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Enhanced refrigeration capacity in Ho1-xDyxB2 compounds around liquid hydrogen temperature
No full textIn this study, the crystal structure, magnetic properties, and magnetocaloric effect of Ho1-xDyxB2 compounds were investigated. It was found that nearly single-phase (Ho,Dy)B-2 compounds with the AlB2-type structure directly form in the as-arc melted alloys and have two successive magnetic transitions. With the increase of Dy concentration x from 0 to 0.8, the spin reorientation transition temperature remains at about 13 K, while the Curie temperature significantly increases from 16 to 43 K. As a result, the full-width at half-maximum of the magnetic entropy change versus temperature curve increases from 19.9 to 48.2 K. Also, these Ho1-xDyxB2 compounds exhibit a large refrigeration capacity of 523-635 J kg(-1) under a magnetic field change of 5 T, although the maximum magnetic entropy change decreases from 34.3 to 17.2 J kg(-1) K-1. In addition, Dy-containing compounds exhibit a table-like magnetocaloric effect compared with the HoB2 compound. Our results indicate that Ho(1-x)Dy(x)B(2 )compounds are a promising candidate for cryogenic magnetic refrigeration around liquid hydrogen temperature. (C) 2021 Elsevier B.V. All rights reserved
Carbon fiber reinforced thermoplastic composites and TC4 alloy laser assisted joining with the metal surface laser plastic-covered method
No full textThe carbon fiber reinforced thermoplastic composites (CFRTP) and the TC4 alloy are the main materials for aircrafts lightweight manufacturing. The joining quality between them determines the fatigue life of CFRTP-TC4 hybrid structures. To improve the joining quality between the CFRTP and the TC4 alloy, a metal surface laser plastic-covered method was proposed, and a high-speed laser rotational welding technology was applied. The joint strength, the fatigue resistance and the failure mechanism of the joint were investigated. The result showed that the shear strength and the fatigue resistance of the CFRTP-TC4 joint can be improved significantly and a laser harden layer was produced on the TC4 surface. The joint failure fracture was occurred at the interlayer of CFRTP, which indicates that the joint strength is higher than the interlayer bonding strength of CFRTP
Straw-like phosphorus-doped Co2MnO4 nanoneedle arrays supported on nickel foam for high-efficiency hydrogen evolution reaction in wide pH range of electrolytes
No full textDeveloping high-performance and cut-price non-noble-metal electrocatalysts for hydrogen evolution reaction (HER) is desirable yet challenging. Herein, straw-like phosphorus-doped Co2MnO4 nanoneedle arrays supported on nickel foam (P-Co2MnO4/NF) were prepared by successive hydrothermal treatment, oxidation and P doping for high-efficiency HER. Benefiting from the unique needle-like arrays and compositions advantages, P-Co2MnO4/NF exhibited excellent HER activities with the overpotentials of 33, 43 and 102 mV to afford a current density of 10 mA cm(-2) in alkaline, acidic and neutral media, respectively, coupled with the long-term electrochemical stability. This work affords an effective avenue for preparation of cost-effectiveness, high-efficiency and wide-pH HER catalysts for electrochemical energy technologies
Improving Wear and Corrosion Properties of Magnesium Alloy by Cold Sprayed Nano WC-17Co Coating
No full textTo promote the application of magnesium alloys for reducing the weight of the engineering components, improvement of their wear and corrosion resistance by coating processes is a necessity. In the present study, cold sprayed nano WC-17Co coatings have been deposited on commercial AZ80 magnesium alloy at different nozzle traverse speeds. WC-17Co coating exhibits a highly dense structure and well bonds with the magnesium alloy substrate when the traverse speed is selected as 80 and 40 mm/s. The C40 coating that is prepared at 40 mm/s possesses the highest microhardness and fracture toughness. The ball-on-disk wear test indicates that WC-17Co coating can significantly improve the wear resistance of magnesium alloy. The wear rate of C40 coating is 8.2 x 10(-7) mm(3) N-1 m(-1), while magnesium alloy exhibits very high wear rate of 6.8 x 10(-4) mm(3) N-1 m(-1). Meanwhile, WC-17Co coating reduces the corrosion current density of magnesium alloy and C40 coating also possesses more excellent corrosion resistance than that of C80 coating. Thus, with appropriate traverse speed, high quality nano WC-17Co coating can be prepared and the wear and corrosion resistance of magnesium alloy substrate can be greatly improved by this cold sprayed coating
Construction of compressible Polymer/MXene composite foams for high-performance absorption-dominated electromagnetic shielding with ultra-low reflectivity (vol 173, pg 932, 2021)
No full textA Miniaturized Active Thermography System to Inspect Composite Laminates
No full textWith the rapid increase of the integration and complexity of industrial components, the inaccessibility and inapplicability of existing nondestructive testing devices have become a bottleneck for in situ inspection of these objects. This article introduces a miniaturized active thermography system featured with a small-size, low-resolution, and low-cost thermal sensor, where two optional excitation sources including flash and laser are integrated. Dedicated data analysis approaches to evaluate defects are proposed considering the degraded signal quality. Three carbon fiber-reinforced polymer laminates with a variety of defects are evaluated quantitatively and qualitatively using the proposed system by comparing with two existing non-miniaturized inspection systems. The results show that the proposed system can work effectively for the degradation assessment of composite laminates. Even with the technical limitations that affect the detectability, for instance, the low pixel resolution, this technique will play an important role to inspect components featured with geometrically intricate space
Nanoporous Metals: From Plasmonic Properties to Applications in Enhanced Spectroscopy and Photocatalysis
