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

Hybrid organic–inorganic aerogels are highly hydrophobic porous solids that avoid the brittleness and moisture adsorption of the standard silica aerogels. Superhydrophobic porous materials have attracted great interest because of their ability for selective absorption of organic solvents while repelling water, as excellent candidates for remediation techniques. This work shows a comparative of three drying procedures of DEDMS/TEOS (diethoxydimethylsilane/tetraethylorthosilicate) gels, namely, by supercritical CO₂, by supercritical ethanol, and dried at ambient conditions. Supercritical CO₂ and ambient drying produced superhydrophobic aerogels (θ > 150°), while supercritical ethanol drying produces denser aerogels with smaller both porous volume and specific surface area. Regarding the absorption of organic liquids, swelling is observed in all cases. Hexane had faster diffusion that obeyed Fick's law (∝t^0.5) whereas liquid polydimethylsiloxane exhibited slower non-Fickian diffusion process (∝tⁿ, n < 0.5).

This research focused on the synthesis and characterization of Faujasite-Na zeolites from fly ash (FA). The FA was subjected to pretreatment processes, washings with hydrochloric acid solutions and heat treatments at 700 °C for 3 h, to remove unburned carbon that would affect the synthetic process. After a fusion with NaOH at 550 °C for 3 h, the resulting material was disposed in a hydrothermal reactor at 100 °C for 12 h to obtain the corresponding zeolite. The products were characterized by XRD analysis, where quartz, mullite, sillimanite and lime phases were identified for the fly ash; quartz, mullite and in higher proportion Faujasite-Na for the synthesized material. The average size of the crystals of the fly ash and zeolite Faujasite-Na was 35.0 and 38.7 nm respectively, while the FTIR results allowed the identification of vibrational bands, characteristic of SiOSi and SiO bonds. The TGA-DTA analysis, allowed the identification of signals associated with exothermic and endothermic processes related to water removal and Faujasite-Na formation, while the EDX analysis coupled to SEM allowed verifying that the composition of the samples is consistent with the results sought and that the morphological characteristics validate the proposed methodology. The XRF results confirm the composition of the fly ash and the obtained Faujasite in accordance with some previous results and an improved composition. Surface area analyses (BET) showed that synthesized Faujasite possess an active area of 460 m² g⁻¹ while the fly ash for its physicochemical properties just an area of 6 m² g⁻¹. The overall results confirmed the efficiency of Faujasite-Na synthesis from FA by the proposed fusion-hydrothermal method.

Graphite–molybdenum–titanium powders prepared by colloidal processing technique were sintered by Spark Plasma Sintering (SPS). This material is proposed in this manuscript due to its potential interest as heat sink. The influence of the molybdenum content (2.5, 5.0 and 10.0 vol.%) on the thermal, electrical, and mechanical properties of the composite are studied to define the composite with the best properties. Thermal, electrical, and mechanical properties of the composite graphite–10 vol.% Mo–1 vol.% Ti (that are composites of graphite with molybdenum and titanium carbides after sintering) are significantly better than those of the composites with lower molybdenum contents (2.5 vol.% and 5 vol.%). This way, flexural strength, electrical conductivity, and thermal conductivity are 1.5, 7.8 and 18 times greater, respectively, than in the composite graphite–2.5 vol.% Mo–1 vol.% Ti. In the case of comparing with the composite graphite–5 vol.% Mo–1 vol.% Ti, flexural strength, electrical conductivity, and thermal conductivity are 1.2, 5.1 and 3.2 greater in the composite graphite–10 vol.% Mo–1 vol.% Ti, respectively.

Multicomponent oxide with pyrochlore structure (A₂B₂O₇), containing 7 different A-site cations and 3 B-site cations in equiatomic amounts, was synthesized. Powders with nominal composition (La_1/7Sm_1/7Nd_1/7Pr_1/7Y_1/7Gd_1/7Yb_1/7)₂(Sn_1/3Hf_1/3Zr_1/3)₂O₇ were fabricated through a reaction of metal nitrates (A-site) and metal chlorides (B-site) with sodium hydroxide during the solid state displacement reaction. Room temperature synthesis initially resulted in the obtainment of amorphous powders, which crystallized after subsequent calcination to form single crystalline compounds. Crystalline high-entropy ceramic powders formation took place at temperatures as low as 750 °C. During calcination, defective fluorite (F-A₂B₂O₇) and crystal pyrochlore (Py-A₂B₂O₇) structures coexist. A large number of cations induce the obtainment of stable high-entropy pyrochlores. Results showed that sintering at 1650 °C lead to pure crystalline single-phase pyrochlore formation. High-density ceramic, free of additives, was obtained after powders were compacted and subjected to pressureless sintering at 1650 °C. Multicomponent pyrochlore structure was investigated using the theoretical and experimental multi-methodological approach.

