Reduced Cracking in Oxide Fiber‐Reinforced Oxide Composites via Freeze‐Dry Processing

Porous oxide matrix composites typically develop significant numbers of matrix cracks during processing. Eliminating such cracks will lead to improved matrix‐dominated properties and will also provide a significant step toward producing a dense oxide matrix composite. However, attaining a crack‐free oxide matrix composite has been elusive due to the large shrinkages of the matrix in drying and sintering in the presence of the constraints to macro shrinkage imposed by fiber reinforcement, and to direct effects of drying. By utilizing a camphene based freeze‐drying process combined with a nonshrinking matrix, the shrinkage cracks in an oxide fiber‐reinforced composite can be essentially eliminated. This concept was validated for 2D fabric‐reinforced composites.