Abstract ：

In producing electrolytic manganese and manganese-based lithium batteries, Manganous sulfate solution serves as a crucial intermediate material. During the preparation of manganese sulfate solution by acid leaching, the removal of impurities such as zinc, nickel, and cobalt ions by sulfide precipitation is essential for obtaining high-quality metallic manganese and high-purity manganese sulfate. The results show that when the temperature is 45 °C, the pH is 5.60, the ammonium sulfide dosage is 40 %, the time is 5 min, and the rotation speed is 650 rpm, the sulfidation rates of zinc, nickel and cobalt are 99.07 %, 89.30 %, and 87.70 % respectively. At this time, the loss rate of manganese in the solution after sulfide impurity removal is 11.45 %, and the manganese-impurity ratio is 80.00. Response surface methodology analysis revealed that temperature, pH, and ammonium sulfide concentration significantly affected the manganese loss rate. After process optimization, at a temperature of 32.70 °C, a pH of 5.20, and an ammonium sulfide concentration of 32.73 %, the manganese loss rate decreased to 6.05 %, while the removal rates of Ni, Co, and Zn were 75.35 %, 60.80 %, and 99.51 %, respectively. In the Manganous sulfate electrolyte with or without ammonium sulfate, the sulfide precipitation processes of zinc, nickel and cobalt ion are all first-order reactions, and the reaction order is zinc > nickel > cobalt. More importantly, the density functional theory (DFT) calculation results also confirmed the formation sequence of zinc sulfide > nickel sulfide > cobaltous sulfide, which supported the experimental results well. This study will lay the foundation for process optimization and mechanism elucidation of impurity ions in ammonium sulfate electrolyte precipitated by ammonium sulfate. © 2024 Elsevier B.V.

Keyword ：

Cobalt compounds Sulfur compounds Density functional theory Optimization Process control Precipitation (chemical) Electrolytes Nickel compounds Lithium-ion batteries II-VI semiconductors Manganese compounds Ions Nitrogen compounds

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Abstract ：

The manganese-cobalt mixed oxide nanorods were fabricated using a hydrothermal method with different metal precursors (KMnO4 and MnSO4·H2O for MnOx and Co(NO3)2⋅6H2O and CoCl2⋅6H2O for Co3O4). Bamboo-like MnO2⋅Co3O4 (B-MnO2⋅Co3O4 (S)) was derived from repeated hydrothermal treatments with Co3O4@MnO2 and MnSO4⋅H2O, whereas Co3O4@MnO2 nanorods were derived from hydrothermal treatment with Co3O4 nanorods and KMnO4. The study shows that manganese oxide was tetragonal, while the cobalt oxide was found to be cubic in the crystalline arrangement. Mn surface ions were present in multiple oxidation states (e.g., Mn4+ and Mn3+) and surface oxygen deficiencies. The content of adsorbed oxygen species and reducibility at low temperature declined in the sequence of B-MnO2⋅Co3O4 (S) > Co3O4@MnO2 > MnO2 > Co3O4, matching the changing trend in activity. Among all the samples, B-MnO2⋅Co3O4 (S) showed the preeminent catalytic performance for the oxidation of toluene (T10% = 187°C, T50% = 276°C, and T90% = 339°C). In addition, the B-MnO2⋅Co3O4 (S) sample also exhibited good H2O-, CO2-, and SO2-resistant performance. The good catalytic performance of B-MnO2⋅Co3O4 (S) is due to the high concentration of adsorbed oxygen species and good reducibility at low temperature. Toluene oxidation over B-MnO2⋅Co3O4 (S) proceeds through the adsorption of O2 and toluene to form O*, OH*, and H2C(C6H5)* species, which then react to produce benzyl alcohol, benzoic acid, and benzaldehyde, ultimately converting to CO2 and H2O. The findings suggest that B-MnO2⋅Co3O4 (S) has promising potential for use as an effective catalyst in practical applications. © 2023

Keyword ：

Bamboo-like morphology Hydrothermal method Manganese-cobalt mixed oxide Nanorod Toluene oxidation

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Abstract ：

Friction rolling additive manufacturing (FRAM) is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head. The thermal efficiency of FRAM, which depends only on friction to generate heat, is low, and the thermal-accumulation effect of the deposition process must be addressed. An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling (PC-FRAM) is devised in this study, and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head. Additionally, 2195-T87 Al-Li alloy is used as the feed material, and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated. The results show that water cooling significantly improves heat accumulation during the deposition process. The cooling rate increases by 11.7 times, and the high-temperature residence time decreases by more than 50 %. The grain size of the PC-FRAM sample is the smallest, i.e., 3.77±1.03 μm, its dislocation density is the highest, and the number density of precipitates is the highest, the size of precipitates is the smallest, which shows the best precipitation-strengthening effect. The hardness test results are consistent with the precipitation distribution. The ultimate tensile strength, yield strength and elongation of the PC-FRAM samples are the highest (351±15.6 MPa, 251.3 ± 15.8 MPa and 16.25 %±1.25 %, respectively) among the samples investigated. The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples. The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect. © 2024

