Hollow Anode Research Articles

Collimated electron beam accelerated at 12 kV from a Penning discharge.

A pulsed electron beam accelerated at 12 kV with a duration of 40 μs per pulse is obtained from a Penning discharge with a hollow anode and two cathodes. The electrons are extracted through a hole in one of the cathodes and focused by a pair of coils. The electron beam has a diameter of a few mm in the cross section, while the beam current reaches peak values of 400 mA, depending on the magnetic field inside the focussing coils. This relatively inexpensive and compact device is suitable for the irradiation of small material samples placed in high vacuum.

An alumina stabilized graphene oxide wrapped SnO2 hollow sphere LIB anode with improved lithium storage

SnO2 hollow spheres were stabilized by graphene oxide wrapping, by alumina coating deposited via atomic layer deposition (ALD), or the combination of the two methods and used in lithium ion battery anodes.

Small-size plasma diode with a transparent internal cathode for neutron generation

A discharge plasma system for neutron generation based on the concept of inertial electrostatic confinement is considered. The system is made in the form of a gas-filled (1–60 Pa) diode with a composite hollow cathode placed at its center symmetrically to an embracing hollow cylindrical anode. Preionization of the discharge gap and an original design of the electrode system with a transparent central part make it possible to initiate a pulse high-voltage (100–150 kV) volume discharge in the ion oscillation mode. Estimates of the neutron emission in such a deuterium-filled diode show the feasibility of generating a pulse with a neutron yield on the order of 105 in the reaction D(d, n)3He, which is confirmed in experiments with an optimized geometry of the electrodes.

Stress-modulated driving force for lithiation reaction in hollow nano-anodes

Lithiation of a crystalline silicon anode proceeds by the movement of an atomically sharp reaction front that separates a pristine crystalline phase and a fully-lithiated amorphous phase. The velocity of the reaction front is limited rather by the reaction rate at the lithiation front than by the diffusivity of lithium ions in the amorphous lithiated phase. Experiments on solid nanoparticle/nanowire silicon anodes show an initial rapid advancing of reaction front at the initial stage of lithiation, followed by an apparent slowing or even halting of the reaction front propagation. Lithiation-induced stresses during lithiation are attributed to alter the driving force of lithiation and thus result in the observed slowing of reaction front. Recent experiments on lithiation of hollow silicon nanowires reveals similar slowing of reaction front, however, quantitative study of the effect of lithiation-associated stress on the driving force of lithiation still lacks so far. Here, through chemo-mechanical modeling and theoretical formulation, we present a comprehensive study on lithiation-induced stress field and its contribution to the driving force of lithiation reaction in hollow silicon nanowire anodes. We show that hollow silicon nano-anodes could be fully lithiated with lower stress-induced energy barrier than solid silicon nano-anodes. As a result, it is expected that the hollow nanowires and nanoparticles may serve as an optimal structural design for high-performance anodes of lithium-ion batteries. Results from the present study shed light on a number of open questions of lithiation kinetics of silicon-based anodes in recent literature and offer insight on developing silicon-based anodes with high charging capacity and high charging rate.

Li4Ti5O12/TiO2 hollow spheres composed nanoflakes with preferentially exposed Li4Ti5O12 (011) facets for high-rate lithium ion batteries.

Li4Ti5O12/TiO2 hollow spheres composed of nanoflakes with preferentially exposed Li4Ti5O12 (011) facets have been successfully fabricated via a facile hydrothermal processing route and following calcination. These hollow spheres show good electrochemical performance in terms of high capacity (266 mAh g(-1) at 0.1 A g(-1)), and excellent rate capability (110 mAh g(-1) at 4.0 A g(-1) up to 100 cycles), attributed to unique morphology, preferred facet orientation of the nanoflakes and microscopic structure of the hollow spheres. The preferentially exposed Li4Ti5O12 (011) facets leads to fast lithium insertion/deinsertion processes in materials because of shorten lithium ion diffusion length, proved to be highly effective in improving the electrochemical properties of the hollow spheres. The excellent electrochemical performance makes these hollow spheres promising anode material for lithium ion batteries with high power and energy densities.

Microstructure tailoring of the nickel oxide-Yttria-stabilized zirconia hollow fibers toward high-performance microtubular solid oxide fuel cells.

