Cylindrical Cathode Research Articles

Field emission from cylindrical graphene cathodes prepared by chemical vapor deposition and cold rolling

We report field emission (FE) properties of cold cathodes made by a scalable chemical vapor deposition synthesis of three-dimensional graphene (3DG) from a cast catalyst followed by cold rolling. This process leads to an increase in mechanical strength and electrical conductivity of the tested material. For a given distance between the tip of the cathode and the anode, it is found that the FE current from the edge of a single sheet of cold-rolled 3DG-based cathode can be increased by over one order of magnitude when rolling the 3DG sheet in the shape of a cylinder with several turns. A FE current in the order of 4.5 mA was measured from a 3 mm diameter cold-rolled 3DG cylinder with six turns at a bias of 2400 V for a separation of 0.5 mm between the tip of the cylindrical cathode and the anode. The FE data of all cold-rolled 3DG-based cathodes are well fitted by the expression proposed by Abbot, Henderson, Forbes, and Popov [Filippov et al., R. Soc. Open Sci. 9, 220748 (2022)], Im=CVmκexp(−B/Vm), where Im is the FE current, Vm is the bias applied between the cathode and anode, and B and C are fitting parameters. It is found that κ=1 and 3/2 for FE from the surface and edge of the cold-rolled based cathodes, respectively.

Effect of multi-cusp magnetic fields to generate a high-density hydrogen plasma inside a low pressure H2 cylindrical hollow cathode discharge

Based on probe measurements, the plasma density in a low pressure H2 radio-frequency (RF) magnetized cylindrical hollow-cathode capacitively coupled plasma (CCP) is demonstrated to be enhanced by applying a multi-cusp magnetic field (MCMF). CCPs can be used for fabricating functional thin-films, but are currently limited by low plasma densities of less than or about 1016 m−3. It is found that a maximum plasma density of 2.51, 2.88, and 3.14 × 1016 m−3 is obtained at 3, 4 and 5 Pa, respectively. The employed MCMF arrangement contributes to achieving superior plasma uniformity, both in axial and radial direction, at an RF power of 50 W.

Two-temperature modeling of lamellar cathode arc

A three-dimensional, two-temperature (2T) model of a lamellar cathode arc is constructed, drawing upon the conservation equations for mass, momentum, electron energy, and heavy particle energy, in addition to Maxwell’s equations. The model aims to elucidate how the physical properties of electrons and heavy particles affect heat transfer and fluid flow in a lamellar cathode arc. This is achieved by solving and comparing the fields of electron temperature, heavy particle temperature, fluid flow, current density, and Lorentz force distribution under varying welding currents. The results show that the guiding effect of the lamellar cathode on current density, the inertial drag effect of moving arc, and the attraction effect of Lorentz force at the lamellar cathode tip primarily govern the distribution of the arc’s physical fields. The guiding effect localizes the current density to the front end of the lamellar cathode, particularly where the discharge gap is minimal. Both the inertial drag effect and the attraction effect of Lorentz force direct arc flow toward its periphery. Under the influence of the aforementioned factors, the physical fields of the lamellar cathode arc undergo expansion and shift counter to the arc’s direction of motion. A reduction in welding current substantially weakens the guiding effect, causing the arc’s physical fields to deviate further in the direction opposite to the arc motion. In comparison with a cylindrical cathode arc, the physical fields of the lamellar cathode arc are markedly expanded, leading to a reduction in current density, electron temperature, heavy particle temperature, cathode jet flow velocity, and Lorentz force.

Perspectives of a single-anode cylindrical chamber operating in ionization mode and high gas pressure

As part of the R2D2 (Rare Decays with Radial Detector) R &D, the use of a gas detector with a spherical or cylindrical cathode, equipped with a single anode and operating at high pressure, was studied for the search of rare phenomena such as neutrinoless double-beta decay. The presented measurements were obtained with a cylindrical detector, covering gas pressures ranging from 1 to 10 bar in argon and 1 to 6 bar in xenon, using both a point-like source of 210\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{210} $$\\end{document}Po (5.3 MeV α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}) and a diffuse source of 222\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{222}$$\\end{document}Rn (5.5 MeV α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}). Analysis and interpretation of the data were developed using the anodic current waveform. Similar detection performances were achieved with both gases, and comparable energy resolutions were measured with both sources. As long as the purity of the gas was sufficient, no significant degradation of the measured energy was observed by increasing the pressure. At the highest operating pressure, an energy resolution better than 1.5% full-width at half-maximum (FWHM) was obtained for both gaseous media, although optimal noise conditions were not reached.

