International Journal of Applied Ceramic Technology最新文献

Yttrium-stabilized zirconia (YSZ) plays a crucial role in thermal barrier coatings widely used to protect metallic components in gas turbine engines against high-temperature combustion product gases and harsh environments. The thermal conductivity of these coatings is a critical parameter influencing the gas turbine design, performance, and service life. In this study, a laser temperature gradient method is utilized to measure the thermal conductivity of porous YSZ coatings. The method employs specialized laser energy delivery to create a one-dimensional temperature gradient through the sample thickness, closely simulating the operational condition. This approach provides an effective, direct means to determine the thermal conductivity of high-temperature heat-resistant porous ceramic materials.

This study introduces a feasible approach for preparing Al₂O₃-based ceramics with highly controllable performance via binder jetting. The Al₂O₃-based ceramics were prepared using Al₂O₃ and H₃BO₃ as raw materials. The results showed that the samples prepared with 0.24 mol H₃BO₃ exhibited high apparent porosity (64%–66.67%), well-bending strength (3.46–8.53 MPa), and low thermal conductivity (0.113–0.329 W·m⁻¹·k⁻¹ at 200–800°C). It was observed by an electron microscope that the increase of boric acid content led to the in-situ formation of more aluminum borate grains in the sample. Meanwhile, the remaining Al₂O₃ reacts with silicon oxide in the impregnation solution to form mullite whiskers. The whiskers ensured that the sample had superior mechanical properties and lower thermal conductivities. Based on the above properties, the possibility of Al₂O₃-based ceramics application in the aerospace field can be speculated.

As a promising high-thermal-conductivity ceramics, the direct bonding of Si₃N₄ with metals remains challenging. Here, we employed active metal brazing of Si₃N₄ ceramics and Kovar alloys using AgCuTi metal filler, and found that the shear strength in the prepared Kovar/AgCuTi/Si₃N₄ joints depends on the competitive correlation between the interface layers. The competitive consumption for active element Ti by Kovar/AgCuTi interfacial reactions reduced AgCuTi/Si₃N₄ interface layer thickness and deteriorated final shear strength, even when using a high-Ti-content filler. Surface analysis indicated that interfacial fracture between Ag-based solid solution and Ti₅Si₃ was the primary cause of failure. Density functional theory (DFT) revealed that Ag (111)/Fe₂Ti (001) interface had higher ideal work of adhesion (W_ad) than Ag (111)/Ti₅Si₃ (001) interface, confirming the importance of AgCuTi/Si₃N₄ interface layer. Ultimately, by adjusting interface reaction layer thickness, the joints reached a high shear strength of 154.3 MPa.

By experimental characterization and numerical modeling, the dependence of thermophysical properties on time and temperature as well as its influence on the thermomechanical behavior of alumina–magnesia castables has been studied in this work. The thermal conductivity, thermal expansion coefficient, and Young's modulus are the most important parameters, which evolve with temperature and piecewise change with the thermal processes of drying, preheating, and service. It is mainly related to the sintering degree and amount of formed calcium aluminate and spinel phases. The sensitivity analysis of parallel simulations for multilayer steel ladle with different numbers of temperature-dependent thermophysical parameters demonstrates that the thermal conductivity is the most influential parameter, as it dominates the temperature distribution and affects the succeeding thermal expansion as well as deformation. The increase of thermal expansion coefficient and decrease of Young's modulus with temperature counterbalance the deformation of linings under thermal process. Meanwhile, compared with the simulation using temperature-independent parameters, the model with temperature-dependent thermophysical parameters exhibits more severe damage in outer surface of both the working lining and the permanent lining. This gives new insight into the adoption of temperature-dependent parameters for actual thermomechanical behavior evaluation of refractories.

Laser cladding technology is an advanced surface modification technique that has gained significant attention in various fields due to its energy savings, efficiency, and environmental friendliness. This paper discusses the preparation of AlCoCrFeNi high-entropy alloy (HEA) coatings on the surface of a 5083 aluminum alloy using laser cladding technology under the Ar gas conditions. An orthogonal test system was used to optimize the laser cladding process parameters. The microstructure, as well as the mechanical, frictional, and electrochemical properties of the HEA coatings, were comparatively analyzed under the two process conditions S₄ and S₁₀. The results indicate that, under S₁₀, the HEA coatings exhibit optimal surface quality. The coatings contained a mixture of Face-centered cubic (FCC) and Body-centered cubic (BCC) phases. Microscopic examination revealed three distinct areas: dark, gray, and off-white. The coatings can significantly improve the wear and corrosion resistance of the alloy substrate. For the best results, it is set the laser power to 200 W, the laser scanning distance to .05 mm, and the laser scanning rate to 1250 mm/s. This present study offers a novel technical foundation for the fabrication of HEA coatings.

