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

The structural, microstructural, morphological, and electromagnetic properties of a micro- and nanostructured nickel–zinc ferrite ((Cu_0.12Ni_0.23Zn_0.65)Fe₂O₄) were studied after sintering between 900 and 1100 °C. The microparticulated ferrite (MICRO) was a commercial material, while the nanoparticulated ferrite (NANO) was obtained through high energy milling of the former. The effect of microwave heating (MW), compared to traditional infrared sintering (IR), was investigated.

Microwave sintering successfully controlled the grain growth of both granulometries and produced sintered bodies with high relative densities (low porosity), small average grain size, narrow grain size distribution, and a high value of the complex magnetic permeability-imaginary part (μ″) for the MICRO ferrite. In the case of the NANO ferrite, microwave sintering yielded values similar to those obtained by conventional IR.

Microwave sintering significantly affected the densification and grain growth processes for both granulometries studied. Additionally, reducing the granulometry of the starting ferrite powder had a noticeable impact on the microstructure and electromagnetic properties of the sintered ferrites, regardless of whether microwave or infrared radiation was used. However, the magnetic property (μ″) decreased when the particle size of the starting powder was reduced from micro to nanometric scale, irrespective of the sintering source. This observation is supported by our previously published mathematical models that establish relationships between the complex magnetic permeability, magnetization mechanisms, angular frequency, and ferrite microstructure.

This work investigates the chloride binding capacity combine of two sustainable pozzolanic additions such as granulated blast furnace slag (G) and metakaolin (M) used in cement to decrease its carbon footprint. They are also combined with two nanosilicas with different specific surface area (O and A). Blends of alone M or G and with nanosilica are mixed in water with Ca(OH)₂ and chloride (C) to compare chloride binding capacity of both in presence or not of nanosilica. Blends are analysed by XRD, FTIR, DTA–TG and chloride binding capacity is determined too by potentriometric titration with AgNO₃. The addition of chlorides to both pozzolanic M and G indicates that M shows higher chloride binding capacity than G although very similar Friedel's salt formation, indicating a higher physisorbed chlorides contain. Chlorides addition meaningfully replaces carbonates in carboaluminates phases to form Friedel's salt, being this exchange higher for samples with M than for G blends. The combination of experimental techniques used in this study have shown that the effect of nanosilica addition to samples with M and G show an opposite effect in Friedel's salt formation, increasing for samples with G and decreasing for samples that contain M.

There is growing concern about the health of our planet, which has led to a search for methods to purify and recover the pollutant materials that are released into the environment. Among all industries, the dyeing sector of the textile industry is considered one of the most polluting. However, advancements in technology, such as the use of nanoadsorbents, have made it possible to effectively treat and clean these wastewaters by harnessing the adsorption capabilities of these minerals. As a result, highly functional pigmentary hybrids with improved characteristics can be obtained. In this study, the research focuses on exploring the potential of hydrotalcite in combination with reactive, disperse, and direct dyes. Colour measurements are conducted using reflection spectrophotometers to evaluate the colour performance of the hybrid materials, yielding successful results. X-ray diffraction (XRD) analysis is used to verify the structural integrity of the hydrotalcite and confirm the adsorption of the dyes. Additionally, thermogravimetric tests (TGA) are carried out to assess the thermal stability of the different samples, while the colorants’ protection provided by the hydrotalcite is evaluated through total soluble recovery (TSR) measurements. An FTIR analysis is used to detect the presence of characteristic functional groups of the dyes in the resulting hybrids. Surface area and porosity measurements utilising the BET method, along with Scanning Electron Microscopy Energy + Dispersive X-ray spectroscopy (SEM–EDX) and X-ray photoelectron spectroscopy (XPS) tests, are also conducted. In summary, this study investigates the potential of hydrotalcite as an effective adsorbent for various dyes used in the textile industry. The research involves comprehensive analyses, including colour evaluation, structural characterisation, thermal stability assessment, and surface morphology examination. These findings contribute to the development of sustainable and environmentally friendly approaches in the treatment of textile wastewater.

