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The effect of a copper chromite (CC) catalyst on the decomposition of ammonium perchlorate (AP) was investigated using thermo gravimetric analysis (TGA) in conjunction with Fourier transform infrared (FTIR) spectroscopy and electron ionization (EI) mass spectrometry (MS) of the evolved gases. To determine the activation energy of AP samples, the Kissinger–Akahira–Sunose iso-conversional method was used, which shed more light on the effect of copper chromite on both the low-temperature decomposition (LTD) and high-temperature decomposition (HTD) stages. The FTIR and mass spectra revealed species O2, N2O, Cl2, NO2, HCl, HNO3, H2O, ClO, HOCl, and m/z equal to 30. Using a CC catalyst, an increment in the species mole fraction was detected in the HTD stage for all the AP samples. After the catalyst was brought closer, especially when it was embedded with AP, significant changes were observed in the LTD stage as well. MS revealed the formation of new species such as HClO4, ClO4, HClO3, and ClO3 when CC is embedded in AP. Additionally, increased ClO2 due to CC enhances the decomposition reactions near the subsurface. C-DTA proves that the effect in LTD is more due to exothermic decomposition reactions. Consequently, this overall increase in species generation leads to greater mass loss during the LTD stage decomposition. The accelerated path of NO2 production for the pellet of mixed ammonium perchlorate and copper chromite, as well as Copper chromite embedded AP in the LTD stage, is attributed to the presence of ClO2 and the oxidation of CC. These findings demonstrate that the presence of CC near AP causes aging, resulting in a decrease in burn rate over time. Understanding these results will aid in building a detailed chemical kinetic mechanism (DCKM) and open new avenues for researchers to use it wisely in the real world. [ABSTRACT FROM AUTHOR]

The first widespread occurrence of rare Na-, Ca-, and Mg,Mn,Fe-bearing phosphate chladniite was observed in meteorite Graves Nunataks (GRA) 12510, which is a primitive achondrite that sits within the winonaite class. Numerous 1–500 μm chladniite grains were found, often on the margins between silicate clasts and the kamacite portions of the large metal veins that permeated through the sample. The largest chladniite grains are associated with merrillite, kamacite, taenite, troilite, albite, forsterite, diopside, and enstatite, with a few tiny chladniite grains and an apatite grain enclosed within merrillite. GRA 12510s average chladniite composition is Na2.7Ca1.25(Mg10.02Mn0.69Fe0.20)Σ10.91(PO4)9. Electron backscattered diffraction (EBSD) patterns indicate varying degrees of nucleation and growth of chladniite grains. Additionally, the first pure Raman spectrum of chladniite is described here, revealing primary ν1 bands at 954, 974, and especially 984 cm–1. The co-occurrence and close association of merrillite, apatite, chladniite, and P-bearing metallic phases within GRA 12510 suggests that the fO2 of IW-2 to IW-4 is an intrinsic property of the precursor chondritic material, and the phosphatephosphide reaction may have buffered the final winonaite and IAB iron meteorite phase assemblages. Altogether, chladniite appears to form alongside other phosphates, with their chemistries reflecting the diverse environment of their formation. Meteoritic chladniite likely formed through subsolidus oxidation of schreibersite, scavenging Na from albite, Ca from diopside, Mg from enstatite/forsterite, Fe from kamacite/taenite, and Mn from alabandite/chromite when available. A P0-P5+ redox-buffered environment also has implications for thermometry and fast cooling rates, although more experiments are needed to extrapolate powder reaction rates to those of larger crystals. Furthermore, phosphidephosphate buffered experiments may aid in investigating equilibrium chemistry at fO2 values between IW-2 and IW-4, which have been challenging to explore experimentally due to the limited availability of solid metal-metal oxide buffers between IW (Fe-FeO) and IW-5 (Cr-Cr2O3) at temperatures and pressures relevant to planetary interiors. Future investigations of phosphide-phosphate redox-buffered genesis at fO2 values between IW-2 and IW-4 have important implications for primitive meteorite constituents (e.g., CAI values), partially differentiated planetesimals and planets, including Mercury and core formation on Earth. [ABSTRACT FROM AUTHOR]

This paper describes secondary crystallized melt inclusions trapped in magnesiochromite of lherzolite xenolith from the V. Grib kimberlite pipe (Arkhangelsk diamondiferous province). It is shown that the inclusions are microportions of melt related to magmatism, which was further formed this pipe. Daughter minerals assemblage of inclusions in magnesiochromite contain Na‒K‒Ca-, Na‒Mg-, Ca‒Mg-, Mg-, and Ca-bearing carbonates; Na–Mg carbonates with additional PO , Cl–, and SO anions; chlorides; sulfate; phosphate; and silicate. The mineral assemblage of daughter phases, the amount of carbonates (77 vol %) and silicates (tetraferriphlogopite) (15 vol %) and Ca : Na : K ratios within the inclusions indicate that this melt was an alkali-enriched carbonate liquid with a low content of SiO2 (≤6 wt %) and H2O (≤0.6 wt %). As is known, serpentine in kimberlites is a major H2O-bearing mineral, but the problem of water sources during serpentinization of kimberlites and an actual H2O content in kimberlite melts is a controversial issue. The absence of serpentine and the low H2O content (≤0.6 wt %) of the studied melt inclusions in comparison with those of kimberlites of the V. Grib kimberlite pipe (10‒14 wt %) indicate the key role of external fluids during serpentinization of these kimberlites. [ABSTRACT FROM AUTHOR]

Chromite ore processing residue (COPR), which is created during the chromite preparation process of chromite compounds, is considered hazardous waste because it contains chromium trivalent and chromium hexavalent. Recently, the harmless disposal of COPR has received a lot of research interest. COPR is a type of resource attributable to its abundant content of chromium, iron, aluminum, etc. This article starts from the main sources, properties, and pollution characteristics of COPR. It summarizes the methods and approaches used by scholars in recent years to handle COPR: chemical reduction, dry detoxification, pyrolysis, mineralization, solidification/stabilization, biotechnology, electrochemical methods, and resource utilization, achieving harmless treatment of COPR. Among them, research on resource utilization stands out, not only improving resource utilization efficiency but also reducing environmental pollution. This provides new ideas and directions for our future treatment of COPR. [ABSTRACT FROM AUTHOR]

An editorial focuses on the discovery and significance of layered chromite mineralization within mafic-ultramafic rocks in the Gayahe area of the East Kunlun Orogenic Belt, Northwestern China. It highlights the identification of chromitite layers with high ore grades, marking a significant find in an area previously lacking economically valuable chromite deposits.

The podiform chromitites in the Luobusha ophiolite have been thought to experience a very deep formation, but the maximum depth is still an open issue. Here, we have investigated the structural stability of natural magnesiochromite using the synchrotron-based powder X-ray diffraction and diamond anvil cells up to 48.6 GPa and 2 450 K. The results have shown that spinel-type magnesiochromite first decomposes into corundum-type 'Cr2O3' + B1-type 'MgO' at 11–14 GPa and 1 250–1 450 K, then modified ludwigite (mLd)-type 'Mg2Cr2O5' + corundum-type 'Cr2O3' at 14.3–20.5 GPa and 1 300–2 000 K, and finally CaTi2O4-type phase at 24.5 GPa. During the quenching procession from high-temperature-pressure conditions, the mLd-type phase appeared again and was kept at ambient conditions. We also obtained the isothermal equation states of spinel-type and CaTi2O4-type phases, revealing the composition effect on their elasticities. Based on the updated results, we propose chromitites could not experience pressure exceeding ∼14.3 GPa (approximate maximum depth ∼400 km) in the subduction-recycling genesis model. [ABSTRACT FROM AUTHOR]

The multi-stage leaching of chromite in HCl-Na2CrO4, system has been studied, and the leaching kinetics of main metal elements in chromite has been discussed. The results show that under the optimal conditions of particle size of 45~75 µm, oxidizing agent Na2CrO4, dosage of 0.6 times of theoretical dosage, reaction time of 5 h, reaction temperature of 453.15 K, ball to material mass ratio of 1/1, stirring speed of 30 r/min, liquid volume to solid mass ratio of 4 mL/1 g, the three-stage cyclic leaching is carried out, the leaching rates of Cr, Fe, Al and Mg can reach 91.98%, 94.54%, 76.62% and 78.03 %, respectively. The acid leaching reaction of chromite is controlled by interfacial chemical reaction. The apparent activation energies of Cr, Fe, Al and Mg are 45.80, 40.43, 42.08 and 43.54 kJ/mol, respectively. In the range of 373.15~473.15 K, and the leaching effect is good. [ABSTRACT FROM AUTHOR]

