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Heterostructures show great potential in energy storage due to their multipurpose structures and function. Recently, two-dimensional (2D) graphene has been widely regarded as an excellent substrate for active materials due to its large specific surface area and superior electrical conductivity. However, it is prone to self-aggregation during charging and discharging, which limits its electrochemical performance. To address the graphene agglomeration problem, we interspersed polypyrrole carbon nanotubes between the graphene cavities and designed three-dimensional (3D)-heterostructures of ZnMn2O4@rGO-polypyrrole carbon nanotubes (ZMO@G-PNTs), which demonstrated a high rate and cyclic stability in lithium-ion capacitors (LICs). Furthermore, the 3D porous structure provided more surface capacity contribution than 2D graphene, ultimately resulting in a better stability (333 mAh g-1 after 1000 cycles at 1 A g-1) and high rate capacity (208 mAh g-1 at 5 A g-1). Also, the mechanism of performance difference between ZMO@G-PNTs and ZMO@G was investigated in detail. Moreover, LICs built from ZMO@G-PNTs as an anode and activated carbon as a cathode showed an energy density of 149.3 Wh kg-1 and a power density of 15 kW kg-1 and cycling stability with a capacity retention of 61.5% after 9000 cycles.

Carbonate, tight sandstone, and shale reservoirs have many pore types, and the relationship between the porosity and elastic parameters is extremely discrete due to the complex pore shape. This paper presents a method for predicting reservoir pore types based on pore shape substitution. The pore shape substitution allows for accurately characterizing the changes in the elastic properties of the rock with the changes in pore shape, assuming there are no changes in terms of minerals, porosity, or fluids. By employing a multiple-porosity variable critical porosity model, the effective pore aspect ratio could be inverted from the velocities of the rock. To perform pore shape substitution, we could replace the effective pore aspect ratio with another pore aspect ratio or increase/decrease the volume content of different pore shapes. The reservoir pore types could be evaluated by comparing the differences in the reservoir velocities before and after the substitution of the pore shape. The test results pertaining to the theoretical model and the well logging data indicated that the pore shape substitution method could be applied to characterize pore types in terms of separating the effects of the pore shapes from the effects of the minerals, porosity, or fluids on the velocities.

Beyond reasonable designing catalysts, the optimization of preparing air cathode has far-reaching implications for the development of Zinc-air batteries. In this study, the effect of Polytetrafluoroethylene (PTFE) in current collecting layer on the performance of Zinc-air battery was investigated. The results showed that as the polytetrafluoroethylene (PTFE) content and heat treatment temperature changed, the hydrophobicity and porosity of current collecting layer also changed, thereby affecting the performance of air cathode. The air cathode assembled with PTFE-3-300 possessed an excellent electrochemical performance, which was prepared by brushing PTFE and acetylene black (wherein the mass ratio of them is 18:5) on current collecting layer and then heating at 300 °C. The obtained air cathode displayed relatively small polarization loss and excellent rate performance, showing a polarization potential of - 0.405 V vs. Hg/HgO at 100 mA cm−2 and the voltage retention of 94.47% from 5 to 20 mA cm−2. Besides, the air cathode displayed excellent discharge stability maintaining average potential 1.3249 V for 100 h. Based on this work, a detailed understanding of the relationship of PTFE and current collecting layer can be achieved to improve the electrode design, architecture and fabrication.

Potassium-ion capacitors (KICs) have received a surge of interest because of their higher reserves and lower costs of potassium than lithium. However, the cycle performance and capacity of potassiu...

Sluggish kinetics and limited reversible capacity present two major challenges for layered titanates to achieve satisfactory sodium-ion storage performance at subzero-temperatures (subzero-T). To f...

Development of high-efficiency non-noble metal materials to substitute Pt-based catalysts for oxygen reduction reactions is crucial in the commercial viability of Zn-air batteries technology. Nitrogen doped carbons (NDCs) are highly appealing as promising candidates. This study reports a facile molten salt (MS) method to synthesize aerogel-like nitrogen doped carbon (NDC-MS). The eutectic mixture acting as combined solvent and porogen leads to the obtained porous materials with extremely large surface area (1548.6 m2 g−1) and relatively high pore volume. The unique aerogel-like structure with hierarchical structure, increased catalytic active sits, extended surface area and large pore volume is beneficial for enhancing oxygen reduction reaction (ORR) performance. The resultant NDC-MS displays a superb ORR catalytic activity with high half-wave potential of 0.88 V, which is one of the most effective figures in previous literature of metal-free catalysts. The superb ORR performance can also be evaluated by Zn–air batteries with satisfactory power density and long-term operation stability. Therefore, such an efficient and green synthetic strategy can open up a new avenue for a wide range of commercial application of heteroatom doped carbon materials in advanced energy technologies.

The catalyst in the oxygen electrode is the core component of the aqueous metal-air battery, which plays a vital role in the determination of the open circuit potential, energy density, and cycle life of the battery. For rechargeable aqueous metal-air batteries, the catalyst should have both good oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic performance. Compared with precious metal catalysts, non-precious metal materials have more advantages in terms of abundant resource reserves and low prices. Over the past few years, great efforts have been made in the development of non-precious metal bifunctional catalysts. This review selectively evaluates the advantages, disadvantages and development status of recent advanced materials including pure carbon materials, carbon-based metal materials and carbon-free materials as bifunctional oxygen catalysts. Preliminary improvement strategies are formulated to make up for the deficiency of each material. The development prospects and challenges facing bifunctional catalysts in the future are also discussed.

