High Anode Voltage Research Articles

Electrochemical Preparation of In-Silicon Hierarchical Networks of Regular Out-Of-Plane Macropores Interconnected by Secondary In-Plane Pores Through Controlled Inhibition of Breakdown Effects

In-silicon hierarchical networks of ordered out-of-plane macropores interconnected by high-density secondary in-plane pores are prepared by controlled electrochemical etching of n-type silicon in HF:H2O2 electrolyte through the synergistic use of back-side illumination, avalanche breakdown anodization voltage, and high-oxidizing-power chemical. Preparation of the hierarchical networks of pores is enabled by controlled inhibition of breakdown effects at high anodization voltages (in the breakdown region) through back-side illumination of the silicon electrode. Inhibition of breakdown effects in pre-patterned silicon electrodes etched under galvanostatic condition at high anodization voltages is used to simultaneously control formation of out-of-plane macropores by regulating the photogenerated etching current density flowing at the pore tips and enable in-plane branching of out-of-plane pores by increasing leakage current at the lateral pore surface through high voltage effects. Further, high-oxidizing-power chemical, namely H2O2, is used to increase density, length, and diameter of branching and, in turn, enable interconnection of out-of-plane macropores with in-plane secondary pores.

Understanding interfacial chemistry and stability for performance improvement and fade of high-energy Li-ion battery of LiNi0.5Co0.2Mn0.3O2//silicon-graphite

Understanding the chemical processes that occur at the electrode/electrolyte interface in a battery is crucial, as the interactions between anode/cathode and electrolyte and between cathode and anode of a full-cell determine the final battery performance. We have investigated the correlation among cycling performance, interfacial reaction behavior and the solid electrolyte interphase (SEI) stability of a LiNi0.5Co0.2Mn0.3O2//Si-graphite full-cell under an aggressive test condition between 3.0 and 4.55 V using fluoroethylene carbonate (FEC)-based electrolyte, and blended additives of methyl (2,2,2-trifluoroethyl)carbonate (FEMC) and vinylene carbonate (VC). Through the formation of a stable SEI at both high-voltage cathode and anode, metal dissolution from the cathode is inhibited and full-cell achieves enhanced cycling performance. Interfacially stabilized full-cell delivers a high energy of 622 Wh per kg of active material and improved capacity retention, whereas the cell in conventional electrolyte shows a rapid performance fade.

Fabrication and Characterization of Titania (TiO2) Nanotube Dye-Sensitized Solar Cells by Anodization Method

Titania (TiO2) nanotubes were synthesized on Ti metal sheets by anodization method. The anodization condition was the variation of the anodization voltage. The nanotubes were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-vis Spectrometer. The nanotubes can be used to make working electrodes for dye-sensitized solar cells. The pore diameter of TiO2 nanotube increases with the higher anodization voltage. The TiO2 nanotube diameters prepared at applied voltages of 40, 50, 60 and 70 V were approximately 200, 170, 140 and 100 nm, respectively. Furthermore, the dye-sensitized solar cells device based on the N719 dye and electrolytes shows the photovoltaic performance at different voltages of 40, 50, 60 and 70 V were 4.21%, 4.77%, 6.10% and 6.89%, respectively, under irradiation of 60 mW/cm2. The energy conversion efficiency of the dye-sensitized solar cells increased with increasing pore diameter of titania nanotubes.

X-ray source using carbon-nanotube field emitter with side-gate electrode

A carbon-nanotube (CNT) field emitter with side-gate electrodes, which are placed in-plane with the CNT emitters, is one of the most promising structures to realize a large-area X-ray charge neutralizer with a cost-effective and easy process. An X-ray source using the screen-printed CNT field emitter with side-gate electrodes is developed. The field-emission and X-ray properties are evaluated with anode voltages of 5 and 10 kV. It is shown that the emission current can be controlled by the side-gate voltage even with such high anode voltages as 5 and 10 kV. It is reported that the highest anode current is approximately 1 µA, which is high enough for an X-ray charge neutralizer. The X-ray radiation is successfully controlled by the pulsed side-gate voltage with subsecond length.

