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We developed a solid phase method to fabricate structurally ordered Pt3Co/C nanoparticles (NPs) with controllable component proportion as a high efficiency catalyst toward oxygen-reduction reaction. As a result, Pt3Co/C NPs exhibit high crystallinity with small average size and narrow size distribution. Moreover, the ordered Pt3Co/C NPs own enhanced ORR catalytic performance in acid. During the preparation process, the NaCl-matrix acts synergistically with carbon black as nanoreactors for Pt alloying with Co, avoiding serious sintering resulted by annealing at high temperature. Furthermore, other Pt-based NPs supported on carbon can also be prepared by this methodology.

Magnesium-substituted Ni–Zn ferrite (Ni0.5Zn0.5−xMgxFe2O4, x = 0–0.3, in steps of 0.05) has been successfully synthesized via a sol–gel–SHS (self-propagating high-temperature synthesis) method. The Fourier transform infrared spectra indicate the formation of spinel structure for Ni–Mg–Zn ferrites by sol–gel–SHS method. Thermogravimetric analysis reveals that the lowest decomposition temperature of SHS powder is approximately 400 °C. X-ray powder diffraction results signify a single-phase nature of cubic spinel structure for these samples without any detectable impurity phase. Lattice constant gradually decreases as the magnesium content continuously increases, while the average crystallite size increases except for undoped sample. Scanning electron microscopy images demonstrate that the samples consist of regular shaped grains without any phase segregation and agglomeration. Magnetization measurements indicate that all samples display a typical soft ferromagnetic characteristic with an abnormal saturation magnetization peak at x = 0.15. The frequency dependence of dielectric constant of the synthesized Ni–Mg–Zn ferrite exhibits a normal dielectric behavior, while the dielectric loss shows an abnormal peak behavior. The modulation mechanism for magnesium-substituted Ni–Zn ferrite on structure, electrical, and magnetic properties is systematically discussed.

Ni0.5Zn0.5Fe2−xCrxO4 (0≤x≤0.5) ferrites were successfully prepared by conventional solid state reaction method to investigate the effect of chromium substitution on the structural, electrical and magnetic properties. X-ray powder diffraction results demonstrate that all the prepared samples are well crystallized single-phase spinel structures without secondary phase. As chromium concentration increases, the lattice parameter and crystallite size gradually decrease. The magnetic measurement indicates that saturation magnetization is substantially suppressed by Cr3+ doping, changing from 73.5 A·m2/kg at x=0 to 46.3 A·m2/kg at x=0.5. While the room-temperature electrical resistivity is more than four orders of magnitude enhanced by Cr3+ substitution, reaching up to 1.1×108 Ω·cm at x=0.5. The dielectric constant monotonously decreases with rising frequency for these ferrites, showing a normal dielectric dispersion behavior. The compositional dependence of dielectric constant is inverse with that of electrical resistivity, which originates from the reduced Fe2+/Fe3+ electric dipole number by doping, indicating inherent correlation between polarization and conduction mechanism in ferrite.

Reduced graphene oxide (rGO) has attracted great attention as a promising electrode material for supercapacitors. Herein, polystyrene (PS) colloidal microsphere was used as spacers embedded in the ...

We report a novel Ni3S2 carbon coated (denoted as NCC) rod-like structure prepared by a facile one-pot hydrothermal method and employ it as a binder free electrode in supercapacitor. We coated carbon with glucose as carbon source on the surface of samples and investigated the suitable glucose concentration. The as-obtained NCC rod-like structure demonstrated great performance with a huge specific capacity of 657 C g−1 at 1 A g−1, preeminent rate capability of 87.7% retention, the current density varying to 10 A g−1, and great cycling stability of 76.7% of its original value through 3500 cycles, which is superior to the properties of bare Ni3S2. The result presents a facile, general, viable strategy to constructing a high-performance material for the supercapacitor applications.

