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The inherent brittleness of ceramics poses significant challenges in the fabrication of hollow ceramic fibers, severely constraining their practical applications. In this study, a novel method for creating three-dimensional hollow fiber ceramic structures using UV-assisted single-channel direct ink writing was demonstrated. A concentric single-channel nozzle featuring shell/core structure was devised through the coaxial embedding method, and this specially designed nozzle was manufactured using digital light processing technology. During the UV-assisted direct ink writing process, the photosensitive ceramic slurry can be rapidly cured in place under the irradiation of UV light, ensuring high fidelity of the printed components. The hollow fiber structure produced in this study has a circular, pentagram, triangular and quadrilateral inner core, which can be adjusted according to the designed nozzle structure. This approach facilitates a straightforward and expedited creation of scaffolds featuring small-diameter hollow fiber structures, broadening the scope of potential applications for direct ink writing. [Display omitted] [ABSTRACT FROM AUTHOR]

Magnesium borate whiskers were used to prepare a hierarchical microstructure on cordierite ceramic substrate through the precipitation-molten salt method. The La 2-X Ce X Zr 2 O 7 catalyst was then loaded onto the magnesium borate whiskers to form the hierarchical microstructure. The Ce-doped catalysts exhibited a significant improvement in the catalytic activity of soot combustion compared to the La 2 Zr 2 O 7 catalyst. The study employed various techniques to characterize the structural morphology and phase composition, including scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform-infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The growth of Magnesium borate whiskers (Mg 2 B 2 O 5) with diameters of 100–200 nm and lengths of 2–5 μm were grown and tightly bonded to the cordierite ceramic substrate to mimic the structure of human respiratory system cilia. This could improve the filtration efficiency of soot in car exhaust. BET analysis showed that the specific surface area of cordierite increased from 0.684 m2/g to 1.363 m2/g after whisker growth. The study confirmed that the whiskers were firmly attached to the cordierite ceramic substrate, as demonstrated by the binding strength experiments. The addition of Ce metal has been found to significantly enhance soot combustion due to the presence of more active oxygen species and superior mobility of lattice oxygen species with more oxygen vacancies. The catalyst's intrinsic redox property was characterized using X-ray photoelectron spectroscopy (XPS) and H 2 temperature-programmed reduction (H 2 -TPR). The semi-quantitative thermogravimetric analysis (TG-DTG) and the temperature-programmed oxidation (TPO) of catalysts showed that Z-La 1.9 Ce 0 · 1 Zr 2 O 7 exhibited the highest catalytic activity for soot combustion, with an ignition temperature of 268 °C, a peak temperature of 418 °C, and a temperature of 90 % soot conversion of 464 °C. Furthermore, cyclic stability experiments demonstrate that the Z-La 1.9 Ce 0 · 1 Zr 2 O 7 catalyst exhibits excellent structural stability and consistent catalytic performance. This distinctive microstructure holds great potential for applications in the field of DPF. [ABSTRACT FROM AUTHOR]

This paper reports the metamorphic texture of cordierite megacrysts and the metamorphic P–T path of a newly exposed section of gneiss in East Antarctica. We used mineral textures and pseudosection modeling to reconstruct the metamorphic P–T path of cordierite- and spinel–garnet-bearing gneisses from Botnnuten, an isolated nunatak located ~ 60 km from the southern edge of Lützow-Holm Bay in East Antarctica. The gneisses underwent low-P granulite-facies metamorphism at 5.0–6.1 kbar and 850 ± 20 °C followed by isobaric cooling. The isobaric cooling path implies long residence in the middle to shallow crustal level without rapid exhumation. This contrasts with the widely recognized clockwise P–T path of basement rocks of the Lützow-Holm Complex. The rocks at Botnnuten have long been considered part of the Lützow-Holm Complex based on their petrographical features and geothermobarometric data. However, the present results, combined with a reevaluation of available data, indicate the metamorphic history of the Botnnuten gneisses is more comparable to that of the Yamato Mountains, located southwest of the study area. [ABSTRACT FROM AUTHOR]

In the Altai Accretionary Wedge, several periods of Barrovian‐ and Buchan‐type metamorphic cycles were dated from Ordovician to Permian. However, the timing and link between these cycles are not clear, and their causes are debated. In order to contribute to the understanding of Barrovian‐ to Buchan‐type evolution of the accretionary wedges, we studied an area composed of three parallel belts in the easternmost extremity of the Hovd domain located in Mongolian Altai Zone: garnet gneiss in the north, garnet–staurolite–kyanite schist overprinted by ±sillimanite±cordierite±andalusite‐bearing assemblages in the centre and garnet–sillimanite gneiss in the south. Petrography, garnet zoning and thermodynamic modelling indicate that the garnet gneiss from the northern belt records burial from ~510°C and ~3–4 kbar to ~600°C and ~5 kbar, followed by heating to ~660°C and decompression to ~4.5 kbar. The garnet–staurolite–kyanite schist from the central belt records burial from ~550°C and ~3–4.5 kbar to ~640–680°C and ~7 kbar, followed by decompression to the sillimanite stability field at ~650°C and ~6 kbar. Crystallization of cordierite, andalusite, late muscovite and chlorite in some samples indicates cooling on decompression to ~540°C and ~3.5 kbar. In the southern gneiss belt, the garnet–sillimanite gneiss with almost unzoned garnet suggests re‐equilibration at ~6 kbar and ~710°C. In situ U–Pb monazite and xenotime dating carried out inclusions in porphyroblasts and matrix grains revealed Carboniferous and Permian ages. The monazite and xenotime from gneisses of the northern and southern belts record Carboniferous and Permian ages, which are interpreted as Carboniferous crystallization at c. 347 Ma associated with metamorphic peak, followed by Permian (re)crystallization at c. 300 and 283 Ma. In the central belt, rare Carboniferous xenotime grains in a garnet–staurolite–kyanite–andalusite–muscovite schist indicate a possible Carboniferous age of the prograde metamorphism. Predominant ages between c. 280 and 260 Ma recorded by monazite are interpreted as a result of complete recrystallization during an LP metamorphic overprint. The Carboniferous ages from the gneisses can be interpreted as constraining the timing of the exhumation of deep crustal rocks to shallow crustal levels. This event corresponds to the formation of crustal‐scale migmatite‐magmatite domes in the Mongolian Altai Zone. The prograde Barrovian assemblages in the central schist belt are interpreted as having formed contemporaneously during burial in a synform between the migmatite‐magmatite domes. The Permian ages reflect LP–HT metamorphism, best recorded by the Buchan‐type assemblages in the central schist belt, and are related to massive heat flux from tectonically mobile deep partially molten crust. Correlation with similar Barrovian‐ and Buchan‐type episodes from the Chinese Altai Zone indicates multiple compressional and extensional events in the upper plate accretionary wedge, probably related to retreating and advancing modes of the subduction zone. [ABSTRACT FROM AUTHOR]

The heat of mixing of some petrological relevant substitutions (i.e., Mg-Al, Si-Al, Mg-Ti, Mg-Ca, and Mg-Fe) was investigated systematically in silicates, titanates, tungstates, carbonates, oxides, hydroxides, and sulphates by density functional theory calculations (e.g., melilite, chlorite, biotite, brucite, cordierite, amphibole, talc, pseudobrookite, pyroxene, olivine, wadsleyite, ilmenite, MgWO4, ringwoodite (spinel), perovskite, pyrope-grossular, magnesite-calcite, MgO-CaO, anhydrous and different hydrated MgSO4). A specific substitution is characterised by different microscopic interaction energies in different minerals, e.g., the octahedral Mg-Al exchange on a single crystallographic site in pyroxene has a microscopic interaction energy that is more than twice compared to that in biotite. A comparative investigation of the heat of mixing using microscopic interaction energies on a single crystallographic site has the advantage that they are not influenced by cation ordering. They could be successfully correlated with the stiffnesses of the minerals, which in turn were scaled to the oxygen packing fraction, a parameter that is easily available for poorly investigated minerals. With this information, the interaction energies of a certain substitution can be transferred from minerals where they are well-known to mineral groups where they are less- or unknown. Using the cross-site terms and the microscopic interaction energies, the macroscopic interaction energies of the coupled substitution, e.g., Mg + Si = Al + Al, of biotite and pyroxene were calculated, which are, however, affected by cation ordering and different degrees of local charge balance, for which appropriate models are necessary. [ABSTRACT FROM AUTHOR]