Non-noble metal materials are regarded as the most promising catalysts for the oxygen reduction reaction (ORR) to overcome the inherent defects of Pt-based catalysts, like high cost, limited availability and insufficient stability. Here, we fabricate sandwich-like Co encapsulated nitrogen doped carbon polyhedron/graphene (s-Co@NCP/rGO) via a facile and scalable strategy by loading Co-based zeolitic imidazolate framework (ZIF-67) and graphene oxide (GO) layers individually on a polyurethane (PU) sponge template. The 3D sandwich structure is maintained with the assistance of the sponge template, which promotes the uniform dispersion of ZIF-67-derived Co embedded nitrogen doped carbon polyhedra (Co@NCP) and prevents the graphene plates from agglomerating during the annealing process. The final product demonstrates considerable catalytic performance for the ORR with a half-wave potential of 0.85 V, preferable stability and increased poisoning tolerance by comparison to 20 wt% Pt/C, which stems from the 3D sandwich-like structure, N/Co-doping effect, large accessible surface area and hierarchical porous structures. The excellent ORR performance of the catalysts means that they can be utilised in a Zn-air battery as cathode catalysts. During such a demonstration, s-Co@NCP/rGO shows a high open-circuit voltage of 1.466 V, remarkable long-term durability and an outstanding peak power density of 186 mV cm-2, which shows its high potential as a prospective alternative for widespread practical application in the field of non-noble metal ORR catalysts.

Nowadays, Zn-air batteries have been widely applied in miniature electronic devices and power stations. However, it is imperative but challenging to synthesize efficient non-precious metal electrocatalysts for popularizing application of Zn-air batteries. Herein, the three-dimensional porous Co@Co-NPC is prepared by doping P into flower-like Co/Zn-MOF-derived Co-N-C during the carbonization process. The obtained 3D-Co@Co-NPC possesses an excellent catalytic activity, showing a half-wave potential of 0.872 V for ORR and potential of 1.692 V at 10 mA cm−2 for OER. When employed as air-cathode catalyst in Zn-air battery, 3D-Co@Co-NPC shows a high power density of 182.5 mW cm−2 and a high capacity of 764 mAh g−1. Besides, it displays an excellent charging-discharging cycle stability (over 90 h). The outstanding ORR/OER performance of 3D-Co@Co-NPC are mainly attributed to the doping of P element, which can tune the electronic structure of Co-N-C matrix. The pickling experiment proves that Co nanoparticle can make contribution to ORR/OER activity.

To meet the need of high-speed steel roll grinding, a hydrostatic lubrication system for high-speed precision roller grinding head is designed and the dynamic performance of the system is simulated and analyzed in this study. The hydrostatic lubrication system was designed according to the lubrication characteristics of the eccentric sleeve and thrust bearing of the high-speed precision roller. Then the mathematical models of the main components of the system were established. And according to the schematic diagram of hydrostatic lubrication system, the dynamic performance of the lubrication system at high speed was simulated and tested. The simulation and experiment results show that the lubrication effect of the eccentric sleeve static chambers and thrust bearings is good, and the designed hydrostatic lubrication system is feasible.

Controllable synthesis strategies of the cost-effective and high-active non-noble metal bifunctional electrocatalysts for overall water splitting are imperatively required. Herein, the hierarchical heterostructure CoP3/NiMoO4 nanosheets on Ni foam (CoP3/NiMoO4–NF) are synthesized by hydrothermal, annealing and phosphorization treatment. The synergistic effect between CoP3 and NiMoO4 remarkably promotes the HER intrinsic activity. Moreover, the Ni foam promotes the vertical growth of well-aligned nanosheet arrays, which expose more active sites for HER and OER. The CoP3/NiMoO4–NF-2 (Co/Mo = 1/1) electrocatalyst reveals a low overpotential of 92 mV for HER and 347 mV for OER at 10 mA cm−2 in 1.0 M KOH. Especially, the CoP3/NiMoO4–NF-2 exhibits exceptional performance for overall water splitting which presents a low cell voltage of 1.57 V at 10 mA cm−2, and outstanding durability which could maintain over 12 h. The design strategy and controllable synthesis of the hierarchical heterostructure bifunctional electrocatalyst will be beneficial for efficient overall water splitting.

Recently, high performance energy storage devices are increasingly required in many new fields such as smartphone, pilotless automobile. Lithium-ion capacitors (LICs) have become the promising energy storage devices because of the higher power density, electrostatic capacity and long cycle life. Nevertheless, the limitation of the battery-type anode electrode and the capacitance-type cathode electrode with slow kinetics and low specific surface area leads to the LICs remaining lower energy density in high current density. In this report, a high performance LIC assembled by Mn3O4-graphene coupled with activated polyaniline-derived carbon (APDC) is firstly presented. Mn3O4-G composite material exhibits an outstanding invertible capacity of 489.8 mAh g−1 (at 1 A g−1) in a wide working window (0.01–3 V vs. Li/Li+) with an excellent coulombic efficiency in half cell, which is the highest capacitance reported for Mn3O4 so far. By utilization of Mn3O4-G composite as anode and APDC with the large surface of 1641.9 m2 g−1 as cathode, the assembled LIC of Mn3O4-G//APDC possesses an energy density of 97.2 Wh kg−1 at power density of 62.5 W kg−1, even at a relatively higher power density of 6250 W kg−1, its energy density can retain 5.0 Wh kg−1.

