The electrochemical reversibility of maricite NaFePO4 is highly dependent on the rational design of the nanostructure. We propose, for the first time, an effective strategy of applying an acid-etched ...carbon cloth (eCC) as the substrate to be loaded with NaFePO4@C and significantly enhance the electrochemical activity of the maricite. The electrochemical test results show that the NaFePO4@C loaded on eCC exhibits a much higher reversible capacity (142 mAh g−1 at 0.1 C) than that (107 mAh g−1 at 0.1 C) of the material loaded on an Al current collector. Moreover, compared to that of the untreated carbon cloth (CC), NaFePO4@C loaded on eCC shows a superior rate performance and ultralong cycling lifetime at high mass loading levels. The excellent electrochemical performance of the NaFePO4@C-eCC electrode benefits from the regular grooves on the surface of the eCC, which provide a significantly larger surface area that is favorable to NaFePO4@C strongly and uniformly binding onto the carbon fibers. The self-supporting electrode configuration, that is, without the addition of an inactive binder and conductive additives, facilitates fast ion/electronic transport and reduces the aggregation of the NaFePO4@C particles. This work is expected to provide a new route for achieving high electrochemical activity in NaFePO4.
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Abstract
Although the closed pore structure plays a key role in contributing low-voltage plateau capacity of hard carbon anode for sodium-ion batteries, the formation mechanism of closed pores is ...still under debate. Here, we employ waste wood-derived hard carbon as a template to systematically establish the formation mechanisms of closed pores and their effect on sodium storage performance. We find that the high crystallinity cellulose in nature wood decomposes to long-range carbon layers as the wall of closed pore, and the amorphous component can hinder the graphitization of carbon layer and induce the crispation of long-range carbon layers. The optimized sample demonstrates a high reversible capacity of 430 mAh g
−1
at 20 mA g
−1
(plateau capacity of 293 mAh g
−1
for the second cycle), as well as good rate and stable cycling performances (85.4% after 400 cycles at 500 mA g
−1
). Deep insights into the closed pore formation will greatly forward the rational design of hard carbon anode with high capacity.
The development of cost effective, high performance, electrode materials for sodium ion batteries is of critical importance for large scale energy storage. Herein, we synthesize a novel nitrogen and ...fluorine co-doped porous carbon using a facile one-pot pyrolysis of three low cost components: polytetrafluoroethylene, a nitrogen-containing resin, and potassium hydroxide. The co-doped carbon comprises 3D assemblies of highly porous sheets with defects/disorders (and wide interlayer spacing of ~0.42 nm), which have a large surface area of 2040.3 m2 g−1 with hierarchical pore sizes. The advantageous combination of these structural features facilitates high sodium ion storage capacity, fast transfer kinetics and stable cycling. As a result, the co-doped carbon delivers an impressive 312.6 mAh g−1 at 0.1 A g−1 after 300 cycles and 215.3 mAh g−1 at 5 A g−1 after 5000 cycles (or 0.005% loss per cycle). Therefore, the excellent cycling performance of the carbon in combination with its convenient and low cost synthesis offers a promising sodium ion battery anode material for large scale energy storage.
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•A unique NF-3DC is achieved by one-pot pyrolysis of PTFE, N-containing resin and KOH.•NF-3DC contains abundant macro, meso and micropores, and enlarged interlayer gaps.•NF-3DC exhibits large reversible capacity and ultra-stable cycle performance in SIB.
Sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) are greatly potential candidates for large-scale renewable energy storage. However, developing highly efficient anode materials for the ...relatively larger radius of Na+ and K+ ions is still a hot issue. Herein, we report spherical nanoflowers of vanadium disulfide (VS2) with thin petals of 15 nm and high purity of crystallinity, synthesized by one-pot solvothermal method using propylene glycol as solvent without any growth-directing surfactants. Results demonstrate that this spherical nanoflower structure provides a stable framework for Na+/K+ insertion/extraction, wherein, SNF-VS2 not only shows a reversible charge capacity of 329 mAh/g at 0.2 A/g with an initial coulombic efficiency (ICE) of 88.52% for sodium ion storage, but also delivers a reversible charge capacity of 383 mAh/g at 25 mA/g, owning an ICE of 74.09% for potassium ion storage. The high capacity and outstanding ICE make the spherical VS2 nanoflowers ranking among the most effective transition metal dichalcogenide based anode materials and strongly indicate their promising usability for practical SIB and KIB applications. And the outperforming Na+/K+ storage performance is largely due to the abundant interface area with electrolyte and the short ion diffusion paths formed by their ordered flower-like structure.