Keyword ：

Friction rolling additive manufacturing Plasma preheating Heat accumulation Al-Li alloy Microstructure Instant cooling

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Abstract ：

Mixed-matrix membranes (MMMs) incorporating Metal-Organic Frameworks (MOFs) represent a promising approach for gas separation, which can combine the advantages of selective adsorbents and processable polymers, and display great potential in the gas separation process. However, the further application of MMMs is severely impeded owing to the non-ideal interface between fillers and polymer matrix. In this work, a series of MIL-101(Cr) nanofillers, equipped with different kinds of counter anions were introduced to regulate the chemical microenvironment of the MMMs and improve the interfacial relationship between inorganic filler and polymer. The filler of MIL-101-HNO3 exhibits improved dispersibility in solvents and heightened interface relationship with the polymer matrix (PIM-1) due to its optimal particle size and distinctive exposure of crystallographic planes. Moreover, gas sorption isotherms reveal that the MIL-101-HNO3 MOF show reduced N2 adsorption capacity. Therefore, the MOF filler of MMMs were optimized rationally by microenvironment regulate strategy, leading to the MIL-101-HNO3/PIM-1 MMMs achieve high CO2 permeability and exceptional CO2/N2 ideal selectivity (CO2 = 14879 barrer, CO2/N2 = 24.3), surpassing the latest 2019 upper bound. That makes MIL-101-HNO3/PIM-1 a potential candidate for the selective removal of CO2 from stack gas and provides new insights into the regulation of the MMMs nanofiller microenvironment. © 2024 Elsevier B.V.

Keyword ：

Carbon dioxide Fillers Organic polymers Gases Organometallics Particle size Filled polymers Negative ions Gas permeable membranes

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Abstract ：

The expandable graphite (EG) modified TiO2 nanocomposites were prepared by the high shear method using the TiO2 nanoparticles (NPs) and EG as precursors, in which the amount of EG doped in TiO2 was 10 wt.%. Followed by the impregnation method, adjusting the pH of the solution to 10, and using the electrostatic adsorption to achieve spatial confinement, the Pt elements were mainly distributed on the exposed TiO2, thus generating the Pt/10EG-TiO2–10 catalyst. The best CO oxidation activity with the excellent resistance to H2O and SO2 was obtained over the Pt/10EG-TiO2–10 catalyst: CO conversion after 36 hr of the reaction was ca. 85% under the harsh condition of 10 vol.% H2O and 100 ppm SO2 at a high gaseous hourly space velocity (GHSV) of 400,000 hr−1. Physicochemical properties of the catalysts were characterized by various techniques. The results showed that the electrostatic adsorption, which riveted the Pt elements mainly on the exposed TiO2 of the support surface, reduced the dispersion of Pt NPs on EG and achieved the effective dispersion of Pt NPs, hence significantly improving CO oxidation activity over the Pt/10EG-TiO2–10 catalyst. The 10 wt.% EG doped in TiO2 caused the TiO2 support to form a more hydrophobic surface, which reduced the adsorption of H2O and SO2 on the catalyst, greatly inhibited deposition of the TiOSO4 and formation of the PtSO4 species as well as suppressed the oxidation of SO2, thus resulting in an improvement in the resistance to H2O and SO2 of the Pt/10EG-TiO2–10 catalyst. © 2023

Keyword ：

Titania supported platinum Electrostatic adsorption CO oxidation Resistance to H2O and SO2 Expandable graphite

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Abstract ：

The combination of dual-main-phase (DMP) (Nd, Ce)-Fe-B magnets and grain boundary diffusion process (GBDP) is currently a research topic for obtaining high-cost performance materials in rare earth permanent magnet fields. The novel structural features of GBDP (Nd, Ce)-Fe-B magnets give a version of different domain reversal processes from those of non-diffused magnets. In this work, the in-situ magnetic domain evolution of the DMP magnets was observed at elevated temperatures, and the temperature demagnetization and coercivity mechanism of the GBDP dual-main-phase (Nd, Ce)-Fe-B magnets are discussed. The results show that the shell composition of different types of grains in DMP magnets is similar, while the magnetic microstructure results indicate the Ce-rich grains tend to demagnetize first. Dy-rich shell with a high anisotropic field caused by GBDP leads to an increase in the nucleation field, which enhances the coercivity. It is found that much more grains exhibit single domain characteristics in the remanent state for GBDP dual-main-phase (Nd, Ce)-Fe-B magnets. In addition, the grains that undergo demagnetization first are Ce-rich or Nd-rich grains, which is different from that of non-diffused magnets. These results were not found in previous studies but can be intuitively characterized from the perspective of magnetic domains in this work, providing a new perspective and understanding of the performance improvement of magnetic materials. © 2024

Keyword ：

Dual-main-phase Rare earth permanent magnet materials Magnetic microstructures Diffused Dy (Nd, Ce)-Fe-B Grain boundary diffusion process (GBDP)

