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The substitution of La2O3 by Tb2O3 was studied for glass samples with a chemical composition described by: 75P2O5 + (25 − x) La2O3 + xTb2O3, where x = 5, 10, 15, 20 mol%. The mechanical properties were predicted via the Makishima–Mackenzie model. The study demonstrated that when increasing the Tb2O3 content from 5 to 20 mol%, the elastic moduli of the glasses decreased, while the dissociation energy, packing density, and micro-hardness increased. In addition, the radiation shielding properties were studied using the MCNP5 code, which was utilized to simulate the linear attenuation coefficient (LAC) of the investigated samples. Furthermore, the mass attenuation coefficients (MAC) of the glasses were determined. The highest MAC was reported for the sample with 20 mol% of Tb2O3 and decreased from 0.358 to 0.0515 cm2/g between 0.184 and 1.408 MeV. Furthermore, the effective atomic number (Zeff), equivalent atomic number (Zeq), exposure buildup factor (EBF), and the energy absorption buildup factor (EABF) of the glasses were calculated utilizing BXCOM software. The substitution of La2O3 by Tb2O3 was revealed to enhance the shielding features of the TLP samples.

Ceramic engineers have investigated the rheology of the refractory concrete to keep the balance between the desired characteristics of castables and its flow demeanor. The rheology of refractory concrete determines their application manner and a considerable fraction of its properties are largely affected by its flowability. This article gives a brief introduction to refractory concretes. It discusses the variable determinants of castables’ rheology according to their significance and their relation to each other. The measurements of rheology were examined by conventional techniques and the mathematical models of viscosity and rheometry approaches are also used for clarification. Insights into the rheology of alumina–silica containing castables were speculated through exploring submicron and nano-sized particles. The rheology of refractory concrete can be adapted properly according to the application manner and the specified requirements.

Calcium phosphates are biomaterials widely used in bone tissue engineering. In recent years, the alternative of obtaining these materials with antimicrobial properties, has been explored due to the multiple advantages that this would imply in the design of devices or implants that prevent the failure of these associated with bacterial colonization. The goal of the present work was obtaining gold nanoparticles supported on biphasic calcium phosphates (BCPs) with high crystallinity by one-step solution combustion technique, and with antimicrobial response, a fact that can significantly reduce the production cost of these materials. X-ray diffractograms (XRD) showed that prepared powders have high crystallinity owing to high temperatures during the combustion reaction, also Rietveld refinement showed that the inclusion of gold nanoparticles (AuNPs) influenced the phases’ ratio obtained. Furthermore, scanning electron microscopy (SEM) showed agglomeration of particles with morphologies with shape tending to be equigranular, while the presence of AuNPs was corroborated by transmission electron microscopy (TEM). All samples that were obtained in a single step, by solution combustion, showed antimicrobial behavior validated through the inhibition halos, whereas particles subjected to thermal treatment lost their antimicrobial response.

In this study, porous carbon has been prepared through potassium hydroxide (KOH) activation of coconut fiber (CF) and subsequent carbonization in the presence of an inert gas. The activated carbons (AC) were prepared via carbonization of the precursor at different temperatures. Subsequently, their electromagnetic wave absorption (EMWA) performance was investigated at X-band frequency. The phase crystallinity, porous features, and degree of graphitization of the activated carbons were studied using XRD, nitrogen adsorption/desorption isotherm, and Raman spectroscopy, respectively. Using the BET method, the activated carbon prepared at 750 °C displayed a high specific surface area of 602.9 m2 g−1 and an average pore size of 6 nm, which confirms the extant of mesopores. The EMWA was studied using COMSOL Multiphysics software based on the finite element method. Results show that the activated carbon prepared at 750 °C attained an optimal reflection loss of −45.6 dB at 10.96 GHz with a corresponding effective bandwidth of 3.5 GHz at a thickness of 3.0 mm. In conclusion, this study interestingly shows that porous carbon obtained from coconut fiber has great potential for attenuating electromagnetic waves.

Yttrium aluminum garnet (YAG) with cerium admixture (Ce:YAG) was plasma sprayed using two different devices – gas-stabilized plasma (GSP) torch and water-stabilized plasma (WSP) torch. Coatings on stainless steel as well as self-standing plates were produced. Besides microstructure and crystallographic characterizations, dielectric tests were performed on these coatings. They included capacitance (i.e. relative permittivity), loss tangent and volume resistivity measurements. After spraying, the YAG crystal phase was preserved without any decomposition, but an amorphous fraction was detected in the as-sprayed coatings deposited by both processes. The dielectric behavior of the coatings was influenced by imperfections like splat boundaries, pores and thin cracks. The Ce:YAG samples were successfully plasma sprayed by both spray techniques. Selected aspects of wear were measured and compared with a single-crystal. The dielectric properties are comparable with the single-crystal and highly promising, particularly the loss tangent with values so low that they were not found in any other as-sprayed ceramic coating.

Maltose and pectin-assisted low-temperature combustion modified sol–gel process was employed to synthesize nanopowders of Ce0.8Sm0.2O2−δ (SDC 20), Ce0.81Nd0.095Sm0.095O2−δ (NSDC). The sample's powder was sintered at 1250 oC for 6 h to form dense ceramics with a relative density greater than 95%. The Rietveld refinement of powder XRD patterns indicates a single-phase material with a cubic fluorite structure. The Raman spectroscopy studies confirm solid solution with evidence of more oxygen vacancies in sample NSDC to sample SDC 20. The SEM images of the samples show a high-dense surface with few pores. The EDX results confirm the sample's chemical composition. Impedance measurements were carried out to study electrical properties. The NSDC sample showed improved conductivity (3.06 × 10-2 S/cm at 600 °C) over SDC 20 (2.16 × 10-2 S/cm at 600 °C) with lower activation energy (0.81 eV). Specific grain (σ*g) and grain boundary (σ*gb) conductivity values were calculated using porosity corrections to the Bricklayer model.