Cylindrical hot cathode ionisation gauge – Construction and testing

Hot cathode ionisation gauges are indispensable in measuring high and ultra-high vacuum. In the present work the construction details and the metrological evaluation of a novel gauge design — the cylindrical ionisation gauge is presented. With the aim of enhancing accuracy and stability both in the short and long term, details of the mechanical assembling of electrodes and precautions to minimize leakage currents influencing ion current measurement are described. Performance evaluations demonstrate high short-term stability, with linearity error, reproducibility, and repeatability values consistently below 1 %, placing the gauge at the same level as the most stable ionisation gauges. Operating across a pressure range of at least 6 orders of magnitude, the gauge exhibits low linearity error from high to ultra-high vacuum ranges. Its capability to measure pressures below 10−9 mbar remains open and requires further investigation.

Design, construction, and performance of the GEM based radial time projection chamber for the BONuS12 experiment with CLAS12

A new radial time projection chamber based on Gas Electron Multiplier amplification layers was developed for the BONuS12 experiment in Hall B at Jefferson Lab. This device represents a significant evolutionary development over similar devices constructed for previous experiments, including cylindrical amplification layers constructed from single continuous GEM foils with less than 1% dead area. Particular attention had been paid to producing excellent geometric uniformity of all electrodes, including the very thin metalized polyester film of the cylindrical cathode. This manuscript describes the design, construction, and performance of this new detector.

Thermophysical model of a thermonic cathode with induction heating

A thermophysical model was built and the temperature field of a cylindrical thermionic cathode with induction heating was calculated, taking into account the initial and boundary conditions, based on the adoption of assumptions to simplify the mathematical model. During the induction heating of the cathode, a non-stationary heat conduction process is established, which is described by the differential equation of heat conduction with internal sources of Joule heat. The distribution of internal heat sources in the volume of the cathode is determined by the distribution of the ring induced current. The cylindrical design of the inductive thermionic cathode, due to spatial symmetry, allows to reduce the number of spatial variables, significantly simplify functional dependencies, and limit the algorithm for solving the problem. The problem was solved in the cylindrical coordinate system. The obtained approximate solutions were assessed for the correctness of the accepted simplifications when finding the distribution of the temperature field with a sufficient degree of accuracy. Despite the high thermal conductivity of the cathode material, when the cathode is inductively heated, there can be a significant temperature difference between its outer and inner surfaces. The article shows the permissible temperature difference on the surface of the cathode, which limits the choice of geometric dimensions of the cathode. The temperature difference on the surfaces of the induction thermionic cathode is most affected on the end (annular) surfaces of the cathode, so it is better to apply emitting coatings to the side surfaces of the cylindrical cathode, thus complicating the design of the cathode. The application of induction heating of the thermionic cathode allows to simplify the heating unit, increase the reliability and service life of powerful electronic devices. The obtained results are planned to be used in further research as test data for the analysis of more complex problems of numerical calculation of the thermal regimes of the cathode unit with heat shields and focusing elements of thermoelectron flows.

Revealing the mass transfer of proton donors for tailoring hydrogen evolution coupled with manganese electrodeposition

The implementation of a rotating cylindrical cathode for manganese deposition offers a novel perspective in comprehending the conjugated hydrogen evolution reaction within complex solution systems.

Experimental study on electrochemical machining of TC11 titanium alloy blades based on cylindrical array microstructure cathodes

Titanium alloys have a wide range of applications in aerospace, however, this material is very sensitive to changes in the flow field during electrochemical machining (ECM) and suffers from frequent short-circuiting and poor surface quality. Studies have shown that optimization and improvement of the cathode structure often improve the processing properties of the material. To process titanium alloy under a steady state, the laser processing system was used to prepare cylindrical array microstructure on the end surface of cathode. The comparison between the original and improved cathode was conducted in ECM experiments. The experimental results showed that serious flow marks existed on the original cathode processing surface. Within the range of processable voltage, short circuits occurred at the processing heights of 1.823 mm and 1.655 mm. The improved cathode can process a bright finish surface without flow marks and there were no short circuits. The influence of two microstructure arrangements on the blade surface quality was also investigated. Compared to inline cylindrical array (ICA) cathode. The processing gap equilibrium flow rate of the staggered cylindrical array (SCA) cathode is about 0.3 L/min higher. The average surface roughness of the blade hub was reduced from 1.632 µm to 0.574 µm. Additionally, there are multiple layers of electrolysis products adhering to the non-machined surface and the machined sidewall of the blade. The oxygen content of the outer layer is higher than that of the inner layer, and the oxygen content of the non-machined surface is significantly higher than that of the machined sidewall. The microstructure cathode designed in this paper realizes the stable processing of titanium alloy in passivation electrolyte.

