International Journal of Applied Ceramic Technology最新文献

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.

This study provides the first ever investigation of the influence of nickel, copper, and zinc additives upon magnesium oxide powders when synthesized via sol–gel autocombustion. In order to assess the resulting properties of the samples affected by the addition of Ni, Cu, and Zn ions, a number of investigative techniques were employed, among which were X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)–visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL) spectroscopy, and vibrating sample magnetometry (VSM). From XRD results, it was apparent that when Ni, Cu, and Zn ions are added to MgO, cubic solid solutions of NiMgO, CuMgO, and ZnMgO are created. UV-DRS analysis showed significantly improved absorption levels in the samples that were optimally modified compared to the pure sample across UV, visible, and infrared spectral observations. Analysis of the photocatalytic activity exhibited by the synthesized samples was performed by considering the decomposition under sunlight of rhodamine B, methylene blue, methyl orange, and methyl red. The degradation under sunlight for these organic dyes was shown to be superior to that of pure MgO, achieving a range of 91%–95% in just 150 min.

Polymer–ceramic composites are widely used in refractory cables. The ceramic fillers provide high temperature and fire resistance, while the polymer matrix provides flexibility and improved electrical insulation. The properties of the polymer–ceramic composites are determined by the ceramization-forming properties of the corresponding ceramifying powders. Properties such as shrinkage, density, and porosity were characterized to compare the effects of different contents of glass powder. The sintering activation energy was calculated using the logarithmic relationship between shrinkage and holding time. The microstructure, cross-section, and crystalline phases were investigated by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) to explore the ceramization process of sericite ceramifying powder. The ceramization process of ceramifying powder is proposed. The results show that during low-temperature sintering, the glass powder and muscovite phases melt and partially transform into α-quartz and albite low during cooling down.

Silica gel-modified hydratable magnesium carboxylate (HMC) is used as the binder for refractory castables. The mechanical strength and thermal shock resistance of HMC bonded and silica gel-modified HMC-bonded castables were compared. When the HMC/silica gel mass ratio is 2, the cold modulus of rupture, the hot modulus of rupture, the residual strength ratio after three-times water quenching tests, and the matrix-specific fracture energy of the castables were increased by 300%, 124%, 44.7%, and 132%, respectively, compared with HMC-bonded castables. The characterization of microstructure evolution of silica gel-modified HMC-bonded castables indicated that a small amount of liquid phase generated is conducive to improving the high-temperature mechanical properties. The in situ alumina-rich spinel and needle-like mullite toughened the matrix and enhanced the thermal shock resistance of the castables by “microcrack generation” and “preventing crack propagation” mechanisms.

The corrosion behavior of the TiN monolayer and CrN/TiN multilayer coatings deposited via cathodic arc evaporation physical vapor deposition (CAE-PVD) on the Ti–6Al–4V substrates were evaluated in Ringer's and Hank's physiological saline electrolytes. XRD (x-ray diffractometry) and scanning electron microscopy (SEM) analysis were used to characterize the coatings. The corrosion behavior of coatings was assessed by impedance spectroscopy and potentiodynamic polarization techniques. The results showed that the corrosion resistance of coatings was increased in the order of TiN-Ringer's < TiN-Hank's < CrN/TiN-Ringer's < CrN/TiN-Hank's. Therefore, it can be concluded that the CrN/TiN coating, due to having a large number of interfaces and a smoother surface with fewer macroparticles and pinholes, is more efficient in raising the corrosion resistance properties of titanium than TiN monolayer coating. Moreover, it was observed that Ringer's solution is a more severe environment than Hank's solution. Both coatings, because of the precipitation of a protective corrosion products layer on their surface, showed an enhancement in corrosion resistance with increasing the immersion time from 1 to 14 days in Hank's. The results suggest TiN monolayer and CrN/TiN multilayer coatings as promising candidates for biomedical applications.

This study presents an easy method for synthesizing ultrafine Ni_xFe_1–xFe₂O₄ nanoparticles with adjustable composition (x = 0–.8), followed by their stabilization into ferrofluids. Structural identification of the crystalline structure, lattice points, and grain boundaries from the broadened diffraction peaks reveal an average crystalline size of the nanoparticles as 10–16.5 nm. Transmission electron microscopy images reveal spherical magnetite nanoparticles with a particle size ranging from 6 to 13 nm, consistent with diffraction studies. In ferrofluids, the Ni_xFe_1–xFe₂O₄ nanoparticles are stabilized in kerosene with oleic acid, a surfactant. Absorbance data of the ferrofluids is seen in the 200–400 nm wavelength region of UV–vis spectra. The magnetic properties of the samples are probed using a Superconducting Quantum Interference Device. The synthesized samples exhibit superparamagnetic behavior at room temperature (300 K). The saturation magnetization of the samples decreases with an increase in Ni composition (x = 0–.8), ranging from 54 to 28 emu/g. This study explores the magnetic and magneto-optical properties of Ni_xFe_1–xFe₂O₄ ferrofluids. Magneto-viscosity of ferrofluids is also studied, and the final application of such ferrofluids in data storage, catalysis, and biomedical applications is discussed.