Silicate Composition Research Articles

Biomechanical assessment of zirconia-calcium silicate-silver composite dental crowns: A 3D finite element analysis study

Optimal dental health significantly contributes to an individual’s physical and psychological well-being, with an increasing focus on esthetics and functionality in dental restoration procedures. This research explores the use of zirconia ceramic materials combined with calcium silicate and silver compositions as an alternative for dental crown applications. The study employs 3D finite element analysis to assess stress distribution on full crowns with composites under axial and oblique loads, aiming to understand biomechanical aspects and identify fracture resistance and failure modes. The materials include zirconia-calcium silicate-silver composites with varying volume fractions (Zr 74 to 29%, Ca2SiO4 68 to 25%, and Ag 3 to1%). Results show stress concentration at the crown intaglio surface, influenced by the material’s elastic modulus. Specifically, the C14 composite crown with Young’s modulus 90.82 GPa exhibits lower stress levels for crown 10.9 MPa at axial load and 12.77 MPa at oblique load, making it a potentially recommended choice. These findings suggest the potential of designed biomaterials, emphasizing the importance of material selection in enhancing the longevity and resilience of dental crowns. Also, the study enhances understanding of biomechanical aspects in dental crown restorations, contributing valuable insights for clinical applications.

A case study of crushed stone for road construction application: amphibolite and basalt varieties from Croatia

Crushed stone is one of the most exploited and important mineral raw material. Emphasis is given to determination of mineralogical and petrographic properties, of two genetically different rocks of silicate composition, commonly used as crushed stone for road constructions, as their physical properties depend on them. First is amphibolite from Vetovo, and second is basalt from Vratnik locality, both sourced from Croatia. Tests conducted according to European and Croatian norms evaluated the real and apparent density, open and total porosity, and water absorption of stones. The relationship between mineralogical and physical properties led to the following conclusions: the open porosity values of amphibolite samples are low, which is a consequence of the medium to high degree of metamorphism, (plagioclase and hornblenda), sosiritization, and undisturbed rock features. The total water saturation was achieved in a brief time, confirming this statement. The basalts have different porosity and water absorption values, which are consequences of differences their textural-structural properties (glassy, intersertal or intergranular groundmass), amount of amygdules, presence or absence of chlorite/volcanic glass. Furthermore, the percentage of plagioclase in the modal composition differs, and the plagioclase itself has been altered, and the amount of clay, sericite and calcite vary in two different varieties of basalt. Compared to amphibolites, basalts have notably higher water absorption values as well. Accordingly, the studied amphibolite has water absorption less than 0.5% and is suitable for use in a road construction application for wearing course in the asphalt pavement, and studied basalt is not.

Geopolymers made using organic bases. Part III: Cast magnesium, yttrium, and zinc aluminosilicate and silicate ceramics

AbstractIt was shown in Part II of this series of articles that geopolymers synthesized with organic bases could be used as precursors to mullite and mullite + glass composites. A natural next step is to determine whether it is possible to synthesize materials outside the Al2O3·SiO2 and alkali oxide·Al2O3·SiO2 phase systems. Hence, the focus of this study was the use of geopolymer‐like processing to make preceramic bodies with magnesium, yttrium, and zinc aluminosilicate and silicate compositions. These preceramics were successfully fired into monolithic bodies of cordierite, mixed yttrium and aluminum silicates, yttrium disilicate, and willemite. The synthesis of these preceramics employed a guanidine silicate solution, a synthetic oxide powder, and in some cases metakaolin to reach the oxide composition of the ceramic. All solidified within 3 days at 20°C or 50°C, depending on the composition. For the first time, this study showed that Y2O3 and ZnO can react with silicate solutions to give some Y‐O‐Si and Zn‐O‐Si bonding analogous to Al‐O‐Si bonding in geopolymers. These results suggest that other silicate compositions may be possible, such as with the rare earth oxides, which might be valuable to process like a geopolymer rather than by traditional ceramic processing. However, the ceramics made here were generally porous due to the expansion of gases within the sample that were trapped by a viscous liquid phase during firing.

