Anode Erosion Research Articles

Effect of contact materials on the transient characteristics of vacuum arc plasma and anode erosion

In this study, the mechanisms of the anode phenomena and anode erosion with various contact materials were investigated. Arc parameters were calculated, and the anode temperature was predicted with a transient self-consistent model. The simulation results predicted a constricted arc column and obvious anode phenomena in Cu–Cr alloy contacts than in W–Cu alloy contacts. This observation could be the reason for the concentrated anode erosion in Cu–Cr alloys. For the contacts made by pure tungsten (W) and W–Cu alloy, the anode temperature increased rapidly because of the low specific heat of W. However, the maximum energy flux from the arc column to the anode surface was lower than in other cases. The simulation results were compared with experimental results.

Experimental study on the life and performance of an improved DC arc plasma torch

A novel DC arc plasma torch is designed in this paper in order to reduce the electrode erosion, and a series of experiments are carried out to investigate how to improve the lifetime and performance of the nitrogen DC arc plasma torch. The analysis of voltage characteristics of the plasma torch indicates that the interelectrode insert can increase the average arc voltage and the sudden expansion structure can reduce the voltage fluctuation, which is helpful to improve the working stability to some extent. The spectrum characteristics at the plasma torch outlet and the cold flow simulations show that the dual shielding gas mainly act near the anode and can effectively cover the entire anode wall. Combining the shielding gas distribution with anode heat transfer processes in argon and nitrogen plasma torch, it is inferred that argon shielding gas plays an important role on reducing the anode heat transfer processes in nitrogen plasma torch, which can effectively suppress the anode erosion. The life testing experimental results find that there is no significant erosion of the cathode, anode, and interelectrode insert after cumulative working time exceeding 20 h. The maximum nitrogen plasma jet length can reach ∼35 mm with the outlet jet temperature of about 20 000 K at the current of 100 A and nitrogen gas flow rate of 10 slm. The maximum average specific enthalpy and thermal efficiency are respectively about 14 MJ kg−1 and 75% in the nitrogen plasma torch. Therefore, this newly designed DC arc plasma torch not only can suppress the electrode erosion but also has good working performance, which is expected to have excellent application prospects.

Study on deterioration of mechanical properties and voltage-strength theoretical model of CFRP/ conductive ECC composites under coupling effect of anode polarization, load and erosion environment

This study aims to systematically investigate the deterioration of tensile properties, voltage variation, and voltage-strength theoretical model of CFRP/ conductive ECC composites under coupling effect of anode polarization, load and erosion environment. The effects of testing parameters including conductive ECC mixture type, electric current density, polarization time, tensile stress value, sulfate soak time, and sulfate attack-wet and dry cycle time were synthetically investigated. The experimental results indicated that the voltage increases approximately linearly with the increase of degradation time in the voltage-deterioration time curves. The stress-strain curve can be divided into three stages: the stress-strain linear increase stage, the strain hardening characteristic stage, and the decline stage during failure. The conductive ECC mixture type, polarization time, current density, tensile stress value, sulfate soak time, and sulfate attack-wet and dry cycle time all have significant effects the deterioration of tensile strength and the voltage change ratio of CFRP/ conductive ECC composite. More importantly, an innovative voltage-strength theoretical model was proposed, which can predict the relationship between voltage and material deterioration strength. The theoretical model is in good agreement not only with the experimental results of this study, but also with the results of other studies. The model proposed can be used to predict deterioration degree of materials in real time, which has very important guiding significance for impressed current cathodic protection-structural strengthening technology (ICCP-SS) technology. This study is expected to promote a more comprehensive understanding of the deterioration of mechanical properties and voltage-strength theoretical model of CFRP/conductive ECC composites for ICCP-SS technology.