NiO-yttria-stabilized zirconia (YSZ) hollow fiber anode support with different microstructures was prepared using a phase-inversion method. The effect of the solid loading of the phase-inversion suspensions on the microstructure development of the NiO-YSZ anode support was investigated. Solid loading in the suspension was found to have an important influence on the microstructure of the NiO-YSZ anode support and viscosity-related viscous fingering mechanism can be adopted to explain the pore formation mechanism of the as-prepared hollow fibers. NiO-YSZ anode-supported microtubular solid oxide fuel cells (SOFCs) with different anode microstructures were fabricated and tested, and the correlation between the anode support microstructures, porosity, gas permeability, electrical conductivity, and the cell electrochemical performance was discussed. Microtubular SOFCs with a cell configuration of Ni-YSZ/YSZ/YSZ-LSM (LSM = (La(0.8)Sr(0.2))(0.95)MnO(3-x)) and optimized anode microstructure show cell output power density of 833.9 mW cm(-2) at 750 °C using humidified H2 as fuel and ambient air as oxidant.

Fabrication and evaluation of stable micro tubular solid oxide fuel cells with BZCY-BZY bi-layer proton conducting electrolytes

Anode-supported proton conducting micro tubular solid oxide fuel cells (MT-SOFCs) with the configuration of Ni–BaZr0.1Ce0.7Y0.2O3-δ (BZCY)/BZCY/BaZr0.8Y0.2O3-δ (BZY)/La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)-BZY have been prepared by a combination of phase inversion method and suspension-coating technique. The obtained Ni-BZCY anode hollow fiber presents a special asymmetrical structure consisting of a sponge-like layer and a finger-like porous layer, which is propitious to anode electrochemical process. Bi-layer electrolytes consisting of 5 μm thick BZCY and 3 μm thick BZY are successfully fabricated by suspension-coating technique. BZY electrolytes are placed at the cathode side, in order to improve the chemical stability against CO2. The considerable electrochemical performance and good stability in the presence of CO2 indicate that the construction of BZY-BZCY bi-layer electrolytes is an effective way for the development of stable proton conducting MT-SOFCs.

Multiple Fireballs in a Reactive <inline-formula> <tex-math notation="TeX">${\rm H}_{2}/{\rm CH}_{4}$ </tex-math></inline-formula> Plasma

Inverted fireballs (FBs) are plasma phenomena, which develop inside a highly transparent, positively biased grid electrode through electron impact ionization. The ionizing electrons are accelerated into the grid by the high potential on the wires. This leads to an enhanced plasma density inside the hollow anode as well as a strong light emission. FBs show a wide variety of properties. This behavior may manifest itself in different shapes of FBs, which are very sensitive to the physical parameters of the discharge.

Investigation of Hot Cathode and Hollow Anode of Argon Glow Discharge Plasma

Hot cathode and hollow anode argon DC glow discharge plasma at different pressures of (0.04, 0.05, 0.06, 0.07, 0.09, 0.2, 0.4, and 0.8 mbar) has been investigated. The experiments were carried out under the influence of pressure and filament cathode current on voltage – current characteristics of glow discharge and its breakdown voltage. Plasma parameters have been measured and obtained using single probe method at fixed discharge current (Id=1.88 mA) and hollow anode diameter. A computer MATLAB program is performed for this purpose. It was shown that the discharge voltage – current characteristics curve has a positive resistance and represents an abnormal glow region at pressure (0.04 and 0.06) mbar for different filament current. The breakdown voltage increases as the filament current is increased. In different pressure, electron temperature shows different behavior with increasing filament current. Electron density varies nearly inversely with the filament current, but it is increase due to increase of pressure from (1 to 3 mbar), then tends to decrease for the higher pressure. There are two groups of electrons according to the two peaks of (EEDFs), and the peaks amplitude decrease, with the increases of both filament current and gas pressure.

On the dispersion relation of the transit time instability in inverted fireballs

Recently discovered inverted fireballs are non-linear plasma phenomena, which are formed in hollow grid anodes with high transparency in an existing background plasma. If a sufficiently large potential is applied, accelerated electrons from the bulk start to oscillate through the grid. Experimental investigations have shown that they produce different types of plasma instabilities. One of those oscillations is a transit time instability which originates from strong electron beams that travel through the inverted fireball. This type of instability is similar to vircator reflex oscillations and produces radio frequency waves. Hence, it is suitable to convert DC signals into signals oscillating in the MHz range. This paper analyses the dispersion relation of the transit time instability for three different plasma regimes. The regimes can be divided into a collision less regime, a regime with high collisionality and one in between those former two. It is demonstrated that the plasma properties of the surrounding background plasma have a strong influence on the behavior of the instability itself.