Influence of water vapor partial pressure on self-healing and oxidation of SiC-dispersed yttrium silicate composites

The self-healing and oxidation behavior of SiC-dispersed Y2Si2O7-Y2SiO5 composites were elucidated under various water vapor partial pressures PH2O. Samples were exposed in a furnace for self-healing experiments at 1100–1300°C and for high-temperature oxidation at 1200–1400°C, both for 1–24 h, under PH2O ranging from 2×104 to 5×104 Pa, while keeping PO2constant at 2×104 Pa. Water vapor promoted the self-healing effectiveness of the composites. A mechanism contributing to the closure of surface cracks was consistent with volume expansion derived from the oxidative conversion of SiC into SiO2 and the outward diffusion of yttrium cations. The formation of the internally oxidized zone signifies oxidation behavior, resulting from the inward diffusion of oxygen ions. Growth of the internally oxidized zone obeys the parabolic pattern. The influence of PH2O on the high-temperature oxidation of SiC/Y2Si2O7-Y2SiO5 is discussed in this study.

Ti- and Ba-rich phlogopitic micas in alkaline basic and upper mantle igneous rocks; stoichiometry, stability, and Fe valence estimation reassessed and rationalised

Ti- and Ba-rich tri-octahedral micas occur in fractionated basic igneous rocks, metasomatized mantle peridotites, metamorphosed pelites/carbonates, and hydrothermally altered mineral deposits. Electron microprobe analyses (EMP), with all iron reported as FeO, were widely used in the 1970/80s to interpret Ti and Ba substitution mechanisms, based on 22 O2– unit cell calculations, implying that cation vacancies occur in octahedral and/or intersheet sites. In 1996 EMP with chemical and physical analyses for ferric and total Fe, H2O, (OH), and element-specific Fe X-ray Absorption Spectroscopy (both K and L-edges) established valence states for Fe and Ti and cation site occupancies, that ∼50 % O replaces (OH) molecules, and that 24 anion cell formulae show the absence of cation vacancies. Cell formula calculation protocol for phlogopitic micas is refined here and results tested against the stoichiometric formula for vacancy-free phlogopite, XIIK2VIMg6IV[Si6Al2]O20(OH)4. Hypothetical sheet silicate compositions, calculated with fixed contents of vacancies linked to particular mixed-valence element substitutions, confirm that reliable unit cell formulae for natural mica solids require that each stoichiometric vacancy must be accounted for. If reliable estimates for ‘excess O’ (denoted WO2−) are assigned to EMP analyses, the proportion of the oxy-mica component in a mica solid solution can be defined. This approach is tested using published analyses for Ti- and Ba-rich biotites from fractionated basic and ultramafic volcanic igneous rocks (oxymica range 2.5–45 %; TiO2 up to 14 %; BaO up to 23 %), upper mantle peridotites (equivalent values 7–18 %; 6 %; 0.7 %), and metasomatised upper mantle (2–37 %; 9 %; 23 %). Enrichments of Ti and Ba in micas are clearly linked to the extra oxygen charge required to neutralise the more highly charged Ba2+ and Ti4+ replacing K+ and Mg2+.Substitution mechanisms involving Ba, Ti, and Fe3+ in ideal phlogopite involve coupled inter-site/inter-valence interactions so both site-ordering and valence-balance between the different cation sites must be accounted for. The cation exchange 2XIIK+ + 4VI(Mg2+ + Fe2+) + 4IVSi4+ ↔ XIIBa2+ + 3VITi4+ + 4(Altotal + Fe3+ + Crtotal)3+ is used here so that valence and site order can be considered together. Compositional variations show well-defined trends towards high-oxymica content and vacancy-free Ti and Ba mica end-members, rather than to oxy-free end-members with essential vacancies. Average compositions for different source rock micas are used to assess compositional trends; molecular WO2− values are refined by relating initial estimates directly to the wt.% TiO2 contents; and refined WO2− and stoichiometrically calculated Fe3+/Fetotal ratios ranging ∼0.1–0.5) are correlated with possible primary magmatic values.