HTPB (hydroxyl‐terminated polybutadiene) is a well‐established binder in the composite solid propellant owing to its excellent compatibility with ammonium perchlorate (AP) and aluminium (Al) particles in giving rise to optimal ballistic and mechanical properties. Efforts are being made to improve the ballistic properties further, such as specific impulse. One way of increasing the specific impulse is to hydrogenate HTPB, which decreases the molecular mass of the combustion product gases. This paper is a summary of efforts in synthesizing hydrogenated HTPB (HHTPB) using copper chromite (CC) as a catalyst. A novel synthesis methodology is developed for HHTPB using a temperature‐programmed batch reactor with a variable speed stirrer and an instrumentation system to maintain the desired liquid reactant temperature. A process cycle is developed that includes addition sequence and reaction time. The product is analyzed using 1H‐NMR and FTIR to estimate the degree of hydrogenation and the geometrical isomers respectively. The estimated apparent equilibrium rate constants from the degree of hydrogenation values are respectively 74 and 2034 L/(mol MPa) for non‐catalyzed and catalyzed systems, indicating the effectiveness of the catalyst. This is also substantiated by the reduction in Gibbs free energy (ΔG), to an extent of 4.48 kJ/mol. Thermogravimetry examination indicates that the decomposition temperature of HHTPB produced by the catalytic method is marginally higher compared to HTPB. DSC curves indicate that the decomposition enthalpy of HHTPB is higher than that of HTPB. In summary, this paper proposed and validated a novel method in the preparation of HHTPB using copper chromite. [ABSTRACT FROM AUTHOR]

In the present work, host and cerium-doped Zinc chromite nanoparticles (NPs) are synthesized by solution combustion method using Aloe Vera gel extract. The synthesized samples are characterized with different techniques. The Bragg reflections of ZnCr2O4:Ce (0–9 mol%) NPs confirms the formation of pure spinel cubic structure. The crystallite size, lattice strain, crystallinity, dislocation density were determined using Scherrer's and W–H plot method. The direct energy band gap was tuned from 3 to 2.8 eV. The direct energy band gap was found to decrease with increase in the dopant concentration. The cytotoxic properties of ZnCr2O4:Ce (0–9 mol%) NPs were tested against breast cancer cell (MDA-MB-231) and compared with that of Cisplatin, a standard drug. From the MTT assay, it is confirmed that the MDA-MB-231 cells are more sensitive to doped ZnCr2O4: Ce (1–9 mol%) NPs than the host matrix as well as with the standard drug Cisplatin. Compared to other dopant concentrations, the efficiency of ZnCr2O4: Ce (9 mol%) is more than that of the cisplatin and hence this can be used as the substitute for the cisplatin. [ABSTRACT FROM AUTHOR]

Nodular chromite ore deposits are found in ophiolites and crop out in structures interpreted as former dykes. Most of them are transposed parallel to the plastic foliation of the host peridotite. Many studies have been conducted in order to decipher the origin and evolution of nodular chromite but the outstanding lack of consensus paves the way for an integrated field, geochemical and microstructural approach to be carried out. We sampled the well-characterized Maqsad chromitite dyke that crops out at the top of the mantle–crust dunitic transition zone in the Oman ophiolite and that was not affected by transposition. The spectacular variations in nodule size and texture and their distribution within the dyke have been perfectly preserved which is a rather unique situation. We selected about 40 nodules representative of the shapes and size variability of this ore deposit. Nodules have been classified in three categories: Type-1 nodules are large skeletal chromite grains associated with amphibole and olivine filling their former porosity; Type-3 nodules have a central nucleus of chromite/silicate surrounded by a mantle of close-packed chromite grains. Their shape is best described as almond-like, and they may reach 3 cm in length; Type-2 includes all of the intermediate nodules shapes and sizes between type-1 and type-3 varieties. Electron Probe MicroAnalyser (EPMA) transects and maps show that mineral chemical variations in type-1 nodules and in the nuclei of type-2 and type-3 nodules record out of equilibrium crystal growth. They exhibit high XCr and relatively low-TiO2 and likely resulted from transient interactions between hydrothermal fluids and basaltic melts. Contrary to type-1 and nuclei, the mantles of type-2 and -3 nodules have lower Cr2O3 contents, decreasing toward the nodule edges. They are richer in TiO2 than type-1 nodules but concentration patterns of this element along edge to edge transects are quite variable. The chromite mantles of type-2 and -3 are best understood as the fractional crystallization products of a parent melt of type-1 nodules in different pFluids and/or redox conditions. The analysis of the distribution of the misorientation axis between the skeletal grains and the adjacent chromite grains in the mantle (N  = 222 in 28 nodules) revealed a clustering around a [111] axis across the whole range of misorientation angles. Accordingly, we suggest that the growth of the Maqsad nodules is achieved by accretion of finer euhedral chromite grains onto a skeletal chromite grain by juxtaposition of their flat crystal facets. Combined EDS-EBSD mapping together with EPMA transects revealed that a ~1-mm-thick rim of high XCr, displaying a homothetic shape to its corresponding nuclei, is a common feature in the mantle when the nodule sizes exceed about 1 cm. We interpret this observation as the result of the accretion of grains with higher XCr compositions during the nodule construction. Overall, our new study of the Maqsad nodular chromitite highlights the peculiar and transient conditions needed to give rise to the textural and chemical complexity that is preserved in these enigmatic rocks. [ABSTRACT FROM AUTHOR]

Alternative fuels derived from vegetable oil have great potential as diesel fuel replacements in the transportation and manufacturing sectors. The aim of this study is to use cobalt chromite nanoparticles as a fuel additive with biodiesel in engine and to experimentally investigate the influence of injection pressure on combustion parameters. As an addition, cobalt chromite nanoparticles are used with biodiesel made from kapok oil, which is blended with mineral diesel at a ratio of 20:80. The engine is operated at various injection pressures (200–260 bar) and with an 80 ppm nanoparticle concentration. The results have shown that the increased injection pressure caused by the use of nanoparticles enhances engine combustion properties, such as the peak pressure and the rate of heat release. The main purpose of this research was to investigate the effects of a CoCr2O4 + KME20 mix on a CI engine, with the hope of improving engine performance characteristics. This investigation examines the effects of varying test fuel injection pressures. The increased injection pressure of CoCr2O4 + KME20 resulted in better performance and combustion. The 240‐bar IP was shown to be superior to lower IPs because of its greater penetration length and more uniform formation. The IP rating of 240 bar represented a significant improvement over competing products with respect to emission controls. In addition to reducing our reliance on fossil fuels, this also prevents harmful chemicals from being released into the air. [ABSTRACT FROM AUTHOR]

This work details the study conducted on composite solid propellants with activated copper chromite (ACR) as burn catalyst for its burn rate change with time due to the interaction of ammonium perchlorate (AP) with ACR. One of the hypotheses cited for burn rate reduction is the conversion of chromite in ACR to chromate by an electrolytic reaction with moisture in the presence of ammonium perchlorate. This hypothesis was studied by a design of experiments which includes blending ammonium perchlorate and ACR, Aluminum and ACR, stand alone ACR in raw material stage and the blends storage with time. The effect of moisture in AP is addressed by comparing undried and dried AP in the blends. The blended raw materials were characterized by Thermo-gravimetric analysis, Particle Size Distribution, surface area measurement, Scanning Electron Microscopy and chromium estimation. Results show that the conversion of chromium from chromite to chromate is very minimum in the presence of AP. Propellant samples are prepared with these blends at different time intervals to understand viscosity, mechanical properties and burn rate behavior with raw material storage. Experimental results show burn rate shows an opposite trend of increase with blend storage of 6 months. A plausible explanation for this observation is presented in the paper correlating the experimental conditions.

