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The structure of current collectors has significant effects on the performance of a lithium-ion battery (LIB). In this study, we use copper fiber felts made by multi-tooth cutting and high-temperature solid-phase sintering as the current collector for LIBs. An integrated porous electrode based on CuO nanoflowers/copper fiber felt is developed for the anode. Results suggest that the reversible capacity and cycle stability of this new anode are significantly improved, compared with the pristine bare-surface copper plate under the same condition of rate cycles. The new anode structure based on the copper-fiber felt with a porosity of 60% exhibits a higher performance with an initial specific capacity of 609.5 mAh g−1 and retains 486.1 mAh g−1 after 200 cycles at a current density of 0.5 C. The improved electrochemical performance of this electrode is attributed to its large surface area of CuO nanoflowers and porous structure of the copper fiber felt, due to enhanced contact between the active material of CuO nanoflowers and electrolyte. This pore-rich structure makes the electrolyte easy to permeate into the electrode, shortens the diffusion path of Li+, reduces the internal resistance and alleviates the volume expansion of the active material during the insertion and desertion processes of Li+.

The Fe15−xMn40Al45+x (x = 0, 1, 2 and 3) and Fe15Mn40−yAl45+y (y = 1, 2 and 3) alloys were prepared by arc melting and annealed at 1000 °C for 7 days. The microstructure and magnetic properties are characterized by XRD and VSM. Corresponding corrosion potential and hardness are measured by electrochemical workstation and Vickers hardness tester. All samples have CsCl type Cubic structure. And for Fe15Mn40−yAl45+y alloys, with increasing Mn content, the lattice parameters increase from 2.9613 A to 2.9678 A, while the curie temperatures can be tuned from 288 K to 330 K. As for Fe15−xMn40Al45+x alloys, the curie temperatures rise from 315 K to 340 K with lattice parameters increasing from 2.9658 A to 2.9689 A. The peak values of magnetic entropy change under 5 T are −2.4 and −3.1 J·kg−1K−1 for Fe15Mn40Al45 and Fe14Mn40Al44 respectively. The values of refrigerant capacity power are 223.4 and 232.5 J·kg−1 under 5 T. The Arrott plots are also employed to investigate the magnetic phase transition, showing all samples undergo second order ferro-paramagnetic phase transition. Furthermore, these alloys have good hardness and corrosion resistance properties. The potential applications of these alloys as magnetic refrigerant will be also discussed in this paper.

The surface microstructure of the current collectors significantly affects the electrochemical performance of lithium-ion batteries (LIBs). This study shows that an effective method of orthogonal p...

A conductive layer, made of multi-walled carbon nanotubes (MWCNTs), with micro-cracks and a micro/nano porous structure was fabricated between the active material layer (AML) and the current collector in this study. The coating thickness of MWCNTs-based conductive layer (MCL) varies in the range of 25-100 μm. The electrochemical tests of half-cells demonstrate that both the mesocarbon-microbeads (MCMB) anode and the LiCoO2 cathode with a micro-cracked MCL show higher capacity, lower impedance and less capacity fading. These improvements are closely due to the enhancement of adhesion strength, and also the outstanding buffer effect of the micro-cracked MCL. With the change of the coating thickness, the size and amount of the micro-cracks on the MCL varies accordingly to accommodate the active material with different particle sizes. The electrodes including a micro-cracked MCL with a coating thickness of 50 and 75 μm are more suitable for MCMB and LiCoO2 with a particle size of 10-20 μm.

The energy density and operational life of lithium-ion batteries (LIBs) depend sensitively on the properties of electrode materials. Transition metal oxide based electrodes attract much attention because of their potential to offer high energy density. In this study, we report a binder-free composite anode composed of CuO nanosheets and multi-wall carbon nanotubes for LIBs. This composite anode is fabricated by a cost-effective electrophoretic deposition process followed by facile solution immersion. When tested in a LIB, this composite anode delivers a high reversible capacity of 540 mAh g−1 and maintains its capacity retention of above 78% after 50 cycles at a current density of 100 mA g−1, which is much higher than the CuO anode without carbon nanotubes. The high capacity, enhanced rate capability, low resistance, and increased operational life are attributed to the unique architecture of the hybrid electrode. The carbon nanotubes facilitate the electron transfer, enhance the structural stability of CuO nanosheets, and improve the adhesion of the CuO nanosheets to current collector. Such highly porous cross-linked network based on CuO nanosheets and multi-wall carbon nanotubes has great potential as a binder-free anode for high-performance LIBs.