Current trends in the ceramic industry see an increasing interest on porcelain stoneware, by which is possible to produce large tiles and slabs. These products are manufactured by spray-dried powders, which have excellent technological properties but require high energy and water consumption. Dry-processed granulates allow to reduce such a consumption, but suffer from a different technological behavior. A solution to improve the environmental sustainability of ceramic tile-making is mixing powders prepared by the wet and the dry routes. The technological features of industrially manufactured mixed powders was investigated (rheological properties, compaction response and firing behavior) in order to point out advantages and possible pitfalls. Dry-processed and spray-dried granulates exhibit different distributions of size, shape and moisture that reflect on distinct rheological and compaction behaviors. Mixed powders show a more or less accentuated deviation from linearity between the end terms. This fact makes possible to add up to ∼50% dry granulates by keeping the technological properties close to current industrial bodies. Sparings of water, energy and CO2 emission for the milling and granulation stages are estimated for a mix 50% spray-dried and 50% dry-processed powders.

Chitosan-coated Fe3O4 nanoparticles were prepared by coprecipitation followed by reaction with chitosan and different volumes of glutaraldehyde. Coating was modified by varying the volume of glutaraldehyde and reaction time. XRD pattern shows maxima compatible Fe3O4 structure. FTIR spectroscopia confirms the presence of chitosan, more evident in samples with higher chitosan content, as denoted by TGA. TEM images of samples with low glutaraldehyde content reveal particles coated with a homogeneous chitosan shell. Meanwhile, those prepared with high glutaraldehyde volume show nanoparticles dispersed in an organic matrix. Samples present almost superparamagnetic behavior with magnetization saturation values that are reduced as the content of organic matter increases. Regarding the stability of these samples in solution, the presence of a homogeneous coating improves the initial suspension, although it does not prevent its subsequent aggregation over time. However, this aggregation process is reduced for sample synthesized with 1 mL of glutaraldehyde after 6 h of reaction.

Ruthner powder is a by-product of the steel hot-rolling process. This study introduces a new application area for this waste material by investigating its activity for the oxygen evolution reaction. Ruthner powder with the α-Fe2O3 phase structure was deposited on the carbon paper substrates using the electrophoretic deposition (EPD) process to fabricate the electrodes. The effect of the concentration of cetrimonium bromide ([CTAB]) and the Ruthner powder ([RP]) in the EPD cell on the morphology and activity of the electrodes were investigated by SEM, LSV, and EIS techniques. The results revealed the formation of a homogenous layer on the carbon paper when [CTAB] and [RP] were respectively 0.4 g.l−1 and 0.2 g.l−1. The obtained electrode showed the best activity among all fabricated electrodes. In particular, its onset overpotential and overpotential at a current density of 10 mA.cm−2 were respectively 85% and 25% lower than those of bare carbon electrodes.

In this article, it is intended to evaluate the performances of previously synthesized different nanometric compounds as SOFC components under real conditions. For this purpose, anodic supports SOFCs have been manufactured in different configurations. The compounds NiO-(Y2O3)0.08(ZrO2)0.92 (NiO–YSZ), (Y2O3)0.08(ZrO2)0.92 (YSZ), Sm0.2Ce0.8O1.9 (SDC), La0.6Sr0.4FeO3 (LSF) and LaNi0.6Fe0.4O3 (LNF) were used as anode support, electrolyte, barrier, cathode and contact layer, respectively. To obtain the cells, the anode supports were produced by uniaxial pressing and the remaining layers were added using the airbrush technique, assembling them by different sintering processes. The cells developed have been electrochemically tested in a temperature range between 750 and 865 °C. Additionally, degradation tests have been carried out under constant current. Moreover, to characterize the microstructure of the cells, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscopy (EDX) analyzer has been used. The results obtained show that the incorporation of cathode and contact layers increases the power densities and decreases the total resistances of the cells with respect to the cell without cathode, especially with the addition of the LNF contact layer. Despite the improvement obtained, more tests have to be carried out in order to optimize the performance of SOFC devices in degradation tests.

The aim of this research was to evaluate the production of glass ceramics from novel combinations of fly ash, glass cullet, blast furnace slag and copper slag solid wastes. The CaO/SiO2 molar ratios of the mixtures were 0.17–0.39. Glass ceramics were produced by thermal treatment of frits obtained by quenching in water. The results show that samples with a high Fe2O3 content (>4 wt%) are not adequate for glass-ceramic formation, as a result of the effect of ferric iron, Fe3+, which increases the network connectivity, on the stability of the glass. The mechanical properties of the ceramic materials were as follows: elastic modulus of 97.8–106 GPa, Vickers microhardness of 612–701 MPa, fracture toughness of 0.45–0.84 MPa m1/2, and friction coefficient of 0.57–1.0. For the glass ceramics, the mass loss did not exceed 1% in NaOH and 15% in HNO3 as a result of the crystalline phases formed. The ceramic materials developed in this research could be considered for potential applications in the production of glazes for residential or industrial tiles and coatings, among others.

Elephant ivory has a long history as a highly valued commodity in many cultures because of its unique physical, chemical and mechanical properties that served both human wants and needs. Importantly, ivory allowed for aesthetic expression not possible historically with other materials: it carves well and lasts long even under heavy usage. And as such it has, over millennia, made its way into high-value ornaments, weaponry and household objects as well as false teeth and hip-replacements. Outside the human world, in the wild, for the animal, exceptional toughness is required of the elephant’s ivory when a tusk is being used to leverage trees to breaking point or act as a weapon in fights between bulls the size and weight of trucks. Little wonder that ivory has evolved properties and qualities so desired by ancient designers, artists, carvers and medics as well as modern pianists, pool players and, tragically, as ostentatious displays of wealth. But this very nature of ivory is endangering the life and future of its key source, the elephant. This menace posed by human greed does, as it must, restrict, limit and prohibit the continued use of natural ivory. While modern composite materials have largely displaced the functional need for ivory, most of them lack its intriguing properties. Elephant ivory (which is the most important ivory traded even now) is a dense, multifaceted bone-like material of rather complex 3-dimensional construction and levels of porosity. Museum curators and antiquarians care about these properties of ivory for two reasons: regarding its historical value as material (in the sense of workable substance) and concerning its requirements for preservation and display.