Facile fabrication of superhydrophilic/superhydrophobic surface on titanium substrate by single-step anodization and fluorination

A facile and scalable technique for preparation of superhydrophilic/superhydrophobic titanium (Ti) surface by single-step anodization and fluorination is presented in this paper. The Ti substrates were anodized to produce micro-nano hierarchical structure which is essential for superhydrophilic surface. The water contact angles (WCAs) of 5μl water droplets on the anodized Ti surfaces were measured as low as 0°. Capillary rise measurement was used to evaluate the superhydrophilicity on Ti surfaces anodized at different conditions. Results show that higher anodization voltage can yield stronger superhydrophilicity on Ti surface, but the influence of electrolyte temperature on the superhydrophilicity has a close correlation with the anodization voltages. At 20V and 40V anodization voltages, the increase of electrolyte temperature can improve the surface superhydrophilicity, but this trend will be reversed when the voltages rise to 60V and 80V. Superhydrophobic surfaces were further obtained from fluoroalkylsilane (FAS) modification on the anodized Ti substrates. It was observed that appropriate anodization voltages and electrolyte temperatures can balance the growth and dissolution of the micro-nano hierarchical surface structure, thereby obtaining the desired superhydrophobic Ti surface. The WCA, rolling angle and contact angle hysteresis of water droplets on the best superhydrophobic Ti surface were respectively recorded as 160°, 2° and 1.7° in this work. Furthermore, the superhydrophilic and superhydrophobic Ti surfaces fabricated in this research also show satisfactory stability in acidic, neutral and alkaline aqueous solutions as well as ambient conditions.

Control of persistent photoconductivity in nanostructured InP through morphology design

In this paper, we show that long-duration-photoconductivity decay (LDPCD) and persistent photoconductivity (PPC) in porous InP structures fabricated by anodic etching of bulk substrates can be controlled through the modification of the sample morphology. Particularly, the PPC inherent at low temperatures to porous InP layers with the thickness of skeleton walls comparable with pore diameters is quenched in structures consisting of ultrathin walls produced at high anodization voltages. The relaxation of photoconductivity in bulk InP substrates, porous layers, and utrathin membranes is investigated as a function of temperature and excitation power density. The obtained results suggest that PPC in porous InP layers is due to porosity induced potential barriers which hinder the recombination of photoexcited carriers, while the photoconductivity relaxation processes in ultrathin membranes are governed by surface states.

Relaxation Oscillations in Floating Liquid Bridges

A floating liquid bridge configuration that operates in a pulsed relaxation mode in which charge (cations) and fluid injection alternatively assume forward and opposite directions in the bridge structure is reported. Cations formed at the high voltage anode are surrounded by clusters of dimethylsulphoxide (DMSO) molecules that migrate to the cathode resulting in forward fluid transport with a period of ~200 s until an equilibrium point is attained. The fluid motion then assumes the opposite direction of the current for~60 s. Charged clusters travel to the bridge surface modifying its structural properties forming a plastic layer with an ~85 KPa stiffness.

A new lithium-ion battery: CuO nanorod array anode versus spinel LiNi0.5Mn1.5O4 cathode

Lithium-ion batteries with advanced performances are required to meet the needs for next generation power batteries. In this work, a new lithium-ion battery has been successfully assembled based on high energy CuO nanorod array anode and high voltage spinel LiNi0.5Mn1.5O4 cathode. Electrochemical tests of the CuO nanorod array grown on copper substrate demonstrate that the CuO/Li half cell can deliver discharge capacities of 787 and 560 mAh g−1 at 0.1 and 10C rates. Different from the traditional prelithiation of transition metal oxides anodes, a CuO-limited full cell has been assembled directly by adjusting the positive/negative capacity ratio of 1.2:1, which could deliver a discharge capacity of 660 mAh g−1 with estimated energy density of about 217 Wh kg−1 at 0.1C rate. The CuO/LiNi0.5Mn1.5O4 full cell exhibits good cycle stability (with capacity retention of 84% at 0.5C over 100 cycles) and superior rate capability (about 240 mAh g−1 at a high rate of 10C), which are mainly resulted from CuO arrays directly constructed on copper substrate and the hierarchical structure of LiNi0.5Mn1.5O4 materials. The unique battery may cast new light upon constructing low cost, high energy, high rate capability and high safety full cells.

The production and evolution of atomic oxygen in the afterglow of streamer discharge in atmospheric pressure fuel/air mixtures

In this work two-photon absorption laser-induced fluorescence was used to measure oxygen atom (O) concentrations in streamer discharge afterglow in a variety of fuel/air mixtures in order to account for the O reaction pathways in transient plasma ignition. It is demonstrated that O atoms are generated in high concentration (∼5 × 1017 cm−3) directly below the high-voltage anode in a point-to-plane geometry. The corresponding lifetimes in air were on the order of hundreds of microseconds. Fuel chemistry provides consumption pathways via chain branching reactions even without sustained combustion, and the corresponding O-atom lifetimes were much shorter than in air and dependent on the fuel concentration. At the richest conditions, corresponding to a fuel–air equivalence ratio of 2.4, O lifetimes were on the order a few microseconds or less. These experimental results are compared to modelling estimates in order to better understand the role of atomic oxygen in the chemical processes leading to ignition.