The relation between the microstructure and the magnetic properties of Fe2P-type (Mn,Fe)2(P,Si,B) based materials has been systematically investigated by changing the annealing temperature and time. X-ray diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy measurements show that the alloys contain the main Fe2P-type phase and two impurity phases of (Fe,Mn)5Si3-type and Fe2MnSi-type. Boron appears to facilitate the formation of the Fe2P-type phase during the arc-melting progress. Upon increasing the annealing temperatures from 1123 to 1423 K, the Curie temperature (TC) decreases from 302.0 to 270.5 K in the Mn1.15Fe0.85P0.55Si0.45 alloys and the magnetic-entropy change (ΔSM) increases linearly with annealing temperature. For the Mn1.15Fe0.85P0.52Si0.45B0.03 alloys annealed at 1423 K for different times, TC decreases from 263.8 and 232.8 K with increasing annealing time and ΔSM reaches a maximum value after annealing for 48 h. The differences in the annealing temperature and time influence the Si content in the Fe2P-type phase of the alloys and determine TC, the thermal hysteresis and the magneto-elastic transition.

Fe-based metallic glass has been reported to exhibit high degradation ability for azo dye due to its unique atomic structure. In this work, we show that the degradation efficiency of Fe-based alloy can be further improved via simple heat treatment. Fe82Si2.5B12P2.5C amorphous ribbons were prepared by arc melting and melt spinning and then annealed from 100 °C to 850 °C for 5 min. A crystallization process from single α-Fe at 500 °C, to α-Fe + Fe3B at 520 °C, to α-Fe + Fe3B + Fe2C at 850 °C, took place. The degradation efficiency of the heat-treated ribbons decreased monolithically when annealed at 100-600 °C, but increased dramatically at 850 °C. The underlying degradation mechanisms were analyzed, that the formation and interaction of nanocrystals after annealing were considered mainly responsible for the differences in their degradation performances.

The effects of Co on microstructure, crystallization behavior and magnetic properties of (Ni0.5Fe0.5-xCox)80B10Si2Cu1Zr7 (x = 0~0.5) alloys were investigated. The results show that, the as-spun alloys remain lower coercivity (Hc) values (5 A/m ~ 14 A/m) over the whole Co content range, owing to their amorphous structure. After being annealed for 20 min above the onset temperatures of primary crystallization (Tx1), amorphous and nanocrystallines are coexisted in the alloys, and the crystal structure of nanocrystallines changes between fcc-(Ni, Fe, Co) and bcc-(Fe, Ni, Co) with the increasing Co content. In particular, it was found that Hc of the annealed alloys changes anomalously between 40 A/m and 1529 A/m with the increasing Co content, owing to the integrated action of grain size (D), magnetocrystalline anisotropy (K1) and lattice distortion. Especially for the alloys with x = 0.2 and x = 0.3, serious lattice distortion is the dominant factor for their higher Hc value than 1000 A/m.

This study presents a hierarchical MCMB/CuO/Cu anode structure with super-hydrophilic CuO substrate and blind-hole structures (BHSs) for lithium-ion battery (LIB) application. The porous hierarchical CuO clusters with controllable morphology and super hydrophilicity are prepared and combined with the BHSs on the surface of copper plates (CPs). Results indicate that the new anode yields a considerable improvement in reversible capacity and robustness under the condition of rate cycles. Compared with the conventional pattern of MCMB/Cu, the MCMB/CuO/Cu anode with BHSs produces reversible initial discharge and charge capacities of 381.5 and 347 mAh g−1 at a constant current of 0.5 mA. After 30 cycle times, the battery retains 276.7 and 276.6 mAh g−1, which amounts to 5 times as much as that of 0.5 C rate cycles. The energy density of the battery can be also greatly promoted. The larger surface area and porosity of the new anode facilitate formation of contact interface between the active material and current collector (CC). It also helps shorten the diffusion path of Li-ions and alleviate the volume expansion during the insertion and desertion processes of Li-ions.

