Search Results (1,098)

This work presents a study on the optical and mechanical degradation of parabolic trough collector absorber coatings produced through the spray coating application technique of in-house developed paint. The main aim of this investigation is to prepare, cure, load, and analyze the absorber coating on the substrate under conditions that mimic the on-field thermal properties. This research incorporates predicted isothermal and cyclic loads for parabolic trough systems as stresses. Biweekly inspections of loaded, identical samples monitored the degradation process. We further used the cascade of data from optical, oxide-thickening, crack length, and pull-off force measurements in mathematical modelling to predict the service life of the parabolic trough collector. The results collected and used in modelling suggested that cyclic load in combination with iso-thermal load is responsible for coating fatigue, influencing the solar absorber optical values and resulting in lower energy transformation efficiency. Finally, easy-to-apply coatings made out of spinel-structured black pigment and durable binder could serve as a low-cost absorber coating replacement for a new generation of parabolic trough collectors, making it possible to harvest solar energy to provide medium-temperature heat to decarbonize future food, tobacco, and paint production industrial processes. Full article

Corrosion of the molten salts Na₂SO₄ and NaCl has become one of the major factors in the failure of steel components in boilers and engines. In this study, CoNiCrAlY cobalt-based cladding layers with different NiCr-Cr₃C₂ ratios were prepared by microbeam plasma cladding technology. The influence of the NiCr-Cr₃C₂ content on the microstructure, mechanical properties, and molten salt corrosion resistance of CoNiCrAlY was investigated. The CoNiCrAlY with a 25 wt.% NiCr-Cr₃C₂ (NC25) cladding layer possessed the highest microhardness (348.2 HV_0.3) and the smallest coefficient of friction (0.4751), exhibiting great overall mechanical properties. The generation of protective oxides Cr₂O₃, Al₂O₃, and spinel phase (Ni,Co)Cr₂O₄ is promoted by the addition of 25 wt.% NiCr-Cr₃C₂, which significantly reduces the corrosion of the cladding layer, and this effect is much more obvious at 950 °C than that at 750 °C. Furthermore, its corrosion mechanism was clarified. From the findings emerge a viable solution for the design and development of new high-temperature corrosion-resistant coatings. Full article

The composition of Cr-spinels from rocks of the Monchegorsk layered complex (2.5 Ga) basically corresponds to the evolutionary trend that is typical for layered mafic–ultramafic intrusions (late magmatic phases contain Cr-spinels enriched in Fe and depleted in Mg, Cr, and Al). Cr-spinels within the Dunite Body of the Sopcha massif are almost identical to those within the Dunite Block rocks and are close to those from harzburgite of the NKT massif. Cr-spinels within the satellite bodies of the Ore Layer 330 are shown to have zonal structure, which confirms their origin from a new portion of melt, which may have been injected with several pulses. The composition of accessory Cr-spinels may indicate that the layered complex of rocks of the South Sopcha massif was formed from the most evolved portion of magmatic melt (linked with the Monchetundra intrusion), and its vein complex may be considered the one formed at the final stages of the magmatic system evolution. The composition of Cr-spinels from the Pentlandite Gorge mafic–ultramafic rocks may indicate that they are fragments of the NKT massif and not of the Monchetundra massif, as it was believed earlier. Full article

Corrosion of steel is an issue that cannot be ignored in contemporary society. Due to large-scale corrosion, it is urgent to develop a surface treatment process that enhances the corrosion resistance of steel, allowing for application in various scenarios as needed. This study aims to investigate a novel surface treatment process to extend the service life of corroded Q235 steel, reduce its sensitivity to corrosion, and enable its use in multiple environments. This study employs the sol-gel method, using manganese nitrate solutions of varying concentrations to treat the surface of Q235 steel after different electrolysis times. The optimal conditions for precursor preparation were found to be a Mn²⁺ concentration of 0.1 mol/L and an electrolysis time of 2 h. Electrochemical tests using NaCl solutions of different concentrations revealed a significant reduction in the corrosion current for the composite coating based on Q235 steel treated with this method in NaCl solutions with wt.% = 1, 2, 3, 4, 5. Furthermore, the resistance to corrosion was strongest in the NaCl solution with a concentration of 1 wt.% where the corrosion current decreased from 24.8 µA/cm² to 6.79 µA/cm². Additionally, the coating was found to be diffusion-controlled in the early stages of the corrosion process and charge transfer-controlled in the later stages. The MnFe₂O₄ spinel coating demonstrated the greatest enhancement in corrosion resistance in the wt.% = 1 NaCl solution. Full article