The synthesis of a TiO₂-tight ultrafiltration membrane supported on a low-cost ceramic substrate based on metakaolin and natural apatite was proposed in this study. To optimize the substrate composition, three samples were prepared by combining metakaolin and natural apatite with weight ratios of 25:75 (MK25), 50:50 (MK50), and 75:25 (MK75), and then sintered for 2 h at 850, 900, 950, and 1000 °C. The effect of sintering temperature and metakaolin content on the final properties of the prepared samples was studied in terms of microstructure, porosity, and mechanical strength. According to the results, the mechanical strength increased with increasing temperature and metakaolin content, but at the same time, the porosity decreased. MK50 composition and the temperature of 950 °C were chosen as optimal conditions, and the support was prepared by extrusion. The prepared substrate presented a compressive strength of 4.4 MPa, porosity of 33%, and an average pore size of 2.2 μm. To prepare a crack-free ultrafiltration membrane, the deposition of the TiO₂ top layer was favoured over an alumina intermediate layer. The obtained membrane has a pore size of 6.8 nm and water permeability of 5.6 L h⁻¹ m⁻² bar⁻¹. The membrane performance was tested for the removal of cationic and anionic dyes. The ultrafiltration experiments have shown a high removal rate for anionic and cationic dyes. Specifically, it was found that the removal rates of these dyes exceeded 75% without adjusting the pH of the solution.

Electrochromic devices (ECDs) have the ability to show color even when electrical power is disconnected. However, challenges such as simple and cost-effective electrochromic material preparation, insufficient coloration, slow switching times, and poor cycling stability have yet to be overcome. The paper describes an electrochromic device with WO₃ thin film as the electrochromic material for the working electrode and ZnO thin film as a counter electrode fabricated on FTO glass substrates by a simple sol–gel spin coating method. The optical contrast at 600 nm of ZnO counter electrode based ECD (12.4%) is almost double that of graphite counter electrode based ECD (6.5%), showing higher efficiency and better electrochromic response. The properties of ECD devices were also examined using cyclic voltammetry and chronoamperometry measurements with results showing that the devices were stable and the charge required to tint the device (5.6 mA s) is reduced compared to typical graphite-coated counter electrode. These types of devices are promissing candidates to be used as smart windows.

Novel (Cr,V)-ZrSiO₄ jewel green pigments with near-infrared reflection performance were prepared at a low temperature of 900 °C. Effects of Cr/Si mole ratio on phase composition, microstructure, Vis–NIR reflection performance, optical properties and thermal stability were studied. The results show that with the increase of Cr/Si mole ratio from 0 to 0.4, the color of the pigment changes from blue to jewel green and then to dark green. When the Cr/Si mole ratio is 0.2, the (Cr,V)-ZrSiO₄ jewel green pigment shows the best comprehensive properties, which has rendering performance (L* = 56.69, a* = −18.52, b* = −9.28), thermal stability, and near-infrared reflection performance. The properties especially excellent near-infrared reflection performance make it promising functional pigment in heat insulation.

In this research, the effect of La substitution by Pr cation in the A-site of ABO₃ perovskites was carried out using the Pechini method for use in solid state fuel cells (SOFCs). The atomic compositions of Pr varied from x = 0.35, 0.49, 0.53, 0.56, 0.63 and 0.7 in the La_0.7−xPr_xCa_0.3MnO₃ (LPCM) perovskites. The XRD patterns indicated that all the perovskites crystallized in the orthorhombic system with Pnma space group, but only in atomic compositions of 0.53 and 0.70 is possible to obtain pure phases; whereas the other compositions present narrow peaks of La and Pr oxides that are reduced with the amount of the cationic substitution. The Rietveld methodology and its analysis by the Goldsmith tolerance factor indicated that the stability of the samples was achieved through Jahn-Teller distortion in the b-axis. The Mn³⁺/Mn⁴⁺ atomic ratios determined by XPS measurements suggested that the substitution of La ions by Pr promotes the hole doped system instead of electron system. The electrical conductivity showed that the synthesized perovskites are mixed ionic and electronic conductors which positively influence their application in SOFCs. In particular, the La_0.17Pr_0.53Ca0_.3MnO₃ may be a good cathode candidate for these devices.

Highly efficient IR-blue light up-converting NaYF₄: Yb³⁺, Eu²⁺ phosphors have been prepared by a template-free hydrothermal method under mild and reductive experimental conditions. It has been demonstrated that for a fixed reaction time and temperature (150 °C/4 h), the α → β NaYF₄ conversion can be accurately controlled by modifying the F/Y ratio. UC emission spectroscopy reveals that IR-blue light emission efficiency is greatly improved when β-NaYF₄ phase predominates. Under the experimental conditions set in this work, reaching full α → β conversion just by increasing fluoride content entails the co-crystallization of the secondary phase YF₃ 1.5NH₃, but far from causing a detrimental effect on the optical properties, it has been found that the samples where both β-NaYF₄ and YF₃ 1.5NH₃ phases coexist, exhibit outstanding optical properties.