In this work, Polyetherketone cardo (PEK-C) was adopted to improve the mechanical and thermal properties of the typically commercial epoxy resin. The effects of PEK-C on the curing behaviors, the mechanical properties, the phase structures and the thermal properties of the epoxy resin were studied carefully. DSC analysis revealed that adding PEK-C into the epoxy resin facilitated the curing reaction by reducing the activation energy. In addition, the existence of the PEK-C also lowered the reacting enthalpy of the epoxy resin. The results of the mechanical properties of the cured PEK-C/epoxy composites indicated a 61%, 16%, 237% and 164% enhancement in tensile strength , flexural strength , impact strength and fracture toughness, respectively, which could be ascribed to the representative phase structures of the composites. Reaction induced phase separation was clearly observed in the PEK-C/epoxy composites during the curing of the epoxy resin, presenting uniformly dispersed particles, bicontinuous and phase inverted structures accompanied with the increase of the PEK-C content, as evident from the SEM images. The glass transition temperatures ( Tg) and decomposition temperatures were found to be enhanced obviously, hinting that the thermal stabilities of the epoxy resin were also distinctively improved due to the addition of PEK-C.

Ti-based compounds are considered as attractive anode materials for sodium-ion capacitors (SICs) due to their favorable safety and stability. However, achieving more Na+ intercalated sites and fast sodiation kinetics in Ti-based anodes is still challenging. Herein, a facile strategy to promote the electrochemical properties of H-titanates by regulating their electronic structure and Na+ diffusion kinetics through thermal-induced interlayer defect engineering is developed. The targeted distorted quasi-layered H-titanate (Q-LT) with abundant interlayer defects exhibits superfast and stable cycle performance (97% capacity retention after 10,000 cycles at 25 C) in Na-ion half-cells. Applied in the high-working voltage (1.5–4.5 V) SICs as additive anodes, high energy density (124 Wh kg−1) and competitive cycle stability (88% capacity retained after 5000 fast cycles) are achieved. The thermal-induced structure evolution in layered H-titanate has been probed by in-situ X-ray diffraction. First-principles density functional theory calculations demonstrate that the Q-LT is equipped with lower coordinate Ti-O polyhedral, higher delocalized Ti-O environment, narrowed band gap and reduced Na+ migration energies; bond valence sum maps expose the continuous Na+ diffusion pathways within the interlayer of Q-LT. This work may offer a conceptual advance in the understanding of the structure-function-performance relationship of titanates for energy storage.

A new type wear block made of medium carbon low alloy steel was designed to improve the service of a centrifugal crusher. A reasonable casting technology was chosen and ViewCast software was used t...

Multiple active constituents of heterostructured catalysts could form moderate hydrogen binding strength on the surface, which is expected to solve the inefficient issue of hydrogen evolution reaction (HER). Herein, hydrothermal followed by carbon deposition treatment is introduced to design hierarchical heterostructured Mo2C/Mo3Co3C bouquet-like nanowire arrays on Ni foam (Mo2C/Mo3Co3C-NF), and bring abundant Mo2C-Mo3Co3C interfaces for synergetic electrocatalysis. The addition of Co modifies the electronic structure of the resultant catalysts, and the HER intrinsic activity has been remarkably promoted. Additionally, the 3D Ni foam acts as a current collector that facilitates the directional growth of the active phases, and the exposure of more active sites for hydrogen evolution reaction. As expected, the Mo2C/Mo3Co3C-NF-2 (the molar ratio of Co/Mo is 2/4) catalyst electrode exhibits a low onset overpotential of 24 mV and achieves an overpotential of 87 mV at the current density of 10 mA cm–2 in 1 M KO...

The microscopic surface plays a crucial impact on catalytic activity. Herein, the rough-surfaced chain-like palladium nanowires with many steps and inflections are successfully synthesized by a simple one-step reduction by sodium borohydride. The mechanism of bromide ions adsorbing and the oxygen etching to control the growth of chain-like nanowires is investigated. Furthermore, the effect of the pH values of system on the microscopic surface of palladium nanowires, especially on the roughness, is discussed in depth. The nanowires prepared at pH = 11 exhibit rougher surfaces with a diameter of 10–11 nm, and the relevant catalyst has higher electrochemical active area and excellent electrocatalytic performance for oxygen reduction reaction (ORR). Its half-wave potential in 0.5 mol L−1 H2SO4 solution is 80 mV more positive than Pd nanoparticles, slightly negative than Pt/C and the half-wave potential in 0.1 mol L−1 KOH solution is 50 mV more positive than the Pd nanoparticles, and is almost the same as Pt/C. The research result reported here will have important implications for designing palladium-based catalysts to increase their electrocatalytic ability.

