Silica Phase Research Articles

Several natural phytochemicals from Chinese traditional fermented food-pickled Raphanus sativus L.: Purification and characterization.

In this study, we aimed to isolate and identify the bioactive compounds from 5-year pickled radish. The pickled radish was extracted with methanol or ethyl acetate. Sephadex LH-20, normal phase and reverse phase silica gel column chromatography were used for separation and purification, combined with thin layer chromatography (TLC), high performance liquid chromatography (HPLC), electrospray mass spectrometry (ESI-MS), nuclear magnetic resonance spectroscopy (NMR) technology for structural identification. The results showed that 6 compounds were separated and purified from methanol and ethyl acetate extracts of 5-year-old pickled radish. The structures were identified as 5-hydroxymethylfurfural, β-sitosterol, β-sitosterol-3-O-glucose glycosides, α-linolenic acid, 1-monopalmitin and chaenomic acid A. Using molecular docking, it was determined that β-sitosterol and its derivative β-sitosterol-3-O-glucose glycosides have high affinity for five antioxidant enzymes, and there were multiple hydrogen bonds between them. These results indicated that pickled radishes might be used as an important source of natural chemical substances.

Hydrous SiO2 in subducted oceanic crust and H2O transport to the core-mantle boundary

Subduction of oceanic lithosphere transports surface H2O into the mantle. Recent studies show that dense SiO2 in the form of stishovite, an abundant mineral in subducted oceanic crust at depths greater than ∼270 km, has the potential to host and transport a considerable amount of H2O into the lower mantle, but the H2O storage capacity of SiO2 phases at high pressure and temperature remains uncertain. We investigate the hydration of stishovite and its higher-pressure polymorphs, β-stishovite and seifertite, with in situ X-ray diffraction experiments at high pressures and temperatures. The H2O contents in SiO2 phases are quantified based on observed increases in unit cell volume relative to the anhydrous SiO2 system. Density functional theory (DFT) computations permit calibration of water content as a function of volume change based on interstitial substitution of H2O. Regression of our experimental data indicates an H2O storage capacity in stishovite of ∼3.5 wt% in the transition zone and shallow lower mantle, decreasing to about 0.8 wt% at the base of the mantle. We find that SiO2-bearing subducted oceanic crust can accommodate all the H2O in slab lithosphere that survives sub-arc dehydration. Hydration of silica phases in subducted oceanic crust and their unparalleled capacity to host significant amounts of H2O even at high mantle temperatures provides a unique mechanism for transport and storage of water in the deepest mantle.

Nanoparticle suspensions from carbon-rich fluid make high-grade gold deposits

Economic gold deposits result from a 100- to 10,000-fold enrichment in gold relative to crustal background. In hydrothermal systems, this enrichment is achieved through the transport and accumulation of metals via deeply sourced fluids to a site of deposition. However, the generally low metal solubility of Au in aqueous solutions in orogenic systems requires additional processes in order to explain high-grade gold formation. Reports of Au nanoparticles in high-grade gold veins infer that their formation is linked to mineralisation. However, processes leading to nanoparticle nucleation and deposition remain poorly understood. Here we show that formation of metal nanoparticles (Au, AuAg, Cu, Ag2O) is one of the essential contributors to efficient and focused gold deposition. We report systematic and previously unrecognized metal nanoparticles preserved in amorphous silica and/or carbonic phases in five high-grade deposits. The association of metal, silica and carbonic phases helps to constrain the multiple reactive processes involved in Au, Cu and Ag metallogenesis and formation of high-grade gold mineralisation.

