Carbothermal Reduction Research Articles

Antimony nanoparticles encapsulated in interconnected nitrogen-doped carbon nanospheres for high performances PIBs

Antimony (Sb) has attracted significant attention as an anode material for potassium-ion batteries (PIBs) due to its high theoretical capacity and suitable working voltage. However, the severe volume variations of Sb during potassiation/depotassiation process lead to sluggish kinetics and poor cyclic stability for PIBs. In this study, Sb nanoparticles are confined within interconnected N-doped carbon nanospheres (Sb@NC) through an effective carbothermal reduction process. The potassium storage performances and mechanism are elucidated through electrochemical tests combined with ex-XRD analysis. When used as an anode for PIBs, the optimized Sb@NC-2 anode exhibits excellent cycle stability of 463.0 mAh g−1 at 200 mA g−1 over 100 cycles and superior rate capability of 113.4 mAh g−1 at a high current density of 2 A g−1. Besides, a full cell comprising an Sb@NC-2 anode and a PTCDA cathode is also tested to validate the practical feasibility of the anode. Furthermore, Density Functional Theory (DFT) calculations demonstrate that N-doped carbon can enhance the adsorption of K+ and improve the kinetics of electrochemical reactions. Therefore, the unique yolk-shell structure in this study effectively restricts volume expansion and aggregation of Sb particles while facilitating rapid electron/ion transfer. These findings provide a potential alternative anode material for advanced PIBs.

Synthesis of Mo2C/C nanoclusters attached on rGO nanosheets for high-Efficiency electromagnetic wave absorption

It is an effective strategy that constructing composites with a multi-dimensional structure synergistically enhance their electromagnetic (EM) wave absorbing performance. Herein, a high-efficiency EM wave absorber of Mo2C/C nanoclusters uniformly encapsulated in rGO nanosheets (Mo2C/C-rGO) was prepared by a combination of the directing freeze-dry and subsequently carbothermal reaction method. Mo2C/C was in-situ induced from spherical phosphomolybdic acid/polypyrrole (PMo12/PPy) to result in a unique cluster-like microstructure. Abundant heterogeneous interfaces endowed the Mo2C/C-rGO composites with excellent EM wave absorption performance at a low filling ratio of 5 wt%. The minimum reflection loss (RL) value was −49.3 dB at 1.38 mm and the maximum effective absorption bandwidth (EAB, RL<-10 dB) was 5.12 GHz at 1.60 mm. The excellent performance was owing to the lamellar structure and abundant heterogeneous interfaces in Mo2C/C-rGO, lengthening the transmission path of the incident wave, as well as resulting in high conduction loss and interfacial polarization loss. This universal strategy would be extended to other absorbers with multi-interface structures for lightweight and broadband EM wave absorption.

Carbon reduction of 3D-ink-extruded oxide powders for synthesis of equiatomic CoCuFeNi microlattices

Equiatomic CoCuFeNi high-entropy alloy microlattices are created by 3D-extrusion printing with an ink containing a blend of binary oxides (Co3O4+CuO+Fe2O3+NiO) and graphite (C) powders. After printing, the green parts are subjected to a series of heat treatments under Ar leading to (i) the carbon reduction of the oxides to form metallic particles, (ii) the interdiffusion of these metallic particles to create an alloy, and (iii) sintering to remove porosity. The phase evolution in individual extruded filaments (similar to struts in the microlattices) is observed by in-situ X-ray diffraction, showing that intermediate suboxide phases (Cu2O, CoO, Fe3O4, CuFeO2, and FeO) form as the original oxides are reduced by carbon, before the final metallic alloy is formed. At 830 °C, the extruded filaments comprise a face-centered cubic CoCuNi(+Fe) alloy with unreduced FeO inclusions. After reduction and sintering at 1100 °C, homogeneous, densified, equiatomic CoCuFeNi microlattices are achieved, containing small amounts of a Cu-rich phase. At room temperature, the compressive strength of these CoCuFeNi microlattices increases as the strut diameter decreases from ~260 to ~130µm, as expected from an observed drop in strut porosity resulting from more complete sintering. This is consistent with the easier escape of CO+CO2 gas created during carbothermic oxide reduction from the thinner struts undergoing reduction and sintering.

