Mullite Formation in Al_2O_3/SiO_2/SiC Composites for Processing Porous Radiant Burners

摘要

Use of porous ceramic burners for natural gas combustion is an optimum alternative to enhance energy efficiency and decrease emission of pollutant gases per generated power. Materials requirements for the operation of such porous burners are mainly thermal shock and chemical resistance and those can be reached with cellular ceramics. Mullite was theoretically identified among the best materials for this application; however, its potential was not properly explored yet. Even though mullite can be synthesized from different compounds and processing routes, control of final material characteristics is complicated mainly due to the formation of amorphous phase. In this work, using a technological approach mullite burners were processed by the replication method starting from different mixtures of Al_2O_3/SiO_2/SiC. Rheological study of the slurries has given additives content for the coating of the polyurethane sponges. After varying sintering temperatures up to 1600 ℃ and isotherm times for 12 h, microstructural aspects and product phases of the final composites were characterized in order to understand the influence of Al_2O_3/SiO_2/SiC ratios in the formation of mullite phase and amorphous content.