The oxidation behavior and induration characteristics of typical ferrous spinel concentrates including low-Mg (OM) and high-Mg magnetite (MM), titanomagnetite (TM), and chromite (CM) was investigated. An insight into the thermodynamics, phase and microstructure transformation, element migration mechanism of the oxidation of different types of ferrous spinel was taken using thermogravimetry–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD), scanning electron microscopy-energy and energy dispersive X-ray spectroscopy (SEM–EDS), and X-ray photoelectron spectroscopy (XPS) at temperatures ranging from room temperature to 1273 K. The results indicate that OM, MM, and TM start to oxidize and form hematite at a similar temperature of approximately 673 K, while oxidation of CM begins at a higher temperature of around 873 K. Among them, OM exhibits superior oxidizability. For MM, the incorporation of magnesium ions into the octahedral crystal sites of magnetite tends to stabilize the crystal structure of magnetite and presents some negative influence on its oxidizability. TM has more complex chemical and phase compositions, dominantly consisting of titanomagnetite (Fe2.75Ti0.25O4) with good oxidizability, whereas the presence of a small quantity of ilmenite (FeTiO3) reduces the final oxidation degree. Compared with OM, MM, and TM, CM exhibits inferior oxidizability due to its complex chemical compositions and phase transformation. The induration characteristics of pellets prepared by four kinds of spinel also shows significant differences. Under the conditions of 1553 K, the induration characteristics are best with OM, followed by CM and TM, while MM exhibits the best induration performance at 1473 K. [ABSTRACT FROM AUTHOR]

Occurrence of "ferrian chromites" have earlier been reported from the Mesoarchean chromite deposits in the Boula-Nuasahi ultramafic complex (BNUC) of India. We have investigated the chromitite bodies in the southern part of the BNUC (i.e., Bangur area) with respect to the mode of occurrence, petrography, chemistry and structure of the chromite types. Although morphologically five varieties of chromite ore were found, chemically only three types of chromite can be distinguished based on EPMA analysis. These are: 1) Type I: magnesiochromite [high Cr2O3 (57–65 wt.%), low iron (FeO: 13–17 wt.%), XFe3+: < 0.1 apfu]; 2) Type II: ferrian chromite [moderate Cr2O3 (43–53 wt.%), high iron (FeO: 27–30 wt.%), XFe3+: 0.1 to 0.5 apfu]; and 3) Type III: ferrichromite [low Cr2O3 (19–29 wt.%), very high iron (FeO: 55–67 wt.%), XFe3+: 0.5 to 1.0 apfu]. Stoichiometrically calculated Fe2O3 content is very high in some grains (maximum 47 wt.%). Geochemical discrimination diagrams for the Type I pristine magnesiochromite suggest a dominantly boninitic parental magma. Trace element data obtained from LA-ICP-MS indicate that the Type II chromite has formed from a more evolved magma and is richer in trace elements such as V, Mn, Co, Cu, Pb, Ga, and Nb whereas the Type III ferrichromite shows unusually high Ti and erratic high concentrations of trace elements. Alterations in chromite is noticed in two different thermal regimes: 1) 100–200 °C related to serpentinization of dunite and peridotite rocks where chromite grains show an unaltered core, an intermediate ferrian chromite rim and an outer magnetite rim; 2) 500–600 °C where the entire chromite grain is converted to ferrichromite which can be linked to later intrusion of the Bangur gabbro. While HR-TEM study reveals that all three chromite-types have face-centered cubic structure, Raman spectroscopy indicates that there is a gradual transition of the structural state from normal spinel structure (Type I) through Type II to a fully inverse spinel structure in case of ferrichromite. [ABSTRACT FROM AUTHOR]

The Archean–Proterozoic transition in the Earth's history is marked by significant changes in the mantle dynamics and temperature regimes. A notable consequence is the disappearance of Al-depleted komatiites in the Late Archean and an almost complete absence of Archean-typical peridotitic komatiites since the Proterozoic. This work presents a study of the 2.41 Ga komatiitic basalts from the Vetrenyi Belt, dating back to the early Proterozoic. Unique data on the compositions of olivine and chromite, as well as on the crystallization temperatures based on Al-in-olivine geothermometry for komatiitic basalts from the Vetrenyi Belt are provided. The temperatures of the earliest stages of crystallization were approximately 1240 ± 25°C, which indicates the occurrence of water in the melt and is consistent with measured water contents of 0.4 ± 0.2 wt % H2O in the melt inclusions. However, during crystallization, the komatiitic basalt melt underwent degassing, resulting in mass crystallization of the system and a temperature rise by ~20°C due to the release of the latent heat of crystallization. The degassing of water from the melt suggests crystallization under surface conditions. [ABSTRACT FROM AUTHOR]

Featured Application: The potential applications of this work include the reconstruction of artificial bacterial consortia that are able to resist and/or reduce chromium and are robust over time for a bioremediation application at the Quimica Central site (Mexico). Industrial residues with high concentrations of hexavalent chromium [Cr(VI)], characterized by an alkaline pH (between 9 and 13) and high salinity (around 100 psu), were used as a source for extremophilic chromium-resistant and -reducing microorganisms. An investigation of biodiversity through MiSeq showed the presence of 20 bacterial classes, with Bacilli (47%), Negativicutes (15%), Bacteriodia (8%), Gammaproteobacteria (7%) and Clostridia (5%) being the most abundant. The bioprospection allowed the cultivation of 87 heterotrophic bacterial colonies and 17 bacterial isolates at the end of the isolation, and screening procedures were obtained. The isolates were related to Cellulosimicrobium aquatile, C. funkei, Acinetobacter radioresistens, Staphylococcus equorum, S. epidermis, Brachybacterium paraconglometratum, Glutamicibacter creatinolyticus, Pseudomonas songnenensis, Microbacterium algeriense and Pantoea eucalypti, most of them being resistant to Cr(VI). Resistances of up to 400 m g. L − 1 of chromate were obtained for four related strains (QReMLB55A, QRePRA55, QReMLB33A and QReMLB44C). The C. aquatile strain QReMLB55A and the P. songnenensis strain QReMLB33A were exposed to K 2 C r 2 O 7 (200 m g. L − 1 ) under optimal conditions, diminishing 94% and 24% of the Cr(VI) in 6 days, respectively. These strains exhibited a high potential for chromium remediation biotechnologies. [ABSTRACT FROM AUTHOR]

Background: This study focuses on the synthesis of magnesium‐doped dysprosium chromite via a sol‐gel method. The investigation aims to understand the morphological and structural properties of the synthesized nanochromates. Key techniques employed include x‐ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. Aims: The primary aim is to analyze the structural characteristics of MgxDy1−xCr2O4 nanoparticles with varying Mg doping concentrations (ranging from 0.2 to 0.8). Special attention is given to the crystallinity of the synthesized materials, with the goal of assessing the reliability and reproducibility of the sol‐gel synthesis method. Methods: XRD analysis is employed to identify major diffraction peaks associated with the chromate nanoparticles, providing insights into their crystallinity. SEM imaging allows for the examination of the morphological features of the synthesized materials. Additionally, Raman spectroscopy aids in further understanding the structural properties of the nanochromates. Results: The XRD analysis reveals average crystallite sizes for MgxDy1−xCr2O4 nanoparticles at different Mg doping concentrations. Notably, an improvement in crystalline quality is observed with an increase in Mg doping from 0.2 to 0.8, indicating a high level of control achieved in the synthesis process. Cyclic Voltammetry (CV) experiments conducted using a 1M KOH electrolyte and varying scan rates (3 mV/s to 50 mV/s) demonstrate enhanced electrochemical performance of the synthesized nanoparticles. Conclusion: The study concludes that the sol‐gel synthesis method effectively produces MgxDy1−xCr2O4 nanoparticles with controlled morphological and structural properties. The observed improvement in crystalline quality with increasing Mg doping concentration suggests potential applications in fields such as photo‐catalysis, where enhanced crystallinity correlates with improved photo‐catalytic potential for visible light absorption. [ABSTRACT FROM AUTHOR]

Here, we present a petrographic and microanalytical study of microinclusions in chromite from podiform chromitites hosted by the Sartohay ophiolitic mélange in west Junggar, northwestern China, to investigate the parental magma evolution and chromitite genesis. These silicate inclusions comprise olivine, enstatite, diopside, amphibole, and Na-phlogopite. Their morphological characteristics suggest that most inclusions crystallized directly from the captured melt, with a few anhydrous inclusions (olivines and pyroxenes) as solid silicates trapped during the chromite crystallization. Equilibrium pressure–temperature conditions of coexisting enstatite–diopside inclusions are 8.0–21.6 kbar, and 874–1048 °C. The high Na2O and TiO2 contents of hydrous minerals indicate that the parental magma of chromitites was hydrous and enriched in Mg, Na, Ca, and Ti. The calculated Al2O3 content and FeO/MgO ratio of the parental melts in equilibrium with chromite showed MORB affinity. However, the TiO2 values of parental melts, TiO2 contents of chromite, and estimated fO2 values for chromitites (1.3–2.0 log units above the FMQ buffer) evoked parental MORB-like tholeiitic melts. The composition of olivine inclusion was determined, and it was revealed that the primary melts of the Sartohay podiform chromitites had MgO contents of ~22.7 wt %. This aligns with the observed high magnesian signature in mineral inclusions (Fo = 96–98 in olivine, Mg# = 0.91–0.97 in diopside, and Mg# = 0.92–0.97 in enstatite). We propose that Sartohay podiform chromitites initially formed through the mixing/mingling of primary hydrous Mg-rich melt and the evolved MORB-like melt derived from the melt–peridotite reaction in the upper mantle. In this process, the continuous crystallization of chromite captured micro-silicate mineral inclusions, finally leading to the formation of the Sartohay podiform chromitites. [ABSTRACT FROM AUTHOR]

