Optimized microstructure with alumina micropowder and its effects on properties of phosphate-bonded castables

Several phosphate-bonded castables were prepared using corundum as a raw material and 48 wt.% phosphoric acid as a binder. The phase composition, microstructural evolution, and properties of the castables samples were analyzed, and a relationship between the microstructures and properties of the castables was established. The results revealed that the cold modulus of rupture of the specimens increased by 19 % to 33.02 MPa after firing at 1 100 °C when the alumina micropowder content increased from 10 % to 15 %. X-ray diffraction analysis revealed that corundum and AlPO4 were present in the castables fired at both 1 100 °C and 1 500 °C. The intensities of the AlPO4 diffraction peaks increased as the alumina micropowder content and sintering temperature increased. Scanning electron microscopy revealed that AlPO4 was tightly arranged and packed with particles.