Influence of aggregate granulometry on the thermal shock resistance of high alumina refractory

ABSTRACT

Alumina refractories are constantly subject to abrupt temperature variations and to high mechanical stresses. In this context, the search for solutions that prevent or reduce the degradation of refractories from industrial processes. The alumina-mullite-zirconia refractory materials exhibit excellent thermal shock resistance and enable high performance in wear and corrosion applications. In this work, we evaluated high-alumina refractories with 5.0 wt.% of nanometric zirconia, verifying the influence of the granulometry of the mullite aggregates, kept at 20 wt.%. Mullite aggregates up to 1 mm and fines of the order of 75 μm were separately used, partially replacing the alumina, and the specimens were sintered at 1600 °C for 5 h. We use scanning electron microscopy and X-ray diffraction techniques to identify the phases present. The fracture energy was evaluated using a three-point bending test, while the resistance to thermal shock damage using a thermal gradient of 800 °C for samples submitted up to fifteen thermal cycles combined with bending tests. The composition containing fine mullite and agglomerated zirconia aggregate provides higher fracture energy than the refractory, however, the aggregate with coarse particle size tends to offer good resistance to thermal shock damage due to the presence of lateral porosity to the aggregates.

Keywords
Mullite; Granulometry; Thermal shock; Damage; Fracture energy