查看更多>>摘要：SnO2 with a high theoretical capacity has been regarded as a promising candidate for new-generation lithium-ion battery anodes, but challenging as well for the big volumetric variation and poor intrinsic conductivity. To address this challenge, herein, the SnO2 particles containing a small amount of Sn are reduced to the nanoscale and confined in a dual-porous carbon matrix by a relatively facile strategy, and hence exhibits significantly improved electrochemical performance. It is demonstrated that the synergistic effects of SnO2/Sn nanoparticles and dual-porous carbon matrix contribute to fast electrochemical kinetics and enhanced structural stability of the as-prepared SnO2-based composite (SnO2/Sn@p-C). In particular, the dual-porous carbon matrix with two sizes of pores can not only efficiently accommodate the volumetric variation and prevent the aggregation and pulverization of the SnO2/Sn nanoparticles with its big pore confining function, but also promote the ion diffusion and electron transfer by its small pores constructed network conducting open tunnel-like structure. Consequently, the SnO2/Sn@p-C exhibits outstanding lithium storage properties, revealing high capacity of 917.7 mA h g?1 at 200 mA g?1 after 450 cycles as well as 628.9 mA h g?1 at 1000 mA g?1 after 1000 cycles. Thus high-performance makes SnO2/Sn@p-C a promising advanced lithium-ion battery anode.
查看更多>>摘要：Although layered double hydroxides (LDHs), especially NiCo-based LDHs, have been verified to be a type of potential cathode material for supercapacitors with high specific capacity and electric conductivity, their lifespan and rate performance are still not satisfactory. Herein, a series of 3D NiCoFe-LDH samples with different molar ratio of Ni/Co/Fe are successfully fabricated on carbon cloth via an electrodeposition method. It is found that NiCoFe-LDH nanosheet assembled nanospheres/nanoflowers electrode delivers high specific capacity, electrical conductivity, and more importantly, more superior rate performance as well as cycle stability than pristine NiCo-LDH electrode without Fe introduction. Moreover, the as-assembled hybrid supercapacitor device with NiCoFe-LDH and activated carbon as the cathode and anode respectively displays a wide voltage window (0–1.5 V), large specific energy (65 W h kg?1 at the specific power of 83 W kg?1) together with an ultrahigh cycle stability (26% capacity increment after 5000 cycles). With the merits of ease to fabricate and outstanding energy storage property, the newly assembled hybrid supercapacitor delivers great potential for practical application in the near future.
查看更多>>摘要：For constructing high-performance hybrid supercapacitor devices, it is vital to exploit a battery-type cathode with enhanced kinetics and improved cyclic performance to match with a capacitive anode. Herein, highly porous FeCoSe2@NiCo-LDH core-shell nanosheet arrays were in situ decorated on face of carbon cloth via an electrodeposition approach and a selenylation treatment. The hierarchical heterostructure consisting of two types of vertically aligned interconnected two-dimensional nanosheets not only offers huge surface area and available diffusion pathways for quick electron/ion transport, but also generates plentiful heterointerfaces with modified electronic structure and enables synergetic effect between dual components. Consequently, the well-designed FeCoSe2@NiCo-LDH electrode displays a greatly boosted specific capacity of 220.9 mA h g?1 at 1 A g?1, 83.5% capacity retention at 20 A g?1, and wonderful cyclic stability, which are superior to those of single component. Furthermore, the hybrid supercapacitor device with a FeCoSe2@NiCo-LDH electrode and a hierarchical porous carbon electrode illustrates an extensive energy density of 65.9 Wh kg?1 at 1.248 kW kg?1 combined with long lifetime with 87.6% capacity retention over 10,000 cycles. These superb properties manifest that the integrated FeCoSe2@NiCo-LDH electrode owns a desirable application prospect in hybrid energy storage systems.
