[en] Li–S battery has high theoretical specific capacity and specific energy, but the shuttle effect challenges its commercial application. So many composite materials had been prepared to conquer it. In this research, MCNT/MoS₂/S composite and MCNT/MoS₂/S composite cathode were prepared respectively by a facile hydrothermal method and by melt diffusion method. MoS₂ and MCNT showed uniformly combined together by SEM and TEM. The electrochemical properties of the MCNT/MoS₂/S cathode were carried out on a Gamry electrochemical workstation. The initial capacity arrive 820 mAh·g⁻¹ at 0.1 C, and specific capacities up to ∼460 mAh·g⁻¹ over more than 300 cycles at 0.5 C. The improvement of electrochemical performance due to MoS₂ strongly adsorbing polysulfide and the conductivity network of MCNT. (paper)

[en] The microstructure evolution and oxidation behavior of alloy Ni-13Mo-13Cr-9W-3Fe-3Ti-2Al (alloy K4208), a newly developed Ni-Cr-W-Mo-based wear-resistant superalloy, were investigated by isothermal aging at 900 °C in air. Thermodynamic calculations, microstructure observations, electron probe microanalysis (EPMA), and precise microchemical analysis were used to study the microstructure evolution and oxidation mechanism of alloy K4208. The results showed that alloy K4208 was mainly composed of a P-like phase, M₆C (and M₁₂C) carbide, γ′ phase, μ phase, and γ matrix. During the 900 °C aging, the γ′ phase coarsened into irregular shapes, the M₆C (and M₁₂C) carbide decomposed, and the μ phase dissolved into the matrix, providing abundant Cr, Mo, and W for the growth of the P-like phase. Hence, the relationship between the different phases was established by element redistribution. In addition, the oxidation of alloy K4208 was a diffusion-controlled process, leading to the formation of a stable oxide layer composed of three parts: a thin layer of NiCr₂O₄ spinel located on the outermost side, a continuous Cr₂O₃ layer decorated with TiO₂ in the middle, and an internal Al₂O₃ layer.

[en] Pitting corrosion of high-strength steel 10Ni8CrMoV under square wave polarization (SWP) in simulated deep-sea environment is investigated and the possible mechanism is proposed. The results show that potential perturbation generates periodic intensification effect on both anodic and cathodic processes by frequently breaking the electrode equilibrium state. The intensity of periodic intensification effect essentially depends on the concentration gradient of Fe²⁺ cations at the steel/solution interface which acts as the forced electrochemical oscillator. The concentration gradient and the resulting concentration polarization effect increase periodically with the increase in SWP potential range. The morphology observation of the pitting and electric charge calculation indicate that the periodic intensification effect can promote the initiation and growth of pits by enhancing the anodic dissolution even under cathodic protection, but it is ineffective below the hydrogen evolution potential. The decrease in either upper or lower potential can mitigate anodic dissolution. Through the statistical analysis of pitting size, it is found that the wide potential range tends to activate the metastable pitting formed under hydrostatic pressure, forming densely distributed pitting. Meanwhile, it is more favorable to the formation of fully grown pits with high size dispersion degree when the proportion of electric charge in the anodic process is higher.

[en] This paper analyzes the reactive power characteristics of the doubly-fed induction generator (DFIG) during the emergency off-grid process caused by the crowbar protection action. Since the action of the crowbar is much faster than the stator switching, the DFIG would be running with a short-term squirrel cage asynchronous operation. The mathematical model of the DFIG under above situation was proposed in this paper, based on which detailed analysis was given on reactive power demands during squirrel-cage asynchronous state of the DFIG. It is achieved that the amount of reactive power absorption was associated with the initial operating conditions such as the terminal voltage and speed before disconnection, which can be prescribed as the s-Q characteristic of DFIG. Finally, analysis on the measured data of the wind farm disconnected event verified the validity of the model. (paper)

[en] For the first time, the corrosion behavior of Q235 steel in 1200, 2000 and 3000 m deepwater of South China Sea for 0.5 year was reported in this study. The corrosion morphology and corrosion products properties were investigated using different techniques, such as 3D optical microscope, scanning electron microscope, x-ray diffraction analyzer and electrochemical impedance spectroscopy. The main environmental factors influencing the corrosion rate of Q235 in deep sea were discussed by applying gray relational analysis. The results indicated that uniform thinning occurred after exposure. A large number of tiny pits were distributed under the corrosion products with a two-layer structure. The corrosion rate and average pitting depth of samples exposed at 2000 m were lower than those exposed at 1200 and 3000 m, and the main environmental factors determining the variation of corrosion rate at different depths were temperature and dissolved oxygen concentration. Hydrostatic pressure had slight effect on the corrosion rate of Q235 steel, but promoted the formation of a more uniform corrosion morphology.

[en] Anode-supported solid oxide fuel cells (SOFCs) comprising NiO-samarium-doped ceria (SDC) (Sm_0.2Ce_0.8O_1.9) composite anode, thin tri-layer electrolyte, and La_0.6Sr_0.4Co_0.8Fe_0.2O₃ (LSCF)-La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ (LSGM) composite cathode were fabricated. The thin tri-layer consisting of an 11-μm thick LSGM electrolyte layer and a 12-μm thick La_0.4Ce_0.6O_1.8 (LDC) layer on each side of the LSGM was prepared by centrifugal casting and co-firing technique. The performance of the cells operated with humidified H₂ as fuel and ambient air as oxidant showed a maximum power density of 1.23 W cm^-2 at 800 deg. C. A stability test of about 100 h was carried out and some deterioration of output power was observed, while the open circuit voltage (OCV) kept unchanged. Impedance measurements showed that both the electrolyte ohmic resistance and the electrode polarization increased with time and the latter dominated the degradation