In this paper, cordierite ceramics with high far-infrared emission properties are synthesized by a high-temperature solid-phase method using molybdenum tailings and vanadium-titanium magnetite tailings. The microstructure, physical properties and far-infrared emission mechanism of ceramics are investigated. The results show that the ceramics synthesized with 10 wt% molybdenum tailings and 30 wt% vanadium-titanium magnetite tailings have a flexural strength of 67 MPa, a bulk density of 2.531 g/cm3 and a maximum far-infrared emissivity of 0.958 when the sintering temperature is 1200 °C. The crystal phase of the ceramic are 21.4 % cordierite and 58.7 % magnesia-alumina spinel. In the sintering process, the Fe3+ in vanadium-titanium magnetite tailings doped into the cordierite to substitute the Mg2+, which has the similar ionic radius with Fe3+, to form a substitutional solute. Ionic substitution causes the lattice parameters of cordierite larger, reducing the symmetry of the lattice vibrations and leading to lattice distortion. In addition, the composition of a large amount of magnesia-aluminum spinel is attributed to the far-infrared emission properties of ceramics. [ABSTRACT FROM AUTHOR]

Glass-ceramics have extensive industrial applications owing to their superior mechanical, optical and physicochemical properties compared to either glasses or ceramics. Herein, we leverage the concept of high entropy materials to broaden the available chemical compositions for tailoring the properties of glass-ceramics. Among various compositions explored, the high entropy glass 45SiO 2 -20Al 2 O 3 -15MgO-11Li 2 O-1.5TiO 2 -1.5ZrO 2 -2P 2 O 5 -2BaO-SnO 2 -CaO was identified as particularly promising, being easily cast with no pores and cracks. Furthermore, we successfully controlled the crystallization process to produce high entropy glass-ceramics (HEGCs) that range from highly transparent to highly opaque. The concurrent crystallization of γ-spodumene and cordierite led to exceptional mechanical properties such as high Vickers microhardness (10.37 GPa), compressive strength (541 MPa), and flexural strength (305 MPa). These findings not only showcase a novel approach to customizing the chemical composition of glass-ceramics, but also suggest the potential emergence of a new class of glass-ceramics. These materials hold great promise for dental, optoelectronics and energy-related applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The high-pressure (HP) migmatitic paragneiss of the Beni Bousera metamorphic unit (BBMU) from the Beni Bousera Massif underwent granulite-facies metamorphism. They mainly consist of garnet, biotite, kyanite, sillimanite, cordierite, spinel, quartz, plagioclase, K-feldspar, rutile, ilmenite and graphite. These minerals form a sequence of metamorphic assemblages corresponding to five metamorphic events (M1, M2, M3, M4, and M5). The first three events correspond to a latest Carboniferous-earliest Permian metamorphic evolution, while the last two are retrograde and Alpine in age. The p-T conditions of these metamorphic events were estimated using pseudosection calculations in the MnNCKFMASTHO system. Following prograde stage conditions of 9.3–10.9 kbar and 630–665°C (M1 stage), the p-T evolution culminates in melting of the paragneiss which occurred mainly at HP conditions, within the kyanite stability field, at 11.8–14.2 kbar and 820–845°C (M2 pressure-peak); anatexis then continued at high to medium pressure (HMP), within the sillimanite stability field, at 9.9–11 Kbar and 840–860°C (M3 thermal-peak), accompanied by the production of very small proportions of melt. The prograde p-T segment of the inferred clockwise path is characterized by a pressurization related to a post-Variscan collisional event triggered by the closure of the Paleotethys Ocean, and is followed by the exhumation of the granulitic unit to mid-crustal depth, with slight coeval heating. The retrograde Alpine evolution is coeval with the final exhumation of the migmatitic paragneiss and underlying peridotites during back-arc extension related to the westward retreat of the Alpine subduction. It occurred under sub-solidus conditions from 9.5–10.7 kbar and 818–848°C (M4) to 4.9–5.85 kbar and 710–785°C (M5) and corresponds to a near-isothermal and strongly decompressive metamorphic evolution (ΔP ≈ 5 Kbar). [ABSTRACT FROM AUTHOR]

George Barrow's maps (1893, 1912) of the metamorphic zones named after him in the south‐eastern Scottish Highlands, show a prominent staurolite zone running from the west of Glen Clova to the North Sea coast near Stonehaven in the east. Pelitic mica schists throughout this zone commonly show principal mineral assemblages of staurolite+biotite+garnet+muscovite +quartz (St + Bt + Grt), with sodic plagioclase, ilmenite and sometimes magnetite as common accessories; these schists have bulk compositions corresponding with those of common Dalradian metasediments. However, the mineral assemblages on the low‐ and high‐grade margins of the staurolite zone show evidence of changes from west to east. Lower grade assemblages near Stonehaven include chloritoid+biotite, which has not been found further west in the classic ‘Barrovian’ sequence; whilst the higher grade assemblages near Stonehaven lack kyanite, which is widely seen further west. The Stonehaven area has been suggested to have under gone metamorphism at lower pressure (P) than the classic region of the ‘Glens’ inland to the west.This paper describes the occurrence at middle grade in the broad staurolite zone, of unusual bulk rock compositions showing high ratios of Fe2O3/(Fe2O3 + FeO) and MgO/(MgO + FeO) (abbreviated to M/FM). The high M/FM assemblages are distinct from those of the common St‐Bt‐Grt schists. The high ratios of ferric to ferrous iron are thought to result from original sedimentary protolith compositions, that led to metamorphism at relatively high conditions of oxygen fugacity (ƒo2), and resulted in the formation of haematite‐bearing assemblages, rather than ones carrying accessory ilmenite and magnetite as in the common St + Bt + Grt rocks.In the west (Glen Lethnot), the haematite‐bearing pelites show the occurrence of kyanite at a distinctly lower grade than the common (haematite‐free) pelites, and a transition from staurolite‐biotite (St + Bt) through staurolite–kyanite‐biotite (St + Ky + Bt) to kyanite‐biotite (Ky‐Bt) assemblages occurs with increasing abundance of haematite and higher bulk M/FM values. In all bulk compositions, the upgrade formation of kyanite may be associated with the movement of the St + Ky + Bt assemblage to lower M/FM bulk compositions with increasing temperature (T). The difference in the temperature of lowest‐grade kyanite formation in haematite‐rich schists, compared with that in common haematite‐free schists may approach 50°C.In the east (Stonehaven section), the haematite‐bearing assemblages are much rarer than in Glen Lethnot, but those found so far are very distinctive in showing large porphyroblasts of probable cordierite (typically altered to chlorite and sericite). Occasional assemblages of andalusite‐cordierite‐biotite (And‐Crd‐Bt) also occur in the haematite‐bearing rocks and confirm lower pressures of metamorphism near Stonehaven than those seen further west in Glens Clova, Lethnot and Esk. [ABSTRACT FROM AUTHOR]

Purpose: Vanadium-titanium magnetite tailings are bulk industrial solid wastes and can be found in the Panxi Region of Sichuan province. The utilization of vanadium-titanium magnetite tailings as soil represents a viable strategy for achieving extensive depletion, while simultaneously fostering ecological revitalization. In order to effectively reuse the stockpiled Vanadium-titanium magnetite tailings, a comprehensive analysis was conducted to assess their physicochemical attributes, microbial community composition, and mineralogical makeup. Methods: The morphologies of six heavy metals, V, Cd, Cr, Cu, Ni, and Fe, extracted from different depths of the tailings soil were extracted and analyzed using the modified European Community Bureau of Reference (BCR) sequential extraction procedure. The physicochemical indexes—such as water content, pH, available sulfur, and available potassium, of the tailings soil were analyzed. The microbial community structure was analyzed using high-throughput sequencing, and the mineral composition was analyzed using X-ray diffraction (XRD). Results and discussion: The concentrations of Ni, Cu, Cr and Cd in the vanadium-titanium magnetite tailings are all within the controllable range. The content of available phosphorus was graded as level 1 (> 40 mg/kg), the content of cation exchange capacity (CEC) was graded as level 1 (> 20 cmol (+)/kg), and the content of available sulfur was 6.91 times higher than the average value (34.3 mg/kg) of available sulfur of the 10 southern provinces of China. At the T3-D3 sample sites, the Geothermobacter genus prevailed, while Thiobacillus reigned supreme at the remaining sampling locations. The microbial populations in the tailings were primarily influenced by sulfur and iron metabolism. The X-ray diffraction (XRD) analyses showed that pyroxene, mica, cordierite, and kaolinite were the primary minerals in the tailings. Conclusion: There is a low risk of soil contamination from the utilization of vanadium and titanium magnetite tailings as an ecological reclamation substrate. Organic matter and nitrogen being the limiting indicators of soil utilization. The abundance of Actinobacteria and Bacteroidota can be appropriately intensified during soil utilization to enhance the soil nitrogen and carbon cycling performance. The chemical weathering dominated the tailings, and its maturation could be accelerated by strengthening the chemical weathering pathway of tailings. [ABSTRACT FROM AUTHOR]

