Arc Ablation Research Articles

Experimental study on arc ablation occurring in a contact strip rubbing against a contact wire with electrical current

A series of tests on arc discharge were carried out to better understand the wear mechanism of a contact strip rubbing against a contact wire with electrical current. The arc discharge process was recorded with a high-speed camera. The arc voltage drop and electric current were measured throughout the test. The accumulated arc discharge energy was evaluated. Experimental results show that the wear rate of the contact strip is approximately directly proportional to the accumulated arc discharge energy in logarithmic coordinates. Increasing the normal force can suppress arc discharge and decrease wear of the contact strip.

Study on the Electrical Arc Ablation Performance of Al<sub>2</sub>O<sub>3</sub> Reinforced Cu-Matrix Composites

The Al2O3 particle reinforced Cu-based composites (Al2O3/Cu) were prepared by internal oxidation technology. The electrical arc ablation performance of Al2O3/Cu composite was compared with copper H62 through a series of ablation experiments. The results indicate that both the quality lost and ablation diameter of copper H62 samples are larger than those of Al2O3/Cu composites in condition of the same ablating current. The large ablation pits observed by scanning electron microscopy (SEM) indicated that the arc ablation of copper H62 is concentrate and serious. The result of energy dispersive spectrometer (EDS) shows that the molten copper alloy of H62 has been transferred and sprayed. However, the arc ablation pits of Al2O3/Cu composites are dispersing and slight. The transferring and spaying material of Al2O3/Cu composite is mainly from Cu-matrix. The anchoring effect and protection function of the uniformly dispersing Al2O3 grains, which are executed onto the Cu-matrix, has been considered to contribute to the excellent arc ablation performance of composite Al2O3/Cu.

Friction and Wear Behavior of Copper-Graphite Composite Material in High-Speed Sliding with Current

In the present study, the friction and wear behaviors of copper-graphite composite against GCr15 steel in high-speed sliding with current were investigated. The worn surfaces and wear debris were analyzed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), and the wear mechanisms were discussed. It shows that the current plays an important role in the high-speed dry sliding of copper-graphite composite against GCr15 steel. With increasing current, the friction coefficient decreases, and the wear rate increases. The wear mechanisms of the copper-graphite composite are main abrasion and fatigue without current, and that of with current are main fatigue, arc ablation.

New Perspectives on Nanomaterial Aquatic Ecotoxicity: Production Impacts Exceed Direct Exposure Impacts for Carbon Nanotoubes

Environmental impacts due to engineered nanomaterials arise both from releases of the nanomaterials themselves as well as from their synthesis. In this work, we employ the USEtox model to quantify and compare aquatic ecotoxicity impacts over the life cycle of carbon nanotubes (CNTs). USEtox is an integrated multimedia fate, transport, and toxicity model covering large classes of organic and inorganic substances. This work evaluates the impacts of non-CNT emissions from three methods of synthesis (arc ablation, CVD, and HiPco), and compares these to the modeled ecotoxicity of CNTs released to the environment. Parameters for evaluating CNT ecotoxicity are bounded by a highly conservative "worst case" scenario and a "realistic" scenario that draws from existing literature on CNT fate, transport, and ecotoxicity. The results indicate that the ecotoxicity impacts of nanomaterial production processes are roughly equivalent to the ecotoxicity of CNT releases under the unrealistic worst case scenario, while exceeding the results of the realistic scenario by 3 orders of magnitude. Ecotoxicity from production processes is dominated by emissions of metals from electricity generation. Uncertainty exists for both production and release stages, and is modeled using a combination of Monte Carlo simulation and scenario analysis. The results of this analysis underscore the contributions of existing work on CNT fate and transport, as well as the importance of life cycle considerations in allocating time and resources toward research on mitigating the impacts of novel materials.

Study on the Electrical Arc Ablation Performance of Nano-SiC<sub>W</sub> Reinforced Cu-Matrix Composites

The nano-SiC whisker reinforced Cu-matrix composites (SiCw/Cu) were obtained by powder metallurgy processes. The electrical arc ablation performance of composite SiCw/Cu was compared with copper H62 through stagnation-point ablation experiments. The results indicated that the qualities of copper H62 samples decreased with the increasing of ablating current; and the qualities of SiCw/Cu samples firstly increased and then decreased with the increasing of ablating current. Ablation mechanism research indicates the ablation hole of SiCw/Cu is smaller than copper H62, but it produced micro cracks because of different thermal expansion coefficients between nano-SiC whisker and Cu-matrix. At the same time, nano-SiC whisker happens to intricate oxidation reaction during arc ablation, it can reduce Cu-matrix smelts and sprays by absorbing arc energy. The anchoring effect and protection for the copper matrix of the uniformly dispersing nano-SiC whiskers have been considered to contribute the excellent arc ablation performance of composite SiCw/Cu.

