Production of complex microchanneled parts of ZrB2-MoSi2 ultra-high temperature ceramics by freeze casting and pressureless spark plasma sintering

A novel approach for manufacturing complex parts of ultra-high-temperature ceramics (UHTCs) is proposed, combining freeze casting with pressureless spark plasma sintering (SPS). With the aid of MoSi₂ sintering additive (15 vol% or more), this combination enables the production of fully dense ZrB₂-based UHTC parts at 1900 °C. Producing complex-shaped samples including an intricate network of internal microchannels seems feasible, by using additive manufacturing techniques in the production of templates for the external silicone mould and the internal microchannel network to be used during the freeze casting process. Although defects are prone to occur either during freeze drying, due to thermal stresses arising from the expansion mismatch between the internal resin template and the ceramic preform, or during the resin burn-out or SPS cycles, the resulting samples exhibited a fully dense microstructure and similar hardness (17 ± 1 GPa) as the bulk material. Thus, the proposed approach shows promise in the production of arbitrarily complex-shaped UHTC parts that may find application in numerous industrial sectors including aerospace, aviation, and energy generation and storage.