Spinel-type InGaMgO₄ with a = 8.56615(3) Å was prepared by treating layered YbFe₂O₄-type InGaMgO₄ at 6 GPa and 1473 K. DFT calculation and Rietveld analysis of synchrotron X-ray powder diffraction data revealed the inverse spinel structure with In³⁺:Ga³⁺/Mg²⁺ = 0.726:0.274 in the tetrahedral site and 0.137:0.863 in the octahedral site. InGaMgO₄ spinel is an insulator with an experimental band gap of 2.80 eV, and the attempt at hole doping by post-annealing in a reducing atmosphere to introduce an oxygen defect was unsuccessful. This is the first report of the bulk synthesis of AB₂O₄ compounds with both YbFe₂O₄ and spinel polymorphs. Full article

The characterization and evolution of corrosion products deposited on/around MnSs, a typical kind of inclusive particle embedded in AISI 304 stainless steel, was analyzed using a quasi-in-situ method in a 3.5 wt.% NaCl solution. On/around the MnS inclusion, a corrosion product layer with spinel Fe_3−xCr_xO₄ as the main component was formed, with a thickness of several hundred nanometers. Below the layer, there was a cavity layer in which part of the MnS remained, forming secondary pitting along the MnS/matrix boundary. The mechanism of corrosion product deposition and evolution accompanied by MnS dissolution, as well as the characteristics of the corrosion products, are discussed. Full article

In this paper, we introduce an environmentally friendly approach to recycle used batteries and recover highly valuable manganese-based cathode materials. This study demonstrates the feasibility of fast plasma pyrolysis to recover LiMn₂O₄ electrode materials (e.g., lithium manganese oxide, LMO) and demonstrate their reuse in newly assembled Li-ion cells. The electrochemical performance of as-recycled cathodes shows an initial discharge capacity of 72 mAh/g and is stable for 100 cycles at 0.1 C. After adding 20 mole % of excess LiOH, the recycled LMO after relithiation at 660 °C can deliver an initial discharge capacity of 96 mAh/g and retain a decent discharge capacity of 88 mAh/g after 50 cycles at a 0.2 C rate. Without relithiation, the as-recycled LMO cathode after heating at 1000 °C delivers the best electrochemical cycling performance, including an initial discharge capacity of 94 mAh/g and 50th cycle capacity of 91 mAh/g at a 0.2 C rate. This study highlights a feasible approach for recycling electrode materials in spent LIBs. Recycling of lithium-ion batteries and especially electrode materials is crucial for the sustained growth of the lithium-ion battery industry and reduced environmental issues. Full article

In this study, magnetic copper ferrite (CuFe₂O₄) nanoparticles were synthesized via the Pechini sol-gel method and evaluated for the removal of Cd(II) ions from aqueous solutions. PF600 and PF800 refer to the samples that were synthesized at 600 °C and 800 °C, respectively. Comprehensive characterization using FTIR, XRD, FE-SEM, HR-TEM, and EDX confirmed the successful formation of CuFe₂O₄ spinel structures, with crystallite sizes of 22.64 nm (PF600) and 30.13 nm (PF800). FE-SEM analysis revealed particle diameters of 154.98 nm (PF600) and 230.05 nm (PF800), exhibiting spherical and irregular shapes. HR-TEM analysis further confirmed the presence of aggregated nanoparticles with average diameters of 52.26 nm (PF600) and 98.32 nm (PF800). The PF600 and PF800 nanoparticles exhibited exceptional adsorption capacities of 377.36 mg/g and 322.58 mg/g, respectively, significantly outperforming many materials reported in the literature. Adsorption followed the Langmuir isotherm model and pseudo-second-order kinetics, indicating monolayer adsorption and strong physisorption. The process was spontaneous, exothermic, and predominantly physical. Reusability tests demonstrated high adsorption efficiency across multiple cycles when desorbed with a 0.5 M ethylenediaminetetraacetic acid (EDTA) solution, emphasizing the practical applicability of these nanoparticles. The inherent magnetic properties of CuFe₂O₄ facilitated easy separation from the aqueous medium using a magnet, enabling efficient and cost-effective recovery of the adsorbent. These findings highlight the potential of CuFe₂O₄ nanoparticles, particularly PF600, for the effective and sustainable removal of Cd(II) ions from water. Full article

