International Journal of Applied Ceramic Technology最新文献

Cariri Stone is a type of limestone extensively quarried in the region of Cariri, Ceará (Brazil). However, its extraction process generates large volumes of waste—up to 70% of the total extracted material—which is often disposed of improperly, resulting in significant environmental impacts. This study explored the technical feasibility of incorporating Cariri stone waste (CSW) as an alternative raw material in porous ceramic formulations based on kaolin and alumina. Compositions were developed with CSW content ranging from 10% to 28%. Test specimens were shaped by uniaxial pressing (40 MPa) and subjected to sintering at temperatures of 1100°C, 1150°C, 1200°C, and 1250°C. The sintered specimens were characterized in terms of apparent porosity, bulk density, water absorption, mercury intrusion porosimetry, total porosity, linear shrinkage, and three-point flexural strength. Microstructural aspects and thermal behavior were also evaluated. It was observed that compositions containing 21% and 28% of waste exhibited higher porosity, good dimensional stability, and flexural strength reaching values around 38 MPa. The anorthite was the predominantly crystalline phase. Mullite and gehlenite were also identified. The results demonstrated that CSW has the potential to produce sustainable and innovative porous ceramics with good dimensional stability and mechanical resistance.

The common method to regulate the bonding strength of hydroxyapatite (HAp) coating and metal substrate by adding low-expansion additives usually sacrifices the biological properties of the coating. To avoid the adverse effects of external additives, HAp coating modified by in situ co-substitution with strontium (Sr) and fluoride (F) ions was prepared on the surface of titanium substrates by electrochemical deposition method. The effects of Sr substitution and F substitution on the coating's morphology, hydrophilicity, electrochemical behavior, in vitro bioactivity, biocompatibility, and bonding strength were investigated. Increased Sr substitution promoted bioactivity, while F substitution induced more regular structure and improved electrochemical behavior. All coating samples were hydrophilic and biocompatible. Sr-F co-substituted HAp coating could improve the bonding strength between the coating and substrates and enhance comprehensive biological properties.

Stereolithography-based ceramic additive manufacturing enables the fabrication of intricate monolithic components; however, geometric design freedom remains limited by green-body fragility and sintering-induced deformation in overhanging geometries. To overcome these limitations, this study introduces a dual-mode green-state strategy where printed ceramic parts serve two roles: (1) bonding elements, printed separately and joined with UV-curable ceramic resin for co-sintered monolithic assemblies and (2) non-bonding support structures, positioned in dry contact beneath overhanging features to temporarily support them during sintering, preventing deformation.

Mechanical performance of bonded joints are evaluated through four-point bending, Weibull analysis across three joint configurations, varying in mechanical interlock and stress distribution characteristics, and benchmarked against monolithic baselines. Monolithic samples exhibited the highest strength ($��{\sigma }_o�=�226.8�$ MPa, $��\beta �=�11.98�$). Among bonded geometries, face-edge joints (normal and aligned to build direction)—where a flat surface is bonded perpendicularly to the edge of another segment retained the highest strength at 60.6% of monolithic baselines ($��{\sigma }_o�=�137.5�$ MPa, $��\beta �=�6.57�$).

Nonbonding support structures, placed in dry contact beneath overhanging features, exhibited synchronous shrinkage during sintering reducing distortion from 1 mm to below measurement resolution, addressing critical barriers in ceramic AM.

This study investigates the soldering process for joining silicon nitride (Si₃N₄), a commonly used ceramic, to Invar42, a low thermal expansion alloy. The focus lies on analyzing interfacial reactions and evaluating the bonding performance of the Si₃N₄—Invar42 joint. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS) were employed to examine the microstructure, elemental distribution, and chemical composition of the interfacial region. The results underscore the critical role of interfacial reaction layers in the soldering process. Mechanical testing (single lap offset, SLO, lap shear tests) was conducted to assess the bonding strength and mechanical integrity of the soldered joints. Furthermore, the thermal stability and reliability of these joints were evaluated through SLO tests at 300°C. This study contributes to the advancement of a user-friendly, pressureless, localized heating and field-deployable technique for soldering Si₃N₄ to Invar42, thereby facilitating the fabrication of advanced engineering systems in industrial environments.

Compositionally complex transitional metal nitrides are an interesting class of ceramics with superior chemical, thermal, and mechanical stability, with a high potential in ultra-high temperature applications and catalysis. The exceptionality in the properties may partly be explained as a consequence of their high configuration entropy. Although promising candidates, the bulk synthesis of compositionally complex metal (carbo)nitrides remains challenging, often limited by purity and scalability due to significant oxygen contamination from gaseous reactants or nitrogen loss. To offset these disadvantages, the current manuscript proposes an alternative synthesis route for the synthesis of a compositionally complex nitride (V, Nb, Ta, Mo, W)N_x, which deviates from the typical solid-state and sputtering methods by employing an organometallic precursor route and a double ammonolysis process. This is a first attempt to synthesize such ceramics with low oxygen contamination in compositionally complex (carbo)nitrides with a scalable production_. Using a multidisciplinary approach consisting of theoretical methods and experiments, the current study elucidates the evolution and stability of the precursor at high temperatures under carbon, and thereby obtained ceramics at different temperatures.

