International Journal of Applied Ceramic Technology最新文献

High-strength foamed ceramics were synthesized employing silicon-manganese slag (SM) and fluorgypsum (FG) as raw materials, with SiC serving as the foaming agent. Investigations into the influence of firing temperature and FG content on the phase structure, microstructure, and physical properties of foam ceramics were conducted. Characterization of the samples was performed through X-ray diffraction and scanning electron microscopy. Results indicate that an increase in FG content lowers the matrix melting point, promotes crystal growth, enhances compressive strength, and forms a uniform pore structure. At an FG content of 11%, ceramics prepared at a firing temperature of 1130°C exhibit a density of 0.56 g/cm³, porosity of 78.45%, and compressive strength of 3.05 MPa. This study explores the use of FG as a cost-effective alternative to borax, demonstrating a sustainable approach for foam ceramics preparation using silicomanganese slag and FG synergy.

This study investigated the influences of WC and HfB₂ additives along with SiC reinforcement (with various particle sizes) on densification, microstructure, and mechanical properties of ZrB₂–SiC composites. The results showed that WC and HfB₂ addition formed a solid solution of (Zr,W,Hf)B₂ with a core–shell structure, whereas the remaining WC transformed into WB. Moreover, nano-sized SiC caused a much better impact on densification compared to micro-sized SiC. A small fraction of localized phases like ZrC, HfB, and (Hf,Zr)C in the form of solid solution were also formed. The maximum room temperature flexural strength and the fracture toughness of the sample containing 150 nm SiC and 8.9 wt.% WB were measured to be 682 $�\pm$ 17 MPa and 6.5 $�\pm$ .3 MPa m^1/2, respectively.

By using tartaric acid (TA) as a wet-method modifier to modify steel slag powder (SS), it is helpful to reduce the content of free calcium oxide (f-CaO) in SS and further improve the mechanical properties and soundness of SS as supplementing cementitious materials (SCM) in the mortar. The results indicate that with the addition of 2 wt% of TA, the number of large particles bigger than 45 µm in the SS decreased, resulting in predominantly smaller particles smaller than 45 µm. While the specific surface area increased from 417 to 704 m²/kg, the water consumption at standard consistency was significantly reduced. The soundness of the paste SS as SCM had improved including the f-CaO content decreased from 4.81% to 0.95%, and the Le Chatelier expansion reduced from 4.5 to 1.5 mm. The mechanical properties were significantly enhanced, with the flexural strength increasing from 5.6 to 7.8 MPa, and the compressive strength rising from 38.8 to 52.7 MPa. After 28 days of curing in water, the hydration products of the mortar are hydrated calcium silicate (C-S-H), calcium hydroxide (CH), and calcium carbonate (CaCO₃).

In this study, the reaction interfaces of four kinds of oxide refractories (corundum, spinel, mullite, and zirconia) with lanthanum oxide (La₂O₃) and lanthanum aluminate (LaAlO₃) under different atmospheres at high temperatures (1550°C) were analyzed. The results show that the four oxides have a strong reaction with La₂O₃, and the corresponding rare earth aluminate, rare earth silicate, and rare earth zirconate are formed respectively. The reaction with LaAlO₃ is weak, and almost no reaction occurs. Mullite has poor structural stability in a high-temperature reduction atmosphere, easy decomposition, and strong reaction with La₂O₃. This study provides an important reference for the study of the reaction mechanism between rare earth steel and lining materials and the research and development of special lining materials for rare earth steel.

Digital image correlation (DIC) method was employed to analyze the dynamic bending of a metallized Si₃N₄ substrate in thermal cycles ranging from −40°C to 250°C. The substrate was monitored by DIC over several consecutive cycles, spanning from 0 to 2501. Three DIC measurement intervals, specifically during 999–1001, 1999–2001, and 2499–2501 cycles, were selected to analyze the bending behavior in response to temperature fluctuations. By the scanning acoustic microscope (SAM), the substrate revealed negligible delamination after 1001 cycles, light delamination after 2001 cycles, and serious delamination post-2501 cycles. The dynamic bending remained unchanged during 999–1001 cycles. A curve with a negative bending was observed during 1999–2001 cycles, with a peak curvature of .024 mm⁻¹ at −40°C; the negative bending intensified with a curvature reaching .050 mm⁻¹ at −40°C during 2499–2501 cycles. The bending curve then decreased during the heating phase and returned to a non-bent state at elevated temperatures. The bending curve reversed to positive at 250°C during thermal cycles from 2499 to 2501. The bending behavior throughout thermal cycles was discussed in relation to the asymmetric delamination observed on both sides of the substrate, as well as the distribution of delamination.

