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Silica-based glass ceramics have been extensively used in biomedical applications due to their superior biocompatibility and controllable properties. However, their low mechanical strength limits their application. This could be addressed by optimizing the crystalline phase which determines their final properties. Silicon nitride has attracted attention due to its combination of good mechanical and biological properties. Therefore, to combine the advantage of silica-based glass and silicon nitride ceramic, this study developed a silicon nitridesilicon dioxide (Si3N4-SiO2) glass ceramics. The effects of spark plasma sintering parameters on the structural and mechanical properties of Si3N4-SiO2 glass ceramics were investigated. Full densification was reached at a sintering temperature of 1300 degrees C, a holding time of 10 min and an applied pressure of 80 MPa (relative density = 99.19 %). No silicon oxynitride (Si2N2O) crystalline phase was formed in the sintered glass ceramics, as confirmed by XRD. The interface between the (3-Si3N4 crystalline and amorphous SiO2 was investigated by HRTEM, and the results indicated that an amorphous interfacial oxide was formed at the interface. The mechanical properties increased with increasing sintering temperature, as a result of the increased density. The Si3N4-SiO2 glass ceramics sintered at 1500 degrees C exhibited the highest value of toughness and flexural strength, at 4.6 +/- 0.28 MPa m1/2 and 360 +/- 27 MPa. The indentation cracks observed by SEM showed that the large (3-Si3N4 grains promoted crack deflection, while the equiaxed Si3N4 grains with a lower aspect ratio led to transgranular fracture. The mechanical properties of these Si3N4-SiO2 glass ceramics are comparable to commercial glass ceramics, indicating their promising aspects in biomedical applications.

Borophosphosilicate glasses with varying sodium ion concentrations were investigated for their, structural, thermal, and electrical properties. All the obtained glasses were transparent except the glass with the highest sodium content, which exhibited translucency due to inhomogeneities. Increasing sodium content led to reduced boron and silicon content while maintaining a constant B/Si ratio, indicating progressive depolymerization of the glass network. Confocal microscopy, scanning electron microscopy, and atomic force microscopy showed homogeneous and granular structure for samples with lower sodium content, but higher sodium content resulted in visible agglomeration/nanocrystallization. X-ray diffractograms showed amorphous nature for most samples, with samples doped with the highest concentrations of Na2O showing several broad reflections suggesting nanoscale crystallinity. Fourier -transform infrared spectroscopy revealed shifts in dominant bands with increasing sodium content, indicating depolymerization of the borate network. An observed decrease in glass transition temperature and thermal stability with increasing sodium content was attributed to depolymerization and formation of non -bridging oxygens. Impedance spectroscopy revealed two relaxation processes associated with the transport of Na+ ions through two different regions. DC conductivity and activation energy predominantly increased with the sodium ion content at high temperatures.

Thin films of titanium vanadium nitride (Ti1´xVx N) were grown onto WC-Co sub-strates by reactive cathodic arc deposition. Three distinct cathodes were used resulting inseven different compositions for each of the four different substrate biases -25 V, -40 V, -80 V and -100 V. Characterisation was done to investigate the phase, texture, compositionand mechanical properties by X-ray diffractometry (XRD), scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy, nanoindentation and transmission electronmicroscopy (TEM). A fcc TiVN structure dominated for all samples. The texture of thesamples was calculated and a strong (1 1 1) texture for -80 V and -100 V substrate biasesand a nearly random texture for -25 V and -40 V were found. Coatings with a high vana-dium content had a (2 0 0) texture for all substrate biases. The samples showed an increasedstress at higher substrate biases, but a decreased stress for higher vanadium content. Allfilms with the highest vanadium content a low compressive stress for all substrate biases.A decreased number of macroparticles was found at larger substrate biases and higher tita-nium content. A columnar growth was observed for all films, the surface texture was foundto change with an increase in vanadium composition and substrate bias. The samples withhighest vanadium contents deposited at -80 V and -100 V showed an additional hexagonalphase. The hexagonal phase was not found to have any significant impact on hardness,but could influence the low stress of the highest vanadium content. The grain size showedno significant difference between the films except for the mixed phase samples which hadsmaller grains due to competitive growth. The hardness of the samples were found to belie between 28 and 31 GPa for low vanadium contents, but decreased quickly for largervanadium contents to 21 GPa at the highest vanadium content. All compositions showedan increase in hardness of 3 GPa when substrate bias was changed from -25 V to

The primary objective of this study is to explore the relationship between the composition, structure, and thermal characteristics of M-Al-Si-O-N glasses, with M representing sodium (Na), magnesium (Mg), or calcium (Ca). The glasses were prepared by melting in a quartz crucible at 1650 degrees C and AlN precursor (powder) was utilized as a nitrogen source. The measured thermal properties studied were glass transition temperature (Tg), crystallization temperature (Tc), glass stability, viscosity, and thermal expansion coefficient (alpha). The findings indicate that increasing the aluminum content leads to higher glass transition, crystallization temperatures, and viscosities. In contrast, fragility values increase with the Al contents, while modifier elements and silicon content influence thermal expansion coefficient values. FTIR analysis revealed that in all glasses, the dominant IR bands are attributed to the presence of Q2 and Q3 silicate units. The effect of Al is observed as a progressive polymerization of the silicate network resulting from the glass-forming role of Al2O3. In most samples, the Q4 silicate mode was also observed, strongly related to the high Al content. Overall, the study shows that the complexity of composition-property correlations where the structural changes affect the properties of Mg/Ca-based oxynitride glasses has potential implications for their use in various technological fields.