Binding properties of synthesized CS glasses activated by alkaline components

The paper presents the synthesis and evaluation of hydration and binding properties of individual minerals with glass-like structures in silicate systems, most often found in technogenic materials based on phosphorus and blast furnace slags. This work aims to determine the optimum composition of CS glasses to obtain binders with given properties, the hydration of glasses of different silicate and aluminosilicate compositions in the presence of solutions of soda, sodium hydroxide, and sodium metasilicate was investigated. The results of X-ray phase and differential-thermal analysis, and infrared spectrum are given, and the hydration structure of the calcium oxide-silicon oxide-alkali component system has been studied. The analysis of hydrate neoplasms of the studied binding systems shows that the most optimal conditions for the synthesis of stone strength with stable physical and mechanical properties are created in the presence of gel-like phase reinforced by hydrosilicates and hydroaluminosilicates of alkaline and alkaline-alkaline-earth composition, characterized by fiber-like structure and possessing the ability to epitaxial fusion with each other, as well as gel-like phase, which they reinforce.

Peroxidase-Mimetic Iron Silicate Nanosheets Coordinated with Indocyanine Green for Enhanced Anti-Tumor Therapy.

The versatile element composition and multifunctional properties of biodegradable silicates have attracted significant attention in cancer therapeutics. However, their application as nanozymes is often limited by suboptimal catalytic efficiency and insufficient intratumoral retention. In this study, the hydrothermal synthesis of iron silicate (FeSi) nanosheets are reported exhibiting exceptional peroxidase (POD)-like activity (136.7Umg-1), outperforming most reported iron-based nanozymes. Density functional theory calculations revealed that the introduction of Si into the catalyst enhances H2O2 adsorption and dissociation of Fe sites, leading to superior POD performance. Furthermore, the FeSi nanosheets are modified with Indocyanine Green (ICG) to facilitate targeted aggregation-potentiated therapy. The integration of ICG improved tumor penetration and retention of the FeSi nanosheets, significantly increasing their reactive oxygen species production and bolstering therapeutic efficacy.

Understanding the multi-wavelength thermal dust polarisation from the Orion molecular cloud in light of the radiative torque paradigm

Dust grains play a key role in various astrophysical processes and serve as indicators of interstellar medium structures, density, and mass. Understanding their physical properties and chemical composition is a crucial goal in astrophysics. Dust polarisation is a valuable tool for studying these properties. The radiative torque (RAT) paradigm, which includes radiative torque alignment (RAT-A) and radiative torque disruption (RAT-D), is essential to interpreting the dust polarisation data and constraining the fundamental properties of dust grains. However, it has been used primarily to interpret observations at a single wavelength. In this study, we analyse the thermal dust polarisation spectrum obtained from observations with SOFIA/HAWC+ and JCMT/POL-2 in the Orion molecular cloud 1 (OMC-1) region and compare the observational data with our numerical results using the RAT paradigm. In general, we show that the dense gas exhibits a positive spectral slope, whereas the warm regions show a negative one. We demonstrate that a one-layer dust (one-phase) model can only reproduce the observed spectra at certain locations and cannot match those with prominent V-shaped spectra (for which the degree of polarisation initially decreases with wavelength from 54 to ~300µm and then increases at longer wavelengths). To address this, we improved our model by incorporating two dust components (warm and cold) along the line of sight, resulting in a two-phase model. This improved model successfully reproduces the V-shaped spectra. The best model corresponds to a mixture composition of silicate and carbonaceous grains in the cold medium. Finally, by assuming the plausible model of grain alignment, we were able to infer the inclination angle of the magnetic fields in OMC-1. This approach is an important step towards a better understanding the physics of grain alignment and constraining 3D magnetic fields using dust polarisation spectra.