Формирование и исследование свойств покрытий из металлического стекла FeWCrMoBC на стали 35

Introduction. To obtain metallic glass coatings it is necessary to achieve high cooling rates of melt. FeWCrMoBC composition has high melt viscosity and sufficient glass-forming ability to fix of the amorphous state at cooling rates implemented by electric discharge alloying with the use of a crystalline electrode. The purpose of the work is one-stage deposition of amorphous coating by electric discharge alloying, using crystalline anode FeWCrMoBC, prepared by casting and studying the properties of modified surface of carbon steel: wettability, high-temperature resistance, tribological properties. Methods and Results. The structure of anode and coatings was investigated by X-ray diffraction analysis in CuKα radiation on a DRON-7 diffractometer. In contrast to the X-ray patterns of the anode material, sharp Bregg reflexes were not observed on the X-ray patterns of the coatings, but a wide halo was present in the range of angles 2Ѳ = 40–50°, which indicates its amorphous structure. The cyclic high-temperature resistance test was carried out at 700 °C for 100 hours. The wear rate and coefficient of friction of the specimens were studied under dry sliding friction at a speed of 0.47 m/s at a load of 25 N with the use of a counterbody made of high-speed steel M45. The influence of the discharge pulse duty cycle on the character of mass transfer (anode erosion, cathode weight gain, mass transfer coefficient) during coating formation was investigated. With a decrease in the duty cycle of the discharge pulses up to 9 times, the erosion of the anode increased up to 5 times, and the cathode mass gain increased up to 2.2 times. The maximum mass-transfer coefficient was achieved at the highest duty cycle. An increase in a number of surface properties of carbon steel after coating was observed: the hardness of the surface of the specimens increased by 2.3–2.6 times; the average thickness of the coatings was in the range of 56–80.6 µm; the wetting angle was in the range of 108.4–121.3°; the coefficient of friction decreased by 1.2–1.4 times; the wear resistance increased by 2–3.3 times; oxidizability in air decreased by 14–18 times. Scope and Conclusions. The achieved higher properties (hardness, wear resistance, high-temperature resistance, and hydrophobicity) of the executive surfaces of parts made of carbon steel after deposition of the proposed coatings can be used in various branches of engineering production. The results of the work confirmed the possibility of deposition of metallic glass coatings by electric discharge alloying with the use of cast anode material FeWCrMoBC on carbon steel.

Experimental investigation of hydrogen production performance of various salts with a chlor-alkali method

In this experimental study, the hydrogen production performance of aqueous solutions of NaCl, KCl, and CaCl2 salts via an electrochemical method through a chlor-alkali reactor is investigated. For this purpose, a laboratory-scale reactor consisting of anode and cathode compartments is built. The compartments of the reactor are separated by a cation exchange membrane which prevents the mixing of anolyte and catholyte solutions and also allows positive ions (Na+, K+, and Ca2+) and some water to pass through. Electrodes made of 316 stainless steel are used in the compartments of the reactor due to their economic efficiency. While the anode compartment of the reactor is fed with the aqueous solutions of NaCl, KCl, and CaCl2 salts one by one, the cathode compartment is fed with one of the diluted aqueous solutions of NaOH, KOH, and Ca(OH)2 bases depending on the type of salt used. Experiments are carried out at three different cell voltages (3, 4, and 5 V) and three different cell temperatures (30, 50, and 70 °C), and five different electrolyte flows (0.4, 0.6, 0.8, 1.0, and 1.2 g/s). Since the reactor dimensions are very small, experiments are also carried out with small changes in the electrolyte mass flow rate. It is observed that active chlorine gas causes serious contamination in the anode compartment and erosion on the electrode in this compartment. Therefore, the expected chlorine gas output from the anode compartment of the reactor is not observed. Luckily, a significant amount of hydrogen gas output is observed from the cathode compartment of the reactor. The minimum hydrogen production rate is 37.23 mL/h when the aqueous solution of CaCl2 is used with a mass flow rate of 0.4 g/s and cell voltage of 3 V at the cell temperature of 30 °C. The maximum hydrogen production rate is 437.72 mL/h when KCl salt solution is used with a mass flow rate of 1.2 g/s and cell voltage of 5 V at the cell temperature of 70 °C.

