International Journal of Applied Ceramic Technology最新文献

A new preparation process for silicon carbide (SiC) powder is developed. In the Si–(C) –PTFE–Ar system, the grain size and morphology of the product 3C–SiC were controlled by adding a carbon source (graphite) and changing the percentage of polytetrafluoroethylene (PTFE) (0%, 10%, and 20%). The experimental results showed that the SiC powders prepared using a molar ratio of 1:1 silicon powder to graphite, plus 20% PTFE have a uniform particle size distribution (∼130 nm), a lamellar structure made of spherical particle stacking, a small bandgap (1.80 eV), a high carrier concentration, and a large number of lattice defects. These properties are expected to increase the electrical conductivity of 3C–SiC and decrease its thermal conductivity, thus providing a promising feedstock preparation option for SiC thermoelectric materials. In addition, the mechanism of PTFE in the preparation of SiC reactions was studied in detail.

Due to their exceptional impact resistance, ceramics are extensively used in various fields. However, unavoidable pores, microcracks, and inherent defects can degrade the performance of ceramic materials. A damage model of SiC ceramics under passive confining pressure was constructed based on the Lemaitre strain equivalence principle and the Weibull distribution function. This paper presented a dynamic damage model for SiC ceramics subjected to passive confinement pressure based on the principles of damage mechanics. Additionally, the split Hopkinson pressure bar device was employed to investigate the compressive strength and damage evolution of SiC ceramics at various shock pressures and confinement degrees. The experimental results indicate that constraints can reduce the damage to ceramics. The metal sleeve increased stiffness when compressing the ceramic material, allowing the specimen to convert from brittle–plastic–brittle. When sufficient constraints can be provided, the peak strain decreases gradually with the increase of the impact air pressure. Experimental data showing good agreement with the proposed model validated and analyzed the established model. Thinner boundary constraints cannot maintain the stability of ceramic structures, thicker boundaries do not significantly improve performance, and thicker boundaries can cause more weak areas. This paper provides guidance for the design of encapsulated ceramic composite armor by quantitatively studying the constraint thickness.

This paper aims to improve the density and thermal shock resistance of Y₂O₃ ceramics for the preparation of ultra-pure high-temperature alloy crucible materials. The doping effect of MgF₂ content on the densification behavior, physical properties, and thermal shock resistance of Y₂O₃ ceramics was systematically investigated in this paper. The results suggested that the presence of MgF₂ greatly promoted the growth of Y₂O₃ grains and the transformation of the pore structure by liquid-phase sintering. And the mechanical properties of the MgF₂-doped Y₂O₃ ceramics were significantly improved. Besides, the marked improvement in the thermal shock resistance of MgF₂-doped Y₂O₃ ceramics was attributed to the synergistic action resulting from the growth of grain size and the enhancement of the crack deflection effect. In particular, the relative density of Y₂O₃ ceramics doped with 1.5 wt% MgF₂ reached 96.4% and the residual flexural strength ratio after thermal shock achieved 45.0%, showing an excellent application prospect.

The thermal shock resistance of ceramics is a key factor for determining the durability of ceramic components under transient thermal conditions and is also one of the key factors for evaluating the stability of ceramics under extreme thermal conditions. After rapid heating or cooling, the surface and internal thermal stress mismatches of ceramics can cause severe thermal damage. Two main types of ceramic thermal shock exist: rapid cooling and rapid heating thermal shock. This article presents a broad understanding and insight into fundamental theory and experimental methods for ceramic thermal shock testing. The experimental equipment and procedures, test result evaluation, and material characterization of ceramic thermal shock are summarized. Moreover, outlooks and perspectives are discussed for testing and characterizing ceramic thermal shock resistance. This review will be helpful to researchers performing studies in the relevant fields of ceramics.

Liquid-phase laser irradiation technology was utilized to synthesize graphene-coated tungsten carbide (WC@G) core–shell composite materials with regular spherical morphology. Characterization via scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, and Raman spectroscopy revealed the evolution of WC particle microstructure from sharp edges to regular spherical shapes post-laser irradiation. High-resolution TEM displayed a tightly knit core–shell structure. Raman spectroscopy confirmed graphene presence through D, G, and 2D peaks. Incorporation of WC@G into a titanium diboride matrix, followed by discharge plasma sintering, yielded TiB₂/WC@G composite ceramic materials. Compared to TiB₂/WC/G composite ceramic materials, the WC@G core–shell structure significantly enhanced sintering performance. Optimal mechanical properties were achieved with 6 wt.% WC@G, exhibiting a relative density of 99.6%, Vickers hardness of 18.5 GPa, flexural strength of 696.9 MPa, and fracture toughness of 8.5 MPa m^1/2. Characterization identified graphene detachment, pull-out, and fracture deflection as key mechanisms enhancing toughness in TiB₂/WC@G composite ceramic materials.