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High-strength cordierite ceramics with Li 2 O were fabricated by non-pressure sintering. The results showed that the addition of Li 2 O significantly reduced the sintering temperature and expanded the sintering range. Additionally, the mechanical strength of the samples clearly increased after Li 2 O doping. In particular, the sample with 0.5 wt% Li 2 O sintered at 1250 °C showed the best properties, with a flexural strength of 178.6 MPa and a thermal expansion coefficient of 2.1 × 10−6 °C−1. Its flexural strength is much higher than samples without Li 2 O and the cordierite ceramics prepared by non-pressure sintering reported in the literature. The high density of the sample (2.52 g cm−3) is the main reason for its excellent mechanical properties. Furthermore, first-principles calculations verify that Li+ dopants insert at the vacant channel of α-cordierite crystal with six-fold coordination, which may reduce the anisotropy of the thermal expansion coefficient of α-cordierite, thus improving the strength of ceramics. [ABSTRACT FROM AUTHOR]

Post-orogenic magmatism is uncommon in the Songpan-Ganze Orogen (SGO), and could provide deep insights into geodynamic evolution and related metallogenesis. Here we present zircon U-Pb-Hf isotopes and whole-rock geochemical data, for post-orogenic granitoids newly identified in the southern SGO. The Longxigou and Yangfanggou granites yield crystallization age of ca. 165 Ma and εHf(t) values of +3.8 to −9.1. This age post-dates regional ca. 220–200 Ma orogenic magmatism and ca. 205–190 Ma peak metamorphism, and corresponds to ca. 200–150 Ma post-orogenic magmatism which is exemplified by neighbouring and coeval Wenjiaping and Wulaxi felsic plutons. They are crosscut by ca. 133 Ma granitic pegmatites, with εHf(t) values of −4.3 to −14.2. These post-orogenic granites show high SiO2 contents, as well as low Mg# values, (Zr + Nb + Ce + Y) concentrations and zircon saturation temperatures. They have continental crust-like REE patterns and trace element profiles, and exhibit negative Eu anomalies, enrichment in large ion lithophile elements and depletion in high field strength elements. Their mineral assemblages lack typical high-temperature (e.g. pyroxene and fayalite) and peraluminous (e.g. garnet and cordierite) varieties. All these features indicate an I-type granite affinity, and a dominant derivation from thickened lower crust. In comparison, these post-orogenic granites are compositionally distinct from regional late-orogenic (>200 Ma) categories, which have more positive εHf(t) values and higher Mg# values, with subduction-related signatures involving significant mantle components. Further, several high-grade stratiform Cu deposits and a tungsten deposit occur to the south of these granitic plutons, and have mineralization ages of 164–151 Ma together with biotite alteration age of ca. 134 Ma. Hence, ca. 165–133 Ma magmatic-hydrothermal system was most likely responsible for Cu-W mineralization and effective upgrading of metal deposits in the southern SGO. [ABSTRACT FROM AUTHOR]

While basaltic volcanism is dominant during rifting and continental breakup, felsic magmatism may be a significant component of some rift margins. During International Ocean Discovery Program (IODP) Expedition 396 on the continental margin of Norway, a graphite‐garnet‐cordierite bearing dacitic unit (the Mimir dacite) was recovered in two holes within early Eocene sediments on Mimir High (Site U1570), a marginal high on the Vøring Transform Margin. Here, we present a comprehensive textural, petrological, and geochemical study of the Mimir dacite in order to assess its origin and discuss the geodynamic implications. The major mineral phases (garnet, cordierite, quartz, plagioclase, alkali feldspar) are hosted in a fresh rhyolitic, vesicular, glassy matrix that is locally mingled with sediments. The major element chemistry of garnet and cordierite, the presence of zircon inclusions with inherited cores, and thermobarometric calculations all support an upper crustal metapelitic origin. While most magma‐rich margin models favor crustal anatexis in the lower crust, thermobarometric calculations performed here show that the Mimir dacite was produced at upper‐crustal depths (<5 kbar, 18 km depth) and high temperature (750–800°C) with up to 3 wt% water content. In situ U‐Pb analyses on zircon inclusions give a magmatic crystallization age of 54.6 ± 1.1 Ma, consistent with emplacement that post‐dates the Paleocene‐Eocene Thermal Maximum. Our results suggest that the opening of the Northeast Atlantic was associated with a phase of low‐pressure, high‐temperature crustal anatexis preceding the main phase of magmatism. Plain Language Summary: Fifty‐six million years ago, the continents were beginning the final phase of their journey to their modern‐day locations. This included the rifting and formation of the Northeast Atlantic Ocean, known in particular for producing considerable magmatism during continental break‐up. In summer 2021, Expedition 396 of the International Ocean Discovery Program drilled the oceanic floor off the coast of present‐day Norway to collect volcanic and sedimentary rocks deposited at this time. Their main goal was to investigate the cause of the excess magmatism and its potential implications for the global climate. While sampling sediments on the expedition, an unexpected volcanic unit, a glassy garnet‐cordierite dacite, was recovered. To determine its origin, we combined multiple methods (petrography, stratigraphy, thermodynamic calculations, petrochronology, in situ compositional analyses) and showed that the unit is a product of melting of in the continental crust at shallow depth during the rifting process and likely later emplaced in shallow water. Our results demonstrate that the rifting process in the Northeast Atlantic included a long and intense period of continental crustal thinning. This research provides evidence needed to reconstruct the evolution of the Northeast Atlantic Ocean. Key Points: A dacitic unit was recovered in early Eocene sediments on the Vøring margin during International Ocean Discovery Program Expedition 396The Mimir dacite was formed by upper crustal anatexis at 54.6 ± 1.1 Ma, shortly after the Paleocene‐Eocene Thermal MaximumThe dacite is evidence for a break‐up phase associated with significant continental lithospheric extension [ABSTRACT FROM AUTHOR]

Cordierite is a violet-blue gem mineral primarily composed of magnesium aluminum silicate. This study employed three samples of Mg-cordierite and conducted tests on their gemological characteristics, spectroscopic features, and chemical composition using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet spectrophotometry, X-ray photoelectron spectroscopy (XPS), and electron microprobe. The study also explored and analyzed the polychroism and coloration mechanisms of the samples. The results indicate that the lattice vibrations of the Mg-cordierite samples differ along the directions parallel to the a, b, and c crystallographic axes, leading to certain variations in spectral characteristics among these directions. The article provides experimental evidence for the reasons for the polychroism of cordierite in different crystal axes, which is of great significance in the quality evaluation of cordierite. [ABSTRACT FROM AUTHOR]

Current trends in the development of materials for optics and laser technology were analyzed. The prospects of creating passively Q-switched Yb-Er glass lasers with eye-safe emission wavelengths based on glass-ceramic magnesium aluminosilicate materials for compact pulsed lasers were established. The main types of transparent glass-ceramic materials were analyzed and the main criteria for the synthesis of transparent nanostructured glass-ceramic materials with a crystalline phase content of approximately 70-80 vol.% were substantiated. Compositions of magnesium aluminosilicate glasses were synthesized and the differences of compositions with different types of optical transparency were determined, taking into account their thermal prehistory. The mechanism of phase formation and the differences of ΣMgO, Al2O3, MgO/Al2O3 and ΣRO2 in their composition, which determine the character of crystallization, optical transparency and density under the conditions of heat treatment with a duration of 0.5 and 6 hours, were studied. The developed magnesium aluminosilicate glasses can be used as a basis for the creation of protective and functional high-strength nanostructured glass-ceramic materials based on spinel or cordierite with adjustable optical transparency for optics and laser technology. [ABSTRACT FROM AUTHOR]

Idle desert sand was utilized to replacing pure SiO2 in raw materials to synthesize cordierite glass-ceramics. The effects of desert sand addition on sinterability, phase transformation, microstructure, and mechanical and thermal properties of the glass-ceramics were studied. Results show that glass transition temperature and the crystallization temperatures of glass to μ-cordierite and further to α-cordierite were all monotonously decreased with an increase of the replacement from 10 wt% to 90 wt%. Densification of the glass powder compacts started from 900 °C and was improved with increasing the replacement of desert sand and sintering temperature. The highest bending strength of 133.6 MPa and hardness of 936.7 HV were occurred at 90 wt% replacement when sintered at 1000 °C and 1100 °C for 2 h respectively; the lowest thermal expansion coefficient of 1.92 × 10−6/°C was achieved by a 50 wt% replacement and sintering at 1100 °C for 2 h. Desert sand addition not only introduces main compositions of SiO2, Al2O3, and MgO but also introduces nucleation agents of Fe2O3 and TiO2 and fluxes of Na2O, K2O, and CaO. These impurities had significant effect on improvement of the crystallization, densification, and properties of products. This eliminates the need for nucleation agents and fluxes that are necessary in the case of using pure oxides and minerals as raw materials.

