International Journal of Applied Ceramic Technology最新文献

Tin oxide (SnO₂) is one of the important semiconductors used in the application of solar cells because of its chemical–mechanical stability and wide band gap. These properties are very important for the performance development and photoanode optimization of a dye-sensitized solar cell (DSSC). However, the low conduction band value of SnO₂ reduces the photovoltaic efficiency, which limits the application of DSSC. Therefore, the doping strategy was used to increase the sensitivity to the visible light spectrum and change the light absorption properties of SnO₂. In this paper, pure SnO₂, Ag/SnO₂, Pt/SnO_2, and Pt/Ag/SnO₂ nanoparticles were synthesized at the nanoscale by a simple chemical sol–gel method. To characterize the structure, morphological/chemical properties, optical properties, and surface properties of the synthesized SnO₂ nanoparticles, X-Ray Diffraction (XRD), ultraviolet–visible, Brunauer–Emmett–Teller, Scanning Electron Microscopy (SEM)/Energy Dispersive X-Ray Spectroscopy (EDX), Transmission Electron Microscopy (TEM), and particle size analysis were respectively used. XRD results showed that the crystal sizes varied between 8.8 and 12.2 nm depending on the doping. Doping processes resulted in reductions in particle sizes. Optical studies resulted in decreases in the band gap with the doping process. The conclusions obtained have shown that Ag doping, and Pt–Ag co-doping can be promising for use as photoanode materials in semiconductor technology and especially in DSSC applications.

In recent years, catalytic degradation driven by mechanical-energy tribocatalysis has gained much attention. Point defects play very important on the catalytic activity of ferroelectric oxides. In this study, we focus on the influence of oxygen vacancies on the catalyst performance of ferroelectric oxide KSr₂Nb₄TaO₁₅ (KSNT) with a tetragonal tungsten bronze structure. The concentration of oxygen vacancies is modified by sintering atmosphere. The KSNT sintered in N₂ atmosphere exhibits the best tribocatalytic degradation efficiency of 96.7% within 2 h for degradation rhodamine B due to high concentration of oxygen vacancies. The excellent degradation efficiency is attributed to the defect energy level of KSNT and high electron–hole separation efficiency. This work reveals the relationship between oxygen vacancies and tribocatalysis efficiency, which is helpful to design and modify the new ferroelectric oxides for tribocatalysis.

Low-temperature densification of alumina using calcium vanadate (CaV₂O₆, CV) having a similar dielectric constant as a liquid-forming additive has been studied. The alumina‒CV composites containing 20‒40 vol.% CV achieve ∼94% of theoretical density at low temperatures of 1100°C‒900°C by liquid-phase sintering. A reduction in the average size of grains from .87 to .42 µm with a surge in CV amount from 20 to 40 vol.% is observed. The permittivity decreases from 9.2 to 8.90, and the dielectric loss increases from 2.154 × 10^‒3 to 4.761 × 10^‒3 when the amount of CV in the alumina‒CV composite rises from 20 to 40 vol.%. The temperature coefficient of resonance frequency, thermal expansion coefficient, and thermal conductivity of the alumina‒CV composites are observed in the ranges of ‒54 to ‒72 ppm °C^‒1, 6.94‒7.32 ppm °C^‒1, and 13.78‒8.02 W m^‒1 K^‒1, respectively. The compatibility of the composites with Ag for low-temperature co-fired ceramics (LTCC) application is established through co-sintering and energy-Dispersive X-ray spectroscopy line spectra analysis. The low-temperature densification, acceptable range of dielectric and thermal properties, and silver compatibility make the alumina‒CV composite a candidate for LTCC application.

Silicon carbide (SiC) is a useful high temperature ceramic due to its excellent mechanical properties and oxidation resistance. In this study, monolithic SiC and chopped carbon fiber reinforced (C_f)/SiC ceramic matrix composites (CMCs) were additively manufactured via direct ink writing (DIW). Samples employing five different print paths were prepared from SiC and 10 vol.% C_f/SiC inks. All parts were pressurelessly sintered, with relative densities of 96% measured for samples prepared from both inks. Electron and optical microscopy were used to show a high degree of fiber alignment parallel to the direction of the print. Thus, CMC architectures consistent with the print paths were created when printing the 10 vol.% C_f/SiC inks. Characteristic flexure strengths for monolithic SiC and 10 vol.% C_f/SiC CMC samples were the same for the 0° print path, measuring 360–375 MPa. Fiber pullout was observed on the fracture surface of the 10 vol.% C_f/SiC CMCs. The Weibull modulus for the 10 vol.% C_f/SiC CMC samples (10.7) was greater than the monolithic SiC samples (7.4); the trend of fibers narrowing the distribution of failure strengths was consistent for the other print paths investigated.

In the present work, the sintering of bismuth germanate through hot pressing and the improvement of scintillator performance were investigated. The linear shrinkage, crystalline structure, microstructure, transparency degree, and radioluminescence (RL) were studied as functions of the sintering pressure. X-ray diffraction revealed that the samples were predominantly composed of the Bi₄Ge₃O₁₂ phase, accompanied by small amounts of Bi₁₂GeO₂₀, with concentrations varying according to the sintering parameters. These concentrations were quantified through Rietveld refinement, which also indicated a tendency for the cell parameters to shrink as the sintering pressure increased. The microstructure of the ceramic pellets produced under varying hot-pressing parameters was investigated using scanning electron microscopy (SEM), revealing that while the grain size was preserved, the porosity and grain boundary thickness were reduced by the hot pressing, forming a quasicontinuum in some areas of the sample. The RL of all the samples exhibited a green color, with a maximum at 540 nm, ascribed to the transitions from the ³P_0,1,2¹P₁ excited states to the fundamental ¹S₀ state of the Bi³⁺ ions. For samples sintered under a pressure of .18 MPa, the enhancement in the optical transmittance, accompanied by a 61.36% increase in light output at the maximum wavelength, was observed.