In this paper, a liquid-phase sintering method was developed by combining in-situ reaction method with slurry method to prepare HfB2-MoSi2-SiC coatings with controllable composition, content and thickness. The effect of MoSi2 content on the oxidation protection behavior of HfB2-MoSi2-SiC composite coating under dynamic aerobic environment at room temperature ~ 1500 ℃ and static constant temperature air at 1500 ℃ was studied, the relative oxygen permeability was used to characterize the oxidation resistance of the coating. The results of dynamic oxidation test at room temperature ~ 1500 ℃ showed that the initial oxidation weight loss of the samples was delayed from 775 ℃ to 821 ℃, and the maximum weight loss rate decreased from 0.9×10−3 mg·cm−2·s−1 to 0.2×10−3 mg·cm−2·s−1 with the increase of MoSi2 content, the lowest relative oxygen permeability was reduced to 12.2%, resulting in the weight loss of the sample from 1.8% to 0.21%. In this paper, the mechanism of MoSi2 enhancing the ability of oxidation protection of the coating is revealed. With the increase of MoSi2 content, the amount of SiO2 glass phase in the coating is increased, and the dispersion of Hf-oxide on the coating surface is promoted, thus, the Hf-Si-O compound glass layer with higher stability can be formed, and the weight loss rate of the sample reduced from 0.46% to 0.08% after 200 h oxidation at 1500 ℃ in constant temperature air.

Summary The sluggish oxygen reduction reaction (ORR) has becoming the bottleneck of largescale implementation of proton exchange membrane fuel cells. However, when it comes to the ORR activity assessing of platinum group metals (PGMs) with rotating disk electrode, the corresponding potential conversion vs. reversible hydrogen electrode, test protocols, and activity calculation processes are still in chaos in many published literatures. In this work, two standard calculation processes for PGM ORR activities are demonstrated, followed by a specification for the usage of reference electrodes. Then a 4-fold discrepancy in ORR activities obtained via different test protocols is found for the same Pt/C, and an average adsorption model and the “coverage effects” are proposed to illustrate the hysteresis loop between negative and positive-going ORR polarization plots. Finally, four motions over appropriate assessment of PGM ORR activity are emphasized, hoping to bring a fair communication platform for researchers from different groups., Graphical abstract, Highlights • Reference electrode usage specifications and mechanisms are illustrated • A 4-fold ORR activity discrepancy of Pt/C is found for different test protocols • An average adsorption model with self-consistent iterative algorithm is found • The coverage effects derived from the model can interpret the ORR hysteresis loop, Chemical reaction; Catalysis; Energy systems; Energy storage

Mn and N codoped carbon materials are proposed as one of the most promising catalysts for the oxygen reduction reaction (ORR) but still confront a lot of challenges to replace Pt. Herein, a novel gas-phase migration strategy is developed for the scale synthesis of atomically dispersed Mn and N codoped carbon materials (g-SA-Mn) as highly effective ORR catalysts. Porous zeolitic imidazolate frameworks serve as the appropriate support for the trapping and anchoring of Mn-containing gaseous species and the synchronous high-temperature pyrolysis process results in the generation of atomically dispersed Mn-N

Expansive soils located in permafrost and seasonal frozen regions can easily suffer from the action of frost heaving and repeated freezing–thawing. When exposed to freeze–thaw (F–T) cycles, it may pose risk to civil engineering structures and thus causes heavy economic losses. In this study, a series of cylindrical expansive soil specimens were compacted at three different molding water contents (15%, 20% and 23%) and then subjected to a maximum of 12 closed–system F–T cycles. Besides, selected specimens compacted at the optimum water content were also tested under cyclic freezing–thawing with varying freezing temperatures (−5 °C, −10 °C and −20 °C). After each cycle of F–T, volume changes were measured and unconfined compression testing was also performed to estimate stress–strain behavior, resilient modulus and failure strength. Moreover, meso–structural analysis was conducted by using a simple optical test system to quantitatively extract the surface porosity and the pore orientation degree of expansive soil specimens after different F–T cycles. It is found that: 1) Volume changes for expansive soil specimens with higher and lower saturations present opposite directions and different magnitudes upon freezing, but show a similar trend of volume expansion after thawing. A moderate freezing temperature (i.e. –10 °C, in this study) has the greatest effect on volume changes. 2) Expansive soils tend to exhibit strain–softening behavior under unconfined compression conditions. The resilient modulus and failure strength decrease significantly at the first cycle of F–T and then reduce gradually to a stable value with increasing F–T cycles. The higher molding water content and a moderate freezing temperature will lead to a more pronounced degradation of mechanical behaviors with the F–T cycles. 3) It is suggested from the meso–structural analysis that the internal pores of expansive soils after a sequence of F–T cycles tend to become larger and more uniform, especially for the soil with higher water contents or experienced at a moderate freezing temperature.