Application of solar photo-electro-Fenton technology to petroleum refinery wastewater degradation: Optimization of operational parameters

Industrial and agricultural advances have led to global issues such as contamination of water sources and lack of access to clean water. Wastewater from petroleum refineries must be subjected to treatment as it poses a significant environmental threat. The present research aimed to reduce the level of chemical oxygen demand (COD) of an effluent from Bijee petroleum refinery plant, Iraq, using solar photo-electro-Fenton (SPEF) process operated in a batch recycle model. The electrochemical reactor used in the present research was of a tubular design with an anode composed of porous graphite rod and a concentric cylindrical cathode made of the same material.The impacts of operating parameters such as current density (10–50 mA/cm2), Fe2+ concentration (0.2–0.8 mM), NaCl addition (0–1 g/L), and time (30–90 min) on the COD removal efficiency were explored based on the response surface methodology (RSM). Results showed that the impact of Fe2+ concentration was most prominent, with an effective contribution of 47.7%, followed by current density, with a contribution of 18.26%, and the addition of NaCl, with a contribution of 11.20%. COD removal was found to increase with an increase in current density, Fe2+ concentration, NaCl addition, and time, respectively, while energy consumption was found to increase significantly with an increase in current density and a decrease in Fe2+ concentration, respectively. The optimum conditions were observed to be an initial pH of 3, current density of 10 mA/cm2, Fe2+ concentration of 0.8 mM, NaCl addition of 0.747 g/L, and a duration of 87 min, upon which 93.20% COD removal efficiency was achieved, with an energy consumption of 15.97 kWh/kg COD.

Development of Manganese-Coated Graphite Electrode in a Dual-Chambered Fuel Cell for Selenite Removal and Bio-Electricity Generation from Wastewater Effluent by Bacillus cereus

A manganese oxide-coated cylindrical graphite cathode with a zinc anode was developed to treat wastewater containing selenite in a dual-chambered microbial fuel cell. COD and selenite removal in the anodic chamber by Bacillus cereus with energy generation were evaluated in batch mode. A manganese dioxide-coated graphite cathode was tested for its surface morphology and chemical composition using scanning electron microscopy and dispersive energy analysis of X-rays. Compared to the non-coated graphite electrode, up to 69% enhancement was observed in the manganese dioxide-coated electrode voltage generation with 150 ppm selenite concentration. The fuel cell achieved a maximum power density of 1.29 W/m2 with 91% selenite reduction and up to 74% COD (initial COD of 120 mg/L) removal for an initial selenite concentration from 100 to 150 ppm. The current study demonstrated the possibility of a modified cathode in enhancing energy generation and the use of microbial fuel cell technology to treat wastewater containing selenite.

Numerical Study on the Characteristics of Cylindrical Virtual Cathode Reflex Triode Array

The bremsstrahlung cylindrical virtual cathode reflex triode (CVCRT) array is a new type of pulsed warm X-rays load. In this article, we established the CVCRT particle model and simulated and analyzed the working process and the influence of structural parameters on impedance. The results show that the impedance of the CVCRT depends on the structure of electrode and the thickness of anode conversion target. The theoretical impedance calibration relation was given, and the impedance simulation results of particle simulation agree well with the theoretical solution. Based on the Monte Carlo (MC) code, the radiation model of the CVCRT was established, and the influence rule of anode conversion target on X-ray parameters was studied. Results show that the anode thickness is the main factor affecting X-ray intensity. Under the voltage of 300 kV, the optimum thickness of the anode is about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10~\mu \text{m}$ </tex-math></inline-formula> . The influence of array arrangement on the spatial distribution of radiation field was calculated. The CVCRT array can superpose the X-rays in the effective radiation region and improve the efficiency of X-ray utilization, and the intensity of X-rays is about 1.9 times higher than that of the cylindrical reflex triode (CRT) under the identical driving conditions.

Characterising operational performance and oxygen crossover of the low-cost cylindrical cathode in microbial fuel cells

The cylindrical cathode has been used in microbial fuel cells (MFC) to achieve a large cathode area and high operational performance. However, the high material cost of cylindrical cathodes limits their practical application. To overcome this, a low-cost cylindrical cathode was successfully developed by coating activated carbon-based catalysts uniformly on the surface of cylindrical stainless steel mesh. The MFCs with the low-cost cylindrical cathodes could obtain a large surface area (up to 509 m2/m3), high power density (81.4 W/m3) and fast organic matter removal rate (−0.32 h−1). However, long-term operation showed that a cathode area larger than 104 m2/m3 could induce excessive oxygen crossover and substantially reduce the power stability of MFC. A numerical study showed that the oxygen crossover was affected by cathode properties such as surface area, current and biofilm. Accordingly, potential controlling methods were proposed. This study will benefit the practical application of cylindrical cathodes.

