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

In the present work, we studied the effect of Sn⁴⁺ and Cr³⁺ doping on the structural, ferroelectric, and dielectric properties of BaSn_xCr_yTi_1−(x+y)O₃. The materials were prepared by a combination of high-energy mechanical milling and solid-state reactions. The X-Ray Diffraction (XRD) analysis and Rietveld refinements confirmed the presence of a single tetragonal phase for the pure and doped samples. The SEM study revealed that the microstructure is highly susceptible to the addition of both dopants, causing an evident grain refinement. On the other hand, the addition of Sn⁴⁺ and Cr³⁺ had a strong influence on ferroelectric properties, as observed by the pinching of the ferroelectric hysteresis loops. The addition of Sn⁴⁺ increases the remnant and maximum polarization, as the Cr³⁺ doping promoted the contrary effect. Co-doping with Sn⁴⁺ and Cr³⁺ resulted in a maximum energy storage value of 0.2574 J/cm³ with a efficiency of up to 65%, overcoming the values of pure BT. The relative permittivity of all doped samples remained in values of ∼1000, just a little below the permittivity of pure BT.

Synthetic gibbsite (Al(OH)₃) was mechanically activated by attrition milling for 24 h, with various grinding ball-to-powder weight ratios (0, 5, 10, and 20), and characterized by thermal analysis (TG-DSC). Further, we determined the corresponding kinetic parameters using the model-free and model-fitting methods from the Thermogravimetric Analysis (TG) data set. We found that the activation energies provided by both models agree very well. At temperatures higher than 350 °C, the milled samples (GB5, GB10, and GB20) lose mass very slowly, while the unmilled sample (GB0) decomposes faster. In addition, we demonstrated that the decomposition mechanism of each sample engages multi-step reactions, and the corresponding activation energies change with the increasing milling conditions.

Pure and niobium doped bismuth titanate ceramics ${\text{Bi}}_4{\text{Ti}}_{3-x}{\text{Nb}}_x{\text{O}}_{12}(\text{Nb}-\text{BiT})$ with $x$ ranging from 0% to 2% are prepared by sol–gel method. Pellets are sintered by pressureless sintering (PLS) and spark plasma sintering (SPS). Raman spectroscopy indicates distortion in the structure due to the substitution of titanium by niobium. X-ray photoelectron spectroscopy (XPS) displays the Nb integration to the bismuth titanate ceramic structure. X-ray diffraction shows no secondary phases and offers clues about crystallographic texturing due to the SPS technique. The shape and size of the grains are strongly influenced by the niobium added to the system as reported by scanning electron microscopy. Ferroelectric hysteresis loops exhibit the effect of the niobium and the texturing on the ferroelectric behavior. Higher values of remanent polarization are reported for PLS samples. In comparison with PLS, higher values of the relative permittivity are reported for SPS samples due to the non-homogeneous incorporation of Nb.

The Great Mosque of Córdoba is the only mediaeval Islamic monument in al-Andalus that still contains some of its original 10th-century glass mosaic decoration, even though they were significantly altered and restored several times in the 18th, 19th and 20th centuries. By examining analytical, textual, and graphic evidence, this study attempts to reconstruct the different transformations of the Maqṣūrah, focusing on the glass mosaics in order to assess possible implications for their state of preservation. The results show that high-alkaline glass, which can be associated with modern tesserae, was used to restore the Miḥrāb and Sābāṭ mosaics. Modern pigments were also detected in the paints that were applied in situ to the surface of the colourless glasses. Textual and analytical evidences prove that Bāb Bayt al-Māl mosaic was completely removed in the 20th century and a replica with high-lead tesserae was installed in the same place.

The Oued Zemmour deposit is associated to Neogene volcanism in the Kert basin, Nador area (Morocco), and thus one of the numerous bentonite occurrences in the Gourougou volcano's region. To assess their potential use, this article examines the Oued Zemmour bentonite deposit, helping with mineralogical, physicochemical, morphological, geotechnical analyses and ceramic performances. Mineralogical associations are essentially made of montmorillonite, K-feldspars and plagioclase, associated with lower quantities of calcite, dolomite and quartz. The main chemical composition in oxides is SiO₂ and Al₂O₃. Geotechnical results show that the swelling index and Atterberg limits widely vary within the deposit, but all studied samples display high plastic and swelling qualities. The 10 representative bentonite samples of the area (Oz 1–Oz 10) were subjected to a ceramic technological assessment, and all samples have displayed good quality after dry pressing method and sintering at 1000 °C without any defect or cracks (except for Oz 4, Oz 5, and Oz 8 samples). Therefore, two mixtures (Oz M and Oz M1) have been developed from the samples studied, using the same manufacturing protocol. The obtained ceramics were evaluated by studying their morphological structure and macroscopic aspect, as well as their bulk density, porosity, water absorption, shrinkage and tensile strength properties.