In this article, the sol–gel method was used as a synthesis method, which shows the physicochemical nature of the synthesis of a new complex material, ferrite Li_0.5MnFe_1.5O₄. The structure and composition of the synthesized ferrite were determined by X-ray phase analysis. According to analysis indicators, it was found that our compound is a single-phase, spinel-structured, and syngony-cubic type of compound. The microstructure of the compound and the quantitative composition of the elements contained within it were analyzed under a scanning electron microscope (SEM). Under a scanning electron microscope, microsystems were taken from different parts of Li_0.5MnFe_1.5O₄-type crystallite; the elemental composition of crystals was analyzed; and the general type of surface layer of complex ferrite was shown. As a result, given the fact that the compound consists of a single phase, the clarity of its construction was determined by the topography and chemical composition of the compound. As a result, it was found that the newly synthesized complex ferrites correspond to the formula Li_0.5MnFe_1.5O₄. The particles of the formed compounds have a large size (between 50.0 μm or 20.0 μm and 10.0 μm). Electrophysical measurements were carried out on an LCR-800 unit at intervals of 293–483 K and at frequencies of 1.5 and 10 kHz. An increase in frequency to 10 kHz led to a decrease in the value ε in the range of the studied temperature (293–483 K). Full article

This study presents mineral composition estimates of rock and sediment samples analyzed with the CheMin X-ray diffraction instrument on board the NASA Mars Science Laboratory rover, Curiosity, in Gale crater, Mars. Mineral composition is estimated using crystal-chemically derived algorithms applied to X-ray diffraction data, specifically unit-cell parameters. The mineral groups characterized include those found in major abundance by the CheMin instrument (i.e., feldspar, olivine, pyroxene, and spinel oxide). In addition to estimating the composition of the major mineral phases observed in Gale crater, we place their compositions in a stratigraphic context and provide a comparison to that of martian meteorites. This work provides expanded insights into the mineralogy and chemistry of the martian surface. Full article

Peridot has a long history and is deeply loved by people for its unique olive-green color. The Yiqisong peridot deposit in Jilin Province is a newly discovered peridot deposit that still deserves systematic research. In this study, gemological and chemical analyses of thirty-three Yiqisong peridot samples were carried out to investigate the gemological characteristics, as well as the mantle properties and formation conditions of the Yiqisong. In addition, we identified gemological differences in peridot between Yiqisong, Tanzania, and Arizona. The Yiqisong peridot samples have typical peridot gemological characteristics. The UV–visible spectrum indicated that Fe is the chromogenic element. The infrared spectra and Raman spectra of different samples are consistent, which indicates that the Yiqisong peridot belongs to forsterite. The contents of Ni and V in Yiqisong peridot are generally low, distinguishing it from peridot found in Tanzania and Arizona. The major and trace elements of samples show that the Yiqisong peridot is derived from the spinel lherzolite xenoliths with the P–T formation conditions of 813–1087 °C and 21–22 kbar. The Yisqisong peridot samples have relatively high Fo values (up to 91.6), supporting their origin from a moderate refractory lithosphere mantle. Therefore, this study provides gemological, mineralogical, and chemical evidence that fills the research gap in peridot deposit studies and lays the foundation for follow-up investigations of gem-grade peridot deposits. Full article

