Freeze casting for near‐net‐shaping of dense zirconium diboride ceramics

摘要: Zirconium diboride (ZrB2) was formed into dense complex shapes using freeze casting as a near-net-shaping technique. Aqueous-based formulations were compared with nonaqueous (cyclohexane) based in terms of rheological behavior, particle packing the green body, sintered density, macroscale porosity, and cracking. The influence solids concentration freezing rate investigated. aqueous found to be deficient that they produced porosity could not eliminated during sintering resulting low density large pores final shaped objects. nonaqueous-based system able produce objects significantly reduced porosity. higher primarily responsible for enabled densities (up 90%-91.5% theoretical fast freezing). microstructure ZrB2 at rates high content typically had isolated order 5-10 μm size, mainly along grain boundaries (grain sizes between 20 50 μm). Although this rapid denser components, it tended internal cracks. When slower used, intricate without cracks but their only 65% 80% density.