BiOBr-based nanocomposite photocatalysts are used for removing the organic pollutants, but their poor adsorption/photocatalytic performances and the low potential for recycling limit their ...application. To solve the issue, herein we report a large-area recyclable CFC/BiOBr/ZIF-67 filter-membrane-shaped photocatalyst prepared by
in situ
growth of BiOBr/ZIF-67 nanocomposites on carbon fiber cloth (CFC). Fabrication process is based on hydrothermal synthesis of BiOBr nanosheets (diameter 0.5–1 μm) on carbon fiber cloth (as substrate material) and then a chemical bath route is used to grow ZIF-67 nanoparticles (diameter 300–600 nm)
in situ
on the surface of CFC/BiOBr. Resulted composite, CFC/BiOBr/ZIF-67, exhibits a high specific surface area (545.82 m
2
g
−1
) and a wide photoabsorption, accompanied by an absorption edge (~ 620 nm). In dark condition, CFC/BiOBr/ZIF-67 adsorbs bisphenol A (BPA) and orange 7 (AO7) within 60 min, respectively with 20.0% and 40.1% efficiency. This level of efficiencies are correspondingly 2.6 and 3.2 times more that of the bare CFC/BiOBr (7.6% for BPA and 12.4% for AO7). Under visible light irradiation, CFC/BiOBr/ZIF-67 can degrade 69.7% of BPA and 96.0% of AO7, in 120 min, which are, respectively, 1.3 and 1.8 times higher than the absorption efficiency of bare CFC/BiOBr (53.2% for BPA, 52.0% for AO7). When CFC/BiOBr/ZIF-67 is used as a filter membrane for photocatalytic removal of pollutants in flowing wastewater (AO7, rate: ~ 1.5 L h
−1
), 92.2% of AO7 can be decomposed after 10 filtering cycles. This study suggests CFC/BiOBr/ZIF-67 as a novel highly functional, recyclable and environmental friendly photo-driven membrane filter for purification and recovery of flowing surface waste waters.
Graphical abstract
To improve the density of SiC ceramic components with complicated shape built by laser sintering (LS), cold isostatic pressing (CIP) and reaction sintering (RS) were incorporated into the process. In ...the process of LS/CIP/RS, Phenol formaldehyde resin (PF)-SiC composite powder was prepared by mechanical mixing and cold coating methods, with an optimized content of PF at 18 wt%. For the purpose of obtaining improved density of the sintered body after final reaction sintering, carbon black was added into the initial mixed powder. The material preparation, LS forming and densification steps were optimized throughout the whole fabrication process. The final sintered SiC bodies with the bending strength of 292 ~ 348 MPa and the density of 2.94–2.98 g cm− 3 were prepared using the PF coated SiC-C composite powder and the LS / CIP / RS process. The study further showed a positive and practical approach to fabricate SiC ceramic parts with complicated shape using additive manufacturing technology.
A reliable method for fabricating zirconia-based all-ceramic teeth by stereolithography with gelcasting was demonstrated. The effects of ZrO2 particle size were studied on the stability and ...rheological properties of the zirconia slurry. The effects of powder properties, slurry solid content and sintering temperature on the properties and microstructure of zirconia were also investigated. The results showed that optimal parameters were: 0.2 µm particle size, solid phase content 37 vol% of zirconia slurry and sintering temperature 1550 °C. Part density was up to 98.6%, flexural strength was 1170 MPa and fracture toughness was 19.0 MPa m1/2. Zirconia-based all-ceramic teeth were finally fabricated based on the optimal parameters by using combined stereolithography with gelcasting.
Two‐dimensional (2D) heterostructured materials, combining the collective advantages of individual building blocks and synergistic properties, have spurred great interest as a new paradigm in ...materials science. The family of 2D transition‐metal carbides and nitrides, MXenes, has emerged as an attractive platform to construct functional materials with enhanced performance for diverse applications. Here, we synthesized 2D MoS2‐on‐MXene heterostructures through in situ sulfidation of Mo2TiC2Tx MXene. The computational results show that MoS2‐on‐MXene heterostructures have metallic properties. Moreover, the presence of MXene leads to enhanced Li and Li2S adsorption during the intercalation and conversion reactions. These characteristics render the as‐prepared MoS2‐on‐MXene heterostructures stable Li‐ion storage performance. This work paves the way to use MXene to construct 2D heterostructures for energy storage applications.
