Refractory properties of the alumina obtained by chemical synthesis

Full text: This work evaluated the thermal conductivity of compact alumina bodies sintered from two different methods of sintering, Microwave and conventional system. Thereunto, ceramic particles consisting of Al₂O₃ were synthesized using different methodologies. Among them, including Pechini, co-precipitation and mixed method with co-precipitation and freeze-drying. Among the main differences observed is the porosity, characterized by SEM method. In the TEM and XRD, it was possible to see the size and morphology of the nanoparticles. The results show that the calcined at 700 ° C resulted in the gamma phase. The alumina calcined at 1100 ° C showed the alpha phase by the Pechini method. While the mixed method with co-precipitation and freeze-drying still maintained gamma phase. Already by TEM and dilatometry analysis, we note that the method co-precipitation presents higher porosity, while the other methods are more densification. The DTA analysis show the decomposition steps in the synthesis that was associated to thermal properties of the sintered discs samples obtained by the Laser Flash analysis. The expansion coefficients were determined for commercial sintered alumina and our sample under 39% of porosity as 15 to 40K W.m-1.K-1 and K=0.183 to K=0.561K W.m-1.K-1 respectively. The shrinkage was from 10 to 14% indicating that disks of Al₂O₃ has great potential applications as refractory material. The laser flash characterization show that this material have very low conductivity and potential for aerospace materials application. (author)