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

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.

A representative set of glass from mostly Indo-Pacific type beads and other materials including a carnelian bead from two Swahili sites of the Ibo Island at Northern Mozambique has been archaeometrically characterized to get insights into its likely provenance within the framework of the Indian Ocean trade networks. Selected samples were examined and analyzed by using binocular magnifying glass, field emission scanning electron microscopy with energy dispersive X-ray microanalysis, visible spectrophotometry and X-ray diffraction. Up to four different types of glasses were identified according to its chemical composition: mineral-soda alumina glass from Western India, vegetal-soda alumina glass from Central Asia, a conventional soda-lime silicate glass coming probably from Europe and a lead silicate glass of the PbO-SiO₂ binary system most likely from Venice. Red and yellow colours were obtained through colloidal chromophores: cuprite micro-crystals for red brick and lead stannate and/or lead antimoniate micro-crystals for yellow, while deep blue, greenish blue and yellowish colours were obtained through ionic chromophores. Either the carnelian bead or the different types of glass are imported materials resulting from Swahili trade networks of the Indian Ocean, since no evidence of glass production or recycling has been found in archaeological fieldwork.

The production of cement depletes natural resources and emits huge amounts of CO₂. Using waste materials as replacement for cement is a practical solution to produce green concrete. Cane bagasse ash (CBA) and waste glass (WG) have great potential as supplementary cementitious materials. This work presents the effect of the incorporation of cane bagasse ash on mechanical properties and CO₂ emissions of concrete prepared waste glass. Different CBA:WG mass ratio 0:1, 1:3, 1:2, 1:1, 2:1, 3:1 and 1:0 (CBA + WG = 20%) as cement replacement were prepared. The slump decreased with an increase of waste glass and sugar cane bagasse. The incorporation of sugarcane bagasse ash and waste glass it is not related with the density of concrete due to similar density between cementitious materials. The relative compressive strength increased with inclusion of CBA, the 3:1 mixture exhibited the highest relative compressive strength. The CO₂ emissions were reduced when WG and CBA were incorporated. The addition of cane bagasse ash to concrete prepared with waste glass may be a potential option to mitigate the impact of residues and to reduce the CO₂ emissions in concrete industry.

The structural and electrical properties of K_0.48Na_0.52Nb_1−xZr_xO_3−δ (x = 0–0.04) ceramics prepared by the conventional solid-state reaction method were studied. Pellets with composition x ≤ 0.03 sintered at 1125 °C for 2 h showed single-phase of potassium sodium niobate (KNN) perovskite structure. Based on X-ray diffraction and Raman results, a mixture of orthorhombic and monoclinic phases was observed in intermediate compositions. The addition of Zr improved the sinterability and the “hard” piezoelectric properties of KNN, increasing the E_c and Q_m values. The composition with x = 0.03 presented the highest permittivity at room temperature, ɛ_r′ = 363 and the lowest dielectric losses, tan δ = 0.027. Moreover, it was the sample with the highest Q_m and d₃₃ values, with Q_m = 1781 and d₃₃ = 82 pC/N. It was therefore the best compositions to obtain a “hard” piezoelectric material based on Zr-doped KNN, which makes it promising candidate for use as “hard” lead-free piezoelectric material for high power applications.

Removal of heavy metal Mn²⁺ ions in water is of great importance for human health and it is urgently needed to develop efficient adsorption materials. Here, a green and effective strategy to prepare mesoporous micro/nanostructured lithium disilicates (LDs) by employing the cation surfactant hexadecyltrimethyl-ammonium bromide (CTAB) as morphology control agent in hydrothermal environment, and investigated its adsorption behavior toward Mn²⁺ ions. The LDs possessed branched structures that were consisted of scattering pyramidal rods bestrewn with secondary nucleated and aggregated nanoparticles. Due to the mesoporous structures and negatively charged surfaces, LDs exhibited a high adsorption capacity up to 346.84 mg g⁻¹ with corresponding removal efficiency up to 99.82% when initial Mn²⁺ concentration was 82 mg L⁻¹, and their maximum adsorption capacity reached up to 785.25 mg g⁻¹ toward Mn²⁺ of 250 mg L⁻¹. Results indicated that the isotherm adsorption behavior of LDs was well described by mono-layer Langmuir model and kinetic adsorption fitted well with pseudo-second-order model, implying them the excellent chemical adsorbent to remove Mn²⁺ from wastewater. We believe this CTAB-modified approach could be extended to prepare other lithium silicates with mesoporous structures, rendering them wider applications in environmental protection.