479 research outputs found

    Synthesis of silicon nanoparticles with various additions of inert salt as scavenger agent during reduction by the magnesiothermic method as anode lithium-ion batteries

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    A heat scavenger agent magnesiothermic reduction of quartz sand was used to make Si nanoparticles in a way that can be easily scaled up. Its source of SiO2 is safe for the environment, easy to get, and cheap. It can make silicon nanoparticles that work well as an anode material for Li-ion batteries. It is known that using inert salt NaCl has a better characterization of Si and electrochemical performance than KCl, KBr, and CaCl2. XRD diffractogram show 2θ are formed at 27.42°, 47.30°, 56.11°, 69.19°, and 76.37°. The surface area shows 9.75 m2/g, and the pore size is 15.35 Å. In the TEM images, it is found that the silicon shape is spherical. The electrical conductivity voltage of 1 V is 2599.33 µS/cm. The cyclic voltammetry curve during the highest oxidation is 0.57 V, and the lowest oxidation peak is 0.16 V. After the first cycle, the Rs is 4.22 Ω, and the Rct formed is 51.19 Ω. The first discharge capacity is 2599.57 mAh/g, corresponding to coulombic efficiencies at 97.12 %

    Deoxidation thermodynamics of Ti–O in hydrogen atmosphere: Preparation of TiH2 alloy powder by direct reduction of spent V2O5–WO3/TiO2 catalyst with magnesiothermic

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    The abundant metal Ti is a high-quality metal with lightweight, high strength, and corrosion resistance. However, due to its harsh preparation conditions, the price remains high, so titanium metal's simple and effective products have become a challenge for the world's scientific research community. In this paper, by calculating the oxygen potential of Ti–O, Ti–H, and Ti–H–O solid solutions, the oxygen potential of Ti–H–O was obtained when the oxygen content was 0.03 and 0.009. As H2 enters the Ti–O lattice, the oxygen potential of the Ti–H–O system increases with the increase of H content. Thermodynamic calculations showed that introducing hydrogen effectively destroyed the stability of Ti–O solid solutions. At the same time, this paper uses a magnesiothermic as a reducing agent. To verify the feasibility of the above thermodynamics, reduce the spent V2O5–WO3/TiO2 catalyst (Ti > 80 wt%) of titanium-rich materials in a hydrogen atmosphere. Finally, the spent V2O5–WO3/TiO2 catalyst was reduced at 750 °C for 8–24 h to obtain TiH2 powder with an oxygen content of 0.9 wt%

    Plasma defect-engineering of bulk oxygen-deficient zirconia

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    Oxygen-deficient zirconia (ZrO2-x) has recently emerged as a promising material for light absorption and photocatalytic applications. However, the economic and environmentally friendly manufacture of bulk ZrO2-x remains challenging and has limited widespread adoption. In this study, we present a novel low-pressure (300 Pa) plasma treatment (H2 gas at 500 °C for 5 h) capable of producing fully-dense bulk ZrO2-x without significant structural modifications. EPR (electron paramagnetic resonance) and XPS (X-ray photoelectron spectroscopy) characterisation of the plasma treated zirconia indicate the formation of Zr3+ ions and F2+ (V0) centres. The increase of oxygen vacancies is also supported by the greater exothermic heat flow and relative mass gain observed through TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry) analyses. Diffuse reflectance spectroscopy (DRS) reveals a substantial enhancement in light absorption, with an average increase of 66.2 % and >65 % absolute absorption across the entire spectrum (200–3000 nm). XPS and DRS measurements suggest significant reduction in both direct (from 4.84 to 2.61 eV) and indirect (from 3.19 to 1.45 eV) bandgap transition. By effectively enhancing the light absorption capability, reducing bandgap transitions, and maintaining the structural integrity of zirconia, low-pressure plasma treatments offer a promising and scalable approach for the environmentally friendly production of next-generation ZrO2-x materials

    Synthesis and Properties of Silicon Carbide (Review)

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    Silicon carbide is an extremely hard material that exhibits exceptional corrosion resistance as well as thermal shock resistance. Its high mechanical properties determine the increased performance of materials based on it. The combination of high thermal conductivity and low thermal expansion coefficient determines the stability of silicon carbide at high heating rates and under stationary thermal conditions. To date, significant progress has been made in the development of methods for the synthesis of various materials based on silicon carbide. The main synthesis methods that scientists use in their research are the sol-gel method, sintering, pyrolysis, microwave synthesis, chemical vapor deposition, etc. The use of "green" techniques in the synthesis of SiC has gained wide popularity due to environmental friendliness, renewability, and ease of implementation. This review analyzes modern research in the field of silicon carbide synthesis published in peer-reviewed professional journals

    Nanoporous silicon fiber networks in a composite anode for all-solid-state batteries with superior cycling performance