Optimization of chemical oxygen demand removal from petroleum refinery wastewater by electrocoagulation using tubular electrochemical reactor with a novel design

In this study, removal of chemical oxygen demand (COD) from petroleum refinery effluent was investigated using a new tubular electrochemical reactor (TER) design which operated at a batch recycle model. The electrochemical reactor comprises of two concentric electrodes namely spiral aluminum rode anode and hollow cylindrical stainless steel cathode. Four parameters were investigated: current density, sodium chloride concentration (NaCl), pH, and flow rate on the COD removal efficiency, and optimized using response surface methodology. Results show that current density is the most influential parameter on removal percentage where increasing current density results in increasing the removal efficiency. Another effect of lowering flow rate resulted in high removal of COD due to the increased resistance time of effluent passing on the surface of the anode with the newly adopted design. Finding of laboratory work were obtained under optimal working conditions such as current density of 26 mA/cm2, pH of 7.9, NaCl concentration of 1.1 g/L, and flow rate of 2 L/min. These were resulting in a COD removal efficiency of 73.36% with specific energy consumption of 30.61 kWh/kg·COD. Operating cost of the present system was found to be $2.185 m3 which is considered low and acceptable. Experimental results prove that the new design of TER is more efficient than the traditional design that uses in electrocoagulation system to treat wastewater generated from petroleum refinery plants.

NiB-CrC Coatings Prepared by Magnetron Sputtering Using Composite Ceramic NiCr-BC Target Produced by Detonation Spray Coating.

A metal–ceramic composite target for magnetron sputtering was fabricated for the first time by a robotic complex for the detonation spraying of coatings equipped with a multi-chamber detonation accelerator. A mixture of metal and ceramic NiCr/B4C powders was sprayed onto the copper base of the cylindrical composite target cathode. The study of the structure of a metal–ceramic composite coating target using scanning electron microscopy showed that the coating material is dense without visible pores; the elemental composition is evenly distributed in the material. The study of the cathode sputtering area after deposition in the DC mode showed that there are uniform traces of annular erosion on the target surface. The obtained cathode target with an NiCr-70B4C coating was used to deposit the NiB-Cr7C3 coating on flat specimens of 65G steel using equipment for magnetron sputtering UNICOAT 200. The coating was applied in the Direct Current mode. A dense NiB-Cr7C3 coating with a thickness of 2 μm was obtained. The NiB-Cr7C3 coating has a quasi-amorphous structure. The microstructures and concentration of oxygen and carbon impurities throughout the entire thickness of the coating were investigated by means of transmission electron microscopy. The results of the study show that the coatings have a nanocrystalline multi-phase structure. The microhardness of the NiB-Cr7C3 coating reached 10 GPa, and the adhesion fracture load exceeded 16 N. The results will open up new prospects for the further elaboration of technology for obtaining original composite cathodes for magnetron sputtering using detonation spraying of coatings.

Modeling of Tubular Electrochemical Reactor with a Spiral Design of Anode for Treatment of Petroleum Refinery Wastewater

Petroleum effluent is often made up of a complex combination of metals and organic molecules. In the present work, modeling of a tubular electrochemical reactor (TER) with a novel design operated at batch recycle for petroleum refinery effluent treatment by anodic oxidation was investigated. The reactor is composed from a cylindrical stainless steel cathode and a spiral porous graphite anode at its center. The impact of flow rate on the COD reduction and mass transfer coefficient (k) was studied. Results showed that increasing flow rate led to higher removal efficiency of COD and higher mass transfer coefficient where COD removal of 70% and k with value of 6.283x10-4 cm/s were obtained at flow rate of 4l/min. A power low correlation was obtained between mass transfer coefficient(k) and Reynolds number (Re) with coefficient of determination (R2) equal to 0.994869.This relation can be described as k=1.906x10-6(Re) 0.545 with range of Re 10000≤Re≤ 40000 prevailing turbulent conditions.