Microstructure and mechanical properties of (Ti, W, Mo, Nb, Ta) (C0.78, N0.22) high entropy cermets with 5–25 wt% Co–Ni binders

In this study, high entropy (Ti0.6,W0.1,Mo0.1,Nb0.1,Ta0.1)(C0.78,N0.22) ceramics (HECN) powders were synthesized by carbothermal reduction nitridation. (100-x) HECN-(x/2) Co-(x/2) Ni (x = 5–25 wt%) cermet was prepared by vacuum sintering. The relationship between microstructure and mechanical properties of HECN-based cermet sintered at 1450 °C and 1500 °C was studied. The results show that the second phase (W,Mo,Ti)3+x(Co, Ni)3−xC appears at both sintering temperatures, and its content decreases with the increase of binder Co, Ni content and sintering temperature; At the same time, the grain size of the hard phase of the cermet grows with the increase of Co and Ni content. In terms of mechanical properties, at both sintering temperatures, the cermet showed a decrease in hardness and an increase in fracture toughness with the increase of Co and Ni content, while the bending strength increased and then decreased. Among them, when the content of Co and Ni is 20 wt%, the bending strength of HECN-based cermet sintered at 1450 °C is the best, and the bending strength reaches 1640 MPa. This is attributed to the combined influence of many elements in high entropy cermet, which on the one hand leads to serious lattice distortion; On the other hand, improving the wettability and density of the cermet has a strengthening effect on the cermet. In addition, with the increase in Co and Ni content, the plastic deformation of the bond phase will inhibit crack propagation. The main paths are crack deflection and crack bridging, which increase the energy required for crack propagation and lead to a gradual increase in fracture toughness.

Growth mechanism of TaC coating on carbon fibers via molten-salt-assisted carbothermal reduction method

Reactive melt infiltration (RMI) is considered suitable process to prepare C/SiC composites with low porosity and near-net shape. However, because of inevitable reactions between molten metal and carbon fibers, mechanical properties of C/SiC composites may be affected. In this work, continuous TaC coating was successfully prepared on the surface of carbon fibers using molten salt method. Effects of temperature and holding time on microstructure, bonding configurations, and crystal structure of TaC coating were systematically investigated. With increase in temperature and time, TaC grains grew larger and TaC coating became thicker, with growth rate constant of about 3.05 × 10−17 m2/s. TaC coating prepared at 1200 °C for 60 min was continuous, uniform and well bonded with carbon fibers, and the main growth direction of TaC grains was [111]. Activation energy for formation of TaC coating was 295.48 kJ/mol. From a dynamic perspective, diffusion behavior of Ta ions through reaction interface was controlling step for formation of continuous TaC coating.

SnS/C nanostructures endowed by low-temperature in-situ carbothermal reduction of sustainable lignin for stable lithium- and sodium-ion storage

SnS emerges as a promising anode candidate for high-energy–density lithium/sodium-ion batteries, attributed to its substantial theoretical capacity of 1022 mAh/g. However, its practical application faces challenges stemming from intrinsic low conductivity and substantial volume variation during lithium/sodium intercalation and deintercalation processes. To address these limitations, we present a cost-effective hydrothermal synthesis combined with an in-situ carbothermal reduction approach for fabricating a nanoflower-like porous carbon-wrapped SnS (SnS/C NFs) anode. The porous carbon shell mitigates the volume expansion of SnS and enhances electronic/ionic conductivity, owing to the porous structure and formation of C-S-C bonds. The SnS/C NFs anode delivered excellent rate performance and long-term cycling stability with high specific capacity both in LIBs (1120 mAh/g after 1000 cycles at 1 A/g) and SIBs (399.3 mAh/g after 500 cycles at 1 A/g). This work provides a safe and low-cost approach for next-generation advanced LIBs and SIBs anodes.

