The development of new materials is a key factor in the progress of the environment, medicine, space, or energy industries. To this end, composite materials are being developed to meet the multifunctional properties required in these fields. In particular, ceramics are of great importance because of their chemical inertness and resistance to corrosion and high temperatures, which make them suitable as matrices for new composites. In fact, with the incorporation of graphene-based nanomaterials (GBN) to these advanced ceramics, the composites were expected to attain greater structural stability. Nevertheless, the reinforcing ability of the GBN does not show a clear trend after reviewing many of these studies. Some authors have confirmed that the size and oxidation rate of the nanostructures greatly influence the composite performance. Hence, a deep understanding of the relationship between microstructure and properties would enable to tailor these composites with specific properties for precise applications.

Other two-dimensional inorganic nanomaterials having an analogue structure to graphene (known as inorganic graphene analogues, IGA) have more recently emerged. Among them, 2D hexagonal boron nitride (2D-hBN) has gained relevance as it possesses comparable mechanical properties to those of graphene, but showing some advantages over it, such as its chemical stability up to 800-1000 ºC or its white color. It is expected that new functionalities of the composites can be achieved by incorporating these IGA.

In this work, two-dimensional (2D) nanomaterials have been used as reinforcements in 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP). Owing to the difficulty in achieving a homogeneous distribution of the nanosheets through the matrix, diverse processing routes were addressed. All composites were densified using spark plasma sintering (SPS) to maintain a fine ceramic grain microstructure. For some compositions, a rising crack growth resistance (R-curve) was measured, regardless of the composite processing route. Moreover, low energy homogenization and high-temperature sintering of the composites lead to a decrease in the electrical percolation threshold. All these properties will be related to the composite microstructural features that have been assessed through Raman spectroscopy, scanning and transmission electron microscopy, optical microscopy and X-ray diffraction. Finally, the influence of the environmental humidity on the structural integrity of the composites has also been evaluated by studying the subcritical crack growth and the resistance to low temperature degradation.