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

This article investigates the development and potential applications of low-melting point lead-free glasses. Their importance is due to strong market demands to comply with the strict international regulations against the use of lead. In this work, a preliminary study of the existing interactions of a low-melting-temperature glass belonging to the P₂O₅–CaO–Na₂O system when it is deposited on different ceramic substrates, both traditional (porcelain stoneware) and technical (alumina and zirconia), has been carried out. The ionic diffusion through the studied interfaces, the phases present, the composition of the glassy phase and the surface morphology of the coating have been studied by Field Emission Scanning Electron Microscopy (FESEM), with coupled EDX microanalysis. The chemical resistance of the different glassy coatings obtained is also evaluated. The results showed that these new lead-free low-melting-temperature glassy coatings are chemically and mechanically compatible, and promising candidates for applications and markets in a broad range of fields.

Little is known about the materials used in the manufacture of red window glass in the 19th and the first decade of the 20th century. Here, we have studied fragments from eight Spanish glasses from the 19th and 20th centuries. The red glasses consist of a single layer of red glass on a colourless glass substrate. The chemical composition, oxidation state, nature of colourants and crystalline precipitates were determined by a selection of microanalytical techniques. In the study, we have found that the red colour of the glass is due to the presence of Cu⁰ nanoparticles, the red glass layer has lower calcium content than the substrate glasses, which we found favours copper being present in the glass predominantly in Cu⁺. They also contain tin and iron while lead, described in historical and modern documentation, was absent. Tin must have been added to the glass as a Sn²⁺ compound and acted as a reducing agent for copper. Iron is also a well-known reducing agent, but does not act as such in the red glasses studied here. However, it may have facilitated the reduction of copper to Cu⁰ by promoting its incorporation into the glass as Cu⁺ rather than Cu²⁺.

The effects of adding zircon and synthesized TiO₂ nanoparticles (NPs) to standard porcelain tiles on mechanical and optical properties were studied. The obtained TiO₂ nanoparticles had an average particle size of 7.47 nm. The optical properties of TiO₂ NPs were characterized by using UV–visible spectrophotometer. The synthesized TiO₂ NPs and commercial zircon were added to standard porcelain tile composition at a rate of 1%, 2% and 4% by weight. Phase analyzes of the samples were made with XRD, and microstructure analyzes were made with SEM/EDS. Optical dilatometer test was used for sintering studies and densification behaviour was observed with water absorption test. The optical behaviour of the samples was analyzed using spectrophotometric measurements (CIELab method). As a result of this test, it was observed that nano-sized titanium oxide can be used as a whitening agent in porcelain tiles. In addition, the additives made to porcelain tiles also contributed to the increase in mechanical properties.

The increase in pollution, using photocatalytic materials to degrade organic pollutants remains in force. ZnO is the most used semiconductors for photocatalytic applications. The oriented growth of nanostructures on substrates or seed layers (SL) improves the physical and chemical properties compared to the bulk-grown material. In this work, the photocatalytic efficiency of ZnO nanorods and nanoflowers was evaluated, obtained by hydrothermal growth (HG) over SL deposited by the spin-coating technique (SCT). The characterizations results showed two types of growth: 1D nanostructures with a dimension in the range of 400–1000 nm and diameters of 70–100 nm, and 1D microstructures with approximate 5–11 μm length and diameters of 1–2 μm. However, in the 7 SL system, micro prisms were generated, which led to the formation of 3D nanostructures (micro flowers) of ZnO with a maximum of 6 μm in diameter. The system with 1D and 3D ZnO nanostructures, grown in 7 SL, was the most efficient methylene blue degradation. Achieving 100% transformation in 120 min, with a rate constant of 2.98 × 10⁻² min⁻¹. The results show that the SCT deposit combined with the sol–gel method and HG produces 1D and 3D structures with high potential in photocatalytic degradation.