A process for preferential recovery of lithium and manganese from spent NCM by vacuum carbothermal reduction method

In this study, a process was developed for the preferential recovery of lithium and manganese from spent ternary lithium batteries using the vacuum carbothermal reduction method. Firstly, the electrolyte and PVDF in the cathode and anode wafers of the spent ternary lithium batteries were removed. Subsequently, lithium in the cathode powder was preferentially recovered under vacuum conditions using the anodic powder as a reducing agent. The findings show that at 1623 K and 25 %for 2 h, the reduction process generates Li2O, (NiO)m-(MnO)n, Ni, and Co as the ultimate products. Reduction roasting enables the preferential extraction of 99.99 % Li and 99.82 % Mn, which condense on the condensation tray as Li2O and MnOx, while Ni and Co are present in the residue as oxides and monomers. In summary, the whole process of the vacuum carbothermal reduction method achieves efficient extraction of Li and Mn while avoiding the subsequent recovery of Ni, Co, and Mn. It also minimizes Li loss and Mn contamination during the recovery of Ni and Co. Additionally, by utilizing the cathode material from waste LIBs. This process realises the use of waste for waste management, resulting in significant cost savings in recycling and reducing environmental harm.

Pre-separation combined with reduction roasting for high-quality recovery of graphite and lithium from spent lithium ion batteries

The recycling of spent lithium ion batteries is of great significance because it contains large amounts of valuable metals. But current recovery methods exhibit limited efficiency in selectively extracting lithium from spent electrode materials and spent graphite becomes metallurgical residues. In this study, we propose a novel recycling flowchart that combines flotation with multi-stage water-leaching to enhance the recovery of graphite and lithium from black mass derived from spent lithium ion batteries. Removal of organics can be conducted by pyrolysis, at the same time, the spent ternary cathode material was decomposed into CoO, NiO, and MnO at a temperature of 600 °C for 60 min using pyrolysis product-derived reductant. The sub-microlevel migration behavior of lithium ions in electrode materials was also examined. The electrode material aggregates were broken up by water crushing, and 38.67 % lithium dissolves into water for recycling. Bubble flotation was used to recycle the excess graphite from the black mass while the residual graphite was used as reductant for the carbothermal reduction. Using the developed scheme, we were able to recover 95.51 % of lithium after carbothermal reduction with 12.31 % carbon residue. Based on basic research, a novel recycling flowchart of spent lithium-ion batteries has been proposed.

Synthesis and growth mechanism of highly crystalized multi-branched HfB2 microrods with self-toughening effect

Development of strategies to toughen HfB2 ceramic, improve their mechanical properties is the key to promote their applications in extreme thermal environments. This study explores a kind of self-toughening method of HfB2 ceramic by incorporation the highly crystalized multi-branched HfB2 microrods. The multi-branched HfB2 microrods were synthesized by sol–gel process and carbothermal reduction, exhibiting length of 6–13 μm and diameter of 0.60–1.50 μm, respectively. Detailed analysis of the formation mechanism of HfB2 microrods reveals that the HfB2 multi-branched structure is a collaborative consequence of orientation attachment mechanism and reactive templates growth, in which process monoclinic HfO2 crystals transform into crystalized HfO2 microrods at ∼1000 °C, and worked as template to induce one-dimensional HfB2 microrods. Furthermore, spark plasma sintering experiments show that the optimal mechanical properties were attained by 6 wt% addition of HfB2 microrods, comparing with HfB2 ceramics free of self-toughening agent, the hardness and fracture toughness of self-toughened HfB2 ceramic improved by 8.82 % and 81.91 % respectively, demonstrating the effectiveness of self-toughening of the microrods without sacrificing the hardness of HfB2 ceramic. Thus, it can be seen that the work has important reference value for the synthesis of HfB2 powder with different morphologies and the toughening of HfB2 ceramics.

