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ABSTRACT Sauce glazed wares of Yaozhou kilns are famous for their high gloss and distinctive glaze color palette varying from yellowish‐brown to reddish‐brown. In this work, sauce glazes were successfully replicated using the traditional technology of Yaozhou kilns. Micro‐Raman spectroscopy, combined with optical microscopy, scanning electron microscopy, x‐ray fluorescence, and reflective spectroscopy, was systematically applied to analyze the chemical composition, nature and distribution of crystals, and the coloration of the glazes. The results show that the yellowish‐brown glaze is mainly original from dendritic ε‐Fe2O3 crystals, whereas the reddish‐brown color is mainly derived from dendritic hematite crystals. Such dendritic structure could account for slightly color variations of the glaze surface observed in different angles, which also reported in Japanese Bizen ceramics. The principal component analysis (PCA) was further applied to study the Raman spectra of these iron oxides. The PCA results effectively indicates the structural disorders of these crystals introduced by ion substitutions. These substitutions could not only stabilize the crystals but also darken the crystals color. Besides, high Mg in the raw materials was found to benefit the growth of magnesioferrite crystals. The relative low level of Fe2O3, high level of SiO2, and CaO may relate to the formation of ε‐Fe2O3 crystals. [ABSTRACT FROM AUTHOR]

In this study, Fe2O3 nanoparticles were doped with varying concentrations of cerium oxide (CeO2) (5%, 10%, and 20%) were synthesized by using a microwave treated co-precipitation method and thereafter, calcined at 600oC temperature for 2hrs. The X-ray diffraction (XRD) analysis revealed that all calcined samples exhibited hexagonal crystalline structures, with a decrease in grain size from 60.547nm to 47.060 nm with increasing CeO2 concentration. Fourier transform infrared (FTIR) spectroscopy confirmed characteristic peaks of hydroxyl group at 3541 cm-1 and 1624 cm-1, while sharp peaks of 471 cm-1 were identified as the O-Ce-O stretching vibrational band. The observed FTIR patterns were consistent with the XRD results supporting the influence of differing ionic radii between Ce4+ and Fe3+ ions. The Magnetic properties were examined through by using a vibrating sample magnetometer (VSM) and revealed that saturation magnetization peaked at 5% CeO2 dopant concentration (Ms = 33.2×10-2 emu/g), while coercivity reached its maximum at 10% concentration (Hc = 548.26 Oe). Conversely, remnant magnetization (Mr) decreased (4.3×10-2, 3.1×10-2, and 0.9×10-2 emu/g) with increasing cerium oxide concentration (5%, 10%, and 20%). [ABSTRACT FROM AUTHOR]

This article discusses the concept of being a connoisseur of minerals and highlights a selection of mineral specimens from the 2024 Tucson Show. The author emphasizes that being a connoisseur is not just about recognizing expensive minerals or knowing which specimens are considered the best, but also requires a deep knowledge of mineralogy, the ability to observe and handle specimens, and an understanding of rarity. The article features photographs and descriptions of various minerals, including quartz crystals with hydrocarbon inclusions, gold specimens from Oregon, neptunite from California, and fluorite from China. The author invites readers to share their reactions to the specimens and comments. [Extracted from the article]

The objective of this study was to synthesize α-Fe2O3 (hematite) crystals through a mechanical precipitation approach and investigate the influence of elevated annealing temperatures on their optical and magnetic properties. Initially, iron sand was mechanically ground into fine powder using an agate mortar. This powder was then solubilized in 400 mL of 37% HCl and subsequently filtered using Whatman filter paper No. 42. The resulting filtrate was stirred magnetically at 200 rpm while ammonium hydroxide was gradually introduced until a pH of 8 was achieved, precipitating the desired product. The precipitate was separated, washed with deionized water, and dried on a hot plate at 100°C for one hour. The dried product was divided into four samples and each was subjected to annealing at temperatures of 300°C, 400°C, 500°C, and 550°C for one hour, respectively. X-ray diffraction (XRD) analysis, corroborated by the Crystallographic Open Database (COD), confirmed that the synthesized hematite crystals exhibited a hexagonal structure belonging to the R-3c space group. A notable decrease in grain size was observed with increasing annealing temperature, shrinking from approximately 0.44 µm at 300°C to around 0.36 µm at 500°C. This trend suggests that higher temperatures facilitate the disintegration of aggregates into finer particles. Vibrating Sample Magnetometry (VSM) revealed that the hematite crystals possessed high coercivity and remanence, both of which decreased with rising annealing temperatures, indicative of their ferromagnetic nature. UV-Visible spectroscopy identified maximum absorption within the 200-202 nm range, with the peak absorption occurring at 201.56 nm for crystals annealed at 500°C. Additionally, bandgap energy was observed to increase from 2.632 eV at an annealing temperature of 300°C to 3.708 eV at 550°C. In conclusion, the mechanical precipitation method effectively produced ferromagnetic hematite microparticles from natural iron sand, with their properties significantly influenced by the annealing temperature. These findings offer insights into the tunable nature of hematite's optical and magnetic characteristics, with implications for their application in various technological domains. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recycling of jarosite residues by a one-step hydrothermal method was proposed. • Transformation process included jarosite pyrolysis and hematite crystal formation. • Entrained valuable metal resource dissolved into aqueous solution for recycling. • Hematite product met requirements of raw material for ironmaking after roasting. • Hematite product possessed superior characteristics of iron oxide red pigment. Jarosite [MeFe 3 (SO 4) 2 (OH) 6 ] is a typical non-ferrous smelting slag produced in the process of iron removal from hydrometallurgical solution, which contains a large number of valuable and toxic metal elements. Treating the complex and hazardous jarosite residue in an economically and environmentally sound way has always been an urgent problem. A novel one-step hydrothermal treatment method was proposed in this paper for recycling of jarosite residues. It can be seen from the XRD and TEM results that jarosite residues could be completely transformed into hematite crystal particles under hydrothermal conditions at temperature above 220℃. Meanwhile, other valuable metal components (such as nickel sulfate hexahydrate) entrained in the residue will be dissolved in the aqueous solution, which can be reused in the hydrometallurgical process. Through phase composition analysis of the hydrothermal process, it is concluded that jarosite was firstly pyrolyzed to generate Fe3+. The obtained Fe3+ was then hydrolyzed to Fe (OH) 3 , which was transformed into Fe 2 O 3 through dehydration condensation and directional arrangement. Further roasting the hematite particles, the obtained product contained 62.57 % of Fe, but only 0.21 % of S and 0.04 % of As, which meets the requirements of raw materials for iron making. In addition, compared with the current international standard ISO 1248:2006 (E), the obtained hematite particles with nanometer size and single crystal structure can be used as iron oxide red pigment. Overall, the one-step hydrothermal treatment of jarosite residues followed by reduction roasting not only realizes the economic recycling of the metal resources, but also solves the stacking problem of those hazardous residues. [ABSTRACT FROM AUTHOR]