Zircon (ZrSiO4) ceramics have been widely used in many fields due to their excellent physical and chemical properties. However, ZrSiO4 ceramics typically possess moderately low mechanical properties, which hinders their wider application. Meanwhile, elevated temperatures (similar to 1500 degrees C) are required to obtain high-purity synthetic ZrSiO4 ceramics, which is time- and energy-consuming. In the present study, we prepared mechanically robust ZrSiO4 ceramics at low temperature (similar to 1170 degrees C) with a low doping level of Mn dopant (<2 mol%). The ZrSiO4 ceramic processed by hot isostatic pressing with .5 mol% Mn dopant achieved the highest flexural strength (512 MPa), elastic modulus (341 GPa), and nanohardness (20.8 GPa). These values are significantly higher than conventional ZrSiO4 ceramics. The strengthening mechanisms of the prepared ZrSiO4 ceramics were attributed to the formation of homogeneously-distributed nanopores due to incomplete densification and submicron ZrSiO4 grains (similar to 300 nm). The nanopores avoided stress concentration and deflected microcracks during loading, and the submicron ZrSiO4 grains endowed the ZrSiO4 ceramics with grain refinement strengthening. The results reported in this study would offer guidance to fabricate mechanically robust ZrSiO4 ceramics at low temperatures with a low doping level of dopant.

matt lambert writes on artist Trevor Novaks published exhibtion Exploratory Touch as an invited guest curator for C Mag issue 156 funded by the Royal Bank of Canada to focus on emerging artists.

This study demonstrates integration of a zeolite material in a ceramic microcomponent intended for use in sampling and analysis of environmental carbon dioxide (CO2). The zeolite material was integrated in bulk form, allowing for adsorption of large quantities of CO2 compared to previous integration attempts as thin films. To obtain a porous bulk material, an injectable slurry was developed, where expandable polymeric microspheres were added as a sacrificial template. By varying water and sphere contents of the slurry, it was possible to tune the porosity of the zeolite material between 55% and 72%. This in turn affected the flow resistance of the microcomponents, where an increase in the porosity of the filling from 62% to 72% reduced the flow resistance from 84 to 28 kPa min cm-3. In addition, the spheres facilitated complete fillings free from cracks. The zeolite material was seen to retain its ability to adsorb CO2 after processing, but it was not possible to quantify the level of retention compared to unprocessed zeolite.

Europium (Eu) ion-doped luminescent materials have attracted considerable attention for their numerous optical applications. Eu-doped Ca-Al-Si-O(-N) glasses were synthesized from a mixture of oxynitride glasses and Eu2O3 powder using a standard melt-quenching technique in a radiofrequency furnace. The source Eu trivalent ions primarily changed to Eu2+ during melting, and the ratio of Eu2+ ions increased with an increase in Eu content in the starting mixture. All the prepared glasses exhibited photoluminescence (PL) owing to the 5d-4f transition of Eu2+ ions. The absorption edge and PL wavelength shifted to longer wavelength with an increase in Eu content. Moreover, oxynitride glasses exhibited a longer wavelength than those of oxide glasses. The internal quantum efficiency (IQE) increased with the increase in Eu content until it reached a maximum. X-ray absorption structure and electron spin resonance spectroscopies were used to determine the local structure of Eu ions, which confirmed that changes in the local structure of Eu ions were responsible for the shift in PL peak and the change in IQE. The development of the Eu-doped Ca-Al-Si-O-N glasses is highly inspiring for transparent phosphors.

The oxidation of MAX phases has largely been investigated, but the effect of secondary phases and microstructure is still unclear. We report on the effect of reactive and non-reactive sintering, and starting powders, on the microstructure, phase formation, and chemical composition of Cr2AlC MAX phases. The grain sizes are shown to be sensitive to both the processing method and the starting powders. Secondary phases were observed mostly in reactively sintered samples as Cr7C3 and AlCr2 were identified, and Al contents varied between 24.4 and 28.0 at %. Finally, the oxidation behavior of the produced MAX phases was evaluated after 60 and 120 min at 1100 degrees C. The Al content, the average grain size of the as-sintered samples, and the presence of secondary phases affected the decomposition of the MAX phase into Cr-carbides in the vicinity of the oxide scale and the composition of the oxide scale, respectively., Funding Agencies|Region Nouvelle-Aquitaine; Ministe`re de l'Enseignement Superieur et de la Recherche; French government program "Investissements d'Avenir" [ANR-18-EURE-0010]; LABEX INTERACTIFS [ANR-11-LABEX-0017-01]

Amorphous iron-calcium phosphate (Fe-ACP) plays a vital role in the mechanical properties of teeth of some rodents, which are very hard, but its formation process and synthetic route remain unknown. Here, the synthesis and characterization of an iron-bearing amorphous calcium phosphate in the presence of ammonium iron citrate (AIC) are reported. The iron is distributed homogeneously on the nanometer scale in the resulting particles. The prepared Fe-ACP particles can be highly stable in aqueous media, including water, simulated body fluid, and acetate buffer solution (pH 4). In vitro study demonstrates that these particles have good biocompatibility and osteogenic properties. Subsequently, Spark Plasma Sintering (SPS) is utilized to consolidate the initial Fe-ACP powders. The results show that the hardness of the ceramics increases with the increase of iron content, but an excess of iron leads to a rapid decline in hardness. Calcium iron phosphate ceramics with a hardness of 4 GPa can be achieved, which is higher than that of human enamel. Furthermore, the ceramics composed of iron-calcium phosphates show enhanced acid resistance. This study provides a novel route to prepare Fe-ACP, and presents the potential role of Fe-ACP in biomineralization and as starting material to fabricate acid-resistant high-performance bioceramics.

The advantages that 3D printing brings to the development and production of customized structures make it suitable for use in the space industry, since spacecraft components are rarely produced in large series. This work explores the use of stereolithography printing of a silica resin for microfluidic applications, in particular small-scale microthrusters, where an impermeable high-temperature material with a smooth surface is required. The printing accuracy, firing shrinkage, surface roughness and permeability of 3D-printed ceramic samples were investigated. Furthermore, glazing of the ceramic material with a stoneware glaze was performed and evaluated with respect to its effect on surface roughness and gas permeability. Open microchannels with diameter down to 250 µm were obtained. However, the accuracy was poor. Surface roughness (Sa) of the unglazed material was between 2.4 and 20 µm in green state and 4.2-16 µm after firing, depending on the layer thickness and printing angle of the sample. Half of the unglazed samples were permeable, owing to porous areas at the interfaces between the printed layers. Two glazing methods were investigated: dip coating and airbrushing. For the latter, two amounts of coatings were explored. Dip coating and airbrushing with the larger amount of coatings resulted in uniform and smooth glaze layers. The smoothest surfaces, with Sa less than 0.2 µm, were obtained using airbrushing. Glazing made all samples impermeable, no matter the method used. Finally, the potential of the material in the suggested application was demonstrated through operation of a printed and glazed microthruster nozzle.

