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

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.

SrZrO₃-structured perovskite particles were prepared under hydrothermal conditions in a KOH (5 M) solution using Zr-gel and SrSO₄ mineral precursors. The treatments were conducted between 150 and 240 °C for different reaction intervals (1–96 h), and the KOH solution volume varied between 7.5 and 30 mL. To evaluate the effect of the Zr-gel precursor, the treatments were preliminarily conducted with a coprecipitated pasty Zr-gel (Zr(OH)₄·9.64H₂O) and subsequently with a lyophilized Zr-gel Zr(OH)₄ powder. Generally, SrZrO₃ particles were produced by a single-step reaction following the simultaneous bulk dissolution of the Zr⁴⁺ gel precursor and the SrSO₄ powder. However, in the preliminary experiments, a dehydration reaction of the pasty Zr-gel preceded the ultimate single-step reaction, resulting in complete SrZrO₃ particle formation taking place over a longer interval of 96 h at 240 °C. In contrast, when using the dried Zr-gel powder, complete feedstock dissolution occurred more rapidly, producing SrZrO₃ particles at 200 °C over 48 h. The SrZrO₃ particle sizes varied significantly depending on whether the pasty gel or dried powder Zr precursor was used. Particles prepared with the pasty gel exhibited a bimodal size distribution with mean particle sizes of 25 and 65 μm with pseudocubic and star-shaped cuboidal morphologies, respectively. In contrast, particle growth resulting from the rapid dissolution of solid powder feedstock produced cubic-shaped particles, monomodally distributed with an average particle size of 10 μm. Furthermore, byproduct (SrCO₃) formation occurred predominantly under earlier stages together with SrZrO₃ particle irrespective of the 5 M KOH filling volume; however, at a volume of 15 mL spontaneously achieved in situ the SrCO₃ dissolution at intermediate stages of reaction. This reaction pathway did not proceed at small (7.5 mL) and large (30 mL) volumes of the alkaline fluid. A kinetic study indicated that the activation energy required to produce the SrZrO₃ cubic-shaped particles was low in both cases, i.e., 15.05 and 22.27 kJ mol⁻¹ between the powder and pasty Zr⁴⁺ precursors, respectively.

Eight samples of Portland cement and a clinker provided by the Brazilian Association of Portland Cement were analysed with different laboratory diffractometers and a synchrotron instrument to determine the statistical variability in the determination of the mass percentage of the main crystalline phases. Five laboratories participated in the experiment. Data collection was performed by each laboratory following its own internal procedures for a standard Rietveld analysis of mineral phases. Both Cu and Mo radiations were used. Reflection geometries—with and without sample rotation—and transmission geometries were also used. The synchrotron diffraction pattern was acquired from a rotating capillary and a wavelength of 0.41290 Å. Analysis of all diffraction patterns was performed with the help of TOPAS Academic v. 6 with the specific purpose of determining the proportions of polymorphs M1 and M3 of alite, since their ratio must be taken into account for the subsequent development of the mechanical properties of concrete.

This research consists of the fabrication of synthetic gels of hydrated calcium silicate (C-S-H gel) and hydrated calcium aluminate silicates (C-A-S-H gel) in aqueous solution oversaturated in calcium hydroxide. These gels were fabricated using nanomaterials with different specific surface area; two nanosilicas (NS), OX50 and A200 (50 and 200 m²/g respectively) and two nanoaluminas (NA), A65 and A130 (65 and 130 m²/g). Mixtures were carried out maintaining a Ca/Si = 2 ratio and variable Al/Si ratios of 0.1, 0.5 and 1. The effect of aluminium incorporation in the C-S-H gel was studied using the nuclear magnetic resonance technique (²⁹Si MAS-NMR), and the information obtained was further processed using the mathematical deconvolution method. Chemical shift bands were delimited to identify the structures. From the results obtained, modifications of the tetrahedral (Q_n) in the dreierketten structure were observed in the different combinations, as well as the modification of the bridging tetrahedral (Q₂b) due to the presence of aluminium replacing the silica bridging tetrahedron Q₂b(1Al). High Q₄ values were detected in the C-S-H gel with NS OX50 and this could be associated to a double chain formation very similar to a perfect tobermorite. The length of the mean chains (MCL) was very variable in each blend, but some trends were observed as the Al/Si = 1 ratio and the Al/Si = 0.1 ratio maintain or increases the MCL respectively. The results are interesting and concrete case mixtures with NS OX50 show original trends that have not yet been reported in the literature.

This work aims to contribute to reducing environmental damage caused by the manufacturing of Portland cements (PC), through in-depth exploration into the durability of two mortars manufactured from blast furnace slag: an alkaline-activated one (AAS) and a hybrid cement (HS) with less than 20% clinker. The carbonation resistance of these eco-friendly mortars is compared to that of a mortar based on Portland IV cement. From a mineralogical point of view, DTA-TG and confocal Raman microscopy (CRM) tests have been carried out, along with measurement of pH changes, compression strength and total porosity. Böhme tests have been performed to evaluate changes due to carbonation in the wear behavior of the mortars under study. Using the CRM technique, it has been possible to establish a relationship between the carbonation of the systems with the unbound carbon content, as well as identify the different polymorphic phases of CaCO₃ formed. The results obtained reveal that alternative AAS and HS mortars are more difficult to carbonate than Portland cement mortars, and that the effect of this process on the porosity depends on the nature of the hydroxides previously present in the pore solution. The carbonation of the surfaces also improves the abrasive wear resistance of the mortars under study.