Phosphorus is an essential nutrient for plant and animal growth, while excessive phosphorus discharges can cause eutrophication of water bodies, leading to deterioration of water quality and posing serious risks to biodiversity and human health. Hematite is abundant on the Earth's surface and plays a key role in phosphorus cycle. In particular, hematite nanoparticles may adsorb organic or inorganic phosphorus, consequently affecting phosphorus fate and effects. Yet, how the intrinsic properties of hematite (e.g., crystal facet) affect its adsorption process of phosphorus remains unclear. Here, three hematite nanoparticles with different exposed crystal facets were controllably synthesized to investigate their adsorption of phosphate under different pH conditions. The results revealed that the efficiency of hematite for adsorbing the phosphate depends on the crystal facets of hematite in the order of {104} > {110} > {001}. The phosphate adsorption on the hematite surface involves inner-sphere complexation between the phosphate and surface hydroxyl groups of hematite. The facet-dependent adsorption affinity of phosphate to hematite is mainly determined by the content of singly coordinated hydroxyl groups of hematite. These findings are useful to evaluate the potential environmental risks of iron oxide nanoparticles as a medium to the biochemical cycle of P element. [ABSTRACT FROM AUTHOR]

The use of natural catalysts in various processes, including the electro-Fenton (EF) process, is a topic of interest in current research and development. Natural catalysts are being explored as potential alternatives to conventional catalysts due to their advantages such as sustainability, low-cost, and environmental compatibility. It is worth noting that the application of natural catalysts in the EF process is an active area of ongoing research, and their full-scale implementation may still require further development and optimization. That is why in our work, we chose to use hematite and pyrite as natural catalysts in the degradation of the black azo dye Eriochrome Black T (EBT) by EF process. Color and chemical oxygen demand (COD) removal efficiencies were compared with those obtained with the conventional catalyst (FeSO4). The pyrite-EF process followed a pseudo-second-order and was found to be more efficient than the hematite-EF process due to the self-adjustment of its pH, it gave slightly lower color (90.30%) and COD (89.20%) removal rates than those obtained with the conventional catalyst (93.05% and 92.06%) after 60 min of treatment. The morphology, chemical composition and crystal structure of hematite and pyrite samples were identified by scanning electron microscopy, X-ray fluorescence and X-ray diffraction analyses. Furthermore, the study of some operating parameters effects allowed determining the optimal conditions for treatment of the Eriochrome Black T solution: 0.03 g·L-1 (pyrite dose), 8 × 10-3 M (supporting electrolyte concentration) and 15 mA·cm-2 (current density). The pyrite-EF process showed similar behavior to that of FeSO4-EF with a low energy consumption. Therefore, EBT can be efficiently removed electrochemically using natural pyrite as an eco-friendly catalyst. [ABSTRACT FROM AUTHOR]

Crystal dissolution, which is a fundamental process in both natural and technological settings, has been predominately viewed as a process of ion-by-ion detachment into a surrounding solvent. Here we report a mechanism of dissolution by particle detachment (DPD) that dominates in mesocrystals formed via crystallization by particle attachment (CPA). Using liquid phase electron microscopy to directly observe dissolution of hematite crystals — both compact rhombohedra and mesocrystals of coaligned nanoparticles — we find that the mesocrystals evolve into branched structures, which disintegrate as individual sub-particles detach. The resulting dissolution rates far exceed those for equivalent masses of compact single crystals. Applying a numerical generalization of the Gibbs-Thomson effect, we show that the physical drivers of DPD are curvature and strain inherently tied to the original CPA process. Based on the generality of the model, we anticipate that DPD is widespread for both natural minerals and synthetic crystals formed via CPA. Crystal dissolution has been predominately viewed as a process of ion-by-ion detachment into a surrounding solvent. Here, the authors report an alternative mechanism of dissolution by particle detachment. [ABSTRACT FROM AUTHOR]

The Western Indonesia Bauxite Province in Kalimantan is a lateritic bauxite region with a complex history and poorly known sustainable metal contents within the bauxite residue. Bauxite residue produced using the Bayer process contains, notably, scandium. We present new geochemical, mineralogical and geological data from the lateritic bauxite and red mud from the active mine and deposit, which allow us to investigate the behaviour of critical elements during weathering. The geochemical analysis and translated isocon results have shown that the content of scandium in red mud is higher than the average concentration of crustal rocks and is concentrated in the ferrite layer and bauxite residue. A positive correlation between the existence of iron oxyhydroxide mineral in the residual iron-rich layer and red muds with the rare earth elements (REEs) and scandium concentrations may be interpreted as a scavenging effect of mobile REEs. The weathering and leaching processes in bauxite allows the adsorption of the trivalent scandium cation (Sc3+) on goethite and are followed by ionic substitution with other trivalent cations in crystals of hematite. The study illustrates the importance of understanding processes during weathering and laterization for geochemical processes and REE exploration in tropical areas. Supplementary material: Material A, (A) Mineralogical profile of the bauxite, ferrite, and tonalite in Tayan and Mempawah, (B) Ternary diagram of bauxite and their parent rocks, (C) Trace element ratios in bauxite; Material B, Spearman's correlation rank of bauxite and associated rocks from Tayan mine (n = 35); Material C, (A) XRD patterns of representative samples from the Tayan mine and Mempawah deposit, West Kalimantan, (B) Typical normal (left) and continuum (right) removed reflectance spectral curves of samples are available at https://doi.org/10.6084/m9.figshare.c.6689139 Thematic collection: This article is part of the Geochemical processes related to mined, milled, or natural metal deposits collection available at: https://www.lyellcollection.org/topic/collections/geochemical-processes-related-to-mined-milled-or-natural-metal-deposits [ABSTRACT FROM AUTHOR]

Magnetic field sensors using magnetoelectric (ME) effects in planar ferromagnetic-piezoelectric heterostructures convert a magnetic field into an output voltage. The parameters of ME sensors are determined by characteristics of the magnetic constituent. In this work, the low-frequency ME effects in heterostructures comprising a layer of antiferromagnetic hematite α-Fe2O3 crystal with easy-plane anisotropy and a piezoelectric layer are studied. The effects arise due to a combination of magnetostriction and piezoelectricity because of mechanical coupling of the layers. The field dependences of magnetization and magnetostriction of the hematite crystal are measured. The resonant ME effects in the hematite-piezopolymer and hematite-piezoceramic structures are studied. The strong coupling between magnetic and acoustic subsystems of hematite results in a tuning of the acoustic resonance frequency by the magnetic field. For the hematite layer, the frequency tuning was found to be ~37% with an increase in the bias field up to 600 Oe. For the hematite-PVDF heterostructure, the frequency tuning reached ~24% and the ME coefficient was 58 mV/(Oe∙cm). For the hematite-piezoceramic heterostructure, the frequency tuning was ~4.4% and the ME coefficient 4.8 V/(Oe∙cm). Efficient generation of the second voltage harmonic in the hematite-piezoceramic heterostructure was observed. [ABSTRACT FROM AUTHOR]

Only a few iron precursors that can be used in the atomic layer deposition (ALD) of iron oxides have been examined thus far. This study aimed to compare the various properties of FeOx thin films deposited using thermal ALD and plasma-enhanced ALD (PEALD) and to evaluate the advantages and disadvantages of using bis(N,N′-di-butylacetamidinato)iron(II) as an Fe precursor in FeOx ALD. The PEALD of FeOx films using iron bisamidinate has not yet been reported. Compared with thermal ALD films, PEALD films exhibited improved properties in terms of surface roughness, film density, and crystallinity after they were annealed in air at 500 °C. The annealed films, which had thicknesses exceeding ~ 9 nm, exhibited hematite crystal structures. Additionally, the conformality of the ALD-grown films was examined using trench-structured wafers with different aspect ratios. [ABSTRACT FROM AUTHOR]