Synthesis and Characterization of Coenzyme Q10 onto Nanoporous Calcium Silicate-Based Systems for Wound Healing

This study explores the microstructure, spectroscopic, and bonding arrangements within bioactive calcium silicate and calcium magnesium silicate systems loaded with different values (1–2.5 wt%) Coenzyme (CoQ10) ratios, synthesized using sol-gel processes. The investigation utilizes X-ray diffraction (XRD), transmission electron microscopy, and Fourier transform infrared (FTIR) spectroscopy to analyze the samples. The study explores the assignment of FTIR bonds, examining changes in the silicate-based bonds environment under the effect of the CoQ10 ratio. The observed frequency shifts and intensity variations in FTIR bonds, linked with the bioactive silicate composition, are attributed to a reduction in local symmetry resulting from introducing the calcium and magnesium oxides and CoQ10 to the silica network. The XRD and FTIR results contribute valuable insights into the structural role of silicate-based materials loaded with CoQ10, thereby enhancing our understanding of the CoQ10 release process. Approval of the CoQ10 drug loading in both calcium silicate and calcium magnesium silicate nanosystems was recognized by shifts in FTIR bands, changes in particle distribution, and the valuation of drug release activity showed by the bioactive two calcium silicate-based nanoparticles. Additionally, wound healing studies revealed the biocompatibility and wound healing response of calcium magnesium silicate nanoparticles.

Tarda and Tagish Lake: Samples from the same outer Solar System asteroid and implications for D- and P-type asteroids

We report a comprehensive study of the ungrouped type 2 carbonaceous chondrite, Tarda, which fell in Morocco in 2020. This meteorite exhibits substantial similarities to Tagish Lake, Wisconsin Range 91600, and Meteorite Hills 00432, which are generally considered to have originated from a D-type asteroid(s). We constrain the compositions and petrologies of the materials present in a potential sample of a D-type asteroid by reporting the petrography, bulk chemical compositions, bulk H, C, N, Cr, and Ti isotopic compositions, reflectance spectra, and in situ chemical compositions of metals, sulfides, carbonates, and FeO-poor and FeO-rich chondrule silicates of Tarda. We also present new data for Tagish Lake. We then compare Tarda with the other Tagish Lake-like meteorites.Tarda and Tagish Lake appear to be from the same parent body, as demonstrated by their similar petrologies (modal abundances, chondrule sizes), mineral compositions, bulk chemical and isotopic compositions, and reflectance spectra. While the two other Tagish Lake-like meteorites, Wisconsin Range 91600 and Meteorite Hills 00432, show some affinities to Tagish Lake and Tarda, they also share similar characteristics to the Mighei-like carbonaceous (CM) chondrites, warranting further study. Similarities in reflectance spectra suggest that P-type asteroids 65 Cybele and 76 Freia are potential parent bodies of Tarda and the Tagish Lake-like meteorites, or at least have similar surface materials. Since upcoming spacecraft missions will spectrally survey D-type, P-type, and C-type Trojan asteroids (NASA's Lucy) and spectrally study and return samples from Mars' moon Phobos (JAXA's Martian Moons eXploration mission), which is spectrally similar to D-type asteroids, these meteorites are of substantial scientific interest. Furthermore, since Tarda closely spectrally matches P-type asteroids (but compositionally matches the D-type asteroid like Tagish Lake meteorite), P-type and D-type asteroids may represent fragments of the same or similar parent bodies.

