查看更多>>摘要：Hydrogen (H)- and deuterium (D)-loaded Mg_(0.25)Mn_(0.75) nanocomposites were prepared by a ball-milling process and Atom Probe Tomography (APT) analyses were carried out in order to investigate the resultant nanostructure. Due to the immiscibility of the Mg-Mn system, non-uniform and interconnected Mg-rich domains with a thickness of several to 10 nm formed in both of the H- and D-loaded composites. Such complex morphology could be attributed to the severe cold-rolling effects induced by ball-milling. The inhomogeneous distribution of D observed by the APT analysis is likely the result of severe lattice distortion and multiple defects, which are cold-rolling effects. While the detection of D in the D-loaded composite was hampered significantly by the desorption of D during specimen preparation, D remained around the boundary of the Mg-rich domains/Mn-rich matrix. This suggests that the modulated intermixing of immiscible Mg and Mn atoms together with the ball-milling effect results in a disordered atomic arrangement around the boundary. This is assumed to be one of the contributing factors in the destabilization of Mg hydride observed in our previous works.
查看更多>>摘要：The development of ABO_3 perovskite-structured dielectric materials with high recoverable energy storage density (V_(rec)) and power density (P_D) is crucial for the downsizing of pulsed power devices. Despite several research efforts, achieving a high W_(rec) over a wide working temperature range in an environmentally benign system remains a difficulty. A synergistic design strategy is given here, which includes concurrently doping at the A- and B-site to achieve a spread and depressed dielectric response, adding sintering aids, and employing advanced viscous polymer rolling technology for dense and ultra-thin ceramic samples, respectively. Finally, at a relatively low electric field of 380 kV/cm, an ultrahigh W_(rec) of 6.57 J/cm~3 is realized in (Bi_(0.5)Na_(0.5))_(0.93)Ca_(0.07)Ti_(0.85)Zr_(0.15)O_3-0.5 wt% Li_2CO_3 component, which benefits from gentle polarization saturating and improved breakdown strength. The W_(rec) can be maintained above 6 J/cm~3 while maintaining strong thermal stability (variation ≤ ± 3%) over a temperature range of 30-150 °C. Because BNT-based materials have such high energy storage performance and temperature stability, they are not only a promising candidate for replacing lead-based dielectrics, but also a valuable guide for developing new high-performance ferroelectric materials for future energy storage devices in the pulsed power system.
查看更多>>摘要：Transition metal dopant engineering and rational architecture design have been proven to be effective strategies to improve the electrochemical energy storage properties of electrodes. Herein, V-doped NiMn-layered double hydroxide composites were supported on reduced graphene oxide-coated Ni foam (NMV-L/ rGO) by a hydrothermal method. The influences of V content on the electrochemical performances of NMV-L/rGO composites were investigated in detail. At an optimal content of V doping (15%), the NMV-L/rGO-15 reveals enhanced electrochemical properties, and it is subsequently applied as the substrate for the elec-trodeposition of Ni_3S_2 layer. Benefiting from the collaborative effect of NMV-L/rGO-15, Ni_3S_2, and rGO materials, as well as the unique hierarchical architecture, excellent electrochemical performance is obtained in the as-prepared Ni_3S_2 @NMV-L/rGO-15 composite, which exhibits a high specific capacity of 1412.0 C g~(-1) at 1 A g~(-1) as well as desirable long-term stability of 89% over 5000 cycles. Furthermore, the as-fabricated battery-supercapacitor hybrid device (BSH) based on Ni_3S_2@NMV-L/rGO-15 and activated carbon (AC) electrodes displays a remarkable energy density of 60.0 W h kg~(-1) at the power density of 849.1 W kg~(-1) and superior capacity retention of 96% through 7000 cycles. Such excellent results indicate that the Ni_3S_2 @ NMV-L/rGO-15 composite holds great potential as electrode material for high-performance BSHs.
查看更多>>摘要：As a burgeoning energy storage equipment, more attention has been paid to sodium ion hybrid super-capacitor (Na-HSC) with large energy/power density and long cycle life. Anode materials with high Na~+ embedding rate are the key for its development. In this work, multi-chamber microspheres with Nb_2O_5 quantum dots (T-Nb_2O_5@YC) were prepared from yeast enriched with Nb~(5+) and by simple hydrothermal-carbonization. Na~+ half-cell and Na-HSC have excellent electrochemical performance. To be specific, Na+ half battery with T-Nb_2O_5@YC delivers up to 195.7 mA h g~(-1) and maintains 84% discharge capacity after 2000 cycles. Moreover, Na-HSC assembled with T-Nb_2O_5@YC as anode has high energy density (62.5 Wh kg~(-1)) and power density (1250 W kg~(-1)).
查看更多>>摘要：ZnO has a large band gap, which affects its photoelectric catalytic performance to a certain extent. In this paper, Bi-doped ZnO nanoarray was successfully prepared by electrochemical deposition to improve the photoelectrochemical performance of ZnO as a photoanode. XRD results show the prepared Bi-doped ZnO is a typical hexagonal wurtzite crystal, and the SEM results also proved this point. The prepared Bi-doped ZnO presents a neat nano-array, and the doping of Bi also reduces the diameter of the nanorods from the original 500-350 nm. The results of XPS show that Bi is successfully doped into the ZnO nanoarrays, and it exists in the form of Bi_2O_3. Subsequently, the prepared Bi-doped ZnO was analyzed by fluorescence spectroscopy and photoelectrochemical properties, and it was found that when the doping concentration was 5%, the fluorescence intensity was the lowest, and at this time the carrier recombination rate corresponding was the lowest, the photoelectric catalytic effect was the best.