Custom made glass fabrication often requires highly skilled scientific glass blowers, or advanced processing techniques and access to clean-room technologies. Additive manufacturing, or 3D printing, of optical quality glass structures would be a valuable complementary approach and is highly sought after. However, 3D printing glass has proven to be a significant challenge with the main issues related to the high temperatures associated with glass processing, stress and crack formation due to thermal expansion and brittleness. Early attempts using laser sintering of glass powder, either dry or using binding agents [1], resulted in opaque glass following debinding and sintering. Today optically clear glass has been reported using different techniques, including filament based [2], extrusion [3], and light curable resins mixed with nano-powders [4], among others [5]., Part of ISBN 9798350345995QC 20231116

Among the existing materials for heat conversion, high-entropy alloys are of great interest due to the tunability of their functional properties. Here, we aim to produce single-phase high-entropy oxides composed of Co-Cr-Fe-Mn-Ni-O through spark plasma sintering (SPS), testing their thermoelectric (TE) properties. This material was successfully obtained before via a different technique, which requires a very long processing time. Hence, the main target of this work is to apply spark plasma sintering, a much faster and scalable process. The samples were sintered in the temperature range of 1200-1300 degrees C. Two main phases were formed: rock salt-structured Fm (3) over barm and spinel-structured Fd (3) over barm. Comparable transport properties were achieved via the new approach: the highest value of the Seebeck coefficient reached -112.6 mu V/K at room temperature, compared to -150 mu V/K reported before; electrical properties at high temperatures are close to the properties of the single-phase material (sigma = 0.2148 S/cm, sigma approximate to 0.2009 S/cm reported before). These results indicate that SPS can be successfully applied to produce highly efficient TE high-entropy alloys in a fast and scalable way. Further optimization is needed for the production of single-phase materials, which are expected to exhibit an even better TE functionality., Funding Agencies|Knut & Alice Wallenberg Foundation; Swedish Foundations Consolidator Fellowship; L T U Lab fund program; Kempe Foundation

Cobalt chromium alloys (CoCr) are commonly used as total disc replacement components. However, there are concerns about its long-term biological effects. Coating the CoCr with a ceramic could improve the implant’s biocompatibility and wear resistance. Silicon nitride (SiNx) coatings have emerged as a recent alternative to this end. While many have evaluated physical vapour deposition (PVD) techniques to deposit these coatings, plasma-enhanced chemical vapour deposition (PECVD) may provide certain advantages. For example, it may allow for low-temperature depositions as well as more uniform coatings of complex structures. In this study, silicon nitride (SiNx) coatings with different nitrogen-to-silicon (N/Si ratio) compositions (0.65, 1.16 and 1.42) were deposited onto CoCr substrates by PECVD. It was found that the SiNx coating deposited at an NH3 flow rate of 30 sccm (i.e., N/Si ratio of 1.42), had the highest hardness and elastic modulus, 13.19 ± 1.29 GPa and 132.76 ± 9.32 GPa, respectively. While a coating roughness adequate for the application could be measured, further optimization of the coating adhesion is needed to adequately evaluate its wear properties. It was concluded that the PECVD SiNx coating deposited at an NH3 flow rate of 30 sccm showed the highest potential for the intended application.

Liquid-phase sintering (LPS) is an effective pathway to assist the densification of ceramics. However, it has seldom been used to densify glass-ceramics. In the present study, a multielement co-doping strategy has been utilized to achieve LPS of a ZrO2-SiO2 nanocrystalline glass-ceramic. Compared with undoped samples densified by solid-state sintering, doping of equimolar Al, Y, and Ca promoted the densification of the glass-ceramic at lower temperatures with a faster densification rate. Ternary doping enhanced coarsening of ZrO2 nanocrystallites during sintering and annealing. The distribution of dopants was carefully observed with X-ray energy-dispersive spectrometry technique in scanning electron transmission microscopy mode. Results showed that the three dopants showed different distribution behaviors. After sintering, Y dopants were predominately distributed in ZrO2 nanocrystallites, whereas parts of Al and Ca dopants were distributed in ZrO2 nanocrystallites and part of them co-segregated at the ZrO2/SiO2 heterointerfaces. Meanwhile, the segregation of Ca dopant at some intergranular films among ZrO2 nanocrystallites was observed. Redistribution of dopants did not occur during annealing.

In this work, an aerodynamic levitation technology (ALT) was utilized to prepare ZrO2-SiO2 glass-ceramics with two different ZrO2 contents, that is, 35 mol% and 50 mol%. The glass-ceramics were partially melted at similar to 2000 degrees C or fully melted at similar to 3000 degrees C by ALT, followed by rapid quenching to obtain spherical glass-ceramic beads. The phase compositions and microstructures of the glass-ceramics were characterized. Crystallization of ZrO2 occurred during the solidification process and ZrO2 content, processing temperature, and the addition of yttrium (3 mol%) affected the crystalline phase of ZrO2. No ZrSiO4 or crystalline SiO2 were formed during the solidification process and the glass-ceramics were away from thermodynamic equilibrium due to rapid quenching. The glass-ceramics showed a microstructure of irregular-shaped ZrO2 micro-aggregates embedded in an amorphous SiO2 matrix, with lamellar twins and lattice defects formed within ZrO2 crystals. For samples prepared at similar to 3000 degrees C, a liquid-liquid phase separation occurred in the melt, which eventually resulted in the formation of large and irregular-shaped ZrO2 aggregates. In comparison, for samples prepared at similar to 2000 degrees C, pre-existed ZrO2 crystals formed during heating acted as nucleation sites during the cooling process, followed by grain growth to form large ZrO2 aggregates. Solidification and microstructure formation mechanisms were proposed to elucidate the solidification process during rapid cooling and the microstructure of the glass-ceramics obtained.