En la Ciencia Politica, el estudio de las elites politicas ha experimentado un boom desde los anos noventa, en tanto ha seguido un proceso de emancipacion respecto a los trabajos clasicos de corte prosopografico o sociologico. Para dicha disciplina, el concepto de elite politica es indisociable del de representacion politica, de manera que puede ser definido como miembro de la elite aquel personero politico que a traves de su posicion, prestigio —o influencia— participa directa o indirectamente en el proceso de toma de decision y elaboracion de politicas.1 Esto supone, por lo tanto, un numero restringido de personas, por oposicion a la masa de los representados/gobernados o a los politicos de segundo rango. Asimismo, en un contexto de generalizacion de los valores democraticos, los politologos han estudiado a las elites politicas con relacion a sus representados bajo el prisma de las dos caras de Jano: la semejanza y la diferencia. Semejanza, porque para poder llegar a ser los representantes de sus electores, las elites precisan parecerse a estos ultimos, de modo tal que puedan sentirse identificados. Diferencia porque, a la vez, deben distinguirse de los demas ciudadanos y candidatos, al mostrar sus credenciales de capacidad (intelectual, tecnica, entre otras) para legitimarse en su rol decisorio. Esta consideracion abrio el espacio a la elaboracion de numerosos trabajos sobre el perfil de las elites politicas y la diada entre su representatividad (proximidad a los electores) y su desempeno politico (su capacitacion para elaborar o evaluar/aprobar politicas publicas). Emergio asi una serie de trabajos que reflejan el alejamiento de las elites respecto a sus bases a favor de un crecimiento en el grado de “tecnicidad” de las mismas (tecnocratas y technopols).

The purpose of this work is to study the influence of the immersion temperature and the treatment time of the ion exchange of soda-lime glass in molten KNO3 bath on its mechanical properties, and in particular the erosion resistance using Sahara sand and alumina abrasives. EDS analysis showed that the depth of penetration of K+ into glass increases as temperature and treatment time increase. The effect of ion exchange temperature and time on mechanical reinforcement was studied by micro-indentation, scratch test, wear and erosion test. All of these mechanical properties are improved after ion exchange treatments; erosion and wear resistance behave the same, either by using natural abrasives such as Sahara sand or by using an aggressive abrasive as alumina grits. The increase in the ion exchange time induces an increase in Vickers hardness of about 15–40% compared to annealed glass. Samples processed at 520 °C for a short period of 2 h show better mechanical properties compared to samples processed at 480 °C for longer times. In this case, the sample has a higher surface density which made the glass in compression not only because the potassium ions occupy the ionic substitution spaces but also the free spaces.

Potential use of raw clayey deposits from El Jadida, Morocco, in the manufacture of traditional ceramic products has been evaluated through a careful sampling and an in-depth characterization of the outcropping features around Ouled Sidi Ali Ben Youssef area (El Jadida city). We collected six representative clay-rich materials (C1–C6) for subsequent analyses by several spectroscopic and mineralogical techniques including physico-chemical, mineralogical, and thermal analyses. Our results revealed high amounts of oxides, mainly SiO2, Al2O3, Fe2O3, CaO and MgO. Those ferruginous clays were found suitable for dark ceramic bodies. Further mineralogical examination confirmed low to medium contents of clay minerals, but subordinated by quartz, calcite, dolomite and plagioclase as the main nonclay minerals. Ternary diagram plots indicated that the studied clays were suitable for structural clay products and clay roofing tiles. C5 sample exhibited the best physico-chemical and mineralogical properties due to its illitic nature (64%), low quartz content (28%), high plasticity index (32) and lower loss on ignition (10.84%). Therefore, C5 clayey sample was selected as a potential candidate to be mixed with expanded perlite (EP) for the production of insulating ceramics. Specimen were prepared from the new mixture (i.e., C5 and EP) by pressing and firing at 1100 °C. The obtained ceramic bodies were ascertained by addressing their bulk density, water absorption, shrinkage, bending strength, thermal conductivity, structural and mineralogical properties.

The mechanical properties of crystalline materials can be efficiently optimized using a hierarchical twinned structure. Conventional deformation mechanisms for coherent Σ3 boundaries generally involve three basic models: cross-slip, partial dislocation step, and full dislocation step. In this study, we report a novel deformation mechanism that allows the co-existence of twin-separation, phase transformations, grain rotation, and cracking, around a triple junction of twin boundaries in a hierarchical twinned high-entropy alloy. The deformation mechanisms in the reference high-entropy alloy (Fe-30Mn-10Co-10Cr at.%) were investigated using LAADF-STEM. The triple junction of the hierarchical twinned structure gradually deformed during in-situ strain and showed mechanisms significantly different from that observed in the purely twinned structures. These new mechanisms are referred to as “novel synergetic deformation mechanisms of hierarchical twin boundaries.” Understanding the fundamental mechanisms of the hierarchical twin boundaries under deformation could assist the design of strong and ductile bulk materials with hierarchical twinned structure.

©2020 SECV.Published by Elsevier España, S.L.U. This is an open access article under the CCBY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/), With the aim to contrast existing historical documentation with information provided by the own materials, an archeometric study of a representative set of tiles from the Monastery of El Escorial was undertaken. The ensemble, composed of 19 ceramic fragments, covers examples from the 16th and 17th century, either from Talavera or Toledo provenances, and was selected according to stylistic criteria. The goals of the study consisted in determining the average chemical composition of the ceramic body, its textural and microstructural characteristics, the crystalline phases to establish firing temperatures, also in studying these aspects in the enamel or glaze layer, as well as in identifying the chromophores for the coloring of the decorations. Conventional techniques such as binocular magnifying glass, XRF spectrometry, petrographic observation by thin-section, XRD, FESEM with EDS microanalysis and visible spectrophotometry were used. Resulting data indicated the use of calcareous clays for the body (22.0–25.5wt.% CaO), the presence of neoformed phases such as gehlenite, diopside and anortite which suggest a firing temperature between 950 and 1050°C approximately, lead-based glazes (∼25.0wt.% PbO on average) with SnO2-opacifier (∼57.0wt.% on average) and Co2+, Cu2+, Fe3+-ions and lead antimoniate for blue, green, brown and yellow decorative colors, respectively.