Quartz is so variable in its colors, crystal habits, inclusions, and other features that the species cannot be fully described in a single Connoisseur's Choice column. Single faden quartz crystal with the c-axis perpendicular to the faden perched on a group of quartz crystals (7.5 cm) from Amsteg, Intschitobel Valley, Uri, Switzerland. Faden quartz is one of two similar kinds of quartz crystal aggregates that occur in alpine veins. Amethyst, citrine, rose quartz, and smoky quartz are varietal names based on color. [Extracted from the article]

Black glazed wares (Wujin wares) and hare fur's decorated black glazed wares (HF wares) are ones of typical production of Jian kilns, China during Song Dynasty. In this work, Wujin wares and HF wares excavated in Jian kiln complex (Yulinting kilns, Daluhoumen kilns and Luhuaping kilns) were systematically analyzed by optical microscope, X‐ray fluorescence spectroscopy and micro‐Raman spectroscopy. The results show that the index of glassy polymerization (Ip) of Wujin wares is smaller than black areas of HF wares, indicating the higher firing temperature used for HF wares. Several pseudobrookite, rutile, hematite and quartz crystals were detected in glazes of Wujin wares while a great number of ɛ‐Fe2O3 crystals was observed in brown stripes of HF wares. Besides, wares in different kiln sites present obviously differences in bubble distribution and glassy structure, indicating a lower firing temperature used for Yulinting kilns than those of Daluhoumen kilns and Luhuaping kilns. [ABSTRACT FROM AUTHOR]

The purposes of this study were: (1) to review the preparation and characterization of the intergrowth between goethite and hematite crystals; and (2) to propose a schematic diagram of the epitaxial relationships among three sets of (100) goethite twin crystals associated with the (001) orientation of the hexagonal prism of hematite. The Fe(ClO4)3 solution was prepared and aged at 70°C, which precipitated goethite initially and produced hematite later with prolonged aging. Goethite and hematite aged for 20 days were observed as star-shaped and hexagonal prisms, respectively. The results suggest that hematite could form later using goethite as a template surface. A selected area electron diffraction (SAED) pattern showed the epitaxial relationship among three sets of (100) goethite intergrowth crystals and hexagonal prisms with the (001) orientation of hematite. Goethite can be produced as lath-, X-, K-, or star-shaped crystals on the (100) orientation, depending on the Fe(ClO4)3 concentrations and the addition of HClO4 to Fe solution samples which were aged for a prolonged period at room temperature. The initial solubility products [(Fe3+)(OH–)3] of the sample solution, rather than the nature of the nuclei, are the key factors governing the formation of goethite or hematite. The addition of acids and high concentrations of iron solutions extend the secondary hydrolysis and induction period (IP) and favor the formation of hematite. The index of the SAED pattern of the star-shaped goethite intergrowth twin crystal has a (100) plane parallel to this basal plane and rotates at a 60° angle between two or three sets of lath-shaped goethite crystals, which share the (011) plane and form goethite twins with 'interpenetrated' crystal growth. Stereoscopic viewing using Oak Ridge Thermal Ellipsoid Plot (ORTEP) and CrystalMaker software was deployed to explore the relationship and configuration of oxygen atoms between pseudo-hexagonal (100) goethite associated with hexagonal (001) hematite lattice planes. A schematic diagram of the epitaxial relationship between star-shaped (100) goethite, which is acting as a template facilitating later precipitation of (001) hexagonal prisms of hematite on it, is presented. [ABSTRACT FROM AUTHOR]

Recovery of metallurgical dust by sintering inevitably incorporates Zn into the sintered ore, which can have a significant impact on the ore formation process and the quality of the resulting ore. Through miniature-sintering experiments and theoretical first-principles calculations, this paper analyzes in detail the influencing mechanism of Zn on the sintering mineralization process. The results showed that the lowest assimilation temperatures (LAT) of the reagent mixture did not change significantly with increasing ZnO content, the liquid-phase fluidity index (IFL), and the magnetite content in the sintered ore decreased, and the silico-ferrite of calcium and aluminum (SFCA) content increased. However, with increasing ZnFe2O4 content, the LAT, IFL, and magnetite contents of the reagent mixture increased, and the content of SFCA decreased. Since the Zn2+ adsorption energies of hematite and magnetite are higher than that of SFCA, Zn was mainly present in the hematite and magnetite in the sintered ore. In addition, Zn was doped into the hematite and magnetite crystals, resulting in a decrease in their crystalline strengths, so the microhardness values of the hematite and magnetite in the sintered ore gradually decreased with increasing Zn content. [ABSTRACT FROM AUTHOR]

Massif-type mafic intrusions (gabbro and anorthosite) are known for their considerable resources of vanadium-bearing iron–titanium oxide ores. Massive-type gabbroic and anorthosite rocks are frequently associated with magmatic rocks that have significant quantities of iron, titanium, and vanadium. The most promising intrusions that host Fe-Ti oxide ores are the gabbroic rocks in the south-eastern desert. The ilmenite ore deposits are hosted in arc gabbroic and anorthosite rocks. They are classified into three types, namely black ore, red ore, and disseminated ore. The black ilmenite ore is located at the deeper level, while the oxidized red ore is mainly located at or near the surface. Petrographically, the gabbro and ilmenite ores indicate a crystallization sequence of plagioclase, titaniferous pyroxene, and ilmenite. This reveals that the ilmenite is a magmatic deposit formed by the liquid gravity concentration of ilmenite following the crystallization of feldspar and pyroxene. Meanwhile, quartz, tremolite, zoisite, and opaque minerals are accessory minerals. The Fe-Ti ores are composed of ilmenite hosting exsolved hematite lamellae of variable sizes and shapes, gangue silicate minerals, and some sulfides. The X-ray diffraction (XRD) data reveal the presence of two mineral phases: ilmenite and hematite formed by the unmixing of the ferroilmenite homogeneous phase upon cooling. As a result, the ore is mostly made up of hemo-ilmenite. Using an electron microscope (SEM), as well as by observing the textures seen by the ore microscope, ilmenite is the dominant Fe-Ti oxide and contains voluminous hematite exsolved crystals. Under the scanning electron microscope, ilmenite contained intergrowths of hematite as a thin sandwich and lens shape. The formation of hematite lamellae indicates an oxidation process. Mineral chemistry-based investigations reveal late/post-magmatic activity at high temperatures. The examined ilmenite plots on the ferro-ilmenite line were created by continuous solid solution over 800 °C, whereas the analyzed magnetite and Ti-magnetite plot near the magnetite line and were formed by continuous solid solution exceeding 600 °C. [ABSTRACT FROM AUTHOR]

Currently, environmental pollution by various organic pollutants (e.g., organic dyes) is a serious, emerging global issue. The aqueous environment is highly exposed to the harmful effects of these organic compounds. Furthermore, the commonly applied conventional purification techniques are not sufficient enough. Heterogeneous photocatalysis and the photo-Fenton process are effective, low-cost and green alternatives for the removal of organic pollutants. In this study, different iron(III) oxide/titanium(IV) oxide/polyvinyl chloride (Fe2O3/TiO2/PVC) nanocomposites in tablet form were investigated in the photodegradation of methylene blue (MB) under simulated sunlight, and their possible antibacterial effects were examined. The newly synthesized nanocomposites were characterized by scanning electron microscope, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, and Raman spectroscopy. The results showed a hematite crystal form in the case of Fe2O3(2) and Fe2O3 samples, while the Fe2O3(1) sample showed a combination of hematite and synthetic mineral akaganeite. The highest photocatalytic efficiency was achieved in the presence of Fe2O3/TiO2/PVC, when 70.6% of MB was removed. In addition, the possible photo-cleaning and reuse of the mentioned photocatalyst was also examined. Based on the results, it can be seen that the activity did not decrease after five successive runs. Nanocomposites also exhibited mild antibacterial effects against the two tested Gram-positive bacteria (S. aureus and B. cereus). [ABSTRACT FROM AUTHOR]