Developing high-performance electrode structures is of great importance for advanced lithium-ion batteries. This study reports an efficient method to fabricate hierarchical shell/core CuO nanowire/carbon fiber composites via electroless plating and thermal oxidation processes. With this method, a binder-free CuO nanowire/carbon fiber shell/core hierarchical network composite anode for lithium-ion batteries is successfully fabricated. The morphology and chemical composition of the anode are characterized, and the electrochemical performance of the anode is investigated by standard electrochemical tests. Owing to the superior properties of carbon fibers and the morphological advantages of CuO nanowires, this composite anode still retains an excellent reversible capacity of 598.2 mAh g −1 with a capacity retention rate above 86%, even after 50 cycles, which is much higher than the CuO anode without carbon fibers. Compared to the typical CuO/C electrode systems, the novel binder-free anode yields a performance close to that of the typical core/shell electrode systems and a much higher reversible capacity and capacity retention than the similar shell/core patterns as well as the anodes with binders. It is believed that this novel anode will pave the way to the development of binder-free anodes in response to the increasing demands for high-power energy storage.

Fracture fields in coal rocks are the main channels for gas seepage, migration, and extraction. The development, evolution, and spatial distribution of fractures in coal rocks directly affect the permeability of the coal rock as well as gas migration and flow. In this work, the Ji-15-14120 mining face at the No. 8 Coal Mine of Pingdingshan Tian’an Coal Mining Co. Ltd., Pingdingshan, China, was selected as the test site to develop a full-parameter fracture observation instrument and a dynamic fracture observation technique. The acquired video information of fractures in the walls of the boreholes was vectorized and converted to planarly expanded images on a computer-aided design platform. Based on the relative spatial distances between the openings of the boreholes, simultaneous planar images of isolated fractures in the walls of the boreholes along the mining direction were obtained from the boreholes located at various distances from the mining face. Using this information, a 3-D fracture network under mining conditions was established. The gas migration pattern was calculated using a COMSOL computation platform. The results showed that between 10 hours and 1 day the fracture network controlled the gas-flow, rather than the coal seam itself. After one day, the migration of gas was completely controlled by the fractures. The presence of fractures in the overlying rock enables the gas in coal seam to migrate more easily to the surrounding rocks or extraction tunnels situated relatively far away from the coal rock. These conclusions provide an important theoretical basis for gas extraction.

Amorphous (FexNiyCoz)80B10Si2Cu1Zr7 (x + y + z = 1) alloys were prepared by melt spinning. By investigating the glass-forming ability, thermal behavior, crystallization and magnetic properties of alloy ribbons, detailed and integral pseudoternary diagrams of (FexNiyCoz)80B10Si2Cu1Zr7 alloys were constructed, which can make one clearly understand the effects of ferromagnetic elements (Fe, Co, Ni) on microstructure and physical properties. Results show that, all as-spun alloys show a fully amorphous structure and the coercivity (Hc) can be tuned to a lower value than 45 A/m. After being annealed, alloys with Ni content lower than 64 at.% (y

As environmentally friendly and high-energy density rechargeable energy storage devices, lithium-ion batteries (LIBs) have thriving prospects in the field of energy. The current collector, which serves as an important component of LIBs, significantly influences the electrochemical performance of the battery. Numerous efforts have been spent on the design and fabrication of high-performance negative current collectors in the field of LIBs to achieve excellent battery performances. These high-performance current collectors are mostly structuralized to achieve special functions. Hence, different types of structuralized current collectors used for LIB anodes are comprehensively discussed and summarized in this paper. The structuralized current collectors used in LIB anodes are classified into planar-plate-based special-surface current collectors and the 3D framework-based porous current collectors. Both types of the structuralized current collectors are further divided into the single-component and multicomponent current collectors. More subsections are provided and focus on providing description of the developing strategies, fabrication methods, electrochemical behaviors, in-depth reasons for high performances, and advantages and challenges for real applications of the structuralized current collectors in detail. Subsequently, the challenges and future research directions of structuralized anode current collectors are reasonably clarified. Based on an objective summary of the high-performance negative current collectors, this review provides an enlightening guide for the future development of current collectors and LIBs. The fundamental conclusions can also be extended to other energy storage devices.