Improved performance of lithium ion batteries by employment of electrolyte containing nanodiamonds and water

Commercial lithium ion batteries (LIBs) are usually required to avoid the presence of H2O, as the intercalation of H2O molecules would lead to the degradation of both electrolyte and graphite anode, resulting in irreversible failure of the batteries. In this work, we demonstrate that assisted with introducing nanodiamonds (NDs), high concentration H2O in electrolyte (higher than 3000 ppm) can improve the performances of LIBs. For the electrolyte with 5000 ppm H2O and a small amount of NDs, the long-cycle stability and superior reversible capacities of 950 mA h g−1 at 0.1 A g−1 after 100 cycles (130 mA h g−1 at 5 A g−1 after 10,000 cycles) have been realized, which are significantly improved in comparison with the case of sole H2O introduced in the electrolyte. The improvements can be attributed to the synergistic effect of NDs and H2O achieving highly conductive SEI network, enhanced ionic conductivity and separator wettability of electrolyte, mitigated erosion of graphite anode, and increased storage sites for Li+. This work provides an efficient method to not only boost the performances of LIBs but also reduce the cost of production in practical applications.

Modeling and Performance Analysis of Municipal Solid Waste Treatment in Plasma Torch Reactor

Thermal plasma has emerged as a technology with tremendous promise for municipal wastes that should be disposed of sustainably. A numerical simulation of a symmetric turbulent plasma jet from a thermal air plasma torch was developed using COMSOL Multiphysics®5.4 engineering simulation software. The velocities, temperature, arc root motion, and joule heating of the plasma jet were examined under the impact of the gas mass flow rate and current. Moreover, the electrical power required for the municipal solid waste (MSW) processing was estimated. The enthalpy and the effectiveness of the plasma torch were analyzed and discussed. Subsequently an investigation was conducted into the gasification characteristics of MSW using air and steam gases. The torch’s power and efficiency could be enhanced with a higher mass flow rate and temperature. Three operating modes were identified from the current–arc flow combination. Among the plasma gas considered, the air gas plasma torch guarantees an acceptable thermal efficiency and a low anode erosion rate. Plasma gasification produces cleaner syngas with higher efficiency (84%) than the conventional process due to the elevated temperature used during the process that breaks down all the char, dioxins, and tars.

STRUCTURE, MECHANICAL AND TRIBOLOGICAL PROPERTIES OF TI-CR-C-NI-FE COMPOSITE COATINGS

Here we discuss the use of composite cermet SHS electrodes from materials based on titanium carbide, chromium carbide, and nichrome obtained by SHS extrusion for the electrospark deposition of Ti-Cr-C-Ni-Fe composite coatings on metal substrates made of high-speed steel R6M5. Four electrospark alloying modes are considered which correspond to electric discharge energies of 0.2, 0.3, 0.6, and 1.0 J. The plotted experimental curves of the total anode erosion and the total cathode weight gain on the alloying time have a classical form. The effect of the electrospark alloying modes on the structure, mechanical (hardness) and tribological properties of the obtained composite coatings is studied. It is shown that the coating consists mainly of a matrix based on two Cr-Ni-Fe-Csolid and Fe0.7Ni0.3 phases and reinforcement complex carbide Ti0.8Cr0.2C particles, the size of which decreases to less than 100 nm with proximity to the substrate. The hardness of the resulting composite coatings is 10.6-13.5 GPa. The major fraction of carbide particles in the SHS electrode melts during electrospark alloying, and with increasing discharge energy the number of transferred grains in the solid phase increases by a factor of up to 9. Depending on the discharge energy of electrospark alloying, we determine the transfer coefficients of the SHS electrode, the run-in areas of the resulting coatings, and the amount of wear of the coating and counterbody.

