Solar sintering of cordierite-based ceramics at low temperatures

Solar furnaces allow materials processing at much higher heating and/or cooling rates compared with those in the conventional industrial and laboratory processes using electric furnaces. During the course of our recent works using solar furnace, we demonstrated usability of solar furnace for sintering-consolidation of oxide ceramics (alumina) and non-oxide ceramics (WC with Co additive) as well as for producing raw material powders including carbide and carbonitride of transition metals and silicon. Being encouraged by these earlier solar-consolidation experiment results obtained for ceramics with relatively simple composition, we decided to continue this line of solar-sintering experiments for other industrial ceramics with more complicated composition. In this work, two types of commercial ceramic powder mixtures, BL7 and RP7, supplied by Rauschert Portuguesa Lda, were subjected to sintering under concentrated solar beam at 950 °C for 20 min. No evidence of formation of cordierite (2MgO · 2Al2O3 · 5SiO2) phase was detected for the present solar sintered specimens whereas evidence of cordierite phase formation was detected for the RP7 powders heated to 950 °C in a laboratory electric furnace. As such, the present results implied that, for the preparation of consolidated cordierite using solar furnace, control over the heating rate is of critical importance as well as selection of the starting materials and setting of the processing temperature.