Carbothermal synthesis, characterization, and mechanical properties of spark plasma sintered β-SiAlON (z = 2) powder prepared from mechanochemically activated precursors

Based on technological capabilities, β-SiAlON ceramics are one of the most valuable compounds formed in the Si–Al–O–N system, which can be synthesized from raw materials using different methods. An affordable approach was found in this study for the elaboration of the aluminosilicate precursor necessary for the synthesis of β-Si4Al2O2N6 (z = 2) from Aluminum Chloride hexahydrate, Ammonium Chloride and Sodium Metasilicate nonahydrate used as starting materials. The results obtained by XRD and FTIR revealed that the amorphous precursor prepared by mechanochemical processing originally is crystallized as mullite and silica phases at 1200 °C/2 h. Then, with continuous heating to 1500 °C/2 h, it is progressively converted into high-quality SiAlON powders β-Si4Al2O2N6 and β-Si2Al4O4N4 with a small amount of α-Al2O3 through the reduction and nitridation of mullite and intermediate phases, produced at lower temperatures. After spark plasma sintering (SPS) at 1750 °C, the nanometric particles smaller than 50 nm which are developed and distributed well throughout the microstructure of the sintered sample can be densified to 3.19 gcm−3 (≥98% theoretical density). Evaluation of the mechanical properties reveals that the microhardness of 15.8 GPa and fracture toughness of 4.62 MPa m1/2 are accessible from β-SiAlON powder prepared from the starting materials and the procedure employed in this research.It has been found that the aluminosilicate precursor prepared by mechanochemical processing can be a valuable source for CRN synthesis of SiAlON powders.

Nano-structural and nano-constraint behavior of mortar containing silica aggregates

Abstract In this study, nano-structural and nano-constraints behavior of two silica aggregate mortars are investigated. The first silica aggregate (A) is almost pure silica and the second one (B) contains silica, calcite and dolomite phases. The relationship between the durability and nano-structural changes is evidenced using Transmission Electron Microscope, X-ray diffraction (XRD) and TGA/DTA. The nano-structural results show that the macroscopic properties of mortars greatly depend on physico-chemical properties of aggregates. Higher the water absorption, higher the consumption of the Portlandite; the consumption of Portlandite, after 28 days of curing, is more in Bm sample than in Am sample. A relationship between the Portlandite content and the water absorption is evidenced. The relationship between reactivity and nano-constraints deduced from XRD modeling is highlighted.

Evaluation of the Base Stability of Hydrophilic Interaction Chromatography Columns Packed with Silica or Ethylene-Bridged Hybrid Particles

Stability as a function of mobile phase pH is an important consideration when selecting a chromatographic column. While the pH stability of reversed-phase columns is widely studied, there are relatively few reports of the stability of hydrophilic interaction chromatography (HILIC) columns. We evaluated the stability of silica and ethylene-bridged hybrid HILIC columns when used with mobile phases containing basic buffers. The predominant mode of column degradation observed in our studies was a decrease in efficiency due to voiding, resulting from the hydrolysis of the silica particles. Associated with this were increases in tailing factors. Retention factor changes were also noted but were smaller than the efficiency losses. The dependence of the rate of efficiency decrease on the key variables of temperature, mobile phase pH and water content were studied for an unbonded silica column. The effect of the acetonitrile concentration on the pH of the mixed aqueous/acetonitrile mobile phases was also investigated. Using conditions found to cause a 50% decrease in efficiency after approximately five hours of exposure to the basic solution, we evaluated eight different commercially available HILIC columns containing silica or ethylene-bridged hybrid particles. The results show large differences between the stability of the silica and ethylene-bridged hybrid particle stationary phases, with the latter exhibiting greater stability.

High performance thin layer chromatography (HPTLC) method development and validation for determination of doxycycline hyclate in capsule and tablet formulations

Abstract According to World Health Organization (WHO) 10% of the medicines in the Low and Middle Income Countries (LMICs) are of poor quality posing a major public health threat. One way to circumvent such problem is the development and deployment of rapid, economical and efficient analytical methods. Hence this research aims to develop a High-Performance Thin Layer Chromatography (HPTLC) method for the determination of doxycycline hyclate. A rapid and simple HPTLC method with densitometry detection at 360 nm to determine doxycycline hyclate in capsules and tablet formulations was developed and validated. HPTLC was performed on glass plates coated with C18 reverse phase silica gel 60 F254 and pretreated with 0.27 M ethylenediaminetetraaceticacid (EDTA) solution. The mobile phase was dichloromethane: methanol: acetonitrile: 1% aqueous ammonia in the ratio of 10:22:53:15 (v/v). The linearity range lies between 200 and 1,000 ng/spot with correlation coefficient of 0.997. The Rf value is 0.5 ± 0.02%. Recoveries were in the range of 94.50–100.5%. Limit of detection and limit of quantitation values for doxycycline hyclate were 40 and 160 ng/spot respectively. The developed method was validated as per ICH guidelines. Thus, it was found to be accurate, precise, specific and robust. In forced degradation study, doxycycline hyclate was found to degrade in acidic and alkaline media, and through oxidative stress. The drug was found to be relatively stable to heat and photo degradation. The method was successfully applied for the routine quantitative analysis of dosage forms containing doxycycline hyclate. The developed method offered comparable results (as confirmed by F-test) with that of the HPLC pharmacopoeial (BP) analysis method.

