Poor intrinsicconductivity has been a principal limiting factor for Na3V2(PO4)3 (NVP) cathode material. Herein, a synergistic strategy of Nb5+ substitution and constructing with three-dimensional rGO lamella is propo...
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Poor intrinsicconductivity has been a principal limiting factor for Na3V2(PO4)3 (NVP) cathode material. Herein, a synergistic strategy of Nb5+ substitution and constructing with three-dimensional rGO lamella is proposed for the first time to optimize the characteristics of NVP. The introduction of Nb5+ generates beneficial carriers and vacancies that optimize the electronic structure of NVP system. Meanwhile, rGO substrate can construct an effective conductive network for the facilitated electronic transportation and form a stabilized SEI layer after cycling to protect the active particles from being collapsed. This double treatment significantly improves the kineticcharacteristics of NVP. Moreover, theoretical calculations indicate that beneficial Nb5+ doping can effectively reduce the band gap between conductive and valence bands, as well as decline the energy barrier of migration for Na+. Notably, the modified Nb0.15-NVP/c@rGO exhibits impressive electrochemical performance. It delivers a capacity of 107.9 mAh g-1 and keeps a value of 102.6 mAh g-1 after 500 cycles at 2c with a high retention of 95.35%. It submits a capacity value of 97.2 mAh g-1 at 20c, 82.92% reversible capacity (80.6 mAh g-1) could be retained after 2000 cycles. Even at 120 and 300c, this material still performs high values of 84.9 and 71.3 mAh g-1, indicating the superior rate capability.
The electrical properties of c/Siccomposites could be used for online and in-situ damage monitoring. To investigate alternating current (Ac) impedance response to damage in the c/Siccomposites, monotonic and increme...
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The electrical properties of c/Siccomposites could be used for online and in-situ damage monitoring. To investigate alternating current (Ac) impedance response to damage in the c/Siccomposites, monotonic and incremental cyclic tensile tests were performed. Both Ac impedance and acoustic emission (AE) techniques were applied to clarify the damage evolution during the tests. The relationship between damage and electrical impedance response was investigated and validated via macroscopic equivalent circuit models. The effects of longitudinal deformation and damage on Ac impedance characteristics, including impedance magnitude and phase angle, were obtained from the models. Results showed that the longitudinal deformation increases the impedance magnitude and the phase angle, and the damage causes the impedance magnitude to increase and the phase angle to decrease. The phase angle is significantly sensitive to fiber breakage, which makes the Ac-based method more suitable for online damage monitoring and final failure warning.
Metallic foam was introduced as an interlayer to improve the performance of the brazed c/ccomposite-titanium alloy joint, and the interfacial microstructure and residual stress of the brazed joint were investigated. ...
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Metallic foam was introduced as an interlayer to improve the performance of the brazed c/ccomposite-titanium alloy joint, and the interfacial microstructure and residual stress of the brazed joint were investigated. compared with the brazed joint without foam, introducing foam interlayer could achieve the uniform bonding interface, and Ag-based solid solution (Ag(s,s)) became more dispersed and smaller in the center of the brazing seam. The thickness of reaction layer close to c/ccomposite side was less than 1 mu m. Some cu-based solid solution (cu(s,s)) was detected, indicating that cu foam still existed after brazing. The residual stress and its distribution calculated by finite element method (FEM), and the residual stress of the brazed joint decreased from 293 MPa to 228 MPa. The introduction of the foam interlayer could obtain homogeneous microstructure, change stress distribution, and improve mechanical properties of the brazed joints.
Aerobiccomposting is an efficient and environmentally friendly method of converting organic waste into nontoxic fertilizers or soil quality enhancers. The quality of the resultant compost depends greatly upon the com...