The investigation focused on examining the impact of incorporating Fe-carbon nanotubes (CNTs) on the valence state and oxygen vacancies, and the physicochemical parameters of the catalytic system. For the CeO₂/TiO₂ catalyst with Fe-CNTs, no distinct X-ray diffraction (XRD) peaks corresponding to Fe-CNTs were observed. This indicated their uniform dispersion, supported by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) imaging. X-ray photoelectron spectroscopy (XPS) analysis was conducted to observe the changes in the valence state due to the addition of Fe-CNTs. The concentration of Ce³⁺ on catalyst surface increased from 19.90% to 29.48% with an increased concentration of the chemisorbed oxygen species (O_α). This suggests that the addition of Fe-CNTs into CeO₂/TiO₂ catalyst reduced Ce⁴⁺ on the catalyst surface, resulting in the formation of oxygen vacancies. Oxygen temperature-programmed desorption (O₂-TPD) and hydrogen temperature-programmed reduction (H₂-TPR) analyses showed both the adsorbed oxygen species and H₂ consumption increased with adding Fe-CNTs. Furthermore, the onset temperatures for O₂ desorption and H₂ consumption became lower, confirming the enhancement of catalytic redox properties.

Porous mullite ceramics were synthesized via ceramic processing using a local industrial kaolin, alumina, and with AlF₃ and MoO₃ precursor additives to catalyze the formation of pores and acicular mullite grains. The textural properties, crystalline phases, microstructures, and mechanical properties of the obtained samples were comprehensively analyzed and compared with a reference mullite formulated without additives. The obtained ceramics have a well-defined porous microstructure, with a porosity of about 50%, and a pore size distribution in the 0.1–2 µm range. Ceramics that involve the addition of MoO₃ present well-defined acicular mullite grains, with slightly higher porosity, larger pores, and better mechanical resistance compared to those processed using AlF₃.

To correlate the ceramic porosity with its mechanical properties, a simple model of spherical pores was proposed to assess the flexural strength of the dense ceramic. It was found that the inclusion of additives promoting needle-like microstructures increases the mechanical resistance up to four times the value determined for the ceramic without additives (flexural strength up to 390 MPa for zero-porosity extrapolation). These results, together with the refractoriness of mullite, allow inferring the potential applications of the developed materials as structural ceramics with relatively low density and for filtering applications.

Rapid industrialization has led to significant environmental challenges, including the disposal of effluents with high zinc ion concentrations. This study investigates the use of hydroxyapatite nanoparticles as an adsorbent for Zn (II) ions from aqueous solutions at neutral pH. These nanoparticles are characterized by their high purity, mesoporous structure, and a specific surface area of 60.97 ± .40 m² g⁻¹. Their thermal stability was confirmed by thermogravimetric analysis, and zeta potential measurements indicated a surface charge close to the isoelectric point. Adsorption experiments showed that the kinetics fit well with the pseudo-second-order model, with a rate constant of 2.58 ± .49 min⁻¹ mg⁻¹ and a determination coefficient (R²) of 1.00. Isotherm analyses using Redlich–Peterson, Langmuir, and Freundlich models revealed the highest adsorption capacity and best fitting with the Redlich–Peterson model, showing maximum capacities of 30.36 mg g⁻¹ (linear fitting) and 32.11 mg g⁻¹ (nonlinear fitting). These fits achieved R² values of .9949 and .9923, respectively, suggesting efficient and reliable adsorption profiles. This research highlights the potential of hydroxyapatite nanoparticles for effective zinc ion removal, supporting their application in sustainable industrial practices and environmental remediation.

Mullite is an aluminosilicate compound that can be fabricated from various sources of raw materials. Mullite (α) was synthesized from six different mine tailings reinforced with alumina. The tailings were finely ground into powder to determine their chemical components using X-ray fluorescence (XRF) and X-ray diffraction (XRD) spectroscopic technologies. Silica was discovered in all the tailings in significant quantities followed by alumina (high purity α-alumina). 50 g of the first sample which composed 68.8 w(M)/10⁻² of SiO₂ and 13.2 w(M)/10⁻² of Al₂O₃ was measured, reinforced with 81.1 g of Al₂O₃ and subjected to a high-energy ball mill for 30 min to enhance the reaction between SiO₂ and Al₂O₃. The process was repeated for all six powdered tailings. Each mixture was sintered at 1100°C and 1200°C in a muffle furnace for 4 hours at a heating rate of 10°C/min. The sintered materials were characterized using SEM, EDS, XRD, and FTIR techniques. Results and analysis show a significant amount of prismatic α-mullite formed in all six sintered samples. The formation of mullite crystals was observed to increase with an increase in temperature from 1100°C to 1200°C. The phenomenal fabrication of mullite from mine tailings is significant in ceramic technology.

This research aimed to implement a finite element heat transfer model to simulate the thermal cycle of steel ladles using an open-source tool. FEniCS was selected, as it can solve partial derivative equations such as the heat transfer ones, which describes the thermal state of the steel ladle via finite element method. For this, each step of the steel ladle cycle (preheating, waiting steps, and holding) had its own model, comprising specific combinations of boundary conditions. An energy consumption analysis was carried out based on the calculation of the heat flux for each stage of the ladle cycle according to three selected configurations of the refractory lining chosen for the simulation. The results showed that the solutions obtained by both the open-source method and by the commercial tool (Abaqus) were equivalent. The comparison of different lining configurations, especially using insulators, presented several advantages from the energy point of view. The attained conclusions can be of great interest to the refractory engineers who seek novel solutions to improve the insulating performance of the steel ladle. The present framework makes it possible to test a multitude of different designs and processing operation conditions, making the proposed tool a cost-effective solution to aid the required improvements to reduce the carbon footprint of critical industrial processes such as steelmaking.