The Underwater Esmeralda Volcano (Mariana Island Arch) and some Features of the Composition of its Composition Rocks

A generalization of the available original data and literature data on the geological and geophysical knowledge of the underwater volcano Esmeralda, located in the Mariana Island Arc, has been carried out. As a result of studying the rocks dredged during the 4th and 5th cruises of the R/V Vulkanolog at the present level, new data were obtained on the silicate and rare-element composition of the rock samples that make up this underwater volcano. It has been established that the studied volcanic edifice is composed of five types of rocks: basalts, basaltic andesites, dacites, gabbro, and basanites. For the first time, samples of dacite and basanite have been discovered, indicating that the petrochemical diversity of the underwater volcano Esmeralda is wider than previously thought. All dredged rocks are characterized by a slightly increased content of incoherent elements LILE and HFSE. The studies carried out made it possible to attribute the main part of the dredged rocks to the association of island-arc ferruginous tholeiites (IAB, IAT) and only the composition of a single sample of alkaline basalt (basanite) falls into the field of alkaline basalts of oceanic islands (OIB, OIA). The increased content of iron in plagioclase phenocrysts confirms that the rocks belong to the high-iron tholeiite association.

Graphitization of Neoproterozoic sedimentary marbles in The Aird, Scottish Highlands

Graphite occurs in Neoproterozoic (probable Loch Ness Supergroup) marbles of The Aird, in the Northern Highland Terrane, Scotland. The graphite occurs particularly in association with phlogopite mica, and also with other micas and Mg-chlorite. Although the graphite–phlogopite association is recorded widely elsewhere in mantle-derived rocks, our data suggest graphite at The Aird does not have a mantle origin. The carbon isotopic composition of the graphite ( δ 13 C: −1.6 to 0.4‰) indicates that graphitization occurred from a CO 2 -rich fluid associated with decarbonation or devolatilization reactions of a carbonate–silicate protolith. Graphite–phlogopite-bearing marbles in The Aird underwent extensive brecciation and hematite deposition that preceded carbon-rich, mantle-derived (carbonatite) fluids. Pyrite in veins within The Aird marble has a sulfur isotope composition depleted in 34 S (−16.6 to −15.5‰), suggesting a biogenic origin. Elsewhere in The Aird and in surrounding fenitized rocks, 34 S-enriched pyrite has sulfur isotope compositions between 6.1 and 7.7‰, outside the sulfur isotopic composition range of most carbonatite-hosted pyrite, suggesting that pyrite veining is likely to have been influenced by crustal fluid–rock interactions. The observations show that if the protolith has a carbonate–silicate composition, a graphite–phlogopite association can form without the need for mantle-derived fluids.

Petrographic and chemical characterization and carbon and nitrogen isotopic compositions of cometary IDPs and their GEMS amorphous silicates

GEMS (glass with embedded metal and sulfides) are the dominant carrier of amorphous silicates in anhydrous interplanetary dust particles (IDPs) and one of the most suitable materials to study early solar system processes. Amorphous silicates in 105 GEMS from eight IDPs were analyzed regarding texture and chemical composition to reassess GEMS formation theories and genetic relationships to amorphous silicate material in meteorites. Petrography of bulk IDPs was investigated to understand GEMS’ relationships to other IDP components. Furthermore, carbon and nitrogen isotopic compositions were measured. Nearly all GEMS are aggregates of several subgrains with variable amount of nanophase inclusions and different Mg- and Si-contents, while single GEMS are rare. The subgrains within aggregates are typically surrounded by one or more carbon rims with high density. The chemical compositions of GEMS amorphous silicates are subsolar for all major element/Si ratios but exhibit wide heterogeneity. This is not influenced by silicon oil from the capturing process of IDPs as assumed before, as a penetration of the silicon oil is excluded by high resolution EELS (electron energy loss spectroscopy) areal density maps of silicon. Furthermore, low Fe-content in GEMS amorphous silicates shows that these are not altered by aqueous activity on the parent body as it is the case for amorphous silicate material in primitive meteorites. The subsolar element/Si ratios and the wide chemical heterogeneity point to a non-equilibrium fractional condensation origin either in the early solar nebula or in a circumstellar environment and are not in agreement with homogenization via sputtering in the ISM. The close association with carbon around GEMS subgrains and as double-rims around GEMS aggregates argue for a multi-step aggregation after formation of the smallest GEMS subgrains in the ISM or the early solar nebula. Carbon acting as matrix material connecting GEMS and other IDP components has lower areal density as seen from carbon EELS areal density maps and isotopic anomalies varying at the nanometer scale, pointing to different origins and processing of materials to varying extent or at changing temperatures.To balance GEMS’ subsolar element/Si ratios, a supersolar component in IDPs was assumed to account for the overall chondritic composition of bulk IDPs. Nevertheless, our bulk IDP analyses revealed subsolar, but variable, element/Si ratios for complete particles as well, depending on type and amount of mineral phases in each particle. Pyroxenes in the investigated particles can occur as elongated euhedral crystals, but are overall rare. The dominant crystalline fraction in the investigated IDP samples are equilibrated aggregates (EAs) that show the same chemical compositions as GEMS, indicating that the EAs are recrystallized GEMS grains and formed after GEMS formation as secondary phases.

