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

The impact of graphene oxide (GO) on the hydration process, calcium silicate hydrate (CSH) gels structure, and macro-mechanical properties were systematically researched by combinatorial techniques. Findings from ²⁹Si MAS-NMR and nitrogen adsorption (BET) revealed that the effect of GO on the hydration degree of the cement paste, and the main chain length (MCL) is more pronounced at advanced ages (from 28 days), due to its act as a nucleation site. Moreover, the results of Raman spectroscopy tests showed that GO has a strong interaction with the cement matrix. Due to the increase in the degree of hydration, the lengthening of the chain length (MCL), and the formation of strong bonds, both compressive and flexural strength tests also improved. Therefore, the effect of GO as a nucleation site has a positive effect on the cement paste nano-properties at advanced ages.

The use of natural zeolites as precursors offers a valuable alternative in the search for new materials applied to zeolite synthesis. Each study focused on the interzeolitic conversion method plays a fundamental role in understanding the evolution from one zeolite to another. In this study, a natural zeolite containing the crystalline phases of clinoptilolite and mordenite, with HEU and MOR topologies, respectively, as per the coding assigned by the IZA, was employed as a precursor. Combined with potassium–aluminum hydroxide solutions at two different concentrations, followed by a conventional hydrothermal process with durations of 50 and 90 h, characterization of both the precursor and resulting zeolite was performed. A conversion mechanism was proposed based on the structural similarity between the initial and target zeolites. To support these conclusions, characterization techniques such as X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, Fourier-transform infrared spectroscopy, inductively coupled plasma optical emission spectroscopy, and nitrogen adsorption were utilized. This process represents a potential pathway for the synthesis of merlinoite-type zeolites, MER.

Geopolymer composite production has become an indispensable product to reduce carbon dioxide emissions, which have become an important problem today, and to provide green sustainability. Concerns about the global climate change problem have also accelerated geopolymer studies. This research investigated the mechanical and durability characteristics of low-calcium fly ash (LCFA) based geopolymer mortars with different curing temperatures and times. Two forms of curing conditions were applied; the first one was standard curing at room temperature (20 ± 3 °C and RH 65 ± 10%) and the second one was cured in the hot air at 40 °C, 60 °C, and 80 °C for 24 h, 48 h, and 72 h followed by standard curing. After all curing processes, compressive strength, flexural strength, water absorption, void ratio, resistance to elevated temperatures, and freeze–thaw conditions were determined experimentally. In addition, SEM analysis was performed before and after durability tests for comparison purposes. Also, XRD and TGA analyzes were performed. According to test results, curing specimens at longer times and higher temperatures has been shown to increase compressive strength results. The highest compressive strength value was reached at 80 °C after 72 h of curing. Geopolymer specimens subjected to elevated temperatures (600 °C and 900 °C) lost a significant part of their strength value. After the freeze–thaw test, LCFA-based geopolymer specimens showed more than 70% resistance. The freeze–thaw resistance of geopolymer samples was positively affected on long-term curing at high temperatures, but high-temperature resistance was impacted negatively.

Bioactive glasses are mainly used to repair bone defects since they stimulate the natural healing of damaged tissues, allowing the adhesion and proliferation of bone-forming cells. On the other hand, tantalum is known to have good chemical resistance and biocompatibility, with no adverse biological response in organisms. In the present work, 45S5 bioglass systems undoped and doped with Ta₂O₅ were prepared according to the following stoichiometric molar relationship (46 − x)SiO₂ − 26.9CaO − 24.4Na₂O − 2.6P₂O₅ − xTa₂O₅ (x = 0, 0.1, 0.5) by the conventional melt quenching technique. Subsequently, scaffolds from these glassy systems were prepared using the combined method of powder technology and polymer foaming. Both, glass powders and scaffolds, were physicochemical characterized. The results showed that the 0.5 mol% Ta₂O₅-doped scaffolds exhibited less contraction (36.53%) and higher porosity (84.24%) during sintering, with interconnected porosity, pore size in the range of 19–260 μm, and a greater surface area (17.431 ± 0.846 m²/g) than the scaffolds with no Ta₂O₅. Furthermore, the tantalum oxide promoted the formation of a sodium tantalum phosphate phase, along with the combeite and silicorhenanite present in the undoped-glass scaffolds. The maximum compressive strength of scaffolds ranged from 0.42 to 1.40 MPa and the elastic modulus (E) from 0.19 to 0.47 GPa.

Image analysis techniques can be used to detect and interpret the degradation processes that a material undergoes and to help identify the causes and mechanisms of degradation. Structures and morphological changes are also analysed to establish hypotheses about physical changes. Together with complementary analytical techniques, chemical and mineralogical changes can be evaluated.

The methodological process consists of a sequential simplification of the initial micrograph: segmentation of the image, cleaning and isolation of the crack from associated elements, and crack skeletonisation. This method allows the previous image to be processed, thus successfully isolating the microcracks. It is also valid for their quantification.

Cold winter temperatures at high latitudes in coastal regions lead to prolonged exposure of offshore concrete structures to freeze–thaw (F–T) damage, which significantly reduces the mechanical and durability properties of concrete. To improve the durability of concrete under F–T damage, this study investigated the combined effects of fly ash (FA) and bentonite on the frost resistance of polyvinyl alcohol fiber reinforced geopolymer concrete (PFRGC). The study comprehensively analyzed the effect of fly ash and bentonite content on the rate of mass change and compressive strength under various F–T damage conditions. In addition, uniaxial compressive tests were carried out at different stages of F–T damage and the resulting stress–strain curves and compressive properties were analyzed. Correlations between peak stress, peak strain, modulus of elasticity and deterioration time of the concrete were developed. SEM microscopy tests were also used to investigate the evolution of the internal microstructure and the morphological characteristics of the erosion products under freeze–thaw conditions. The results indicated that the change in concrete mass with a growing number of F–T cycles can be divided into two periods: a gentle increase and a faster increase. A continuous increase in the rate of mass increase was observed for the specimens containing fly ash and bentonite, while the compressive strength of these specimens continued to decrease. During F–T damage, the maximum stress decreased slightly and the maximum strain increased gradually as the volume of bentonite and fly ash increased. This study provides a theoretical basis and technical basis for the development of fly ash and bentonite to improve the frost durability of offshore structures.

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.