Conclusion Ferruginous quartz is a well-established variety of impure quartz caused by dense concentrations of fine-grained hematite or (less commonly) goethite that precipitated while crystals of colorless quartz were growing. Quartz variety amethyst reddened by hematite inclusions (7.8 cm tall), an example of hematitic quartz, from the Kakamanurle mine, Karur, India. Associated with black, shiny hematite (specularite) crystals on red-brown massive hematite, they make striking specimens - the very best matrix specimens of ferruginous quartz available. Quartz like many minerals is I allochromatic i , meaning that it occurs in a wide variety of colors. [Extracted from the article]

The ancient porcelain is the treasure of Chinese civilization. In this paper, multiple surface analysis tools were applied to characterize the attractive silvery bright spots on the glaze of black-glazed tea bowl fragment. The raindrop-shaped silver flecks covering the surface were symbols of North China oil spots. High-resolution time of flight-secondary ion mass spectrometry（TOF-SIMS） data confirmed the main component of the oil spot was iron oxide. Positive ions were Fe+（m/z 55.93）, FeO+（m/z 71.93）, Fe2O+（m/z 127.86）, and negative ions were FeO-（m/z 71.93）, FeO-2（m/z 87.92）. A series of peaks were detected by micro-Raman spectroscopy, such as 230, 294, 412, 502, 611, 1 337 cm-1. This suggested existence of hematite（α-Fe2O3） in the spot. Secondary ion imaging of TOF-SIMS indicated the oil spots（～120 μm） was formed by self-organization and dispersion of hundreds hexagonal hematite crystal（～2-10 μm）. Hematite was spatially complementary to alkaline calcareous glaze that contains silicon, aluminum, calcium, and sodium. TOF-SIMS depth profiling of the spot suggested a more than 5 μm continuous hematite layer on the glaze of black-glazed tea bowl. The main mineral of α-Fe2O3 crystals was hematite, which was ochre usually. Specular hematite, a subspecies of hematite with silver or black color, was believed to play critical role in the formation of the oil spot. With the optical microscope observations, we believed that the silvery material on the surface of the oil spots should be a thin layer of specular hematite and the lower ochre layer was hematite. In fact, the oil spot appeared silvery-white and reflective when viewed from 15° to 165°, while it appeared ochre when the angles of gaze was not greater than 15° from the glazed surface of the specimen. The extraordinary visual property of color changing with different angle of gaze formed the charm of Song dynasty oil spot tea bowls. With these results, a hypothesis for the formation of the North China oil spots was enlightened. The molten phase of Fe-rich soy-black glaze gradually formed micron-sized hematite particulates at sealed kiln of high temperature（1 250 ℃）. When the kiln was unsealed, the hot porcelain was exposed to cold air immediately. A thin layer of specular hematite was generated on top of hematite particulates. [ABSTRACT FROM AUTHOR]

The (110) facets of hematite have excellent adsorption performance for chromium. We aim to obtain hematite with a large specific surface area and exposed (110) facets by using natural needle-like goethite as the precursor. The derived hematite shows a significant increment in the removal capacity of chromium by six times compared with goethite under the same experimental conditions. Structural model fitting of extended X-ray absorption fine structure (EXAFS) spectroscopy suggested that the interatomic distance of Cr-Fe was approximately 3.6 Å for the Cr (VI) coordinated hematite with exposed (110) facets, which was characteristic of the form of bidentate binuclear surface complex. Molecular dynamic simulations for the arrangement of Cr (VI) in (110) facets of goethite and hematite indicated the superiority of hematite adsorption for chromium. We optimized efficient and economic permeable reactive barrier (PRB) materials by crystal plane adjustment based on these experimental and theoretical results. It was found that the life span of the column even reached 610 PVs when the initial concentration of Cr (VI) was 20 mg/L, which indicates its potential application in the field of PRB medium material. [ABSTRACT FROM AUTHOR]

The concentration of guest elements (dopants) into host materials play an important role in changing their intrinsic electrical and optical properties. The existence of hetero-element induce defect in crystal structure, affecting conductivity. In the current work, we report Cu2+ ion into hematite in the defectronics point of view and their photoelectrochemical properties. Crystal distortion in the structure of hematite is observed as the amount of dopant increases. Among 1, 3 and 5 mol% of Cu2+ doped hematite, the existence of 1 mol% of Cu2+ ion into hematite crystal structure produce photocurrent value of 0.15 mA/cm2, IPCE value of ~ 4.7% and EIS value of ~ 2000 Ω/cm2 as best performances. However, further increasing dopants increases the number of interstitial defects, which cause the deformation of intrinsic lattice structure. [ABSTRACT FROM AUTHOR]

So far unknown anisotropic properties of out-of-phase magnetic susceptibility (opMS) of hematite and their bearing on understanding the origin of hematite magnetism were investigated on example of four single crystals from Minas Gerais, Brazil. The research comprised measurement of directional variation of field-dependent and frequency-dependent opMS and testing whether the anisotropy of opMS can be represented by the second rank tensor. It was found that the opMS shows strong field dependence along basal plane and only weak field dependence along c-axis. As for the frequency dependence, it is virtually non-existent along the basal plane. Along the c-axis, the opMS is similar at frequencies 976 and 3904 Hz, while at 15616 Hz it is clearly higher. Consequently, opMS is dominantly due to weak field hysteresis. The minimum opMS directions are parallel to the c-axis, while the other two principal directions lie within basal plane. The degree of anisotropy is extremely high (ratio of maximum opMS to minimum opMS ≫100) and the anisotropy ellipsoid is very oblate. In stereographic diagrams, the opMS contours very roughly resemble the theoretical contours calculated from opMS tensor. However, the differences between measured and theoretical values in directional opMS are clearly higher than the measuring error and are distributed very non-homogeneously. This indicates that the second rank tensor is only very approximate representative of the spatial variation of the directional opMS of hematite single crystals. Earlier model of hematite magnetism assuming slightly scanted antiferromagnetism along the c-axis and strongly canted antiferromagnetism or even weak ferromagnetism along the basal plane is supported. [ABSTRACT FROM AUTHOR]

Hematite (α-Fe2O3) is an antiferromagnetic material with a very low spin damping and high Néel temperature. The temperature dependence of the antiferromagnetic resonance in a bulk single crystal of hematite was characterized from room temperature up to the Néel temperature in the frequency range of 0.19–0.5 THz. From these data, the Néel temperature was estimated as 966 K. [ABSTRACT FROM AUTHOR]