Bio-Carbon Assisted Carbothermal Reduction Process for the Recovery of Lithium and Cobalt from the Spent Lithium-Ion Batteries

Bio-Carbon Assisted Carbothermal Reduction Process for the Recovery of Lithium and Cobalt from the Spent Lithium-Ion Batteries

Gallium distribution between slag and metal phases during the carbothermal reduction of bauxite

This article investigated the recoverability of the Ga in bauxite by carbothermal reduction. Currently, Ga is mostly manufactured from bauxite through the Bayer process as a by-product of alumina, but it is worthwhile to consider alternative processes under stricter environmental regulations and a shortage of high-quality bauxite. This study focused on the Pedersen process, which is the alumina production process consisting of carbothermal reduction and alkaline leaching. The metal and slag phases were prepared by carbothermal reduction of bauxite at 1873 K, and then aluminium in the slag was leached with (Na2CO3 + NaOH) solution at 348 K. Evaluation by inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry revealed that almost all Ga in bauxite was transferred to the metal phase, and the distribution to the slag phase was negligible in carbothermal reduction, which agrees with the thermodynamic consideration. These results suggest that the gallium recovery from pig iron is necessary to produce Ga in the Pedersen process.

Revealing the delithiation process of spent LiMn2O4 and LiNi0.6Co0.2Mn0.2O2 batteries during the biomass-assisted gasthermal and carbothermal reduction

The utilization of biomass-assisted pyrolysis in the recycling of spent lithium-ion batteries has emerged as a promising and reliable process. This article furnishes theoretical underpinnings and analytical insights into this method, showcasing sawdust pyrolysis reduction as an efficient means to recycle spent LiMn2O4 and LiNi0.6Co0.2Mn0.2O2 batteries. Through advanced thermogravimetry-gas chromatography-mass spectrometry analysis complemented by traditional thermodynamic demonstration, the synergistic effects of biomass pyrolysis reduction are elucidated, with minor autodecomposition and major carbothermal and gasthermal reduction pathways identified. The controlled manipulation of transition metals has demonstrated the capability to modulate surface pyrolysis gas catalytic reactions and facilitate the preparation of composite materials with diverse morphologies. Optimization of process conditions has culminated in recovery efficiency exceeding 99.0 % for LiMn2O4 and 99.5 % for LiNi0.6Co0.2Mn0.2O2. Economic and environmental analyses underscore the advantages of biomass reduction and recycling for these two types of spent LIBs: low energy consumption, environmental compatibility, and high economic viability.

Co-Extraction of Aluminum and Silicon and Kinetics Analysis in Carbochlorination Process of Low-Grade Bauxite.

Addressing the issue that the Bayer process is not suitable for low-grade bauxite, carbochlorination was proposed to recover aluminum and silicon from low-grade bauxite. This study focused on the behavior of aluminum and silicon during the carbochlorination process of low-grade bauxite. The impact of various process parameters on the chlorination efficiency was investigated, and the chlorination mechanism and kinetics of aluminum and silicon chlorination in bauxite were analyzed and discussed. Under optimal experimental conditions, the chlorination efficiency of Al2O3 and SiO2 reached 94.93% and 86.32%, respectively. The carbochlorination of aluminum and silicon in bauxite adhered to a shrinking, unreacted core model governed by gas diffusion within the product layer. This process can be bifurcated into two stages. Additionally, calculations were conducted to determine the apparent activation energy and reaction order of the chlorination processes involving Al2O3 and SiO2. Examining the chlorination mechanism revealed that the bauxite carbochlorination encompasses transformations among various minerals. Notably, the aluminum component prefers to participate in the carbothermal chlorination reaction over silicon.

Interface migration and alloying mechanism of Fe and P for ferrophosphorus alloy production during the carbothermic reduction of phosphorite

Ferrophosphorus (Fe–P alloy), a byproduct in the carbothermal reduction of phosphorite for yellow phosphorus production, has remarkable potential application as foundational precursors to prepare advanced catalysts and energy materials. However, the gas-solid-liquid equilibrium in the reduction smelting of phosphorite and hematite is intricate, and the reduction, volatilization, and alloying mechanisms of Fe and P at higher temperatures should be given close attention to optimize the production of yellow phosphorus vapor and Fe–P alloy. In this study, the reduction smelting behaviors of fluorapatite and hematite in the phosphorite ore were investigated. Carbothermic reduction reactions of Ca5(PO4)3F with and without Fe2O3 are calculated, establishing theoretical fundamentals. The phase and microstructure evolutions of Ca5(PO4)3F and Fe2O3 are researched. This work also emphasizes the interfacial element migration to clarify the reduction, volatilization, and alloying of Fe and P by considering the solid-solid interface of Ca5(PO4)3F–Fe2O3 and the gas-liquid interface of P2 vapor-metallic Fe.

