International Journal of Applied Ceramic Technology最新文献

This work created a fireproof sandwich structure in which the face sheets were made of expanded vermiculite and expanded perlite-filled geopolymer composites and embedded basalt fiber mats and the core material was rock wool in designing the lightweight and cost-effective fire-resistant structure for steel bridges with excellent retardant and heat-insulating performance. The effects of adding 5%, 10%, 15%, and 20% expanded vermiculite and expanded perlite to the geopolymer on mechanical properties and the thermal conductivity were investigated to obtain the optimized material mixtures for preparing the face-sheets material of the sandwich panel. Then, the fireproof sandwich structures were fabricated and exposed to 800°C for 3 h to study the structural integrity, backfire side temperature, and mass loss ratio. The results indicated that adding 10 wt% expanded vermiculite and 10 wt% expanded perlite to the geopolymer achieved the retention of compressive strength of 66.5% after being exposed to 800°C, and the geopolymer mixtures showed a low thermal conductivity of 0.1942 W/(mK). The TOPSIS evaluation analysis reveals that the proposed fireproof sandwich panel had the highest integrated performance considering the structural weight, insulation properties, and cost. The findings of this work may provide some insights into fireproof and insulating applications in bridge engineering.

A high-entropy rare-earth disilicate (Er_0.25Y_0.25Ho_0.25Yb_0.25)₂Si₂O₇ (hereinafter referred to as (EYHY)₂Si₂O₇) ceramic was synthesized by a heat treatment process combined with spark plasma sintering. According to the experimental results, (EYHY)₂Si₂O₇ presents good phase stability and low thermal conductivity ([1.48–2.35] W∙m⁻¹∙K⁻¹) from room temperature to 1200°C. Its coefficient of thermal expansion is (3.89–5.32) × 10⁻⁶ K⁻¹ from 200 to 1400°C, similar to SiC-based materials ([4.5–5.5] × 10⁻⁶ K⁻¹). Due to the multiple doping effects, (EYHY)₂Si₂O₇ exhibits outstanding corrosion resistance performance in water-vapor corrosion tests. Its weight loss is 1.79 mg/cm² after corrosion at 1600°C for 30 h in the presence of 50% H₂O-50% O₂, which is lower than the corresponding four single components Re₂Si₂O₇ (Er₂Si₂O₇, Y₂Si₂O₇, Ho₂Si₂O₇, and Yb₂Si₂O₇) under the same conditions. Therefore, high-entropy (EYHY)₂Si₂O₇ ceramics are regarded as potential environmental barrier coatings materials for SiC ceramic matrix composites.

Synthesis and consolidation of (Zr,Ti)C were investigated in the present work. ZrC–TiC powder mixture was synthesized at 1650°C for 90 min by the carbothermal method. The prepared powder mixture was hot-pressed at 1800 C for 60 min under a pressure of 40Mpa and then heat-treated at 2100 C for 60 min. There were ZrC-rich and TiC-rich phases together with zirconium oxide phases in powder mixture and hot-pressed samples, while there were no oxide phases in the heat-treated sample and only ZrC-rich and TiC-rich phases were present in the sample. The FESEM image of the fracture surface of the samples shows that the porosity of the samples decreases with increasing temperature. Relative density, microhardness, and flexural strength increased from 93.8% to 98.6%, from 15.26 to 21.41 GPa, and from 185.02 to 220.69 MPa, respectively, with increasing temperatures from 1800 C to 2100 C. In contrast to these properties, the fracture toughness of the samples was reduced from 3.71 to 3.47 MPa·m^1/2. The investigation of oxidation behavior also showed that oxidation is influenced by oxygen diffusion and exhibits nonlinear behavior as a function of time. With increasing oxidation temperature of hot-pressed and heat-treated samples from 600 to 1000°C, parabolic oxidation rate constants (k_p) increased from .267 to 11.793 and from .367 to 10.993, respectively.

Cycloaliphatic epoxides exhibit post-light irradiation heat-induced polymerization, creating warp-resistant green bodies during sintering. However, their use in light polymerization three-dimensional (3D) printing is limited by slow photo-curing speeds. In this study, a photo-cationic polymerizable ceramic slurry was developed for 3D printing by mixing oxetane with cyclo-aliphatic epoxide. This mixture improved photo-curing speed, reduced resin viscosity, and enhanced the ceramic slurry's solid content. Additionally, we optimized the slurry by considering the specific and content ratio of photosensitizers and light absorbers. The optimized slurry polymerized unreacted functional groups in the polymer, improving the fracture strength of the green bodies through enhanced crosslinking density and uniformity in each layer. Ultimately, a sintered body without warpage was produced by the improved green bodies. This approach provides a solution related to controlling the photocuring speed and expands the potential applications of 3D printing in areas where the precision and stability of the printing material are required.

Selective laser flash sintering utilizes a scanning laser as a heat source to locally initiate flash sintering in the regions scanned by the laser. A key challenge towards utilizing this process for additive manufacturing (AM) is the induced electrical current that arises during flash sintering. With traditional scan patterns conducted with static electric fields, electrical and thermal runaway and associated thermal shock cracking occur. In this study, several open-loop control strategies with static and dynamic applied electric fields were utilized to control peak currents. These strategies were shown to be effective in reducing peak currents to below 1.0 µA and reducing the severity of, but not completely eliminating cracking. Alternative strategies are suggested that could lead to complete elimination of cracks.

