Spark plasma sintering and hot pressing of ZrB2–MoSi2 ultra-high-temperature ceramics

ZrB2 + 15 vol.% MoSi2 composites were densified by spark plasma sintering and conventional hot pressing at the same sintering conditions, i.e. maximum temperature: 1750 °C, applied pressure: 30 MPa and heating rate: 100–150 K/min. The densification behaviour was investigated through the analysis of the hot pressing and spark plasma sintering shrinkage curves. The microstructures were analyzed and compared in order to understand the influence of the two sintering techniques. The following mechanical properties were measured: Vickers hardness, fracture toughness, Young's modulus and 4-pt bending strength. The main outcome of the present work is that when the ZrB2-based composite was densified either by spark plasma sintering or by hot pressing using the same sintering parameters, no differences were observed in terms of microstructural features and mechanical properties.