Electrode materials with hierarchical nanoflakes structure show an important application potential in the efficient storage of electrochemical energy. In this work, a bimetallic sulfide NiCo2S4 with a novel controllable structure by adopting a layered double hydroxide (LDH) based on zeolitic imidazolate frameworks (ZIFs) template-oriented strategy is designed. The as-synthesized NiCo2S4 exhibits a hierarchical layered structure composed of nanoparticles with large specific surface area. This unique nanostructure provides abundant electrolyte-accessing sites and sufficient contact between the electroactive materials and electrolytes. As a result, the porous NiCo2S4 electrode exhibits a high specific capacity of 968 C g−1 at 1 A g−1 and an extraordinary rate capability of 91% at the current density of 10 A g−1. Furthermore, a hybrid supercapacitor is assembled with NiCo2S4 as the positive electrode and activated carbon as the negative electrode. The as-prepared device can deliver a high specific energy of 45.1 Wh/Kg at a high specific power of 699.7 W/Kg and its long-term cycling stability can reach 74.7% after 20000 cycles.

Sm3+-Modified (1 -x)Na0.5Bi0.5TiO3-xCaTiO3 (NBT-xCT:Sm3+) piezo-luminescent ceramic materials were synthesized to investigate the influence of CaTiO3 (CT) concentration on their photoluminescence and electrical performance. Under 480 nm irradiation, the NBT-xCT:Sm3+ samples exhibit prominent orange-red emission, with a prime emission peak centered at 597 nm. A moderate amount of CT doping in the Sm3+-modified NBT ceramics boosts both their photoluminescence and piezoelectric properties significantly, with NBT-0.04CT:Sm3+ showing the optimal performance. Furthermore, outstanding luminescence thermal stability over a temperature range of 293-473 K and superior water resistance behavior are achieved in the NBT-0.04CT:Sm3+ ceramic. These results indicate that NBT-xCT:Sm3+ piezo-luminescent ceramics show great potential applications in white LEDs, as well as novel optical-electronic multifunctional devices.

Herein, we report the preparation of an effective and novel NiCo2O4 dendritic structure with nanothorn arrays, using a stepwise, bottom-up hydrothermal and self-sacrificial template method. Rod-like ZnO is synthesized on Ni foam as self-sacrificing template, and Ni-Co-based precursor is grown on it through a hydrothermal method. NiCo2O4 dendritic crystals are obtained by alkali etching of the template and calcination, which significantly enhance its performance on electrochemical energy storage. Although the ZnO matrix is removed by alkali etching, it provides a basis for the growth of Ni-Co oxide. Using ZnO as template is simple to operate and can directly determine the shape and size of the hollow structure. Meanwhile, the ZnO template core can be well separated from the hollow structure, and the template can be used without surface functionalization, which is more simple and efficient. The obtained material can be directly used as electrode material without further processing, offering the benefit of unique structural advantages and low electron transmission resistance, as there is no need to use a binder. The as-obtained NiCo2O4 nanothorn electrode exhibits excellent electrochemical performance. It shows ultrahigh specific capacitance of 1534 C g-1 at 1 A g-1 current density, good rate discharge performance (75.8% retention from 0.5 A g-1 to 5 A g-1), values superior to those of nanothorn NiO, Co3O4 and bare Ni-Co 1-2 nanosheet structures and excellent cycling ability (83% retention after 5000 cycles). The as-assembled Ni-Co 1-2//AC hybrid supercapacitor device also exhibits high energy density of 64.1 Wh kg-1 at the power density of 450 W kg-1.

A facile two-step method is developed for large-scale synthesis of chemically ordered Pt3Co nanoparticles (NPs) as a high-performance catalyst for hydrogen evolution reaction. Due to the NaCl-matrix as dispersing media avoids the severe aggregation during the high-temperature annealing process, the resulting Pt3Co NPs are pure and well crystallized with narrow size distribution. Furthermore, the chemically ordered Pt3Co NPs exhibit excellent HER property in acidic solution. Our methodology can be also applied to synthesis of other Pt-based NPs.

Herein, a novel preparation route of bimetallic spherical core-shell particles of immiscible metal system was developed and demonstrated through the synthesis of Fe@Cu core–shell microsphere particles. Copper ferrite (CuFe2O4) was used as precursor for the preparation of the Core–shell structured Fe@Cu microsphere using the solid-state immiscibility of Fe and Cu and the low wettability strategy of the liquid-solid interface of graphite at 1403 K. The results showed that phase separation occurred between Cu and Fe, where Cu tended to move towards the surface of the particles and Fe was more concentrated in the center of the particles, due to the lower surface energy of liquid Cu with respect to solid Fe. This was followed by formation of metal droplets located on loose graphite flakes on the spherical Fe@Cu due to the solid-liquid interfacial tension. The as-prepared Fe@Cu microsphere exhibited good spherical shapes and smooth surfaces. The cross-sectional micrographics and element mapping of the spherical particles confirmed the evenly distributions of the Fe-rich core and Cu-rich shell. This strategy is promising for the fabrication of core–shell structured spherical particles for immiscible alloys.