Fabrication of Si3N4 ceramics with improved thermal conductivity by carbothermal reduction and two‐step sintering

AbstractSi3N4 ceramics with improved thermal conductivity and mechanical properties were prepared by carbothermal reduction and two‐step sintering. The addition of 2 wt% C led to the development of an intergranular phase YNSiO2 with reduced oxygen content. Notably, setting the pre‐sintering temperature at 1450°C promoted the formation of a rough bimodal morphology within the Si3N4 ceramics. Furthermore, an extended holding period at 1850°C resulted in additional grain growth and the elimination of intergranular phases. The Si3N4 specimens produced at 1450°C for 3 h followed by 1850°C for 8 h, incorporating 2 wt% C, exhibited a notable continuity between Si3N4 grains. The thickness of the grain boundary layer was only about 1 nm, and the N/O atomic ratio of the intergranular phase was measured to be 0.42. Consequently, the resulting thermal conductivity, flexural strength, and fracture toughness of Si3N4 specimens were found to be 101 W·m−1·K−1, 712 ± 29 MPa, and 7.7 ± 0.2 MPa·m1/2, respectively. Compared with samples without C additive and directly sintered at 1850°C for 8 h, the Si3N4 specimens produced in this work showed a significant increase of more than 50% in thermal conductivity and about 17% in fracture toughness.

Highly stable carbon-coated nZVI composite Fe0@RF-C for efficient degradation of emerging contaminants

Nanoscale zerovalent iron (nZVI) has garnered significant attention as an efficient advanced oxidation activator, but its practical application is hindered by aggregation and oxidation. Coating nZVI with carbon can effectively addresses these issues. A simple and scalable production method for carbon-coated nZVI composite is highly desirable. The anti-oxidation and catalytic performance of carbon-coated nZVI composite merit in-depth research. In this study, a highly stable carbon-coated core-shell nZVI composite (Fe0@RF-C) was successfully prepared using a simple method combining phenolic resin embedding and carbothermal reduction. Fe0@RF-C was employed as a heterogeneous persulfate (PS) activator for degrading 2,4-dihydroxybenzophenone (BP-1), an emerging contaminant. Compared to commercial nZVI, Fe0@RF-C exhibited superior PS activation performance and oxidation resistance. Nearly 95% of BP-1 was removed within 10 min in the Fe0@RF-C/PS system. The carbon layer promotes the enrichment of BP-1 and accelerates its degradation through singlet oxygen oxidation and direct electron transfer processes. This study provides a straightforward approach for designing highly stable carbon-coated nZVI composite and elucidates the enhanced catalytic performance mechanism by carbon layers.

Fe nanoparticle-functionalized ordered mesoporous carbon with tailored mesostructures and their applications in magnetic removal of Ag(i)

Abstract Fe nanoparticle-functionalized ordered mesoporous carbon (Fe0/OMC) was synthesized using triblock copolymers as templates and through solvent evaporation self-assembly, followed by a carbothermal reduction. Fe0/OMC had three microstructures of two-dimensional hexagonal (space group, p6mm, Fe0/OMC-1), body centered cubic (Im3̄m, Fe0/OMC-2), and face centered cubic (Fm3̄m, Fe0/OMC-3) which were controlled by simply adjusting the template. All Fe0/OMC displayed paramagnetic characteristics, with a maximum saturation magnetization of 50.1 emu·g−1. This high magnetization is advantageous for the swift extraction of the adsorbent from the solution following the adsorption process. Fe0/OMC was used as an adsorbent for the removal of silver ions (Ag(i)) from aqueous solutions, and the adsorption capacity of Fe0/OMC-1 was enhanced by the functionalization of Fe0. Adsorption property of Fe0/OMC-1 was significantly higher than that of Fe0/OMC-2 and Fe0/OMC-3, indicating that the long and straight ordered pore channels were more favorable for adsorption, and the adsorption capacity of Ag(i) on Fe0/OMC-1 was 233 mg·g−1. The adsorption process exhibited conformity with both the pseudo-second-order kinetic model and the Freundlich model, suggesting that the dominant mechanism of adsorption involved multilayer adsorption on heterogeneous surfaces.