Modification of spinel MnCo2O4 nanowire with NiFe-layered double hydroxide nanoflakes for stable seawater oxidation

Currently, direct electrolysis of seawater-based electrolytes rather than fresh water based ones for hydrogen production is gaining more and more attentions for creating a sustainable society. However, using seawater remains more challenges owing to the existence of competitive reactions between chlorine evolution reaction (ClER) or hypochlorite generation reaction and oxygen evolution reaction (OER) and electrode erosion. In this study, a MnCo2O4 nanowire coated with NiFe-Layered Double Hydroxide (NiFe-LDH) layer (MnCo2O4@NiFe-LDH) composite electrocatalyst prepared by a simple two-step hydrothermal method was applied for the seawater electrolysis, which exhibited low overpotentials of 219 and 245 mV at a relatively high current density of 100 mA cm−2 in alkaline simulated and natural seawaters, respectively, as the anode electrocatalyst. It is found that the NiFe-LDH layer on the MnCo2O4 nanowire can serve as Cl- protective layer to hinder the ClER and anode erosion and simultaneously improve the active surface area and intrinsic properties of MnCo2O4 nanowires, allowing for faster kinetics. While, the high valence states of Mn3+, Co3+, Ni3+and Fe3+ played a vital role for OER. In addition, when it was used as the bifunctional electrocatalyst for the overall real seawater splitting, the cell composed of MnCo2O4@NiFe-LDH (-) || MnCo2O4@NiFe-LDH (+) pair only required a low voltage of 1.56 V@10 mA cm−2 and simultaneously maintained excellent stability at a high current density of 100 mA cm−2. Such an electrocatalyst could be a promising candidate for long-term seawater splitting.

Numerical modelling of a direct current non‐transferred thermal plasma torch for optimal performance

AbstractA laminar steady‐state 2D axisymmetric model of a direct current (DC) thermal plasma torch using a magneto‐hydrodynamic approach has been developed. The model takes into account the entire torch system comprising the plasma gas injection, the inner region of the torch, and the jet exiting into the ambient environment. Numerical results are obtained for two different power inputs chosen from published experimental data. The temperature predictions at the torch exit are found in good agreement with experimental results. Velocity analysis of the plasma jet has been presented and the impact of electromagnetic force on jet velocity is analysed. The Lorentz force arising due to the coupling of fluid motion and electromagnetic forces shoots up the jet velocity to significantly high values near the cathode tip. Temperature and velocity profiles are in good agreement with the characteristics of a long laminar plasma jet. An operating value of heat transfer coefficient (h) has been suggested for optimal torch operation, thus ensuring a low anode erosion rate and acceptable thermal efficiency. The argon torch has the maximum temperature and longest jet length among the plasma gases considered.

Performance of a Multigap Multiaperture Pseudospark Switch in Series With the Saturable Inductor

In this study, experimental investigation has been performed for discharge characteristics of a multigap multiaperture (MGMA) configuration of pseudospark switch (PSS) with a saturable inductor (SI) in series at the anode. The impact of the number of inductor cores on the commutation process is studied experimentally. Initially, in the commutation process, when the anode voltage is 40 kV with five toroid cores, the inductor is unsaturated, and it offers high impedance, resulting in a slow current rise rate of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 2.5$ </tex-math></inline-formula> kA/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> with fast voltage drop rate. During the second phase, when the inductor gets saturated and offers low impedance, it leads to a fast-current rise rate of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 4.35$ </tex-math></inline-formula> kA/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> . Due to the SI, the discharge current rise lags behind the breakdown voltage drop of MGMA-PSS. It results in a significant reduction in power dissipation across the switch during the commutation process. Furthermore, equivalent electrical circuit modeling has also been proposed for the estimation of power losses during the commutation process. During the application of 40-kV anode voltage with five inductor cores at 30-Pa background H2 gas pressure, the commutation losses have been reduced up to ≈95%, which also enhanced the performance of PSS. The proposed analysis and optimization of the inductor core would be very much useful for the reduction in the anode erosion and improved the switching performance of the MGMA-PSS.