Stability of deflected-beam metal–insulator–metal tunneling cathodes under high acceleration voltage

Metal–insulator–metal (MIM) tunneling cathodes have advantageous features, such as areal electron beams and robustness to surface contamination. Therefore, they are suitable for field-emission displays. This paper reports the long-term stability of MIM tunneling cathodes in display panels operating under a high acceleration voltage (anode voltage). A preliminary life test was carried out using conventional display panels, which consisted of a phosphor-coated anode plate and a cathode plate having matrix-arrayed cathodes. The life test indicated that the pace at which cathodes degrade increases significantly when the acceleration voltage exceeds a few kilovolts. This high-voltage (HV)-induced degradation is presumably attributed to cathodes being bombarded by positive ions originating from residual gases. To suppress HV-induced degradation, the authors propose the concept of a deflected-beam cathode, in which electron beams are deflected so that the recoiling ions fail to hit the cathode. This concept was implemented by introducing deflector electrodes in the cathode plate, thereby forming an electron lens in each pixel. As 6-μm high scan lines were used as the deflector electrodes in this design, the deflected-beam cathodes could be fabricated only by modifying the pattern of the scan lines. The authors also present a simulation-based design procedure using an emitter-landing diagram, which facilitates analysis of the margins for the deflected-beam cathodes. The deflected-beam cathodes thus designed were incorporated into 3.8 cm-diagonal test panels to confirm the validity of the concept. The degree of beam deflection that was observed was in excellent agreement with the results obtained from simulation. A life test extending over a 20 000-h period demonstrated that the HV-induced degradation was suppressed with the deflected-beam MIM cathodes.

Controlled Growth and Application in Lithium and Sodium Batteries of High-Aspect-Ratio, Self-Organized Titania Nanotubes

Searching for optimized electrode materials in alkali ion batteries we have prepared a large number of titania nanotubes (nt-TiO2) electrodes by using different voltages in the 42–100 V range and Ti-anodization times and studied their behavior in test batteries. As a result of the high current densities observed in the transient curves for a fixed electrolyte composition, high anodization voltages allow the rapid growth of self-organized and amorphous nanotube arrays with up to 200 μm in length. The growth of nt-TiO2 follows the parabolic rate law (L2 = kt). Titania nanotubes with different lengths were used as electrode materials in lithium and sodium test cells. In lithium cells, the areal capacities depend on the nanotube length independently of the anodization voltage used to obtain a particular length. The very high areal capacities that are observed in lithium (around 2–4 mAh/cm2) and sodium (ca. 1 mAh/cm2) cells are attributed to the high length of the nanotubes. However, the longer titania nanotubes exhibit lower gravimetric capacity values (mAh/g) due to the longer ion diffusion path. The capacity to react with sodium is lower than with lithium, probably due to the poor conductivity of nt-NaxTiO2.

An Investigation of Performance Characteristics of High-Voltage Trigatron

A new-style high-voltage switch named trigatron with great advantage, such as simple structure and applying circuits, wide operational temperature and voltage range, short delay time, long operational life is introduced in this paper. Firstly the four operational modes which trigatrons are suitable for pulse power devices are presented. Then through experimental study and theoretical analysis, the effect factors of turn-on time of trigatrons are summed up, including anode voltage, triggering voltage and triggering-wire’s length, finally giving a conclusion that the higher anode voltage and triggering pulse voltage are, the more steady and shorter turn-on time is.

Growth and Morphology of Highly Ordered TiO2 Nanotube Arrays via Electrochemical Anodization

In this paper, highly ordered titania nanotube arrays (TNTs) were prepared by anodization of Ti foils in ethylene glycol electrolyte. The morphology of the TNTs under different voltage and duration has been studied by Scanning Electron Microscopy (SEM). The constituent elements of the TNTs are mapped by energy dispersive X-ray (EDX). Immobilized TNTs were formed in the voltage range of 20~80V. High anodic voltage (>80V) induced detachable nanotube arrays on Ti foils. The nanotube diameter increases with increasing the applied voltage and without dependence on the anodic duration. The concentration of element oxygen is rich at top and bottom sections of the nanotube arrays. Meanwhile, the oxygen concentration on top surface decreases with increasing the anodization voltage.

Gradient TiO2 Nanotube Arrays via Asymmetric Anodization

Gradient self-organized TiO2 nanotube arrays with the tube diameters and length gradually changing along the sample plane are conveniently fabricated. The fabrication method is based on asymmetric anodization with the point cathode placed close to the edge of the titanium foil anode. Mechanism study reveals that the drastic variance in the voltage drop over the tube bottom at different locations along the film is responsible for the formation of the gradient morphology. Experimentally, moderate electrolyte conductivities and sufficiently high anodization voltages are necessary to enable the desired gradient TiO2 nanotube arrays. Moreover, the structural features of the fabricated gradient TiO2 nanotube arrays can be further adjusted by controlling the imperfection level of the titanium substrate.