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•Spherical nanoflower like VS2 was synthesized using a non-template strategy.•The VS2 exhibited high capacities, reversibility and excellent cyclability for Na+/K+ storage.•The unique nanoflower structure provides a more efficient Na+/K+ diffusion path than that of stacked structure.
•CADWE is proposed to merge CAD and CAE application into a unified pattern.•CADWE maintain top–down modeling process and change propagation in complex product design.•CADWE is based on three ...cornerstones, i.e., unified preliminary model, generalized feature and agent of preliminary geometry.•Preliminary model is a sort of unified and shareable integration information model.•Generalized feature and its modeling method serve for global CAD/CAE modeling strategy.•Agent of preliminary geometry can solve the problem involved in change propagation.
In order to considerably reduce the overall time and cost associated with design process, it has been widely noted that data consistence and a unified software platform play a vital role in CAD/E integrated design. A novel modeling mechanism named as CADWE (Computer-Aided Design-While-Engineering) is proposed to merge CAD and CAE application into a unified pattern. Meanwhile,the CADWE maintains top–down modeling process and change propagation in complex product design. Preliminary model is adopted to build up consistent and shareable integration information model instead of focusing on programming to link different model to keep the consistence. Particularly, generalized feature and agent of preliminary geometry are put to use to achieve synchronous and automatic change propagation from preliminary geometry to detailed model and FEM application. Thus, not only numerous duplication and human error in complex simplification operation and incompatible data exchange may be avoided, but also much software development is dispensable. A software package is developed and used in change propagation with the aid of NX/Open API. To explain the CADWE modeling process with more insight, two examples are used as the case studies. By means of the comparison with the techniques in the literatures high relevant to this topic, it proves that the CADWE technology is good at handling complicated product modeling and their change propagation with little software development.
We break the limit of grain refinement and strength of low-carbon steel by tuning deformation compatibility of heterostructure.
Ultrastrong materials can notably help with improving the energy ...efficiency of transportation vehicles by reducing their weight. Grain refinement by severe plastic deformation is, so far, the most effective approach to produce bulk strong nanostructured metals, but its scaling up for industrial production has been a challenge. Here, we report an ultrastrong (2.15 GPa) low-carbon nanosteel processed by heterostructure and interstitial mediated warm rolling. The nanosteel consists of thin (~17.8 nm) lamellae, which was enabled by two unreported mechanisms: (i) improving deformation compatibility of dual-phase heterostructure by adjusting warm rolling temperature and (ii) segregating carbon atoms to lamellar boundaries to stabilize the nanolamellae. Defying our intuition, warm rolling produced finer lamellae than cold rolling, which demonstrates the potential and importance of tuning deformation compatibility of interstitial containing heterostructure for nanocrystallization. This previously unreported approach is applicable to most low-carbon, low-alloy steels for producing ultrahigh strength materials in industrial scale.
The closed pore has been considered as the key structure for Na ion storage in hard carbon. However, the traditional view is that closed pores can only be formed by the curling of graphite‐like ...crystallites in the case of high temperature carbonization. Ingenious designing of closed pore structures at lower temperature is still blank. Herein, for the first time, engineering the wall thickness and number of closed pores in waste rosewood‐derived hard carbon was successfully achieved at a low temperature of 1100°C by removing the lignin and hemicellulose components in wood precursor. When applied as an anode material, the optimum sample exhibits a high capacity of 326 mAh/g at 20 mA/g and a remarkable rate capability of 230 mAh/g at 5000 mA/g, significantly higher than those of the untreated sample (only 33 mAh/g at 5000 mA/g). The significantly improved Na storage performance should be attributed to abundant closed pores that provide sufficient spaces for Na storage and thin pore wall structure that is beneficial to the diffusion of Na+ in the bulk phase. This work provides a new idea for the future application of biomass‐based hard carbon for advanced Na ion batteries.
