Fracture Behaviors and Ferroelastic Deformation in W/Cr Co‐Doped Bi₄Ti₃O₁₂ Ceramics

Abstract

In this paper, the influence of Cr 2 O 3 additive (y = 0~0.4 wt%) on fracture behaviors, ferroelastic deformation, and mechanical strengths of Bi 4 Ti 2.95 W 0.05 O 12.05 (BTW) Aurivillius ceramics was investigated. For these W/Cr co-doped Bi 4 Ti 3 O 12 ceramics (BTW-yC), SEM analysis on their fractured surfaces demonstrate that the transgranular fracture is the main fracture mechanism, however, the intergranular fracture also exists in the sample at y = 0.3. Impedance analyses based electrical resonance show that their Poisson's ratio and Young's modulus vary with y in a similar trend, while the frequency constant and elastic compliance exhibit a contrary varying trend with y. On the other hand, under the Vickers indentation, the crack propagation in BTW-yC ceramics takes the form of the longstraight extension, small-angle deflection, and short-distance branching at y = 0, 0.2, and 0.4, respectively. In the uniaxial compression tests, the stress-strain behavior of ceramics consist of three stages, i.e., linear elastic deformation, ferroelastic domain switching, and microcrack propagation. The ferroelastic domain switching tends to form the resistance for the microcrack propagation. Furthermore, uniaxial bending tests prove that the fracture strength is dependent on the grain size and fracture toughness, Overall, the sample at y = 0.1 gains a better mechanical strength among BTW-yC ceramics.

Anisotropy of Mechanical Properties in a Hot‐Pressed Boron Carbide

“…19 or crystalline forms at triple-junction points. 12,20 In this BC, graphite-like inclusions were found to be dominant for fracture initiation among the whole population of inclusions and their influence on the dynamic mechanical behavior must be taken into account. Figure 3 shows typical load-displacement curves of the BC (matrix) material and large flake-like carbon inclusions (within the matrix material) collected from experiments performed in the hot-pressing direction and up to 200 mN peak load.…”

“…1,8,9,10 Nonoxide additives, such as free carbon, also improve this process. 10,11,12 However, the more additives in the powder, the larger the probability that secondary phases and/or precipitates will form at the grain boundaries or within the grains. 12,13 If the properties of these inhomogeneities are very different from those of BC, inhomogeneous stress fields will likely develop in the material in response to loading.…”

“…10,11,12 However, the more additives in the powder, the larger the probability that secondary phases and/or precipitates will form at the grain boundaries or within the grains. 12,13 If the properties of these inhomogeneities are very different from those of BC, inhomogeneous stress fields will likely develop in the material in response to loading. Consequently, cracks can originate from these highly stressed regions and lead to massive failure.…”

Ion Doping Effects on the Lattice Distortion and Interlayer Mismatch of Aurivillius-Type Bismuth Titanate Compounds

“…In our previous work [14,15,16,17], we attempted a co-substitution of W 6+ and Cr 3+ for Ti 4+ at the B-site of Bi 4 Ti 3 O 12 . This type of W/Cr co-doped Bi 4 Ti 3 O 12 compound gained many good electrical and mechanical properties in the form of ceramics, becoming a very competitive candidate for high-temperature piezoelectric applications.…”

Effect of the pH of the electrolyte on the formation and on the corrosion properties of ceria based coating on carbon steel

“…For instance, physical, chemical, or electrochemical techniques like simple immersion, anodic or cathodic deposition, PVD, sol-gel, etc., have been reported to successfully elaborate such coatings. [2][3][4][5][6][7][8][9][10][11][12] The final coating is composed of two layers (inner and outer) with different chemistries. While it is established that the outer layer is mainly composed of cerium oxyhydroxides, [13] the chemistry of the inner layer depends on the metal substrate and on the application technique.…”