查看更多>>摘要：The stacking fault energy y of an alloy has been reported to significantly affect the grain size d and twin nucleation size r_c during grain refinement. However, ternary relation among y, d and r_c has not been investigated comprehensively. Here we prepared nanocrystalline (NC) and ultrafine-grained (UFG) 99.99 wt% Cu, Cu-0.86 wt% Al and Cu-2.2 wt% Al alloys with different y by high-pressure torsion (HPT), and then characterized d and r_c. Transmission electron microscopy observations show that under the same experimental condition d decreases and corresponding grain refinement mechanism transforms from dislocation subdivision to twin segmentation with decreasing y. The relation among y, d and r_c from experiments are consistent well with theoretical prediction from Meyers model. r_c decreases with decreasing d, and the variation is exacerbated by the decrease of y. r_c increases first and then decreases by forming a peak-shaped variation with decreasing y when d is in UFG regime, suggesting there exists an optimum stacking fault energy r_c for twin nucleation. The r_c peak becomes flat and moves to higher y value when d is in NC regime due to the enhanced geometric effect of d on r_c which weakens the role of y. Our findings reveal a comprehensive ternary relationship among y, d and r_c, and provide guidance for designing NC and UFG materials with high-density twins and good strength-ductility combination.
查看更多>>摘要：Hexaferrites are usually used in devices for frequencies of 8-75 GHz. In this work, it is shown that Sn-substituted hexaferrite can be used for electromagnetic shielding and at lower frequencies (for example, in the L-band and S-band) as absorbing materials. The paper defines a solid-state reaction technique for preparing BaFe_(12-x)Sn_xO_(19) (0.1 ≤ x ≤1.2). The samples are characterized by XRD, SEM, VSM, and VNA. The study shows that increasing the Sn-substitution leads to weakening the interaction between the magnetic sublattices. So, in general, the saturation magnetization (M_s) decreases. Low saturation magnetization at high coercivity values gives a high anisotropy field, which provides significant absorption and matching impedance. The sample with substitution of x = 1.2 is the most absorbing sample (more than 99.99% of the incident energy absorbed for 10 mm thickness). The investigated samples have the potential to be useful absorption materials for shielding production (materials that absorb electromagnetic radiation)
查看更多>>摘要：The synergistic effect of Zr addition and grain refinement on the corrosion resistance and pitting corrosion behavior of single α-phase Ti-Zr-based alloys was evaluated. The corrosion mechanisms of as-cast and hot-rolled Ti-xZr-4Al-0.005B alloys (x = 0,10, 20, 30, 40 wt%) in 5 M aqueous hydrochloric acid solution are investigated by analyzing their electrochemical and immersion corrosion behavior using scanning electron microscopy, electrochemical analyses, and X-ray photoelectron spectroscopy. Both Zr alloying and grain refinement improve the corrosion resistance; while grain refinement improves the stability of the passivation film, Zr addition increases the pitting sensitivity. Zr alloying and grain refinement greatly affects the pitting corrosion behavior in the alloy. In Ti or Ti-Zr alloys with low Zr content, grain refinement inhibits the appearance of corrosion pits inside the grains. For Ti-Zr alloys with higher Zr content, grain refinement induces small corrosion pits in the alloy. Grain refinement increases the frequency of corrosion pits in the Ti-Zr alloys with higher Zr content but inhibits the growth of the pits by improving the corrosion resistance and stability of the passivation film through the formation of more high-valence oxides and a thicker passivation film.
查看更多>>摘要：Constructing Z-scheme heterojunction is considered to be a promising strategy to isolate photogenerated carriers and boost the activity of the photocatalysts. Here in, a novel Z-scheme Bi_2WO_6/Ni-MOF heterojunction with intimate interface was constructed via wrapping flowerlike Bi_2WO_6 on 2D Ni-MOF sheets. The resultant Bi_2WO_6/Ni-M0F heterojunction displayed superior photocatalytic performance with respect to methylene blue degradation under visible light illumination. When the content of Ni-MOF was 20 wt%, the Bi_2WO_6/Ni-M0F heterojunction achieved the highest activity, which was 24.0 and 6.4 folds that of the pristine Ni-MOF and Bi_2WO_6, respectively. The superior degradation performance was caused by the formation of a direct Z-scheme heterostructure between Ni-MOF and Bi_2WO_6, which boosted the separation of photoinduced carriers. The principal active species and possible photocatalytic mechanism were also explored. This study provides a pathway to design and fabricate efficient Z-scheme photocatalysts for environmental remediation.
Nadendla Hari BabuHiiseyin DemirtasErdem Karakulak
8页
查看更多>>摘要：Investigations have been carried out to understand the correlation between Ni content and properties of HPDC cast A384 aluminium alloy in as-cast and heat-treated conditions. Depending on Ni content in the alloy, different Ni-bearing intermetallics were formed. Suitable heat treatment conditions were selected after a series of experiments to obtain optimal mechanical properties. Most of the Ni containing intermetallics found to be stable at solutionizing temperatures which have a dramatic effect on the mechanical properties of alloys after natural and artificial aging. The results showed that, after heat treatment, to achieve higher strength values lower Ni additions are favourable.
NSTL
Elsevier