Developing new radiation-resistant materials and understanding the structural damages caused by radiation are persistent goals of material scientists. Here, we report on the structural integrity and damage to ZrO2-SiO2 nanocrystalline glass-ceramics after radiation with 1.4 MeV He ions at three different fluences: 1.0 x 1016 ions/ cm2 (low), 5.0 x 1016 ions/cm2 (moderate), and 1.0 x 1017 ions/cm2 (high) at 500 degrees C. Grazing incident X-ray diffraction shows the tetragonal-ZrO2 to monoclinic-ZrO2 phase transformation induced by microstrain from the irradiation. The addition of yttrium indicated tetragonal-ZrO2 stabilization effect during irradiation. The irra-diated glass-ceramics show a Raman signal-enhancement effect probably related to the electronic structure changes of the amorphous SiO2 component in the glass-ceramics. The formation of microcracks and lattice de-fects within ZrO2 nanocrystallites is the main structural damage caused by irradiation. There was no observable amorphization of ZrO2 nanocrystallites due to irradiation. No obvious He bubbles were detected, either. The formation of microcracks results in a decrease of in the nanohardness of the glass-ceramics. The results provide fundamental experimental data to understand the structural integrity and damage caused by radiation, which could be useful to design radiation-resistant nanocrystalline glass-ceramics for extremely radioactive environments.

The zero resonant frequency temperature coefficient (zf) of microwave dielectric ceramics (MWDCs) at high and low temperature have attracted great attention in the development of microwave communication equipment. In this work, the Mg2TiO4-MgTiO3-CaTiO3 (MMC) ceramics with meeting the application requirements of 5G communication were prepared by traditional solid-phase sintering after investigating the relationship among phase compositions of xMg2TiO4-(0.931-x)MgTiO3-0.069CaTiO3 and 0.34Mg2TiO4-0.591MgTiO3-yCaTiO3, sin-tering process, and dielectric properties in detail. The results show that the dielectric properties of MMC ceramics are strongly affected by the phase relative contents of MgTiO3, Mg2TiO4 and CaTiO3. For instance, MMC ceramics with approximate zf = 0 is contributed by mutual compensation of Mg2TiO4 and MgTiO3, in which the Mg2TiO4 phase plays an important role in decreasing the zf value; and the increase of CaTiO3 will greatly increase the epsilon r value for MMC ceramics, while has a negative effect in the Q x f value. After three-phase regulation, the 0.32Mg2TiO4-0.611MgTiO3-0.069CaTiO3 microwave dielectric ceramic has a better dielectric temperature sta-bility, associated with dielectric properties of er = 19.7, Q x f = 55,400 GHz (at 8.43 GHz), zf-= 4.5 ppm/degrees C (-40 degrees C-25 degrees C), and zf+ =-5.1 ppm/degrees C (25 degrees C-90 degrees C).

QC 20230215

We explore the formation and composition–structure–property correlations of transparent Ca–Al–Si–O–N glasses, which were prepared by a standard melt-quenching technique using AlN as the nitrogen source and incorporating up to 8 at.% of N. Their measured physical properties of density, molar volume, compactness, refractive index, and hardness—along with the Young, shear, and bulk elastic moduli—depended roughly linearly on the N content. These effects are attributed primarily to the improved glass-network cross-linking from N compared to O, rather than the formation of higher-coordination AlO5 and AlO6 groups, where 27Al magic-angle-spinning nuclear magnetic resonance experimentation revealed that aluminum is predominately present in tetrahedral coordination as AlO4 units. Yet, several physical properties, such as the refractive index along with the bulk, shear, and Young's elastic moduli, increase concomitantly with the Al content of the glass. We discuss the incompletely understood mechanical–property boosting role of Al as observed both herein and in previous reports on oxynitride glasses, moreover suggesting glass-composition domains that are likely to offer optimal mechanical properties.

In this thesis, I have explored the possibilities of what furniture can look like on a moon base. How they will be made and what resources to use. What will the living conditions be like and why producing on a faraway place is important for future interstellar missions. By combining art and design, I will present a realistic concept that fits the need of the astronauts stationed on the moon and know what one might need when on a moon station.

Ultrafast high-temperature sintering (UHS) is a novel sintering technique with ultrashort firing cycles (e.g., a few tens of seconds). The feasibility of UHS has been validated on several ceramics and metals; however, its potential in consolidating glass-ceramics has not yet been demonstrated. In this work, an optimized carbon-free UHS was utilized to prepare ZrO2-SiO2 nanocrystalline glass-ceramics (NCGCs). The phase composition, grain size, densification behavior, and microstructures of NCGCs prepared by UHS were investigated and compared with those of samples sintered by pressureless sintering. Results showed that NCGCs with a high relative density (similar to 95%) can be obtained within similar to 50 s discharge time by UHS. The UHS processing not only hindered the formation of ZrSiO4 and cristobalite but also enhanced the stabilization of t-ZrO2. Meanwhile, owing to the ultrashort firing cycles, the UHS technology allowed the NCGCs to be consolidated in a far from equilibrium state. The NCGCs showed a microstructure of spherical monocrystalline ZrO2 nanocrystallites embedded in an amorphous SiO2 matrix.

Thermal shock resistance is one of the performance-defining properties for applications where extreme temperature gradients are required. The thermal shock resistance of a material can be described by means of the thermal shock parameter RT. Here, the thermo-mechanical properties required for the calculation of RT are quantum-mechanically predicted, experimentally determined, and compared for Ti3AlC2 and Cr2AlC MAX phases. The coatings are synthesized utilizing direct current magnetron sputtering without additional heating, followed by vacuum annealing. It is shown that the RT of both Ti3AlC2 and Cr2AlC obtained via simulations are in good agreement with the experimentally obtained ones. Comparing the MAX phase coatings, both experiments and simulations indicate superior thermal shock behavior of Ti3AlC2 compared to Cr2AlC, attributed primarily to the larger linear coefficient of thermal expansion of Cr2AlC. The results presented herein underline the potential of ab initio calculations for predicting the thermal shock behavior of ionically-covalently bonded materials.

