Microstructure and mechanical properties of acicular mullite

Porous acicular mullite (ACM) ceramics are known to be mechanically robust even at high porosities. This study was undertaken to better understand what aspects of acicular mulliteʹs needle-like microstructure affect the overall mechanical properties and how the microstructure might be modified to improve mechanical performance. ACMs with a variety of porosities, pore sizes, and needle diameters were produced, and their elastic moduli, flexure strengths, and fracture toughnesses were measured. Three-dimensional image analysis was an invaluable tool in determining the needle diameters of these complex 3D network structures. It was found that porosity was the most dominant factor in determining the mechanical properties of ACM and that its behavior could be described using the Gibson–Ashby foam model.