Mullite is one of the preferred aluminosilicates for both traditional and advanced ceramics. This paper reports the use of simplex-centroid mixture design to prepare mullite–glass ceramics by reactive sintering. The phase composition and technological properties of formulations containing kaolinitic clay, kaolin waste and alumina were investigated after sintering at 1400 °C. The sintering behavior was assessed by dilatometry. Microstructural analysis indicated the crystalline phases mullite, residual quartz, cristobalite, and α-alumina. A glassy phase was also identified as a matrix embedding mullite grains (as seen by X-ray diffractometry and scanning electron microscopy). In kaolin waste-rich formulations, a liquid phase sintering mechanism favored the densification process and the mechanical resistance. Highly significant statistical models allow correlating the concentrations of raw materials with linear firing shrinkage, water absorption and apparent porosity. Overall results stand out for the potential of using kaolin waste in the preparation of mullite–glass ceramics.

Resumen En este trabajo se presenta un estudio en el que se aplica la teoria funcional de densidad (DFT), utilizando el software CASTEP, para cristales de silicato (K2SiO3, K2Si2O5 y K2Si4O9) y de oxido de silicio (cuarzo). La densidad de estados (DOS) de estos silicatos muestra que los dos tipos de atomos de oxigeno, puente (BO) y no puente (NBO), tienen una distribucion electronica significativamente diferente en los orbitales 2p y 2s, debido a un ambiente quimico inmediato diferente. Esto lleva a un desplazamiento a energias menores de las bandas de valencia s y p de la densidad de estados parcial (PDOS) del NBO de alrededor de 2 eV respecto de la PDOS del BO. En el cristal de menor contenido en K2O (K2Si4O9), se incrementan los enlaces covalentes Si-O debido a la transferencia de carga electronica del orbital 4s del atomo de potasio al NBO, y de este NBO al atomo de silicio y, finalmente, a todos los atomos del tetraedro, lo que permite mejorar la fuerza de enlace del sistema. Este hecho resulta en que el material final tenga una mayor resistencia mecanica. Por otro lado, en el K2Si2O5 (el cual posee un NBO por tetraedro) el enlace Si-O es mas debil con respecto al del K2Si4O9, tendencia que se acentua en el K2SiO3 (que posee dos NBO por tetraedro). Esta misma tendencia sigue la dureza Vickers calculada teoricamente. Este estudio se ha aplicado a vidrios de silicato de potasio obtenidos experimentalmente y se han comparado varias propiedades mecanicas con las teoricas de los respectivos cristales de igual composicion quimica. Los NBO tanto de cristales como de vidrios se han cuantificado a partir de las unidades estructurales Qn. Se ha observado que las propiedades mecanicas de los vidrios no pueden ser explicadas unicamente por las contribuciones de los tetraedros libres unidos por el vertice y caracterizados por sus BO y NBO como funcion de la concentracion en K2O, es decir por los Qn. Esto es debido a que la DFT de CASTEP para sistemas cristalinos considera todo orden de interaccion. Por ello es necesario utilizar estructuras a alcance intermedio, denominadas como unidades estructurales rigidas (RSU). La contribucion de los tetraedros libres se ha calculado usando la dureza Vickers del cristal y un factor de apantallamiento por la perdida de la interaccion de medio y largo alcance. En el trabajo se explica el comportamiento de la dureza Vickers y modulo de Young de vidrios de SiO2-K2O en un amplio rango de composiciones molares.

The reaction between chamotte and active carbon at high temperature and low oxygen partial pressure conditions has been investigated. Both components react at temperatures above 1400 °C where cristobalite is reduced by the carbon while increases the mullite content. At 1600 °C mullite tends to disappear due to the reduction reaction leading to the formation of alumina. The reaction between chamotte and active carbon in these conditions produces the reduction of silica and mullite. This process increases with the reaction time although not all the active carbon is consumed. The graphite nanodomain size of the active carbon tends to decrease with respect to the original size with both the temperature and the reaction time. The microstructures of the obtained materials present a glassy phase due to the inherent presence of impurities in chamotte, and where small particles, pores and mullite needles are also observed. The presence of this glassy phase becomes more pronounced with the treating temperature while solid particles and pores tend to disappear, moreover, the formation of the glassy phase occurs in a less extent due to the higher concentration of active carbon. The presence of the liquid glassy phase also favours the formation of the long-needle like mullite crystals.

Basalts, which cover about 70% of the Earth's surface, are igneous rocks originating from cooling and solidifying the magma on the Earth's surface. Products obtained from the melting of rocks have a wide market and can be considered the precursors of glass-ceramic technology. These materials are promising due to the possibility of converting low-cost natural raw materials into products with excellent mechanical, thermal, and chemical properties. In this article, a general overview of the basic principles for obtaining basaltic glass-ceramic materials will be made, as well as their properties, applications, and potentialities.

Fabrication of thin-wall components using the laser powder bed fusion (LPBF) additive manufacturing (AM) technology was investigated for two “hard-to-weld” high gamma prime Ni-based superalloys RENE 65 (R65) and RENE 108 (R108). Simple block parts with wall thicknesses of 0.25 mm, 1.00 mm, and 5.00 mm are printed using a bidirectional laser scanning strategy without layer-wise rotation. Parts with walls thinner than 5 mm fail before reaching the designated build height. Results indicate that reduction of limiting build height (LBH) corresponds to the reduction of part thickness and is unaffected by alloy composition. On the contrary, the number of internal micro-cracks along columnar grain boundaries in the build direction (BD) increases with part thickness and is significantly higher in R108 than R65. These findings suggest that reduced LBH in parts with thinner walls is not caused by internal micro-crack formation. Fractography and finite element analysis (FEA) of the in-process thermal stresses show that the LBH trend is not explained by the conventional cracking mechanism. Simulations suggest that part thickness affects stress distribution leading to more substantial distortion and consequent failure to add layers for continued fabrication of thinner parts.