Nicotinic acid as a novel inhibitor for alkaline cobalt CMP: Experiment and molecular simulation

Cobalt (Co) is the interconnect metal of integrated circuits with the feature size of 10 nm and below, and Co corrosion is the main problem in cobalt interconnect chemical mechanical polishing (CMP). The introduction of inhibitors is one of the most ideal approaches to reduce corrosion. In this work, useful insights into the corrosion inhibition performance of nicotinic acid (NA), a green inhibitor, on cobalt film in alkaline medium were investigated via electrochemical characterization, surface analysis, quantum chemical calculation, and molecular dynamics (MD) simulation, as well as the adsorption mechanism at atomic level was explored. NA belongs to anodic erosion inhibitor and its inhibition efficiency reached a maximum of 86.65 % at the concentration of 80 mM pH 10, which was identified by the contact angle and potentiodynamic polarization (PDP) test. The electrochemical impedance spectra (EIS) suggested that the surface resistance was enhanced to prevent corrosion. Free energy obtained from the Langmuir model indicates that NA molecules are physically and spontaneously adsorbed on cobalt surface. XPS results further confirmed this point, which reveals that NA exists in the form of Nic2− in alkaline solution and forms a Co(OH)2(Nic2-) molecule group (Co(II)-NA) on Co surface. Additionally, quantum chemical calculations based on density function theory (DFT) have approved that CN bond and carboxyl group are the active sites of NA molecule and form the most significant electrostatic adsorption force with cobalt atoms. Moreover, it can be inferred from MD simulations that NA molecules are spontaneously and physically adsorbed on the cobalt surface at a certain angle. In a word, NA manifests its effectiveness in corrosion inhibition of cobalt and will become a potential cobalt CMP inhibitor. The research methods and results of this paper are beneficial to the study of the adsorption characteristics and inhibition mechanism of inhibitors on the metal surface, and provide a theoretical basis for optimizing the composition of Co CMP slurry.

Electrode Erosion During High-Voltage Electrical Discharge in a Liquid

The paper presents the results of experimental studies of the mass value of electrode (anode) erosion during a high-voltage electric discharge in a liquid. The results obtained made it possible to determine the influence of technological parameters and operating conditions of high-voltage electric discharge installations on the mass erosion of an anode. It is noted that with an increase in the specific electrical conductivity of the working fluid and in the length of the interelectrode gap, a decrease in the value of the mass erosion of the anode is observed. Comparison of mass erosion of anodes made of copper, steel, and aluminum showed that among them the steel anode has the highest erosion resistance during an electric discharge in water. Based on the results of the performed experimental studies, an empirical technique was developed that allows to estimate the mass erosion of the anode in one electric discharge in water.

Collective acceleration of deuterons from the residual chamber atmosphere in a Luce diode

The collective acceleration of deuterons from the residual atmosphere of the Luce diode chamber is studied at a pressure of gaseous deuterium in the range of 0.029–0.177 Pa. The energy and number of accelerated deuterons were determined by neutron time-of-flight spectrometry and by measuring the activity of 13N and 11C radionuclides induced in B4C targets by the reactions 12C(d,n)13N and 10B(d,n)11C, the activity of the 7Be induced by the 10B(p,αγ)7Be reaction was used to control the number of accelerated protons. The neutron time-of-flight shows that the gaseous products of polyethylene anode erosion have no noticeable effect on the energy and number of deuterons accelerated in shots following the first shot of the series. It is shown that the energy of deuterons accelerated from the residual atmosphere is the same as during their acceleration from the near-anode plasma using a deuterated polyethylene anode, but the number of accelerated deuterons per shot depends on the deuterium pressure exponentially, still it is by an order of magnitude smaller even at a pressure of 0.177 Pa. The exponential growth is due to the fact that the number of accelerated deuterons strongly depends on the diode current, which increases noticeably with increasing the deuterium pressure.