Sustainable glasses were prepared by green technology including the use of different wastes as raw materials and concentrated solar power (CSP) as renewable energy. The raw materials used to formulate the glasses were animal bone flour ash, which presents high contents of CaO, P₂O₅ and alkaline oxides; glassy sand from the waste of packaging glass submitted to a primary treatment, composed principally of SiO₂; and potassium carbonate of reagent grade. Different exposure times to solar radiation were tested. For comparison, the same composition of glass was melted into a conventional electric furnace. The use of CSP to produce glasses reduces the melting time by approximately 90%, with consequent energy savings. The increased CSP processing time results in more amorphous and thermally stable glasses. The results showed the viability of producing ecofriendly glasses in the SiO₂–P₂O₅–CaO–K₂O system, which could be used as matrix-based fertilizers.

This article breaks new ground in understanding of variation in the magnetic strength performance, flux pinning and energy dissipation mechanism of polycrystalline bulk Bi_1.8Sr_2.0Ca_2.2Cu_3.0O_y (Bi-2223) superconducting materials added with the different vanadium concentration level (0.0 ≤ x ≤ 0.30) under the magnetic field strengths applied up to 5 T for the first time. We provide the sophisticated and phenomenological discussions on the magnetoresistivity measurement results in three main sections along the paper. All the findings show that the increase of both the vanadium concentration in the crystal structure and external magnetic field strength damages significantly the magnetic strength performance, vortex dynamics, flux pinning ability and vortex lattice elasticity of bulk Bi-2223 superconducting ceramics. The vanadium addition promotes thermally the movement of correlated two-dimensional (2D) pancake Abrikosov vortices between the in-plane Cu–O₂ layers in the valance band, vortex lattice elasticity, vortex dynamics, distance for interlayer Josephson couplings and flux pinning centers and the theoretical computations confirm the remarkable degradation in the formation of super-electrons in the Bi-2223 crystal system. Thus, the vanadium addition is anticipated to be one of the best selectable materials to examine the differentiation in the thermal movement of correlated 2D Pancake Abrikosov vortices in the bulk Bi-2223 superconducting system.

The shielding properties of a Cu-doped Ni–Zn polycrystalline ferrite in the frequency range 1 MHz to 1 GHz were explored. Samples of composition (Cu_0.12Ni_0.23Zn_0.65)Fe₂O₄ were prepared by the traditional ceramic route. The complex relative permittivity (${\epsilon }_r={\epsilon }^{\prime }-j{\epsilon }^{″}$) and permeability (${\mu }_r={\mu }^{\prime }-j{\mu }^{″}$) of the absorber ceramics were measured, and the minimum reflection-loss $RL$, matching frequency $f_m$, matching thickness $d_m$ and bandwidth for $\text{RL}\le -20\text{dB}$ were calculated using the theory of the absorbing wall. Effect of the main process parameters (pressing pressure P, sintering temperature T, and sintering time t) on the electromagnetic properties and microwave-absorbing characteristics was deeply investigated. The rise of the three selected process parameters was observed to improve the sintered microstructure of the final specimens (monitored by the relative density $\varphi$ and the average grain size G), provided that abnormal grain growth does not occurred. The increase in sintered relative density and average grain growth modifies complex permeability and permittivity in the explored frequency range, enhancing the shielding properties of the material.

In this work, a new combination of ceramic materials is proposed for bone tissue engineering applications. Multilayer scaffolds consisting of a core composed mainly of calcium pyrophosphate and external coatings of silica and calcium doped with Fe³⁺, Sr²⁺ and Mg²⁺ were prepared. To study the influence of the arrangement of dopant ions in the external coatings, two different scaffolds were developed: scaffolds 3J consisting of a single external coating with 9 mol% of Fe³⁺, Sr²⁺ and Mg²⁺ ions; and scaffolds 3S comprising three external coatings, each containing 3 mol% of Fe³⁺, Sr²⁺ and Mg²⁺ ions. Scaffolds were physico-chemically characterized and evaluated for in vitro bioactivity and cellular response in the presence of MG-63 cells. The results showed that the core scaffold displayed no in vitro bioactivity or good cellular response, but served as a support for the external coatings given its mechanical resistance. The cell viability of scaffolds 3J and 3S increased more than 100% in relation to the core, and also improved cell proliferation and adhesion resulting in a dense layer of cells that covered the scaffolds’ entire surface. The arrangement of ions in the external coatings did not influence the cellular response, but determined the bioactivity rate.