This research has addressed a complete study of the bioactivity of bioactive glass coatings obtained by atmospheric plasma spraying. The coatings have been characterized in terms of microstructure, adhesion, crystalline phases and bioactivity. Hydroxycarbonate apatite formation was also monitored following a standard protocol and the in vitro cell response was evaluated by human osteoblast-like cells (MG-63 cells) incubation. The obtained coatings shown a microstructure typical of glass coatings. A simulated body fluid test proved that coatings are capable of developing a surface layer of hydroxycarbonate apatite whereas the appearance of this phase takes place at a longer time than that observed for the powder feedstock. Cell-culture test showed multidirectional growth of MG-63 cells which promoted good contact between cells and the surface of the coating. This study has confirmed a positive effect of the coatings in terms of surface bioactivity and, more interestingly, it has proven an adequate cell-material interaction on the coating surface. Este trabajo ha abordado un estudio completo de la bioactividad de recubrimientos de vidrio bioactivo depositados mediante proyección térmica por plasma atmosférico. Se han caracterizado la microestructura, la adherencia, las fases cristalinas y la bioactividad de los recubrimientos obtenidos. También se ha estudiado la formación de hidroxiapatita carbonatada siguiendo un protocolo estándar y se ha evaluado la respuesta in vitro de los recubrimientos mediante su incubación con osteoblastos humanos (células MG-63). Los recubrimientos obtenidos han mostrado una microestructura típica de recubrimientos de vidrio. Tras la inmersión en fluido biológico simulado, se ha comprobado que el recubrimiento es capaz de desarrollar una capa superficial de hidroxiapatita carbonatada, aunque la velocidad de aparición de esta capa es menor que la observada para el polvo de vidrio de partida. El ensayo de cultivo celular ha mostrado un crecimiento multidireccional de las células MG-63, dando lugar a un buen contacto entre las células y la superficie del recubrimiento. Este estudio ha confirmado un efecto positivo de los recubrimientos en términos de bioactividad de la superficie y, lo que es más interesante, ha demostrado una adecuada interacción célula-material sobre la superficie del recubrimiento.

Zirconia and silver oxide substituted 1393 bioactive glasses (1393Zr and 1393Zr–1Ag) were prepared by sol-gel technique and sintered at 900–1100 °C. ZrO2 incorporation into the glass was on the sole purpose of mechanical performance augmentation, while Ag2O being antibacterial, their incorporation on microbial efficacy, in vitro bioactivity and cytocompatibility were assessed. The Ag2O incorporated glass showed minimal effect on bioactivity of the parent glass. Both the cytocompatibility (U2-OS cells using MTT assay) and antibacterial efficacy (by using Bacillus subtilis; and Escherichia coli) were found significantly improved in silver doped glass than the undoped one. Excellent mechanical performance was also observed in 1393Zr-1Ag compared to the both pure 1393 glass and 1393Zr. Thus, Ag2O incorporation into 1393Zr not only introduced the bactericidal efficacy, but also enhanced the mechanical properties of the glass, while leaving bioactivity unharmed. Thus the Ag2O incorporated 1393Zr seems a potential biomaterial for bone tissue engineering application.

In this present study, synthetic tobermorites are prepared using bio-waste (snail shell) and municipal waste (container glasses) as lime and silica precursors respectively. Six batch compositions were formulated with varying combination of soda-lime glass and snail shell ash. The bodies were sintered at 950 °C for a holding period of 2 h in an electric muffle furnace. Analyses such as scanning electron microscopy (SEM/EDS), Fourier Transform Infra-red Spectroscopy (FT-IR), X-ray diffractometry (XRD) were used to assess the microstructure, functional groups and the phase composition of the prepared tobermorites respectively. The results of the morphology shows that the tobermorites possess irregular but spherical shaped grain with coated water films while the EDS shows the presence of Ca and Si with small amount of Al confirming tobermorite. The FT-IR indicates Ca–O–Si and Si–O–Si as main functional groups while the phase composition investigated by XRD indicate low intensity peaks of calcium silicate (CaSiO3).

Representative ‘Blue speckled’ (13–16th centuries) and ‘Brown speckled’ (13–21st centuries) wares recovered from the excavations in Qalhât or collected around Bahlâ city (Sultanate of Oman) were characterized by XRPD, SEM-EDS, Raman/optical microspectroscopy, and thermal expansion. Minerals present in the body (quartz, augite and albite as major phases, calcite, dolomite, rutile, anatase, phosphate, hematite and magnetite as minor phases) were identified by XRPD and/or Raman spectroscopy. SEM-EDXS microanalysis was performed on the glazes in order to compare their composition, especially the type of flux. The firing temperatures measured from the thermal expansion curves range between 1080 °C and 1150 °C. This preliminary study confirms that the first differentiation can be made by considering non-invasive Raman technique and thermal expansion measurement is sufficient to get an extensive comparison of the wares. A local place of production is likely for the body of all samples but importation of the glazes of ‘Blue speckled’ wares is questioned. Modern Bahlâ productions cannot be considered to have inherited the Qalhât ones. Ba-rich, cassiterite-opacified glaze corresponding to the Late Islamic Arabic Period appears as a new technology without a connection to the ancient one.

We consider two important problems concerning the interaction between a cycloid surface and a screw dislocation. First, we examine the interaction between a traction-free and charge-free periodic cycloid wavy surface and a screw dislocation under anti-plane mechanical and in-plane electrical loading in a hexagonal piezoelectric solid. With the aid of conformal mapping and analytic continuation, we derive an elementary closed-form solution of the two-dimensional analytic vector function in the image plane characterizing the electroelastic field in the piezoelectric solid. The stresses, electric displacements, strains and electric fields in both the corresponding Cartesian and the curvilinear coordinate systems are determined. The image force acting on the piezoelectric screw dislocation is then obtained using the generalized Peach–Koehler formula. For a cusped cycloid surface, the resultant stress and electric displacement intensity factors at the cusp tips and crack extension force on the cusp tips are presented. Secondly, we use essentially the same approach to investigate the problem of the interaction of a screw dislocation with a traction-free and conducting cycloid surface in a hexagonal piezoelectric half-plane. A simple dislocation emission criterion is proposed.