Antibacterial coatings on magnesium formed via plasma electrolytic oxidation in CuO suspension

Biodegradable materials, especially Magnesium (Mg) and its alloys, are preferred for bone implants due to their compatibility with host tissue and biomechanical support. However, their rapid corrosion and vulnerability to structural failure, compounded by infections from antibiotic-resistant bacteria, pose significant challenges. Addressing these issues, we developed silicate-based composite coatings with varying CuO concentrations (1, 5, and 7 wt%) on Mg using plasma electrolytic oxidation (PEO). This study evaluated the coatings' surface characteristics, degradation behavior, and optimum composition. Our analyses, including XPS and EDX, confirmed the presence and influence of CuO on the coatings. We observed enhanced hydroxyapatite crystallization in CuO-doped coatings, which is critical for implant biocompatibility. These coatings also showed improved corrosion resistance and controlled ion release, likely due to silicate composition and CuO's sealing effects. Antimicrobial assays revealed that CuO concentration influenced bacterial and fungal adhesion, varying with microorganism type. Our findings demonstrate that incorporating inert copper particles into PEO coatings alters their chemical and elemental properties, enhancing bioactivity, corrosion resistance, and antimicrobial efficacy. These multifaceted improvements position our CuO-doped silicate coatings as a pioneering solution in bone implant technology, potentially setting new standards for safety, efficacy, and longevity in orthopedic and dental implants.

Nanocomposites Derived from Construction and Demolition Waste for Cement: X-ray Diffraction, Spectroscopic and Mechanical Investigations

In the production of cement, raw materials can be partially substituted by regenerable waste provided from glasses, construction and demolition waste in order to reduce the environmental problem and burden of landfills. In this study, limestone–silicate composites were synthesized using starting materials such as glass waste and lime, brick, autoclaved aerated concrete (ACC), mortar or plaster waste. The structure and mechanical properties of the nano-composite materials have been studied. The mean CaCO3 crystallite sizes are higher for composites containing ACC and brick than for doping with lime, mortar and plaster. Cement-based materials are formed by replacing 2.5% of the Portland cement with limestone–silicate composites. The results indicate new possibilities for introducing 2.5%of composites in cement paste because they promote the formation of the C-S-H network, which provides strength and long stability for the cement paste. The influence of varied types of mix composites in the expired cement on the initial cracking strain and stress, tensile strength and compressive strength were investigated. The compressive strength values of composite-expired cement specimens are situated between 11.8 and 15.7 MPa, respectively, which reflect an increase from 22.9 up to 63.54% over the compressive strength of expired cement matrix.