Cordierite-mullite composite ceramics were prepared by solid-state method using Panzhihua low-grade Ti-rich clay, talc, and alumina. Influences of cordierite/mullite ratio, sintering temperature, and the chemical composition of clay on the phase composition, microstructure, physical properties, and thermal properties were investigated in detail. The results showed that the impurity oxides inside the Ti-rich clay had a great ability of forming liquid. Above 1300 °C, the reaction between TiO 2 of the clay and Al 2 O 3 produced stable Al 2 TiO 5 , which was conducive to decreasing the coefficient of thermal expansion (CTE). At 1300–1350 °C, the secondary mullitization caused the volumetric expansion, decreasing the bending strength and increasing the CTE. The optimum ratio of cordierite to mullite ranged from 90:10 to 80:20, and the sample fired at 1400 °C exhibited the lowest water absorption and porosity (0.64 % and 1.56 %, respectively), optimal bulk density, and bending strength (2.59 g cm−3 and 87.79 MPa), as well as better CTE, thermal conductivity, and thermal storage density (2.91 × 10−6 °C−1, 4.11 W/(m⋅K) (30 °C), and 1181 kJ kg−1, respectively). Compared with the reported values of cordierite-based thermal storage ceramics prepared by using the high-grade clay or minerals, the obtained samples showed the advantages such as lower costs for raw materials, higher bending strength, higher thermal conductivity (1.63–2 times higher), low CTE, and high thermal storage density. This study demonstrated that the low-grade Ti/Fe-rich clay has excellent cost-effective potential for the preparation of thermal storage ceramics. [ABSTRACT FROM AUTHOR]

The P–T paths of the exhumation of Precambrian granulite complexes at craton boundaries usually include two stages: subisothermal decompression and a decompression–cooling stage with a more gently sloped P–T path. Our goal is to understand the possible causes of the change in the slope of the P–T exhumation path of the Central Zone (CZ) of the Limpopo granulite complex, South Africa, located between the Kaapvaal and Zimbabwe cratons. For this purpose, rocks (mainly, metapelites) were studied in various structural settings within the Central Zone, i.e., in dome structures, regional cross folds, and in local and regional shear zones. The metapelites are gneisses of similar bulk composition. The rocks contain various amounts of relics of leucosomes composed of quartz–feldspar aggregates with garnet and biotite, and melanocratic domains that are enriched in cordierite and usually mark shear microzones that envelope and/or break garnet porphyroblasts. Study of polymineralic (crystallized melt and fluid) inclusions in the garnet, its zoning with respect to the major (Mg, Fe, and Ca) and some trace (P, Cr, and Sc) elements, fluid inclusions in quartz, as well as phase equilibria modeling (PERPLE_X) showed that the rocks coexisted with granite melts and saline aqueous carbonic fluids ( = 0.74–0.58) at the peak of metamorphism at 800–850°C and 10–11 kbar. Partial melting of the rocks initiated their subisothermal exhumation to 7.5–8 kbar during diapirism of granitic magmas in the Neoarchean (2.65–2.62 Ga). This is reflected in the specific zoning of the garnet grains in terms of the grossular content. A change in the rheology of the rocks as a result of partial removal and crystallization of melt activated the shear zones during further exhumation to 6–5.5 kbar along a decompression–cooling P–T path at 95–100°/kbar, reflecting the slower uplift of the rocks in the middle crust. This process was resumed due to thermal effects and interaction of the rocks with aqueous fluids ( > 0.85) in the Paleoproterozoic (~2.01 Ga). Such a scenario of metamorphic evolution implies that the Limpopo granulite complex in general and its Central Zone in particular resulted from the evolution of an ultrahot orogen, in which vertical tectonic movements associated with diapirism were coupled to horizontal tectonic processes caused by the convergence of continental blocks. [ABSTRACT FROM AUTHOR]

Ceramic-based back covers are commercially utilized as a high-end option for the physical protection of mobile phones. Herein, an unprecedented composite structure consisting of a cordierite (2MgO.2Al 2 O 3 5SiO 2) glass–ceramic strengthened with yttria-stabilized zirconia (YSZ) fillers is introduced as a protective back cover, specifically for next-generation communication mobile phones additionally requiring a low dielectric constant at gigahertz frequencies. Crystallization sequence was rather complicated with the involvements of multiple crystalline phases, α- and μ-cordierite, tetragonal and monoclinic ZrO 2 , and ZrSiO 4 , depending on the glass and composite compositions. This unique approach effectively induced the best mechanical performance for the 10 wt% YSZ/glass–ceramic structure, despite the low sintering temperature of 1050 °C, with the highest Vickers hardness of ∼9.2 GPa and flexural strength of ∼196.8 MPa attained for the optimal composite. Although effective dielectric constant of the composites depended on the relative contents of the evolved crystalline phases, overall dielectric constant was kept low due to the utilization of cordierite glass as the main component. [ABSTRACT FROM AUTHOR]

Binary CaO‐MgO‐Al2O3‐SiO2 (CMAS) ceramics composites of anorthite‐cordierite composition were synthesized from natural raw materials (kaolin and dolomite rock). The change of SiO2/Al2O3 ratio in kaolin/dolomite mixtures (12, 24, and 36 wt.%) and synthesized composites along with analysis of their phase composition transformations (X‐ray diffraction) during heat treatment (thermogravimetric and differential thermal analysis) give the controlled design of aluminosilicate matrices. The obtained ceramic composites are represented by anorthite, a cordierite‐like phase whose ratio varies from 1.3:1 to 2.8:1. Mullite crystals, also included in the composition, reinforce the anorthite‐cordierite matrix. The morphostructural features of the samples were studied using optical and scanning electron microscopy. The porosity ranges from 7.8% to 24.2% depending on dolomite content. The impurities of iron and titanium interfering with obtaining a qualitative product are leveled by the presented technique including the heat treatment scheme justified by thermogravimetric analysis. Obtained CMAS‐ceramics of anorthite‐cordierite composition correspond to industrial international standards by their technical characteristics and exceed the requirements for heat‐insulating and chemically resistant materials by compressive strength. [ABSTRACT FROM AUTHOR]

The specific surface area of attapulgite was significantly enhanced (from 128 to 212 m2/g) by its purification with sodium hexametaphosphate and nitric acid. Subsequently, an acid modification method was employed to prepare a coated attapulgite cordierite honeycomb with a specific surface area approximately 39 times larger than that of the bare cordierite honeycomb. SEM images showed that the surface of the cordierite was rough and uneven, with the attapulgite filling the large pores on its surface, forming a "nail-like" interaction between the coating and the carrier. After loading the catalyst, no significant mass loss was observed after 1 h of ultrasonic testing, indicating good adhesion stability of the coating. Furthermore, under test conditions of GHSV (Gas Hourly Space Velocity) = 10 000 h–1 and a toluene concentration of 1500 ppm, the prepared integrated catalyst exhibited excellent activity for the catalytic oxidation of toluene, with T50 and T90 values of 261 and 290°C, respectively, suggesting broad application prospects. [ABSTRACT FROM AUTHOR]

