Nickel Hollow Spheres Research Articles

Hollow nickel sources for improving nickel utilization in Zebra batteries

The Zebra (Na-NiCl2) batteries are regarded as a promising option for large-scale electrical energy storage due to their plentiful electrode material resources, high energy density, and safety features. In the cathode of Zebra battery, the nickel powders serve as both an active material and a conductive agent. In practice, its amount is significantly greater than its theoretical usage, often exceeding three times the theoretical amount. Hence, the presence of ultra-excessive nickel results in high material costs, posing obstacles to the wider implementation of Zebra batteries. To address this problem, we introduce hollow nickel source as active material to improve the nickel utilization in Zebra battery. In this work, we assemble Zebra batteries using nickel hollow spheres (NHS) with sizes of ∼200 nm, ∼500 nm, ∼1 μm and ∼ 5 μm as nickel source. The battery using NHSs with a size of 1 μm exhibits the best cycling performance and the lowest polarization voltage. By reducing the Ni(NHS, ∼1 μm)/NaCl mass ratio to 1.0, 60% theoretical capacity can be achieved after 170 cycles at 260 °C, which surpasses the traditional batteries using solid nickel source at the same Ni/NaCl ratio. This performance is comparable to that of traditional solid nickel sources with a mass ratio of 1.5 to NaCl. Therefore, using NHS as the nickel source in Zebra batteries reduces nickel usage by 33% without compromising performance.

Preparation, compression behavior and 3D damage evolution of epoxy syntactic foam with nickel hollow spheres

The nickel thin-walled hollow spheres (NHS) epoxy syntactic foam was fabricated by the infiltration method. The crystal structure and grain size of the NHS were quantitatively analyzed by FIB-TEM. The bulk compressive response of the NHS syntactic foam was determined and compared with glass bubble syntactic foam. The X-ray computed microtomography (XCT) coupling with the interrupted compression tests were conducted on a single NHS and the NHS syntactic foam to demonstrate the 3D deformation history. The bulk behaviors of the NHS syntactic foam were correlated with the XCT examinations to analyze the mechanisms of the failure process. The electrodeposited NHS shows the nanocrystalline and polycrystalline microstructure. The low air void content was achieved in the NHS syntactic foam produced by the infiltration method. Although the NHS syntactic foam's elasticity and yield strength are lower, the compressive resistance and toughness as well as the energy absorption of the NHS syntactic foam are higher than those of glass syntactic foam. The failure process of the NHS syntactic foam is dominated by the NHSs deformation and the resultant strain hardening. The damage initiates from the weak NHSs, then more crushed bands arise with the increased compressive stress. The further deformation of the damaged bands can intermittently develop owing to the strain hardening. During the deformation history, no visible macro cracks can be found in the epoxy matrix from the XCT slices.

Nickel Hollow Spheres Concatenated by Nitrogen-Doped Carbon Fibers for Enhancing Electrochemical Kinetics of Sodium-Sulfur Batteries.

The high energy density of room temperature (RT) sodium–sulfur batteries (Na‐S) usually rely on the efficient conversion of polysulfide to sodium sulfide during discharging and sulfur recovery during charging, which is the rate‐determining step in the electrochemical reaction process of Na‐S batteries. In this work, a 3D network (Ni‐NCFs) host composed by nitrogen‐doped carbon fibers (NCFs) and Ni hollow spheres is synthesized by electrospinning. In this novel design, each Ni hollow unit not only can buffer the volume fluctuation of S during cycling, but also can improve the conductivity of the cathode along the carbon fibers. Meanwhile, the result reveals that a small amount of Ni is polarized during the sulfur‐loading process forming a polar Ni—S bond. Furthermore, combining with the nitrogen‐doped carbon fibers, the Ni‐NCFs composite can effectively adsorb soluble polysulfide intermediate, which further facilitates the catalysis of the Ni unit for the redox of sodium polysulfide. In addition, the in situ Raman is employed to supervise the variation of polysulfide during the charging and discharging process. As expected, the freestanding S@Ni‐NCFs cathode exhibits outstanding rate capability and excellent cycle performance.