Structure of waste wood‐derived hard carbon was regulated by a chemical treatment, which results in more available closed pores with thinner pore walls for Na storage. Significantly improved Na storage performance with high plateau capacity was achieved by regulating the closed pores in hard carbon even at 1100°C.
Purpose
Magnetic minerals within fluvial sediments are affected by a variety of natural and anthropogenic factors, limiting the capability of sediment magnetism in tracing provenance, assessing ...pollution, and other environmental or geological fields.
Methods
Twenty-three samples were collected from Liuxi River, a river influenced by complex natural and human processes, in southern China to conduct the analysis of magnetism, particle size, and geochemical elements. The micromorphology of magnetic particles was directly observed by scanning electron microscope and energy dispersive spectrometer.
Results
The following are the factors affecting the sediment magnetic properties: (1) There is a sampling site in the upper reach with over 100 times magnetic susceptibility than other sites. This sampling site is close to the areas having documented iron ore mining and smelting activities in the past few hundred years, and the sample contains the very high concentrations of metals (e.g., Fe, Mn, Ni, Pb, Sn, V, Cr, Cu, and Bi), implying the ancient mining activity could pose environmental risks in modern sediments. (2) In a downstream direction, magnetic concentration shows a decreasing tendency and magnetic grain size becomes finer. The contributions of superparamagnetic particles and high-coercivity minerals (e.g., hematite) to the total magnetism increase, and technogenic magnetic particles appear downstream of urban areas. In general, the upstream magnetic minerals are controlled by weakly weathered coarse-grained particles produced by granite denudation, while the downstream magnetic minerals are affected by the sedimentary rocks and the human activity. (3) Magnetic minerals become coarse after the river flows over barrages in response to the hydrodynamic changes.
Conclusions
The investigation reveals the natural and anthropogenic influences according to the analysis of the sediments in Liuxi River, and further research related to the sediment magnetism in complex river should be conducted.
A new processing route to produce Ultrafine-Grained Dual-Phase steel has been proposed, involving cold-rolling and subsequent intercritical annealing of a fibrous ferrite⁻martensite starting ...structure. Ultrafine-grained DP (UFG-DP) steel with an average ferrite grain size of about ~2.7 μm and an average martensite island size of ~2.9 μm was achieved. Tensile testing revealed superior mechanical properties (the ultimate tensile strength of 1267 MPa and uniform elongation of 8.2%) for the new DP steel in comparison with the fibrous DP steels. The superior mechanical properties are attributed to the influence of microstructure refinement on the work-hardening and fracture behavior.
We report a facile synthesis strategy that achieves two goals of carbon support design for oxygen reduction catalysis: (1) self-assembly of hierarchical porous structure, with (2) well-separated ...nitrogen and boron codoping. The B and N codoped carbon nanofibers (BNCNF) grow directly on a cobalt foil catalyst via a “dissolution–diffusion–precipitation” mechanism using tert-butylamine borane as the source of boron, nitrogen, and carbon. The process releases gaseous boron and nitrogen at different temperatures and times, which greatly inhibits the formation of disadvantageous B–N bonds in the support. BNCNF has hierarchical porosity, large surface area, good structural stability, abundant reaction active sites, and facilitates highly dispersed distribution of platinum nanoparticles. Owing to strong interactions and multiple synergistic effects, Pt/BNCNF has increased oxygen reduction activity and durability in HClO4 solution over that of commercial Pt/C. Pt/BNCNF facilitates a Pt mass activity of 355.4 mA mg–1 (approximate 3.5 times larger than Pt/C) at 0.9 V vs RHE. Furthermore, Pt/BNCNF has better stability and maintains 90.4% of its initial mass activity after 5000 potential cycling tests, which is remarkably higher than that of Pt/C at 50.6%.
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