Proton exchange membrane（PEM） is a key component of vanadium redox flow battery（VRB）, and its proton/vanadium selectivity plays an important role in the performance of a VRB single cell. Commercially available perfluorosulfonic acid（Nafion） membranes have been widely used due to their excellent proton conductivity and favorable chemical resistance. However, the large pore size micelle channels formed by the pendant sulfonic acid groups lead to the excessive penetration of vanadium ions, which seriously affects the coulombic efficiency（CE） of the single cell and accelerates the self-discharge rate of the battery. Additionally, the expensive cost of Nafion is also an important reason to limit its large-scale application. In this paper, the dense and lowcost hydrocarbon polymer polybenzimidazole（PBI） is used as the matrix material of the PEM, which is doped with phosphotungstic acid（PWA） to acquire excellent proton conductivity, and the intrinsic high resistance of PBI for vanadium ions is helpful to obtain high proton/vanadium selectivity. Considering the enormous water solubility of PWA and its easy leaching from membrane, organic polymer nano-Kevlar fibers（NKFs） are utilized as the anchoring agent of PWA, which achieves good anchoring effect and solves the problem of the poor compatibility between inorganic anchoring agent and the polymer matrix. The formation of PWA functionalized NKFs was characterized by scanning electron microscope（SEM） and Fourier transform infrared（FT-IR） spectroscopy. The anchoring stability of NKFs for PWA was evaluated by UV-Vis spectroscopy. The characterizations including water uptake, swelling ratio, ion exchange capacity, proton conductivity, vanadium ion permeability and ion selectivity were performed to evaluate the basic properties of the membranes. At the same time, the charge-discharge, self-discharge and cycle performance of single cell assembled with the composite membrane and recast Nafion were tested at various current densities from 40 to 100 m A·cm-2. Simple tuning for the filling amount of NKFs@PWA gives the composite membrane superior ion selectivity including an optimal value of 3.26 × 105 S·min·cm-3, which is 8.5 times higher than that of recast Nafion(0.34 × 105 S·min·cm-3). As a result, the VRB single cell assembled with the composite membrane exhibits higher CE and significantly lower self-discharge rate compared with recast Nafion. Typically, the CE of the VRB based on PBI-（NKFs@PWA）-22.5% membrane is 97.31% at 100 mA·cm-2 while the value of recast Nafion is only 90.28%. The open circuit voltage（VOC） holding time above 0.8 V of the single cell assembled with the composite membrane is 95 h, which is about 2.4 times as long as that of recast Nafion-based VRB. The utilization of PBI as a separator for VRB can effectively suppress the penetration of vanadium ions, achieve higher proton/vanadium selectivity and superior battery performance as well as reduce the cost of the PEM, which will play an active role in the promotion of VRB applications.

We report an innovative strategy to prepare the porous N-doped graphene aerogel with an open structure and abundant defects by hydrothermal self-assembly of zeolitic imidazolate framework (ZIF)-8 and graphene oxide. The in-situ hydrothermal restructuring of ZIF-8 on graphene sheets plays a key role in the synthesis of the open structure and the uniform N-doping. The dissolution and restructuring of ZIF-8 on graphene oxide obviously suppress the stacking and reunion of graphene sheets to obtain the continuous macroporous structure. Moreover, the introduction of N and Zn creates the abundant N-doped sites and microporous structure. Its unique structure and composition improve the accessible surface area, the mass transfer diffusion, the dispersion and electronic structure of Pt nanoparticles, further resulting in the high catalytic performance of Pt-based catalyst for methanol oxidation reaction (MOR). Its MOR activity is about 1.8 times of commercial Pt/C, and its long cycling durability is improved by about 18.7% compared with commercial Pt/C. This work renders a promising method by utilizing ZIF-8 derivatives to synthesize the excellent N-doped carbon materials for electrochemical applications.

A novel polybenzimidazole (PBI) proton exchange membrane based on phosphotungstic acid (PWA)-anchored nano-Kevlar fibers (NKFs) has been successfully prepared by solution casting. Employing NKFs instead of frequently used oxide support as anchoring agent has effectively conquered the problem of the poor interface compatibility between the inorganic component and the polymer, resulting in the excellent dispersion of PWA in the matrix and providing favorable conditions for the formation of consecutive proton transport channels. The as-obtained PBI/NKFs@PWA membrane exhibits proton conductivities as high as 0.029 and 0.051 S cm−1 at 20 and 80 °C without extra humidity, respectively. And benefit from the undetectable leakage of PWA, the proton conductivity retention could achieve 93.16% within 500 h. Simultaneously, the methanol barrier property of the hybrid membrane is far beyond Nafion, indicating a membrane selectivity of 12.08 × 104 S (s cm−3), which is 8.21 times higher than that of Nafion 115. The hybrid membrane allowed for sufficient proton conductivity, robust stability, lower methanol permeability, as well as low cost compared with Nafion, shows great potential for direct methanol fuel cell applications.

Al-0.05Ga-0.05Sn-0.05Pb-xMg alloys with different Mg content have been prepared. Electrochemical tests including constant current discharge test, current polarization test, electrochemical impedance spectroscopy (EIS) test, and Tafel test are performed. The surface states of the alloys after constant current discharge were analyzed by scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS). X-ray diffraction (XRD) analysis was carried out. We find that different Mg contents have great influence on discharge performance of aluminum alloy anodes by changing the corrosion behavior. The SEM and XRD show that Mg can influence the distribution of corrosion and change the grain size to improve the discharge performance of aluminum anodes. Al-0.05Ga-0.05Sn-0.05Pb-0.1Mg shows the best electrochemical performance due to uniform corrosion and proper grain size. At 800 mA cm−2 constant current discharge, the potential of the aluminum anode can reach − 1.54 V (vs Hg/HgO), and the utilization ratio is over 98%.

Nitrogen-doped three-dimensional porous graphene frameworks (NGAs) are fabricated through a unique strategy of adopting the supramolecular assembly-assisted method with GO as building block, and supramolecular aggregate of self-assembled melamine and cyanuric acid as not only a “spacer” to suppress the re-stacking of graphene nanosheets but a self-sacrificial pore-forming agent as well as a nitrogen source leading to simultaneous N-doping. Supramolecular aggregates function as the structure-directing agent playing a vital role in generating the loose porous and free-stacking structure and guiding the formation of unique 3D architecture. The resulting metal-free NGA products possess high specific surface area, porous structure and free-stacking properties, and exhibit enhanced ORR performance in terms of positive half-wave potential which is only ∼43 mV lower than that of a commercial Pt/C, four-electron-transfer process, good durability and outstanding methanol poisoning tolerance. Besides, it also performs as a good support for Pt particles. Consequently, Pt/NGA catalyst displays impressive catalytic activity and stability towards efficient methanol electrooxidation reaction. This simple and robust synthetic strategy of 3D N-doped graphene has put forward a new prospect for rational synthesis of heteroatoms doped carbon materials for sustainable energy conversion applications.

