the dried samples. The dried samples were sintered at 1500 ºC and three point bending strength, porosity determinations and microstructure investigations were performed after sintering. According to the results, it was observed that the amount of CaCl2 which is the gelling agent which started the gelation together with the amount of pectin is also very important. The second series, 0.5% CaCl2, was found produced effectively by gel casting. In these samples, the highest strength value belongs to the sample containing 1.5% pectin and it is 8.61 MPa which is very close to that of the standard body (11 MPa). The physical and mechanical properties of this successful samples after firing were also investigated. When the amount of pectin is increased by more than 1.5% after firing, the open porosity increases and the apparent density values decrease. The highest bending strength was obtained by using %1 pectin. The strength value of this sample was 158 Mpa which is higher than that of standard body (118MPa). It was concluded that increased amount of pectin caused decrease in strength after increasing the porosity after firing. According to the results of microstructure analyzes, it was observed that the middle parts of the pectin containing samples were in a dense, non-porous structure and air bubbles could not be left in the edge regions. This explains the increase in open porosity with the increasing amount of pectin. In addition, for future works, it is thought that air bubble removal can be obtained for higher strength values of samples formed by gel casting with pectin if air bubble removal is done more effectively.