Nickel cobalt sulfide hollow micro-/nanostructures have received extensive attention as potential electrode materials for electrochemical energy storage due to its attractive structure, reach chemistry and excellent conductivity. Compare to ordinary hollow materials, multi-shelled hollow structures apparently have more advantages in specific surface area, energy density and structure stability. Herein, we successfully prepared multi-shelled NiCo2S4 hollow microspheres and pioneered its application in supercapacitors. The multi-shelled NiCo2S4 hollow microspheres show high specific capacity of 1521.3 F g−1 at a current density of 0.5 A g−1. The asymmetric supercapacitor with a positive electrode of multi-shelled NiCo2S4 hollow microspheres and a negative electrode of active carbon reveals excellent energy density of 58.18 Wh kg−1 at the power density of 400.03 W kg−1, and only 14.51% energy density fade after 5000 cycles. Such striking electrochemical performances make the multi-shelled NiCo2S4 hollow microspheres promising for high performance supercapacitors.

Co3O4 as an electrode material has been widely used for energy storage. However, it has low capacity and is generally associated with poor cycle life and stability. We designed the Co3O4 hollow tube arrays on Ni foam though a facial strategy based on the ZnO sacrificial template method. Benefit from the unique hollow structure advantage and the low resistance brought by the use of self-supporting method without binder. Compared to Co3O4 directly grown on a substrate, the as-prepared hollow Co3O4 structure exhibits large electrochemical capacity of 748.1 C g−1 at 1 A g−1, the result is larger than that of pure Co3O4 directly growing on the substrate without adding Zn2+ as the template. Furthermore, a hybrid supercapacitor device Zn@Co//AC reaches the specific energy of 60.91 Wh kg−1 under the specific power of 450 W kg−1.

Monodisperse spherical Cu-Sn alloy powders were successfully synthesized via the reduction of mixture CuO-SnO2 powders coupled with in-situ de-wetting of liquid-solid interface. The alloy droplets were divided into small units using a graphite sea as solid dispersant to suffer from agglomeration. Fully dense without pores and bulk inclusions, the cross-sectional micrographics of the spherical alloy particles indicate an evenly distribution of the Cu and Sn. The Cu-Sn alloy powders exhibit a good spherical shape and smooth surface, suggesting that the liquid Cu-Sn alloy completely de-wets from the graphite surface. Our strategies are expected to provide a new route for fabrication of high-quality spherical Cu-Sn alloy powders via the reduction of mixture metal oxides.

Here, we present a liquid–solid method (termed “LS method”) for the formation of spherical metal powders. By taking advantage of the low wettability of metal liquids on a solid powder, spherical metal droplets were formed under the influence of interfacial and surface tension, as demonstrated for copper, silver, aluminum, copper–tin alloy, copper–zinc alloy, and amorphous magnetic iron–silicon–boron materials. This LS method is a versatile and universal route and would be applied in powder metallurgy, 3D printing and metal injection modeling. We believe this method provide an additional way for the formation of spherical metal powders. Keywords: Surface energy, Interface wetting, Powder processing

Nitrogen-doped graphene deposited on nickel foam was prepared via a simple hydrothermal process using urea as the reducing agent and nitrogen source and was directly applied as a binder-free supercapacitor electrode. The N content was 5.01 at. %. The electrochemical test of the prepared N-doped graphene showed ideal and reversible capacitive behaviour and excellent electrochemical performance, with a high specific capacitance of 223 F g−1 at 0.29 A g−1, a high-rate capability with the specific capacitances maintained at 184 F g−1 at a high rate of 35.7 A g−1, and good cycling stability with the specific capacitance of the N-doped graphene increased to 206 F g−1 after 3000 cycles. The results suggest its promising application as an electrode material for supercapacitor.