In this study, the impact of varying spraying current on tribological performance and microstructural properties for coating was investigated. Atmospheric plasma spraying (APS) was used as the technique of depositing coatings on Q235 grade steel (equivalent to ASTM A36 mild steel). The coated samples were characterized using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), adhesion testers and microhardness tester. Scratch tests were carried out under ambient and dry environments using a pin-on-plate configuration against Tungsten Carbide (WC) body (pin/stylus) for a constant load. It was found that samples sprayed under higher current had better adhesive bond and erosion wear resistance, they also had the lowest wear loss and least percentage porosity. Additionally, hardness was improved almost 10 times of the base material in comparison to lower current samples. Resumen: En este estudio se investigó el impacto de la corriente de pulverización variable sobre el rendimiento tribológico y las propiedades microestructurales para el recubrimiento del Cr2O3. La pulverización con plasma atmosférico (PPA) se usó como la técnica para depositar recubrimientos de Cr2O3 sobre acero de grado Q235 (equivalente al acero dulce ASTM A36). Las muestras recubiertas se caracterizaron usando microscopía óptica (MO), microscopía electrónica de barrido (MEB), espectroscopia de energía dispersiva (EED), probadores de adherencia y probadores de microdureza. Las pruebas se llevaron a cabo en medios ambientales y secos utilizando una configuración de pin en placa contra el cuerpo de carburo de tungsteno (WC) (pin/stylus) para una carga constante. Se encontró que las muestras rociadas con una corriente más alta tenían un mejor enlace adhesivo y una mejor resistencia al desgaste por erosión, también tenían menor pérdida de desgaste y menor porcentaje de porosidad. Además, se mejoró la dureza casi 10 veces del material base en comparación con muestras de corriente más baja.

International audience; A simple, first order description of the formation of ε- and α′-martensite in meta-stable austenitic Fe–Mn alloys containing 12–35 wt% Mn was developed. Given the initial volume fractions of ε- and α′-martensite in the non-deformed material, it is possible to calculate the evolution of phase fractions as a function of applied strain. An accurate estimate of the initial amounts of ε- and α′-martensite based solely on the Mn content of the alloy, could not be obtained due to the important role of microstructure features and processing conditions on the martensitic transformations.

This study mainly investigated the effects of silicate concentration at the range of (16 g/L to 56 g/L) on the plasma electrolytic oxidation of Zircaloy-2 in potassium hydroxide/sodium silicate electrolytes in detail, including the growth behavior, wear and corrosion resistance of as-obtained ZrO2/SiO2 alloyed coatings. It was found that the coating thickness increased continuously on increasing the silicate concentration in electrolyte. Besides, the amount of t-ZrO2 in the coatings increased with increase of silicate concentration in electrolyte, while the amount of m-ZrO2 decreased. Comparative studies have shown that the coatings formed in electrolyte with high silicate concentration possessed superior wear and corrosion performance, which could be ascribed to heavy silica deposition associated with the presence of t-ZrO2 stabilized by SiO2. The results may provide guidance for obtaining high performance of ZrO2/SiO2 alloyed coatings. Besides, it is believed that the presence of Si species in zirconia endows the coatings with enhanced bioactivity like bioactive glasses and ceramics coatings and we envision that the as-prepared ZrO2/SiO2 alloyed coatings have great potential for biological applications. Resumen: Este estudio investigó en detalle los efectos de la concentración de silicato en el rango de (16 a 56 g/l), en la oxidación electrolítica por plasma de Zircaloy-2 en electrolitos de hidróxido de potasio/silicato de sodio, incluido el modo de crecimiento y la resistencia al desgaste y a la corrosión de los recubrimientos de aleaciones de ZrO2/SiO2 obtenidos. Se descubrió que el espesor del recubrimiento aumentaba continuamente al aumentar la concentración de silicato en el electrolito. Además, la cantidad de t-ZrO2 en los recubrimientos aumentó con el aumento de la concentración de silicato en el electrolito, mientras que el contenido de m-ZrO2 disminuía. Estudios comparativos han demostrado que los recubrimientos formados en electrolito con alta concentración de silicato poseían mayor resistencia al desgaste y a la corrosión, que podría atribuirse a una fuerte deposición de sílice asociada con la presencia de t-ZrO2 estabilizado por SiO2. Los resultados pueden proporcionar guía para obtener un alto rendimiento de los recubrimientos con aleaciones ZrO2/SiO2. Además, se cree que la presencia de especies de Si en la circona dota a los recubrimientos con una bioactividad mejorada como recubrimientos cerámicos o vítreos bioactivos, y prevemos que los recubrimientos de aleaciones ZrO2/SiO2 preparados tienen un gran potencial para aplicaciones biológicas.

Ceramic Injection Moulding (CIM) is an advanced powder processing technology launched three decades ago which has become a growing attractive alternative for new technical applications, such as thermal management and wireless charging. Porcelain-type ceramics can allow the introduction of new feedstocks into the CIM market at a competitive cost, in comparison with the conventional alumina and zirconia feedstocks. During the CIM manufacturing process, several factors related to the starting powder characteristics have an influence on the quality and properties of the final components, such as the mixing behaviour and the feedstock flow properties, as well as injection, debinding and sintering parameters. In this work, the viability of three porcelain-based powders to successfully achieve injectable mixtures for CIM is described. The mixing behaviour and the feedstocks flow behaviour as a function of its solids loading is evaluated. In this way, the ideal attributes for a CIM porcelain powder are discussed, studying the first process stages through to the production of a sintered component by injection moulding. Finally, density, hardness, bending strength and microstructural properties of the selected porcelain are investigated and a cost-efficient ceramic feedstock is suggested for aesthetic and electrical applications. Resumen: El moldeo por inyección de cerámica (en inglés, Ceramic Injection Moulding [CIM]) es una tecnología avanzada de conformado de polvos establecida hace tres décadas que recientemente se ha convertido en una atractiva alternativa para nuevas aplicaciones avanzadas, como la gestión térmica y la recarga inalámbrica de dispositivos. Las cerámicas de tipo porcelana permiten la introducción de nuevos feedstocks en el mercado CIM a precios más bajos en comparación con los tradicionales de alúmina y zircona. Existen varios factores que influyen en la calidad y las propiedades de los componentes finales en el procesado CIM y que están relacionados con las características del polvo de partida, como son el comportamiento durante el mezclado y la fluidez del feedstock, así como los parámetros de inyección, eliminación y sinterización. En este trabajo se describe la viabilidad de tres porcelanas para obtener mezclas inyectables que puedan procesarse con éxito mediante CIM. Se muestra la estabilización del par de torsión durante el proceso de mezclado, así como la fluidez de los diferentes feedstocks en función de la carga cerámica. Asimismo, se discuten las cualidades que idealmente se buscan en un polvo para ser procesados mediante CIM. Finalmente, se muestran los resultados obtenidos de densidad, propiedades microestructurales y propiedades mecánicas (dureza y resistencia a la flexión) de la porcelana seleccionada, y se demuestra que la mezcla inyectable diseñada a precio competitivo puede utilizarse para aplicaciones estéticas y eléctricas en futuros trabajos.