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Aerobiccomposting is an efficient and environmentally friendly method of converting organic waste into nontoxic fertilizers or soil quality enhancers. The quality of the resultant compost depends greatly upon the composition of the substrate used. The initial carbon-to-nitrogen (c/N) ratio of the substrate is an important factor affecting the composting process. This study elucidated how initial c/N ratios affect the biodegradation of lignocellulose, due to changes in microbial community structure. Four different c/N ratios (20:1, 25:1, 30:1, and 35:1) were examined during a 35-day composting process. The degradation of cellulose, hemicellulose, and lignin was highest (35.7%, 30.6%, and 19.1% respectively) at a 30:1 c/N ratio;after 30 days, the 25:1 c/N ratio ranked second in terms of lignocellulosic degradation rate. The 30:1 c/N ratio further promoted the growth of functional microorganisms responsible for lignocellulose degradation (Luteimonas, Sphingobium, Trichoderma, chaetomium, and Rosellinia), while the growth of dominant pathogenic microbes (Erwinia and Ulocladium) decreased significantly. These results confirm that the initial c/N ratio of the substrate has a significant effect on the microbial community and degradation of organic matter, during walnut branch composting. This process could therefore offer an alternative means of efficient recycling and recovery of waste branches.
A chromium carbide (cr-c) coating in-situ formed on the c/c substrate is successfully prepared by a novel reactive wetting strategy. The interfacial microstructure and oxidation resistance of coated c/ccomposites are...
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A chromium carbide (cr-c) coating in-situ formed on the c/c substrate is successfully prepared by a novel reactive wetting strategy. The interfacial microstructure and oxidation resistance of coated c/ccomposites are investigated in detail. The as-prepared coating mainly consists of cr23c6 and cr7c3, forming a tight joining with the c/c substrate. compared to uncoated samples, the oxidation weight loss of coated c/ccomposites is sub-stantially reduced at high temperatures. Furthermore, the hardness of coated c/ccomposites is significantly increased, enhancing their ability to resist external damage. This reactive wetting strategy can also be used to prepare uniform coatings on c/ccomposites with complex grooved structure or large size. Surprisingly, coated c/ccomposites possess a low weight gain of 3.7% due to thin coating (< 10 mu m), which can maintain their advantage of low density.
Excessive discharge of toxic dyes is detrimental to ecological system and human health. Therefore, an effective photocatalyst must be designed and developed to degrade dyes from wastewater. Herein, a novel one-dimensi...
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Excessive discharge of toxic dyes is detrimental to ecological system and human health. Therefore, an effective photocatalyst must be designed and developed to degrade dyes from wastewater. Herein, a novel one-dimensional (1D) flower-like recoverable ZnFe2O4/c/MnO2/BiOI magneticcomposite photocatalyst was synthesized via electrospinning technique combined with hydrothermal method. The photocatalytic activities of composite photocatalyst were evaluated by degrading methyl orange (MO) and Rhodamine B (RhB) under simulated light irradiation. The efficiency of ZnFe2O4/c/MnO2/BiOI photocatalyst in visible light for 150 min reached 91% (MO) and 120 min reached 94% (RhB). Moreover, the degradation rate of MO still remained 78% after five cycles. The design of 1D magnetic flower-like composite provided a new strategy for preparing photocatalysts possessing excellent photocatalytic efficiency and cyclic stability.
The appropriate assessment of mechanical properties is essential to design ceramic matrix composites. The size effect of strength plays a key role for the material understanding and the transfer from lab-scale samples...
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The appropriate assessment of mechanical properties is essential to design ceramic matrix composites. The size effect of strength plays a key role for the material understanding and the transfer from lab-scale samples to components. In order to investigate the size effect for carbon fiber-reinforced silicon carbon (c/c-Sic) under tensile load, a tensile testing with a minimum of deviation from the pure tensile loading is necessary. Hence, a hybrid edge/face-loading test device for self-alignment and centering of c/c-Sic tensile samples was developed, evaluated and proved to ensure pure tensile load. The mechanical analysis of more than 190 samples with two different cross-sections fabricated from the same material population revealed no significant difference in tensile strength. Although the volume under load was increased from 129 to 154 mm3, the tensile strengths of 162 +/- 7 and 164 +/- 6 MPa did not change. These results are discussed regarding the weakest link and energetic size effect approaches.