Cadmium Removal Using Bio-Electrochemical Reactor with Packed Bed Rotating Cylindrical Cathode: A Kinetics Study

The kinetics of removing cadmium from aqueous solutions was studied using a bio-electrochemical reactor with a packed bed rotating cylindrical cathode. The effect of applied voltage, initial concentration of cadmium, cathode rotation speed, and pH on the reaction rate constant (k) was studied. The results showed that the cathodic deposition occurred under the control of mass transfer for all applied voltage values ​​used in this research. Accordingly, the relationship between logarithmic concentration gradient with time can be represented by a first-order kinetic rate equation. It was found that the rate constant (k) depends on the applied voltage, the initial cadmium concentration, the pH and the rotational speed of cathode. It was increased with increasing the applied voltage and its relationship with the applied voltage obeyed an exponential formula. The rate constant (k) was decreased with increasing the initial concentration of cadmium higher than 150ppm while at low concentrations it was increased. pH and rotational speed have different effects on the rate constant. Increasing the pH from 3 to 6 increases the rate constant while a slight decrease in the rate constant occurs at pH = 7. Increasing the rotation from 100 to 500 rpm increases the rate constant; however, the rate constant became approximately constant buoyed 300 rpm.

Double‐ejection micro‐cathode arc thruster applied to micro‐satellite

An innovative double-ejection micro-cathode arc thruster (ACd-µCAT), which consists of a cylindrical inner anode, a cylindrical outer cathode and two insulating sleeves (an inner insulating sleeve and an outer insulating sleeve), was proposed. The differences in electrical characteristics, plasma parameters and propulsion performance between the newly proposed ACd-µCAT and a traditional μCAT were examined. Study results showed that compared to the traditional μCAT structure, by using the ACd-µCAT, the peak value of produced thrust was increased 9.3 times, while the amplitude of the ion current and the ion-to-arc ratio were increased 5.4 and 5.9 times (from 1.2% to 7.1%), respectively. In addition, data from Langmuir probe experiments indicated that peak values of the directional propagation speed and density of plasma plume were increased 3.1 times and 4.2 times, respectively. Moreover, plasma plume directional ejection performance was also significantly improved. This study result will provide support for the development of a new-generation μCAT.

Boosting hydrogen production from fermentation effluent of biomass wastes in cylindrical single-chamber microbial electrolysis cell.

Microbial electrolysis cells (MECs) are considered as green technologies for H2 production with simultaneously wastewater treatment. Low H2 recovery and production rate are two key bottlenecks of MECs fed with real H2 fermentation effluent of biomass wastes. This work established a 1 L cylindrical single chamber MEC and enriched electroactive anodic biofilms from cow dung compost to overcome the bottlenecks. These MEC components (platinum-coated cylindrical titanium mesh cathode and cylindrical graphite felt anode) were arranged in a concentric configuration. A high H2 production rate of 6.26 ± 0.23 L L-1day-1 with H2 yield of 5.75 ± 0.16 L H2 L-1 fermentation effluent was achieved at 0.8V. The degradation of acetate and butyrate (main components of H2 fermentation effluent) could reach to 95.3 ± 2.1% and 78.4 ± 3.6%, respectively. The microbial community analysis for anode showed the abundance of Geobacter (22.6%), Syntrophomonas (8.7%), and Dysgonomonas (6.3%) which are responsible to complex substrate oxidation, electrical current generation, and H2 production. These results prove the feasibility of cylindrical single-chamber MEC for high H2 production rate and high acetate and butyrate removal from H2 fermentation effluent.

Electrowinning of gold from a dilute solution using hydrocyclone-type cell

ABSTRACT The redox reaction mechanism of gold−cyanide [Au(CN)2 −] during hydrocyclone electrowinning was investigated in this work by conducting Hull cell test, potentiodynamic polarization, and computational fluid dynamics (CFD) simulations. A leaching solution of waste printed circuit boards (WPCBs) was prepared as an electrolyte, and the effects of flow rate and applied voltage on the recovery of gold and destruction of cyanide through hydrocyclone electrowinning were investigated. A numerical simulation of the flow field in the cell was performed, and the results were visualized by conducting a finite element analysis in FLUENT. The CFD simulations and Hull cell test showed that the cylindrical cathode region had a flow velocity of ~11.05 m·s−1, which was higher than that at the center of the cylindrical part (<6.45 m·s−1). The optimum conditions for electrowinning were found to be as: an electrode distance of 4.9 mm and a current density of 73.78 mA·cm−2. The anodic polarization results showed that an Ir-based mixed metal oxide (MMO) anode could more efficiently oxidize the free cyanide because of its high current density than other types of anodes (Ir-based MMO: 299.3 mA·cm−2 > SS304: 3.5 mA·cm−2 > Pt-coated Ti: 1.3 mA·cm−2). Through the demonstrated hydrocyclone electrowinning test, the gold concentration could be decreased from 100 to 0.24 mg·L−1 within 12 h while destroying almost total amount of free cyanide in a day.