Abstract

Energy saving methods arise from two main routes: efficiency and conservation. The former reduces the energy required to perform a task, whereas the latter comprises all actions to reduce the losses. For high temperature processes, heat conduction is mostly carried out by radiation in the infrared range (0.7 to 100 µm). Therefore, a good thermal insulating material for high temperature application must be able to reduce the radiation intensity within the temperature of interest. Porous refractory ceramics with tailored amount and size of pores are candidates to be applied for this purpose. Considering the different routes of processing porous ceramics, the direct foaming method results in materials with reproducible properties, narrow distribution of pore sizes and suitable mechanical strength. Nevertheless, physical effects as coalescence and drainage can take place in the liquid foam, reducing its stability and increasing the bubbles’ size. There are two ways to control this phenomena: adding surfactants that act on the bubble’s surface tension or using binders that induce the fast transition from the liquid to solid foam. In this work, aluminous foams were prepared by the direct foaming method using different inorganic binder systems and setting additives. Their microstructure, porosity, thermal conductivity and mechanical strength, were evaluated. The results pointed out that the foam microstructure was modified when different binder systems were used, influencing the mechanical and thermal properties of the material. Based on these results, the selection of the binder system has been shown as an important factor to process porous material with tailored properties.