According to the characteristics of the internal damage of the C_f/SiC composite material after the lightning strike, this article establishes a high-energy ultrasonic excitation, reception, and high-resolution ultrasonic testing model, achieving high-energy and high-resolution ultrasound C-scan detection of C_f/SiC composite material samples after lightning strikes, and combining digital X-ray and computed tomography methods for damage analysis. When the lightning energy is gradually increased, the lightning stratified damage will occur inside the sample, and the delamination damage area reaches the maximum value of 25182 mm² at the lightning energy of S4. Subsequently, as the energy increases, significant needle-like damage is generated at the needle-stitched area inside the sample, and the area of delamination damage gradually decreases. When the energy continues to increase to the lightning strike energy of S6, as the energy increases, the number of needle-like damage in the sample continues to grow, and penetrating injury appears at the needle suture site. At S8, the maximum number of needle-like lightning damage occurred, with 53 damage points and a total volume of 256.86 mm³, respectively. Through comprehensive analysis, C_f/SiC has excellent resistance to lightning damage, but the needle-stitched carbon fiber in the thickness direction significantly reduces its resistance to lightning penetration.

In this paper, we prepared Al₂O₃–ZrO₂–SiB₆ composite ceramics with excellent performance by introducing the second-phase high-strength healing agent SiB₆ in zirconia-toughened alumina system, artificially created cracks using Vickers hardness tester, investigated the effects of heat treatment temperature (600–1200°C) and time (0–300 min) on the microscopic morphology and bending strength of the ceramics, revealed the healing mechanism, and studied the oxidation resistance properties. It was found that the healing effect was better at heat treatment of 90 min at 700°C and 60 min at 800°C, and the flexural strength was restored to more than 95% of that of the smooth specimens in both cases. Crack repair was mainly achieved by the reaction of SiB₆, ZrB₂, and B₄C with O₂. Below 800°C, healing was mainly achieved by the reaction of SiB₆ and B₄C with O₂, and the generated B₂O₃ and SiO₂ migrated toward the crack to repair it. When the healing temperature is higher than 800°C, ZrB₂ also reacts with oxygen to produce B₂O₃ and t-ZrO₂. It was found that the oxidation weight gain per unit area of the Al₂O₃–ZrO₂–SiB₆ ceramic composite at different temperatures was small, and it has excellent oxidation resistance.

A porous silicon carbide (SiC) ceramic filter was prepared at 1000°C using waste red mud (RM), SiC, pore-forming agent, and catalyst. The influence of sintering temperature, RM content, and pore former on the mechanical performance and the porosity of porous ceramics were investigated, and based on the result optimal processing parameters were selected. The air and water permeability tests were carried out at room temperature. The stability of the ceramic filter under thermal shock and chemical treatment was investigated and corroded samples were characterized. The ceramic was prepared using optimized processing parameters obtained with a flexural strength of 65.36 MPa at a porosity of 30.15 vol.% and demonstrated good performance in terms of pure water flux, oil, and turbidity removal efficiency from industrial wastewater. The filtration and permeation results indicated that the SiC filter prepared in this study is suitable for various applications, particularly in the remediation of oil-polluted water.

In this study, varying amounts of MnO₂ up to 5 wt.% were added to magnesium aluminate spinel (MA) bodies using a solid-state sintering method at 1200–1600°C. The effect of MnO₂ addition on the phase composition, microstructure, distribution of elements, and ionic valence of MA was investigated via X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results showed that Mg²⁺ ions in MA crystals were replaced by Mn²⁺ ions, resulting in the formation of the (Mg_1-xMn_x)Al₂O₄ solid solution. The distorted crystal structures promoted the sintering reactions, and the mechanical characteristics of MA were greatly improved by the solid solution strengthening process. When the additive amount of MnO₂ was 5 wt.% and the sintered temperature reached at 1600°C, excess manganese ions hardly dissolved into the lattice of MA. And these ions were only distributed at the grain boundaries of MgAl₂O₄, forming a “barrier” that hindered the migration and diffusion of particles, thereby suppressing the sintering process and weakening the mechanical strength of MA.

The present study intends to establish biphasic composite scaffolds containing polycaprolactone/hydroxyapatite (PCL/HA) and PCL/barium titanate (PCL/BT) layers with improved mechanical and biological properties by preserving HA and tuning BT contents. The porous piezo-biphasic scaffolds were fabricated, using extrusion three-dimensional printer technology, and on the basis of the scanning electron microscopy results, a relative porosity of 210–250 µm was created. The presence of BT phase in the biphasic scaffolds was confirmed by X-ray diffraction and Fourier transform infrared analyses. The printed biphasic composites demonstrate suitable mechanical strength compared to one containing only 35% PCL and 65% HA compositions, which had a strength of 2.5 MPa. However, the strength for 80% BT-incorporated biphasic composite was almost 13.5 times higher than that of monolithic specimen. The measured output voltages for the scaffolds after being subjected to an electric field affirmed that adding BT nanoparticles in biphasic composites leads to an increase in the output voltage that was lower compared to the monolithic scaffold. The piezo-biphasic scaffold containing 80% BT is found to possess the highest enhancement in cytocompatibility for MG63 cells with the survival rate of approximately 95%, rendering the PCL/HA–PCL/BT biphasic scaffolds promising candidates for bone regeneration.