Boletin de la Sociedad Espanola de Ceramica y Vidrio最新文献

Superficial cracks are one of the common defects in the manufacturing of traditional ceramic tiles. Such defects do not only damage the appearance of the product, but also affect their mechanical behavior. Understanding the correlation between superficial cracks and deflection is key for the traditional ceramic tile industry. However, the related bibliography is very rare, and its importance is systematically ignored during design and manufacturing. In this work, we investigate the impact of the location and size of superficial cracks over the deflection of traditional ceramic tiles. A technique based on FEA (finite element analysis) is validated through experimental data and used to undertake a statistical, parametric research. The study shows that location and depth of the defect have an exponential cross-correlation over deflection and could be characterized together through a single surface. On the contrary, the width and sharpening of the defect barely interfere.

A series of glasses with chemical composition (50−x−y) TeO₂–30ZnO–10YF₃–10NaF–xHo₂O₃–yYb₂O₃ (x = 0.5 and y = 0.5, 1.0, 3.0, 5.0 mol%) were prepared by melt-quenching procedure. The absorption spectra, excitation, down conversion emission spectra, up-conversion (UC) emission spectra and decay time measurements were analyzed. In down conversion, the visible emission transition intensity associated with ⁵F₄ → ⁵I₈ (547 nm), ⁵F₅ → ⁵I₈ (657 nm), and ⁵F₄ → ⁵I₇ (755 nm) of Ho³⁺ ions decreased with Yb³⁺ concentration due to the energy transfer (ET) process from Ho³⁺ to Yb³⁺ ions. In up-conversion, on exciting with 980 nm diode laser beam, we observed a strong green (543 nm) and red (657 nm) UC emissions, that refers to the energy level transitions; ⁵F₄ (⁵S₂) → ⁵I₈ and ⁵F₅ → ⁵I₈ of Ho³⁺. The influence of excitation power on UC intensities studies revealed that the population at ⁵F₄ (⁵S₂) and ⁵F₅ levels of Ho³⁺ ion occurs due to two-photon absorption process associated energy transfer from Yb³⁺ to Ho³⁺. The influence of Yb³⁺ doped concentration on UC was studied, and it is observed that both the green and red UC intensities improved significantly on increasing Yb³⁺ ions concentration.

The need for biodegradable bone graft biomaterials in orthopedic surgeries is more often each day due to the promotion of natural tissue regeneration. One option is calcium phosphate cements (CPC), that are also osseconductors. However, their low mechanical properties restrict their application to low mechanical requirement areas of the body. The CPC mechanical resistance depends on the entanglement grade of the calcium deficient hydroxyapatite (CDHA), one option to improve it is trough incorporation of nucleating agents (e.g., stoichiometrically hydroxyapatite). This work proposes the use of a biodegradable nucleating agent, as it is Type B carbonated Hydroxyapatite (CHA-B), to improve the CPC performance. It was formulated compositions of alpha tricalcium phosphate (α-TCP) with variations on the amount of CHA-B (0–5–10–15 wt.%). The compression resistance was evaluated and results indicated that 5% CHA-B increases the strength (7.8%) and the elastic modulus (6.16%), while the other additions diminished such values. Besides, the effect on the setting time, the in vitro degradation and in the physicochemical properties was determined through scanning electron microscopy, X-ray diffraction and infrared spectroscopy.

The nucleation and growth of ZnO nanorods by hydrothermal method onto seed layer deposited onto an ITO/PET substrate. Concentrations of 10 and 15 mM were used for the synthesis of the seed layer solution, as well as 10 and 15 mM for the hydrothermal treatment, it is noted that the entire process was carried out at low temperature (<100 °C). The synthesis of ZnO nanorods was carried out in two stages: (i) A nucleation process, using the sol–gel method to obtain a seed layer; and (ii) a growth process, using the hydrothermal process to promote the perpendicular growth of ZnO nanostructures. The X-ray diffraction (XRD) ZnO results revealed a preferential orientation along the (002) axis, with a wurtzite hexagonal structure. The crystallite size (27 nm) and Gibbs free energy of the films were calculated, which exhibited a minimum diameter for the nucleation of ZnO nanorods (22 and 30 nm of the core diameter). The thickness layer is between 200 and 500 nm. These results indicate that ZnO nanorods with an average diameter between 50 and 195 nm are obtained, oriented perpendicularly to the ITO/PET substrate, synthesized by a low temperature process. Their potential applications are in power generators and sensors.

