Preparation, mechanical and thermal properties of continuous oxide fiber-reinforced porous composites via hot-press-assisted molding

To address the low processing efficiency of conventional continuous oxide fiber-reinforced porous oxide composites (Al₂O_3f/Oxide), a combined hot-press-assisted molding and slurry impregnation strategy was developed to fabricate AF18/Al₂O₃ and AF18/Al₂O₃-3YSZ composites with a bimodal particle-size matrix via a single impregnation-sintering process. The effects of sintering temperature and 3YSZ addition on matrix grain growth, porosity evolution, and mechanical properties were systematically investigated, as well as high-temperature thermal aging, thermal shock, and three-point bending tests. The incorporation of 3YSZ effectively suppressed matrix grain coarsening and mitigated fiber/matrix interfacial erosion, thereby enhancing composite strength and hardness. At 1300 °C, the AF18/Al₂O₃-3YSZ composite exhibited a low density of 2.62 g/cm³ and a high average flexural strength of 273.53 MPa with a fracture energy of 6673.4 J/m², significantly exceeding that of the AF18/Al₂O₃ composite. The stress-displacement curve displayed a distinct staged failure behavior, reflecting a favorable balance between strength and toughness. After thermal exposure at 1300 °C for 24 h, the flexural strength still reached 270.73 MPa, indicating excellent thermal stability. Owing to improved thermal expansion compatibility, the AF18/Al₂O₃ composite demonstrated superior thermal shock resistance at 1200 °C. Furthermore, both composites exhibited excellent ablation resistance and thermal insulation capability due to their porous architecture and intrinsic oxide stability, highlighting their potential for high-temperature structural applications.