Equilibrium Phase Relations for a SiO2-Al2O3-FeOx System at 1300 °C and 1400 °C in Air

A long-term fundamental study for the construction of the thermodynamic database of a metallurgical slag system has been proposed. In the present work, the equilibrium phase relations for the key ternary SiO2-Al2O3-FeOx system at 1300 °C and 1400 °C in air were experimentally determined by the equilibrium-quenching technique, followed by X-ray Photoelectron Spectroscopy and Scanning Electron Microscope equipped with an Energy Dispersive X-ray Spectrometer analysis. The oxidation states of Fe2O3 and Fe3O4 were confirmed at 1300 °C and 1400 °C, respectively, from both XPS detection and FactSage calculation. Within the high-SiO2 composition range, the solid phases of silica, mullite, magnetite and ferric oxide were confirmed as the equilibrium phases. Based on the equilibrium compositions, the 1300 °C and 1400 °C isotherms were projected onto a SiO2-Al2O3-FeOx quasi-ternary phase diagram; however, obvious discrepancies with about a 20 °C difference were confirmed from further comparison with the predictions given by FactSage, indicating that more efforts are needed for the updating of the current thermodynamic database relating to metallurgical slag oxide systems.

Mineralogy and geochemistry of hot spring deposits at Námafjall, Iceland: Analog for sulfate soils at Gusev crater, Mars

AbstractIceland’s Námafjall geothermal area exhibits a range of alteration environments. Geochemical and mineralogical analyses of fumaroles and hot springs interacting with Holocene basaltic lavas at Hverir, and with Pleistocene hyaloclastites atop nearby Námaskarð hill, reveal different patterns of alteration depending on water-rock ratio, degree of oxidation, and substrate composition and age. The focus of this study is on the mineral deposits at and near hot springs at Hverir and Námaskarð. Surface samples, and samples collected from shallow pits in the alteration aprons adjacent to hot springs, were analyzed by X-ray diffraction (XRD) and X-ray fluorescence (XRF) to constrain the differences in composition with both distance and depth. Fluids were analyzed in the field for their environmental parameters and sampled for cation and anion analysis. Fluid analyses revealed uniformly acidic conditions but with site-to-site variation in other parameters such as temperature, salinity, and conductivity. Solid phases identified include amorphous silica, pyrite, elemental sulfur, and kaolinite in the muds, surrounded by Fe2+-sulfate and then Fe3+-sulfate efflorescence, following a redox gradient pattern involving the oxidation of sulfur and then iron with increasing distance. Shallow pits excavated near two Námaskarð hot springs reveal a shallow oxidation front, with sulfide-rich materials below a thin surface of sulfates and elemental sulfur. Silica phases include amorphous silica and quartz. Quartz likely reflects diagenetic maturation of earlier-formed amorphous silica, under surface hydrothermal conditions.The high iron content of the substrate basalt and the prevalence of Fe-sulfates and Fe-oxides among the alteration products make this geothermal area an especially useful analog for potential martian hydrothermal environments. In particular, these sulfate-rich deposits adjacent to volcanic, acidic hot springs could provide a helpful comparison for sulfur-rich soils in the Columbia Hills on Mars, where some of the same minerals have been identified (e.g., ferricopiapite) or inferred (e.g., rhomboclase).

