Ultrafast preparation of dense textured ZrB₂-based ceramics via heavy continuous DC Joule heating and pressing

The preparation of dense ZrB₂-based ceramics typically requires high temperatures and long sintering time, which often result in significant grain coarsening and thus deterioration of mechanical properties. Ultrafast sintering techniques offer a solution to inhibit grain coarsening by reducing the processing time. However, the ultrafast preparation of dense ZrB₂-based ceramics remains a challenge. In this work, we successfully fabricated dense ZrB₂-based ceramics in just a few minutes using heavy continuous direct current (DC) Joule heating and pressing. Notably, the densification rate peaked at 1218 °C, and the densification process was nearly complete at a relatively low temperature of 1500 °C. The application of heavy continuous direct current not only promotes the densification of the ceramics but also enhances the texturization of ZrB₂. This results in optimally aligned ZrB₂ grains that form a three-dimensional bonded skeletal network. These unique microstructures can effectively induce multi-stage fracture surfaces during failure, which helps synergistic strengthening and toughening of the ceramics. The ceramics exhibit remarkable comprehensive mechanical properties, with flexural strength and fracture toughness values reaching 773±114 MPa and 5.88±0.08 MPa·m^1/2, respectively, surpassing those of conventional hot pressed samples. This technique is expected to be applied to other ultra-high temperature ceramics, providing a promising approach for the development of thermal protection materials.