Secondary ion mass spectrometry (SIMS) measurements of δ18O in nine chromite (Mg, Fe)(Al, Cr, Fe)2O4 samples (Cr# = 0.58–0.79, Mg# = 0.39–0.72) from chromitites and harzburgite have confirmed their intra‐ and inter‐grain isotopic homogeneity, making them suitable reference materials for in situ analysis. The SIMS measurements of the oxygen isotopic composition of these chromites exhibit a range of instrumental mass fractionation (IMF) as a function of the end‐member compositions of the chromite, particularly the magnetite (FeOFe2O3) and spinel (MgAl2O4) components. Functional relationships have been developed to correct for IMF over the compositional range XMag = 0.01 to 0.05, and XSpl = 0.14 to 0.22. We conclude that, to be accurate, SIMS measurements of δ18O must be combined with electron probe microanalyses of the individual analysed spots. [ABSTRACT FROM AUTHOR]

The production processes in open cast mining activities are primarily associated with rock blasting operations, which trigger blast-induced ground vibrations causing significant damages to the surrounding surface structures. Regular monitoring of the ground vibration levels serves as crucial input to the regulatory authorities and policymakers for designing and developing an efficient blasting system to control the extent of damages caused by the same. Thus, the present study aimed to monitor the field practiced blasting events in active open cast chromite mines in the Sukinda valley of the Indian state of Odisha to develop a new site-specific model for predicting blast-induced ground vibration. The investigation has proposed a new ground vibration prediction model using multivariate statistical analysis. The validation of the model-predicted results against the field recorded data suggests the reliable performance of the proposed model having R2, RMSE, MAE and MAPE values of 0.8, 2.8, 1.925 and 0.5, respectively. Whereas, the comparison of the field recorded data with the universally employed USBM model exhibits R2, RMSE, MAE and MAPE values of 0.28, 8.13, 4.72 and 0.68, respectively suggesting the better predictive capabilities of the proposed model. Hence, the present study suggests the applicability of a newly proposed predictive model for blast-induced ground vibration in the chromite mining region of Sukinda valley. Finally, one such design parameter, namely the maximum explosive charge per delay, has been optimized for different distances by limiting the PPV value within the legislative limits as per guidelines formulated by the regulatory authority of India. [ABSTRACT FROM AUTHOR]

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The use of gravity concentrators involves several challenges, such as determination of the liberation sizes of the minerals, selection of appropriate particle sizes for the applied concentration method, and the severity of the beneficiation of fines.In this study, the effects of fully liberated (artificial mixtures of magnetite and quartz) and non-liberated particles (chromite ore collected from a chromite processing plant) on various gravity concentration equipment were investigated as a function of particle size considering recoveries, separation efficiencies, and grades of products. A series of tests were conducted on shaking tables, spiral concentrators, and a Falcon concentrator with different design features under various operating conditions. Finally, the separation efficiencies were correlated with the settling rates of the particles.The test results confirmed a certain trend in the separation efficiency as a function of particle size for each condition. The separation efficiency initially increased with increasing particle size, peaked, and eventually decreased with increasing particle size. The maximum separation efficiency attained was 90% for 141 µm particles in the shaking table and 54% for 245 µm particles in the Falcon concentrator, both of which were used to treat the artificial feed. In the spiral concentrator, which treated chromite ore as feed, the maximum separation efficiency attained was 82% for 178 µm particles.This experimental study provides data to identify the concentration behavior of particles by investigating possible separation mechanisms. Consequently, it provides an understanding of the relationships between particle size and separation efficiency in terms of settling rates, especially in spiral concentrators. [ABSTRACT FROM AUTHOR]

The work reports on the results of the mineralogical and petrographic study of the Borodino meteorite (H5). For the first time, meteorite minerals were described and their chemical compositions were given. The following were found in the Borodino meteorite: olivine (Fa 18.16 ± 1.15), Ca-poor pyroxene – (clino)enstatite (En 81.37 ± 1.73, Wo 1.18 ± 0.31), Ca-rich pyroxene – augite (En 57.23 ± 1.57, Wo 39.38 ± 2.68), diopside (En 51, Wo 45), pigeonite (En 69, Wo 6), plagioclases – oligoclase (An 12.16 ± 1.24, Or 5.68 ± 2.12), andesine (An 48.23 ± 1.84, Or 1.23 ± 0.12), anorthoclase (An 0, Or 36) and sanidine (An 0, Or 40.00 ± 1.1), and poorly crystallized glasses of the feldspathic composition, merrillite and chromespinelide. The obtained data made it possible to estimate a degree of terrestrial weathering of the meteorite as W0 and the stage of impact metamorphism (S1-2), which suggests good preservation of the meteorite material. The composition of olivine and Cr-spinel, determined by the Electron Probe Microanalysis, was used to estimate the peak temperature of thermal metamorphism at 720°C, which falls within the temperature range (670–740°C) typical of chondrites of a petrological type 5. The presence of Ca-rich pyroxenes, large grains of Ca–Na–Mg phosphates and chromite-pigeonite aggregates in the meteorite matrix indicate the prolonged heating of the material. [ABSTRACT FROM AUTHOR]

Detrital chromite is currently accumulating in the wave-influenced gravel-dominated shoreface of eastern Port au Port Bay of western Newfoundland adjacent to the mouth of Fox Island River. Chromium (Cr) concentrations of up to 7485 ppm occur in modern cross-bedded shallow marine gravel and pebbly sand facies sourced from rapidly eroding coastal cliffs cut in a lateglacial and early postglacial fan delta and raised beach facies. These sediments fill a broad coastal embayment and were deposited by a glacially influenced Fox Island River during a phase of low relative sea level following final deglaciation of the Newfoundland Ice Cap between approximately 13 700 years B.P. (ybp) and 9500 ybp. Since then, coastal outcrops of these raised sediments have undergone rapid erosion in response to ongoing postglacial sea level rise outpacing the rate of crustal recovery. Geochemical analysis of 1149 sediment samples across the entire Fox Island River watershed identifies relatively low Cr concentrations (maximum 1860 ppm) in glacial and fluvial sediments, including those areas adjacent to chromite-bearing rocks of the Bay of Islands Ophiolite Complex. Conversely, uplifted lateglacial shallow marine gravels and associated raised beach/nearshore deposits along the coast show elevated Cr concentrations up to 5400 ppm, highlighting the importance of marine concentration of glacially derived sediment during deglaciation. At the present day, chromite-bearing lateglacial sediment is being reworked and transported southwards by shore-parallel littoral currents resulting in reconcentration of Cr within a nearshore placer about 8 km long and 2 km wide, though the deposit may be more extensive offshore where it is likely covered by transgressive marine muds. The glacial and postglacial history of the Port au Port Bay area was widely replicated in other areas of ultrabasic rock along the western coast of Newfoundland and the results of this investigation may aid the search for other nearshore glacially influenced marine placers. [ABSTRACT FROM AUTHOR]

The aim of the following work was to determine the possibility of using barley malt as a binder in moulding sands technology. The moulding sands prepared on the basis of three kinds of sands, i.e. quartz, olivine and chromite sands were analyzed. In order to determine the properties of moulding sands, typical determinations were made, i.e. moisture content, flowability, permeability, strength properties and abrasion wear. The obtained results indicate that it is possible to use barley malt as an independent binder for masses made of quartz, olivine and chromite sands. [ABSTRACT FROM AUTHOR]

Oxygen crystallising was obtained from olivine, chromite separates from host rock samples, and gabbro from ultramafic cumulates, harzburgite, and dunite samples collected from tectonites of the Guleman ophiolites. The study includes the oxygen isotope compositions from the Guleman ophiolite and the evolutionary scenarios of geochemical and isotopic signatures. The olivine and chromitite δ18Oolivine/chromite and δ18Omelt values point out these minerals and melt isotopic compositions similar to mantle values and rich, heavy stable isotopes. The highest δ18Ochromite isotopic composition values indicate that as the heavy isotope in the melt increases, the concentration in the mineral increases. Excluding a dunite sample, the values of the δ18Owhole rock of the dunite and pyroxenite samples are similar to mantle values. The gabbro samples have higher δ18Owhole rock values than the two harzburgites. Hereby, the chromite formations are the later fractional crystallisation products than olivine and dunites due to the lowering of δ18O. The lower oxygen isotopic composition in studied samples than the normal mantle values, and these values point out subducted hydrothermally alteration. The higher δ18O isotopic compositions could be explained by serpentinization on the ocean floor at low temperatures. [ABSTRACT FROM AUTHOR]