Anti-urease and antioxidant activities of the leaf extracts from Murraya paniculata (L.) Jack (Rutaceae)

This report is on the urease inhibitory and free radical scavenging activities of the leaf extracts of Murraya paniculata. The pulverized plant sample (314 g) was extracted by successive cold maceration using n-hexane (non-polar), acetone (moderately polar) and absolute ethanol (polar) for 72 hrs. Phytochemical screening done using standard phytochemical methods, urease inhibition using modifed Berthelot method and free radical scavenging using 2, 2-diphenyl-1-picryl hydrazyl (DPPH) spectrophotometric assays. The bioactive extract was fractionated on chromatography column packed with normal phase silica gel (200-400 mesh size) and eluted using gradient mixtures of n-hexane, dichloromethane and methanol. The pooled fractions from the column were assessed for bioactivity. The functional group investigation was done using infra-red (IR) spectroscopy. Alkaloids, flavonoids, triterpenoids, phenols, steroids, and carbohydrates were present in the extract. The acetone extract displayed the highest free radical scavenging activity (54.186±0.0004) with IC 50 value: 0.84 mg/ml, and urease inhibition. Its dichloromethane-methanol column chromatography fraction had the highest free radical scavenging activity at 0.8 mg/ml (60.65±0.062) with an IC50 value: 0.49mg/ml. The activities were quite significant compared to the standard (Ascorbic acid) at P<0.05. The bioactive dichloromethane-methanol column chromatography fraction evidenced vibration stretching bands [3440 cm-1 (O-H), 2975 cm-1 (C-H), 1745 cm-1 (C=O), 1634 cm-1 (C=C), 1290 cm-1(C-N), and 1134/1007 cm-1 (C-O)] from the IR spectroscopy thus corroborating the detected phytochemicals. These current results validate the use of the M. paniculata in managing oxidative stress and other reported traditional uses in addition to the potentials for its use in the discovery and development of eco-friendly urease inhibitors for sustainable agriculture.

A machine-learned interatomic potential for silica and its relation to empirical models

Silica (SiO2) is an abundant material with a wide range of applications. Despite much progress, the atomistic modelling of the different forms of silica has remained a challenge. Here we show that by combining density-functional theory at the SCAN functional level with machine-learning-based interatomic potential fitting, a range of condensed phases of silica can be accurately described. We present a Gaussian approximation potential model that achieves high accuracy for the thermodynamic properties of the crystalline phases, and we compare its performance (and performance–cost trade-off) with that of multiple empirically fitted interatomic potentials for silica. We also include amorphous phases, assessing the ability of the potentials to describe structures of melt-quenched glassy silica, their energetic stability, and the high-pressure structural transition to a mainly sixfold-coordinated phase. We suggest that rather than standing on their own, machine-learned potentials for silica may be used in conjunction with suitable empirical models, each having a distinct role and complementing the other, by combining the advantages of the long simulation times afforded by empirical potentials and the near-quantum-mechanical accuracy of machine-learned potentials. This way, our work is expected to advance atomistic simulations of this key material and to benefit further computational studies in the field.

Guilty by dissociation: Part B: evaluation of Supercritical Fluid Chromatography (SFC-UV) for the analysis of regioisomeric diphenidine-derived Novel Psychoactive Substances (NPS)

Supercritical Fluid Chromatography (SFC-UV) employing a carbon dioxide (CO2) and 10 mM ammonium acetate in MeOH-water (95:5 v/v) gradient provides a rapid analysis (tG <10 min) of 31 novel, regioisomeric diphenidine-derived psychoactive substances, on a range of stationary phases of differing polarity. Medium to large selectivity differences between regioisomers, were observed on the acidic, neutral and basic SFC phases. For individual substituted ortho-, meta- and para-isomers, the same elution order was observed irrespective of the nature of the stationary phase. The acidic silica stationary phases yielded longer retention of the diphenidines via electrostatic attraction, whereas the basic phases resulted in shorter retention via electrostatic repulsion. SFC effected baseline separation of seven of the eight substituted groups of ortho-, meta- and para-diphenidines evaluated on a range of stationary phases. A simple silica phase achieved baseline separation of six of the regioisomeric substituted diphenidines. As the size of the halo-substituent increased, the resolution between ortho-/meta-isomers decreased, resulting in co-elution of the ortho- and meta-bromodiphenidines. Fluphenidines and chlorodiphenidines generated an elution order of meta- < ortho- < para- whereas an elution order switch was observed for the iodophenidines. This contrasted with RP-UHPLC where the elution order for the fluphenidines and iodophenidines was para- < ortho- < meta- and para- < meta- < ortho- respectively. An orthogonal elution order of diphenidines was demonstrated between the RP-UHPLC and SFC stationary phases due to the polarity differences between the separation modes. In general, hydrophilic compounds, which were poorly retained on a C18 reverse phase column, were well retained on SFC columns.