Influence of porosity on the Umov effect in silicate and organic refractory aggregates

This study investigates the influence of porosity on the Umov effect, a phenomenon observed in the scattering of light from celestial objects. The Umov effect describes an inverse relationship between the degree of linear polarization and the object’s reflectance (geometric albedo). To study the dependence of porosity on the Umov effect, a wide range of porosity (i.e., from 0.64 to 0.99) is considered. Four types of aggregates, ballistic cluster–cluster aggregate (BCCA), ballistic particle cluster aggregate (BPCA) or ballistic agglomeration (BA), ballistic agglomeration with one migration (BAM1), and ballistic agglomeration with two migrations (BAM2) each having porosity 0.99, 0.87, 0.74, and 0.64 are considered in this study. The multi-sphere T-matrix code is utilized to calculate the linear polarization and geometric albedo (A) considering silicate and organic refractory compositions for monodisperse aggregates. The results are reported for six different wavelengths, ranging from near-ultraviolet to the visible spectrum. When the polarization maximum (Pmax) is plotted against the geometric albedo (A) on a logarithmic scale, an inverse relation is observed. This relation exhibits non-linear changes, fitted by a second-degree polynomial equation, as the porosity changes from 0.64 to 0.99. This finding constitutes one of the interesting results of our study. In addition, the study explores the effect of porosity (P) on the ratio between log(Pmax) and log(A), showing a non-linear relationship. A comparison is drawn between the results obtained from organic refractory compositions and amorphous silicate compositions, emphasizing the importance of porosity and wavelength in regulating the Umov effect. In addition, the research investigates how mixing affects the results at different wavelengths, assuming the aggregates are blends of organic refractory and amorphous silicate compositions. The computations have also been performed for polydisperse aggregates (considering BCCA, BA, BAM1, and BAM2 structures) at a wavelength of 0.45 μm for silicate compositions, which also showed a non-linear dependence as observed in the case of monodisperse aggregates.

Comparative Mid-infrared Spectroscopy of Dark, Primitive Asteroids: Does Shared Taxonomic Class Indicate Shared Silicate Composition?

Primitive asteroids with low albedos and red slopes in the visible and near-infrared (VNIR) are found in both the main belt and the Jupiter Trojan clouds. In order to determine whether the VNIR spectral similarities of primitive main-belt asteroids and Jupiter Trojans are reflective of a true compositional similarity, we compare the mid-infrared silicate emission features of main-belt and Jupiter Trojan asteroids. Using archival data from the Spitzer Space Telescope’s Infrared Spectrograph and observations from the Stratospheric Observatory for Infrared Astronomy’s FORCAST instrument, we analyze the 5–40 μm spectra of 13 primitive main-belt asteroids and compare them to those of Jupiter Trojans in the literature. We find that while many primitive asteroids in the main belt resemble their Trojan counterparts with strong spectral signatures of olivine-rich high-porosity silicate regoliths, we identify (368) Haidea as a spectrally distinctive asteroid that lacks strong evidence of olivine in its mid-IR spectrum. Differences in silicate compositions among D-type asteroids imply a diversity of origins for primitive asteroids.

Upcycling of pine and sodium silicate composites through pyrolysis: Effects of pyrolysis temperature and sodium silicate content

In 3D-printing, sodium silicate (SS) can be used as an inorganic binder for wood-based composites due to its better rheological properties, high strength, and affordability. Investigating the recyclability of 3D-printed composites is necessary to understand the reusability of demolished additively manufactured construction waste. In this work, the bio-oil through pyrolysis was produced using pine and SS composites and further characterized to observe the effects of the pyrolysis temperatures and the proportion of SS in composites. Pine and SS composites with 0, 33.33, 50, and 66.67 % of the SS on a mass basis were prepared and cured to mimic the 3D-printed composites. Then, pyrolysis of cured composites was performed in a bench-scale fixed bed pyrolysis reactor at four temperatures (450–600 °C). From the pyrolysis of composites with 66 % SS at 600 ℃, a maximum condensed liquid yield of 68 % (wt.%, dry basis) was obtained. Further, it was observed that the selectivity towards hydrocarbons and alkyl phenols increased by increasing the proportion of SS in the composite, but methoxy phenols decreased, which enhanced bio-fuel production. A maximum hydroxyl concentration of 6.54 mmol g−1 was observed for the bio-oil from pyrolysis of SS-based composite at 600 ℃. This study shows the feasibility of upcycling the 3D-printed wood composites through pyrolysis to generate bio-oil that can be used for bio-based resin synthesis and bio-fuel applications.

