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

This study is part of the research line that sees it necessary to develop materials that are alternatives for Portland cement (PC), using industrial by-products such as blast furnace slag and fly ash. This line arises because of the serious environmental consequences suffered by our planet throughout many decades, which have led the cement industry to reduce the amount of CO₂ emitted in the production of PC, since it is a highly polluting process. The chemical and physical properties of the materials were studied. In this way, the study of the thermal properties is interesting to test the feasibility of the mortars to use them as solid media to storage thermal energy, since most of the research focus on the thermal properties of concrete is oriented toward fire resistance. Storing solar thermal energy improves the operation of solar power thermal plants. It is being studied that the use of concrete (composed of PC) contributes efficiently to concentrated solar power (CSP) technology. To avoid the use of PC due to environmental concerns, alkaline-activated mortars are manufactured with blast furnace slag using alkaline solutions such as sodium hydroxide (NaOH) and commercial sodium silicate (SiO₂/Na₂O = 0.8), as well as hybrid mortars using 80% fly ash or blast furnace slag and 20% PC. After experimental analysis and a simulation to measure the conduction within the mortars through a commercial Computational Fluid Dynamic software (CFD, ANSYS Fluent), it can be concluded that the mechanical and thermal properties of most of the alternative mortars manufactured in this study are better than the ones obtained in the PC. Most notably, the slag alkaline-activated mortar increases those properties significantly.

In recent years, the existence of a dense pottery production in the Tagus estuary during the Iron Age, and specifically in the Lisbon area, has been highlighted. This was part of a process of economic intensification stimulated by the presence of phoenician traders. One of the most conspicuous products are amphorae containers, recently identified and classified from specimens recorded in different archaeological excavations. Imported amphorae, mostly from the south of the Iberian Peninsula, have also been found in the same contexts.

The aim of the present work is to further characterise these productions, both local and imported, through the analysis of 14 samples from excavations carried out on the slopes of the hill of Castelo de São Jorge in Lisbon. For this purpose, a petrographic study has been carried out through thin sections, as well as chemical (XRF) and mineralogical (XRD) analyses of all the sherds. A cluster analysis was applied to chemical data. In conclusion, a high degree of coincidence is observed in the results of these 3 analyses and their coherence with the previous geographical and typological ascription, proposed on the basis of the macroscopic examination.

A monolithic porous composite was synthesized by sol–gel process, containing the maximum and significant amount of bentonite that allows its use as a filter bed in aqueous effluents treatment. This process is able to apply on an industrial scale.

The bentonite used was an efficient adsorbent for various contaminant molecules in aqueous media when is operated in a batch stirred tank, but presents difficulty in the separation stage of suspended particles. In this laboratory-scale work, cylindrical monoliths of 9 cm length by 2 cm diameter were made that can be used as a filter bed. The primary composite, silica-resin, was prepared by the sol–gel precursor mixture of the partially hydrolyzed tetraethylorthosilicate and a phenol-formaldehyde resin. Bentonite was added to the pre-gelling, obtaining the silica-resin-bentonite composite, made up the gel which is then dried and cured at 270 °C. The different composites mineralogical and structurally were evaluated. The preliminary performance of the developed bentonite filter bed showed almost 90% adsorption of diphenylamine, a commercial agrochemical widely used as anti-antiscaldant in postharvest treatment of fruit, and showed that the bentonite conserves its adsorption capacity and controls the swelling of the interlayer space which encourages further research studies applied to water treatment.

Tin oxide is one of the most extensively studied semiconductor materials due to its broad field of applications. On the one hand, its high conductivity and its corrosion resistance are the most remarkable properties. Therefore, one of the most developed uses in the recent decades has been as ceramic electrode for electrooxidation process. On the other hand, its poor sinterability hinders a broader use. As a result, the use of advanced techniques or sintering aids for obtaining low-porosity specimens is necessary. So far, many additives have been studied, CaCO₃, Co₃O₄, Nb₂O₅ or MnO₂, among others. In the present work, the sintering behaviour of SnO₂-based powder, containing Li₂CO₃ as a sintering aid, which generates a liquid phase, has been analysed, since it is one of the additives that has been studied to a lesser extent. The effect of the amount of sintering aid just like the thermal treatment parameters (maximum temperature, heating rate and soaking time) on volumetric contraction's evolution has been studied through a factorial experiment designs 2ⁿ. The results show that an amount of lithium carbonate greater than 1 mol.% is unfavourable to densification. With regards to the thermal cycle's parameters, it is advisable to have thermal treatments at high temperatures (1300 °C) with moderate soaking times (1 h), as maximum temperatures have the biggest influence on the densification followed by soaking time while the heating rate has a lesser influence. Under these conditions, a microstructure of closed and rounded pores is obtained, in which a residual phase is enclosed, but the small proportion of which prevents its characterisation.