Silicon carbide-based composite ceramic is manufactured by one-stage selective laser sintering. The effect of the sintering parameters and raw materials on the sinterability of SiC based composite is studied. The optimization of the parameters is carried out. In a single stage of selective laser sintering, it is possible to achieve 87% relative density. The influence of particle size of feedstock, as well as BN and Y₂O₃ additives on the sinterability, mechanical and thermal properties of the samples are studied.

For composites that contain 10% BN, the thermal expansion coefficient increases from room temperature to 900 °C. The electrical resistivity decreases both in the room and at cryogenic temperature (−200 °C). The thermal conductivity and mechanical properties of BN-containing samples decrease as well. Yttrium oxide-containing samples show higher thermal conductivity and electrical resistivity than boron nitride-containing samples.

Magnesium phosphate cement (MPC) is an attractive alternative to Portland cement (PC) since it can also be obtained using by-products and wastes as raw materials. This research uses low-grade MgO (LG-MgO) as a magnesium source to obtain MPC, reducing CO₂ emissions related to MPC production. The obtained binder can be referred to as “sustainable MPC” (sust-MPC). Moreover, this investigation incorporates a by-product obtained in the aluminium recycling process, named PAVAL® (PV). The addition of PV (5, 17.5, and 35 wt.%) and water to solid (W/S) ratio (0.23, 0.25, 0.28, and 0.31) were studied in terms of mechanical and fresh properties, leaching behaviour, and microstructure to evaluate the degree of PV inclusion in the K-struvite matrix. The addition of PV into sust-MPC improves the mechanical behaviour of the micromortars, indicating a good inclusion of PV. The mechanical and fresh behaviour of the formulations, and BSEM-EDS analysis revealed the potential chemical interaction between Al and K-struvite matrix. The addition of 17.5 wt.% of PV with a W/S of 0.25 showed the best mechanical performance (∼40 MPa of compressive strength at 28 days of curing). The amount of PV should be lower than 17.5 wt.% to classify it as non-hazardous material at the end-of-life.

Physico-chemical properties, structural characterization, and dissolution behaviors of four phosphate glasses modified by incorporating zinc, boron, and copper, acting as eco-friendly fertilizers with controlled release of macro and micronutrients for wheat plants, were investigated. The elaborated glasses were characterized by differential thermal analysis, density measurements, X-ray diffraction, FTIR spectroscopy, and Raman spectroscopy. The dissolution behaviors were investigated using weight and pH measurements. The ionic concentration of leachate solutions was determined using ICP-OES. Results proved that the glass's chemical composition and lattice structure play the mean role in controlling the release of nutrients from the glass. The seemingly different properties between the elaborated glasses depend on the strength's bonds of glass lattice-formers and modifiers as well as their ionic field strength of the incorporated elements. An agronomic valorization was carried out to evaluate the efficiency of these agriglasses on wheat crops. It revealed a positive impact on wheat growth, yield, photosynthetic parameters, and grain mineral content with improvement values ranging from 4 to 89% compared to conventional fertilizers. These results pave the way to applying these fertilizers in large-scale experimentation to confirm their potentiality in crop production and as eco-friendly fertilizers.

Naples yellow was widely used across different types of artwork. Technical studies identified a binary Pb–Sb type as well as modified ternary variants with either zinc or tin in the structure. Although these variants were the object of previous experimental studies, a better understanding of the impact of the glazing procedure on the chromatic, chemical and crystallographic characteristics of the pigment is still lacking. In this work, several historical Naples yellow recipes were re-worked and subsequently applied and fired on test tiles, over a white glaze. The results show that the interaction between pigment and glaze produces important modifications to the colour, chemistry and structure of the pigment. Such modifications will strongly impact the reconstruction of historical recipes, with major consequences for identifying Naples yellow variants on artwork and investigating artistic practices.

The humidity regulation in the interior spaces of buildings by means of passive solutions that do not require energy consumption is a topic of great interest due to the current needs for comfort and energy efficiency. This paper addresses the engineering of humidity regulating ceramic tiles that incorporate a functional coating formulated from gibbsite together with other common raw materials whose moisture regulating capacity has been demonstrated previously. A multi-layer coating tile system has been proposed, consisting of the following elements: an engobe layer, the functional coating with the regulating capacity, a decoration by inkjet technology and a protective topcoat glaze.

This system has been analysed with moisture adsorption–desorption tests. The moisture regulation capacity and the effect of the coating thickness on this property have been determined, allowing to optimise the functionality.

Finally, an analysis of the humidity regulation has been performed on the basis of demonstrators or small-sized cubicles that simulate the conditions of final use in rooms of buildings. The results show the different behaviour of the demonstrator with functional tiles in relation to conventional tiles, with an indoor ambient humidity that remains in the comfort zone for longer periods of time.