The 3D N-doped graphene supported metal oxide has been synthesized as the sulfur host of Lithium-sulfur battery. A simple method of nanoparticles in-situ grown in aqueous solution is introduced. The SEM images and XRD spectra confirmed that nanoparticles with few tens of nanometers distributed on the surface of graphene sheet. The compound electrode showed an initial specific capacity of 1518 mA h g−1 at 0.2 C with a sulfur utilization of 90%. During 700 cycles, the capacity decay was only 0.03% per cycle. Even at a high rate of 2 C, the specific capacity can still be achieved 595 mA h g−1. The visual charge-discharge test showed that the composite electrode had strong adsorption effect on polysulfide vividly.

A supramolecular polymerization-assisted approach is proposed for the preparation of 1D hollow nitrogen-doped carbon tubes (h-NCTs) as an advanced support material to immobilize metal nanoparticles...

The kinetics of gas hydrate formation and decomposition at the gas–water interface are of crucial importance to the application of the hydrate-based technique and the gas recovery process from marine sediments. Herein, the behaviors of in situ CO2 hydrate growth and dissociation at the interface of liquid CO2 and water were observed using magnetic resonance imaging. The results indicated that the growth of the hydrate film was primarily controlled by the mass transfer of CO2 into the water phase. Notably, the stepwise depressurization beyond the equilibrium pressure was found to facilitate the thickening of hydrate films as a result of the enhanced evolution of dissolved gas out of water for hydrate formation. The addition of surfactants (sodium dodecyl sulfate) could contribute to a shorter induction time and a thinner hydrate film. The dissolution of the gas molecule and bubbles in the water phase were suggested as the crucial factor impacting the thickening of CO2 hydrate films.

We describe the design, fabrication, and evaluation of a new on-wafer four port device for measurement the complex permittivity of materials over the continuous frequency range from 1.5 GHz to 2.75 GHz. The proposed device consists of two 3dB directional coupler connected through two U-shaped slot line sections with the same length. This method can afford high accurate measurement results by only two measurements of scattering parameters. One measurement is for the empty device and the other for the material under test loaded on U-shape slot-line of the device. Additionally, we compute the complex permittivity of the materials under test from the measured scattering parameters. Our measurements show excellent agreement with transmission methods.

Titanium nitride (TiN) as catalyst support has a very good application prospect due to its chemical stability, electrical conductivity and the metal-support interaction. But it is difficult to synthesize nano-TiN with the uniform dispersion by a simple method. This paper proposes a novel and easy strategy to address the problem. The mesoporous g-C3N4 has been synthesized and used as both nano-reactor and nitrogen source for the synthesis of nano-TiN evenly dispersed onto Vulcan XC-72. The uniform dispersion of nano-TiN is conducive to depositing and anchoring the PtRu nanoparticles, further increasing the long-time catalytic durability. Moreover, the electronic effect of TiN obviously improves the catalytic activity and the adsorbed CO tolerance ability of PtRu catalysts for methanol oxidation. Compared with the PtRu/C catalyst, the activity of PtRu/C-TiN for methanol oxidation has been increased by 47.3%. Meanwhile, its durability has been improved by 6.5% after 1000 cycles. In addition, this novel and easy method can be generalized to the synthesis of other nano-size nitrides. The applications of nano-size nitrides modified carbon black in other fields are also expected in the future.

Ni-rich cathode materials always suffer from serious side reaction and irreversible phase transition leading to capacity fading and thermal instability, which could be improved by surface coating and elemental doping. However, it is difficult and cumbersome to carry on the coating and doping at the same time. Herein, a facile method of bi-functional Ti modification has been employed on LiNi0.8Co0.15Al0.05O2 to enhance surface and structural stability via heterogeneous layer coating and bulk doping. The mechanism and synergistic effect of Ti modification has been investigated by XRD, XPS, SEM, TEM and the half-cell test in details. The existence of Ti occupancy in Ni site of the transition metal layer has been confirmed. Besides, a 22 nm heterogeneous layer has been detected on the particle surface and the composition has been analyzed. Ti bulk doping can reduce the cation mixing degree, and stabilize the lattice due to the pillar effect and charge compensation. Moreover, the heterogeneous coating layer could protect the cathode particles from hydrofluoric acid attack and reduce the decomposition of electrolyte during cycling. With the synergistic effects of heterogeneous layer coating and bulk doping, NCA-T2 exhibits the highest initial capacities of 162.9 and 182.4 mAh·g−1 at 1C and 0.1C, and the discharge capacity retentions of 1C cycling reach 85.0% after 200 cycles.