Different crystal formation patterns of Fe x O y species over two zeolitic supports were observed. Starch was used in the synthesis of ZSM-5 to generate a zeolite with supplemented mesoporosity in addition to the traditional microporous structure. Fe was incorporated into the zeolitic matrices through hydrothermal synthesis of hematite nanoparticles. Two zeolitic catalysts with different activities in a photo-Fenton reaction were obtained. The materials were thoroughly characterised by XRD, UV–Vis DRS, TPR, FIT-IR, NMR, SEM, EDS, TEM, Mössbauer Spectroscopy and N 2 adsorption-desorption isotherms. Methyl orange, a persistent anionic dye in water, was chosen for photocatalytic degradation testing. Promising results were obtained when hematite nanoparticles were supported onto hierarchical ZSM-5. The presence of extra-framework aluminium served as a nucleation site, leading to the formation of numerous smaller hematite crystals, enhancing the photocatalytic performance of the catalyst. [Display omitted] • ZSM-5 zeolites as supports for hematite nanoparticles in photo-Fenton catalysts. • Micro/mesoporous zeolite impact on the synthesis of hematite nanoparticles. • More stable catalysts obtained with micro/mesoporous ZSM-5 (Fe-ZA). • Extra framework Al plays a vital role in the incorporation of hematite on Fe-ZA. • Highlighted efficiency of Fe-ZA on the photocatalytic degradation of methyl orange. [ABSTRACT FROM AUTHOR]

The Linfen kiln complex, one of the most representative of Shanxi kilns, is famous for its oil spotted glazed ware production. In this work, micro‐Raman spectroscopy was applied to analyze the nature of the rusty oil spot pattern of a bowl fragment from Linfen kilns. Crystals of polygonal shape found in the spots at the glaze surface and around bubbles in the cross‐section of the glaze were identified as hematite. Their distribution in the glaze suggests that nucleation seeds and small crystals are carried toward the surface by the rise of bubbles during the heating step of the firing. Raman spectra combined with energy‐dispersive spectrometry (EDS) measurements also suggest that Fe ions in hematite crystals are partially substituted, causing the variation of band position and full width at half maximum (FWHM) of the spectra. Dendritic ε‐Fe2O3 was identified in brown areas of the black glaze, as well as pseudobrookite crystals of tens of microns in the cross‐section of the glaze. The degree of the glaze polymerization (A500/A1000) was calculated at 1.85, indicating a firing temperature lower than 1300°C, consistent with the archaeological data. [ABSTRACT FROM AUTHOR]

• Crystal growth mechanism of hematite in high-temperature lead-free glass frit was investigated. • Hematite particles slightly grew due to sintering up to near softening point of the frit. • Hematite crystal growth occurs through Ostwald ripening above softening point. • Resultant hematite crystal was surrounded by low index crystal planes having low surface free energy. To elucidate the crystal growth process of hematite in high-temperature lead-free multicomponent alkali borosilicate glass, which is essentially important to control the color of red overglaze enamels, frit and hematite mixture is heat-treated and subjected to microscopic observations. Hematite particles slightly grew due to sintering at low temperature. Once the glass matrix formed near the softening point of frit, hematite dissolved into glass fluid. Hematite crystal growth concomitantly ensued with decrease in the number of hematite particles via Ostwald ripening as the temperature increased. The grown particles exhibited an anisotropic morphology with straight outlines reflecting crystal planes, the morphology of which is completely different from those grown by sintering and particles prior to heating. These results suggest that comprehensive understanding of frit and hematite from the perspectives of glass science and chemistry as well as powder technology are important to truly control the color of red overglaze enamels. [ABSTRACT FROM AUTHOR]

Ceramic glass foam/foams (CGF) from two different F-class fly ashes were produced via a well-known simple conventional sintering method using sodium silicate (Na 2 SiO 3) as a foaming and fluxing agent. The research aimed to understand the effects of each fly ash, Na 2 SiO 3 ratio, and sintering conditions on the properties and microstructure to produce a commercial CGF of low thermal conductivity. The chemical composition of fly ash from the thermal power plants of Tunçbilek and Seyitömer were quite similar but had different melting temperatures and microstructures. While the foam structure was successfully obtained at 1100 °C with 30 wt.% Na 2 SiO 3 from Tunçbilek fly ash, a similar structure was obtained at 1150 °C from the Seyitömer fly ash. The effects of Na 2 SiO 3 content and sintering temperature on the properties and microstructure of the CGF from the Tunçbilek fly ash of a lower melting point, in particular, were investigated systematically. The optimal sintering temperatures were determined to be 1200, 1150, and 1100 °C at the highest fly ash ratios of 90, 80 and 70 wt.%, respectively. The CGF were produced with 69.76–75.43% porosity, 0.55–0.69 gr/cm3 bulk density, 3.2–5.35 MPa compressive strength and 0.10–0.21 W/(m K) of low thermal conductivity. XRD results showed that optimal CGF samples mainly contained spinel, quartz and hematite crystal phases and amorphous phase. In this research, a thermal insulation material was successfully produced using an industrial waste completely with a well-known simple method. It is thought that this will contribute beneficially to the environment and the economy. [ABSTRACT FROM AUTHOR]

Impulsive stimulated Brillouin scattering (ISBS) has emerged as a noninvasive means to determine the elastic properties of transparent materials. Here, we report on time-resolved broadband ISBS reflectivity measurements in single crystal hematite, α -Fe2O3. We found that the observed transient reflectivity changes are best described by the known strain propagation model (SPM) and introduced a simple derivation of the ISBS-SPM formula based on ray tracing, which accounts for the presence of the interface. Measurements at different incident probe beam angles illustrate a plausible approach toward determining the speed of sound in transparent media without any prior knowledge of their dielectric properties and vice versa. [ABSTRACT FROM AUTHOR]

[Display omitted] Photoelectrochemical (PEC) water splitting for solar energy conversion into chemical fuels has attracted intense research attention. The semiconductor hematite (α-Fe 2 O 3), with its earth abundance, chemical stability, and efficient light harvesting, stands out as a promising photoanode material. Unfortunately, its electron affinity is too deep for overall water splitting, requiring additional bias. Interface engineering has been used to reduce the onset potential of hematite photoelectrode. Here we focus instead on energy band engineering hematite by shrinking the crystal lattice, and the water-splitting onset potential can be decreased from 1.14 to 0.61 V vs. the reversible hydrogen electrode. It is the lowest record reported for a pristine hematite photoanode without surface modification. X-ray absorption spectroscopy and magnetic properties suggest the redistribution of 3 d electrons in the as-synthesized grey hematite electrode. Density function theory studies herein show that the smaller-lattice-constant hematite benefits from raised energy bands, which accounts for the reduced onset potential. [ABSTRACT FROM AUTHOR]

• Advanced electrochemical techniques employed to track charge dynamics. • In-situ modifications can improve the charge carrier kinetics. • Ta+5 simultaneously dopes and segregates at hematite crystal surfaces. • Na+ changes hematite morphology but it has limited impact in the carrier kinetics. • Zn+2 hinders charge separation and increases bulk recombination. This letter focuses on monitoring alterations in the charge carrier dynamics associated with in-situ modifications into hematite photoanodes, employing advanced electrochemical techniques. A simple and scalable polymeric precursor solution, deposited by spin-coating, was employed to synthesize hematite based photoanodes. Among various modifications, Tantalum (Ta+5) shows the most promising results, yielding a hydrogen production rate of 24.0 μmol cm−2h−1 at 1.23V RHE. This is attributed to Ta5+ segregation at hematite grain surface, which facilitates the charge transport efficiency and leads to higher external quantum efficiency. Conversely, sodium (Na+) primarily increases the film thickness with limited observable effects on charge carrier dynamics, while zinc (Zn+2) adversely affects hematite performance due to its negative effect on charge separation efficiency and increased bulk recombination. [ABSTRACT FROM AUTHOR]

