Micromechanical properties of Al2O3–C refractories with aggregate/matrix interfacial layer by nanoindentation

The mechanical properties at microlevels are of important meaning for refractories while determining these values is of great challenges. In this contribution, a tailored grid nanoindentation test was employed to determine the micromechanical properties of low-carbon Al₂O₃–C refractories featuring reduced brittleness with in situ magnesium aluminate spinel/carbon nanotubes (MgAl₂O₄/CNTs) compound interfacial layer between the aggregate and matrix. The micromechanical properties, especially Young's modulus (E) and specific fracture energy (G_c) of the aggregate, matrix, and aggregate/matrix interface area of the refractories, were determined and compared. Statistical analysis on the nanoindentation results of the aggregate and matrix in the reference sample and the sample with interfacial layer shows high consistency, which reveals the high feasibility of the method. The median microspecific fracture energy of the aggregate/matrix interface increases from 63.67 J m⁻² of the reference group to 132.90 J m⁻² of the sample with the compound interfacial layer, which means that higher energy is needed for the initiation and propagation of microcracks within the interfacial layer, accounting for the brittleness reduction of the refractories. Consistent conclusions were drawn from the nanoindentation test at microlevels along with the macrolevel thermal shock test and wedge splitting test.