[Objective] The Prydz Bay belt in East Antarctica recorded two significant tectono-thermal events, the Grenvillian event and the Pan-African event, which are considered to be closely related to the evolution of the Rodinia and Gondwana supercontinents. However, the geological history and the tectonic nature of the two events remain controversial. [Methods] Mineralogical and petrological analyses, phase equilibria modelling and zircon geochronology are combined to investigate the spinel-cordierite granulite from the Mirror Peninsula in order to better understand the tectono-thermal history of the Prydz Bay belt. [Results] The spinel-cordierite granulite contains different stages of mineral assemblages. The major stage of mineral assemblage involves cordierite, spinel, biotite, sillimanite, K-feldspar and minor garnet and ilmenite. The later stage of mineral assemblage is indicated by the emergence of magnetite as the increasing volumes of biotite and cordierite. Minor garnet and corundum are locally preserved, implying the mineral reaction 'g+cor→sp+sill' and more garnet and corundum in the peak stage. The garnet grains consist of 70%-72% almandine, 20%-22% pyrope, -4% grossularite and -4% spessartine. The XFe (Fe2+/(Fe2++Mg2+)) of representative garnet grains ranges from 0.77 to 0.80. The spinel exhibits an XFe range from 0.80 to 0.86. Different cordierite grains have similar compositions with Al of 3.89-3.93 a.p.f.u (atoms per formula unit) and XFe of 0.32-0.36. Biotite has high TiO2 (4.13%-5.23%) and Ti (0.23-0.30 a.p.f.u). K-feldspar grains consist of 78%-85% orthoclase, 15%-23% albite and -1% anorthite. Based on the mineral compositions and phase equilibrium modelling, the pressure-temperature (P-T) conditions of the major stage of mineral assemblage are constrained to 870-910 °C and 0.64-0.69 GPa, followed by later retrogression to 810-820°C and 0.49-0.53 GPa. A peak stage with higher P-T conditions (T>910 °C, P>0.69 GPa) can be inferred based on the relict peak minerals and characteristic mineral compositions (e.g. Ti in biotite). Zircon grains commonly show core-mantle-rim structures in cathodoluminescence (CL) images. The LA-ICP-MS zircon U-Pb dating analyses reveal a wide age range from 613±7 Ma to 877±9 Ma (except a maximum of 916±11 Ma) for the cores. The zircon bright rims yield a weighted mean age of 526±8 Ma with a wide range of Th/U (0.06-1.23), mostly higher than 0.1. [Conclusion] Based on the results, a few conclusions can be drawn: (1) The spinel-cordierite granulite recorded medium-low pressure/high-ultrahigh temperature metamorphism with a clockwise P-T evolution path and high dT/dP. (2) The results of zircon geochronological analysis show that zircon cores mainly record U-Pb ages in the range of 800--600 Ma, younger than typical ages of Grenvillian events, which may reflect younger inherited zircon cores or significant isotopic resetting. (3) The age of -530 Ma of zircon rims is interpreted to represent the post-peak cooling stage of the Pan-African tectono-thermal event. [Significance] This study examined the P-T conditions and the zircon ages of the spinel-cordierite granulite in the Mirror Peninsula. In combination with previous results, the P-T-t path constructed for the spinel-cordierite granulite provides new constraints on the evolution of the Prydz Bay belt during the Pan-African period. [ABSTRACT FROM AUTHOR]

Dip coating method was utilized for wash-coating alumina onto cordierite honeycomb substrate, followed by catalyst coating by sol–gel dip coating of CMX(X = 0, 5, 70, and 100 corresponding to Ce1-xMnxO2-δ, where x = 0, 0.5, 0.7, and 1) to obtain CM0/Al2O3/Cord, CM5/Al2O3/Cord, CM70/Al2O3/Cord, and CM100/Al2O3/Cord. The sol–gel was obtained from the EDTA–citrate method. XRD, BET, and BJH analysis was conducted on samples Cord to CM100/Al2O3/Cord. An intense peak of ceria at 462.53 cm−1 and that of Mn3O4 was observed at 658 cm−1 in the Raman spectra analysis. The adherence test was conducted to test the mechanical stability of the wash-coat and catalyst layer. The visual evidence of coating was furnished by optical imaging and FESEM analysis. Ultrafine particles with high porosity were observed in sample Al2O3/Cord. Cracks were observed in the FESEM images of CM0/Al2O3/Cord to CM100/Al2O3/Cord samples. CO oxidation studies were performed on the samples Cord to CM100/Al2O3/Cord. CM70/Al2O3/Cord performed the best among all other samples with a T50 temperature of 157 °C. The activation energy of CO oxidation was calculated using the Ozawa method for samples CM0/Al2O3/Cord to CM100/Al2O3/Cord. 50 h long-term CO oxidation stability experiments were also conducted on samples CM0/Al2O3/Cord to CM100/Al2O3/Cord. The synergistic effects of ceria and manganese, combined with fine dispersion of the catalyst, pore characteristics, and cracks improving diffusivity, pitched CM70/Al2O3/Cord to have the best CO oxidation activity. [ABSTRACT FROM AUTHOR]

In this study, aluminum titanate-cordierite composite ceramics were successfully prepared fry solid-state reaction method, with MgO as a stabilizer and cordierite as a reinforcement. The effects of MgO, cordierite, and sintering temperature on the phase composition, microstructure, sintering performance, and thermodynamic properties of the composite ceramics were systematically investigated. The experimental results show that the introduction of MgO promotes the synthesis and growth of aluminum titanate grains, reduces the sintering temperature, and improves the thermal stability of aluminum titanate ceramics by forming a solid solution of MgxAl2(1-x)Ti(1+x) O5. Cordierite plays an important role in sintering densification and mechanical properties. Under the sintering condition of 1 325 °C, the sample (MgO content of 8.00%, cordierite content of 15.00%) exhibits excellent performance, with a bulk density of 3.49 g/cm³, a porosity of only 2.2%, a flexural strength of 66.8 MPa, and a thermal expansion coefficient of 2.6 x 10-6 K-1 (room temperature to 1 000 °C). The research results provide new insights for the design and preparation of high-temperature structural ceramics with excellent comprehensive performance. [ABSTRACT FROM AUTHOR]

The main objective of this study is to fabricate composite materials having excellent thermal, mechanical and electrical properties for thermal and electronic applications. In this work, strontium feldspar-containing composites (Sr-feldspar/cordierite and Sr-feldspar/Sr-osumilite) were prepared by solid-state sintering of SrO-containing cordierite (MgSrAl 4 Si 5 O 18)/borosilicate glass powder mixtures. The phase composition, physical properties and microstructure of sintered composites were investigated by X-ray diffraction technique, water displacement method and scanning electron microscope, respectively. Moreover, the thermal expansion coefficient, hardness, and electrical properties were also measured. The results of X-ray patterns revealed the crystallization of Sr-feldspar and cordierite in the composites that contain up to 20% borosilicate glass. On the other hand, the composites that include more than 20% glass, displayed the crystallization of Sr-feldspar and Sr-osumilite with little amount of cristobalite. The bulk density values of sintered composites were decreased from 2.41 to 1.84 g/cm3 with increasing the amount of added glass. The microhardness values were increased from 519 to 710 kg/mm2 with increasing the glass content. Low thermal expansion coefficient (2.65 × 10−6, 2.22 × 10−6, 3.45 × 10−6 and 4.26 × 10−6 K-1 for C0, CG91, CG73, CG55, respectively) and low dialectic constant (7–8.5) were obtained for the prepared composites. [ABSTRACT FROM AUTHOR]

In this work, we investigate the spectroscopic properties of photochromic alexandrite and cordierite by TD‐DFT. The objective is to assess the TD‐DFT for the simulation of pleochroism (change of color depending on the crystallographic direction of the observation) and the change of color as a function of the light source. For these simulations, we compared an embedding where dangling bonds are saturated by hydrogen atoms and an electrostatic embedding. The electrostatic embedding provided numerically more stable results and allowed a good reproduction of the pleochroism of cordierite, based on a Fe2+‐Fe3+ intervalence charge transfer transition. However, the pleochroism of alexandrite is not as well reproduced, suggesting that TD‐DFT has some difficulties to reproduce the anisotropy of the transition dipole moment, an aspect that is not deeply documented in the literature. [ABSTRACT FROM AUTHOR]

The saggar plays a crucial role as a carrier during the solid‐state sintering process of Li‐ion battery cathode materials. In order to enhance its resistance against alkali erosion, the study utilized hibonite, cordierite, α‐Al2O3, and zirconia as primary raw materials, along with Ca(OH)2 as an additive, to fabricate a composite‐layered hibonite–cordierite saggar. Our investigation delves into the sintering bond formation between the composite layer and the saggar matrix and, more crucially, scrutinizes the saggar's erosion resistance against Li‐ion battery cathode materials. The outcome underscores the groundbreaking impact of a 3% Ca(OH)2 infusion on in situ anorthite formation within the composite layer, ushering in a robust integration between the composite layer and the saggar matrix. Moreover, this unique anorthite formation establishes a dense isolating shield along the periphery of hibonite particles, effectively impeding the corrosive reaction between the cathode material and the saggar, thus enhancing the saggar's resistance to corrosion. [ABSTRACT FROM AUTHOR]