Ultra–high-temperature ceramics (UHTCs) are valued for their extremely high melting temperatures and resistance to active oxidation. However, their low fracture strengths and the difficulties in shaping them into complex geometries hamper their widespread application. This study aims to fabricate zirconium diboride–silicon carbide (ZrB₂-SiC) composites reinforced with aligned SiC fibers by formulating suspensions containing a preceramic polymer, ZrB₂, and SiC fibers. This study assessed the influence of fiber alignment on electrical and thermal conductivities, as well as on mechanical strength. The results revealed a significant enhancement in thermal conductivity, particularly when the fibers were aligned, effectively doubling it compared with the non-aligned parts. Additionally, increasing the fiber content significantly improved the fracture strength, with composites containing 22.5 vol% fibers reaching fracture strengths over 57 MPa. However, the final values did not meet the theoretical expectations because the porosity in pyrolyzed parts exceeded 10%. Furthermore, the study demonstrated a 10-fold increase in electrical conductivity with fiber alignment compared to that for non-aligned composites. These results highlight the capability of paste extrusion-based additive manufacturing in tailoring ultra–high-temperature ceramic matrix composites (UHTCMCs) with aligned fibers, realizing their suitability for aerospace applications.

Recently, high-entropy perovskites have attracted considerable attention due to their diverse chemical composition and multifunctionality. In this study, the high-entropy approach was employed in a (Bi_0.4Na_0.2K_0.2Ba_0.2)TiO₃ matrix, and Nd³⁺ was introduced to enhance the configurational entropy and modify its dielectric and ferroelectric properties. Notably, despite Nd³⁺ doping, all samples maintained a tetragonal perovskite structure at room temperature. The configurational entropy increased with the Nd³⁺ concentration, consequently leading to a gradual decline in the ferroelectric properties along with the associated temperature (T_m) and maximum dielectric constant (ε_m). The P–E loops of the ceramics also became thinner as P_m and P_r decreased, resulting in a slow decrease in the recoverable energy density (W_rec) and a simultaneous increase in the energy storage efficiency (η). Especially, the energy storage performance reached its peak at an Nd³⁺ concentration of 12 mol%, exhibiting an energy storage efficiency of 85.8% and a recoverable energy storage density of 0.74 J/cm³ at a low electric field of 100 kV/cm. These results highlight the potential of this material for dielectric applications in low electric fields and contribute to the advancement of alternative high-entropy energy storage perovskite ceramics.

Hierarchical porous silicon carbide (SiC) ceramics were fabricated by combining particle-stabilized emulsions and three-dimensional (3D) printing. Direct ink writing (DIW) was used as the 3D printing technique. The formulation for successful printing is discussed in relation to the rheology of the emulsions. The SiC emulsions were able to be printed with a lower storage modulus (G′) and apparent yield shear stress (τ_y) than previously reported SiC ink pastes. The printed and sintered porous SiC ceramics possess a total porosity of 73.7% with an average pore size within the filaments of 2.2 µm in diameter. A hierarchical pore structure that contains pore sizes of about 250 µm, around 1–10 µm and smaller than 0.5 µm can be observed in the microstructure and pore size distribution. The mechanical properties showed a good strength-to-density ratio, and the thermal conductivity was reduced to 4.9 W/m·K. This study provides a new reliable approach for fabricating hierarchical porous SiC ceramics with low thermal conductivity.

The current study investigates the tensile behavior of SiC/SiC minicomposites, focusing on the efficacy of epoxy encapsulation in extracting the intrinsic fiber bundle response. Three minicomposite types were examined: two with Hi-Nicalon Type-S fibers and one with Tyranno ZMI fibers. Tensile tests were performed on minicomposites and fiber tows, both bare and epoxy-encapsulated, whereas interface properties were measured via fiber push-in tests. The results demonstrate that epoxy encapsulation partially mitigates non-uniform loading in minicomposites with discontinuous matrices. Theoretical limits on fiber bundle strength, estimated using micromechanical models based on weakest-link statistics and shear lag theory, are similar to measured encapsulated tow strengths when failure occurs within the elastic regime of the epoxy. In some cases, microstructural defects such as fiber–fiber contacts and debonded coatings play important roles in limiting composite strengths relative to theoretical values. Although encapsulation does not always directly improve properties, it provides useful context for evaluating composite performance and exposing microstructural limitations unaccounted for in idealized models.

LiCoO₂ has become the most widely used cathode material in lithium-ion batteries because of its high capacity and excellent stability. The high-temperature solid-state method is commonly used for the preparation of LiCoO₂. However, this method will produce highly penetrating Li₂O, which causes spall or fracture of the insulating refractory materials in the kiln. In this study, the corrosion resistance of bubble alumina, mullite, and calcium hexaaluminate (CA₆) insulating refractories to LiCoO₂ has been thoroughly investigated. Combining the laboratory-scale interfacial reaction experiments with post-experimental life cycle analysis of industrial insulating refractories, the interaction between the insulating refractory materials and LiCoO₂ after calcination at 900°C for 5 h and the corrosion behavior of LiCoO₂ on different insulating refractory materials following heat treatment at 900°C for 5 h every time and repeated seven times are investigated. The corrosion mechanisms are concluded by analyzing the physicochemical composition and macro- and micromorphology of the three insulating refractory materials before and after corrosion. The results can provide a basis for the use of insulating refractories in the development of lithium batteries.