Careful material selection is paramount to meet the significant challenges posed by harsh environments in advanced applications. Ceramic matrix composites (CMCs) have come to the forefront of consideration for many of these applications where environmental resistance needs to be combined with structural stability at high temperatures (1200°C+). Many gaps exist in understanding how material variations pose unique material and design challenges that affect the final performance in a particular application. Thorough materials testing at relevant temperatures is required for various candidate materials to realize an analytical approach to materials selection. This review will discuss mechanical and environmental tests and their use at high temperatures including tensile tests, flexure tests, lifetime testing methods, interlaminar tests, and environmentally relevant tests. Challenges for performing these tests at high temperatures and on CMCs will be discussed. A literature review will provide examples of state-of-the-art testing, and the test results from historical work and improvement opportunities will be addressed. This review aims to provide an overview of the current capabilities and practices for high-temperature testing and recommend best practices for performing high-temperature tests and interpreting and sharing the results and metadata with the larger community to expand the CMC material property database.

Reliable metallurgical bonding between Al₂O₃ ceramic and copper was achieved by vacuum brazing using Ag–23Cu–14.5In–3.3Ti (wt.%) alloy. The representative interfacial structure of the joint was Al₂O₃/Ti₃(Cu,Al)₃O + γ-TiO/Ag-based solid solution + (Cu,Ag)₇In₃ + Ag–Cu eutectic + Cu-based solid solution/copper. The interface microstructure evolved with process parameters, including the formation of γ-TiO and Ti₃(Cu,Al)₃O, as evidenced by microstructural analysis and etched surface morphology. The relationship between fracture path and shear strength was established by observing the fracture morphology and performing shear strength tests on joints with various process parameters, utilizing the degree of the Ag-based solid solution loss and the thickness of the reaction layer as evaluative factors. When brazed at 760 or 780°C for 20 min using a 100 µm brazing alloy foil, the brazed joints demonstrated a peak shear strength of 215 ± 25 MPa, and the fracture predominantly occurred in the Al₂O₃ matrix and Ti₃(Cu,Al)₃O layer.

Environmental barrier coatings (EBCs) are indispensable for the service of SiC-based turbine engines. The Si-bond coating is a critical layer that prevents oxidants from penetrating SiC substrates and determines the service lifetimes of EBCs. In this study, the oxidation behaviors and failure mechanisms of Si-based bond coatings were reviewed. The large growth rate and phase transformation of thermally grown oxides (TGOs, SiO₂) seriously deteriorate the service of Si-bond coatings. The low melting point of Si further limits its application in next-generation engines above 1 427°C. The results show that an isolated particle healing (IPH) treatment decreased the oxidation rate of the Si-bond coating by ∼24% at 1 300°C. Moreover, the Si–HfO₂ and Si-stabilizer (Si–Al₂O₃ or Si-mullite) composite/duplex bond coatings can eliminate SiO₂ phase transitions, thus improving the service lifetime. In addition, rare earth silicide (RESi), SiC and SiO₂–HfO₂ composite show potential for use in next-generation EBCs above 1 427°C. This review provides guidance for designing Si-based bond coatings with improved service lifetime.

Porous geopolymer composite (E51) reinforced by E51 epoxy resin was prepared by well-distributed dual-blending using red mud, metakaolin, and slag as raw materials. The effects of E51 content on microstructure, porosity, mechanical properties, and thermal insulation properties of the porous composites were investigated. The addition of E51 changed the setting time and viscosity of the slurry with high content of solid wastes (80%), which play an important role in the formation of pores during the direct foaming process. The addition of E51 had great influence on the porous properties of geopolymer composites, which in turn affected their compressive strength (0.19–1.44 MPa) and thermal conductivity (0.09–0.12 W/mK). The addition of E51 enabled the production of geopolymer composites in a rather large range of total porosity (67.3–81.1 vol%), with an optimal sample possessing a total porosity of up to 78.7 vol%, a thermal conductivity of 0.086 W/mK, and a compression strength of 0.47 MPa.

Zinc-doped indium oxide (IZO) thin films were deposited on silicon dioxide substrates by radio-frequency magnetron sputtering using an IZO ceramic target with In₂O₃/ZnO weight ratio of 9:1. The effects of power, pressure, and distance between target and substrate on microstructure and photoelectric properties of IZO films were investigated. The results show the performance of IZO films prepared under the conditions of power 80 W, air pressure .5 Pa, and target base distance 80 mm are the best, and the IZO films are amorphous with high transmittance (>86.0%), high mobility (>45.0 cm²/V s), and low resistivity (less than 2.0 × 10⁻⁴ Ω cm), which are the best photoelectric performance reported at present. This work provides a feasible research approach for preparing high-performance IZO thin films.