Bioinspired PcBN/hBN fibrous monolithic ceramic: High-temperature crack resistance responses and self-lubricating performances

Abstract

The high strength and toughness of natural materials are mainly determined by a combination of mechanisms operating at different length scales, which can be used as a strategy to reduce the intrinsic brittleness of ceramics. Inspired by the architectures of bamboo, the polycrystalline cubic boron nitride/hexagonal boron nitride (PcBN/hBN) fibrous monolithic ceramics with a long fiber arrangement structure was constructed with PcBN fiber cells and hBN cell boundaries, and its crack resistance responses and tribological performances were investigated. The composite ceramic failed in a non-brittle manner with the rising resistance curve (R-curve) behavior, which was attributed to multiscale crack effects in the hierarchical architecture. The maximum crack growth toughness was extremely high (approximately 21 MPa·m1/2), corresponding to a 270% increase over the crack initiation toughness. Excellent fracture resistance could be retained even above 1000 °C. Moreover, the composite ceramic exhibited low and stable friction coefficients (approximately 0.33) when paired with a Si3N4 pin at high temperature (1000 °C), owing to the lubrication function of hBN cell boundaries with weak van der Waals forces and a small amount of liquid B2O3 produced. As a result, a synergistic improvement of mechanical and tribological properties at high temperature (1000 °C) was realized by combining bionic structure and tribological design. It provides important theoretical and technical support for expanding the application of self-lubricating composite ceramics in harsh environments.

High damage tolerant Al2O3 composite ceramics constructed with short Al2O3 fibers

“…The crack growth resistances in standard valid and invalid were attributed to small-scale and largescale cracking effects, respectively. 18 While the reference Al 2 O 3 ceramic lacked the crack propagation resistance behavior and energy dissipation mechanism, its fracture toughness was about 4.26 ± 0.58 MPa⋅m 1/2 without any ascending characteristics. Thus, these composite ceramics possessed multiscale extrinsic toughening characteristics and exhibited excellent mechanical properties and service reliability.…”

“…The stress-strain curves and R-curves of the various composites are shown in Figure 3, which were calculated from the initial load-displacement curves obtained from SENB tests and the J-integral method, respectively. 18,19 The stress-strain curves (Figure 3A) illustrate that the reference Al 2 O 3 ceramic showed a purely linear elastic response until catastrophic failure occurred, which was a typical catastrophic fracture behavior. By contrast, the stress-strain curves of the as-prepared samples exhibited considerable carrying capability remaining after the first decrease of the stress, which enabled the composite ceramics to have a greater strain.…”

Cuttlefish-Bone-Structure-like Lamellar Porous Fiber-Based Ceramics with Enhanced Mechanical Performances

“…Thus, the lower linear shrinkage in the direction parallel to the X−Y plane mainly benefits from the presence of fibers that have been proven to be effective in resisting deformation. 43,44 On the basis of the SEM images shown in Figures 3 and 4 and Figure S4, the large linear shrinkage of the AS02 product in the direction parallel to the X−Z plane leads to the formation of broken lamellar structures, whereas the relatively low linear shrinkage of other products contributes to forming the continuous and complete lamella structures.…”

“…Then, parts of the cracks in the lamellas stop propagating because of the presence of the fibers as shown in Figure 8d,f, indicating that fibers can toughen the lamellas by inducing the crack deflection. 43,44 Other cracks proceed to propagate, eventually leading to the fracture of the lamella or fiber. Fortunately, because of the presence of the lamellar spacing and abundant unique fiber-bridge structures between the lamellas that can effectively connect adjacent lamellas, the adjacent lamellas near the fractured lamellas still remain intact.…”

Low-temperature and flexible strategy to in-situ fabricate ZrSiO 4-based ceramic composites via doping and tuning solid-state reaction

“…11b). The presence of the debris at the friction interface not only resulted in the formation of more peeling off debris [47], but also aggravated the friction under the action of plough effect [48,49]. Meanwhile, the sizes of the ZrSiO4 and SiO2 grains were a few micrometers and they had an interpenetrating microstructure (Fig.…”