Ceramics Testing

Bertrand, Pierre, et al. Journal of the European Ceramic Society 45.2 (2025): 116886.

This study explores the interface fracture energy between SiC/SiC Ceramic Matrix Composites (CMC) and environmental barrier coatings (EBCs), utilizing a four-point flexural test without precracking. The method enables stable crack propagation along the interface, offering a straightforward approach for specimen preparation and testing. The propagation of cracks was monitored through visible light cameras, and digital image correlation was used to correlate experimental results with numerical simulations.

The use of finite element-based stereocorrelation proved crucial for identifying crack tips and assessing crack length during testing. The correlation between experimental displacement fields and simulations provided a robust way to quantify crack lengths, which was validated at a global scale with good experimental-numerical agreement. The critical energy release rate (Gc) was computed during crack propagation, aligning well with values in the literature. However, uncertainties in crack tip positions and boundary conditions influenced Gc values, which were quantified through this method.

The study demonstrates the effectiveness of this technique in evaluating fracture energy in ceramics, especially in the context of multiple crack initiation. It also highlights the importance of accounting for dissipative phenomena like microdamage in the CMC substrate, which were not captured in simulations. The proposed method is adaptable to various loading conditions and can be extended to different ceramics applications, providing valuable insights into material performance under stress.

Sun, Jialin, et al. Journal of Materials Research and Technology 29 (2024): 1313-1320.

This study investigates the enhancement of binderless tungsten carbide (WC) ceramics, which exhibit superior wear, oxidation, and corrosion resistance but suffer from poor sinterability and brittleness. To address these issues, the effects of hybrid ceramic and oxide binders, SiC whiskers, and graphene on densification, microstructure evolution, and mechanical properties were explored through two-step spark plasma sintering.

The results demonstrate that the combination of ceramic binders and SiC whiskers significantly improved WC densification, while graphene served as an optimal reinforcement for WC-SiC whisker-based nanocomposites. The optimal formulation (SG0.15) achieved remarkable mechanical properties, including a hardness of 23.21 GPa, a flexural strength of 1207.2 MPa, and a fracture toughness of 10.66 MPa•m^1/2. Additionally, the harmful W₂C phase was eliminated in the WC-SiCw-GPL composites.

The key toughening mechanisms identified were SiC whisker pullout, crack deflection, and graphene-based crack bridging. Furthermore, the study showed that lower SiC whisker concentrations resulted in significant grain growth, while higher concentrations inhibited grain growth, providing a balanced approach for improved material properties.

This research offers valuable insights into the development of high-performance binderless tungsten carbide ceramics, presenting a promising strategy for advancing their application in extreme conditions, particularly where wear resistance and toughness are critical.

Şabikoglu, İsrafil. Advanced Powder Technology 33.8 (2022): 103685.

This study explores the synthesis and luminescence properties of Samarium (Sm³⁺) doped lithium metasilicate (Li₂SiO₃) ceramics. The Li₂SiO₃ compound, synthesized through a solid-state method, exhibits a glassy ceramic structure with an orthorhombic phase confirmed by X-ray diffraction (XRD). The impact of Sm³⁺ doping on the crystal structure was minimal, as it did not significantly alter the basic framework of the material.

The optical properties were characterized by photoluminescence (PL) and radioluminescence (RL) measurements. The maximum PL emission for Sm³⁺ doped Li₂SiO₃ was observed at 554, 583, 641, and 725 nm, which aligns with the visible spectrum. RL spectra revealed a wide peak between 400 and 600 nm, attributed to the silicate host matrix. Both doped and undoped Li₂SiO₃ samples showed similar electronic transitions in absorption and PL spectra.

The study highlights the potential for Li₂SiO₃:Sm³⁺ ceramics in luminescent applications. The results were comparable to similar studies; however, further improvements in synthesis temperature and doping ratios are suggested for enhanced optical performance. Conducting measurements at lower temperatures would also help achieve more accurate PL and RL data, paving the way for optimizing the ceramic material for various luminescent applications.