As shown in the literature several times, the calculation of the anisotropy of magnetic susceptibility (AMS) of hematite single crystals using standard linear AMS theory reveals that the calculated minimum principal susceptibility is parallel to the crystallographic c -axis, but is negative, which is however not due to diamagnetism as evidenced by direct measurements of susceptibility along the principal directions. Susceptibility of a few hematite single crystals from Minas Gerais, Brazil, was measured in 320 directions using a special 3-D rotator and the measurements were processed through AMS calculation by means of standard linear theory and through constructing contour diagrams in equal-area projection. In addition, the susceptibility was in detail measured in three perpendicular planes approximately passing through the main crystallographic directions. The crystals show extremely high anisotropy, the susceptibility measured along the basal plane is several hundred times higher than that along the c -axis and the AMS ellipsoids are very oblate. The contour diagrams show relatively simple patterns of directional susceptibilities, similar to those of the second-rank tensor. Fitting tensor to measured hematite grains results in small but negative minimum principal susceptibility. Nevertheless, summation of many oriented grains filters out the non-tensorial parts of the grain susceptibility in multicrystal assemblages, the AMS of which is well represented by a tensor. [ABSTRACT FROM AUTHOR]

Samples of nanoscale hematite, α-Fe2O3, with different surface geometries and properties have been studied with inelastic time-of-flight neutron scattering. The 15 nm diameter nanoparticles previously shown to have two collective magnetic excitation modes in separate triple-axis neutron scattering studies have been studied in further detail using the advantage of a large detector area, high resolution, and large energy transfer range of the IN5 TOF spectrometer. A mesoporous hematite sample has also been studied, showing similarities to that of the nanoparticle sample and bulk α-Fe2O3. Analysis of these modes provides temperature dependence of the magnetic anisotropy coefficient along the c-axis, κ1. This is shown to remain negative throughout the temperature range studied in both samples, providing an explanation for the previously observed suppression of the Morin transition in the mesoporous material. The values of this anisotropy coefficient are found to lie between those of bulk and nano-particulate samples, showing the hybrid nature of the mesoporous 3-dimensional structure. [ABSTRACT FROM AUTHOR]

Dr Josh Makepeace is an Associate Professor in Materials Chemistry and UK Research and Innovation (UKRI) Future Leaders Fellow at the University of Birmingham. Raised in Australia, Josh started his journey in chemistry research at Flinders University of South Australia, investigating the origin of hematite crystals in William Bligh's naval logbooks, and the detection of pesticides in waterways. [ABSTRACT FROM AUTHOR]

Magnetite and hematite iron oxides are minerals of great economic and scientific importance. The oxidation of magnetite to hematite is characterized as a topotaxial reaction in which the crystallographic orientations of the hematite crystals are determined by the orientation of the magnetite crystals. Thus, the transformation between these minerals is described by specific orientation relationships, called topotaxial relationships. This study presents electron‐backscatter diffraction analyses conducted on natural octahedral crystals of magnetite partially transformed into hematite. Inverse pole figure maps and pole figures were used to establish the topotaxial relationships between these phases. Transformation matrices were also applied to Euler angles to assess the diffraction patterns obtained and confirm the identified relationships. A new orientation condition resulting from the magnetite–hematite transformation was characterized, defined by the parallelism between the octahedral planes {111} of magnetite and rhombohedral planes of hematite. Moreover, there was a coincidence between one of the octahedral planes of magnetite and the basal {0001} plane of hematite, and between dodecahedral planes {110} of magnetite and prismatic planes of hematite. All these three orientation conditions are necessary and define a growth model for hematite crystals from a magnetite crystal. A new topotaxial relationship is also proposed: (111)Mag || (0001)Hem and ||. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide is a highly valuable chemical, and electrocatalytic oxygen reduction towards H2O2 offers an alternative method for safe on‐site applications. Generally, low‐cost hematite (α‐Fe2O3) is not recognized as an efficient electrocatalyst because of its inert nature, but it is herein reported that α‐Fe2O3 can be endowed with high catalytic activity and selectivity via the engineering of facets and oxygen vacancies. Density‐functional theory (DFT)calculations predict that the {001} facet is intrinsically selective for H2O2 production, and that oxygen vacancies can trigger the high activity, providing sites for O2 adsorption and protonation, stabilizing the *OOH intermediate, and preventing cleavage of the OO bond. The synthesized oxygen‐defective α‐Fe2O3 single crystals with exposed {001} facets achieve high selectivities for H2O2 of >90%, >88%, and >95% in weakly acidic, neutral, and alkaline electrolytes, respectively, and the H2O2 production rate reaches 454 mmol g−1cat h−1 at 0.1 V versus RHE under alkaline conditions. In an anion exchange membrane fuel cell, a maximum H2O2 production of 546.8 mmol L−1 with a high Faradaic efficiency of 80.5% is achieved. Thus, this work details a low‐cost catalyst feasible for H2O2 synthesis, and highlights the feasibility of theoretical catalyst design for practical applications. [ABSTRACT FROM AUTHOR]

Jarosite method is most widely employed to remove iron through the zinc hydrometallurgical process, and ammonium jarosite sediment is produced. The low-temperature thermal decomposition of the ammonium jarosite sediment is desirable to recover natural resources and protect the environment. Herein, we aimed to study the influence of troilite addition on thermal decomposition of hydrothermally synthesized ammonium jarosite. The ammonium jarosite gets decomposed at 300 °C and results in a hematite crystal phase. The hematite, pyrite and magnetite phases have been observed at 400 °C. Furthermore, the hematite and magnetite are present as major phases and pyrrhotite phase has been detected as the minor phase at 500 °C. In addition, the amount of magnetite and hematite exhibited linear and inverse relationships with heat treatment temperature, respectively, in the temperature range of 500–800 °C. Also, the sulfur has been completely decomposed during the jarosite process after roasting at 500 °C and the estimated activation energy value (Ea) of 503.4 kJ mol−1 has been obtained from ln (v / T p 2) versus 1/Tp plots. Troilite can improve sulfur elimination from ammonium jarosite at low temperature. [ABSTRACT FROM AUTHOR]

It was noticed long time ago that the dielectric permittivity of BaTiO3 single crystals in the rhombohedral phase varies from observation to observation, but the microstructure mechanism behind this phenomenon remained unclear. We show that the variations in susceptibility can be related to the variable domain structure introduced by different pre-treatments at higher temperatures: Electrical depoling at room temperature leads to nano-sized domains and ultrahigh susceptibility in rhombohedral phase, whereas thermal annealing at 450 °C results in micro-sized domains and relatively lower dielectric permittivity. The influence of the pre-treatments on domains evolution is tentatively rationalized with a stress accommodation mechanism. The ultrahigh dielectric permittivity could be ascribed to the by-produced 180°-domain walls in the ultrafine domain structure. [ABSTRACT FROM AUTHOR]