Al-doped zinc oxide (ZnO) films were deposited on glass substrates by radio frequency magnetron sputtering using a sintered target of nanoparticles synthesized by sol–gel. The films were characterized using X-ray diffraction, scanning electron microscopy, the four-point probe method for resistivity, energy dispersive X-ray spectroscopy and photoluminescence. The X-ray diffraction patterns showed a hexagonal structure corresponding to the wurtzite phase for all the films, nanoparticles, and sintered targets. The films deposited by sputtering showed a highly preferred orientation to the (002) plane. These films were compared structurally and electrically to those deposited by the sol–gel method. Photoluminescence spectra show a decrease in intensity due to the reduction of defects by the incorporation of Al as dopant in the ZnO films deposited by the both methods (sol–gel and sputtering). The Al-doped ZnO films deposited by sputtering reached resistivity of 0.1 Ω cm and those deposited by sol–gel reached a resistivity of 1.24 Ω cm. The physical properties of these films show potential for application in devices like sensors and biosensors.

In the present work, argyrodite Li₆PS₅Cl sulfide solid electrolyte is prepared by a liquid phase process, consisting of two steps: (1) suspension-reaction under the ultrasonication of Li₂S, P₂S₅, and LiCl precursors in acetonitrile and, (2) dissolution-precipitation involving the addition of ethanol/acetonitrile and solvents removal by heating at 180 °C. The effect of the addition of a nonionic surfactant on the properties of the sulfide solid electrolyte is also studied. The synthesis process allows to obtain Li₆PS₅Cl argyrodite solid electrolyte with high ionic conductivity of 2.0 × 10⁻⁴ S cm⁻¹, the low activation energy of 0.22 eV, and electrochemical stability up to 5 V (vs. Li). A regular particle distribution with a size smaller than 1 μm is obtained by the addition of the surfactant.

The sintering behaviour of a pyrophyllite clay has been investigated. The mineralogical composition by X-ray diffraction (XRD) of this sample was ∼35 wt.% pyrophyllite, ∼25 wt.% sericite/illite, ∼15 wt.% kaolinite and ∼20 wt.% quartz. The chemical composition was consistent with these results, with a total flux content of 4.18 wt.%. Prismatic bars were prepared by dry pressing using this sample and fired in the range 800–1500 °C with 0.5–5 h of soaking times. Sintering diagrams were obtained using the results of linear firing shrinkage, water absorption capacity, bulk density and apparent porosity determined in the ceramic bodies as a function of firing temperatures. It was found a trend of slight variations of bulk density values firing in the range 1000–1150 °C, with marked decreases of these values for these bodies fired at 1200 °C and 1300 °C. The temperature of maximum bulk density was determined as ∼1200 °C and the vitrification temperature was ∼1300 °C where the apparent porosity becomes almost zero. The vitrification process of the pyrophyllite clay sample was investigated using a method previously described in the literature, which considered an Arrhenius approach under isothermal conditions and a first order kinetic. It was determined an activation energy (E_a) of ∼45 kJ/mol with a linear correlation coefficient of 0.998. The relative rates of vitrification were calculated. It was found that the contribution of vitrification due to the heating was relatively small compared to the vitrification during soaking. Mullite and quartz are forming the ceramic bodies besides a vitreous or glassy phase. The thermally treated pyrophyllite clay showed a dense network of rod-shaped and elongated needle-like crystals, being characteristic features of mullite as a dense felt. The vitrification rate equation, as deduced in this study by first time, can be a useful tool to estimate the optimum firing conditions of the pyrophyllite clays applied as ceramic raw materials.

The transparent relaxor ferroelectric ceramics of the system lanthanum modified lead magnesium niobate (PLMN-13PT) have been investigated for a variety of electro-optic, properties; good electro-optic switching times and modest half-wave voltages. In this work, the dependence of microstructural, structural, dielectrical, optical, and electro-optical properties in function of Rare Earth (RE = Tm³⁺, Nd³⁺, Yb³⁺, Er³⁺ and Ho³⁺) has been reported. PLMN-13PT:RE with excellent properties were obtained, highlighting the electrical, optical, and electrooptical properties, suitable for the fabrication of multifunctional devices. The most prominent or important feature is the largest quadratic Electro-optic coefficient achieved ((9.37 ± 0.39) × 10⁻¹⁶ m²/V²) corresponding to PLMN-13PT:Ho transparent ceramics. This result in addition to the electrical and photoluminescence properties becomes a promising alternative to building multifunctional devices.