| Direct synthesis of porous calcium-hexaluminate aggregate for refractory applications |
| Hyeon-Mo Bae1, Ayman Muhammad Tsabit1, Sung-Soo Ryu2, Dang-Hyok Yoon1 |
1School of Materials Science and Engineering, Yeungnam University, Gyeongsan, 38541, South Korea
2Engineering Ceramic Center, Korea Institute of Ceramic Engineering and Technology, Icheon, 17303, South Korea |
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Received: May 4, 2023; Revised: October 22, 2023 Accepted: November 21, 2023. Published online: December 6, 2023. |
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| ABSTRACT |
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The synthesis of macro-porous calcium-hexaluminate (CaO∙6Al2O3, CA6) aggregates composed of CA6 platelets was examined using various Ca- and Al-precursors. The effects of annealing temperature, time, atmosphere, and AlF3 as a mineralizer on the formation of plate-shaped CA6 were also studied. The Ca:Al ratio was adjusted for full conversion to CA6, which is the most stable phase among the CaO-Al2O3 intermediate compounds. The conditions for the synthesis of plate-shaped CA6 aggregates with adequate strength were uncompromising, requiring heat treatment at ≥ 1500 °C for 15 h, which was also significantly affected by the type and size of the precursors. CA6 aggregate synthesized directly using coarse Al2O3 and CaO with 10 wt% CaO∙Al2O3 cement as a binder phase revealed the optimal macro-porous microstructure for castable refractory applications, showing porosity and compressive strength of 65% and 2.9 MPa, respectively. |
| Key words:
Calcium hexaluminate · Cement · Refractory · Porosity · Microstructure |
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