Influence of water conductivity on particular electrospray modes with dc corona discharge — optical visualization approach

The effect of water conductivity on electrospraying of water was studied in combination with positive DC corona discharge generated in air. We used a point-to-plane geometry of electrodes with a hollow syringe needle anode opposite to the metal mesh cathode. We employed total average current measurements and high-speed camera fast time-resolved imaging. We visualized the formation of a water jet (filament) and investigated corona discharge behavior for various water conductivities. Depending on the conductivity, various jet properties were observed: pointy, prolonged, and fast spreading water filaments for lower conductivity; in contrast to rounder, broader, and shorter quickly disintegrating filaments for higher conductivity. The large acceleration values (4060 m/s2 and 520 m/s2 for 2 μS/cm and 400 μS/cm, respectively) indicate that the process is mainly governed by the electrostatic force. In addition, with increasing conductivity, the breakdown voltage for corona-to-spark transition was decreasing.

Nano-Hierarchical Hollow Manganese Oxide Anode Material with High Performance for Lithium-Ion Battery

Lithium-ion batteries (LIBs) are expected to continue playing important roles in energy storage for mobile communication and electric vehicle (EV) and renewable energy applications in the foreseeable future. Graphite as a commercial anode material for LIB possesses the advantages of high coulombic efficiency and good cycle stability. However, its theoretical capacity is only 372mAh/g, and this limits the total capacity of the full battery. The demand for higher energy capacity of the energy storage cell has been driving the development of alternative anode materials with higher capacities. Certain nanocrystalline metal oxides have been shown to be able to work as a reversible anode through heterogeneous conversion reaction.The high theoretical capacity and density give metal oxides the edge over graphite as high energy density anodes for LIB. Nevertheless, due to the high kinetic barrier of the conversion reaction at room temperature, metal oxide anodes typically exhibits large potential hysteresis between lithiation and de-lithiation cycles. The hysteresis reduces the operating voltage window as well as the energy efficiency of the LIB cell. Furthermore, the poor conductivity and large volume expansion arising from lithiation of the metal oxide particles are major shortcomings that may cause poor cycling stability. Compared with other conversion–type metal oxide anodes, manganese oxide (MnOx) shows smaller potential hysteresis and lower operation potential. In addition, MnOxhave the advantages of being environment friendly and abundant.In this work, we have prepared hierarchical hollow MnO2 by utilizing a SiO2-templating hydrothermal process. The results revealed that the novel hollow nanostructure MnO2 electrode had a specific charge capacity as large as 1364 mAh/g at 0.1 C-rate, and it unprecedentedly demonstrates high rate performance, retaining 878 mAh/g at 2 C-rate and good cycle stability.

An electron source with a multiarc plasma emitter for obtaining submillisecond pulsed megawatt beams

An electron source with a plasma emitter based on an arc-discharge system with six cathodes and a common cylindrical hollow anode is described. Upon synchronous initiation of vacuum-arc discharges, the space of the hollow anode is filled by dense low-temperature plasma, the emission boundary of which is stabilized by a fine-structure metal grid with a 150-cm2 area. The arc-current amplitude for each cathode amounts to 100–300 A. Under the action of a constant accelerating voltage applied between the plasma emitter and grounded accelerating electrode combined with the drift tube, electrons are extracted from plasma and accelerated. At a working pressure of 0.04 Pa, an electron beam with a maximum current amplitude of 1 kA has been obtained at an initial accelerating voltage of 80 kV and pulse duration (FWHM) of 100 μs, which has been transported in a longitudinal magnetic field of 0.035 T over a distance of 80 cm.

Experimental Study of Electron Gun With Hollow-Anode Vacuum-Arc-Plasma Cathode

This paper presents experimental results of a novel electron gun with a vacuum-arc-plasma cathode used in microwave tube devices. The plasma cathode is based on a vacuum-arc discharge with a novel hollow anode and a Pierce-type electrostatic focusing system. The experimental result shows that this type of electron gun can be used to generate an electron beam of several amperes with a long pulsewidth. Based on the test results, a longer pulsewidth can theoretically be obtained by adjusting the parameters of the vacuum-arc discharge and ignoring heat dissipation and electrode erosion.

Controllable synthesis of hollow Si anode for long-cycle-life lithium-ion batteries.

A versatile and surfactant-free method is developed to synthesize hollow Si materials using carbonates as templates without the use of hazardous hydrofluoric acid. The morphology of Si is controllable from hollow cubes, spheres, and tubes, to flowers and other shapes. Such hollow Si materials as anodes of lithium-ion batteries show excellent cyclic performance, which is promising for practical applications.