Exploring the general chemistry of the core and ocean of Enceladus

Measurements made by the Cassini spacecraft instruments were able to reveal the composition of the geysers of the Saturn moon, Enceladus, among which salts (sodium chloride, sodium bicarbonate and/ or sodium carbonate) and traces of silica could be the result of hydrothermal processes from the interaction of an inner liquid ocean with the core of Enceladus.The chemistry of the ocean should be closely connected to the chemistry of the core. Even though. the actual composition of the core is unknown, Enceladus has been characterised as a moon with a silicate core and different authors have estimated the properties of the ocean.A core with a silicate composition alone, does not necessarily justify most of the observed species of the plume. Given the many uncertainties, in the current work, we study the possible chemistry of the core and the ocean in the context of a four-layered Enceladus (dry core, hydrated core, ocean and crust) with three different compositional scenarios for the core: primordial (represented by an ordinary chondrite), composite (represented by a carbonaceous chondrite with an igneous inclusion) and non primordial (epresented by a given peridotite). The scenarios comprise a set of minerals that interact with a primordial ocean (either pure or enriched water) at a given temperature and pressure, producing a series of secondary minerals and compounds, some of them, coincident with the chemical species observed in the geysers. Specifically, we make a chemical speciation for each proposed compositional scenario with the software PhreeqC, however our analysis is limited to the study of interactions that reach a given equilibrium. In particular, output values like the potential of hydrogen of the ocean or the saturation indices of mineral products may give us hints about the chemistry of the ocean and the core. We find that, based on the species observed in the plume, the actual composition of the core (and the ocean as well) poses a somewhat wide range of possible compositional scenarios and each of our proposed scenarios and their products justify, to some extent, the observations of the plume.

Bamboo leaf-derived biochar/iron silicate composite for an adsorption-degradation synergistic removal of ciprofloxacin

Antibiotics pose significant risks to both the environment and human health. Herein, we develop a collaborative strategy for the enhanced removal of a typical antibiotic, Ciprofloxacin (CIP), by using a bamboo leaf-derived biochar/iron silicate composite (BL-FeSi) with the assistance of peroxymonosulfate (PMS). The rationale behind the design is the construction of composited material with synergistic adsorption-catalysis functions, based on covalent bonding networks of the biochar and specific Fe(III)/Fe(II) redox chemistry of iron silicate in PMS activation system. H2 reduction of pristine BL-FeSi increases Fe(II) content and thus improves catalytic activity. Batch experiments demonstrate that the preferred BL-FeSi400 (H2 treatment at 400 °C) exhibits superior efficiency in activating PMS. The CIP removal efficiency is highly dependent on pH value of reaction solution. A remarkable 97% removal is achieved at pH = 5.5 (CIP: 60 mL, 20 mg/L; BL-FeSi400: 0.2 g/L, PMS: 0.2 g/L), and the pH increase to 11 results in 100% CIP removal. The BL-FeSi400 shows robust resistance to inorganic ions (NO3−, SO42−, HCO3−, and H2PO4−), and the catalytic activity remains consistently high (>82%) even after four consecutive cycles, making it highly promising for practical applications. It is found that both radical pathway (•OH and SO4•−) and non-radical pathway (1O2) contribute to CIP degradation in the BL-FeSi400/PMS system, while the active •OH dominates the oxidization process. The coupling of adsorption and degradation holds great potentials for effective removal of more organic contaminants.