Mg-modified c/c-Zrc-Siccomposites were fabricated by a sol-gel process, and the influences of the Mg/(Zr + Si) molar ratio on the microstructure and the mechanical and anti-ablation properties of the composites were ...
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Mg-modified c/c-Zrc-Siccomposites were fabricated by a sol-gel process, and the influences of the Mg/(Zr + Si) molar ratio on the microstructure and the mechanical and anti-ablation properties of the composites were investigated. The results showed that Mg addition not only optimized the distribution of surficial ceramic par-ticles but also improved the flexural strength of composites by inhibiting the ceramization of fibres. Fabricated Mg/(Zr + Si) with a molar ratio of 0.040:0.18 increased the flexural strength of the composite from 173.15 MPa to 331.22 MPa, and the elastic modulus ranged from 11.46 GPa to 23.09 GPa. After plasma flame ablation for 180 s, this composite also showed excellent anti-ablation performance with linear and mass ablation rates of 3.91 mu m/s and-0.23 mg/s, respectively. The superior ablation property was ascribed to the formation of a consecutive oxide layer constructed by a viscous mixed liquid consisting of liquid Mg-Si-O and Zr-Si-O phases and the robust skeleton of the coarsening ZrO2.
Poor conductivity is an obstacle that restricts the development of the electrochemistry performance of Fe3O4. In this work, a novel carbon and nitrogen co-doped ultrafine Fe3O4 nanoparticles (cN-Fe3O4) have been synth...
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Poor conductivity is an obstacle that restricts the development of the electrochemistry performance of Fe3O4. In this work, a novel carbon and nitrogen co-doped ultrafine Fe3O4 nanoparticles (cN-Fe3O4) have been synthesized by triethylamine (TEA) induction and subsequent calcination. The addition of TEA could not only regulate the size of Fe3O4 nanoparticles, but also promote the formation of amorphous carbon layer. Well-designed cN-Fe3O4 heterostructures provide a highly interconnected porous conductive network, large heterogeneous interface area, large specific surface area and a large number of active sites, which greatly improve conductivity and promote electron transfer and electrolyte diffusion. The prepared cN-Fe3O4 electrode exhibits a high specificcapacitance of 399.3 mF cm(-2) and good cycling stability. Meanwhile, cN-Fe3O4 catalyst exhibits excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities, with overpotentials of 136 and 281 mV at the current density of 10 mA cm(-2), respectively. This work provides a promising approach for the design of high-performance anode materials for supercapacitors and provides profound implications for the development of catalysts with bifunctional catalytic activity. (c) 2021 Elsevier Inc. All rights reserved.
c/cx-Sicy composites are one of the most promising counterparts of c/ccomposites as they maintain the mechanical strength of c/ccomposites while providing excellent anti-ablation properties at the same time. This pa...
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c/cx-Sicy composites are one of the most promising counterparts of c/ccomposites as they maintain the mechanical strength of c/ccomposites while providing excellent anti-ablation properties at the same time. This paper reports that the composites could exhibit even better anti ablation properties after heat treatment. The materials were heat-treated and then tested with a thin-blade oxyacetylene torch without the protection of any coatings. The 1600 degrees c heat-treated thin-blade specimen could sustain the ablation of the oxyacetylene torch with a temperature of 1776 degrees c (80 degrees c higher than the original material without heat treatment) and a lower liner ablation rate (1.31 mu m/s) than the original material (1.66 mu m/s). An extreme ablation test was also conducted at around 2400 degrees c, and the 1600 degrees c heat-treated specimen exhibited a lower linear ablation rate (13 mu m/s) than the original specimen (47 mu m/s). The influence of the heat treatment on the crystallinity of the matrix is studied with the additional help of Raman spectroscopy and XPS. The ablation mechanism is discussed in detail, and the fluent condition of the thin-blade specimen is simulated. The paper also reports a different ablation behavior of the 1600 degrees c heat-treated specimen from the material without heat treatment to explain their excellent ablation property.
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