Here, porous grapheme oxide (GO) gel deposited on nickel foam was prepared by using polystyrene (PS) colloidal particles as spacers for use as electrodes in high rate supercapacitors, then reduced by Vitamin C aqueous solution in ambient condition. The PS particles were surrounded by reduced graphene oxide (rGO) sheets, forming crinkles and rough textures. When PS particles were selectively removed, rGO gel coated on the skeleton of Ni foam can formed an open porous structure, which prevents elf-aggregation and restacking of graphene sheets. The porous rGO-based supercapacitors exhibit excellent electrochemical performances such as a specific capacitance of 152 F g−1 at 1 A g−1, high rate capability of 53% capacitance retention upon a current increase to 100 A g−1 and good cycle stability, due to effective rapid and short pathways for ionic and electronic transport provided by the sub-micrometer structure of rGO gel and 3D interconnected network of Ni foam.

Spherical Fe-based magnetic powders were obtained by taking advantage of the surface tension of a molten metal and the de-wetting of metal droplets on a solid graphite sea. The surface carbides inhibit the interfacial reaction and suppress the wetting of the alloy in the graphite substrate. Cross-sectional micrographs of the spherical particles indicate that the particles are fully dense without pores and bulk inclusions. The amorphous degree of the spherical powder was improved by directly quenching in water compared to the raw materials, and the directly quenched sample exhibits excellent soft magnetic properties. Our strategy is expected to provide a new route for the fabrication of spherical insulation coated Fe-based magnetic powders for use in high frequency devices as magnetic core powders.

Spherical Cu–Zn alloy powders were fabricated by combining the surface tension of a molten metal with the de-wetting of a metal droplet on a graphite surface. The effect that the gas pressure had on the surface morphology and composition was studied. The Zn concentration can be maintained at 20.18 wt.%, 15.5 wt.% and 12.08 wt.% using 0.22 MPa, 0.10 MPa, and 0.04 MPa, respectively, from a commercially available Cu–38 wt.%Zn raw material. The gas pressure was adjusted to control the surface volatility of Zn without affecting the spherical morphology, and higher gas pressure yielded less volatile Zn. The Cu–Zn alloy powders were perfectly spherical, even at a negative pressure of 0.04 MPa. The spherical Cu–Zn alloy particles hardly changed and were fully dense up to Cu–50 wt.%Zn, which allowed high-quality spherical Cu–Zn alloy powders to potentially serve a large composition range.

Here, we demonstrate the design of a binder-free reduced graphene oxide (rGO) and polystyrene colloidal microsphere (PS) compound with rGO/PS/rGO sandwich structure and application for supercapacitors electrode. rGO and PS are alternately deposited into 3D Ni foam by a simple layer-by-layer assembly based on dip-coating. The interlayer space of rGO film expanded by PS microsphere and 3D structure of compound electrode can effectively shorten diffusion pathways of ions and accelerate the transport of ions into graphene sheets. The resulting rGO/PS compound electrode exhibits a high specific capacitance with 164.7[Formula: see text]F g[Formula: see text], and outstanding rate capability. It is found that the specific capacitance is dependent on the number of rGO film layers in rGO/PS compound electrode.

We report a pure ferromagnetic metallic magnetoplasmonic structure consisting of two-dimensional ordered Ni nanodisks array on Co film. With a sufficient height of the nanodisks, a steep and asymmetric Fano resonance can be excited in this structure. We attribute the fascinating spectral lineshape to the strong coupling between the excitation of surface plasmon polaritons at the interface and the localized surface plasmon resonance of nanodisks. The conclusion is fully confirmed by spectrum measurements in nanostructures with different heights. Furthermore, the enhancement and sign of the magneto-optical Kerr rotation in this structure are significantly modified by the Fano resonance.

The properties of optics and magneto-optical Faraday effects in a metal-dielectric tri-layer structure with subwavelength rectangular annular arrays are investigated. It is noteworthy that we obtained the strongly enhanced Faraday rotation of the desired sign along with high transmittance by optimizing the parameters of the nanostructure in the visible spectral ranges. In this system, we obtained two extraordinary optical transmission (EOT) resonant peaks with enhanced Faraday rotations, whose signs are opposite, which may provide the possibility of designing multi-channel magneto-optical devices. Study results show that the maximum of the figure of merit (FOM) of the structure can be obtained between two EOT resonant peaks accompanied by an enhanced Faraday rotation. The positions of the maximum value of the FOM and resonant peaks of transmission along with a large Faraday rotation can be tailored by simply adjusting the geometric parameters of our models. These research findings are of great importance for future applications of magneto-optical devices.