A silicon isotopic perspective on the contribution of diagenesis to the sedimentary silicon budget in the Southern Ocean

Diatoms are known to fractionate silicon isotopes during the formation of their frustules causing the silicon isotopic composition of biogenic silica to track the degree of silicic acid consumption in surface waters. Despite a growing body of work that uses this proxy to reconstruct past changes in silicic acid utilization, the understanding of the benthic silicon cycle, particularly the identification and quantification of the processes that potentially alter the silicon isotopic composition of biogenic silica during early diagenesis is still lacking. We investigated these processes by comparing the silicon isotopic composition of pore water silicic acid, biogenic silica and, for the first time, lithogenic silica from five sediment cores collected in the deep basin of the Southern Ocean representing a diversity of sedimentation regimes. Silicic acid concentrations and the isotopic composition of Southern Ocean pore waters were the result of a dynamic balance between the dissolution of biogenic silica, reactive lithogenic silica phases and Si re-precipitation with the relative importance of each processes differing significantly between regions. The results are consistent with the formation of authigenic alumino-silicates derived from dissolved biogenic silica in the Sub-Antarctic Zone and in the Antarctic Zone (on average 12 ± 5% and 17 ± 13%, respectively). Since this latter process can fractionate silicon isotopes, this implies that, even if the silicon isotopic composition of diatoms preserved in the sediments is a reliable proxy for silicic acid utilization in the past ocean, care must be taken to extract a clean biogenic silica phase free of authigenic clays and lithogenic phases from sediments to eliminate this potential bias when interpreting isotopic records.

Silica–Resorcinol–Melamine–Formaldehyde Composite Aerogels as High-Performance Thermal Insulators

Here, we report the gelation and supercritical drying of ethanol-based silica–resorcinol–melamine–formaldehyde (RMF) composite aerogels with relative concentrations of initial reagents ranging from neat silica to neat RMF alcogels. The as-prepared materials are subsequently supercritically dried with carbon dioxide. Their properties include a thermal conductivity in the 15–20 mW·m–1·K–1 range even with a silica content as low as 20%wt. The possible reasons behind this interesting insulation performance and the mechanisms leading to the underlying gel structure are discussed in depth. A focus is made on the different gelation modes happening between the RMF and silica phases, from a coating of silica surfaces with RMF species to discontinuous RMF particles within a silica backbone and a continuous RMF backbone with isolated silica particles. The implications in terms of mechanical properties and thermal conductivity are elaborated upon. The initial ratio of silica–RMF species in this ethanol-based synthesis affects the micro- and macrostructure of the composites, resulting in materials with drastically different pore structures and thus an interesting array of possibilities for a new class of silica-organic composite aerogels, based on a sol–gel process.

Evolved components in the eucrite parent body: Records in the layered eucrite Northwest Africa 8021

AbstractIn this study, we report the petrography and mineralogy of a brecciated eucrite Northwest Africa (NWA) 8021, which shows a locally layered texture with one layer containing graphic clasts and Si,Ti‐rich regions. The graphic clasts contain rod‐like grains of silica phases, augite, K‐feldspar, and Ca‐phosphate minerals included in anorthite. Some of the clasts contain relatively coarse grains of quartz, K‐feldspar, and augite, which are chemically different from the rod‐like phases, indicating different origins. All of the augite grains in the graphic clasts have rare earth element (REE) concentrations higher than those in typical eucrites. The bulk Na2O+K2O contents of the graphic clasts are higher than typical eucrites. All of these chemical features indicate that the graphic clasts were probably derived from an evolved parent rock. Low‐degree partial melting of the eucritic crust (&lt;10%) is required to generate a melt equilibrated with the REE‐rich rod‐like pyroxene from the graphic clasts. The Si,Ti‐rich regions contain high abundances of silica phases (~52 vol%) and ilmenite (~9 vol%), probably derived from an evolved Si,Ti‐rich rock (dacite). The evolved components observed in NWA 8021 are different from other evolved components observed in howardites and indicate more diverse evolution in the eucrite parent body than previously thought.