Fe78Si11B9P2 metallic glass (MG) ribbons are proved to exhibit excellent comprehensive ability in azo dye treatment. The Fe78Si11B9P2 MG ribbons can degrade the azo dye effectively, which derived from high mass and electron transfer ability due to the cotton-like structure formed during the reaction. The degradation efficiency and reaction rate raise with the decrease of the initial Orange Ⅱ concentration, the increase of ribbon dosage and the proper addition of H2O2. The Fe78Si11B9P2 MG ribbons are more applicable in acidic and neutral solutions. Compared to the other reported Fe-based metallic glasses for dye degradation, the Fe78Si11B9P2 MG has a lower reaction activation energy and relatively good reusability in treating with azo dye. In addition, the achieved high COD removal indicates that the complex organic structures in azo dye can be decomposed completely by Fe78Si11B9P2 MG ribbons. This work not only provides a new effective and low-cost materials for wastewater treatment, but also promotes the practical applications of Fe-based MGs as functional materials.

The Fe0.6Mn0.4NiSi1−xAlx (x = 0, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, and 0.12) alloys were prepared by arc melting and annealed at 1073 K for 90 h. With increasing Al contents, the structure of Fe0.6Mn0.4NiSi1−xAlx changes from TiNiSi-type to Ni2In-type at room temperature, while the Curie temperature decreases from 390 K to 136 K. Although the refrigerant capacity is relatively small, about 126 J/kg, the maximum isothermal entropy change reaches a value of −ΔSmax = 52.9 J/(kg K) under 5 T for x = 0.04. At the same time, the alloys have great corrosion resistance. From x = 0 to 0.12, samples can be tuned from a second-order to a first-order and then to a second-order phase transition. It is worth noting that there is no magnetic hysteresis for all samples although they experience structural phase transition. The structural and magnetic phase diagrams of the Fe0.6Mn0.4NiSi1−xAlx system have been figured out. The results indicate that the relatively large magnetocaloric effects with no magnetic hysteresis and good corrosion resistance make these alloys a good candidate for magnetic refrigeration near room temperature.

FexOy-type iron oxides, especially α-Fe2O3 and Fe3O4, are powerful alternatives to the currently available graphitic anode materials for lithium-ion batteries (LIBs) owing to their high theoretical capacity, natural abundance, environmental benignity, non-flammability, and enhanced safety. In this context, compositional engineering is a widely used strategy to improve the electrochemical performance of electrode materials; in this method, the synergetic effects of individual components in a hybrid material are harnessed for improved performance. To improve FexOy-based materials in terms of compositional engineering, in this review, the factors affecting the electrochemical performance of pure FexOy and different kinds of additives combined with FexOy for LIB anodes via doping or compositing and their effects on the electrochemical performance of the anodes are discussed in detail. Several approaches that can enhance the performance of FexOy-based LIB anodes via compositional engineering are highlighted and the importance of a proper combination of compositional and structural engineering for achieving the desired physical/electrochemical properties in FexOy-type anodes is described. In the near future, such approaches may provide effective and efficient ways to obtain advanced rechargeable LIBs with a high energy/power density, long cycle life, and low cost.

The high-energy and low-cost lithium-sulfur (Li-S) battery is regarded as a new generation energy-storage device. However, the Li-S battery mostly suffers from low electronic conductivity and poor cycle capability. This study reports on a novel sandwich-structured cathode with optimized electrode architecture and interface design of the current collector (named as M-S-LTO) made by a facile layer-by-layer slurry coating process. The new integrated electrode is composed of a micro-cracked current collector (MCC) based on multi-wall carbon nanotubes, a middle layer of sulfur/carbon material and an upper current collector&interlayer (UCC&I) based on multi-wall carbon nanotubes and Li4Ti5O12 nanospheres. The M-S-LTO cathode produces a better electrochemical performance because of its improved internal electrical and ionic conductivity, stable structure and mitigation of shuttle effect, in contrast to the sulfur electrode with either an MCC (M-S cathode) or a smooth aluminum foil current collector (S cathode). At a current density of 0.2 C, the Li-S battery with the M-S-LTO cathode delivers a high initial capacity of 1248.6 mAh g−1 and retains a reversible capacity of 960.3 mAh g−1 after 200 cycles. Even at 1 C, its capacity can reach 773.4 mAh g−1 after 200 cycles. The battery with the M-S-LTO cathode shows a higher cycle performance than most of other reported cells based on the interlayer design with a comparable sulfur loading. With the enhanced electrochemical performance, the new cathode offers a promising avenue to fabricate high-performance Li-S batteries.

