Energy saving methods arise from two main routes: efficiencyand conservation. The former reduces the energy required toperform a task, whereas the latter comprises all actions to reducethe losses. For high temperature processes, heat conduction ismostly carried out by radiation in the infrared range (0.7 to 100μm). Therefore, a good thermal insulating material for hightemperature application must be able to reduce the radiationintensity within the temperature of interest. Porous refractoryceramics with tailored amount and size of pores are candidatesto be applied for this purpose. Considering the different routesof processing porous ceramics, the direct foaming methodresults in materials with reproducible properties, narrowdistribution of pore sizes and suitable mechanical strength.Nevertheless, physical effects as coalescence and drainage cantake place in the liquid foam, reducing its stability andincreasing the bubbles' size. There are two ways to control thisphenomena: adding surfactants that act on the bubble's surfacetension or using binders that induce the fast transition from theliquid to solid foam. In this work, aluminous foams wereprepared by the direct foaming method using different inorganicbinder systems and setting additives. Their microstructure,porosity, thermal conductivity and mechanical strength, wereevaluated. The results pointed out that the foam microstructurewas modified when different binder systems were used,influencing the mechanical and thermal properties of thematerial. Based on these results, the selection of the bindersystem has been shown an important factor to process porousmaterial with tailored properties.
展开▼