Utilizing marine waste and resources for eco-friendly building materials is pivotal in promoting sustainable development in island and coastal construction industries. Among the potential alternatives, coral sand as well as sea sand stands out as a promising material. This research seeks to explore the potential of coral/sea sand as a fine aggregate in the creation of environmentally sustainable marine engineered geopolymer composites. An assessment was conducted on the influence of varying proportions of coral sand, meant as a substitute for sea sand, on the flowability, drying shrinkage, mechanical properties, and microstructure of the marine engineered geopolymer composites. The findings indicate that as coral sand replaces sea sand, flowability and drying shrinkage decrease, while compressive strength experiences an initial rise followed by a decline. Encouragingly, a combination of coral and sea sands enhances tensile ductility. Overall, a 20 wt.% coral sand mixture yields optimal results, with the compressive strength is 54.4 Mpa and the tensile strain capacity is 2.397% after 28 days. Moreover, microscopic tests reveal changes in hydration products and pore structure. Our research delves into the potential of coral/sea sand as a fine aggregate in the creation of environmentally sustainable marine engineered geopolymer composites.

Large gas engines are typically applied to compensate for peak loads and grid instabilities in the electric power supply. A key component of these engines is the spark plug. Because of the harsh conditions encountered in their use, the spark plug electrodes are subject to significant wear. Conventional electrodes are expensive due to the precious metal alloys they contain. As an alternative, ceramic materials from the groups of silicide, carbides, and nitrides were selected for preliminary experiments that investigate functional as well as mechanical properties and wear behavior. Because of the harsh conditions during operation, the new materials must have a high melting temperature, good thermal shock resistance, high thermal conductivity, and high corrosion/oxidation resistance as well as high density. It was found that the mechanical and thermomechanical properties of certain ceramic candidates are sufficient for application as spark plug electrodes. Furthermore, the chosen ceramic materials achieve an adequate performance in terms of secondary voltage trace and ignition behavior. However, wear resistance may not be sufficient for service times longer than the service time of existing spark plugs and further research is still necessary before ceramic electrodes may be established as a commercial alternative to existing electrodes.

Alkali-activated materials (AAMs) were prepared using tungsten tailings via pressure molding and casting, and their high-temperature resistances were analyzed. Variations in their compressive strength, gel, and physical phase transformation, pore structure, and morphology at different temperatures were investigated and comparatively analyzed. Results showed that the compressive strength of both AAMs first increased and then decreased with increasing temperature. At 600°C, the pressure-molded AAM exhibited a considerably higher compressive strength (152.38 MPa) than the cast-molded AAM (42.05 MPa). Thermogravimetric–differential scanning calorimetry, XRD, and FTIR analyses showed that the pressure-molded AAM contained more gel phases than the cast-molded AAM at the same temperature. The gel phase further polymerized and decomposed at high temperatures (>800°C), forming nepheline and zeolite crystals. Mercury intrusion porosimetry and scanning electron microscopy results revealed that pressure molding increases the contact between the gel and unreacted materials, effectively reducing the porosity and densifying the AAM. The pressure-molded AAM had a considerably smaller pore diameter than the cast-molded AAM; thus, the former had considerably higher compressive strength. The porosity and pore size of the pressure-molded AAM gradually increased with the temperature, which polymerized the gel phase and eventually decomposed it; this increased its compressive strength first and then decreased.

In the field of ceramics, mullite has drawn plenty of attention due to its low thermal expansion and thermal conductivity as well as its high chemical stability and creep resistance. This work reported the mineral phase, liquid phase, and microstructure evolution of the sintered mullite, using coal-series kaolin as the raw material and potash feldspar as well as phosphorus pentoxide as additives. The effects of K₂O and P₂O₅ on the content and viscosity of the liquid phase in mullite were calculated using FactSage 8.1. The results showed that the introduction of K₂O could inhibit the formation of cristobalite effectively. Adding K₂O and P₂O₅ improved the content of the liquid phase formed during the calcination process. After introducing K₂O and P₂O₅, mullite developed acicular and columnar structures, with average lengths of 9.76 and 7.97 µm, respectively. Furthermore, introducing K₂O and P₂O₅ improved the physical properties of mullite significantly.

Herein, a spinel-type high-entropy ceramics (Co_.2Cr_.2Fe_.2Mn_.2Zn_.2)₃O₄ is introduced. The obtained ceramics exhibit superior thermal stability under accelerated aging conditions at 125°C for 500 h, that is, aging drift was less than .35% for all samples sintered at temperatures (1200or–1275or . The variation of resistance is mainly attributed to the oxidation of grain boundaries and the migration of oxygen vacancies. The relationship between crystal structure evolution and aging properties was investigated using structural analysis and P–V–L bonding theory. Theoretically, the Co/Cr/Mn/Fe–O bonds at the octahedral sites in the spinel structure are more important for controlling structural stability.