Innovation in ceramic foam filters manufacturing process

Ceramic filters have singular properties such as high permeability and specific surface area associated to low density. Some examples of their use can be found in liquid metal deep filtration, water treatment, air purification, and others. These particular properties are dependent on the filters' manufacturing process. One of the most used techniques to produce filters is the replication method, which provides a tridimensional network of struts and interconnected pores. However, a common issue of all ceramic filters produced by this technique is their low mechanical strength due to the hollow struts and microcracking generated during the thermal decomposition of the sponge. Intending to address this limitation and produce filters with higher mechanical strength, this paper analyzed a modified process route for manufacturing filters. Samples of preheated Al2O3 filters were vacuum infiltrated with ceramic suspensions (Al2O3 and SiO2) of different solids concentrations (15-40 wt%), particle size distribution (nano to micrometric size) at distinct processing times (1-5 minutes). The data analysis indicated that the best balance among mechanical strength, mass, and strut thickness was achieved by infiltration with SiO2 colloidal suspension (40 wt%) per 1 minute. SEM analysis confirmed that the struts were filled and microcracks were sealed with colloidal particles.