Mechanical evaluation of DIW-printed carbon nanofibers- alumina-toughened zirconia composites

Direct ink writing (DIW) offers cost-effective fabrication of intricate ceramic structures. However, the mechanical properties (reliability) of DIW-obtained components have been inadequate for structural applications. This study aimed to improve mechanical properties of DIW alumina-toughened zirconia (ATZ) composite filaments with and without carbon nanofibers (CNFs). Optimized debinding and sintering conditions were determined for Conventional Sintering (CS) and Spark Plasma Sintering (SPS). The influence of nozzle diameter, CNF content and sintering method on the fracture strain, Young's modulus, flexural strength and Weibull modulus was carefully assessed via correlation analyses. CNFs, although intended to enhance properties, were often agglomerated, which negatively affected mechanical properties. Smaller nozzle diameters enhanced Young's modulus, with CSsintered ATZ filaments showing transformation-induced plasticity (TRIP). Mechanical properties rivaled or surpassed those of conventional techniques (e.g., cold isostatic pressing, slip casting) with a good level of mechanical reliability achieved. Overall, DIW showed promise for ceramic materials, particularly ductile Ce-TZPbased composites.