With the increasing demand for synergistic performance in “mechanical–aesthetic–biocompatibility” properties of dental restoration materials, lithium silicate glass-ceramics (LSGCs) have emerged as a core material in fixed prosthodontics, owing to the unique advantages of their “glass–crystal” biphasic composite structure. This article provides a systematic review of recent research advances in LSGC from multiple perspectives, including chemical composition, microstructure, mechanical properties, and aesthetic characteristics. It discusses the effects of composition regulation, morphology control, and environmental factors on the mechanical and optical properties of LSGC. Furthermore, it explores the application of machine learning in performance prediction and inverse design—such as analyzing adhesion mechanisms and color matching—while also addressing current challenges, including unclear long-term performance in multifield coupled environments and the difficulty in achieving high mechanical–optical performance synergy. Future development trends focus on multiscale reinforcement, intelligent bioinspired modification, and machine-learning-driven full-chain design, facilitating the transition of LSGC from empirical optimization toward personalized and intelligent restorative materials.

In the present study, aluminum-modified preceramic silicon polymers were synthesized via chemical modification of a commercially available organopolysilazane using an aluminum amido complex. The incorporation of aluminum into the polymer structure and its effect on ceramization behavior and processability as well as the thermal and mechanical properties of the obtained Si─Al─C─N ceramic materials were systematically investigated. The microstructure and chemical composition of the dense, predominantly amorphous monolithic Si─Al─C─N were characterized using solid-state nuclear magnetic resonance, scanning electron microscopy, and transmission electron microscopy. Aluminum incorporation led to enhanced densification of Si─C─N, resulting in monoliths with a porosity fraction as low as 2 vol% achieved for the composition with the highest aluminum content. Al incorporation was shown to also result in a significant reduction in thermal conductivity, thus, Si─Al─C─N formulations exhibited values as low as 0.6 W m⁻¹ K⁻¹. The hardness and Young's modulus remained nearly unchanged upon aluminum incorporation, with values of ca. 14.5 and 156 GPa, respectively, for the high-aluminum-content sample. To the best of our knowledge, the present study reports for the first time on the thermal and mechanical properties of dense, mainly amorphous Si─Al─C─N ceramics, highlighting the suitability of Si─Al─C─N as excellent material for possible thermal insulation at temperatures beyond 1000°C.

The preliminary results of hyperspectral neutron radiography of Si–SiC made with binder jet additive manufacturing, subsequent carbon addition, and silicon melt infiltration are presented. The samples were measured in the processing states before and after the melt infiltration to determine if neutrons would help characterize the microstructure to better understand the melt infiltration process. Theoretical Bragg edges were calculated for comparison with the radiographic results. The changes in the Bragg edges from pre- to post-infiltrated reaction-bonded SiC were evident, that could be used to address the differences in microstructures. The preliminary results presented in this study demonstrated that neutron Bragg-edge imaging is possible with Si–SiC reaction-bonded ceramics and can help determine the microstructure of melt infiltrated samples.

Flash joining (FJ) typically requires applying a threshold electric field at high temperatures to generate oxygen vacancies, a process that often imparts damage to the base material. Existing improvement approaches, such as pretreatment, can introduce oxygen vacancies in advance but involve complex processes. To address this, we propose a novel two-step FJ technique. Unlike ordinary FJ, this method implements dual electric field: initial application at a lower temperature followed by reheating to target temperature with field reapplication. The key strategy of applying electric fields in stages is to generate vacancies prior to the joining process, which effectively lowers the onset FJ conditions. Additionally, this approach significantly enhances bonding of yttrium oxide/titanium, achieving a 65.8% increase in shear strength compared with ordinary FJ. The two-step FJ plays a role in two ways: (i) Promoting oxygen vacancy generation to reduce current excitation time, thereby reducing damage to the base material; (ii) Vacancy aggregation at the interface to accelerate filling reactions and atomic diffusion. By applying an electric field in stages to control defects, these findings provide a new approach to improving FJ strength.

The development of cost-effective, nonradioactive zirconium (Zr)-free opaque glazes represents a critical objective for sustainable ceramic manufacturing. This study successfully prepared an augite-based glass-ceramic glaze within the CaO–MgO–Al₂O₃–SiO₂ system using economical industrial raw materials. The glaze was prepared via a frit route, involving melting the raw materials, quenching the melt to obtain a frit, ball-milling the frit into a slurry, and finally dip-coating and firing. Systematic investigation revealed that firing at 1150°C produced an optimal microstructure dominated by augite (24.9 wt.%) and cristobalite (20.4 wt.%) crystals, with a refined grain size of ∼1.4 µm. The resulting glaze exhibited properties comparable to conventional ZrSiO₄-based systems, achieving a superior L^* value of 89.21 (+77.6% vs. ceramic body), whiteness of 76.1% (+561.7% vs. ceramic body), and Vickers hardness of 7.10 GPa. These findings confirm that augite-based opaque glazes are a technically viable and more sustainable alternative, offering valuable insights for the development of low-temperature-fired, Zr-free ceramic glazes.