Minerals consisting of the platinum-group elements iridium, osmium and ruthenium (IPGE) are widely dispersed in alluvial deposits derived from ultramafic igneous complexes originating in ophiolite belts. Rock types, such as cumulate dunite–pyroxenite–harzburgite, and their serpentinite derivatives are especially fertile sources of IPGE minerals, which are colloquially termed 'osmiridium'. IPGE minerals have been recorded from five localities in Victoria—beach sands at Waratah Bay, and stream concentrates from Turtons Creek, Stockyard Creek and Horseshoe Creek in South Gippsland. A grain of IPGE was recently found in a gully near the Dolodrook River further north. These occurrences are all poorly documented by comparison with the northwest Tasmanian deposits, and only Waratah Bay has provided enough material to enable full characterisation. Microprobe data show that all four minerals currently defined in the Os–Ru–Ir system occur at Waratah Bay, including rutheniridosmine. Gold and chromite are also present in the alluvial samples from Waratah Bay and Turtons Creek. Attempts to correlate compositions of alluvial chromite with those from likely proximal serpentinite source rocks proved to be inconclusive due mainly to inadequate representative sampling. However, the chromite compositions are broadly characteristic of those found in the early Paleozoic ultramafic ophiolite complexes in northwestern Tasmania, in which IPGE minerals and chromite are abundant. Regional aeromagnetic trends across Bass Strait suggest that the Victorian IPGE occurrences represent disaggregated and metamorphosed extensions of the Tasmanian sequences. IPGE minerals (alloys of platinum-group elements osmium, iridium, and ruthenium) have been recorded from five Victorian placer deposits, but only those in beach sands at Waratah Bay, in southern Victoria, have been preserved for study. The primary sources for most occurrences can be tracked to nearby Cambrian mafic–ultramafic rocks ('greenstones') sequences. The IPGE minerals range in composition across all currently defined species in the Os–Ir–Ru system and are typical of occurrences in Tasmania and elsewhere in the world. Aeromagnetic trends across Bass Strait suggest a linkage between the Victorian and Tasmanian occurrences. Compositions of chromite in the serpentinites cannot be correlated with those in associated placer deposits. [ABSTRACT FROM AUTHOR]

Olivine from the dunite of the Guli pluton crystallized from olivine–melanephelinite magma at temperatures above 1260°C according to the melt inclusion study. The melts were enriched with volatile components (S, CO2, F, H2O, slightly Cl) and contained high amount of incompatible elements. In addition, olivine hosts sporadic inclusions of picrite-basalt composition, which are close to picrite–meimechite melts preserved in chromite from dunite according to literature data. This suggests the influx of picrite–meimechite melts and their mixing with melanephelinite magma during the formation of dunites in the magma chamber. Based on the indicator ratios of incompatible elements, these melts and melanephelinite magma had different sources, which were located in undepleted mantle at different depths and derived through different degree of partial melting. [ABSTRACT FROM AUTHOR]

The CB (Bencubbin‐like) metal‐rich carbonaceous chondrites are subdivided into the CBa and CBb subgroups. The CBa chondrites are composed predominantly of ~cm‐sized skeletal olivine chondrules and unzoned Fe,Ni‐metal ± troilite nodules. The CBb chondrites are finer grained than the CBas and consist of chemically zoned and unzoned Fe,Ni‐metal grains, Fe,Ni‐metal ± troilite nodules, cryptocrystalline and skeletal olivine chondrules, and rare refractory inclusions. Both subgroups contain exceptionally rare porphyritic chondrules and no interchondrule fine‐grained matrix, and are interpreted as the products of a gas–melt impact plume formed by a high‐velocity collision between differentiated planetesimals about 4562 Ma. The anomalous metal‐rich carbonaceous chondrites, Fountain Hills and Sierra Gorda 013 (SG 013), have bulk oxygen isotopic compositions similar to those of other CBs but contain coarse‐grained igneous clasts/porphyritic chondrule‐like objects composed of olivine, low‐Ca‐pyroxene, and minor plagioclase and high‐Ca pyroxene as well as barred olivine and skeletal olivine chondrules. Cryptocrystalline chondrules, zoned Fe,Ni‐metal grains, and interchondrule fine‐grained matrix are absent. In SG 013, Fe,Ni‐metal (~80 vol%) occurs as several mm‐sized nodules; magnesiochromite (Mg‐chromite) is accessory; daubréelite and schreibersite are minor; troilite is absent. In Fountain Hills, Fe,Ni‐metal (~25 vol%) is dispersed between chondrules and silicate clasts; chromite and sulfides are absent. In addition to a dominant chondritic lithology, SG 013 contains a chondrule‐free lithology composed of Fe,Ni‐metal nodules (~25 vol%), coarse‐grained olivine and low‐Ca pyroxene, interstitial high‐Ca pyroxene and anorthitic plagioclase, and Mg‐chromite. Here, we report on oxygen isotopic compositions of olivine, low‐Ca pyroxene, and ±Mg‐chromite in Fountain Hills and both lithologies of SG 013 measured in situ using an ion microprobe. Oxygen isotope compositions of olivine, low‐Ca pyroxene, and Mg‐chromite in these meteorites are similar to those of magnesian non‐porphyritic chondrules in CBa and CBb chondrites: on a three‐isotope oxygen diagram (δ17O vs. δ18O), they plot close to a slope‐1 (primitive chondrule mineral) line and have a very narrow range of Δ17O (=δ17O–0.52 × δ18O) values, −2.5 ± 0.9‰ (avr ± 2SD). No isotopically distinct relict grains have been identified in porphyritic chondrule‐like objects. We suggest that magnesian non‐porphyritic (barred olivine, skeletal olivine, cryptocrystalline) chondrules in the CBas, CBbs, and porphyritic chondrule‐like objects in SG 013 and Fountain Hills formed in different zones of the CB impact plume characterized by variable pressure, temperature, cooling rates, and redox conditions. The achondritic lithology in SG 013 represents fragments of one of the colliding bodies and therefore one of the CB chondrule precursors. Fountain Hills was subsequently modified by impact melting; Fe,Ni‐metal and sulfides were partially lost during this process. [ABSTRACT FROM AUTHOR]

At high PT parameters of cumulates of ultramafic–mafic intrusions and low oxygen fugacity (below QFM buffer), Pt in the form of a carbonyl complex is dissolved in a CO2-bearing fluid. The high solubility of Pt chloride in brines with NaCl, which is related to the formation of low-sulfide deposits of platinum group elements, is attained only at high oxygen fugacity (above the QFM buffer). It is suggested that native platinum at low oxygen fugacity in low-Н2О СО–СО2 (Н2О) fluid can also transit into a cation-soluble form due to the reaction of chloration. The experimental data are provided for the interaction of NaCl with magnetite and chromite (accessory minerals of ultramafic–mafic intrusions) at Р = 200 MPa, Т = 950°С, and fO2 3 and FeCl2 equilibrium provides a high chlorine fugacity (fCl2), which is only 3–4 orders of magnitude lower than fCl2 in Pt–PtCl2 equilibrium and 2.5–3.0 orders of magnitude higher than in 1 M HCl aqueous fluid at the same Р‒Т–fO2 parameters. [ABSTRACT FROM AUTHOR]

Silica sand is an essential raw material for glass production. The specification of silica sand for each type of glass is the most important point, such as chemical purity, grain size, grain shape, and their impurities. Some of the impurities in the sand can be eliminated by processing yet some cannot be avoided. This paper indicates that as an impurity in the sand, chromite minerals dissolve in glass. 0.200 mm and 0.250 mm grain size chromite minerals were observed grain size change at 1350 °C − 1400 °C − 1450 °C. With increasing in temperature, the rate of size change in the grain diameter increased. Because of the chemical composition of chromite mineral, with increasing temperature, first of all, aluminum and magnesium content start to dissolve in soda lime silicate glass. Then, chromium content transforms into chromium oxide. The transformation rate depends on the mineral composition as well as the temperature and the residence time in the furnace. This paper concerns the chemical composition of the chromite by scanning electron microscopy equipped with energy dispersive spectrometer, the compositions of the raw material analyzed with X-ray fluorescence spectroscopy, inductively coupled plasma optical emission spectrometer and chromite characteristics analyzed by Raman Spectroscopy methods. [ABSTRACT FROM AUTHOR]

This study investigated the recovery of nickel from tailings (0.2% Ni) obtained in a chromite beneficiation plant using H2SO4 leaching followed by oxalic acid precipitation. The tailings were characterized using mineral liberation analysis. Ni was found as Fe-Ni, Fe-Ni-Co sulfide minerals, which were encapsulated in serpentine, olivine, pyroxene and clinochlore. Liberated fine chromite minerals benefited from magnetic separation followed by Falcon concentrator. A chromite product with a grade > 37% was obtained. The effect of leaching conditions including acid concentration, temperature, time and solid-to-liquid ratio on the leaching behavior of Ni was investigated based on the Taguchi approach. It was possible to extract Ni with a rate of > 98% from the tailings using the following conditions: H2SO4 concentration of 3 M, solid-to-liquid ratio of 1:20 and ambient temperature for 2 h. Finally, Ni was precipitated as an oxalate form with a precipitation rate of 72%. It is believed that implementing additional purification methods like solvent extraction may be essential to obtain a high-purity nickel product from the leach solution of oxalate precipitate. Experimental results indicate that the tailings used in this study are a good alternative as Ni resource in the near future. [ABSTRACT FROM AUTHOR]

