International Journal of Applied Ceramic Technology最新文献

High-temperature oxidation (1050°C) of Sr_.9(Zr_.9Yb_.05Y_.05)O_2.85 (SZYY) thermal barrier coatings (TBCs) by suspension plasma spraying (SPS) and growth behavior of thermally grown oxide (TGO) were investigated. When the TBCs were exposed to high temperature for a period of time (∼5 h), the BC oxidized and TGO inevitably formed between the bond coating (BC) and the ceramic top coating (TC). The high-temperature oxidation behavior of the BC is generally manifested as the growth of TGO, which has four specific stages as follows: (1) formative oxidation stage (0‒10 h), (2) rapid oxidation stage (10‒50 h), (3) stable oxidation stage (50‒100 h), and (4) complex oxidation stage (100‒200 h). The main component of early TGO is α-Al₂O₃. It has a very low oxygen ion diffusivity and provides an excellent diffusion barrier, which has a positive effect on preventing further BC oxidation. However, as the heat treatment time increased, the Al consumption and the formation of a CNS layer (NiO, Co₃O₄, and spinel) in the BC eventually led to coating failure. The working life of TBCs can be improved by improving the ceramic TC structure and the Al content of BC. SZYY-TBCs have certain potential application value.

Direct ink writing (DIW) technology supersedes traditional mold-based forming methods, significantly enhancing the fabrication of personalized and customized products with complex structures. This technology particularly excels in achieving precise control over the porosity of porous constructs. This study employs inorganic Al₂O₃ as raw material, sodium hexametaphosphate as dispersing agent, and inorganic SiO₂ micropowder as binding medium to fabricate lattice porous structures. One challenge encountered is the viscoelastic behavior of the extruded filament. When spanning the unsupported segments of the lower layer, the upper extruded filaments are susceptible to deflection or collapse, adversely affecting the porosity and dimensional fidelity of the final specimens. Experimental results revealed that a larger span and smaller modulus will cause the extruded filament to be more prone to deformation at the midpoint. The introduction of 2 wt% polyethylene glycol as a plasticizer mitigates this issue, ensuring nondeflection of the extruded filaments at a span of 6 mm. The deflection model for the extruded filament about span and modulus identifies the minimum modulus necessary to prevent or minimize deflection under given spans, which closely approximates our experimental findings, offering a valuable framework for guiding the production of high-precision, porosity-controlled porous structures.

To achieve the repeatability of aerospace thermal components, C/TaC‒SiC composites were fabricated. Cycle ablation and bending tests were carried out. After 3 × 60 s of ablation beyond 2100°C, the mechanical property retention rate was 80.9%. Interestingly, a reaction similar to “ouroboros ring,” in which the cyclic reactions of “TaC being oxidized to Ta₂O₅ and Ta₂O₅ being reduced to TaC,” occurred in the central ablation region of C/TaC‒SiC composites. On the one hand, the continuous generation of TaC could prevent liquid state Ta₂O₅ from being blown off central ablation region, playing a similar role in “water and soil conservation.” On the other hand, liquid Ta₂O₅ covered the surface of C/TaC‒SiC composites during ablation process, contributing to block the inward permeation of oxidized gases. In addition, novel “Grotto” structures were detected in the transitional ablation region of C/TaC‒SiC composites. The formation reason of the “Grotto” structure has also been discussed.

In the present study, SrTiO₃ was selected to enhance the multiferroic characteristics of Bi_0.88Sm_0.12FeO₃ (BSF) ceramics. With increasing SrTiO₃ content, the principal phase of BSF ceramic transitions from rhombohedral R3c to Pna2₁. Through DSC and dielectric analysis, it was observed that both the Curie temperature and Néel temperature decreased proportionally with the augmentation of SrTiO₃ content. When x = .1, the optimal ferroelectric performance is achieved, and the highest remanent polarization value is 55.47 µC/cm², significantly surpassing that of BSF ceramics. Moreover, the PFM test results showed that as the substitution content increased, the domains in the BSF ceramic gradually transformed from normal ferroelectric domains to polar nanomicro-domains. Magnetic and magnetoelectric results show that when x = .1, the best magnetic properties are obtained, M_r = 59.7 emu/mol. The magnetoelectric coefficient α_ME initially increased and then decreased with the increasing SrTiO₃ content, reaching its optimum magnetoelectric properties at x = .1, where α_ME = .47 mV cm^–1 Oe^–1. In summary, when the substitution amount of SrTiO₃ reaches 10%, the ferroelectric, magnetic, and magnetoelectric properties of BSF ceramics are significantly improved.

Titania nanotube (NT) arrays have been widely used as cell-supporting matrices. However, cells are always seeded on the porous surface of the NT array and have very limited interactions with each individual NT in the array. In this study, titania hollow microtubes (HMTs) were synthesized via a gelatin-template sol-gel route and then utilized as free-standing cell-supporting matrices for the first time. The resultant titania HMTs were studied by field emission scanning electron microscopy, energy-dispersed spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. Each HMT was composed of rutile-type titania nanoparticles with diameters of 50–100 nm and a diameter of 50–100 µm. The results from a leaching liquor assay demonstrated good biocompatibility of titania HMTs. Each HMT has been demonstrated to independently support the adhesion and proliferation of osteoblast MC3T3-E1 cells. For comparison, titania NT arrays, not independent titania NT, only supported the adhesion of cells on their porous surface. Thus, the resultant titania HMTs are applicable to free-standing and biocompatible cell-supporting matrices.

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.