Thermodynamic modeling of silicon carbide formation during the Acheson process in non-stoichiometric mixtures

A brief review and critical evaluation of the literature related to the mechanism of carbothermic reduction of silicon oxide is presented. To resolve the contradictions in the literature data about the number of chemical reactions and key intermediate substances during the Acheson process, thermodynamic modeling of products of carbothermic reduction of silicon (IV) oxide at 1 bar total pressure was carried out. It was determined that CO2 and Si were absent among the intermediates at temperatures close to the silicon carbide formation temperature (from 1520 to ~2500 °С). Out of several dozen possible reactions, the two dominant reactions that result in the formation of silicon carbide in the Acheson process were identified. The effect of reagents temperature from 1000 to 3000 °С, bulk and local deviation from stoichiometry of the initial mixture on the composition of the reaction products was discovered. Obtained new data explains some empirical observations and greatly simplifies the physicochemical modeling of the Acheson process.

Boosting proton intercalation via sulfur anion doping in V2O3 cathode materials towards high capacity and rate performance of aqueous zinc ion batteries

Aqueous zinc-ion batteries (ZIBs) are a prospective solution for grid-scale energy storage. V2O3 has emerged as a promising cathode candidate with reversible two-electron redox capability for ZIBs. However, it still faces problems such as poor electronic conductivity and sluggish ion embedding kinetics. Herein, we report sulfur anion-doped V2O3 with tunneled structure based on a facile carbothermal reduction method, which can exhibit the significant impact of sulfur anion-doping on proton storage in vanadium-based cathode materials for high capacity and rate performance of ZIBs. The covalent bonds in S-V-O lead to accelerated charge transfer and elevated electronic conductivity. In-situ X-ray diffraction, synchrotron-based X-ray absorption spectroscopy combined with DFT calculations demonstrate that S doping effectively diminishes the adsorption and embedding energies of H+ in V2O3 and greatly boosts proton insertion kinetics. The co-intercalation of H+/Zn2+ helps compensate for the deficiency of Zn2+ insertion/extraction kinetics. Amorphous transition of crystalline V2O3 initiated from initial charging is conducive to mitigating stress and retaining stable cycling capacity. The typical sulfur-doped V2O3 achieves remarkable capacity (470.4 mAh·g−1 at 0.5 A·g−1), excellent rate capability (264.6 mAh·g−1 at 10 A·g−1) and stable long-term cyclability (231.2 mAh·g−1 at 10 A·g−1 after 2000 cycles). Furthermore, the corresponding pouch cells can deliver 26 mAh at 1 A·g−1 after 250 cycles, holding great potential for practical applications.

Silicon Carbide-based Materials from Rice Husk

Background: Rice husk is an important agricultural waste that contains organic mass and bio-silica. Although some rice husks have been used as fuel, animal food, filler for wine fermentation, and fertilizer, the majority are discarded as agricultural waste, which does great harm to the environment. The conversion of rice husk to silicon carbide (SiC)-based materials satisfies the demand for the reutilization of solid wastes. Methods: The article reviews recent progress and patents on the SiC-based materials from rice husk. The possible development directions of the SiC-based materials from rice husks are also analyzed. Results: SiC materials with different morphologies, including microscale and nanoscale particles, nanoscale whiskers, and nanowires, can be prepared by high-temperature carbothermal reduction reaction from rice husk at the temperature of 1200-1800 °C, reaction time of 0.5-8 h, respectively. SiC-based composites, including SiC nanowires/C, Al/SiC, SiC/Si3N4, and SiC/Al2O3, can be obtained using rice husk as main source materials at 800-1800 °C. SiC-based materials exhibit great application potential in the fields of absorbents, optical devices, mechanical products, photocatalysts, semiconductors, and Li-ion batteries. Conclusion: The low cost of preparing SiC-based materials from rice husk, combining them with different compositions, and exploring new applications are important research directions in the future.