Extraterrestrial chrome spinel and chromite extracted from the sedimentary rock record are relicts from coarse micrometeorites and rarely meteorites. They are studied to reconstruct the paleoflux of meteorites to the Earth and the collisional history of the asteroid belt. Minor element concentrations of Ti and V, and oxygen isotopic compositions of these relict minerals were used to classify the meteorite type they stem from, and thus to determine the relative meteorite group abundances through time. While coarse sediment‐dispersed extraterrestrial chrome‐spinel (SEC) grains from ordinary chondrites dominate through the studied time windows in the Phanerozoic, there are exceptions: We have shown that ~467 Ma ago, 1 Ma before the breakup of the L chondrite parent body (LCPB), more than half of the largest (>63 μm diameter) grains were achondritic and originated from differentiated asteroids in contrast to ordinary chondrites which dominated the meteorite flux throughout most of the past 500 Ma. Here, we present a new data set of oxygen isotopic compositions and elemental compositions of 136 grains of a smaller size fraction (32–63 μm) in ~467 Ma old pre‐LCPB limestone from the Lynna River section in western Russia, that was previously studied by elemental analysis. Our study constitutes the most comprehensive oxygen isotopic data set of sediment‐dispersed extraterrestrial chrome spinel to date. We also introduce a Raman spectroscopy‐based method to identify SEC grains and distinguish them from terrestrial chrome spinel with ~97% reliability. We calibrated the Raman method with the established approach using titanium and vanadium concentrations and oxygen isotopic compositions. We find that ordinary chondrites are approximately three times more abundant in the 32–63 μm fraction than achondrites. While abundances of achondrites compared to ordinary chondrites are lower in the 32–63 μm size fraction than in the >63 μm one, achondrites are approximately three times more abundant in the 32–62 μm fraction than they are in the present flux. We find that the sources of SEC grains vary for different grain sizes, mainly as a result of parent body thermal metamorphism. We conclude that the meteorite flux composition ~467 Ma ago ~1 Ma before the breakup of the LCPB was fundamentally different from today and from other time windows studied in the Phanerozoic, but that in contrast to the large size fraction ordinary chondrites dominated the flux in the small size fraction. The high abundance of ordinary chondrites in the studied samples is consistent with the findings based on coarse extraterrestrial chrome‐spinel from other time windows. [ABSTRACT FROM AUTHOR]

We integrate multidisciplinary observations to provide a regional-scale synthesis of river drainage reconfiguration in Southland (New Zealand) between the Miocene and the Holocene. Distributions of sedimentary clasts, including alluvial gold, garnets and chromite, are combined with freshwater fish genetics, surface geomorphology, and basement geology to constrain river drainage directions and interconnections through time. River evolution in much of the South Island has been dominated by localised tectonic uplift linked to distant Alpine Fault tectonism. In the southeast, the rise of ranges between Central Otago and Southland severed initial long-distance southward drainage and gold transport and isolated fish species. Plio-Pleistocene range uplift caused the recycling of older alluvial gold deposits into the new Southland river systems. The most significant Southland drainage reorientations have occurred through the Pleistocene, in parallel with similar processes in Central Otago. In particular, the Pomahaka River has evolved geomorphologically from a Southland-linked catchment to become a major tributary of the Clutha catchment, with associated biological evolution of distinctive endemic freshwater fish. [ABSTRACT FROM AUTHOR]

Organosilicon materials generate copious amounts of Si-containing solid waste during production, leading to severe environmental pollution and substantial resource squandering. In pursuit of the resource utilization of Si-containing solid waste, this study conducted experimental research on the direct alloying of molten steel through the silicothermic self-reduction of chromite ore using Si-containing solid waste as a reducing agent. Additionally, thermodynamic analysis was performed, employing the thermodynamic calculation software FactSage 8.2 (Thermfact Ltd., Montreal, QC, Canada and GTT-Technologies, Aachen, Germany), to examine the equilibrium reactions of the silicothermic reduction of chromite ore and the variations in the thermodynamic equilibrium compositions of slag and metal phases. The results indicate a reduction sequence for the reducible components in chromite ore as Fe2O3 → Cr2O3. The introduction of CaO and Al2O3 into the silicothermic self-reduction compacts altered the forms of Fe and Cr oxides in equilibrium, significantly reducing the standard Gibbs free energy (ΔG0) of the silicothermic reduction reaction. The initial slag melting point decreased from 1700 °C without the addition of CaO and Al2O3 to 1500 °C with the addition of CaO and Al2O3. Correspondingly, the slag viscosity at 1600 °C decreased from 134.1 Pa·s without CaO and Al2O3 addition to 1.81 Pa·s with CaO and Al2O3 addition. The addition of CaO and Al2O3 accelerated the reduction of Cr oxide in chromite ore and enhanced the recovery of Cr, consistent with the thermodynamic calculation results. In the process of steelmaking through the direct alloying of chromite ore silicothermic self-reduction compacts, the final recovery rate of Cr increased from 86.4% without CaO and Al2O3 addition to 95.4% with CaO and Al2O3 addition. [ABSTRACT FROM AUTHOR]

Improving the application of nanomaterials has always been a research hotspot in the field of energetic materials (EMs) due to their obvious catalytic effect on the EMs, especially the uniformly dispersed nanomaterials. However, few studies have reported the dispersion of nanomaterials. In this study, the dispersity and mixing uniformity of nano-CuCr2O4 was evaluated based on the difference of solid UV light absorption between the nano-catalytic materials and EMs. The nano-CuCr2O4/ultrafine AP composites with different dispersity of nano-CuCr2O4 were prepared by manual grinding and mechanical grinding with different grinding strength and griding time. And then, the absorbance of different samples at 212 nm was obtained by solid UV testing due to the high repeatability of the absorbance at 210–214 nm for three parallel experiments, and the dispersity of different samples was calculated through the established difference equation. Furthermore, the samples were characterized by XRD, IR, SEM, EDS, DSC and TG-MS, which confirmed that different mixing methods did not change the structure of the samples (XRD and IR), and the mixing uniformity improved with the increase of grinding strength and grinding time (SEM and EDS). The scientificity and feasibility of the difference equation were further verified by DSC. The dispersity of nano-CuCr2O4 exhibits a positive intrinsic relationship with its catalytic performance, and the uniformly dispersed nano-CuCr2O4 significantly reduces the thermal decomposition temperature of ultrafine AP from 367.7 to 338.8 °C. The TG-MS patterns show that the dispersed nano-CuCr2O4 advanced the thermal decomposition process of ultrafine AP by about 700 s, especially in the high temperature decomposition stage, and the more concentrated energy release characteristic is beneficial to further enhance the energy performance of AP-based propellants. The above conclusions show that the evaluation method of dispersity based on solid UV curves could provide new ideas for the dispersity characterization of nano-catalytic materials in EMs, which is expected to be widely used in the field of EMs. [ABSTRACT FROM AUTHOR]

Abstract—The Maksyutov eclogite–blueschist Complex is characterized by a complicated fold-and-thrust structure that has been formed during the Late Devonian collision between the subducting Baltica margin (East European Plate) and the Magnitogorsk island arc. Eclogites are the most studied rocks of the Complex; their formation and exhumation are usually associated with the collisional stage of the orogen development. At the same time, the origin of meta-ultramafic rocks, which together with eclogites form sheets and boudins within metasedimentary rocks (schists and quartzites), still remains unknown. This paper presents the results of the first detailed petrological study of meta-ultramafic rocks represented by antigorite−chlorite and magnesite−antigorite meta-harzburgites, and chlorite−antigorite metaorthopyroxenite. Mineral compositions and textural relationships between minerals in the meta-harzburgites indicate at least two stages of rock transformations. Minerals of the early mineral paragenesis (first stage)—olivine, accessory chromite, and low-fluorine Ti-clinohumite – have a metamorphic genesis; ultrahigh-pressure (UHP) conditions of their formation are discussed. Partial replacement of olivine by orthopyroxene-bearing parageneses with Cr−Al antigorite and/or high-chromium chlorite is established for the second stage. The phase equilibria modeling using the Perple_X software package demonstrates that formation of antigorite−orthopyroxene paragenesis was associated with Si−Al metasomatism at: T ~ 630°С, P ~ 2 GPa, log ~ −0.6, log ~ −2.5. It is important to note that the mineral paragenesis is highly sensitive to : a slight decrease in log relative to the above value would lead to the growth of olivine with antigorite, and an increase would lead to the growth of orthopyroxene. The latter may explain the formation of meta-orthopyroxenites, which are widely distributed among the meta-ultramafic rocks of the Maksyutov Complex. Similar calculations performed for the range of = 0.01–0.05 in H2O–CO2 fluid showed the replacement of silicate minerals by magnesite under the established thermodynamic conditions. Carbonation and Si−Al metasomatism are specific features of high-pressure transformations of meta-ultramafic rocks, which have not been established in the associated eclogites, quartzites, and shales. Such selective fluid influence on different rock types is interpreted as a result of their different tectono-metamorphic evolution: meta-ultramafic rocks are fragments of the suprasubduction mantle, which were tectonically juxtoposed with the rocks of the subducting plate (eclogites and metasedimentary rocks). [ABSTRACT FROM AUTHOR]