The properties of BaO–CaO–Al₂O₃–SiO₂ (BCAS) glass seal materials reinforced with 5–30 wt.% glass fiber are investigated. The seals are prepared by solid mixing process. The microstructure and phase content of the samples are studied. Mechanical properties are investigated by Vickers micro-hardness, nano-indentation and compression tests. The thermal properties of the samples are evaluated by conducting a dilatometry analysis. The electrical conductivity and leak resistance of the seal materials are measured at high temperatures. Increasing the amount of glass fiber in the composite samples decreases the magnitude of the thermal expansion coefficient. It is found the addition of just 5 wt.% of glass fiber (GF5sample) increases the indentation fracture toughness of the seals by ∼280% without impairing other properties. It is also found that the GF5 sample has high electrical resistivity with the activation energy of 63.7 kJ/mol and very low leak rate of 1.7 × 10⁻⁴ sccm/cm at 750 °C.

The preparation of an aluminum-mesoporous A1-MCM-41 humidity control material (Al-MHCM) by hydrothermally synthesizing a mixture of thin-film transistor liquid crystal display (TFT-LCD) waste glass and sandblasting (SB) waste was studied. The product has a typical mesoporous structure, with a specific surface area of up to 1013 m²/g, the pore size distribution calculated is 3–4 nm, and the pore volume of 0.97 cm³/g. All the aluminum atoms of the product are in the form of tetrahedral aluminum in the framework, which confirms the successful synthesis of Al-MHCM. Results show that when the hydrothermal synthesis temperature is 105 °C, the product synthesized from a mixture with a Si/Al molar ratio of 41.8 exhibits excellent performance (91.45 m³/m³) in terms of the equilibrium moisture content and moisture adsorption capacity. The results confirm that the equilibrium moisture content of Al-MHCM is better than the rape straw concrete and hemp concrete (9.8–17.8 m³/m³), and that of a diatomite/ground calcium carbonate composite aterial (11.7 m³/m³). The research results are expected to provide a new technology for synthesizing TFT-LCD waste glass and SB waste into novel high value-added humidity control materials.

Lithium borate glasses doped with three transition metals: Ag, Cd and Zn were prepared with the melt-quenching method. Dopants concentrations were (Li₂B₄O₇)_(100−x) (Zn[NO₃]₂, CdN₂O₆, AgNO₃) (x = 0%, 1%, 5%). Doped glasses were analyzed and their shielding features were determined. The XRD measurements show the amorphous state of the glasses. Fluorescence analysis shows the characteristic emission of Ag, Cd and Zn and their enhancement is explained. UV–vis spectra were recorded in the interval 200–900 nm, and show the peaks belonging to the plasmon of the three transition metals. The optical energy band gaps were calculated using the Tauc's plot model; also, the refractive index was calculated. Additionally, density (ρ) and molar volume (V_m) were calculated as part of the characterization of the samples. In order to determine the shielding features against gamma-rays the mass attenuation coefficient (μ/ρ)(E), the half value layer (HVL(E)) and the Effective Atomic Number (Z_eff(E)) for photons from 0.015 to 15 MeV using the Phy-X program.

A novel method for obtaining ceramic (tricalcium phosphate, TCP) fibres with a small diameter (below 0.1 mm) is proposed and its potential use in the 3D printing of scaffolds for biomedical applications is explored. An ink consisting of a high solid content (40 vol%) ceramic slurry in a photocurable resin was prepared and extruded using near-field electrospinning. The influence of the electric potential, flow rate, and distance between tip and collector on the fabrication process in static mode were studied and the role played by unidirectional motion of the collector was also analyzed. A one order of magnitude reduction in the diameter of the jet to around 30 μm is demonstrated under static conditions, which increased to around 100 μm when collector was displaced. Continuous fibres were deposited but the slurry spread over the collector. The method was implemented on a DIW system, using in-flight UV light curing to prevent the spreading of the ink upon deposition. The feasibility of the strategy was demonstrated, although challenges remain for the optimization and control of the fabrication process. Nevertheless, these preliminary results suggest this could be a promising alternative to produce 3D ceramic scaffolds for biomedical applications with improved spatial resolution.

The effect of adding 0.1, 0.3, 0.6, 1.0, and 2.0 wt.% halloysite clay, which calcined and uncalcined form, was studied on the glossy opaque glaze hardness and mechanical properties. Since the most significant disadvantage of opaque glazes is low hardness, halloysite particles with higher toughness were added to glazes to increase this property. Since more stable halloysite tubes were obtained after the calcination process, both calcined and uncalcined halloysite additions were made to see the effect of calcination, and the obtained results were examined. Detailed technological, mechanical and microstructural characterization studies were done on glazed samples. In addition, the change in the melting behavior of the glaze and the glassy phase viscosity of the addition of halloysite was also examined and interpreted considering hot stage microscope analyses. Compared to standard glossy opaque glaze, almost all the halloysite added samples displayed similar optical properties but higher hardness, surface wear resistance, and fracture toughness values. Among the case studies, the 2% halloysite addition by weight (uncalcined and calcined form) showed the highest mechanical properties.