• New insight on the journey of "Byzantine gems" from the East to the West of the Empire. • The gems of the relic of St. John the Baptist and its reliquary are analyzed for the first time. • The presence of a rare and exquisite example of Balas ruby was identified in the relic. • The investigation improves knowledge on ancient gems traveling across Europe. Gems, especially from remote areas, were highly demanded and valued in Byzantine times, often used for sacred Imperial purposes. Because of their imperishable nature, they were often re-used over time and many of them passed, one way or another, from East to Western Europe. The history of the gems set in Byzantine relics that survived in medieval Europe is often impossible to reconstruct. The exceptional opening of the relics of St. John the Baptist in Siena, 200 years after the last inspection, has made it possible to study the magnificent gems that adorn it. Spinels, rubies, sapphires and other gems from oriental geographies, along with high quality glasses used together regardless of their monetary value, were identified in the relic and its reliquary case through gemological analysis and portable Raman spectroscopy, once again demonstrating the vital contribution of the trans-disciplinary approach in the study of ancient art goldworkings. [ABSTRACT FROM AUTHOR]

Mabel Creek Ridge, in the northern Gawler Craton, is a granulite‐facies domain recording early Mesoproterozoic metamorphism, flanked by less metamorphosed rocks and dissected by crustal‐scale divergent structures. The nature of early Mesoproterozoic events is poorly understood due to the lack of basement outcrop. Calculated metamorphic phase diagrams and geochronology are used to decipher the tectonic regime of a potential gneiss dome. Pressure–temperature (P–T) modelling of metapelites from five drill holes across Mabel Creek Ridge suggests it has experienced conditions of ~6.4–7.4 kbar and 800–850°C and the growth of suprasolidus cordierite after garnet indicates subsequent decompression. In situ U–Pb monazite and Lu–Hf garnet geochronology constrains the granulite‐facies metamorphism of Mabel Creek Ridge to ca. 1600–1560 Ma. In contrast, drill hole GOMA DH4 located to the north of Mabel Creek Ridge records conditions of 2.2–5.4 kbar and 710–740°C at ca. 1520 Ma, with no evidence for 1600–1560 Ma metamorphism. Our new P–T pseudosection results and geochronology data from Mabel Creek Ridge and adjacent crust, coupled with the regional seismic and airborne magnetic data, reveal that Mabel Creek Ridge represents a record of early Mesoproterozoic extension in the Gawler Craton, during which thermally perturbed lower crustal rocks were exhumed within a gneiss dome. Early Mesoproterozoic extension took place within a complex geodynamic regime resulting from the interplay between final Nuna convergence along the margin of northeast Australia at ca. 1600 Ma and subduction to the southwest at ca. 1630–1610 Ma. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ceramics / Taoci Xuebao is the property of Journal of Ceramics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ceramics / Taoci Xuebao is the property of Journal of Ceramics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Refractories / Naihuo Cailiao is the property of Naihuo Cailia (Refractories) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Early Permian in the present-day Europe area was a time when a major tectonic shift occurred, leading from the tectonic collapse of the Variscan orogeny to the crustal extension and thinning that characterized the Early Permian times. Crustal extension was associated with extensive magmatism at different crustal levels: from gabbro in the lower crust or at the mantle/crust transition to subaerial high-SiO2 volcanic activity. In the whole Southalpine Domain, the Early Permian intrusive bodies occur from the west (e.g. Ivrea-Verbano Complex and "Graniti dei Laghi") to the east (Ifinger, Brixen and Cima d'Asta intrusive complexes). Among these, in the central Southern Alps (comprised between the Giudicarie Belt and the Lake Como), minor intrusive complexes also occur. The Val Biandino Intrusive Suite consists of two magmatic units: the Val Biandino Quartz-Diorite (VBQD) and the Valle di San Biagio Granite (VSBG). The first of them consists of gabbro-diorite to granodiorite bodies associated with leucocratic cordierite-bearing granitic dikes that intruded the pre-Permian basement. To the west, a W-dipping normal fault of Permian age represents the boundary between this unit and the Valle di San Biagio porphyric granite. All rock varieties of the Val Biandino Intrusive Suite display a high-K calc-alkaline affinity with metaluminous to peraluminous character. Field crosscutting relationships point to a late generation of the cordierite granites of the Val Biandino Quartz-Diorite unit with respect to the more mafic types. SHRIMP U–Pb zircon dating provided an age of 285.2 ± 1.9 Ma for a cordierite granite of the Val Biandino Quartz-Diorite unit and 283.2 ± 1.9 Ma for the porphyric Valle di San Biagio Granite. Geochemical data suggest that gabbro-diorite, quartz-diorite, granodiorite and leucogranite are not co-magmatic. The existing gaps in term of SiO2 wt% and the higher HREE contents in mafic and intermediate rocks with respect to granite coupled with similar LREE in all rocks support this hypothesis. The high Rb/Sr ratios (> 1) in leucogranite, together with the occurrence of white mica and cordierite point to a significant contribution of crustal partial melting in their genesis. The Val Biandino Intrusive Suite was likely formed through the interaction of magma genesis at the mantle/crust transition and partial melting of the heterogeneous pre-Permian basement of the Southalpine Domain. This scenario explains the strong heterogeneity displayed by the relatively small intrusive complex and the strong crustal signature exhibited by all the magmatic types of the Val Biandino Intrusive Suite. [ABSTRACT FROM AUTHOR]

In order to obtain ceramic materials for high-temperature gas-solid separation, the cordierite-mullite-corundum porous ceramics were prepared by particle stacking and pore-forming agent method, with bauxite as aggregate and in-situ synthesized cordierite as binder. Designed four-factor four-level orthogonal experiments for the first time to improve the porosity of the samples. The phase composition and microstructure of the samples were studied by XRD, SEM and other testing methods. The results show that: X6 sample (firing temperature of 1340 °C, 50 wt% binder, aggregate coarse, medium and fine mass percentage 30:50:20, plus 20 wt% charcoal powder, 10 wt% graphite) has the best comprehensive performance, with porosity of 41.51 % and bending strength of 17.88 MPa. Pore size distribution range from 10 to 40 μm. Corundum and mullite, with excellent high-temperature properties formed by the aggregate, are tightly bonded together by cordierite, contributing to the strength of the porous ceramics. The addition of pore-forming agent improves the porosity and forms a stable and uniform pore structure in the porous ceramics. The high porosity and large connected pore size reduce the viscous resistance of the porous ceramics to the gas, improve the filtration performance of the material, and make it expected to be applied in the field of hot gas clean-up. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the mineralogical composition of equine enteroliths from the Aburrá Valley in Antioquia, Colombia. Samples of eight enteroliths from eight horses were subjected to semi-quantitative X-ray diffraction (XRD) and transmission and scanning electron microscopy (TEM/SEM) analysis. The TEM/SEM of the analyzed enteroliths reported the presence of carbon, oxygen, phosphorus, magnesium, calcium, silicon, potassium, bromine, iron, sulfur, and aluminum. The XRD identified struvite, newberyte, kyanite, low quartz, actinolite, nitratine, cordierite, and vivianite. Both techniques used in the analysis of the enteroliths were correlated by matching the mineral compounds with the detected chemical elements. The main mineral components of the enteroliths were magnesium phosphates, struvite and newberyte being the most common. [ABSTRACT FROM AUTHOR]

Constructing a monolithic catalyst for low-temperature catalytic oxidation of refractory volatile organic compounds (VOCs) is of great value and significance. Herein, a series of aliovalent-doping MnCeOx/cordierite were prepared by two-step hydrothermal method. Ce(OH)3 was loaded on cordierite at first, which not only provided abundant oxygen vacancy but also acted like a coating. In the second step, Ce3+ partially redissolved at high temperatures and formed MnCe-BDC together with Mn and ligand. Impressively, the pyrolyzed catalyst has an excellent structure with aliovalent-doping and the specific surface area of cordierite is improved, resulting in the excellent catalytic oxidation performance for o-xylene with a T90 of 283 °C. At the same time, the catalyst shows great stability in cycle, water vapor, long-term, different airspeed, and variable temperature tests. This study provides a new strategy for the design of efficient and stable monolithic catalysts for the catalytic oxidation of VOCs. [ABSTRACT FROM AUTHOR]