The Fe78Si13B9 amorphous alloy ribbons and high-entropy amorphous alloy ribbons of (FeCoNi)78Si13B9 were prepared by melt spinning method. The decolorization performances of these ribbons were investigated in details. It was interesting that Orange Ⅱ solution of 40 mg/L can be degraded almost completely within 70 min and a reduction 52.4% in COD (Chemical Oxygen Demand) value using Fe78Si13B9 amorphous ribbons, indicating the prominent capacity of alloys on the degradation of azo dyes. As for amorphous ribbons (FeCoNi)78Si13B9, they just presented a physical adsorption process, with no chemical degradation of dye molecules under the same conditions. Furthermore, the Fe78Si13B9 amorphous ribbons possess a higher decolorization reaction rate (kobs = 0.071 min−1) compared to the (FeCoNi)78Si13B9 ribbons, together with converting dye molecules to harmless micromolecule inorganic substances, which is of practical significance from the perspective of environmental protection. In addition, all the degradation process in this work fit well with the pseudo-first-order kinetic model. The findings are attractive, valuable and promising for the practical applications and they have important implications in developing Fe-based high-entropy alloys for functional application materials in the field of wastewater treatment.

Mining mechanics usually refers to the movement of overburden rocks and stress redistribution induced by mining effects, especially during the evolution of abutment pressure at a mining face (Xie et al. 2011). The characteristic of the stress field at a mining face serves as an important foundation for achieving roof safety and preventing excess gas (Suchowerska et al. 2013; Yang et al. 2011a). The mining effect may cause coal rocks to fracture, causing coal methane to escape from the fractured rock into the mining face, resulting in the exceedance of safety limits for gas. This is especially relevant under intensive mining conditions (Yang et al. 2011b; Li et al. 2006; Wang et al. 2012). Therefore, the study of mining mechanics is of great importance in achieving the safe and efficient coal mining. Many specific studies have been conducted to investigate stress redistribution, strata deformation, strata failure and fluid flow of coal seams (Islam and Shinjo 2009; Yang et al. 2014). However, these studies only focused on mining mechanics induced by mining advances, and neglected local mining effects, such as coal caving processes used for top coal caving method. In this manuscript, a field test and analytical analysis were conducted. A combination of global and local mining mechanics was consequently proposed for the top coal caving. Based on the real-time pressure monitoring of single props and hydraulic supports at a top coal mining face, intensive factors of pressure were adopted to provide a quantitative description of the mining mechanics.

Rectangular caverns are increasingly used in underground engineering projects, the failure mechanism of rectangular cavern wall rock is significantly different as a result of the cross-sectional shape and variations in wall stress distributions. However, the conventional computational method always results in a long-winded computational process and multiple displacement solutions of internal rectangular wall rock. This paper uses a Laurent series complex method to obtain a mapping function expression based on complex variable function theory and conformal transformation. This method is combined with the Schwarz-Christoffel method to calculate the mapping function coefficient and to determine the rectangular cavern wall rock deformation. With regard to the inverse mapping concept, the mapping relation between the polar coordinate system within plane ς and a corresponding unique plane coordinate point inside the cavern wall rock is discussed. The disadvantage of multiple solutions when mapping from the plane to the polar coordinate system is addressed. This theoretical formula is used to calculate wall rock boundary deformation and displacement field nephograms inside the wall rock for a given cavern height and width. A comparison with ANSYS numerical software results suggests that the theoretical solution and numerical solution exhibit identical trends, thereby demonstrating the method's validity. This method greatly improves the computing accuracy and reduces the difficulty in solving for cavern boundary and internal wall rock displacements. The proposed method provides a theoretical guide for controlling cavern wall rock deformation failure.