In this work, Ag0.5Cr2.5O4 nanochromite is fabricated utilizing a simple process (flash technique) at various annealing temperatures (room and 900 °C). The particle sizes of the materials under study were shown to be in the nanoscale range by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Fourier transform infrared (FTIR) analysis was performed to verify the fabrication of the examined nanosamples and evaluate the bands behavior. The tetrahedral A-site (622.9 cm−1 for room temperature, 630.6 cm−1 for 900 °C) and the octahedral B-site (557.3 cm−1 for room temperature, 563.1 cm−1 for 900 °C) were the two prominent bands measured by FTIR analysis. The elastic characteristics of Ag0.5Cr2.5O4 nanoparticles were examined using FTIR measurements, revealing that the interatomic bonding of the atoms at 900 °C is higher than at room temperature. In addition, the elastic characteristics may be understood by analyzing the transverse and longitudinal velocities. Both Gram-positive and Gram-negative bacteria were effectively inhibited by the samples evaluated for antibacterial properties; however, neither sample showed any antifungal activity. Therefore, it is highly suggested that the investigated samples could be used in different applications, particularly biological ones. [ABSTRACT FROM AUTHOR]

The change of iron grade in the leaching residue and the leaching kinetics under normal pressure and pressure were examined. The pressure leaching of nickel and cobalt from a high iron and low grade laterite nickel ore in Indonesia with sulfuric acid was studied. The results show that under the conditions of acid/ore ratio of 260 kg/t, leaching temperature of 250 °C (corresponding to water vapor pressure of 4. 0 MPa), liquid volume/solid mass ratio of 3/1, stirring speed of 300 r/min, particle size of 100 mesh and reaction time of 1 h, the leaching rates of nickel, cobalt and iron are 98. 1 %, 98. 3% and 4. 7%, respectively, and the iron grade can reach 51. 3%. The leaching processes of nickel and cobalt under pressure and atmospheric pressure are in line with the shrinkage kernel model of interfacial chemical reaction control, and the activation energies of the reactions are 116 kj/mol and 91 kj/mol under pressure, respectively, and the activation energies of the reaction under atmospheric pressure are 41 kj/mol and 53 kj/mol, respectively. The leaching is mainly goethite under normal pressure, and chromite, magnetite and other mineral phases under high pressure. [ABSTRACT FROM AUTHOR]

Using the pyrolyzing polymer‐salt compositions method yttrium orthochromite (space group Pnma) was synthesized. A value of oxygen nonstoichiometry δ=.056 and a band gap of 1.64 eV were obtained. With the experimentally determined structural parameters as a basis, we performed ab initio simulations to investigate the defect structure of YCrO3±δ. We studied the presence of interstitial oxygen in the YCrO3 at oxygen nonstoichiometry close to the experimental value and vacancies at the same concentration. Formation energies were estimated for interstitial oxygen atoms and compared with those of oxygen vacancies in the cases neutral and charged supercells. The computational results demonstrate that interstitial oxygen is energetically more favorable than the formation of oxygen vacancies. We considered various configurations of the interstitial oxygen atom within the YCrO3 crystal lattice and identified two fundamentally distinct types. An analysis of projected densities of states and charge distributions was performed for these configurations. The results indicate that direct intercalation of oxygen atoms is energetically more favorable than the formation of a peroxide species when the Fermi level is close to the conduction band minimum. [ABSTRACT FROM AUTHOR]

Large crystals of titanium nitride (mineral osbornite) from metallurgical slag were studied by EMPA, XRD and Raman spectroscopy. The sample was collected at metallurgical dump in Kladno in the early 1970s and briefly described by Žáček and Ondruš (2003). The sample has a size of about 40 x 30 x 30 mm and is notable for its high density and conspicuous cubes of copper-like red to gold colour with metallic lustre (Fig. 1-2). The material consists of dominant gehlenite (~ 65% of the sample, all vol. %), osbornite (~ 20%), metallic iron (~ 8%), oldhamite (~ 5%), spinel (~1%) and anorthite (~ 1%), see Fig 3. All these phases were analyzed with the Cameca SX100 electron microprobe, and osbornite by Raman spectroscopy. Gehlenite and osbornite were also confirmed by XRD (Žáček -- Ondruš 2003). Gehlenite contains a low concentration of MgO (0.8-1.1 wt.%) and traces of Na2O (0.06-0.16 wt.%) and Fe2O3 (0.4 wt.%). Aggregates of metallic iron embedded in gehlenite contain low titanium (up to 0.06 wt.% Ti) and elevated phosphorus concentrations (0.53-1.59 wt.% P), whereas tiny iron inclusions embedded in osbornite are richer in titanium (1.31 wt.%) and poorer in P (0.37 wt.%). Oldhamite, a cubic CaS, forms rounded inclusions 20-150 μm in size embedded in massive gehlenite. It is characterized by elevated concentration of Mn (2.7 wt.%) and low Fe (0.3 wt.%) and Mg (0.15 wt.%). Spinel has empirical formula Mg0.98Al1.99O4, and plagioclase is pure anorthite. Compositional data of osbornite are given in Table 1, those of associated minerals in Table 2 and 3. Osbornite forms aggregates of cubic crystals in a small slag cavity. Individual and crystal aggregates, usually up to 5 mm in size, are embedded in massive gehlenite. The largest aggregate of osbornite crystals reaching about 15 x 8 mm in size (Fig. 2). Osbornite contains 76.30-78.21 wt.% Ti, 21.31-23.82 wt.% N, and 0.02-0.46 wt. % Fe and displays stoichiometric composition Ti0.97-1.03N0.96-1.03 with only 0.005 apfu Fe (see Table 1). Lattice parameter is: a = 4.2536(3) Å (Žáček -- Ondruš 2003). The Raman spectrum of osbornite (Fig. 4) measured on the unpolished surface of cubic crystals showed the following vibrational bands: 1498, 201, 226, 271, 316, 345, 395, 439, 520, 559, 609, 649, 765, 836, and 1075 (all in cm-1). Raman spectra of TiN and other Ti nitrides have been studied by a number of authors (e.g. Spengler et al. 1978, Subramanian et al. 2011, Judek et al. 2021). The spectra can be divided into acoustic (A) and optical (O) part and further to the combination A + O, 2A and 2O modes (Spengler et al. 1978; see Fig. 4). In addition to the vibrational bands typical of osbornite (201, 271, 316, 345, 395, 520, 559, 649, 765, 836 and 1075 cm-1), there are also vibrational bands corresponding to rutile and to the TiON phase (149, 226, 395, 439, 520, 609 and 649 cm-1, Spengler et al. 1978, Judek et al. 2021). The position of the vibrational band of osbornite at 201 cm-1 indicates a stoichiometric Ti : N ratio of 1 : 1, which is in agreement with the results of WDS chemical analysis (Spengler et al. 1978). The detected presence of TiON and TiO2 phases on the surface of osbornite crystals indicates oxidation of osbornite, probably at elevated temperatures. A similar effect was achieved during laboratory annealing of TiN layers at temperatures above 250 °C (Glaser et al. 2007) or above 500 °C (Chen et al. 2005). Osbornite had long been considered as an exclusively extraterrestrial mineral (Ramdohr 1973, Casanova 1992), and only a few natural terrestrial localities have been identified so far. It was first detected in heavy mineral concentrates from volcanic breccias at the contact of the Priazov Massif with the Donbas Basin in Ukraine (Tataritsev et al. 1987). Osbornite along with other minerals occurs here as inclusions of up to 20 μm in size embedded in corundum. Another occurrence from Ukraine, reported by Yatsenko et al. (2017, 2021), is also from inclusions in corundum originating from kimberlite in the Khmelnytsky region. A verified occurrence of osbornite is in the Luobasa chromite deposit in Lhoca Prefecture, Tibet, where it forms, together with coesite and qingsongite (BN), microscopic inclusions in ultrahigh-pressure mantle xenoliths enclosed in ophiolite (Dobrzhinetskaya et al. 2009). Most recently, osbornite has been found in pyrometamorphosed rocks of the Hatrurim Complex in Israel. The Hatrurim Complex consists of rocks with a predominance of larnite, spurrite and gehlenite. Osbornite forms here inclusions of up to 40 μm in size embedded in a paralava dominated by gehlenite and is accompanied by a number of other exotic minerals, especially phosphides (Galuskin et al. 2022). Studied osbornite from metallurgical slag resembles osbornite from Ca-rich paralavas by its paragenesis and conditions of formation under reducing conditions at atmospheric pressure. [ABSTRACT FROM AUTHOR]