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    Abstract All-solid-state batteries comprising Si anodes are promising materials for energy storage in electronic vehicles because their energy density is approximately 1.7 times higher than that of graphite anodes. However, Si undergoes severe volume changes during cycling, resulting in the loss of electronic and ionic conduction pathways and rapid capacity fading. To address this challenge, we developed composite anodes with a nanoporous Si fiber network structure in sulfide-based solid electrolytes (SEs) and conductive additives. Nanoporous Si fibers were fabricated by electrospinning, followed by magnesiothermic reduction. The total pore volume of the fibers allowed pore shrinkage to compensate for the volumetric expansion of Li12Si7, thereby suppressing outward expansion and preserving the Si-SE (or conductive additive) interface. The network structure of the lithiated Si fibers compensates for electronic and ionic conduction pathways even to the partially delaminated areas, leading to increased Si utilization. The anodes exhibited superior performance, achieving an initial Coulombic efficiency of 71%, a reversible capacity of 1474 mAh g−1, and capacity retention of 85% after 40 cycles with an industrially acceptable areal capacity of 1.3 mAh cm−2. The proposed approach can reduce the constraint pressure during charging/discharging and may have practical applications in large-area all-solid-state batteries

    Biomass-derived carbon–silicon composites (C@Si) as anodes for lithium-ion and sodium-ion batteries: A promising strategy towards long-term cycling stability: A mini review

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    The global need for high energy density and performing rechargeable batteries has led to the development of high-capacity silicon-based anode materials to meet the energy demands imposed to electrify plug-in vehicles to curtail carbon emissions by 2035. Unfortunately, the high theoretical capacity (4200 mA h g−1) of silicon by (de-)alloy mechanism is limited by its severe volume changes (ΔV ∼ 200% − 400%) during cycling for lithium-ion batteries (LIBs), while for sodium-ion batteries (NIBs) remain uncertain, and hence, compositing with carbons (C@Si) represent a promising strategy to enable the aforementioned practical application. The present review outlines the recent progress of biomass-derived Si-carbon composite (C@Si) anodes for LIBs and NIBs. In this perspective, we present different types of biomass precursors, silicon sources, and compositing strategies, and how these impact on the C@Si physicochemical properties and their electrochemical performance are discussed

    Ultrathin Magnesium-based Coating as an Efficient Oxygen Barrier for Superconducting Circuit Materials

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    Scaling up superconducting quantum circuits based on transmon qubits necessitates substantial enhancements in qubit coherence time. Among the materials considered for transmon qubits, tantalum (Ta) has emerged as a promising candidate, surpassing conventional counterparts in terms of coherence time. However, the presence of an amorphous surface Ta oxide layer introduces dielectric loss, ultimately placing a limit on the coherence time. In this study, we present a novel approach for suppressing the formation of tantalum oxide using an ultrathin magnesium (Mg) capping layer deposited on top of tantalum. Synchrotron-based X-ray photoelectron spectroscopy (XPS) studies demonstrate that oxide is confined to an extremely thin region directly beneath the Mg/Ta interface. Additionally, we demonstrate that the superconducting properties of thin Ta films are improved following the Mg capping, exhibiting sharper and higher-temperature transitions to superconductive and magnetically ordered states. Based on the experimental data and computational modeling, we establish an atomic-scale mechanistic understanding of the role of the capping layer in protecting Ta from oxidation. This work provides valuable insights into the formation mechanism and functionality of surface tantalum oxide, as well as a new materials design principle with the potential to reduce dielectric loss in superconducting quantum materials. Ultimately, our findings pave the way for the realization of large-scale, high-performance quantum computing systems

    Rice husk as anode material for Li-ion batteries and beyond

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    Introduction: Rice husk (RH) the outer covering of a rice kernel, is an abundant agricultural byproduct that can be source of anode materials for lithium-ion batteries (LIBs). From RHs both carbon (from the organic constituents), and silicon (RHs contain ~ 10/15% wt of silica) can be derived. As anode material for LIBs, Si has a theoretical capacity ten folds that of standard graphite electrodes, but it is subjected to huge volumetric expansion upon lithiation (> 300% for bulk) which leads to high mechanical instability and thus to rapid battery failure. Compositing nanosized Si domains with C is an effective route towards mechanical stability while also increasing the anode conductivity. Direct carbonization of RH at high temperature gives hard carbon, so RH-C is also suitable for sodium intercalation. In this work, different C/SiO2 and C/SiO2/Si composites derived from RH are tested in half-cell configuration vs. Li as well as Na, both with conventional (LP30) and non-conventional glyoxal based electrolyte (i.e., LiTFSI in TEG:PC, NaTFSI in TEG:PC). Material and Methods: As a first trial, RH has been carbonized in Ar atmosphere either up to 800°C in a tubular oven (sample RH800) or up to 1000°C (RH1000). These two samples were then used as active material for preparing electrodes without any further treatment. Moreover, after the same carbonization at 800°C, a third sample has undergone a magnesiothermic reduction at 700°C in a tubular oven under Ar. The thus obtained silica-reduced sample (RHMgR) has been washed with HCl and filtered with distilled water (H20dist) to remove by-products (mainly MgO). All the samples have been characterized by XRD, BET surface analysis, XPS, SEM-EDX. Electrodes were prepared by depositing on Cu foil a slurry of active material (90%), carbon black (5%) and CMC (5%) in H20dist. Results: All the samples were characterized by cyclic voltammetry (CV) and galvanostatically cycled in Li-half cells with standard LP30 electrolyte and the alternative glyoxal-based electrolyte. Directly carbonized samples have also been similarly tested in Na-half cells. Discussion Preliminary results show that the directly carbonized samples behave like hard-carbons: no clear redox peaks during CVs, good capacity retention at 1C cycling (calculated on graphite-rates) although an increase of capacity over cycling may suggest SiO2 activation. Charge-discharge cycling of the RH-derived anodes has been also proved to work with Na-disc as counter-electrode. The effect of glyoxal-based electrolyte on all samples and the electrochemical behaviour of the Si-containing sample are currently under investigation