In this study, the effect of perlite from NW Turkey on the physical properties of ceramic tile bodies was investigated. The phases present in the raw materials were measured by X-ray diffraction while chemical analysis of the raw materials were determined by X-ray flouresence. Colour, water absorption and firing shrinkage of the raw materials were investigated. The data obtained from this study showed that the addition of NW Turkey perlites improved sintering behaviour of ceramic tile bodies, Therefore, alternative tile compositions were formulated using perlite as a substitute for common alkali bearing raw materials. The sintering behaviour of the standard bodies and that of the perlite containing bodies were characterized using a double-beam optical non-contact dilatometer. Moreover, the effect of perlite on firing shrinkage (%), water absorption (%), apparent porosity (%), apparent density (g/cm3), bending strength and colour values (L, a, b) were studied and resultant microstructures were characterized by X-ray diffraction (XRD) and scanning electron microscope studies (SEM). It was clearly observed that perlite improves sinterability of the tile bodies but increases the firing shrinkage due to the presence of water in its structure. The low thermal expansion values of the sintered bodies containing perlite makes it a visible raw material for porcelain stoneware tiles. Resumen: Se ha investigado el efecto de una perlita de la región de Biga (noroeste de Turquía) sobre las propiedades físicas de composiciones estándar de gres porcelánico. Las fases presentes en las materias primas y su composición química se han determinado por difracción de Rx y fluorescencia de Rx, respectivamente. También se determinó algunas propiedades físicas de las materias primas cocidas como el color, la contracción y la absorción de agua. Se han planteado composiciones alternativas empleando perlita como sustituto de materias primas aportadoras de óxidos alcalinos. El comportamiento en la sinterización de las composiciones propuestas ha sido evaluado por dilatometría. Además, también se ha estudiado el efecto de la perlita sobre las propiedades físicas de las piezas sinterizadas, así como sobre las fases y la microestructura de las mismas mediante difracción de Rx y microscopía electrónica de barrido. Se observó que la perlita mejora la sinterabilidad de las piezas, pero aumenta la contracción de cocción debido, en parte, al contenido de agua estructural de este mineral. Se observó claramente que la perlita mejora la sinterización de las de los azulejos, pero aumenta la contracción de cocción debido a la presencia de agua en su estructura. Los bajos valores de expansión térmica de piezas sinterizadas que contienen perlita lo convierten en una materia prima visible para las baldosas de gres porcelánico.

Present paper reports an approach to BaI2:Eu2+ glass ceramic fabrication from a powder route. The structural, morphological, luminescent and paramagnetic properties of the materials synthesized this way have been investigated. X-ray diffraction analysis made evidence for the glass ceramics containing BaI2·2H2O and BaI2 inclusions when 50 wt.% of the starting iodide powder had been used in the synthesis process. According to scanning electron microscopy, only two samples demonstrated presence of ceramics particles inside: those with initial mix of 25 and 50 wt.% of the BaI2:Eu2+. Photoluminescence spectra could be measured only in these samples. They were multicomponent as compared to the single band spectrum observed in the BaI2:Eu2+ powder. Altogether this indicates europium distribution over several places with different environments in the materials. BaI2 dissolution in the glass matrix is confirmed further by electron paramagnetic resonance measurements. They have shown that the Eu2+ ions predominantly stay in the glass avoiding ceramic grains. Only negligibly small amount presumably occupies the ceramic part in the sample with the initial 50 wt.% part of the BaI2 powder. The Eu2+ → Eu3+ charge transformation under 442 nm laser light irradiation has been observed in the glass ceramics as well. Resumen: Este artículo informa sobre el enfoque de síntesis de BaI2:Eu2+ vitrocerámica a partir de una ruta de polvo. Se han investigado las propiedades estructurales, morfológicas, luminiscentes y paramagnéticas de los materiales sintetizados de esta manera. El análisis de la difracción de rayos X había demostrado las vitrocerámicas que contienen inclusiones de BaI2·2H2O y BaI2 cuando el 50% en peso del polvo de yoduro se había utilizado en el proceso de síntesis. Según la microscopia electrónica de barrido, solo dos muestras demostraron la presencia de partículas de cerámica adentro: aquellas con una cantidad inicial del 25 y 50% en peso del BaI2:Eu2+. Los espectros de fotoluminiscencia solo se pudieron medir en estas muestras. Eran multicomponentes en comparación con el espectro de banda única observado en el polvo BaI2:Eu2+. En conjunto, esto indica la distribución de europio en varios lugares con diferentes ambientes en los materiales. La disolución de BaI2 en la matriz de vidrio se confirma, además, por mediciones de resonancia paramagnética electrónica. Han demostrado que los iones de Eu2+ permanecen predominantemente en el vidrio, evitando los gránulos de cerámica. Solo una cantidad insignificantemente pequeña ocupa presumiblemente la parte cerámica en la muestra con el 50% en peso del polvo inicial de BaI2. La transformación de carga de Eu2+→Eu3+ bajo irradiación de luz láser de 442 nm también se ha observado en la vitrocerámica.

Control of Ag electro chemical migration is crucial for long–term reliability of electrical components in high–voltage applications. In this work, Cu was bonded onto an AlN substrate at temperatures between 650 °C and 950 °C for 1 h using a Ag free Cu–P–Sn–Ni brazing filler metal with Ti as an active metal addition. The interfacial structure between the Cu and the AlN and the mechanical properties of the bond were both investigated. Three different phases which contain Ti and O were observed during the growth process of the Cu/AlN interfacial reaction layer: an amorphous P–Ti–O phase, an amorphous Ti–O phase and rutile, TiO2. The most stable Cu/AlN interfacial structure occurred when rutile was present, and where a particular orientation relationship with AlN was observed: TiO2 (101)//AlN (0001), TiO2 [010]//AlN [ $$11\overline{2}0$$ ]. The probability of Cu/AlN interfacial fracture decreased as the bonding temperature was increased. Cu/AlN interfacial fracture was completely suppressed above 850 °C where rutile was the dominant phase at the Cu/AlN interface.

