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Sodium-ion batteries have been intensely developed as cost-effective alternatives to current lithium-ion batteries for large-scale applications, especially in energy storage systems and low-speed electric transportations. Na3V2O2(PO4)2F (NVOPF), as one particular derivative of sodium vanadium fluorophosphates with excellent ionic conductivity and robust polyanionic structure, has been attractive as a high-energy cathode candidate to exhibit superior sodium storage performance. However, the high-rate and cycling performance of the NVOPF cathode is far away from expectations, owing to its intrinsic poor electronic conductivity. Here, we report a dual-carbon decoration to address this essential issue. Specifically, an amorphous carbon (C) layer is homogeneously coated at the surface of NVOPF particles, coupled with an in situ wrapping of graphitized carbon nanofibers (CNFs) externally, resulting in a heterostructure of dual-carbon coated NVOPF@C/CNFs. Through a post-annealing (PA) treatment, the NVOPF@C/CNF-PA cathode reveals the desired rate capability and cycling stability even under elevated working temperatures. The material can deliver an impressive capacity of 86.7 mA h g−1 at 50C and can also retain 82.5% capacity retention after prolonged 2500 cycles at 5C at 60 °C, which is superior to previously reported NVOPF-based cathode materials with different surface engineering. In situ galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) examinations show that the heterostructured dual-carbon decoration considerably improves the sodium storage kinetics during extraction of the first Na-ion, i.e., overcomes the rate-determining Na-ion diffusion for the NVOPF cathode, which accounts for the ultrafast sodium storage. This work highlights an effective surface engineering protocol that significantly boosts the rate capability of polyanion-type cathodes for fast-charging sodium-ion batteries.

Due to the continuous decomposition of the in situ solid-electrolyte interphase (SEI) between the electrolyte and anodes such as Li metal, Si, MoS2, etc., the low cycling stability has become one of the challenges for practical application of new-type Li-ion batteries (LIBs) with high energy density. Herein, an artificial LiAlO2 SEI is inserted between the in situ SEI and anode to improve the cycling stability of the batteries, through the formation of lattice-matched interfaces between the artificial LiAlO2 and in situ formed SEI components such as LiF, Li2CO3, LiPO2F2, etc. The lattice-matched interfaces can efficiently suppress mechanical and chemical degradation and retain the in situ SEI and consequently the cell stability through cycling. Taking a conversion-type Ni3S2 electrode as a model system, the stabilization mechanism of the in situ SEI is well illustrated and the reversible capacity attenuation of Ni3S2 from the 2nd to 100th cycle can be significantly reduced from 35.8% to 1.2%, in the presence of the lattice-matched interfaces. The proposed strategy is highly effective and inspiring to solve the challenge of in situ SEI decomposition and achieve a stable cycling in LIBs with different electrodes.

Four kinds of alcohol amines were tested to improve the anticorrosion performance of the phosphoric and tannic acid (PTA)-based rust converter. The alcohol amine modified PTA rust converters with the optimum mechanical and functional performances were used to prepare the homogeneous single-component waterborne rust conversion-based paint. The mechanical properties and the long-term corrosion resistance of the synthesized rust converter-based paint were investigated. The results show that alcohol amine modified PTA rust converter can convert the rust layer into a thick passivation film with iron tannate and iron phosphate as the main components, significantly improving the corrosion resistance of the carbon steel. The alcohol amine D modified PTA rust converter (RC-D) showed the best anticorrosion and rust conversion performances. The waterborne rust conversion-based paint can convert the rust layer of steel into a blue-black and relatively flat passivation film layer. The waterborne polymer-based paint containing 10 wt.% RC-D significantly improves the long-term corrosion resistance of the rusty steel and the mechanical property of paint.

The calculation process of the traditional test method of unsaturated clay permeability coefficient is complicated, so a prediction model of unsaturated clay permeability is established. The e-lnp curve is drawn through K0 consolidation test of unsaturated remolded clay. The linear relationship between state variables and soil saturation was found, and the influence of unsaturated clay on soil properties was obtained. According to the adsorption storage mechanism and the position of soil compactness in the coordinate system, the characteristic curve of soil moisture and the prediction model of unsaturated clay permeability were established. The permeability test of unsaturated remolded clay is carried out by using transient profile method, and the results show that the model can well describe the change of permeability of unsaturated clay.

In order to achieve effective diagnosis of insulation state of water-tree aged XLPE cables, this paper investigates the variation of conduction current of water-tree aged cables in the polarization process, and analyzes the asymmetrical interface polarization characteristics. The cable samples with different water tree aging time were taken the PDC test. According to the test results, the conduction current of aged cables extracted from the PDC test emerges a peak value, and this value gets more apparent when deterioration of water-tree aged cables are severer. Analysis shows the polarization process of water-tree aged cables is fast and the depolarization process is slow due to the nonlinear variation of relative dielectric constant and conductivity of water tree region, leading to appearance of the conduction current peak. So this paper presents K value to show the asymmetrical interface polarization characteristics of water-tree aged cables, and diagnose insulation performance of cables.