    Preparation of RE-containing magnesium alloys via molten-salt-mediated magnesiothermic reduction

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    RE-containing magnesium alloys were prepared via molten-salt-mediated magnesiothermic reduction by using RE2O3 (RE=Y, Nd and Gd) and Mg metal as raw materials. The thermomechanical analysis of the magnesiothermic reduction reactions in molten salt was investigated. Then the molten-salt-mediated magnesiothermic reduction process was studied from three different perspectives. After that, the RE-containing magnesium alloy was characterized by using chemical analysis, XRD analysis and SEM analysis. The magnesiothermic reduction was a liquid-liquid reaction with relatively weak driving force. During the melting process and the magnesiothermic reduction process, magnesium metal and the obtained alloy went up and down as a whole in molten salt, which improved the process safety without introducing chloride inclusions. Meanwhile, the hydrolysis of the RECl3-containing molten salt occurred at elevated temperature, which severely impeded the magnesiothermic reduction process. After the magnesiothermic reduction at 750 °C for 2.0 h, the content of RE and the common impurity elements in the obtained RE-containing alloy met the both requirements of the commercial WE43A and WE43B

    Advanced Transition Metal-Based Anode Materials and their Composites for Lithium Ion Battery Application

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    In this thesis, conversion type anode materials including transition metal oxides (MoO3, MoO2,WOx), disulfides (WS2) and the insertion reaction-based carbides with MXene-structure (Ti3C2,Nb2C, V2C), as well as their composites, were investigated as potential anode materials for next generation lithium ion batteries (LIBs). MXenes were prepared by an selective etching-based process. When used as anode materials forLIBs, the synthesized MXenes electrodes exhibit excellent cycling stability due to their high electronic conductivity, layered structure as well as good mechanical properties. In order toimprove the specific capacity (<300 mAh g-1) of the MXenes, composites based on Nb2C- andV2C-MXenes and conversion-based high-capacity anode materials (MoO2 and MoO3) were produced. The here presented MoO3/Nb2C was synthesized by a ball-milling method and MoO2/C/V2C by an electrostatically assisted hydrothermal method. Crucial experimental parameters for the ball-milled MoO3/Nb2C (ball-milling time, ball-milling speed, and mass ratio of components) were varied to optimize the morphology and thus the battery performance. The best properties are obtained for MoO3/Nb2C composite synthesized with a mass ratio of 1:1 where a capacity of 261 mAh g-1 is found after 300 cycles at a current density of 100 mA g-1. The uniquely structured hydrothermally synthesized MoO2/C/V2C composites consist of uniformly distributed MoO2 in the hierarchical V2C/C structure. When used as anode materials for LIBs, the composites show outstanding cycling stability and superior rate capability with, e.g., 96% capacity retention (605 mAh g-1) at a high current density of 1000 mA g-1 after 400 cycles. Lastly, carbon-coated tungsten oxides based on low-cost carbon sources (CTAB or PVP) were synthesized by a hydrothermal, carbonization process. An additional sulfurization process yielded carbon-coated disulfides. When used as anode materials for LIBs, the CTAB-assisted tungsten oxide carbon composite (c-WOx/C), tungsten disulfide carbon composite (c-WS2/C), and mixedphase (c-WOx/C-WS2/C) electrodes show outstanding cycling stability and rate performance compared to pristine ones. Particularly, the c-WS2/C electrode shows superior long-term cycle stability of 97% retention after 500 cycles at a high current density of 500 mA g-1. Similarly, the PVP-assisted WS2/C (p-WS2/C) electrode displays a capacity retention of 80% after 500 cycles. This work, therefore, presents a scalable and low-cost route to prepare carbon-coated tungsten oxide and disulfide for high performance LIBs, which can be extended for the preparation of other carbon-coated metal-based materials