We present studies of magnetic and transport properties of Ge1-x-ySnxMnyTe mixed crystals with chemical compositions 0.083¿x¿0.142 and 0.012¿y¿0.119. The transport characterization measurements were performed at temperatures 4.2<300 K. The results showed feature characteristic for narrow gap semiconductors, e.g., metallic conductivity with pxx¿10-4 ¿ cm and hole concentrations p>1021 cm-3. It was found that the transport properties strongly depend on the chemical composition of the alloy. The magnetic investigations included measurements of linear ¿1 and harmonic ¿2,3 ac susceptibilities as a function of temperature and of the applied magnetic field amplitude and frequency. Qualitative analysis of our experimental data showed that in the studied system, in the investigated composition range, the spin glass order exists at temperatures up to 50 K. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • P-doped α-Fe2O3 nanorods on Ti foil as PEC electrode. • Phosphorous doping led to a shift of the band structure toward more positive potentials. • The optimized electrode achieved a photocurrent of 2.5 mA/cm2 at 100 mW/cm2 illumination. Abstract The realization of an efficient photocatalytic water splitting in the absence of sacrificial agent is an important step to achieve the sustainable production of hydrogen using solar energy. Heterostructure-based photocatalysts are used to mitigate charge recombination, thus leading to the improved photoactivity. In a traditional electrochemical system, it works similarly as the heterostructure of z-scheme type which transports the photoinduced electrons to the cathode. Herein, by using a photo-electrochemical process, the production of oxygen and hydrogen was achieved with improved photocatalytic faradaic efficiency. The oxygen evolution process (OER) was improved upon modifying the hematite with phosphorous. The phosphorous doping led to a shift of the band structure toward more positive potentials, resulting in higher OER rates. The optimized electrode achieved a plateau photocurrent of 2.5 mA/cm2 at 100 mW/cm2 illumination. [ABSTRACT FROM AUTHOR]

Problematic red parent material (PRPM) soils resist redox-induced color changes and development of redoximorphic features, posing a challenge to hydric soil and wetland identification. Previous studies suggested that color change resistance was a function of the mineralogical properties of hematite inherited from soil parent materials, but the underlying cause of the phenomenon has remained uncertain. In this study, several hypotheses (i.e., physical occlusion, Al substitution, and crystal size) were investigated to explore the mechanism of PRPM soil color change resistance. The physical occlusion hypothesis was assessed by comparing Color Change Propensity Index (CCPI) values between size fractions for both PRPM and non-PRPM soils. Persistence of color change resistance (low CCPI) in the finest (clay) fractions of all PRPM soils resulted in removing the physical occlusion hypothesis from consideration. Substitution of Al for Fe in hematite was compared between PRPM and non-PRPM clay fractions by observing X-ray diffraction (XRD) peak shifts. Substitution of Al in hematite remained low for the PRPM samples (mean 0.8 mol%), compared with the non-PRPM (mean 6.8 mol%) suggesting that Al substitution is not the cause of observed color change resistance. Finally, mean hematite crystallite size was evaluated using Scherrer equation calculations. Mean hematite crystallite size in PRPM soils was significantly larger than non-PRPM soils (P = 0.0039), suggesting that color change resistance and the PRPM soil phenomenon are derived from the large size of hematite crystals. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Hematite (α -Fe 2 O 3) is one of the most widely studied materials for the application of water oxidation in the field of renewable energy. In order to push hematite toward maximal efficiency, a better understanding of the intrinsic limitations is essential. In this review, we cover our latest results on identifying and finding ways to overcome bottlenecks by modelling the electrochemical processes in hematite at three regimes: 1. at the bulk, the calculated hole effective mass is unfavorably high and conductivity can be improved through doping and alloying, 2. at the surface, catalysis is slow and involves long-lived surface states, but the catalytic overpotential can be reduced by adding a doping gradient or overlayers without strain, and 3. at the back contact the losses can be improved by selecting a proper metal contact. We provide unique analysis approaches that reveal fundamental understanding of electrochemistry with hematite. These models have made an impact on understanding experimental observations and have influenced subsequent theoretical investigations. [ABSTRACT FROM AUTHOR]

As an n-type semiconductor with a band gap of 1.9–2.2 eV, α-Fe2O3 is widely applied for photo-electrodes, organic pollutant degradation, ion adsorption, gas sensors, etc. Therefore, controlled synthesis of hematite with certain morphology has attracted increasing attention due to the unique properties associated with a specific crystal face. Here, we present a simple hydrothermal method to prepare hematite mesocrystals with novel morphologies. Substituted vicinal diol and alkamine were generated via hydrolysis and aminolysis of glycidyl methacrylate and used as novel capping agents to obtain plate-like and hexagonal bipyramidal mesocrystals, respectively. The effects of capping agents on morphology were investigated and the formation mechanism was discussed. The mainly exposed faces of the plate-like and bipyramid-like mesocrystals were the {001} and {116} planes, respectively. Improvement in the catalytic activity for the photo-Fenton reaction was achieved probably due to the specific exposed crystal faces. [ABSTRACT FROM AUTHOR]

Abstract Due to its poor bulk charge separation efficiency, the photoelectrochemical (PEC) performance of pristine hematite prepared directly from an electrodeposited Fe film is limited. Au-modification of hematite via a simple immersion method improves the PEC performance two-fold to 0.31 mA cm−2. The Au nanoparticles deposited from HAuCl 4 act as plasmonic photosensitizers and electron collectors to improve the light absorption and bulk charge separation efficiency of the photoanode. In addition, the increase in the (110) plane and specific surface area induced by HAuCl 4 enhances the bulk charge separation efficiency. After further modification with Ti, the photocurrent response of the resulting Ti/Au/α-Fe 2 O 3 photoanode improves to 0.51 mA cm−2; this increase is attributed to its increased light absorption, bulk charge separation efficiency (η bulk), and surface charge injection efficiency (η surface). In this work, the effect of Au and Ti on the crystalline structure, morphology and PEC performance of the novel electrodeposited hematite photoanode are investigated by systematical characterization. Highlights • Pristine hematite is prepared directly from an electrodeposited Fe film. • Au nanoparticles act as plasmonic photosensitizers and electron collectors. • HAuCl 4 modification can increase the bulk charge separation efficiency of hematite. • Ti and Au co-modified hematite has excellent PEC performance. [ABSTRACT FROM AUTHOR]

Abstract To address the need for new synthetic methods to prepare novel nanocomposites, here we present a direct route for preparing multi-oxide inorganic composites with specific architecture of nanoparticles decorating nanotubes. Our route involves cycles of impregnation of a metallo-organic precursor of nickel into hematite nanotubes and subsequently thermally decomposing it, that we named IDC. We characterized the nanotubes before and after ten sequential IDC. The obtained material is a composite of NiO nanoparticles grown onto the walls of hematite nanotubes. Hematite nanotubes are morphologic and chemically stable during the entire synthetic process. In the synthetic route tested by us, virtually any metallo-organic precursor/combinations of precursors can be used. Our method can be explored to obtain tailored nanocomposites consisting of nanoparticles with different oxides combinations decorating the walls of nanotubes, with potential use such as in catalysis and biomedicine. Graphical abstract Image 1 Highlights • We present a method to prepare NiO nanoparticles decorating hematite nanotubes. • Nanoparticles grow preferentially on the inner-surface of the nanotubes. • Hematite nanotube is chemical and mechanically stable during the synthetic process. • Virtually any combination of oxides can be obtained using our synthetic method. [ABSTRACT FROM AUTHOR]