[en] The gas chromatographic retention data of 90 saturated esters obtained isothermally at 150 deg. C on seven stationary phases (SE-30, OV-7, DC-710, OV-25, XE-60, OV-225 and Silar-5CP) are well-correlated with recently introduced Lu index and novel distance-based atom-type DAI topological indices using multiple linear regression (MLR) method. For the retention indices (RI) based on each stationary phase, the correlation coefficient r of the final models is larger than 0.994, and particularly, the decrease in the standard error is within the range of 53.0-64.8% as compared with the simple linear models with Lu index alone. The results indicate the efficiency of these indices in the structure-retention index correlations of complex compounds. The role of each of the molecular size and individual groups in the molecules is illustrated by analyzing the relative or fraction contributions of individual indices. The results also indicate that the molecular size makes a dominant contribution to retention behaviors, while some atomic type or groups have smaller influence dependent on the polarity of the column. The leave-one-out cross-validation demonstrates the final models to be statistically significant and reliable

[en] Highlights: • Hierarchical assembly, Fe doping and Ag loading are used to design ZnO catalyst. • Novel Platycladus orientalis–shaped Ag/Fe-doped ZnO heterostructure is synthesized. • Photocatalytic mechanism promoted synergetically by Fe doping and Ag loading is proposed. • Ag/Fe-doped ZnO exhibited excellent photocatalytic activity and cyclic stability. -- Abstract: The Ag/Fe-doped ZnO composites were designed by controllable intergration of the three strategies of hierarchical assembly, Fe doping, and Ag loading. The 3D Fe-doped ZnO hierarchical nanoflowers were firstly constructed with Platycladus orientalis–shaped petals via a hydrothermal method, and then Ag nanoparticles were anchored on the surface of Fe-doped ZnO nanoflowers through impregnation/reduction of silver nitrate solution. The samples were characterized by using XRD, SEM, TEM, HRTEM, XPS, Raman spectra, BET, UV–vis DRS, PL, EIS, Mott-Schottky plots, and photocurrent response. The results showed that Fe doping increased BET surface area and oxygen vacancies of ZnO, Ag loading produced the LSP absorption at ~530 nm, Fe doping and Ag loading together extended the visible light absorption and facilitated the separation of photogenerated carriers, which favors photocatalytic activity of ZnO. The maximum degradation efficiency of 92.3% for MO was achieved after visible light irradiation for 80 min when the feed atom ratio of Fe to Zn was 1.2% and Ag loading was 4 wt% of Fe-doped ZnO. Four cycle tests had little effect on the morphology and structure of Ag/Fe-doped ZnO, suggesting good cycling stability. The photocatalytic mechanism was elucidated based on the scavenger experiments and energy bands alignment.

[en] Highlights: • The undoped and Fe, Co and Fe-Co doped g-C₃N₄ were successfully prepared by water bath heating and high temperature calcination method. • The doping mechanism and photoelectric properties of undoped and Fe, Co and Fe-Co doped g-C₃N₄ were performed in this work. • The Fe-Co codoped g-C₃N₄ showed better optical properties such as absorption and photoconductivity. • It implies Fe-Co doped g-C₃N₄ has potential application for photovoltaic devices related to ultraviolet and visible light. The Fe, Co and Fe-Co codoped g-C₃N₄ were prepared and constructed by experiment and first principle to study its doping mechanism and photoelectric properties. The results of FTIR, XRD and simulation show the C-N structure of doped g-C₃N₄ stretched and a highly conjugated system is formed, less obvious (0 0 2) preferred orientation may result from the stronger ionic interactions between Fe, Co and adjacent N atoms. UV-DRS and simulation results reveal that Fe-Co codoped g-C₃N₄ has better optical properties such as absorption and photoconductivity due to Fe and Co dopants, as shallow donor defect, make valence band move to lower energy (red shift), which may imply a potential application prospect on some near ultraviolet and visible light optical element.

[en] The objectives of this study were to fabricate porous scaffolds using decellularized meniscus, and to explore a preferable crosslinking condition to enhance mechanical properties of scaffolds. Moreover, the microstructure, porosity, biodegradation and cytotoxicity were also evaluated. EDAC or GTA in different concentration was used to crosslink scaffolds. FTIR demonstrated functional groups change in crosslinking process. SEM photography showed that crosslinked scaffolds had blurry edges, which resulted scaffolds crosslinked by 1.2 mol/l EDAC had smaller porosity than other groups. The structure change enhanced antidegradation property. After immersing in enzyme solution for 96 h, scaffolds crosslinked by GTA and EDAC could maintain their mass > 70% and 80%. Most importantly, mechanical properties of crosslinked scaffolds were also improved. Uncrosslinked Scaffolds had only 0.49 kPa in compression modulus and 12.81 kPa in tensile modulus. The compression and tensile modulus of scaffolds crosslinked by 1.0% GTA were 1.42 and 567.44 kPa respectively. The same value of scaffolds crosslinked by 1.2 mol/l EDAC were 1.49 and 532.50 kPa. Scaffolds crosslinked by 1.0% and 2.5% GTA were toxic to cells, while EDAC groups showed no cytotoxicity. Chondrocytes could proliferate and infiltrate within scaffolds after seeding. Overall, 1.2 mol/l EDAC was a preferable crosslinking condition. - Highlights: • Porous meniscus scaffolds were fabricated using decellularized meniscus tissue. • Mechanical properties of meniscus scaffolds were enhanced by chemical crosslinking. • The crosslinked scaffold showed enhanced anti-degradation properties. • Chondrocytes could infiltrate and proliferate within crosslinked scaffolds.