Synthetic zircon (ZrSiO4) ceramics are typically fabricated at elevated temperatures (over 1500 degrees C), which would lead to high manufacturing cost. Meanwhile, reports about preparing ZrSiO4-based ceramic composites via controlling the solid-state reaction between zirconia (ZrO2) and silica (SiO2) are limited. In this work, we proposed a low-temperature strategy to flexibly design and fabricate ZrSiO4-based ceramic composites via doping and tuning the solid-state reaction. Two ceramic composites and ZrSiO4 ceramics were in-situ prepared by reactive fast hot pressing (FHP) at approximately 1250 degrees C based on the proposed strategy, i.e., a ZrSiO4-SiO2 dual-phase composite with bicontinuous interpenetrating and hierarchical microstructures, a ZrSiO4-ZrO2 dual-phase composite with a microstructure of ZrO2 submicron- and nano-particles embedded in a micron ZrSiO4 matrix, and ZrSiO4 ceramics with a small amount of residual ZrO2 nanoparticles. The results showed that the phase compositions, microstructure configurations, mechanical properties, and wear resistance of the materials can be flexibly regulated by the proposed strategy. Hence, ZrSiO4-based ceramic composites with different properties can be easily fabricated based on different application scenarios. These findings would offer useful guidance for researchers to flexibly fabricate ZrSiO4-based ceramic composites at low temperatures and tailor their microstructures and properties through doping and tuning the solid-state reaction.

Medium- and high-entropy carbides (MECs and HECs) have a wide range of advanced applications and, in many cases, outperform monocarbides. However, the behavior, oxidation mechanisms, and factors defining oxidation resistance of some popular HECs at high temperatures have not been studied in detail yet. In this study, the oxidation behavior of MEC and HECs including (Ta,Ti,Nb,Zr)C, (Ta,Ti,Nb,Zr,Mo)C, (Ta,Ti,Nb,Zr,Hf)C, and (Ta,Ti,Nb,Zr,W)C was investigated under both non-isothermal and isothermal conditions at temperatures up to 1200 °C, and a possible oxidation path was described. It was found that under non-isothermal heating conditions, the oxidation of HECs occurred in three stages, each governed by first-order chemical reactions, and was limited by the formation of ZrO2, Me2Me6O17, and MeMe2O7 oxides, respectively. In the case of isothermal heating, the oxidation of (Ta,Ti,Nb,Zr)C, (Ta,Ti,Nb,Zr,Mo)C, and (Ta,Ti,Nb,Zr,Hf)C follows a logarithmic law and was limited by the formation of a protective Me2Me6O17 layer. In contrast, isothermal oxidation of (Ta,Ti,Nb,Zr,W)C followed a linear law due to the formation of volatile WO3. The results of the study have a high potential for practical application for the production of HEC ceramics for various high-temperature purposes and could be used for further understanding of functional characteristics and development of the new ceramic compositions., QC 20230614

Limestone is calcined into quicklime in lime kilns at temperatures above 1000°C. Heat is supplied through combustion inside the kilns, which are insulated with a lining of refractory bricks to mitigate heat loss and to protect the kiln from the hot, chemically aggressive, and mechanically abrasive environment. While magnesia bricks have proven to be effective lining materials, they are still susceptible to extensive wear in lime kilns, especially in the burn zone. Refractory corrosion, in particular, can occur when melted fuel ash infiltrates the refractory materials through pores and small cracks. This resultant wear can lead to high maintenance and operational costs, often due to unplanned kiln shutdowns. To reduce the release of fossil-based carbon dioxide into the atmosphere from lime production kilns, there is a growing interest in introducing bio-based fuels with only relatively minor modifications to the process. Biomass fuels can be sourced from bio-based waste streams from industries or be specifically cultivated for combustion. However, the ash content and properties of bio-based fuels tend to be problematic from an ash chemistry perspective. Therefore, before introducing a new fuel source, it is essential to investigate its potential effects on the kiln lining material. In this thesis work, the interactions between melted olive pomace ash and coal ash with commercially available magnesia refractory materials, primarily composed of periclase (MgO) with minor amounts of spinel (MgAl2O4), were studied. A procedure for quantifying the intrusion depths was described. Refractory samples were exposed to the fuel ashes under a simulated lime kiln atmosphere with high CO2 levels at 1200 and 1400°C for 15 and 60 minutes. Cold crushing strength tests were conducted on refractory samples exposed to coal and olive pomace ash, along with CaO powder, at 1400°C for 96 hours. Additionally, postmortem analyses of spent MgO-based refractory bricks were carried out to inves

Chicken eggshells (eggshells) are the bio-waste produced during day-to-day egg consumption by humans. The eggshell contains calcium carbonate (CaCO3) along with several other elements such as Si, Mg, K, P, Na, etc., which enables its application for human bio-implants. Our research work aims to practically implement the eggshell powder as the bio-implant, for which, the study of the densification behavior of the eggshell powder is required. Hence, the present paper represents the densification behavior of the crystalline eggshell powder by spark plasma sintering. The eggshell powders were irregular in shape with a wide particle size distribution. The eggshell powder was sintered at six varying temperatures, i.e., 250 °C, 500 °C, 750 °C, 850 °C, 900 °C, and 1000 °C. The consolidated samples were characterized through SEM, FTIR, and XRD analysis, and the optimum spark plasma sintering temperature was determined. The consolidation of eggshells at 850 °C not only avoids the calcination process (due to the application of pressure) but gives optimum density and hardness making it an optimum condition for consolidating eggshells into compacts.

The impact of the crystallinity on structural, thermal, and in vitro dissolution properties were examined for Na2O-CaO-Nb2O5/MgO-P2O5 glasses/glass-ceramics. Glass-ceramics were synthesized via a spontaneous crystallization process. The Nb content in the materials increased with melting temperature, furthermore, the crystallinity is proportional to the Nb content. The presence of crystalline niobates and phosphates is confirmed by FTIR analysis which is consistent with XRD. The FTIR results indicate that the phosphate network is built of different proportions of Q2, Q1, and Q0 units, depending on the amount and type of crystalline phase. Most of the samples show an improvement in thermal stability. The in vitro dissolution test showed that the highest mass loss for most of the samples occurred during the first 6 days of immersion in the PBS solution. The presence of small phosphate crystals favors the deposition of hydroxyapatite on samples' surfaces while the larger niobate crystals dissolve more readily.