Improvement of the performance of a field‐emission device with a metal mask

AbstractIn a field‐emission device, the background noise of the anode current is a little large due to the high anode voltage. Apart from this, the electron beam spreads because of the large gap between the cathode and the anode. To improve the performance of a field‐emission device, a metal mask is introduced between the gate and the anode. Because the metal mask shields the electric field caused by the anode, the background noise of the anode current has been decreased about 90%. With a proper voltage applied on the metal mask, a convergence electric field is generated around the holes of the metal mask, so the focus performance of the electron beam is also improved. The width of the scanning line decreases from 3.1 mm to 0.9 mm after the metal mask is mounted. Because the metal mask can be fabricated in a large volume with low cost, the structure proposed in this paper has a promising application in the field‐emission display devices. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Low-voltage driven carbon nanotube field emission lamp

CNTs were grown on a silicon substrate using the RAP process and PECVD system. The resulting CNT emitters showed the excellent field emission characteristics. For low-voltage driving field emitter fabrication, the CNTs were connected to the drain part of an external MOSFET. A low gate voltage of the MOSFET can control the field emission current of CNTs, instead of a high anode voltage. The emission current of CNTs controlled by the MOSFET was very stable in terms of both the current switching and the current stability of 100 h.

Power Quality Investigation of Back-to-Back Harmonic Filters for a High-Voltage Anode Foil Manufacturing Facility

The problem, as described by this high-voltage anode foil manufacturing facility, has included loss of the harmonic filter banks during utility power disturbances. During such disturbances, one or more formation machine(s) trip and rectifier(s) fault, both of which are critical to the continuous operation of the process. One recent disturbance resulted in significant failure of components in both filter banks. A power quality investigation commenced to determine the cause of the filter bank failure. This paper describes the results of the analytical methods employed. Field harmonic measurements determined the presence of voltage and current distortion and established an appropriate model for harmonic analysis of various likely system conditions. Harmonic analysis explained the tuning of the existing filter banks and changes to tuning that have occurred since installation several years ago, as well as determined the harmonic loading on each stage of the filters. Transient simulations identified existing problems and areas of concern, particularly in regard to transient overvoltages that resulted when switching either of the filter banks. Recommendations included alternatives to avoid possible failures in the future, most significantly the redesign of one of the harmonic filters and the application of surge protection.

Novel tapered macrogate structure for carbon nanotube based field emission display

The tapered macrogate (TMG) structure is proposed to overcome the difficulties in carbon nanotube (CNT) based field emission display (FED) with high-voltage phosphors used in cathode ray tube screens. In order to achieve an ideal triode operation for field emission devices, the TMG was designed to have a very thick gate insulator with the inclined gate holes compared with the CNT emitters. The inclined gate holes with a narrower outlet than the bottom of the hole were shown to protect the CNT emitters from the anode field perfectly, enabling the authors to apply a high anode voltage over 10 kV needed for high-voltage FED. Also, the TMG structure had additional useful functions such as an electron-beam self-focusing and high durability against electrical damage. The authors successfully fabricated and demonstrated a 5 in. active-matrix CNT-FED panel with the TMG, showing color moving images with a low addressing voltage of about 15 V using amorphous silicon thin-film transistor as a switching device.

High-Aspect Ratio Nano-Noodles of Alumina and Titania

We report the formation of high-aspect ratio rod-like structures or 'nano-noodles' of alumina or titania. Such structures are formed either by rapid anodization of aluminum/titanium foil or by long-term post-anodization treatment of porous templates. Specifically, the nano-noodle structures form during anodization in highly acidic electrolytes and/or at high anodization voltages, or when porous templates are etched for long periods of time in an acid. Growth mechanism for such structures is also proposed.

Effect of trace Sn on corrosion behaviors of high voltage anode aluminum foil

The cube texture and the surface corrosion structure of aluminum anode foil for high voltage electrolytic capacitor containing trace Sn were investigated based on quantitative texture analysis and microstructure observation under SEM. High volume fraction of cube texture over 95% and obviously higher specific capacity are obtained in the foils with less than 0.002% Sn. It is indicated that the corrosion behavior of trace Sn on aluminum surface is similar with that of Pb. Higher content of Sn over 0.002% reduces the cube texture component and therefore the specific capacity. Sn, as an eco-friendly microelement, can be applied to replace Pb in improving the homogenous pitting behaviors of high voltage aluminum foils.