ПОЛУЧЕНИЕ МЕТАЛЛОМАТРИЧНЫХ СПЛАВОВ ДЛЯ ИЗНОСОСТОЙКИХ ЭЛЕКТРОИСКРОВЫХ ПОКРЫТИЙ

The study objective is to obtain and study metal matrix alloys based on NiAl intermetallic compound with different concentrations of Ni for forming wear-resistant coatings on steel 45. &#x0D; The problems to which the paper is devoted are: obtaining electrode materials based on NiAl intermetallic compound with different concentrations of Ni and studying their structure; studying the mass transfer during electrospark deposition on steel 45; studying the comparative wear resistance of the coatings obtained. &#x0D; Research methods: electrode alloys are obtained by the method of liquid-phase self-propagating high-temperature synthesis; electro spark alloying is used to create wear-resistant coatings; the microstructure of the obtained alloys is studied by the method of metallographic analysis.&#x0D; The novelty of the work: for the first time, the influence of different Ni concentration values on the wear resistance of NiAl electrospark coatings on steel 45 is studied.&#x0D; Study results: the microstructure of the obtained alloys consists of doped Cr and Co grains of NiAl matrix with a different Ni/Al ratio, along the boundaries of which the compounds of all alloy components are located. When forming coatings by electrospark method, time dependences of changes in anode erosion, cathode gain and mass transfer coefficient are obtained. &#x0D; Conclusions: NiAl metal-based alloys with different concentrations of Ni were smelted using a liquid-phase SHS method using charge consisting of metal oxides and mineral concentrates containing tungsten and zirconium; the microstructure of the obtained alloys consists of doped Cr and Co grains baseds on NiAl, along which boundaries compounds of all the constituent components of the alloy are concentrated, including Zr and W. Experimental results of anode erosion, cathode gain, and mass transfer coefficient were obtained while forming the coatings with the alloys using electrospark method, and it was found during wear resistance tests that with an increase of Ni concentration in the alloy, the wear resistance increases.

A Highly Efficient Ion and Electron Conductive Interlayer To Achieve Low Self-Discharge of Lithium-Sulfur Batteries.

The practical use of lithium-sulfur (Li-S) batteries is limited by serious self-discharge, fast capacity loss, and severe lithium anode erosion due to the shuttling of lithium polysulfides (LiPSs). Herein, we developed a highly efficient ion and electron conductive interlayer composed of Ti2(SO4)3/carbon composite layer-coated Li1.3Al0.3Ti1.7(PO4)3 (CLATP) and graphene to effectively block the diffusion of polysulfide anions but allow rapid Li ion transfer, therefore significantly inhibiting the self-discharge and boosting the cyclic stability of Li-S batteries. The Ti2(SO4)3/carbon thin protective layer endows an optimized adsorption ability toward LiPSs and avoids the side reactions between LATP and LiPSs. The high electronic conductivity of graphene and high ionic conductivity of CLATP ensures the hybrid interlayer rapid electron and fast Li ion transport. As a result, the Li-S battery with the hybrid interlayer shows a high discharge capacity of 671 mAh g-1 after 500 cycles with an extremely low capacity fading of 0.022% per cycle at 1 C. Moreover, the battery shows no self-discharge even after rest for 12 days. This work opens up a new way for the design of functional separators to significantly improve the electrochemical performance of Li-S batteries.

Effect of Chromium Addition and Regimes during Electrospark Alloying with Aluminum Matrix Anode Material of Steel 45