Mineralogy and bulk geochemistry of a fumarole at Hverir, Iceland: Analog for acid-sulfate leaching on Mars

AbstractIceland’s Námafjall geothermal area exhibits a range of alteration environments. Geochemical and mineralogical analyses of fumaroles and hot springs interacting with Holocene basaltic lavas at Hverir, and with Pleistocene hyaloclastites atop nearby Námaskar∂, reveal different patterns of alteration depending on the water/rock ratio, degree of oxidation, and substrate composition and age. The focus of this study is a transect of a Hverir fumarole that has formed a bullseye pattern of alteration of a Holocene basaltic lava flow. Surface samples and samples collected from shallow pits were analyzed by X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM) to constrain changes in mineral assemblage and major elemental composition with both distance and depth. Elemental sulfur is concentrated near the vent, with leached deposits with amorphous silica and anatase nearby and kaolinite, hematite, and jarosite/alunite-group sulfate minerals farther out, with smectites and less altered material at the margins, though smaller-scale mineralogical diversity complicates this pattern.Silica phases include amorphous silica (most samples), cristobalite (some samples in the leached part of the apron), and quartz (minor constituent of a few samples). The silica was concentrated through residual enrichment caused by leaching and is accompanied by a significant enrichment in TiO2 (in anatase). The presence of abundant cristobalite in a surface fumarole-altered Holocene basaltic lava flow most likely reflects cristobalite formed during the devitrification of volcanic glass or precipitation from fumarolic vapors, rather than high-temperature processes. Minor, localized quartz likely reflects diagenetic maturation of earlier-formed amorphous silica, under surface hydrothermal conditions. Natroalunite, natrojarosite, and jarosite are all present and even exhibit compositional zonation within individual crystals, showing that under surface hydrothermal conditions, these minerals can form a significant solid solution.The high iron content of the substrate basalt and the prevalence of Fe-sulfates and Fe-oxide spherules among the alteration products makes this geothermal area an especially useful analog for potential martian hydrothermal environments. The residual enrichment of silica in the leached deposits of the Hverir fumarole apron could serve as an acid-sulfate leaching model in which amorphous silica forms without appreciable sulfur-bearing phases in many samples, a possible analog for silica-rich soils in the Columbia Hills on Mars. The coexistence of hematite spherules and jarosite-group minerals serves as an intriguing analog for a volcanic/hydrothermal model for hematite and jarosite occurrences at Meridiani Planum.

Maltose-functionalized HILIC stationary phase silica gel based on self-assembled oligopeptides and its application for the separation of polar compounds.

In this study, carbonyldiimidazole was used to bond maltose-modified oligopeptides (Ala-Glu-Ala-Glu-Ala-Lys-Ala-Lys) to the surface of silica spheres for hydrophilic interaction liquid chromatography (HILIC). Attenuated total reflectance-Fourier transform infrared spectroscopy, elemental analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, BET technique, and water contact angle measurement results confirmed the successful immobilization of the obtained material. Compared with the conventional method for preparing carbohydrate stationary phases, this method involves simpler steps and less time-consuming processes. The experimental results proved that the retention mechanism of the maltose-based HILIC column matched the typical HILIC retention mechanism. The column showed high separation efficiency and stability toward the separation of polar compounds such as amino acids, bases, nucleosides, water-soluble vitamins, and salicylic acid and its analogs. The column achieved high selectivity toward oligosaccharide separation. In addition, this efficient analysis demonstrates the applicability of the as-prepared material in the field of food inspection.

