Increasing the tensile strength of oxide ceramic matrix mini‐composites by two‐step sintering

Abstract

Adapting conventional sintering (CS) techniques of monolithic ceramics for the production of oxide ceramic matrix composites (Ox-CMCs) comes along with a few drawbacks, such as fiber degradation. Thus, the applicability of two-step sintering (TSS) for the production of Ox-CMCs based on Nextel™ 610 fibers and porous alumina matrix is investigated in this study for the first time. Uniaxial tensile tests were performed to evaluate the performance of mini-composites produced by TSS and compared with those produced by CS. Parameters known for influencing the mechanical behavior of the mini-composites, such as grain size, porosity, shrinkage, as well as matrix properties, were analyzed. Both sintering techniques resulted in similar grain size distributions, whereas TSS showed higher total porosity and lower amount of sintering-induced cracks. As a result, TSS samples showed a higher tensile strength of 230±27 MPa when compared to 133±8 MPa for CS. In general, it was observed that most of the densification happens during the first phase of TSS, while the matrix is slowly strengthened during the second step. Therefore, the reported TSS process is a very promising and easy-to-apply heat treatment for producing Ox-CMCs with controlled microstructure.

Slurry infiltration and sintering cycle‐dependent mechanical properties of 3D oxide/oxide ceramic matrix composites

“…The fracture toughness slightly decreased from 12.5 ± .7 MPa m 1/2 (the C3 composite) to 10.3 ± .8 MPa m 1/2 (the C9 composite), as shown in Figure 5b. The oxide/oxide composites had much higher fracture toughness than those of monolithic oxide ceramics 35 and the 2D oxide/oxide composites 31,34 . The fracture toughness, which is commonly used for brittle materials like monolithic ceramic, presents some limitations in the ceramic matrix composites 25 .…”

“…Thermodynamically, there was no interfacial reaction between the fiber and the matrix. The enhanced interfacial bonding was due to two reasons: (i) thermal residual stress between the fiber and matrix after sintering 34 ; and (ii) the matrix sintering formed much more contact points with the fiber, as evidenced in Figure 1c,f,i. The SIS cycles led to strengthening of both the matrix and fiber/matrix interface.…”

“…The oxide/oxide composites had much higher fracture toughness than those of monolithic oxide ceramics 35 and the 2D oxide/oxide composites. 31,34 The fracture toughness, which is commonly used for brittle materials like monolithic ceramic, presents some limitations in the ceramic matrix composites. 25 The extrinsic toughening mechanisms of the ceramic matrix composites result from the continuous fibers rather than brittle ceramic matrix.…”

Effects of the Sintering Process on Al2O3 Composite Ceramics Fabricated Using Material Extrusion and Photo-Polymerization Combined Process

“…As ceramic fabrication technology develops, two-step sintering (TSS) is adopted to control the sintering rate and achieve the density and refinement of ceramics [13][14][15] to improve their mechanical properties [16,17]. Generally, the first step of sintering to the maximum temperature is recorded as T 1 .…”