Investigation of production parameters in fracture behavior of hot‐pressed Al₂O₃–SiC/graphite fibrous monolithic ceramics: Fibers orientation and cell boundary fraction

Abstract

Fibrous monoliths (FMs) exhibit graceful failure in flexure and have higher toughness values. In this research, a mixture of Al 2 O 3 and SiC as the core and graphite as the shell material of fibers were produced by extrusion-molding technique and after aligning along intended directions (0°, 90°, and 0°/90°) were sintered using the hot-pressing method at the temperature of 1500°C under pressure of 35 MPa for 1 hour. The significance of fibers orientation angle and the cell to cell boundary volume ratio in defining the fracture behavior of the FMs was detected.Because of the extensive crack interactions with graphite cell boundary such as crack deflection and delamination, with increasing cell boundary content from 25 to 30 vol%, the fracture toughness was enhanced. The highest flexural strength (184.8 ± 0.61 MPa) obtained from samples with 0°fibers orientation compared to 0°/90°. Since in the transverse plies (layers with 90°aligning), the properties of matrix phase are dominant, hence the strength in specimens with 0°/90°fibers orientation decreased considerably due to weak graphite matrix phase. In addition, the fracture toughness value increased up to 8.35 ± 0.74 MPa·m 1/2 for the unidirectional architecture of (0°) in comparison with cross-ply (0°/90°) architecture.

Effects of carbon nano-additives on characteristics of TiC ceramics prepared by field-assisted sintering

“…Therefore, other solutions should be taken into account. As two potential replacements for the conventional powder metallurgy technique, many researches have been done on fabricating TiC-based materials using spark plasma sintering (SPS) [16][17][18] or hot pressing (HP) [19,20] routes. The former takes advantage of external pressure over the sintering process through which the densification can be completed at a roughly low sintering temperature within a short dwelling time [21,22].…”

The influence of different SiC amounts on the microstructure, densification, and mechanical properties of hot‐pressed Al2O3‐SiC composites

“…1,2 Al 2 O 3 as one the structural ceramics provides excellent features such as heat, corrosion, and wear resistance and hardness. [5][6][7] It seems that to dominate the intrinsic brittleness of alumina, composition of new materials is necessary. Therefore, it has been widely used in dielectric applications.…”

“…4 However, as to the strong ionic-covalent bonds and the rhombohedral structure, the dislocation movements are restricted and this material proposes a low fracture toughness and strength. [5][6][7] It seems that to dominate the intrinsic brittleness of alumina, composition of new materials is necessary. In this regard, the construction of ceramic matrix composite (CMC) structures by addition of one or more other ingredients into the ceramic material has been found as an efficient procedure to improve the fracture toughness of Al 2 O 3 ceramics.…”