Micromagnetic Simulation in Hexagonal Arrays of Nanosized Hollow Nickel Spheres

Arrays of nanosized hollow spheres of Ni were studied using micromagnetic simulation by the Object Oriented Micromagnetic Framework. Before all the results, we will present an analysis of the properties for an individual hollow sphere in order to separate the real effects due to the array. The results in this paper are divided into three parts in order to analyze the magnetic behaviors in the static and dynamic regimes. The first part presents calculations for the magnetic field applied parallel to the plane of the array; specifically, we present the magnetization for equilibrium configurations. The obtained magnetization curves show that decreasing the thickness of the shell decreases the coercive field and it is difficult to obtain magnetic saturation. The values of the coercive field obtained in our work are of the same order as reported in experimental studies in the literature. The magnetic response in our study is dominated by the shape effects and we obtained high values for the reduced remanence, $M_{r}/M_{S} = 0.8$ . In the second part of this paper, we have changed the orientation of the magnetic field and calculated hysteresis curves to study the angular dependence of the coercive field and remanence. In thin shells, we have observed how the moments are oriented tangentially to the spherical surface. For the inversion of the magnetic moments we have observed the formation of vortex and onion modes. In the third part of this paper, we present an analysis for the process of magnetization reversal in the dynamic regime. The analysis showed that inversion occurs in the nonhomogeneous configuration. We could see that self-demagnetizing effects are predominant in the magnetic properties of the array. We could also observe that there are two contributions: one due to the shell as an independent object and the other due to the effects of the array.

Fabrication and microwave properties of hollow nickel spheres prepared by electroless plating and template corrosion method

Using carbonyl iron as template, hollow nickel spheres were prepared by electroless plating on carbonyl iron and template corrosion method. The samples were characterized by X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), transmission electron microscope (TEM), scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and vector network analyzer. Results showed that the shell thickness can be controlled by adjusting the loadage of carbonyl iron templates. The hollow nickel spheres exhibited good magnetic properties with a saturation magnetization of 48.56emu/g and enhanced coercivity (as high as 260Oe). The real (ε′) and imaginary (ε″) parts of complex permittivity of hollow nickel spheres first increased and then decreased as the shell thickness increased, and the sample with the thinnest shell showed the lowest complex permittivity. For the complex permeability, the resonance peak shifted to the lower frequency and then moved to higher frequency, as the shell thickness increased. The microwave absorption performances could be tuned by changing the shell thickness. In this study, the minimum reflection loss (RL) value of −27.2dB was obtained at 13.4GHz with a matching thickness of 1.4mm and the effective absorption band (RL <−5dB) from 11.8 to 18GHz, covering the whole Ku-band (12.4−18GHz).

Size Influence on Magnetic Properties of Nickel Hollow Spheres

Nickel hollow spheres (NHSs) with different diameter have been synthesized by the autocatalytic reduction method. The morphology, size distribution and magnetic properties of NHSs were characterized. The results indicate that when the nickel hollow spheres become smaller, mechanism of magnetization reversal varies from motion of domain wall to spin coherent rotation. After the heat treatment process, the grain size of samples becomes bigger and coercivity is enhanced because domain wall is pinned by local magnetic anisotropy induced spontaneously.

Facile synthesis of hollow and porous nickel microspheres by low temperature molecular self-assembly

Hollow and porous nickel microspheres with potential applications as catalysts, magnetic materials, and adsorbing materials were synthesized by self-assembly in an aqueous medium in which hydrazine hydrate acted as the reducing agent. The crystal structure, phase, particle size and magnetic performance of the hollow nickel microspheres were characterized and the effects of the template, pH value, temperature, and reaction time were evaluated. Uniform hollow nickel spheres with porous structures could be obtained at 75 °C and pH of 9–10 with a heating time of 30 min. The average diameter of the spheres was 1.4 μm and mean thickness of the sphere wall was 120 nm. Polyvinyl pyrrolidone (PK40) played an important role in the formation of the spherical template which controlled the formation of hollow spheres. Magnetic measurements indicated that the hollow nickel spheres are soft-magnetic materials with much lower coercivity and much higher saturation magnetization compared to the nickel crystals with irregular shapes.