For the first time, a supramolecular template-derived synthesis approach is reported to fabricate 1D nitrogen-doped hollow carbon tubes (h-NCTs) with a hierarchical micro/mesoporous structure. A melamine cyanurate supramolecular assembly is used as the tubular-structure guiding template and nitrogen source, endowing the obtained h-NCTs catalyst with proliferative catalytic active sites, a high surface area as well as a well-defined multiscale pore system. The sample prepared at 900 °C (h-NCT-900) displays an exceptional half-wave potential of 0.86 V versus RHE, which is one of the best values recorded in the literature for a metal-free electrocatalyst.

Three kinds of FeCrAl fibers with different pore sizes were prepared by design, fabrication, sintering and repression. The pore size, resistance and capacity were tested. The results show that the initial resistance and efficiency is reduced, while the capacity is increased with the increase of pore size. The pulse-jet cleaning of fibers were operated based on VDI3926 standard at different face velocity and cleaning pressure. The result indicates sample 3 with 22 μm fiber diameter have the longest cleaning lifespan. The four stages of the standard VDI3926 are completed in the face velocity of 0.06 m/s, the dust concentration of 2 g/m3 and pressure drop prior to pulse-jet cleaning is 3500 Pa. The sample increment weighing reaches 12.31 g, the average efficiency is as high as 98.5% and consumed time is 3 h after 30 times artificial aging. The fiber with 22 μm diameter shows the longest lifespan.

The 3D N-doped graphene nanomesh foam (3DNGF) has been synthesized as the Lithium-sulfur battery cathode material for the first time. A method of in situ doping nitrogen and meanwhile etching graphene layer is introduced. The BET result shows the 3DNGF has a large specific surface area more than traditional three-dimensional graphene. Transmission electron microscopy (TEM) observation and Raman spectra confirm the nanoholes on the graphene. The 3DNGF/S composite exhibits an initial discharge capacity of 1134 mAh g −1 at 0.2C in the first cycle with the sulfur utilization of 67%. The electrode reserves a specific capacity of 578 mAh g −1 after 500 cycles at 0.5C, with a capacity decay of 0.06% per cycle. Its specific capacity at 2C can still reach to 729 mAh g −1 , indicating the good rate performance.

The three-dimensional (3D) hybrid aerogels built from graphene and polypyrrole-derived nitrogen-doped carbon nanotubes (G-NCNTs) are synthesized by facile hydrothermal and heat treatment process using graphite oxide (GO) and polypyrrole nanotubes (PNTs) as precursors. The 3D G-NCNTs hybrid aerogels, in which the NCNTs are dispersed homogeneously in the graphene sheets, are designed to efficiently support Pt nanoparticles. Comparing with 3D graphene (GA), the 3D G-NCNTs supported Pt-based catalyst possesses improved electrocatalysis activity and stability toward methanol oxidation reaction (MOR). The mass activity of Pt/G-NCNTs-1/2 catalyst is 0.74 A mg−1Pt, which is 1.4 times that of the Pt/GA catalyst (0.54 A mg−1Pt). In addition, the retention rate after 1000 cycles for Pt/G-NCNTs-1/2 catalyst is as high as 82.4%, obviously superior to 68.5% of Pt/GA catalyst. The enhanced electrochemical performance is ascribed to the synergistic effect of GA and NCNTs. The introduction of NCNTs can uniformly disperse and strongly anchor Pt nanoparticles due to the increase in nitrogen active sites. Moreover, the NCNTs introduced into GA may prevent the restacking of graphene sheets, and provide a large accessible surface area for better dispersing Pt nanoparticles and transporting reactants and products.

Powder metallurgy (PM) Ti–22Al–24Nb–0.5Mo (at.%) alloys were prepared by hot isostatic pressing. In order to study the feasibility of PM + ring rolling combined process for preparing Ti2AlNb rings, thermal mechanical simulation tests of PM Ti2AlNb alloys were conducted and two rectangular PM rings (150 mm in height, 75 mm in thickness, 350 mm in external diameter) were rolled as a validation experiment. Experimental results show that the flow stress of Ti2AlNb alloys exhibited a significant drop at the very beginning of the deformation (true strain

As the most common structure of chitin, α-chitin is insoluble in common aquatic and organic solvents, and is very difficult to be processed due to its highly ordered crystalline structure and the large number of intermolecular and intramolecular hydrogen bonds. Amorphization of α-chitin has been proved to be a valid measure for improving its subsequent functionalization efficiency and depolymerization yield. In this study, superfine grinding (SFG) was introduced to make α-chitin amorphous, and it was found that SFG effectively reduced the particle size, changed the microstructure, and significantly reduced the crystallinity of α-chitin. Chitin with crystallinity as low as 8.39 % was obtained after 60 min of SFG treatment, and the amorphous chitin became readily dissolved in 10 % NaOH solution after one round of freezing-thawing process. As continuous manner could be employed, SFG might be a powerful and efficient method for preparing amorphous chitin to help its processing and modification of various applications.

Repairing bone defects remains challenging in orthopedics. Here, strontium (Sr) alginate hydrogels containing chondroitin sulfate (CS) were fabricated for enhancing bone defects repair. The effects of CS incorporation ratio on the morphology, structure, thermal stability, water uptake and mechanical performance of Sr-CS/alginate hydrogels were also evaluated. Increasing CS incorporation ratio, Sr-CS/alginate hydrogels exhibit decreasing mechanical properties and lower water retention capacity. In vitro results suggest that Sr-CS/alginate hydrogels with higher CS ratio facilitate the proliferation of osteoblasts. Additionally, the osteogenic genes expressions were investigated by real-time quantitative polymerase chain reaction (RT-qPCR). The results reveal that Sr-CS/alginate hydrogels should have positive effects on modulating the osteogenic factors. Moreover, by employing repair femoral cylindrical defects rabbit model, the efficiency of as-fabricated Sr-CS/alginate hydrogels in bone regeneration was evaluated. The animal study suggests that Sr-CS/alginate hydrogel could significantly facilitate bone defects repair and therefore should potentially be useful for osteochondral tissue engineering.