A dc plasma source for plasma–material interaction experiments

A new device has been constructed for the investigation of interactions between engineered materials and a plasma in regimes relevant to electric propulsion and pulsed power devices. A linear plasma source, consisting of a hollow cathode, cylindrical anode, and axial magnetic field, delivers a 3 cm diameter beam to a biased target 70 cm away. The ion energy impacting the surface is controlled by biasing the sample from 0 to 500 V below the local plasma potential. This paper discusses the major aspects of the plasma source design and presents measurements of the plasma parameters achieved to date on argon and xenon. Experiments show that splitting the gas injection between the hollow cathode and the anode region provides control of the discharge voltage to minimize cathode sputtering while providing ion fluxes to the target in excess of 1021 m−2 s−1. Sputtering rate measurements on a non-textured molybdenum sample show close agreement with those established in the literature.

Controlled Syntheses of Various Palladium Alloy Nanoparticles Dispersed in Single-Walled Carbon Nanohorns by One-Step Formation Using an Arc Discharge Method

The present study examined the formation of single-walled carbon nanohorns (SWCNHs) dispersed with nanoparticles of a Pd alloy that is composed of one of nine elements—Au, Pt, Cu, Fe, Ni, Ti, Mo, W, and Nb—by a modified gas-injected arc-in-water (GI-AIW) method incorporating a hollow graphite anode into which wires of Pd and an alloying component were inserted to generate arc discharge. The following requirement to realize the formation of Pd-alloy nanoparticles dispersed in SWCNHs was recognized: the boiling points of the alloying component must be below the 5000 K arc plasma temperature. When this requirement is satisfied, the boiling point of this component could be used as a threshold to judge whether Pd should be enriched or diluted in the products formed by the arc discharge process. Particle size analysis revealed that nanoparticles of Pd alloy containing Au show significantly high dispersion. In contrast, alloys with Cu produce relatively large alloy nanoparticles. The tendency of the average size...

Effect of nickel impregnated hollow fiber anode for micro tubular solid oxide fuel cells

A micro tubular solid oxide fuel cells (MT-SOFCs) with a cell configuration of Ni impregnated Ni–Gd0.1Ce0.9O1.95 (GDC)/GDC/La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)–GDC has been prepared by the phase inversion and impregnation technique. A special asymmetrical structure consisting of a sponge-like layer and a finger-like porous layer for hollow fiber anode is obtained by the phase inversion. Fine Ni specie particles are then coated on the surface of anode using impregnation method. The enhancement in electronic conductivity of anode by Ni modification is beneficial to current collection of MT-SOFCs. Meanwhile, the catalytic activity of anode is also improved due to the introduction of Ni nano-particles. Thus, the Ni modified MT-SOFCs exhibit high power densities, such as 0.69 W cm−2 at 600 °C. The encouraging results demonstrate that the Ni impregnation is an effective way to improve anode microstructure of MT-SOFCs.

Design and initial results from a kilojoule level dense plasma focus with hollow anode and cylindrically symmetric gas puff

We have designed and built a Dense Plasma Focus (DPF) Z-pinch device using a kJ-level capacitor bank and a hollow anode, and fueled by a cylindrically symmetric gas puff. Using this device, we have measured peak deuteron beam energies of up to 400 keV at 0.8 kJ capacitor bank energy and pinch lengths of ∼6 mm, indicating accelerating fields greater than 50 MV/m. Neutron yields of on the order of 10(7) per shot were measured during deuterium operation. The cylindrical gas puff system permitted simultaneous operation of DPF with a radiofrequency quadrupole accelerator for beam-into-plasma experiments. This paper describes the machine design, the diagnostic systems, and our first results.

STRESS-MODULATED DRIVING FORCE FOR LITHIATION REACTION IN HOLLOW NANO-SPHERICAL ANODES

ABSTRACTRecent experimental evidence on nano-particle and nano-wire silicon anodes showed an initial rapid velocity of reaction front at the initial stage of lithiation, followed by an apparent slowing or even halting of the reaction front propagation. This intriguing phenomenon is attributed to the lithiation-induced mechanical stresses across the reaction front which is believed to play an important role in the kinetics of reaction at the front. Here, through theoretical formulation, we presented a comprehensive study on lithiation-induced stress field and its contribution to the driving force of lithiation in hollow spherical anodes with different boundary conditions at the inner surface of the particle. Our results reveal that hollow spherical silicon anodes can be lithiated more easily than solid spherical silicon particles and thus may serve as an optimal design of high performance anodes of lithium-ion battery.