Introduction. Electrospark alloying is used to produce hardening coatings. Anodic materials with unique properties include metal matrix composites based on aluminum. The aim of the work is to develop new aluminum matrix anode composite materials with high efficiency indicators during electrospark alloying of carbon steel 45. Materials and Methods. Structural carbon steel 45 was used as the substrate (cathode). Aluminum matrix materials are chosen as the anode materials. The value of the cathode weight increment and the anode erosion were determined by the gravimetric method on the Shinko Denshi HTR-220 CE electronic scale with an accuracy of ±∙10–4 g. To study the microstructure and metallography of the surface of the anode materials, the microscopes EVO-50 XVP and Altami MET 3 APO from S. ZEISS were used. The device CALOTEST CSM Instruments was used to study coatings for microabrasive wear. Results. There is developed a methodological scheme for achieving the efficiency of the electric spark alloying parameters and the properties of the doped layer depending on the composition of the anodic metal matrix composite material based on aluminum with the addition of chromium and processing modes. The mode of Institute of Materials Science electrospark installation with pulse energy of 14.4 J was set for anode material application during electrospark alloying. It is established that after electric spark alloying of steel 45, the hardness and wear resistance of the surface increase by 2-3 times, and the heat resistance ‒ by 5–18 times. Discussion and Conclusion. The series of increasing the cathode mass, the erosion resistance of the electrode materials, mass transfer coefficient, heat resistance, hardness and wear resistance of the alloyed layer are obtained. The obtained series are a convenient tool for achieving various efficiency parameters in electric spark alloying depending on the selected anode material and processing modes.

Experimental investigation on electro-osmotic treatment combined with vacuum preloading for marine clay

An electro-osmotic consolidation (EO) combined with vacuum preloading (VP) was investigated on marine clay using laboratory tests. To improve consolidation efficiency and reduce the settlement difference, a new prefabricated device was designed to combine EO and VP for the tests. The results indicated that the vacuum preloading with intermittent electro-osmotic consolidation (VP–I-ECM) provided more water discharge with higher discharge rate and produced larger soil settlement compared to traditional vacuum preloading and electro-osmotic consolidation. For the combined method, the VP effectively removed water from the soil for the first 12 h, and its efficiency decreased with the time. After 12 h, the intermittent EO was used to further consolidate the soil and maintain a high level of drainage rate. Test results also showed that the combined method of VP-I-ECM significantly improved the shear strength and bearing capacity of the marine clay to satisfy the construction requirements with a significant reduction in the anode erosion and the energy consumption. This research study provides useful information for the design guide and practical application of the combined technique for improving marine clay.

Selective synthesis of DC carbon arc-generated carbon nanotube and layered-graphene and the associated mechanism

Herein we report how an anode is eroded and the eroded mass is deposited on the cathode surface at different arc currents () in a DC carbon arc discharge using roughly oriented graphite (ROG) as electrodes. It was found that the nature of anode erosion critically depends on and has profound effects on the morphology of the as-synthesized cathode deposits (CDs), the conversion efficiency of the system to form the CDs and their compositions. By characterizing the as-synthesized CDs in their totality by transmission electron microscopy, Raman spectroscopy, and x-ray diffraction it was found that there exists a critical value of below which the arc remains constricted, and above which the arc becomes intense. It was further found that the system can selectively generate both carbon nanotubes (CNTs) and layered-graphene sheets (LGs) when the carbon arc runs in constricted and intense modes, respectively. By the suitable adjustment of it is possible to switchover between the aforementioned arc-modes. Based on the experimental results, a semi-empirical model encompassing the plausible effects of rapid and random movement of the anode spot on the used ROG anode surface was developed to provide new insights into the growth mechanism of arc-generated CNTs and LGs. The state-of-the-art presented in this paper could facilitate the carbon arc discharge route for the tailored synthesis of highly crystalline CNTs and LGs.

Numerical Simulation and Analysis of Arc Anode Erosion Process with Electrode Rotation

A three-dimensional geometric model of anode contact of vacuum circuit breaker is established. Considering the influence of electrode rotation on vacuum arc and anode thermal process, a physical model of phase transformation process is established for the melting and evaporation of anode surface. The solid-liquid mixing area is treated by the description method of porous media, and the numerical simulation of anode thermal process is carried out. The conclusion is that with the increase of time, the anode surface temperature increases, molten pool development, molten pool depth deepening, in addition, with the increase of electrode speed, the highest temperature on the surface of the contact and the size of the molten pool were reduced, the temperature distribution more uniform. It provides theoretical basis for evaluating the breaking capacity of vacuum circuit breaker.