International Journal of Applied Ceramic Technology最新文献

TC4 titanium alloy has been widely used in the automotive field due to its exceptional properties. However, inherent defects such as low hardness and poor wear resistance for TC4 alloy limited its wider application. The microarc oxidation (MAO) technique was employed in this paper to prepare MAO coatings on TC4 titanium alloy. The microstructure, phase structure, mechanical properties, and tribological performance were systematically evaluated. The results show that the coating contains a large amount of rutile TiO₂ hard phase after MAO treatment, which significantly improves the mechanical properties of the substrate. The hardness of the MAO coating can reach 581 HV_.05. Furthermore, the synergistic lubrication effect of onion-like carbon (OLC) nanoparticles and organic molybdenum dithiocarbamate (MoDTC) in PAO oil was observed for MAO-treated TC4. Particularly, when .01 wt.% OLC is used with 1 wt.% MoDTC oil, the coefficient of friction (COF) decreases to .062, and the wear rate decreases to 4.3 × 10⁻⁷ mm³/Nm. Combined Raman and X-ray photoelectron spectroscopy (XPS) analysis indicate that OLC is deposited on coating area to form a lubricating carbon film. Additionally, OLC can promote the decomposition of MoDTC during sliding to generate a tribofilm containing MoS₂.

The aim of this work is to fabricate a low-cost ceramic microfiltration (MF) membrane made from a new geomaterial named peridotite. The membrane was prepared by uniaxial pressing and followed by sintering. The effect of sintering temperature, in the range of 1100–1225°C, on the permeability, porosity, mechanical strength, and pore size was investigated. The optimized MF membrane sintered at 1200°C exhibits 1198.9 L h⁻¹ m⁻² bar⁻¹ of permeability, 36.41% of porosity, 12.9 MPa of mechanical strength, and 1.56 µm of pore size. The prepared membrane was used for the MF treatment of dairy wastewater. It was found that the membrane is able to remove 88.56% and 69.54% of turbidity and chemical oxygen demand, respectively. Furthermore, the cost of the peridotite membrane was estimated to be $10.3 m⁻².

LaB₆–HfB₂ composites with the different HfB₂ contents (10 wt.%, 30 wt.%, 50 wt.%, 70 wt.%, and 90 wt.%) were densified by spark plasma sintering (SPS). Results showed that the densification mechanism of the composite transformed from the grain boundary diffusion into the dislocation climbing mechanism as the holding time was extended from 0 to 15 min under temperature range of 1750–1900°C. The HfB₂ phase could effectively limit the grain growth of LaB₆ phase, and the dynamic growth of the grain was governed by grain boundary diffusion. Both the Berkovich hardness and Vickers hardness obeyed the normal indentation size effect. LaB₆–70 wt.% HfB₂ composite had the highest fracture toughness of 3.98 ± .43 MPa m^.5, whereas the highest current density of 18.34 A/cm² belonged to LaB₆–30 wt.% HfB₂ composite. All the results demonstrated that LaB₆–HfB₂ composite was a promising material with the excellent structural and functional performance.

This study aimed to compare and summarize the mullitization mechanism of the sillimanite group minerals and investigated its effect on the mechanical properties of Al₂O₃-SiC-C gunning materials. By comparing the phase composition and microstructure of kyanite, andalusite, and sillimanite at different temperatures, the mullitization mechanism of sillimanite group minerals was clarified. Furthermore, the Al₂O₃-SiC-C gunning materials with sillimanite group minerals addition were prepared by bauxite and fused brown corundum as aggregates, fused white corundum (≤0.045 mm), SiC (≤0.075 mm), α-Al₂O₃ (≤10 µm), pitch sphere, SiO₂ micropowder (≤2 µm) as a matrix, and silica sol as a binder. Then, the effect of the addition of sillimanite group minerals on the mechanical properties of Al₂O₃-SiC-C gunning materials was characterized. The results indicate that kyanite requires the lowest temperature for mullitization compared to andalusite and sillimanite. The mullitization process involves the migration of Al³⁺ and Si⁴⁺, resulting in a decrease in the lattice constant of sillimanite group minerals followed by the production of mullite and SiO₂. Incorporating sillimanite group minerals into Al₂O₃-SiC-C gunning materials effectively controls their linear change rate after firing while enhancing their mechanical properties. Notably, the addition of kyanite yields superior performance in Al₂O₃-SiC-C gunning materials.

Traditional abradable seal coatings (ASCs) face huge challenges for the requirements of next-generation aero engines due to high inlet temperature (>1300°C) and non-matched coefficients of thermal expansion for SiC based composites. Herein, a novel Yb₂Si₂O₇ seal coating was developed to meet the demands of high-temperature resistance and match the coefficient of thermal expansion with SiC. The prepared Yb₂Si₂O₇ seal coating has excellent properties, including high porosity of 35.5%–23.3%, moderate hardness of 77.9–82.5 HR15Y, and high bond strength of 7.8–9.0 MPa. Adjusting spray current could effectively control the thickness, porosity, and hardness of the coating. More importantly, the coating also has good erosion resistance. Our results show that the fabricated porous Yb₂Si₂O₇ coating would have promising applications in the field of high-temperature ASCs.

Ceramic refractory bubbling devices may be applied in the steel ladle to induce the flotation of non-metallic inclusions to the slag phase. These inclusions have many origins along the steelmaking process and induce a detrimental effect on the mechanical properties of these metals. Therefore, the design of high-performance ceramic plugs relies on understanding the fundamentals of non-metallic inclusions captured by the gas bubbles. This study investigated the flotation dynamics of hydrophobic and hydrophilic hollow glass particles through experimentation using a water model and quantifying the particle concentration via light scattering. Both types of particles exhibited a comparable natural flotation removal rate, whereas a 40% increase for hydrophobic particles was observed when introducing 1.1 mm bubbles (at 25 NL/h) enhancing the efficiency from 43.1% to 65.2%. For hydrophilic particles, the efficiency increased from 59.1% to 86.2% when bubbles were injected into the system, whereas the removal rate decreased by 2.1-fold. The consequence of the practice of inert gas purging to remove non-metallic inclusions is also discussed.

This work investigates the material extrusion-based additive manufacturing (AM) process chain of a pure alumina-based oxide ceramic matrix composite, starting from material selection, large-scale compounding to pellets, the AM process itself, debinding and sintering as well as microstructural and mechanical characterization. The compounded pellets have a volume share of 50% binder (polyvinyl butyral [PVB], polyethylene glycol [PEG], and stearic acid) and 50% alumina (Al₂O₃, alumina powder, and Nextel 610 alumina fibers) with an aimed fiber volume share of 40% after sintering. The material is compounded on an industrial scale with approximately 10 kg/h and the material extrusion-based AM process reaches speeds of up to 1000 mm/s. A variation of the feed rate leads to a significant increase in surface roughness and an increase in mass of 30%, in thickness of 12% and in width of 25%. The flexural behavior in the four-point-bending test can be described by a fast first peak and reaching higher flexural strength after the first crack subsequent with averages of 23.8 ± 3.6 MPa below .1% elongation. The fracture surfaces show the expected failure mechanisms like pull-out and crack deflection. The resulting fiber length in the printed samples is 140 µm in average.