Ni-rich cathode materials have attracted considerable attention due to the high electrochemical capacities and prominent price advantage, while their extensive applications are still impeded by the poor structure stability induced by the intrinsic Li+/Ni2+ cation mixing and mechanical stress accumulation upon cycling. To address these issues, a typical negative thermal expansion (NTE) material ZrV2O7 (ZVO) is firstly employed as coating layer on LiNi0.6Co0.2Mn0.2O2 (NCM622) particles to promote the electrochemical performances through enhancing the structure stability upon repeated cycling and operating at high temperature. The NCM622@1.0 wt% ZVO sample exhibits excellent cyclability (71.0% capacity retension after 500 cycles under 25 °C and 67.0% capacity retension after 200 cycles under 55 °C) and rate capability (60.7% at 5 C). Further in-situ XRD analysis confirms that the structure stability of NCM622 could be prominently stabilized both under electrochemical and thermal treatments after ZVO decoration. Intensive investigation implies the unique functionalities of ZVO in restraining the stress accumulation and volume expansion, thus contributing to the bulk structure stability and interface compatibility of modified NCM622, besides the traditional effect of surface deposition layers (physical separation between solid electrode/electrolyte and inhibited irreversible surface side reactions).

In order to obtain waterborne two-component polyurethane (WB 2K-PUR) with good mechanical properties as well as excellent corrosion resistance, a series of hydroxyl-based polyurethane (HO-WPU) were synthesized using isophorone diisocyanate (IPDI), dimethylolpropionic acid (DMPA), and different proportions of polyether polyol (PTMEG) and polyester polyol (P1012) in this paper. Then WB 2K-PUR coatings were prepared with water-dispersible isocyanates (WDPI) as curing agent. The influence of the proportion of polyester polyols and polyether polyols in soft segments on coatings properties was studied. The characteristics of the coatings were analyzed by Fourier transform infrared spectroscopy (ATR-IR), contact angle, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and atomic force microscopy (AFM). The results showed that the mechanical properties and corrosion resistance of polyester and polyether polyols with appropriate proportion are improved significantly. The mechanism tended to be that with the addition of polyester, more hydrogen bonds were formed between the molecules, which increased the compactness of the coating as a physical crosslinking point. However, the ester groups have a strong affinity to water molecules, so the hydrophilicity of the coating was increased by excessive polyester polyols, and the shielding effect on the corrosion medium was reduced. With the inclusion of 40 % (g/g) P1012 in polyols, the coating has satisfied comprehensive properties.

A novel kind of low-loss single-mode optical fiber was designed and fabricated, which has superior anti-bending performance and good compatibility with the present optical fibers of constructed networks.

The I-II mixed crack is one of the most common cracks contained in the engineering materials. In this study, the theoretical solutions of the brittle tensile failure capability K J , the tensile strength σ c , and the initial fracture angle θ 0 are developed for the engineering materials containing the mode I-II mixed cracks (the crack angle is β ) under uniaxial tensile stress loading based on the maximum circumferential stress criterion. Additionally, under the same frame and boundary conditions, it is concluded that the preponderant crack angle β is 68.09 which making the cracks are most easy to fail and propagate; the corresponding brittle tensile capability K J is 0.97 K I C , and the tensile strength σ c is σ c =0.97K IC /√pa . Based on the results stated above, it is further concluded that, in the engineering structure design, if the tensile strength of materials σ c is given, the allowed maximum length of cracks a 0 is limited to 0.94 K 2 IC / pσ c 2 , which would provide the theoretical foundations for limiting the maximum length of cracks, and detecting cracks in engineering design. DOI: http://dx.doi.org/10.5755/j01.mech.18.1.1275

Photonic crystal polarization maintaining optical fibers(PC-PMFs) could offer much higher birefringence than conventional PMFs and have many remarkable properties. In this article, the localized function was orthogonalized with another function for the PC-PMFs, so the orthogonal localized functions were got, and the mathematical model of modal birefringence for PC-PMFs was brought forward. What’s more, a mathematical formula of attenuation for PC-PMFs was made, the effecting factors on the attenuation of PC-PMFs were analyzed and the process technologies to decrease the loss of PC-PMFs were also proposed.

A new non-zero-dispersion-shifted fiber design is presented. These fibers, with low dispersion slope of 0.03 ps/nm/sup 2/-km and small negative dispersion from 1530 to 1620 nm, are ideal transmission medium for use in broad band DWDM systems.