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Abstract ：

This study introduced a novel catalyst, Cu-Fe@CTS (Chitosan)-ATP (attapulgite), which distinguished itself from traditional Fenton-like catalysts by effectively degrading pollutants across a broad pH range. This catalyst achieved impressive degradation rates of 200 mg L−1 of FA (Fulvic acid), reaching 97 % at pH = 3, 96 % at pH = 7, and 95 % at pH = 10. The catalyst's enduring effectiveness, with FA removal rates marginal decrease to 94 % at pH = 3 after ten cycles, showcased its sustained catalytic activity. The underlying mechanism was attributed to a synergistic interaction facilitated by the addition of Cu2+ and Fe3+ into ATP's framework, which generated a M1-O-M2 structure. Experimentation and analysis revealed a dynamic electron transfer mechanism within the M1-O-M2 structure. Moreover, the catalyst proved to be highly effective in treating real wastewater-leachate concentrate, underscoring its potential for environmental remediation across diverse pH conditions. This research laid the groundwork for expanding the pH applicability of catalysts, opening new pathways for advanced environmental clean-up strategies. © 2024 Elsevier B.V.

Keyword ：

Heterogeneous Fenton-like reaction Wide pH range Electron transport Bimetallic Lewis acids

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Abstract ：

Vanadium (V) interlayers of 0.4 mm, 0.8 mm, and 1.2 mm thickness were firstly deposited on the TC4 alloy side using a laser metal deposition (LMD) process, which was then combined with a CuCrZr plate as a composite intermediate layer, for dissimilar laser welding of TC4 titanium alloys to 304 stainless steels (SS) successfully. The effects of different thicknesses of V interlayers on the weld shape, microstructure and mechanical properties of TC4/304SS joints were investigated. The results show that a sound TC4/304SS butt joint with full penetration is successfully obtained using the prepared composite interlayer. The TC4/304SS joint exhibits a maximum ultimate tensile strength (UTS) of 418 MPa and an elongation index (EI) of 15 % with a V layer thickness of 1.2 mm. With the V-layer thickness increasing, the size and content of the V-Cu solid solution in the fusion zone (FZ) on the TC4 alloy side are gradually increased without the formation of intermetallic compounds (IMCs) generated. © 2024 Elsevier Ltd

Keyword ：

Zircaloy Tensile strength Copper alloys Stainless steel Vanadium alloys Titanium alloys Vanadium compounds Vanadium steel Ternary alloys Butt welding Plate metal Chromium alloys

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Silicon-based anodes, utilizing nanosized silicon materials, hold great promise for the next-generation of lithium-ion batteries due to their high capacity and stable expansion. This study aims to address challenges in traditional slurry-coated anodes, such as agglomeration and low adhesive strength, through the application of laser powder bed fusion (LPBF). The process involves fabricating an Al-Si-Cu alloy layer on a Cu foil current collector, followed by dealloying to create a porous Si-Cu anode. Simulated and experimental results demonstrate successful alloy layer formation through optimized laser spot (55 μm) and powder sizes (1–5 μm). Controlled cooling produces primary Si particles ranging from 150 nm to 1 μm. The resulting microstructure enhances electrochemical performance, particularly by tailoring the size of primary Si. The resultant porous Si-Cu anode, featuring uniformly distributed primary Si (200 nm) metallurgically bonded with Cu networks, exhibits an initial coulombic efficiency of 83% and a remarkable capacity retention of 80% after 300 cycles at 2 C. In-situ and ex-situ observations confirm the crucial role of anode architecture in performance enhancement. This study elucidates the influence of the LPBF microstructure on anode performance and broadens the potential application of laser powder bed fusion in battery manufacturing. © 2024

Keyword ：

Copper alloys Anodes Aluminum alloys Porous silicon Silicon alloys Lithium-ion batteries Dealloying Adhesives Microstructure Metal cladding

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As an energy and carbon saving process for nitrogen removal from wastewater, the partial nitrification and denitrification process (PN/D) has been extensively researched. However, achieving stable PN in municipal wastewater has always been challenging. In this study, a gel immobilized PN/D nitrogen removal process (GI-PN/D) was established. A 94d pilot-scale experiment was conducted using real municipal wastewater with an ammonia concentration of 43.5 ± 5.3 mg N/L at a temperature range of 11.3–28.7℃. The nitrogen removal performance and associated pathways, shifts in the microbial community as well as sludge yield were investigated. The results were as follows: the effluent TN and COD were 0.6 ± 0.4 mg/L and 31.1 ± 3.8 mg/L respectively, and the NAR exceeding 95 %. GI-PN/D achieved deep nitrogen removal of municipal wastewater through stable PN without taking any other measures. The primary pathways for nitrogen removal were identified as denitrification, simultaneous nitrification-denitrification, and aerobic denitrification. High-throughput sequencing analysis revealed that the immobilized fillers facilitated the autonomous enrichment of functional bacteria in each reactor, effectively promoting the dominance and stability of the microbial communities. In addition, GI-PN/D had the characteristic of low sludge yield, with an average sludge yield of 0.029 kg SS/kg COD. This study provides an effective technical for nitrogen removal from municipal wastewater through PN. © 2024

Keyword ：

Gel immobilization Sludge yield Autonomous enrichment Deep nitrogen removal Partial nitrification

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