The controlled nanocrystallization of sodium-calcium-borophosphate glass (Na16.6Ca5.1B10.5Al0.8P10.5 O56.5 in at %) was conducted to investigate its influence on in vitro dissolution. Three temperatures (570 degrees C, 590 degrees C, and 610 degrees C) were selected based on thermal analysis and investigation of the morphology, structure, and in vitro dissolution of glass and glass-ceramics was conducted. The results of X-ray diffraction confirmed the presence of calcium phosphates nanocrystallites in glass-ceramics, with their contents increasing proportionally to the crystallization temperature. Infrared spectroscopy showed the presence of phosphate and borate network units, along with phosphates in a crystalline form. It was found that the target glass shows the highest mass loss in comparison to the glass-ceramics. Controlled nanocrystallization slowed down the dissolution of the materials (>10%), but did not adversely affect the deposition of hydroxyapatite layer. The presence of calcium phosphate nanocrystallites favors the process of B3+ release. The nanocrystallization of borophosphate glasses is a perspective tool for controlling the rate of dissolution of bioactive materials and enhancing their ability to de-posit hydroxyapatite on their surface.

Mg3Sb2-based thermoelectric materials attract attention for applications near room temperature. Here, Mg-Bi films were synthesized using magnetron sputtering at deposition temperatures from room temperature to 400 & DEG;C. Single-phase Mg3Bi2 thin films were grown on c-plane-oriented sapphire and Si(100) substrates at a low deposition temperature of 200 & DEG;C. The Mg3Bi2 films grew epitaxially on c-sapphire and fiber-textured on Si(100). The orientation relationships for the Mg3Bi2 film with respect to the c-sapphire substrate are (0001) Mg3Bi2||(0001) Al2O3 and [11 2 over bar 0] Mg3Bi2||[11 2 over bar 0] Al2O3. The observed epitaxy is consistent with the relatively high work of separation, calculated by the density functional theory, of 6.92 J m(-2) for the Mg3Bi2 (0001)/Al2O3 (0001) interface. Mg3Bi2 films exhibited an in-plane electrical resistivity of 34 mu omega m and a Seebeck coefficient of +82.5 mu V K-1, yielding a thermoelectric power factor of 200 mu W m(-1) K-2 near room temperature., Funding Agencies|Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program [KAW-2020.0196]; Swedish Research Council (VR)Swedish Research Council [2016-03365, 2021-03826, 2018-05973]; National Key Research and Development Program of China [2018YFB0703600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [51872133]; Guangdong Innovative and Entrepreneurial Research Team Program [2016ZT06G587]; Tencent Foundation through XPLORER PRIZE [2021B1212040001]

CaCu3Ti4O12 ceramics have great dielectric constant, excellent temperature stability and good frequency stability. However, due to high dielectric loss, its practical application in engineering is hindered. In this paper, Na0.25Bi0.25LaxCa0.5-3x/2Cu3Ti4O12 (NBLCCTO) ceramics were prepared by solid phase synthesis. The effects of sintering temperature and La content on dielectric properties of NBLCCTO ceramics were studied. The results show when the sintering temperature is 1030celcius and La content is 0.05, NBLCCTO ceramics show better dielectric properties. Its dielectric constant has epsilon(r) = 22,231 at 1 kHz and its dielectric loss is 0.0546 at 10 kHz. Appropriate doping of La can lead to grain refinement and enlarge specific surface area of grain boundary, thus increasing resistivity and reducing dielectric loss. Therefore, NBLCCTO ceramics have lower dielectric loss than Na0.25Bi0.25Ca0.5Cu3Ti4O12 (NBCCTO).

Calcium phosphate cements (CPCs) are attractive synthetic bone grafts as they possess osteoconductive andosteoinductive properties. Their biomimetic synthesis grants them an intrinsic nano- and microporosity thatresembles natural bone and is paramount for biological processes such as protein adhesion, which can laterenhance cell adhesion. However, a main limitation of CPCs is the lack of macroporosity, which is crucial to allowcell colonization throughout the scaffold. Moreover, CPCs lack specific motifs to guide cell interactions throughtheir membrane proteins. In this study, we explore a strategy targeting simultaneously both macroporosity andcell binding motifs within CPCs by the use of recombinant silk. A silk protein functionalized with the cell bindingmotif RGD serves as foaming template of CPCs to achieve biomimetic hydroxyapatite (HA) scaffolds withmultiscale porosity. The synergies of RGD-motifs in the silk macroporous template and the biomimetic features ofHA are explored for their potential to enhance mesenchymal stem cell adhesion, proliferation, migration anddifferentiation. Macroporous Silk-HA scaffolds improve initial cell adhesion compared to a macroporous HA inthe absence of silk, and importantly, the presence of silk greatly enhances cell migration into the scaffold.Additionally, cell proliferation and osteogenic differentiation are achieved in the scaffolds.

The content of crystalline phase plays a significant role in manipulating the microstructure and mechanical properties of glass-ceramics. This study aims at exploring the optimum content of crystalline phase in ZrO2-SiO2 nanocrystalline glass-ceramics (NCGCs) in terms of obtaining the highest mechanical properties. To this end, the mechanical properties of ZrO2-SiO2 NCGCs with 70 mol%, 75 mol%, 80 mol% ZrO2 were tested and compared with those of the previously prepared NCGCs with ZrO2 content ranging from 35 mol% to 65 mol%. Results showed that 65 mol% was the optimum content of ZrO2 in terms of obtaining the highest flexural strength. The flexural strength of NCGCs with ZrO2 content over 65 mol% was lower than that of the NCGCs with 65 mol% ZrO2. This was because the NCGC with 65 mol% ZrO2 had a homogenous microstructure, with ZrO2 nano crystallites homogeneously distributed in an amorphous SiO2 matrix. Whereas, when ZrO2 content was increased to 75 mol%, ZrO2 nanocrystallites were not homogeneously distributed in the SiO2 matrix anymore. The formation of SiO2 "holes/canyon " due to ZrO2 grain coalescence resulted in the decrease of flexural strength. The fracture mechanism and wear properties of the NCGCs were also investigated.