查看更多>>摘要：The strategy of combining well-designed hollow structure with compositional engineering has been aroused wide interest in the fields of energy storage. Herein, starting from Ni-Co coordination polymer spheres as self-templates, the NiCo2S4/CoO multi-shelled hollow spheres (NiCo2S4/CoO HMSs) are constructed through calcination and sulfurization, in which the shells consist of a large number of nanoparticles with heterostructures. By virtue of its structural and compositional advantages, the NiCo2S4/CoO HMSs present desirable energy storage properties including high specific capacity (860.1 C g?1 at 1 A g?1), outstanding rate performance and good cycling durability. It is also found that the NiCo2S4/CoO HMSs possess accelerated reaction kinetics. Furthermore, a hybrid supercapacitor device, assembled by NiCo2S4/CoO as the positive electrode and hierarchically porous carbon as the negative electrode, yields a high energy density of 55.35 Wh kg?1 at 790 W kg?1. This work would contribute to designing advanced heterostructures for high-performance electrode materials.
查看更多>>摘要：The recently-developed Al-Mn-Sc based alloys specific for laser powder bed fusion (LPBF) have shown excellent mechanical performance. However, the complicated intermetallic particles in the microstructure remain to be identified, hindering the deep understanding of their effects on mechanical properties and further property improvement. In this work, a range of phases in a LPBF-built Al-Mn-Sc based alloy have been systematically studied by atom probe tomography. The results clarify characteristic intermetallic phases in two different grain-size regions in the microstructure. In the fine grain (FG) region, three distinct phases have been identified. A Sc-rich phase having an average composition of Al3.3(Sc0.8Zr0.2) is observed at both the grain boundary (GB) and grain interior, but they have different morphologies. The Mn-rich phase with an average composition of Al4.3(Mn0.9Fe0.1) is only observed along GBs. In addition, Mg-rich oxide has been observed either with a separate distribution or attached to Sc-rich particles. In the coarse grain (CG) region, the GB particles exhibit different size and composition from FG region. The Sc-rich GB particles contain Mg enrichment rather than Zr and the composition is determined to be Al3.4(Sc0.75Mg0.25). The Mn-rich GB particles in the CG region, with higher Fe contents, are Al4.3(Mn0.8Fe0.2) along the GBs and Al4.5(Mn0.85Fe0.15) inside the grains. Many smaller Mg-rich oxides and Sc-rich particles are also observed in the internal grains of the CG region.
查看更多>>摘要：Sodium-ion batteries have high potential for next-generation battery system because of their cost-effective and similar energy-storage mechanism to lithium-ion batteries. However, the commercial graphite anode for lithium-ion batteries cannot be applied to sodium-ion batteries. The lower rate performance and poor cycling life of existing anode materials are major bottlenecks to prospective application in sodium-ion batteries. To address this issues, we synthesize a novel ultrathin Bi2Se3 layered nanosheets that enhance sodium-ion storage performance due to its stable graphene-like structure. Benefiting from the layered nanosheets morphology, as-prepared anode material exhibit excellent electrochemical performance, which can deliver an initial high capacity of 650 mA h g?1 (Na+ storage) at 0.1 A/g along with outstanding stability. The ultrathin Bi2Se3 layered nanosheets with a thickness of ~6 nm offer a large electrode-electrolyte contact interface due to its porous morphology. Ex-situ transmission electron microscopy analysis and electrochemical impedance spectroscopy measurement reveals the structural stability of bismuth selenide nanosheets during repeated sodium-ion insertion and extraction process. The superior electrochemical performance and unique graphene-like architecture of the layered bismuth selenide nanosheets offer a promising anode for commercial sodium-ion batteries.
查看更多>>摘要：The combination of soft matrix alloys and brittle spheres has gained unceasing demand due to its structural strength and tailored properties to meet industrial and commercial needs. Single sphere aluminum matrix syntactic foams (AMSFs) show poor ductility and fracture strength at high volume fractions of reinforcement. In the present investigation, three different volume fractions of the single sphere (alumina hollow spheres and cenospheres), syntactic foams (SF) and hybrid SF were prepared using a powder metallurgy route with a maximum reinforcement fraction of 30%. The lowest density of 2.17 g cm -3 was produced with no chemical reaction observed between matrix and reinforcement. The quasi-static compression studies have shown a significant effect of particle size and volume fraction with respective mechanical properties (peak stress = 601 MPa (Sample #1), 610 MPa (Sample #4) and 525 MPa (Sample #10)). The densification strain, energy absorption, energy absorption efficiency (EAE) and ideal EAE have been predicated for all the samples. The macroscopic deformation of SFs is in good agreement with stress-strain data. The results show that the slope of the plateau region follows a negative linear trend against the strain hardening exponent.