Efficient enhancement of the toughness of epoxy resins has been a bottleneck for expanding their suitability for advanced applications. Here, polysulfone (PSF) was adopted to toughen and modify the epoxy. The influences of PSF on the mechanical and thermal properties of the epoxy resin were systematically studied by optical microscopy, Fourier transform infrared spectrometer (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analyzer (TG), dynamic mechanical thermal analyzer (DMA), mechanical tests and scanning electron microscope (SEM). The dissolution experimental results showed that PSF presents a good compatibility with the epoxy resin and could be well dissolved under controlled conditions. The introduction of PSF was found to promote the curing reaction of the epoxy resin without participating in the curing reaction and changing the curing mechanism as revealed by the FT-IR and DSC studies. The mechanical properties of PSF/epoxy resin blends showed that the fracture toughness and impact strength were significantly improved, which could be attributed to the bicontinuous phase structure of PSF/epoxy blends. Representative phase structures resulted from the reaction induced phase separation process were clearly observed in the PSF/epoxy blends during the curing process of epoxy resin, which presented dispersed particles, bicontinuous and phase inverted structures with the increase of the PSF content. Our work further confirmed that the thermal stability of the PSF/epoxy blends was slightly increased compared to that of the pure epoxy resin, mainly due to the good heat resistance of the PSF component.

Na3V2(PO4)2F3 is a promising cathode candidate for sodium ion batteries due to its high working voltage. However, an “unknown” low-voltage plateau around ~3.3 V lowers its operating voltage and puzzles researchers. Herein, the reasons for its appearance are explored. It is found that the formation of the low-voltage plateau originates from the extra-generated [VO6] induced by the fluorine loss during the synthesis. To enable better performance, a feasible strategy of stabilizing fluorine is proposed to eliminate the low-voltage plateau. It is demonstrated that this strategy can effectively guarantee the existence of fluorine and modulate the local electronic structure of V to maintain [VO4F2] in Na3V2(PO4)2F3 phase, thus eliminating the undesirable plateau and achieving an operating-voltage increase of ~100 mV. Moreover, the enhanced structural stability and kinetics of the optimized Na3V2(PO4)2F3 cathode are confirmed by in-situ XRD. As expected, the Na3V2(PO4)2F3 cathode delivers higher energy density (446.4 Wh kg−1), better rate capability and longer cycling performance (89.2%@30 C after 1000 cycles). Furthermore, its excellent adaptability to wide temperature range (−25 °C–55 °C) and strong competence in Na3V2(PO4)2F3||hard carbon full-cell are verified. These excellent properties further qualify Na3V2(PO4)2F3 as a competitive cathode for sodium ion batteries.

Molybdenum trioxide (MoO3) has been considered an advanced auxiliary support for Pt nanoparticle anchorage due to its excellent activity and stability. Nevertheless, its non-conductivity property still impedes its applications in electrocatalytic fields. Thus, the MoO3 and carbon composite of a nanostructure is synthesized through sintering process and served as an efficient co-support for Pt-based anode catalyst in this paper. The electrochemical measurements demonstrate that Pt/MoO3-C catalyst shows higher catalytic activity and stability than the as-prepared Pt/C. Significantly, it exhibits 1.95 times higher activity and 2.36 times better durability for methanol oxidation when compared with commercial Pt/C. The remarkably enhanced performance of this novel Pt/MoO3-C catalyst for methanol electrooxidation can be ascribed to the abundant Pt nucleation active sites, uniformly dispersed Pt nanoparticles and the strong metal-support interaction between Pt and MoO3-C. These outstanding properties suggest Pt/MoO3-C a promising catalyst for practical application of fuel cell.

The atomically controlled transition of nanohybrids and their effects on charge-carrier dynamics are highly desirable for fundamental studies in photocatalysis. Herein, for the first time, a method combining atomic monodispersity and single-atom alloy was used to prepare a new form of highly efficient silver-based cocatalysts (Ag25 & Pt1Ag24) on graphitic carbon nitride, representing a novel photocatalytic system for hydrogen evolution.

Molybdenum dioxide (MoO2) has been adopted as an advanced auxiliary support material for its outstanding electrical properties to anchor metal nanoparticles (NPs). To overcome the drawback of MoO2 electronic conductivity, a novel hierarchical carbon coated molybdenum dioxide (MoO2@C) nanotube built from ultra-thin nanosheets was utilized as a nanostructured support. Pt NPs were uniformly deposited onto the MoO2@C support and a hierarchical Pt-based anode catalyst was successfully synthesized. Benefitting from several favourable features, including high exposed surface area, short diffusion distance, fast charge transfer and homogeneous Pt NPs dispersion, the Pt/MoO2@C catalyst exhibited an improved activity along with enhanced stability for methanol electrooxidation when compared with that of the Pt/C catalyst. This novel hierarchical structure is helpful for the further applications in hydrogen evolution reaction, supercapacitors and batteries.