Effects of dopants with different valences on the densification behavior and phase composition of a ZrO2-SiO2 nanocrystalline glass-ceramic (NCGC) during pressureless sintering were investigated in this study. The raw powder of Ca2+, La3+, Ce4+ and Ta5+ ions doped ZrO2-SiO2 (referred to as Ca-ZS, La-ZS, Ce-ZS, Ta-ZS, respectively) and pure ZrO2-SiO2 (PZS) sample were synthesized by sol-gel method, followed by pressureless sintering. Compared with the PZS sample, doping of Ca2+ and La3+ ions significantly promoted the densification of the NCGCs. The "densification promotion " effect was attributed to the formation of oxygen vacancies and the decrease of SiO2 viscosity due to doping of aliovalent cations. The dopants with various valences showed significant effects on the phase compositions of the NCGCs during sintering. Doping of Ca2+ ion accelerated the reaction kinetics between ZrO2 nanocrystallites and amorphous SiO2 to yield ZrSiO4. The La3+ ion acted as destabilizer of t-ZrO2, which resulted in a rapid tetragonal (t) to monoclinic (m) ZrO2 phase transformation during sintering, while in the Ta5+ and Ce4+ ions doped sample, the phase transformation occurred gradually. All the doping ions increased the lattice parameters and the volume of t-ZrO2 unit cell, while the effects of the doping ions on the lattice parameters of m-ZrO2 unit cell were more complex.

The addition of dopant(s) is an effective strategy to regulate the microstructure and properties of ZrO2-based ceramics. In this study, we investigated the effects of ternary element alloying, namely tantalum (Ta), niobium (Nb), and hafnium (Hf) elements, on the microstructure and transformability of ZrO2 nanocrystallites in a ZrO2SiO2 nanocrystalline glass-ceramic (NCGC) during sintering and thermal treatments. The ternary dopants enhanced the transformability of tetragonal ZrO2 (t-ZrO2) nanocrystallites during sintering, i.e., the dopants acted as t-ZrO2 destabilizer. The Ta, Nb and Hf elements dissolved in ZrO2 nanocrystallites, forming ZrO2 solid solution. Meanwhile, lamella nanotwins were formed within many ZrO2 nanocrystallites. No obvious segregation of dopants was detected at ZrO2 grain boundaries. t-ZrO2 and monoclinic (m) ZrO2 nanocrystallites were metastable in thermal treatments process, with "t" to "m" and the reverse "m" to "t" polymorphic transformation occurred simultaneously. Meanwhile, t-ZrO2 and m-ZrO2 nanocrystallites had a great tendency to grow larger during thermal treatments.

It is challenging to develop a material that combines good mechanical properties and high translucency since these properties are generally not coincident in one material. In this study, we prepared ZrO2-SiO2 nano crystalline glass-ceramics that combines the above two types of properties. Raw powder with 55 mol%, 65 mol%, and 75 mol% ZrO2 and each with 5 mol% yttrium as a dopant was prepared by sol-gel method, followed by spark plasma sintering to obtain dense glass-ceramics. XRD results demonstrated that the glass-ceramics with 65 mol% and 75 mol% ZrO2 were composed of tetragonal-ZrO2, whereas, that with 55 mol% ZrO2 was composed of cubicZrO(2). The as-sintered glass-ceramics showed black/brown discoloration, but they obtained high translucency after thermal treatment. X-ray energy-dispersive spectrometry (EDS) results in scanning electron transmission microscopy (STEM) mode demonstrated yttrium dopants were predominately distributed in ZrO2 nano crystallites. The glass-ceramics with 65 mol% ZrO2 had the highest flexural strength, achieving an average value of 673 MPa. The glass-ceramics with different compositions sintered at different temperatures showed fracture toughness values ranging from 5.25 MPa m(1/2) to 6.69 MPa m(1/2). The strong and translucent ZrO2-SiO2 nano crystalline glass-ceramics showing great protentional to be used in many fields.

The safe treatment and disposal of radioactive graphite waste is becoming an important issue worldwide. The objective of this paper is to prepare the SiC-ZAC (ZAC: ZnO-Al2O3-CaO) composite ceramic for immobilizing radioactive graphite, where ZAC is as sintering additives. The effects of the sintering system and ZAC content on the phase compositions, microstructure, and properties of SiC-ZAC composite ceramic are studied by XRD, SEM-EDS, TEM-EDS, linear shrinkage, Vickers hardness, and thermal conductivity. By vacuum hot pressing sintering at 1600 degrees C for 1 h, the results show that the S-35-160 0 (65 wt% SiC, 10.5 wt% ZnO, 15.72 wt% Al2O3, 8.78 wt% CaO) sample is the potentially applicable formula composition due to its better performance, in which the Vickers hardness and the thermal conductivity are 165.2 HV10, 14.6 W m(-1) k(-1) respectively, and the normalized elemental mass loss of Si, Al and Ca are 0.0064-0.0108 g/m(2), 21.4784-24.7837 g/m(2), 56.9108-67.5637 g/m(2) after 42 days at pH = 5/7/9 solution, respectively. Importantly, ZAC sintering additives can form the bond phases of CaAl4O7, CaAl2O4, Ca3Al2(OH)(12), and Ca2Al2SiO7 under relatively low temperatures to reduce the sintering temperature for SiC ceramics. Meanwhile, the existing form of the Zn element is revealed: one part of the Zn forms glass phase, and the other part volatilized by carbothermic reduction.

In vitro dissolution, structure, and thermal properties of the glass series Na2O-MgO CaO Nb2O5 -Al2O3-P2O5 were studied. The dissolution behavior in phosphate-buffered saline (PBS) confirmed the potential bioactive properties of tested glasses. The dissolution process was found to depend on the Al, Nb, and Mg contents. Al, respectively, suppresses the Nb and accelerates the Mg release process from the glasses. Moreover, Al stays highly bonded in the phosphate network during 14 days of immersion. In all glasses, the phosphate network was found to be highly disrupted and built mostly of Q1 units. Al and Mg addition decreases the polymerization of the glass network. The Nb addition effect was found to be the opposite. Thermal properties were correlated mostly with the Nb and Al contents. However, the fragility index of glasses increases with the content of P and Al.

This paper investigates how the composition of Portland composite cements affects their chloride-binding properties. Hydrated cement pastes prepared with a reference Portland cement and composite Portland cements containing metakaolin and/or silica fume were exposed to NaCl or CaCl2 solutions. Chloride-binding isotherms were determined and the hydrate assemblage was investigated using TGA, XRD, 27Al NMR, 29Si NMR and thermodynamic modelling. Compared to the reference Portland cement paste, silica fume replacement did not alter the chloride-binding capacity. The metakaolin replacement resulted in the highest chloride-binding capacity. When combining silica fume with metakaolin, the chloride binding is similar to the reference Portland cement. In this study the differences in chloride binding were linked not only to changes in the AFm content, but also to alterations in the Al-uptake and chain length of the C(-A)-S-H.