A simple in-situ method was proposed to synthesize surface coating of SiC nanowhiskers on cordierite honeycombs by aluminothermic, silicothermic, and carbothermic reduction reactions. The surface coating of SiC nanowhiskers was synthesized by controlling the partial pressure of SiO gas on the surface of honeycombs, based on the pore-forming process using aluminium(Al) agent. Increasing the porosity of the honeycombs provided aisles to volatilize SiO gas, and the growth of SiC nanowhiskers changed from inside the honeycomb wall to on the honeycomb surface. SEM and TEM observations revealed that the relatively high porosity (≥45%) and sintering temperature (1250–1300 °C) were necessary for obtaining surface coating of SiC nanowhiskers, and the nanowhisker-coating having the smooth morphology and a thickness of ∼150 µm was obtained at 1250 °C. Compared with cordierite honeycombs without SiC nanowhiskers, SiC nanowhiskers inside the honeycomb walls could improve the compressive strength and thermal conductivity with increasing rates of 121% and 123%, respectively, and the surface coating of SiC nanowhiskers increased the specific surface area of the honeycombs by 241 times. [ABSTRACT FROM AUTHOR]

To achieve the low temperature synthesis of cordierite, according to its theoretical ratio, porous cordierite ceramics were prepared using calcined kaolin (≤0.044 mm), sintered magnesia (≤0.074 mm) and silica micropowder (d50 =2.6 µm) as main raw materials, analytically pure zirconia and lanthana as sintering aids, and polyvinyl alcohol (PVA) solution as the binder, pressing to samples of Φ30 mm x30 mm at 60 MPa, drying and calcining. The effects of the extra additions of zirconia (0 and 8%, by mass) and lanthana (0, 0.2%, 0.4%, 0.6% and 0.8%, by mass) and calcination temperatures (1 200, 1 250 and 1 300 °C) on the cold physical properties, phase composition and microstructure of the porous cordierite ceramics were studied. The results show that: (1) the sample fired at 1 300 °C and introduced with 8% zirconia and 0.6% lanthana shows good physical properties; (2) the co-doping of zirconia and lanthana can improve the mechanical properties of the sample while maintaining the apparent porosity, and promote the formation of cordierite; (3) the co-doping of zirconia and lanthana can reduce the synthesis temperature of cordierite and improve the comprehensive performance of the sample. [ABSTRACT FROM AUTHOR]

This work investigates the relationships between partial melting, melt extraction, pluton growth and silicic volcanism in garnet-bearing felsic volcanic rocks that were extruded in the Iberian Pyrite Belt, at ca. 345 Ma. The garnets are of peritectic origin, displaying textural and chemical features of disequilibrium crystallization during partial melting reactions involving biotite at high temperatures (up to 870 °C) in the middle-lower crust. Major element composition suggests compositional equilibrium with the entrained and pinitized peritectic cordierite, but reveals some subsequent homogenization by diffusion. Trace element maps and spot analyses of garnet show, nonetheless, significant trace element variations, reflecting biotite and Y-REE-P-rich accessory phase breakdown during partial melting reactions. Peritectic garnet and cordierite growth resulted in the preservation of Th- and Y-rich prograde suprasolidus monazite, which constrains the timing of partial melting of the metapelitic protolith at ca. 356.8 ± 2.4 Ma. The zircon cargo further shows that a significant amount of zircon crystals from previously crystallized felsic melts were also remobilized and erupted. These were likely stored in an upper crustal pluton that grew episodically since ca. 390 Ma during voluminous melt generation periods within the middle to lower crust, which also resulted in voluminous volcanism. The geochemical trends of the felsic volcanic rocks reflect the entrainment of xenoliths of peritectic garnet, cordierite and feldspar, and as such, the garnet-bearing felsic volcanic rocks represent an erupted mixture of a lower-temperature (ca. 770 °C) silicic melt and autocrysts, and peritectic phases and zircon crystals from previously crystallized and stored felsic melts. [ABSTRACT FROM AUTHOR]

The analysis of the influence of an increase in firing temperature on the thermodynamic possibilities of solid-phase chemical reactions in the MgO-Al2O3-SiO2 system in the direction of cordierite formation has been conducted. The thermodynamic direction of solid-phase reactions in the MgO-Al2O3-SiO2 system allows determining rational firing temperatures of materials containing cordierite for the manufacture of products for various purposes. During low-temperature firing (up to 1200 K) of finely dispersed masses based on talc-clay-alumina compositions, materials with high open porosity but low strength characteristics can be obtained. This is because the reactive sintering mainly occurs due to reactions forming intermediates for cordierite synthesis and incomplete processes of destruction in natural mineral raw materials. In the firing temperature range of 1200-1500 K, the thermodynamic probability of reactions immediately via several cordierite formation mechanisms increases, which should limit the growth of individual crystals while increasing their quantity. This should positively affect the strength and heat resistance of materials due to low values of the thermal coefficient of linear expansion. Firing temperatures of 1500-1659 K correspond to the limits for cordierite formation and contribute to the consolidation of the material with a change in the nature of porosity from open to closed. Exceeding firing temperatures above 1659 K results in the thermodynamic instability of the cordieritecorundum phase combination and can lead to the formation of defects due to the appearance of a significant amount of melt in the phase composition of the material. [ABSTRACT FROM AUTHOR]

In glass-ceramic design, the two most crucial factors are composition and microstructure both factors control the ability to form a glass and determines its degree of workability. The composition also determines whether internal or surface nucleation can be achieved. If internal nucleation is desired, as is the case in hot forming glassware, right nucleating agents are melted into the glass as part of the bulk composition. For this reason, this research work focuses on obtaining glass-ceramic cordierite starting from a parent glass of the MgO–Al2O3–SiO2–MoO3 system, using NiO, ZrO2 and TiO2 in a range of 1%Wt to 3%Wt, with the objective of identifying which of the oxides most favors the formation of cordierite. Twelve samples were prepared, which were characterized by thermal gravimetric analysis (TGA), differential thermal scanning analysis (DSC), X-ray diffraction (XRD), Elemental X-ray mapping (SEM), and Infrared spectra using the ATR technique (FT-IR). It was found that NiO is the oxide that most promotes the formation of the cordierite phases, in addition to the use of molybdenum as part of the parent glass, which lowers the crystallization temperature of the crystalline phases obtained. This is determined with the results of phase quantification using the Rietveld method, by XRD, where the samples with NiO add up to a content greater than 90 % of cordierite α and β. And it is supported by the SEM results, where the characteristic hexagonal morphologies of cordierite are identified, the IR characterization results where the bands of the bonds of the phases identified by XRD are identified.

Toluene treatment has received extensive attention, and ozone synergistic catalytic oxidation was thought to be a potential method to degrade VOCs (violate organic compounds) due to its low reaction temperature and high catalytic efficiency. A series of bimetal/Cord monolithic catalysts were prepared by impregnation with cordierite, including MnxCu5−x/Cord, MnxCo5−x/Cord and CuxCo5−x/Cord (x = 1, 2, 3, 4). Analysis of textural properties, structures and morphology characteristics on the prepared catalysts were conducted to evaluate their performance on toluene conversion. Effects of active component ratio, ozone addition and space velocity on the catalytic oxidation of toluene were investigated. Results showed that MnxCo5−x/Cord was the best among the three bimetal catalysts, and toluene conversion and mineralization rates reached 100 and 96% under the condition of Mn2Co3/Cord with 3.0 g/m3 O3 at the space velocity of 12,000 h−1. Ozone addition in the catalytic oxidation of toluene by MnxCo5−x/Cord could efficiently avoid the 40% reduction of the specific surface area of catalysts, because it could lower the optimal temperature from 300 to 100 °C. (Co/Mn)(Co/Mn)2O4 diffraction peaks in XRD spectra indicated all the four MnxCo1−x/Cord catalysts had a spinel structure, and diffraction peak intensity of spinel reached the largest at the ratio of Mn:Co = 2:3. Toluene conversion rate increased with rising ozone concentration because intermediate products generated by toluene degradation might react with excess ozone to generate free radicals like ·OH, which would improve the toluene mineralization rate of Mn2Co3/Cord catalyst. This study would provide a theoretical support for its industrial application. [ABSTRACT FROM AUTHOR]