A large amount of waste glass (WG) and rice husk ash (CCA) is produced yearly. This paper evaluated the effect of incorporating waste glass in concrete prepared with rice husk ash (RHA) as a partial substitute for cement, considering differences in the mechanical and thermal behavior of concrete based on the proportions of WG and CCA. A 5% replacement of cement by ashes of rice husk and waste glass was considered in this work. Concrete samples were prepared with several RHA:WG ratios namely 1:0, 1:1, 1:2, and 1:3 (RHA + WG = 5%). For these concrete samples, the mechanical, thermal, and environmental properties were evaluated, the latter measured in CO₂ emissions. Results showed that workability (i.e. slump) and density increased as long as WG content increased. The value of compressive strength of 1:3 mixture was 14% higher than the 1:0 concrete mixture. Moreover, the thermal conductivity was increased by 380% and CO₂ emissions were dropped by 5.5%, in comparison to 1:0 concrete mixture. The incorporation of WG improves mechanical and thermal properties and reduces the environmental impact of rice husk ash concrete.

Lithium silicate-based glass-ceramics are widely employed dental materials, showing superior aesthetics (determined by translucency) but poorer wear resistance under severe contact conditions than alternative, artificial crown materials. This work investigates possible correlations between the level of translucency and resistance to wear (in vitro) under sliding contact against hard zirconia antagonists in commercial lithium disilicate and zirconia-reinforced lithium silicate dental glass-ceramics. Wear rates are quantified, and mechanisms responsible for material removal are analyzed. Results are discussed in terms of the materials’ microstructure and mechanical properties within the framework of a fracture mechanics model. Finally, implications for materials selection in dentistry are briefly discussed.

The synthesis of glass–crystalline materials in the system Na₂O/CaO/SiO₂/Fe₂O₃ with high concentrations of Fe₂O₃ (20, 25 and 30 mol%) by applying the melt-quenching technique is reported. The melts spontaneously crystallize during pouring and the formation of magnetite (Fe₃O₄), hematite (α-Fe₂O₃) and ɛ-Fe₂O₃, as identified by X-ray diffraction (XRD) is observed. The microstructure and the elemental composition of the prepared materials are further investigated by scanning electron microscopy (SEM) and two different morphological types of Fe-containing crystals – needle-like and dendrite-shaped are detected. Mössbauer spectroscopy showed the presence of Fe³⁺ and Fe²⁺, as well as the existence of iron ions both in tetrahedral and octahedral coordination and the precipitation of hematite, ɛ-Fe₂O₃ and magnetite. The magnetic measurements on the prepared samples reveal ferrimagnetic properties with well defined hysteresis curves, although due to relatively small volume fraction of the iron-rich crystalline phases, the net magnetic moment is quite low compared to the bulk values for magnetite.

Plasma electrolyte oxidation was used to modify the surface of different Ti alloys: c.p. Ti (α hcp structure), Ti–15Nb (α′ + β structure) and Ti–33Nb–33Zr (stable β cubic structure) and the influence of elements and microstructure in the TiO₂-based ceramic layer formed as well as the surface properties was analyzed. The XRD patterns confirmed the presence of TiO₂ (anatase and rutile) in the c.p. Ti. For Ti–15Nb (wt.%) indicated the presence the same oxides also of pentoxide niobium (Nb₂O₅). For Ti–33Nb–33Zr (wt.%) indicated just the presence of rutile as the stable oxide one at room temperature and dioxide zirconium (ZrO₂). In addition, the formation of calcium carbonate CaCO₃ and calcium phosphate Ca₃(PO₄)₂ was detected in all 3 materials. The ceramic-like layer was more homogeneous for c.p. Ti and Ti–15Nb and more irregular hole like-pores for Ti–33Nb–33Zr. Bioactive ions used were detected in all alloys and the roughness for Ti–15Nb was higher compared to c.p. Ti. and Ti–33Nb–33Zr. The contact angle for the three samples was higher than 100°.

Ceramic-based bone graft substitutes have been extensively studied for bone tissue engineering, due to their biocompatibility and osteoconductivity. Additionally, several studies have shown how graphene and its derivatives, due to their unique properties, can strongly promote cell adhesion, by enhance cellular adherence, proliferation, and osteoblast differentiation, and how graphene-based materials can promote spontaneous osteoblastic differentiation. The aim of this study was the use of a calcium silicophosphate ceramic, previously prepared in our laboratory, that presents excellent in vitro bioactivity, optimizing its operation by rGO coating. After coating with rGO any significant differences were observed in diffraction peaks from starting calcium silicophosphate ceramic, and SEM analysis showed a rough and undulating surface that favored a high specific surface area for promoting cell adhesion, proliferation and differentiation of cells. It could be confirmed by in vitro cell cultured with ahMSCs, showing adhesion and growing for cells with interconnected filaments extending over the surface, covering it after 7 days.