Fabrication of Nickel hollow spheres by microemulsion–template–interface reaction route

Ni hollow spheres (NHSs) have been successfully synthesized through a microemulsion–template–interface reaction route. The structures of NHSs were characterized by X-ray powder diffraction (XRD), selected area electron diffraction (SAED), transmission electron microscopy (TEM). The results showed that the size of the NHSs was between 50 to 150 nm. The shell thickness of the NHSs is about 20 nm. In our method, the metal precursor and reducing agent dissolved in two different phases; they can react at oil/water interface. Thus, hollow spheres can be fabricated more easily.

Surface-modified micrometre nickel hollow spheres and their microwave characteristics

To improve the magnetic properties, nickel hollow spheres (NHSs) were surface-modified with a cellular Co structure by a facile electroless cobalt plating route. The microstructures and properties of the modified NHSs were characterized by field emission scanning electron microscopy, x-ray diffraction, Brunauer–Emmett–Teller specific surface area and a vibrating sample magnetometer. Microwave properties were evaluated by mixing NHSs with polyvinyl butyral as coaxial samples. The SEM images showed that the NHSs were coated by the Co cellular films, which not only increased the specific surface area but also enhanced the coercivity and magnetization. Also, the modified NHSs composites presented low RL min values below −30 dB at thicknesses between 1.0 and 2.0 mm, and exhibited a broad absorption bandwidth ΔW at ‘thin’ thickness.

Metallic Hollow Sphere Structures Manufacturing Process

AbstractThis paper focuses on manufacturing process of regular Metallic Hollow Sphere Structures (MHSS) through brazing technique. As a large stress level is generally confined into the necks formed by brazed spheres, the influence of the filler material on mechanical behavior of cellular metal has been studied. The microstructures of joints resulting from nickel hollow spheres brazing with different commercial fillers “MBF 30” and “MBF 1006” were compared by Scanning Electron Microscopy (SEM) and microhardness testing. These studies revealed a wide boron diffusion into nickel shells through grain boundaries for “MBF 30” brazing, with the formation of borides in a fine brittle eutectic structure. Conversely it was observed that the eutectic structure concentrates at the necks for “MBF 1006” and can be completely eliminated by diffusion-brazing, despite of the shells thinness. The uniaxial compressive tests of HSP specimens have shown two different strain mechanisms depending on brazing process.

Preparation and microwave absorption properties of electroless Co–P-coated nickel hollow spheres

Co–P-coated nickel hollow spheres (NHSs) were prepared by electroless plating technology. The morphology and component content of Co–P coating varies with the change of sodium citrate concentration in elctroless plating solution. And as phosphorus content increases in coatings, resulting in smaller grain, coercivity of microspheres decreases. The microwave absorption properties of spheres–wax composite were investigated in the range of 2–18 GHz. Both permittivity and permeability increase with an increase of cobalt content in coatings. For composite layer, a minimal reflection loss (RL, −36.9 dB) of was predicted at 8.1 GHz with a thickness of 3 mm.

Size influence on optical absorption property of ultra-fine nickel hollow spheres

Nickel hollow spheres (NHSs) with different diameter have been synthesized by the autocatalytic reduction method. The morphology, particle size distribution and optical absorption property of NHSs were investigated. The optical absorption intensity obviously increases in ultraviolet—near infrared region with the decrease of particle size. While in infrared region, nickel hollow spheres have almost no absorption. After the heat treatment process, the grain sizes of samples become bigger and the absorptances decrease in UV–Vis–NIR region. For smaller particles, the absorption peak in ultraviolet range moves from 375 to 440 nm because of the increase of grain size after heat treatment.