In the year of 2022, which falls during an age of transition towards sustainability, the United Nations’ seventeen global goals define the direction of development. Materials development is an important component of sustainable development and innovation. The latter is conventionally defined as the implementation of creative ideas that are introduced into society in the form of services or goods. However, in order for innovations to arise, innovators are required. An innovator is a person or a group who introduces something novel, e.g., a method, an idea, or a product, or does something for the first time. The term pioneer is frequently used to describe an innovator who creates a paradigm shift, but innovators are also those who contribute incremental ideas that eventually combine to produce innovations. This model of incremental and disruptive innovation draws a simple distinction, but we stress that both types of innovators are needed to drive sustainable development., Funding: Forskningsrådet Formas 2018-00707, Tunnare och starkare glas för hållbar produktion och konsumtion

The transport properties of dense QCD matter play a crucial role in the physics of neutron stars and their mergers but are notoriously difficult to study with traditional quantum field theory tools. Specializing to the case of unpaired quark matter in beta equilibrium, we approach the problem through the machinery of holography, in particular the V-QCD and D3-D7 models, and derive results for the electrical and thermal conductivities and the shear and bulk viscosities. In addition we compare the bulk to shear viscosity ratio to the speed of sound and find that it violates the so-called Buchel bound. Our results differ dramatically from earlier predictions of perturbative QCD, the root causes and implications of which we analyze in detail., QC 20220524

Here we design a novel multi-principal element carbide system (Ti,Zr,Hf,W)C with a miscibility gap using computational tools and report on the formation of a single-phase (Ti,Zr,Hf,W)C after spark plasma sintering. The (Ti,Zr,Hf,W)C shows high nanohardness (32.7 GPa) and fracture toughness (5 MPa·m1/2). Aging studies at 1350 °C for 100 h show that the single-phase carbide solid solution is quite stable even though this temperature is within the predicted miscibility gap of the system. Detailed electron microscopy characterization shows that phase separation has initiated with minor decomposition after aging by forming rock-salt (Ti,W)C- and (Zr,Hf)C-rich phases as well as hexagonal WC precipitates. We show that the (Ti,W)C- and (Zr,Hf)C-rich phases form a lamellar structure upon aging and the interlamellar spacing is considerably coarser than what has been previously found for the binary (Ti,Zr)C system. The decomposition kinetics, on the other hand, is sluggish due to the reduced driving force for phase decomposition., QC 20230322

Ionic thermoelectric materials have recently aroused intense research interest because of their promising potential for heat en-ergy conversion. In a recent Cell Reports Physical Science article, Ma et al. presented a comprehensive study of the evaluation param-eters from the view of field evolutions of temperature, voltage, and ionic concentration., Funding Agencies|Swedish Research Council; [VR 2018-04037]

Using niobium crucibles for melting phosphate and silicate glasses of various modifier oxide contents, and therefore varying optical basicity (Lambda), was found to result in varying dissolution rates of niobate during melting. Because of their high electronic polarizability, even small concentrations of niobates are detectable in the Raman spectra of glasses. Even <1 mol% Nb2O5 can be identified, as independently confirmed by SEM-EDX analysis. Silica-rich glasses (similar to 60% SiO2, Lambda similar to 0.6) did not show significant Nb dissolution from the crucible, while higher basicity metasilicate glasses (similar to 50% SiO2, Lambda similar to 0.65) and pyrophosphate glasses (similar to 30% P2O5, Lambda similar to 0.7) did show the typical niobate signature in the Raman spectra at 810-840 cm(-1), depending on composition. While niobium is well-dissolved throughout the pyrophosphate glass, metasilicate glasses showed a much more intense Raman signature of niobate units near the outer surface of the glass. Measurements along the cross-section of a fractured metasilicate glass showed a steady decrease of the strength of the niobate signature from the surface toward the bulk of the material. Besides correlation with optical basicity, the tendency of melts to dissolve Nb crucible was discussed in terms of the connectivity or polymerization of the network and the corresponding melt viscosity.

Electrical properties of beryllium-alumino-tellurite glasses and glass-ceramics doped with iron ions were studied using impedance spectroscopy. The conductivity was measured over a wide frequency range from 10 mHz to 1 MHz and the temperature range from 213 to 473 K. The D.C. conductivity values showed a correlation with the Fe-ion concentration and ratio of iron ions on different valence states in the samples. On the basis of Jonscher universal dielectric response the temperature dependence of conductivity parameters were determined and compared to theoretical models collected by Elliott. In glasses, the conduction process was found to be due to the overlap polaron tunneling while in glass-ceramics the quantum mechanical tunneling between semiconducting crystallites of iron oxides is proposed. The D.C. conductivity was found not to follow Arrhenius relation. The Schnakenberg model was used to analyze the conductivity behavior and the polaron hopping energy and disorder energy were estimated. Additionally, the correlation between alumina dissolution and basicity of the melts was observed.

Lithium containing glassy materials can be used as solid electrolytes or electrode materials for lithium-ion batteries due to their high energy density. Conventional melt-quenched Ca11Al14Si16O49N10 glass powder containing 24 e/o N, doped with Li-ions (1, 3, and 6 wt. %) and sintered by spark plasma sintering technique (SPS) was studied. The benefits of using SPS to produce glass-ceramics are rapid heating rates compared to conventional consolidation techniques and tuning of properties, adjusting the temperature, holding time (closed to Tg temperature), heating rate (solidification), and pressure (densification) profile during the heat treatment using SPS. Pure glass and glass-ceramic were obtained under identical SPS conditions and compared with pristine oxynitride and soda-lime-silicate (float) glasses. XRD and SEM analysis confirmed that increasing the amount of Li increases the crystallinity in the glass matrix. Nano-indentation analysis showed a decreased hardness and reduced elastic modulus values with the addition of Li-ions. The direct current conductivity increases with the addition of Li due to the high mobility of Li-ions. However, the float glass sample doped with 6 wt.% of Li exhibits even higher values of D.C. conductivity, than the analogously doped Ca11Al14Si16O49N10 glass. The magnitude of activation energy (more than 1 eV) is typical for an ion hopping mechanism and the D.C. conduction mechanism is dominated by Li+ hopping.