Brittleness reduction of low-carbon Al2O3-C refractories with in-situ formation MgAl2O4/CNTs layer between aggregate and matrix

Abstract

Crack propagation at the aggregate/matrix interfaces of refractories favors their brittleness reduction and better thermal shock resistance. Design of suitable interfaces is highly desirable in refractories. With coating of magnesium citrate and nickel nitrate hexahydrate catalyst on corundum aggregates, a thin MgAl2O4/CNTs interfacial layer of porous structure was formed between aggregate and matrix in low-carbon Al2O3-C refractories. The formation mechanisms of this interfacial layer are pyrolysis of magnesium citrate, reaction with corundum into MgAl2O4 and growth of CNTs. Comparison study of mechanical results shows that this compound interfacial layer contributes to an increase in cold crushing strength, and brittleness reduction assessed with wedge splitting tests. The 3-times water quenching tests testified that brittleness reduction brings about a mild loss of cold modulus of rupture. The results support the conclusion that aggregate/matrix interface design is an effective method to reducing the brittleness and eventually improving the thermal shock resistance of refractories.