No full textThe field of plasmonics is capable of enabling interesting applications in different wavelength ranges, spanning from the ultraviolet up to the infrared. The choice of plasmonic material and how the material is nanostructured has significant implications for ultimate performance of any plasmonic device. Artificially designed nanoporous metals (NPMs) have interesting material properties including large specific surface area, distinctive optical properties, high electrical conductivity, and reduced stiffness, implying their potentials for many applications. This paper reviews the wide range of available nanoporous metals (such as Au, Ag, Cu, Al, Mg, and Pt), mainly focusing on their properties as plasmonic materials. While extensive reports on the use and characterization of NPMs exist, a detailed discussion on their connection with surface plasmons and enhanced spectroscopies as well as photocatalysis is missing. Here, we report on different metals investigated, from the most used nanoporous gold to mixed metal compounds, and discuss each of these plasmonic materials' suitability for a range of structural design and applications. Finally, we discuss the potentials and limitations of the traditional and alternative plasmonic materials for applications in enhanced spectroscopy and photocatalysis
Ionic liquid-induced low temperature graphitization of cellulose-derived biochar for high performance sodium storage
No full textThe graphitization of biochar by high temperature carbonization above 2000 degrees C or metal-based catalytic approaches posed specific hindrances to the industrial production of high-quality graphitic carbon from biomass. The use of imidazolium-based ionic liquids (ILs) to induce fast graphitization of biochar at a low temperature range has not yet been reported. In this work, the carbonization of microcrystalline cellulose and 1-butyl-3-methylimidazolium acetate (BMIMAcO) at the temperature range of 750 degrees C-1400 degrees C led to enhanced graphitization of the biochar in comparison with the carbonization of microcrystalline cellulose alone. The incorporation of intact imidazolium rings into carbon skeleton played a critical role in the formation of graphitic structure with high nitrogen content. The IL-induced cellulose carbon obtained at 1000 degrees C (ICC-1000) with 5.67 at.% of nitrogen-doping presented interconnected graphitic nanosheets with 0.488 nm interlayer spacing and abundant mesopores and macropores on the surface. When used as anodes of sodium-ion batteries (SIBs), the ICC-1000 exhibited stable reversible capacity around 391 mAh g(-1) at 100 mA g(-1) for 100 cycles and 136 mAh g(-1) at 500 mA g(-1) for 1000 cycles, showing satisfactory sodium storage performance. Kinetic analysis of Na+ storage revealed that the ICC-1000 showed obvious capacitive characteristics and improved electric conductivity. DFT calculations suggested an interlayer spacing of 4.9 angstrom for optimal Na+ intercalation in multilayer graphene, and the capacity of pristine multilayer graphene was greatly improved from 69.8 to 527.3 mAh g(-1) after 4.8 at.% of N-doping
Solvent Annealing Enables 15.39% Efficiency All-Small-Molecule Solar Cells through Improved Molecule Interconnection and Reduced Non-Radiative Loss
No full textPost-treatment is of great importance to form nanoscale phase-separated morphology for all-small-molecule organic solar cells (ASM-OSCs), while the reasons for the difference between thermal annealing (TA) and solvent annealing (SVA) remain unclear. In this work, the influences of TA and SVA (with three common solvents of THF, CS2, and CF) are systematically investigated based on BT-2F:N3 through characterization of photovoltaic performance, molecular stacking, charge transfer, etc. The results indicate that: i) solvents with good solubility induce stronger molecular interaction than that of TA treatment, and thus endowing molecules with better mobility to migrate for crystallization and phase separation, which leads to better J-aggregation and molecular interconnection. ii) Donor-selectively dissolved CS2 is better for optimizing the donor domain for its suitable domain size, improved molecular interaction and interconnection, and reduced trap states. iii) CS2 imposes a small impact on N3 acceptors and thus alleviates the increment of non-radiative recombination. As a result, CS2 SVA with unique multifunctions enables a PCE of 15.39% with simultaneously improved voltage (0.845 V) and fill factor (75.02%), which is much higher than 14.66% of TA treatment. Moreover, 15.39% efficiency is also the highest value in binary ASM-OSCs
An in situ TEM nanoindentation-induced new nanostructure in cadmium zinc telluride
No full textPhase transformations occurring in a solid govern the structural and physical properties significantly. Nevertheless, deformation-induced phase transition in a soft-brittle solid has not been demonstrated yet. Soft-brittle cadmium zinc telluride (CZT) based instruments have produced technological breakthroughs in the semiconductor industry, and therefore their phase transformations have been widely investigated during the past 60 years. In this study, in situ transmission electron microscopy (TEM) nanoindentation was performed on CZT, and it was found that no brittle fracture occurred at a peak load of 41.9 mu N, corresponding to a stress of 1.75 GPa. A new nanostructure induced by in situ TEM nanoindentation was observed, consisting of a single crystal, slip bands, stacking faults, a superlattice, a new tetragonal phase, and Moire fringes. The new tetragonal phase was formed by partial Cd and Te atoms in the (11 (1) over bar) plane slipping along the [(1) over bar2 (1) over bar] orientation, which was elucidated by ab initio simulations. It belongs to a tetragonal crystal system, and the lattice distances along the X and Y axes were 0.382 and 0.376 nm, respectively. Our findings provide new insights into the deformation-induced phase transformation for a soft-brittle solid, and have application potential in solar cells, radiation detectors, and medical imaging, quantum, flexible electronic and optoelectronic devices