The mixing operation and design of agitated vessels for various chemical engineering applications may still represent a challenge due to the complexity of hydrodynamic fields established inside the reaction system. Computational Fluid Dynamics (CFD) is considered a valuable tool for the investigation of the complex turbulent flow field proper of mechanically agitated vessel (MAV). The use of CFD may effectively support the process engineer for the selection of the most proper impeller/vessel geometry and operative conditions to achieve homogeneous and fully turbulent conditions. In this work, experimental tests and CFD simulations were performed to study the Cr(VI) removal efficiency through nano-hematite particles (nHP) in MAV. More in detail, some solutions of Cr(VI) were treated using lab-made nHP, produced by a spinning disk reactor, in labscale agitated vessel and the kinetic of the removal process was experimentally studied varying the reactor/impeller configuration (impeller geometry) and the impeller rotational velocity. The obtained results were interpreted according to a CFD model of the system hydrodynamic field based on the k- turbulent model whereas the kinetic data were fitted to a suitable mass transfer kinetic model. [ABSTRACT FROM AUTHOR]

Oxygen vacancy (VO) engineering is an effective method to tune the photoelectrochemical (PEC) performance, but the influence of VO on photoelectrodes is not well understood. Using hematite as a prototype, we herein report that VO functions in a more complicated way in PEC process than previously reported. Through a comprehensive analysis of the key charge transfer and surface reaction steps in PEC processes on a hematite photoanode, we clarify that VO can facilitate surface electrocatalytic processes while leading to severe interfacial recombination at the semiconductor/electrolyte (S‐E) interface, in addition to the well‐reported improvements in bulk conductivity. The improved bulk conductivity and surface catalysis are beneficial for bulk charge transfer and surface charge consumption while interfacial charge transfer deteriorates because of recombination through VO‐induced trap states at the S‐E interface. [ABSTRACT FROM AUTHOR]

Graphical abstract Ultrathin cobalt-iron phosphate (CoFePi) nanolayers are in-situ decorated on Ti-doped hematite nanoarrays photoanode via spin-coating and annealing process to realize synergistic effects on enhancement of photoelectrochemical (PEC) water oxidation performances. Highlights • Ti-Fe 2 O 3 /CoFePi realized high solar water oxidation performance. • CoFePi nanolayer is in situ formed by spin-coating and annealing. • Ti doping and CoFePi coating play synergistic roles in improving the PEC activity. Abstract Hematite (α-Fe 2 O 3) is one of the most promising photoanode materials for solar-to-hydrogen (STH) energy conversion by photoelectrochemical (PEC) water splitting. However, the practical application of hematite in PEC water splitting is severely hindered by the intrinsically low charge separation efficiency and sluggish water oxidation kinetics. Here, we reported Ti-doped hematite photoanode nanoarrays decorated with cobalt-iron phosphate (CoFePi) ultrathin nanolayers greatly enhanced bulk and surface charge separation efficiency, as well as passivate surface states for promoting the PEC water oxidation activity. The synergistic interactions of CoFePi nanolayers with the Ti-Fe 2 O 3 photoanode yield current densities of 1.75 mA/cm2 and 2.15 mA/cm2 in 0.1 M KOH and 1 M KOH respectively at 1.23 V RHE under AM 1.5 G illumination, which is 2.3 and 3.1 fold higher than bare hematite photoanode, and also even higher than Ti-Fe 2 O 3 and Ti-Fe 2 O 3 coated with cobalt phosphate (CoPi), iron phosphate (FePi), phosphate (Pi), respectively. A low turn-on voltage of 0.68 V RHE and high incident photon-to-electron conversion efficiency of 46.6% (IPCE, 1.23 V RHE , λ = 340 nm) are achieved with the Ti-Fe 2 O 3 /CoFePi photoanode. Collectively, the results demonstrated that the synergistic Ti-Fe 2 O 3 /CoFePi photoanode is promising for PEC water oxidation for hydrogen production. [ABSTRACT FROM AUTHOR]

Samples taken from the human brain (Globus Pallidus) have been investigated by physical techniques such as light microscopy, scanning electron microscopy, transmission electron microscopy, Mössbauer spectroscopy and SQUID magnetometry. SEM-EDX/TEM investigation reveals multielemental composition of hematite andmagnetite nanocrystals with sizes ranging from40nm to 100 nm and hematite microcrystals from 3 µm to 7 µm. Room temperature Mössbauer spectra show quadrupole doublets assigning to hematite and ferrihydrite. SQUID measurements of temperature dependence of the mass magnetic susceptibility between T = 2 - 300 K at DC field B0 = 0.1 T, the field dependence of the mass magnetization taken at the fixed temperature T0 = 2.0 and 4.6 K and the zero-field cooled and field cooled magnetization experiments (ZFCM/FCM) confirm a presence of ferrimagnetic phases such as maghemite and/or magnetite with hysteresis loops surviving until the room temperature. Differences between these measurements from the point of view of iron oxides detected can indicate important processes in human brain and interactions between ferritin as a physiological source of iron and surrounding environment. [ABSTRACT FROM AUTHOR]

The strategic exploration of a synthetic approach to afford pristine theranostic nanoparticles (NPs) endowed with versatile physicochemical properties depends on their structural attributes. Therefore, optimizing their design while preserving the crystallinity will undoubtedly be a key foundational data to resolve and understand their biophysical and therapeutic properties. Herein, we report a facile synthesis of α-Fe 2 O 3 NPs under different experimental conditions via the co-precipitation technique. An optimization method- grey relational analysis coupled adaptive particle swarm optimization (GRA-APSO) and artificial neural network (ANN)-a modeling tool were employed to optimize and predict the relationship between the input parameters (pH, stirring speed, reaction temperature, and calcination temperature) and the response attributes (crystallite size, lattice strain, crystallinity index, bond length, and band gap). X-ray diffraction (XRD) pattern revealed the hematite crystal structure for NPs synthesized under initial (IE) and optimized (OE) experimental conditions. Transmission electron microscopy (TEM) confirmed the hexagonal shape of α-Fe 2 O 3 NPs with particle size averaging at 8.5 and 13.7 nm for OE and IE, respectively. Brunauer–Emmett–Teller (BET) measurements unveiled the mesoscopic structure of the as-synthesized samples with a high specific surface area (160 m2/g) for OE. The magnetic hysteresis analysis displayed the weak-ferromagnetic nature of α-Fe 2 O 3 samples. Pure α-Fe 2 O 3 NPs exhibited high T 2 relaxivity (OE-34.8 and IE-36.4 mM−1s−1). Subsequently, haemocompatibility assays demonstrated excellent compatibility of IE and OE samples toward human RBCs. Moreover, synchronous attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and circular dichroism (CD) measurements proved minimal change in the α-helical content of plasma upon association with α-Fe 2 O 3 NPs. The synergistic outcomes of the present study can promise new avenues for exploring haemocompatible α-Fe 2 O 3 NPs as a novel theranostic nanomedicine for multi-modal imaging and versatile biomedical applications. [Display omitted] • Pristine synthesis of hexagonal α-Fe 2 O 3 NPs using thermolysis-assisted co-precipitation route. • A hybrid of GRA-APSO and ANN was adopted to optimize the synthesis of α-Fe 2 O 3 NPs. • GRA inferred pH as the most influencing parameter over all NPs characteristics. • GRA-APSO depicts globally best synthesis conditions (A4, B4, C4, and D1) compared to the traditional GRA-based approach. • As-synthesized NPs showed excellent haemocompatibility, T 2 -relaxivity, and high specific surface area. [ABSTRACT FROM AUTHOR]