MoS2‐on‐MXene heterostructures were obtained by an in situ sulfidation of Mo2TiC2Tx MXene, which deliver improved Coulombic efficiency and cycling performance for the Li‐ion battery. A computational study shows that the strong Li and Li2S adsorption on 2D heterostructures leads to a stable Li‐ion storage performance.
The structure and Mn(III) concentration of birnessite dictate its reactivity and can be changed by birnessite partial reduction, but effects of pH and reductant/birnessite ratios on the changes by ...reduction remain unclear. We found that the two factors strongly affect the structure of birnessite (δ-MnO2) and its Mn(III) content during its reduction by fulvic acid (FA) at pH 4–8 and FA/solid mass ratios of 0.01–10 under anoxic conditions over 600 h. During the reduction, the structure of δ-MnO2 is increasingly accumulated with both Mn(III) and Mn(II) but much more with Mn(III) at pH 8, whereas the accumulated Mn is mainly Mn(II) with little Mn(III) at pH 4 and 6. Mn(III) accumulation, either in layers or over vacancies, is stronger at higher FA/solid ratios. At FA/solid ratios ≥1 and pH 6 and 8, additional hausmannite and MnOOH phases form. The altered birnessite favorably adsorbs FA because of the structural accumulation of Mn(II, III). Like during microbially mediated oxidative precipitation of birnessite, the dynamic changes during its reduction are ascribed to the birnessite-Mn(II) redox reactions. Our work suggests low reactivity of birnessite coexisting with organic matter and severe decline of its reactivity by partial reduction in alkaline environment.
Abstract Hypersonic vehicles can be affected by incoming hot air. In order to ensure that the power generation turbine blades can operate properly, the fuel in the engine is used to cool the turbine ...blades. In this paper, the heat transfer characteristics of fuel in smooth and 45° ribbed channels under rotating conditions are investigated. Their results show that, unlike the smooth channel, the heat transfer coefficient of the 45° ribbed channel decreases as Ro increases under the combined influence of the rib structure and the physical properties of the fuel. The rib structure disrupts the high-velocity fluid near the trailing surface of the centrifugal section, which promotes doping between the fuels and weakens the effect of the Coriolis force. The Nu increase in ribbed channels ranged from 11.4% to 55.1% compared to smooth channels.
The development of sodium‐ion batteries for large‐scale applications requires the synthesis of electrode materials with high capacity, high initial Coulombic efficiency (ICE), high rate performance, ...long cycle life, and low cost. A rational design of freestanding anode materials is reported for sodium‐ion batteries, consisting of molybdenum disulfide (MoS2) nanosheets aligned vertically on carbon paper derived from paper towel. The hierarchical structure enables sufficient electrode/electrolyte interaction and fast electron transportation. Meanwhile, the unique architecture can minimize the excessive interface between carbon and electrolyte, enabling high ICE. The as‐prepared MoS2@carbon paper composites as freestanding electrodes for sodium‐ion batteries can liberate the traditional electrode manufacturing procedure, thereby reducing the cost of sodium‐ion batteries. The freestanding MoS2@carbon paper electrode exhibits a high reversible capacity, high ICE, good cycling performance, and excellent rate capability. By exploiting in situ Raman spectroscopy, the reversibility of the phase transition from 2H‐MoS2 to 1T‐MoS2 is observed during the sodium‐ion intercalation/deintercalation process. This work is expected to inspire the development of advanced electrode materials for high‐performance sodium‐ion batteries.
MoS2 nanosheets vertically aligned on paper towel derived carbon paper are fabricated as freestanding electrodes for sodium‐ion batteries. Benefiting from the 3D hierarchical structure, the as‐prepared electrodes exhibited high initial Coulombic efficiency, high reversible capacity, high‐rate charging, and a long cycle life. In situ Raman electrospectroscopy is employed to investigate the sodiation/desodiation process.