Mechanical degradation in electrode materials during successive electrochemical cycling is critical for battery lifetime and aging properties. A common strategy to mitigate electrode mechanical degradation is to suppress the volume variation induced by Li/Na intercalation/deintercalation, thereby designing strain-less electrodes. In this study, we investigate the electrochemically-induced volume variation in layered and spinel compounds used in Li-ion and Na-ion battery electrode materials through density functional theory computations. Specifically, we propose to decompose the volume variation into electronic, ionic, and structural contributions. Based on this analysis, we suggest methods to separately influence each contribution through strategies such as chemical substitution, doping, and polymorphism. Altogether, we conclude that volume variations can be controlled by designing either mechanically hard or compact electrode materials. Full article

The cyclic oxidation behavior of an additive manufactured CoCrMo alloy with 0.14 wt.% C was investigated at 914 °C for 32 cycles, each lasting 10 h, resulting in a total exposure time of 320 h. The oxidation rate was assessed for mass gain after finishing each 40 h oxidation cycle. It was experimentally determined that the oxidative process at 914 °C of this CoCrMo alloy follows a parabolic law, with the process being fast at the beginning and slowing down after the first 40 h. The microstructural analysis revealed that in the as-printed state, the phases developed were primarily the γ matrix and minor traces of ε phase. The oxidative process ensured an increase in the ε phase and precipitation of carbides which produced a 12% increase in the material’s hardness after the first 40 h of exposure at 914 °C. The oxidation process led to the development of an oxide scale comprising a dense Cr₂O₃ layer and a porous layer of CoCr₂O₄ spinel, the latter spalling after the 240 h of exposure. Despite this spallation, the oxide scale continued to develop in the presence of O, Cr, and Co. The experimental analysis provided valuable insights regarding the material’s behavior under prolonged exposure at high temperature in air, demonstrating its suitability as a candidate for additive manufactured mandrels used for bending metallic pipe fitting elbows. Full article

As a typical spinel structure material, ZnMn₂O₄ has been widely researched in the field of electrode materials. However, ZnMn₂O₄ nanoparticles as electrode materials for supercapacitors have the disadvantages of low conductivity, inferior structural integrity, and easy aggregation, resulting in unsatisfying electrochemical performance. In this work, we use a hydrothermal method and high-temperature calcination to deposit ZnMn₂O₄ nanoparticles on carbon cloth and explore the influence of hydrothermal reaction time on the deposition morphology and distribution of ZnMn₂O₄ nanoparticles on carbon cloth. The deposition process of ZnMn₂O₄ nanoparticles on carbon cloth was analyzed, and a ZMO-9 electrode was deduced to be the most suitable electrode for supercapacitors. A series of electrochemical performance tests show that the ZMO-9 electrode has excellent specific capacitance (specific capacity) (499 F·g⁻¹ (299.4 C·g⁻¹) at a current density of 1 A·g⁻¹) and rate performance (75% capacitance retention at a current density of 12 A·g⁻¹). The assembled asymmetric supercapacitor has an energy density of 46.6 Wh·kg⁻¹ when the power density is 800.1 W·kg⁻¹. This work provides a reference for the structural design of ZnMn₂O₄ supercapacitor electrode materials and the improvement of electrochemical properties. Full article

In this study, we synthesized spinel high-entropy oxide (HEO) (Cr_0.2Mn_0.2Co_0.2Ni_0.2Zn_0.2)₃O₄ nanoparticles by a simple solution combustion method. These particles were investigated for their performance as anodes in lithium-ion batteries. The reversible capacity is 132 mAh·g⁻¹ after 100 cycles at a current density of 100 mA·g⁻¹, 107 mAh·g⁻¹ after 1000 cycles at a current density of 1 A g⁻¹, and 96 mAh·g⁻¹ rate capacity at a high current density of 2 A g⁻¹. The outstanding cycle stability under high current densities and remarkable rate performance can be attributed to the stable structure originating from the high entropy of the material. Full article