A humite group mineral, Ti-bearing hydroxylclinohumite, referred to natural compact water-containing magnesian silicates (DHMS phases) was found for the first time in podiform chromitites. The finding was made in chrome ores of the Paity Plateau located in the northern part of the Voikar–Synya ultramafic massif of the Polar Urals. Chromitites deposited in the dunite body located at the contact of apoharzburgite amphibole–olivine–antigorite and amphibole–enstatite–olivine metamorphic rocks containing nonserpentinized harzburgite relics. According to the optical data and chemical composition, this mineral belongs to Ti-bearing hydroxylclinohumite, because it contains TiO2 (up to 5.64 wt %) and is absolutely devoid of F. The OH-group in the mineral is confirmed by the Raman spectrum generally corresponding to the hydroxylclinohumite standard. According to the geothermometry results, this mineral was formed in chromitites of the Polar Urals at a temperature of 668–740°C and, probably, a pressure of 20–25 kbar. Hence, chromite ores were generated (recrystallized) under high-pressure conditions. In other words, the chromite ore occurrences in the northern part of the Voikar–Synya massif developed, apparently, in the suprasubduction environment. [ABSTRACT FROM AUTHOR]

An ultrasonic irradiation-assisted green approach was developed for the facile preparation of xanthenones and chromenopyrimidinediones using copper chromite nanoparticles (CuCr2O4 NPs) as an efficient heterogeneous catalyst. The desired products were formed by a one-pot three-component reaction of aromatic aldehydes, 3,4-methylenedioxyphenol, and C-H activated acidic compounds including dimedone and 1,3-dimethylbarbituric acid. Various aromatic aldehydes extended the scope and generality of the presented route. Using water as green and nonvolatile solvent and ultrasonic irradiation as an innocuous energy resource, high yields of products within a short reaction time increase the current protocol's economic and environmental superiority. Compounds were evaluated for their antimicrobial inhibition against some selected Gram-positive and Gram-negative bacterial strains. The results showed that the growth of Gram-positive bacteria was highly inhibited by only compounds 5a, 5b, 6d, and 6e, while the rest of test compounds show moderate effects on microbial growth. All test compounds, aside compound 6d, did not display any remarkable growth inhibitory activity against the Gram-negative bacteria. The present study introduces a ground work for the application prospects of ultrasound-based novel, green, and sustainable method for the preparation of some xanthenone and chromenopyrimidinedione derivatives. Copper chromite nanoparticles have appeared as efficacious and reusable catalyst for ultrasonic irradiation treatment in the synthesis of the above-mentioned compounds. The present study establishes that several synthesized compounds show good antimicrobial effects against the standard Gram-positive bacteria Staphylococcus aureus and Streptococcus pyogenes and Gram-negative bacterium Serratia marescens. Due to the best of our knowledge for these previously known compounds, this study is the first report of their promising antimicrobial activity. [ABSTRACT FROM AUTHOR]

Significantly different peak pressure–temperature (P–T) conditions (18–26 kbar and 630–760°C versus 29–37 kbar and 750–940°C) have previously been published for eclogite and related metabasites from the south‐eastern flank of the Pohorje Mountains in Slovenia. These rocks can show a bimodal distribution of chromium in the rock‐forming minerals, particularly garnet, the role of which in their metamorphic evolution is unclear. Therefore, we studied an eclogite and a related rock with clinopyroxene containing only 17 mol% jadeite + acmite (sample 18Ca35a). KαCr intensity maps of garnet particularly in sample 18Ca35a show a sharp irregular boundary between the core (Gt1) and the mantle (Gt2). Gt1 of millimetre‐sized garnet in this rock is nearly Cr‐free and unzoned, whereas Gt2 is of different composition (0.22 wt.% Cr2O3) and slightly zoned. Nearly Cr‐free amphibole, (clino)zoisite, kyanite and staurolite inclusions are present in Gt1. The matrix consists of garnet and Cr‐bearing clinopyroxene, (clino)zoisite and amphibole. Thermodynamic modelling suggests peak P–T conditions of 22.5 ± 2 kbar at 710 ± 25°C (Gt1) and 23 ± 2 kbar at 700 ± 25°C (Gt2) in both samples. We interpret these findings to suggest that olivine‐ and hornblende‐bearing gabbros with some chromite experienced early metamorphism in the eclogite facies, when Gt1 formed. The rock was subsequently exhumed and cooled leading to significant garnet corrosion. A second stage of metamorphism, recognized by mappable Cr contents in garnet, led to the growth of Gt2 and other Cr‐bearing minerals at the expense of chromite relics, which survived stage I. The peak P–T conditions of stage II are compatible with those previously derived by same authors and support the view that probably no ultrahigh‐pressure eclogite exists in the Pohorje Mountains. We relate the two metamorphic events to the Cretaceous and Palaeogene high‐pressure events recently reported from micaschists of the Pohorje Mountains. [ABSTRACT FROM AUTHOR]

In this context, first-time cobalt chromite nanoparticles (CoCr2O4 NPs) were synthesized using honey as a natural precursor through a bio-derived approach. The benefits of this protocol are an easy workup using inexpensive precursors. The textural characteristics of the as-synthesized CoCr2O4 NPs were examined via XRD, FTIR, UV, FESEM, EDX mapping, and VSM studies. Microscopic pictures revealed a cuboidal topology with a mean size of 31.69 nm for greenly produced CoCr2O4 NPs. Furthermore, CoCr2O4 NPs were applied as a heterogeneous catalyst for the facile and one-step formation of 5-aryl-[1,2,4]-triazolidine-3-thiones. The proposed approach offers several admirable benefits, such as straightforwardness, benign reaction systems, shorter reaction time, facile workup, and excellent yield. Also, the as-prepared nanocatalyst was reused (up to 5 cycles) without reducing the significant catalytic performance. Therefore, the present study discloses that synthesizing CoCr2O4 NPs by a facile green approach and assessing robust catalytic performance might benefit nanochemistry research, offering new avenues for organic transformations. [ABSTRACT FROM AUTHOR]

Lacustrine strata-bound magnesite deposits associated with Alpine-type ultramafic rocks are hydrothermal in origin. The magnesite ores of the Kamado deposit are unconformably underlain by mid-Jurassic marine carbonate and ultramafic rocks of the Bangong-Nujiang ophiolite suite and are in fault contact with hanging wall rocks composed of siliceous sinter. Three types of cryptocrystalline magnesite ores can be identified in Kamado: (1) strata-bound massive magnesites, representing the main ore type in the upper part; (2) banded ores in the lower part; and (3) some vein and stockwork ore in the ultramafic wall rocks. Integrated scanning electron microscopy, C–O isotope analysis, and geochemical analyses were carried out on the Kamado deposit. The results indicate that: (1) the orebody is composed of magnesite, with accessory minerals of aragonite, opal, and chromite; (2) the siliceous sinter and relatively high B (32.0–68.1 ppm) and Li (14.7–23.4 ppm) contents of the magnesite ores reflect long-term spring activity in Kamado; (3) the light carbon (δ13CV-PDB: −4.7 ± 0.3‰ to −4.1 ± 0.6‰) and oxygen isotopic compositions (δ18OV-SMOW: +12.3 ± 0.3 to +16.3 ± 0.1‰) of the stockwork ores in the foot wall rocks indicated that the carbon in fractures in the ultramafic rocks is from a mixture of marine carbonate and oxidized organic-rich sedimentary rocks, reflecting a typical "Kraubath-type" magnesite deposit; and (4) the relatively heavy carbon isotopic (δ13CV-PDB: +8.7 ± 0.4‰ to +8.8 ± 0.3‰) composition of the banded magnesite ores in the lower segment may have formed from heavy CO2 generated by anaerobic fermentation in the lakebed. Additionally, the carbon isotopic (δ13CV-PDB: +7.3 ± 0.3‰ to +7.7 ± 0.7‰) composition of the massive magnesite ores in the upper segment indicates a decline in the participation of anaerobic fermentation. As this economically valuable deposit is of the strata-bound massive ore type, Kamado can be classified as a lacustrine hydrothermal-sedimentary magnesite deposit, formed by continuous spring activities under salt lakes on the Tibetan Plateau, with the Mg mainly being contributed by nearby ultramafic rocks and the carbon mainly being sourced from atmosphere-lake water exchange, with minor amounts from marine carbonate strata. [ABSTRACT FROM AUTHOR]