查看更多>>摘要：For the first time, we discovered the exceptional oxidation phenomenon on Ti6Al4V alloy. A thin layer of silver was pre-deposited via PVD on a Ti6Al4V alloy surface before ceramic conversion treatment (CCT) based on thermal oxidation in air at 620 °C. The pre-deposited silver particles accelerated the oxidation of the Ti6Al4V alloy by up to 50 times, and also helped to produce a thick compact surface oxide layer with a larger surface area compared to a non-silver pre-treated surface. However, silver had a less profound effect on the oxidation of other titanium alloys that didn't contain vanadium, additionally the silver particles tended to agglomerate on their surfaces, particularly for commercially pure titanium (CPTi). Systematic work examining the impact of vanadium found that vanadium together with silver played a critical role in activating oxygen and promoting its diffusion in the oxide layer, thus dramatically accelerating the oxidation of the vanadium-containing titanium alloys with a pre-deposited Ag layer in CCT. SEM/EDX, TEM, XRD and XPS analyses on the surface phase constituents and microstructure helped to explicate the rapid oxidation mechanism of pre-deposited silver on Ti6Al4V surfaces, and thus provide a new insight into modifying the titanium alloys surface efficiently.
查看更多>>摘要：Two dimensional (2D) Ruddlesden Popper perovskites have been extensively studied for their exceptional optical and electronic characteristics while only a few studies have shed light on their mechanical properties. The existing literature mainly discusses the mechanical strength of single crystal perovskites, however a study of structure tunability of 2D perovskite thin films is still missing. In this study, we report the effect of number of inorganic layers ‘n’ on elastic modulus of 2D, quasi-2D perovskites and 3D perovskite thin films using nanoindentation technique. Our studies indicate the role of orientation of the inorganic layers in perovskite films in tailoring their mechanical response. The experimental results have been substantiated using first principle density functional theory (DFT) calculations. We also report other important mechanical parameters namely, shear modulus, bulk modulus, Poisson's ratio, Pugh's ratio, Vickers hardness, yield strength and the universal elastic anisotropic index using DFT simulations. Anisotropy is observed in the elastic modulus of the materials under study and has been discussed in detail in the manuscript. Understanding the mechanical behavior of 2D Ruddlesden Popper perovskites thin film in comparison with conventional 3D perovskite offers intriguing insights into the atomic layer dependent properties and paves the path for next generation mechanically durable and novel devices.
查看更多>>摘要：Despite numerous achievements recorded so far in developing solar absorber coatings for photothermal applications, the study of the thermal stability in humid and cold environment remains very scarce and the underlaying physics behind the transfer of the absorbed energy to the working fluid has never been investigated. In this perspective, we developed Ti/AlN/Ti/SiO2 film as multilayer selective solar absorber coating (MSSAC) on Fe3O4 modified stainless steel substrate using Direct Current (DC)/Radio Frequency (RF) magnetron sputtering at room temperature. The coating exhibited solar absorptance of 0.969 and thermal emittance of 0.220 in the solar and infrared spectrum regions respectively. The MSSAC was found to be thermally stable up to 500 °C in air. Further increase in annealing temperature to 600 °C resulted to a slight decrease in solar absorptance from 0.969 to 0.953 and a small rise in the emittance value from 0.220 to 0.258. A high humidity test and rapid heating-cooling cycling (RHCC) test revealed the stability of this coating and its potential application in humid (90 mmHg) and cold (? 50 °C) environments. Additionally, the coating shows good adhesion strength even after humidity and RHCC tests. The in-plane heat distribution analysis using thermal infrared imaging camera illustrated that there is a good possible transfer of the absorbed heat to the working fluid due to high surface temperature exhibited by Ti/AlN/Ti/SiO2 coated modified stainless steel (SS) substrate than the other boundary conditions. Overall, these results indicate that the present coating has the potential application in both high temperature, humid and cold environments.
NSTL
Elsevier