Micromanipulation and biological, material science, and medical applications often require to control or measure the forces asserted on small objects. Here, we demonstrate for the first time the ...microprinting of a novel fiber-tip-polymer clamped-beam probe micro-force sensor for the examination of biological samples. The proposed sensor consists of two bases, a clamped beam, and a force-sensing probe, which were developed using a femtosecond-laser-induced two-photon polymerization (TPP) technique. Based on the finite element method (FEM), the static performance of the structure was simulated to provide the basis for the structural design. A miniature all-fiber micro-force sensor of this type exhibited an ultrahigh force sensitivity of 1.51 nm μN
, a detection limit of 54.9 nN, and an unambiguous sensor measurement range of ~2.9 mN. The Young's modulus of polydimethylsiloxane, a butterfly feeler, and human hair were successfully measured with the proposed sensor. To the best of our knowledge, this fiber sensor has the smallest force-detection limit in direct contact mode reported to date, comparable to that of an atomic force microscope (AFM). This approach opens new avenues towards the realization of small-footprint AFMs that could be easily adapted for use in outside specialized laboratories. As such, we believe that this device will be beneficial for high-precision biomedical and material science examination, and the proposed fabrication method provides a new route for the next generation of research on complex fiber-integrated polymer devices.
Birnessite, a layered manganese (Mn) oxide, possesses extraordinary metal adsorption and oxidation activity, and thus imposes impacts on many biogeochemical processes. The reactivity of birnessite ...strongly relies on its Mn oxidation state composition (the proportions of Mn II, III and IV), particularly by the Mn(III) proportion. Partial reduction of birnessite transforms birnessite to be Mn(II, III)-rich or to MnOOH and Mn3O4, and thus strongly affects birnessite reactivity. As a metal scavenger, naturally occurring birnessite contains abundant transition and alkali and alkaline earth metal cations in its structure; however, the effects of these metal cations on the partial reduction-induced transformation of birnessite remain unknown. We examined the effects of Zn2+, Mg2+, Ca2+ and ionic strength (controlled by NaCl) on transformation of birnessite (δ-MnO2) and adsorption and oxidation of natural organic matter during partial reduction by fulvic acid (FA) at pH 8 and FA/MnO2 mass ratios (R) of 0.1 or 1 over 600 h under anoxic conditions. Results showed that low ionic strength (0 versus 50 mM NaCl) disfavored FA adsorption, fractionation and oxidation, and thus disfavored formation of Mn(III) in the reacted birnessite. Compared to the 50 mM NaCl system, all divalent cations (Mg2+, Ca2+ and Zn2+) favored FA adsorption and fractionation. Both Mg2+ and Ca2+ significantly enhanced FA oxidation at the early stage but barely at the late stage, whereas Zn2+ strongly suppressed FA oxidation during the entire experimental period. Due to adsorption competition, the presence of the divalent cations resulted in low concentration of Mn(II) adsorbed on vacancies of birnessite. Both Ca2+ and Mg2+ favored Mn(III) production in MnO6 layers, while Zn2+ inhibited it. A small portion of birnessite also transformed to feitknechtite and hausmannite, and the transformation seemed faster in the presence of Ca2+ or Mg2+ than in NaCl solution. In the presence of Zn2+ at the high FA/MnO2 ratio (R = 1), Zn-substituted hansmannite formed extenstively. The formation of Mn(III) in the reacted birnessite can be ascribed to comproportionation between Mn(IV) and Mn(II) adsorbed on either vacancies or edge sites of birnessite. The low-valence Mn oxide phases likely formed via the comproportionation on the edges. The divalent cations affected Mn(III) concentrations of birnessite and formation of the low-valence Mn oxides by competing with Mn(II) for adsorption on edge/vacancy sites or stabilizing Mn(III) in the layers. This work indicates that divalent metal cations strongly influence reactivity and transformation of birnessite in the coupled Mn and carbon redox cycles, and that birnessite containing divalent cations can be an important adsorbent for natural organic carbon in Mn-rich environments. Overall, this study provides insights into the coupled cycles of Mn, trace metals and organic carbon in alkaline and saline environments.
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