Synthesis of mono-disperse hollow nickel spheres with a double shell structure using poly(methyl methacrylate) as a template

Mono-disperse hollow SiO 2 /Ni magnetic spheres were successfully manufactured by radiofrequency magnetron sputtering and sol–gel methods using poly(methyl methacrylate) spheres as template. After removing core templates, the hollow structure of the SiO 2 /Ni magnetic spheres was characterized by electron microscopy and the magnetic properties were measured by vibrating sample magnetometry. Finally, the anti-oxidation test shows that the inert SiO 2 layer can protect the hollow nickel spheres from oxidization in the air very well.

Preparation of monodisperse Ni/PS spheres and hollow nickel spheres by ultrasonic electroless plating

Monodisperse Ni/PS spheres with polystyrene (PS) core and nickel shell were fabricated by ultrasonic electroless plating. Hollow nickel spheres were consequently prepared by calcination and reduction of these Ni/PS spheres at high temperature. The samples were characterized by SEM, TEM, XRD, TG, TPR and EDX. The effects of sensitization time and agitation type on the preparation and dispersity of the Ni/PS spheres were examined. The results indicated that long sensitization time was necessary for the uniform deposition of nickel on the surfaces of the PS spheres. Ultrasonic waves could prevent the polystyrene spheres and Ni/PS spheres from agglomeration, and enhanced the rate of reaction in electroless plating. Optimum electroless plating conditions were found to be as that the polystyrene spheres were sensitized for 30 min, followed by electroless plating for 5 min in the presence of ultrasonic wave. The hollow nickel spheres were consequently obtained by calcining these Ni/PS spheres in air at 550 °C for 4 h and reducing in hydrogen at 550 °C for 3 h.

Microwave characterization of submicrometer-sized nickel hollow sphere composites

In this work, we report on the microwave properties of the nickel hollow spheres (NHSs) synthesized by a facile autocatalytic reduction method. The resonance characterization of the NHS-polyvinyl butyral composite, due to the skin effect, is observed in the microwave frequency. It is shown that the resonant and the matching frequencies of the composite largely depend on the particle size of the spheres.

Preparation and microwave characterization of submicrometer-sized hollow nickel spheres

The hollow structural submicrometer-sized nickel spheres were successfully fabricated by the autocatalytic reduction method. Because of the metallic and ferromagnetic behaviour of the nickel spheres, the low-density microspheres could obtain high dielectric constant and magnetic loss in microwave frequencies. The abrupt variation of the real part and the sharp peaks of the imaginary part of permittivity and permeability were observed for the micrometer-sized and nanometer-sized nickel hollow spheres. Reflection loss less than −25 dB were predicted over 11 GHz with a thickness of 1.5–2.0 mm.

Nanometer‐Sized Nickel Hollow Spheres

Nanometer‐Sized Nickel Hollow Spheres

Submicrometer-sized hollow nickel spheres synthesized by autocatalytic reduction

A facile method to fabricate submicrometer-sized hollow nickel spheres by autocatalyzing the redox reaction around a sacrificial colloidal particle surface is presented in this paper. The size distribution of these spheres can be controlled by regulating the concentration of the alkali solution. The hollow nickel particles were characterized by field emission scanning electron microscopy, transmission electron microscopy and X-ray powder diffraction. The hollow spheres produced by this process may have potential applications in many fields, including chemistry, biotechnology and materials science.

Nanometer‐Sized Nickel Hollow Spheres

Hollow nickel spheres of 50–60 nm diameter have different properties from bulk nickel. For example, the authors demonstrate that the spheres exhibit a long-range magnetic-ordering transition at 575 K and enhanced coercivity. The facile synthesis of such spheres by mild hydrothermal redox reaction of nickel dodecylsulfate with NaH2PO2 (see Figure) is described.