Powdered Ni-based catalysts exhibit good performance in the dry reforming of methane (DRM); however, they suffer from limited industrial applicability. Structured monolithic catalysts can overcome these limitations. In this sense, we present the synthesis of Ni–Ce mixed oxide-type catalysts immobilized in cordierite monoliths using a simple coprecipitation method and slurry coating without additives using hydrotalcite precursors for catalyst preparation. Our research explores the role of Ce (0–7 % w/w) as a promoter and the impact of immobilizing mixed oxides (MO) within cordierite monoliths on the physicochemical properties and catalytic performance of non-previously H 2 -reduced materials in DRM at 700 °C. Our findings reveal the favorable impact of Ce on the physicochemical properties of the catalyst in both the powder and monoliths, including smaller crystallite sizes, enhanced CO 2 adsorption, and reducibility with higher Ce loading. The immobilized mixed oxide (MO) maintained its crystalline structure and formed stable, uniform layers with thicknesses below 10 μm in the monoliths. The powders exhibited stable conversions of 70–80% for CH 4 and 66–75% for CO 2 , whereas the monoliths showed conversions of 85–90% for CH 4 and 80–90% for CO 2 at 700 °C and 94,680 mL·g cat −1·h−1. A higher catalyst loading in the monoliths did not result in detrimental catalytic conversion. On average, the monoliths had a higher H 2 /CO ratio (1.25–1.5) compared to the powders (1–1.25), which may explain the increased coke formation rate in the monoliths from methane cracking. Ce improved the stability and reduced coke formation, particularly when the space velocity was lower. This research highlights the significant advantages of immobilizing mixed oxides (MO) in monolithic structures, making them highly promising for potential industrial scale-up. Their stability, recoverability, elimination of high-cost H 2 reduction, and reusability in subsequent catalytic tests contributed to their favorable characteristics. [Display omitted] • Coprecipitation simplifies slurry coatings for monolith immobilization. • Monoliths were prepared without additives. • The monoliths exhibited high stability and consistent performance upon reuse. • Ce improved stability and reduced coke formation at lower space velocities. • Immobilized catalysts produced more carbon, but no pressure drops were observed. [ABSTRACT FROM AUTHOR]

Hydrogen generated in severe accidental conditions poses a threat to nuclear containment once it exceeds the flammability limit in the air. A passive Autocatalytic Recombiner (PAR) device is one of the best options to tackle this scenario. In view of this, we have developed a novel breed of bimetallic Pt–Pd nano-catalysts supported over cordierite by a chemical reduction route. Pt–Pd particles with dimensions ∼4.5–11.5 nm were found to be in a metallic state and amorphous in nature. They were assessed for H 2 and O 2 recombination reactions and found to be catalytically active for the same. Their activity was also established in the presence of various probable contaminants viz. CO, CO 2 , CH 4 , relative humidity, and catalyst wetness. • Pt + Pd bimetallic catalyst was developed for hydrogen mitigation under severe accident conditions. • Ceramic support was used for enhanced properties of the catalyst. • Catalyst exhibits unaltered catalytic activity in presence of various poisons. • Catalyst retains its activity in presence of CO for wider range of concentrations. • Activation energy calculated and compared to earlier reported catalyst. [ABSTRACT FROM AUTHOR]

Cordierite ceramic is usually used for diesel particulate filter owing to its excellent low thermal expansion coefficient and high thermal shock resistance properties. However, the co‐exited intermediate spinel phase can deteriorate the thermal and mechanical performances of cordierite ceramic product, because the spinel phase has much higher thermal expansion coefficient comparing to that of cordierite. In this study, two methods are utilized to reduce the spinel impurity in the cordierite ceramic. On the one hand, rational reaction resources were introduced to decrease spinel production. The formation of intermediate spinel phase is systematically researched by X‐ray diffraction (XRD), scanning electron microscopy (SEM), Raman characterizations and the results clarified the preference of path "Enstatite + Mullite → Cordierite" for less spinel production in comparison to path "Enstatite + Al2O3 → Cordierite + Spinel." Additionally, MgO was introduced as fluxing agent to promote liquid‐phase sintering, thus facilitating the conversion of spinel. On the other hand, the sintering schedule was improved by introducing a holding temperature gradient to promote the diffusion of Si4+ and further promote the conversion of spinel into cordierite. With these methods, the residual spinel phase is minimized, the resulting high‐purity cordierite has a 47% reduction in the thermal expansion coefficient from 3.07 × 10−6/K to 1.63 × 10−6/K compared to the original cordierite sample. [ABSTRACT FROM AUTHOR]

The main goal of this work is to study the effects of some transition metal-oxides, i.e. ZnO, TiO2, and Fe2O3, on inhibition of spinel formation during cordierite fabrication from granite waste, talc, and alumina by direct coagulation casting method. Moreover, the effect of these oxides on sinterability, microstructure, hardness and electrical properties was achieved. The casted specimens were sintered at different temperatures then examined by X-ray diffraction technique to follow the formed phases. The physical properties were determined according to Archimedes rule. The microstructure was also investigated by scanning electron microscope, while the hardness was determined by Vicker's method. The electrical properties were evaluated by an impedance analyzer. The results indicated that sintered cordierite-spinel ceramics were successfully prepared with inhibition of spinel formation after addition of some transition metals and sintering up to 1250 °C. ZnO promoted the formation of spinel while TiO2 and Fe2O3 inhibited the formation of spinel and promoted the formation of cordierite. The ZnO-containing cordierites exhibited their best properties after sintering at 1200 °C, while the samples containing TiO2 and Fe2O3 showed their best properties after sintering at 1250 °C. The physical, mechanical and electrical properties were improved after increasing the amount of added metal oxides. The dielectric constant values were higher for the samples that contain TiO2 than those contain Fe2O3 and ZnO. Moreover, the hardness of all samples was in a narrow range of 6.14–6.61 GPa. [ABSTRACT FROM AUTHOR]

The Pd ion substituted TiO2, synthesized by solution combustion method crystallizes in anatase structure with stable composition Ti1-xPdxO2-x (x = 0.01–0.03) creating an oxide ion vacancy per Pd2+ ion substitution. Over 1.35 mol of H2 per mole of bulk Pd ions, in ~ 5 nm nanocrystalline catalyst Ti1-xPdxO2-x (x = 0.03) is adsorbed at 300 K. On exposure of only hydrogen to Ti0.98Pd0.02O1.98 at 300 K, water is formed making the catalyst wet. On heating in a vacuum, mass loss due to water is 0.026 mol /mole of catalyst meaning 1.3 mol of hydrogen per mole of Pd ion in the catalyst. Pd ion substitution in TiO2 anatase activates lattice oxygen leading to the formation of H2O on exposure to H2 gas at 300 K utilizing lattice oxygen. On heating in air at 650 K the reduced catalyst is regenerated. The catalyst produces a high rate of H2 + O2 recombination up to 9 µmoles−1 g−1 at 300 K, and over 230 µmoles−1 g−1 at 330 K with a TOF of 2000 h−1. The catalyst is coated on cordierite honeycomb avoiding handling of powder catalyst. The rates are highest compared to any catalyst for H2 + O2 recombination known so far. Extensive DFT calculation on (101) surface in Ti31Pd1O63 slab confirmed (a) one oxygen out of 4 bonded to Pd ion in nearly square geometry is fully activated to form water molecule creating an oxide ion vacancy; (b) dissociative adsorption of H2 on one of the Pd as well as oxide ion and not both on Pd ion; (c) exchange of feed oxygen with lattice oxygen during 2H2 + O2 recombination; (d) 2H2 + O2 → 2H2O molecules form per Pd ion in one cycle regenerating the catalyst, Ti0.97Pd0.03O1.97 surface explaining high rates of recombination and (e) Pd ion undergoes redox cycle with Ti and oxide ions acting as charge reservoirs. [ABSTRACT FROM AUTHOR]

Porous geopolymers with sustainable dimensional stability at high temperatures represent a noteworthy challenge for the development of thermomechanical, reliable and multifunctional composites. This study reports on the porosity formation of refractory-reinforced geopolymer paste via hydrogen peroxide decomposition. Reinforcing the slurry with ceramic chamotte and cordierite increases the apparent viscosity more than eight times in the interval to 100 s−1 retaining a pseudoplastic behavior. Cordierite particles increase the plastic viscosity at 6 Pa s and yield stress above 28 Pa. Surprisingly, the particulate ceramic filler acts as a porosity-modifier thereby reducing the mesoporosity region. Microstructural and porosity behavior was studied via digital microscopy, SEM, MIP and micro-CT. The wrinkled morphology of ceramics significantly affects the macroporosity formation in the region of 100 μm reaching a total porosity of ∼60 vol%. The presence of large pores in the macro region and the high distribution of interconnected porosity in ceramics-reinforced composite foams resulted in compressive strengths ranging from 2 to 10 MPa. The effect of curing rate on porosity was most evident in the cordierite reinforcement which led to the occurrence of large interconnected pores. Based on thermomechanical analysis, the ceramic-reinforced foams show high dimensional stability with a reduction in total shrinkage to −0.71 % at 850 °C. These results may foster further developments of innovative routes for the synthesis of geopolymer composite foams for widespread technological applications. [ABSTRACT FROM AUTHOR]