Versatile Thermal-Solidifying Direct-Write Assembly towards Heat-Resistant 3D-Printed Ceramic Aerogels for Thermal Insulation.

Ceramic aerogels have great potential in the areas of thermal insulation, catalysis, filtration, environmental remediation, energy storage, etc. However, the conventional shaping and post-processing of ceramic aerogels are plagued by their brittleness due to the inefficient neck connection of oxide ceramic nanoparticles. Here a versatile thermal-solidifying direct-ink-writing has been proposed for fabricating heat-resistant ceramic aerogels. The versatility lies in the good compatibility and designability of ceramic inks, which makes it possible to print silica aerogels, alumina-silica aerogels, and titania-silica aerogels. 3D-printed ceramic aerogels show excellent high-temperature stability up to 1000 °C in air (linear shrinkage less than 5%) when compared to conventional silica aerogels. This improved heat resistance is attributed to the existence of a refractory fumed silica phase, which restrains the microstructure destruction of ceramic aerogels in high-temperature environments. Benefiting from low density (0.21 g cm-3 ), high surface area (284 m2 g-1 ), and well-distributed mesopores, 3D-printed ceramic aerogels possess a low thermal conductivity (30.87 mW m-1 K-1 ) and are considered as ideal thermal insulators. The combination of ceramic aerogels with 3D printing technology would open up new opportunities to tailor the geometry of porous materials for specific applications.

Incineration of Aviary Manure: The Case Studies of Poultry Litter and Laying Hens Manure

The industrial incineration of aviary manure is still far from the concept of using its ash residuals for nutrient uptake by plants and most of these materials are landfilled under futile fixed cost. Aviary manure includes poultry litter mixed with different aviary bedding materials or laying hens manure, which may be burned using different incineration technologies and conditions. This study aims to determine the comparative characterisation of P-rich ash residues sampled at Güres Energy (Turkey) fluidized bed combustion of laying hens manure and at Campoaves (Portugal) chain grate stoker combustion of rice husk poultry litter. The effect of different fuels and different combustion systems on P speciation in ash was investigated: the characterisation of global samples (bottom ash (BA), economiser fly ash (FAECO), cyclone fly ash (FACYC)) and respective size-fractions were done chemically (proximate and elemental analysis by X-ray fluorescence–XRF–and Inductively Coupled Plasma Mass Spectroscopy – ICP-MS), morphologically (detailed imaging and X-ray micro analysis by Scanning Electron Microscopy—Energy-Dispersive X-ray spectrometry–SEM−EDS) and mineralogically (X-ray diffraction–XRD). Phosphorus was detected in Güres ashes mainly as hydroxyapatite crystals alongside with CaCO3 relics and CaO, while Campoaves ash fractions contained P also as Na–K-Mg phosphate and major amounts of rice husk relics including unburnt char and silica phases. Both Güres and Campoaves ashes are complex but the combustion of aviary manure under these setting conditions appears to be promising for P recovery owing to their high P content and limited trace elements respecting the limitations imposed by EU legislation for fertilisers applications.

Microstructure and phase composition evolution of dual-phase ytterbium silicate coatings plasma sprayed from stoichiometric Yb2Si2O7 feedstock powder

The main challenges of atmospheric plasma spraying (APS) when dealing with rare earth silicate are the amorphous phase formation and silica volatilization in as-sprayed coatings. In this study, the microstructure and phase composition evolution of dual-phase ytterbium silicate environmental barrier coatings (EBCs) plasma sprayed from stoichiometric Yb2Si2O7 feedstock powder are investigated. The unavoidable silica volatilization leads to the coating composition deviate from stoichiometry of disilicate composition and result in the presence of Yb2SiO5 in coatings. By controlling the phase fraction of Yb2SiO5 through modulation of plasma character allows minimizing the effects of thermal residual stress on the coating durability in thermal cycling. The high crystallinity and crack-free coatings were achieved through optimized crystallization heat treatment. The presence of dislocation and deformation twins endow the dual-phase coating with intrinsic quasi plasticity and improvement in reliability. The present study provides useful inspirations on the optimization of spraying parameters and design of advanced EBC systems.