Transparent and conductive Ti-doped In2O3 (TIO)/Ag/Ti-doped In2O3 (TAT) multilayer films were deposited on colorless poly imide (CPI) substrates by direct current (DC) and radio frequency (RF) magnetron sputtering at room temperature. During deposition the thickness of both the top and bottom TIO layer was fixed at 30 nm, while the thickness of the Ag interlayer was varied, to 5, 10, and 15 nm, to enhance the optical, electrical and mechanical properties of the films. In the XRD analysis the TIO films did not show any characteristic peaks in the diffraction pattern. The 10 nm thick Ag inter layer showed some characteristic peaks of Ag (111), (200), (220) and (311), respectively, and the grain size of the Ag interlayer enlarged as Ag thickness increased. To investigate the most efficient Ag interlayer thickness, a figure of merit (FOM) based on the opto-electrical performance of the transparent conducting films was compared. The films with a 10 nm thick Ag interlayer exhibited a higher FOM of 1.71 × 10-2 Ω-1 than the other films. When the radius of the film's curvature was reduced to 1.7 mm, the TIO single layer films showed a 13 times increase in sheet resistance, while the TAT (30/10/30 nm) films showed an insignificant change in sheet resistance. From the observed results, it was concluded that the Ag interlayer in the TAT multilayer films enhanced the opto-electrical performance of the films and also acted as a potent bridge which assured the high flexibility endurance of the films.

The bonding properties of adhesives are mainly affected by surface roughness, topography and chemical adsorption. In this paper, we studied the effects of surface pretreatment of Al 2024-T3 (bare) in terms of surface roughness, topography and surface free energy. Surface pre-treatment included solvent cleaning, FPL etching, PAA and CAA treatment. The surface energy and roughness of the aluminum surface were significantly increased by the anodizing treatment. Single lap shear and fatigue tests were performed to investigate bonding properties and durability. The evaluation revealed that the surface energy and surface roughness resulting from the aluminum surface treatment had a significant impact on bonding properties and durability. PAA treated surfaces had the highest bonding strength, and CAA treated surfaces had superior bonding retention performance in hot water or salt spray environments. The results of the fatigue test most clearly demonstrated how the surface pretreatment of the aluminum alloy differently affected bonding performance. (Received March 27, 2021; Accepted May 10, 2021)

This study proposed a constitutive equation to predict the change in yield strength according to the behavior of β″ metastable precipitates, which have a profound effect on strength among materials precipitated during the T6 heat treatment of Al-Mg-Si alloy. The β″ precipitate is a metastable phase before it becomes a β (Mg2Si) precipitate, and is distributed in the form of nano-scale rods in the aluminum alloy matrix. Existing precipitation strengthening models assume the shape of the precipitate to be spherical, and in that case the equation that depends on the Orowan mechanism with the average precipitate size and distribution should dominate. However, precipitates are formed in various shapes and sizes by anisotropic growth. In particular, rod-shaped precipitates are not suitable for the existing precipitation strengthening model. In this study, an Al-Mg-Si alloy was fabricated by gravity casting followed by T6 heat treatment. The new precipitation strengthening effect equation proposes that the β″ precipitate affects yield strength during plastic deformation of the Al-Mg-Si alloy. The proposed precipitation strengthening effect equation probabilistically considers the Critical Resolved Shear Stress (CRSS), which varies depending on the angle between the dislocation and the precipitate, when the dislocation passes through a rod-shaped precipitate.

This investigation aims to improving mechanical properties of normal concrete such as compressive strength, tensile strength, and flexural strength by using integral waterproof admixture (IWP) and also decreasing absorption of concrete, using different mix proportions of concrete, study shows a good increment of compressive strength for all mixes by using integral waterproof and also increasing the flexural and tensile strengths. The study contains also a sulfate attack study on normal mixes and integral waterproof mixes. Different percentages of IWP used in the study containing 0.0%, 1% ,1.5% and 2% for each 100 kg cement. Concrete mixes with 2% IWP admixture and 1:1:1.5 mix proportions give the highest values of compressive, tensile, and flexural strength in the study. compressive strength improved from 33.6MPa for reference 1:1:1.5 mix to 39.8 MPa by using IWP, also less absorption concrete obtained, the absorption was lowered from 3.5% to 1.7%, also deterioration in strength due to sulfate attack was small compared with reference mixes, same to other mixes 1:2:4, 1:1.5:3 that also improved by IWP admixture and lead to increasing mechanical properties and reducing absorption and sulfate attack.

There are a number of technical solutions to utilize the waste gases of electric arc furnaces (EAF) for scrap preheating thus returning back the heat into the technological process. The waste gases can be utilized also for steam or hot water production. The preliminary scrap heating before charging it into EAF is more perspective. Technical features of various types scrap heaters considered, including conveyer and shaft scrap heating technologies with continuous (Contiarc, Consteel, Comelt, BBC-Brusa) and periodic charging (Fuchs Systemtechnik, COSS, backet). It was shown that application of scrap heaters for EAF ensures saving of electric energy, increase of metal yield, decrease of dust and gases level in the shop, decrease of negative impact on environment. The disadvantages include frequent and costly repairs of the facilities, impossibility to control some factors having effect on the process of scrap heating. It was shown that when designing new EAFs with a charge exceeding 100 t, horizontal facilities are more preferrable, while for EAFs of small volumes shaft heaters suit better. At EAF modernizing it is recommended to use shaft heaters and back­et-thermos, since it is easier to construct a vertical furnace than a horizontal one with minimal length of 100 m. It was noted that hor­izontal heaters operate better in terms of technology, since ensure continuous charging by scrap, but at that occupy a considerable space in the shop. When comparing vertical heaters and backet by all the characteristics including heat-engineering and designingones, vertical shaft heaters prevail.