Open Ceramics最新文献

Global warming necessitates efficient new batteries, with Zn-O₂ batteries standing out due to their high theoretical energy density, safety, and long cycle life, making them ideal for large-scale use. However, their industrial application faces challenges such as rapid energy density decline after initial cycles, limited cathode efficiency, and high overpotential between discharge and charge. This study focuses on synthesizing and characterizing ceramic iron compounds as catalysts for the cathode of Zn-O₂ aqueous batteries. The findings revealed that obtained catalysts presented surface active areas beyond 220 m²/g after calcination at 800 °C, which removed organic templates. Various thermal treatments have been analysed to measure their impact on the final product. XRD, FTIR, and Raman spectroscopy confirmed sample nitridation, while SEM showed macro–meso-porosity. The electrochemical evaluation demonstrated a significant enhancement in the material's catalytic properties for ORR/OER in alkaline Zn-O2 batteries, surpassing 140 h of satable cyling with catalytic activity for ORR and OER. This improvement, coupled with optimized electrode design, resulted in a substantial increase in the batteries' operational life, achieving stable cycling for over 120 h.

In “London Underground” stations, a high concentration of dust particles containing organic and inorganic matter of varying chemical composition. “London underground dust” is created from train wheels and brakes grinding against steel tracks and collected in filtration systems. The experiment will focus on using “London Underground Dust” to colour the ceramic facing tiles intended for re-use in newly built London Underground stations. The phase composition, particle size distribution surface area, morphology, and thermal behavior of collected dust were studied by XRD, XRF, SEM-EDS, BET, heating microscopy, STA-MS, UV–VIS spectroscopy. The substrate tiles for glazing experiments were prepared from local London clay. The mixtures of glazes and collected or milled dust were sprayed on the substrate tile's surface, dried and finally fired at 1060 °C. The influence of used materials weight ratio and dust milling time were shown as crucial parameters to obtain optimal final glaze colour.

Zirconia is a ceramic material with fine properties for dental restorations, but the color of zirconia does not match natural teeth color. In this study, the effect of zirconia doped with different rare earth oxides on the color of denture manufactured by Digital Light Processing (DLP) method was investigated. Experimental results showed that the color of the ceramic parts after sintering could cover Vita 3D colorimetric plate for natural teeth, and the color accuracy was within 1.5 NBS. Meanwhile, the forming accuracy of the denture reached 67.7 μm, and the three-point bending strength was 520.32 ± 35.44–649.10 ± 42.31 MPa, which met the requirements of triple crown in dentistry. This study establishes a method to achieve colors of natural teeth using DLP technology, and the results of this study have important leading implications for the use of additive manufacturing technology to fabricate natural-color ceramic dentures for dental applications.

In manufacturing of UHTCMC components machining is often one of the ultimate process steps and have then important objectives, including dimensional tolerances and surface roughness. Additionally, the prevention of any damage to high-value components is very important. In this study, the machining of 0/90°-C/ZrB₂ composite is investigated to understand some fundamental mechanisms involved. Specifically, the material removal mechanisms of the heterogeneous and anisotropic material structure through scratch tests are explored. Grinding experiments are conducted to evaluate surface quality, measuring surface roughness and grinding forces. This allows an interpretation of machining induced damage mechanisms of UHTCMCs. 0/90°-C/ZrB₂ shows generally brittle removal mechanisms and influence of fiber cutting direction. Scratching depth and speed influences less on damage. This was also found in the grinding experiments, where roughness remains almost constant.

TiC features an interesting combination of mechanical properties, high-temperature resistance, and lightness, making it an excellent candidate for several applications in harsh environments. However, its sintering to obtain bulk components is extremely challenging. Herein, we show that titanium aluminide is a promising sintering aid for TiC (5, 10, and 20 vol% were investigated). The aluminide allows the formation of a nearly fully dense component at 1350 °C by spark plasma sintering under 80 MPa. The aluminide forms a grain boundary secondary phase that promotes the Ti diffusion: Ti from TiC can be dissolved within the TiAl_y at the neck center and precipitate at the neck surface, while C can easily diffuse through the TiC lattice. Higher temperatures cause the extrusion of the aluminide out of the SPS die and its reaction with oxygen impurities. The final microstructure is constituted by nearly pure TiC with isolated alumina pockets at the triple points.

Y₂O₃ transparent ceramics with different amounts of ZrO₂ were obtained by reactive vacuum sintering at a relatively low temperature of 1735 °C for 22 h. The influence of ZrO₂ concentration within the 0–15 mol.% range on the microstructure, phase composition, microhardness, and optical properties of ceramics in the visible and IR ranges was investigated. SEM and XRD results indicate the absence of secondary phases in the studied concentration range, indicating the formation of single-phase solid solutions. It was shown that doping by ZrO₂ considerably decreases the average grain size of ceramics, while microhardness has the opposite behaviour. 15 mol.% ZrO₂-doped Y₂O₃ ceramics demonstrated the highest transmittance in the visible wavelength range. On the other hand, 5 and 7 mol.% ZrO₂-doped Y₂O₃ could be considered promising materials for the first atmospheric window (3–5 μm).

Magneto-optical and thermo-optical characteristics of transparent Tb₂Ti₂O₇ ceramics were investigated. The dependence of the index of refraction on the wavelength in the 0.29–2 μm range, the wavelength and temperature dependence of the Verdet constant, as well as the dependence of thermally induced depolarization on laser radiation power were measured. The value of the Verdet constant in Tb₂Ti₂O₇ surpasses that in Tb₃Ga₅O₁₂ by more than 1.68 times. The thermo-optical characteristic Q_eff was estimated to be (1.8–3.7)∙10⁻⁸ 1/K, which is record small compared to Q_eff of the known magneto-optical materials. The small value of Q_eff makes Tb₂Ti₂O₇ a highly promising magneto-optical material for Faraday isolators and rotators for high average power lasers.

In this research, B₄C-TiB₂ composites were successfully fabricated via the spark plasma sintering method. First, the TiB₂ source effect on the B₄C-TiB₂ composites was investigated using commercially available TiB₂ and in-house synthesized TiB₂. Subsequently, the effect of Si/B co-doped B₄C on composite ceramics was studied, followed by examining the samples' microstructure and elastic and mechanical properties. The results showed that B₄C-TiB₂ composites made with in-house TiB₂ powder obtained higher relative density and more desirable elastic and mechanical properties than samples made with commercial TiB₂. In-house TiB₂ and Si/B-B₄C composites provided more properties improvement overall. The elastic modulus, Vickers hardness, and fracture toughness values of Si/B co-doped samples were 493 GPa, 30.09 ± 1.97 GPa, and 4.31 ± 0.74 MPa m^1/2, respectively. Additionally, the amorphization of the TiB₂-B₄C composite decreased with Si/B co-doping.

The aim of this work was to gain an initial impression of the surface quality that can be achieved with additively manufactured ceramic components. For this purpose, an assessment body was generated, which has partially double-curved surfaces that can be scanned using a confocal microscope. After manufacturing using Vat Photopolymerization for ceramic components (CerAM VPP) with a commercial alumina suspension (Lithalox 350, Lithoz, Vienna, AUT) and thermal processing, the respective surface was measured at four different geometric areas. For evaluation, line sections were extracted to calculate R_a values as well as to determine S_a values for surfaces. R_a and S_a values were determined in all areas, reaching always values below 2.5 μm. The surface quality is therefore an order of magnitude lower than that of typical metallic AM components.