Tribological and electric-arc behaviors of carbon/copper pair during sliding friction process with electric current applied

The tribological behaviors of carbon block sliding against copper ring with and without electric current applied were investigated by using an advanced multifunctional friction and wear tester, and the electric-arc behaviors were analyzed in detail. The results show that the normal load is one of the main controlling factors for generation of electric arc during friction process with electric current applied. The strength of electric arc is enhanced with the decrease of normal loads and the increase of electric currents. The unstable friction process and the fluctuated dynamic friction coefficients are strongly dependent upon the electric arc. The wear volumes and the wear mechanism of carbon brush were affected by the electric arc obviously. As no electric arc occurs, no clear discrepancy of the wear volumes of the carbon samples with and without electric current applied could be detected. While the wear mechanisms are mainly mechanical wear. However, under the condition of the electric arc appearance, the wear volume of carbon with electric current applied increases much more rapidly than that without electric current applied and also increases obviously with the increase of electric current strengths and the decrease of normal loads. The wear mechanisms of carbon block are mainly electric arc ablation accompanying with adhesive wear and material transferring.

Friction and wear behavior of pure carbon strip sliding against copper contact wire under AC passage at high speeds

A series of tests on the friction and wear behaviour of pure carbon strip/copper contact wire with alternating current were conducted on a ring-on-block sliding tester at a high speed. The electric current, normal force and sliding velocity have distinct effects on the test results. The worn scar has the smallest size without electric current. The worn scar becomes larger with increasing electric current. Arc ablation pits, dark stream-lines of arc ablation, slipping marks, spalling blocks and the copper-like layer are found on the worn surfaces. Arc erosion, abrasive wear and adhesive wear are main wear mechanisms.

Effect of Arc Discharge on Friction and Wear Behaviors of Stainless Steel/Copper-Impregnated Metalized Carbon Couple under Electric Current

Friction and wear tests of stainless steel rubbing against copper-impregnated metalized carbon with electric current were carried on the pin-on-disc tester. The result indicates that arc discharge occurs in the process of experiments, and the intensity of arc discharge of interface increases with increasing of electric current and sliding velocity. As increasing of the arc discharge intensity, friction coefficient shows a tendency of slightly increase. While the rate of copper-impregnated metalized carbon material increase significantly with the increase of arc discharge intensity. Through observing the worn surface morphology of pin samples, it is found that the abrasive wear is dominant at small arc discharge due to worn particles and arc ablation craters, but arc erosion and oxidation wear are the main wear mechanisms in condition of large arc discharge due to arc discharge and its producing high temperature. The materials transfer of contact couple occurs in the process of friction and wear.

The selective hydrogenation of acetylene on palladium–carbon nanostructured catalysts

A novel carbon nanostructured material was produced using the electric arc ablation method. The product was purified using a combination of extraction, acid reflux and selective oxidation. The purified carbon nanostructured material (CNS) consisted of single-walled carbon nanotubes (SWNTs) with an average tube diameter of 1.3 nm, and interconnected, nanostructured and multiwalled globules. Catalysts containing 1 and 5% (m/m) Pd supported on the CNS were synthesized involving an activation step, followed by electroless plating of the Pd on the CNS. The Pd/CNS catalysts consisted of Pd particles with an average diameter of 6 nm highly dispersed on the CNS. The activity and selectivity of the 1 and 5% Pd/CNS catalysts towards the hydrogenation of acetylene were determined under different conditions of temperature and pressure. The results were compared to that obtained for reference catalysts, namely 1 and 5% Pd/Al 2O 3, and 1 and 5% Pd/activated carbon, under the same conditions. The Pd/CNS catalysts proved to have superior selectivity and activity, and formed less green oil and no detectable coke formation compared to the commercial catalysts under the experimental conditions. It is postulated that this was due to reduced hydrogen spillover and sintering effects and the different surface morphology of the Pd/CNS catalysts compared to the commercial products.

Influence of the spring stiffness on friction and wear behaviours of stainless steel/copper-impregnated metallized carbon couple with electrical current

Influence of the support stiffness of the pins on friction and wear behaviours of stainless steel/copper-impregnated metallized carbon with electric current is studied on a pin-on-disc tester. The result indicates that the coefficient of friction increases with an increase of the stiffness at a low velocity or with a small electric current, while at a high velocity or with a large electric current the friction coefficient decreases firstly and then increases as the stiffness increases. The wear rate of pin samples with elastic supports is much smaller than that with rigidity. When the stiffness is equal to 19,000 N/m the wear rate is found to be lowest. In the test, it is observed that there are two different arc discharge phenomena. It is found that the spark discharge is dominant when the pin is connected to power supply anode, while the arc discharge mainly occurs when the pin is connected to power supply cathode. Morphology of the worn surfaces of copper-impregnated metallized carbon is observed with SEM. It is found that the abrasive and adhesive wears are dominant at low velocity or with small electric current, while oxidative wear and arc ablation mainly occurs at high velocity or with large electric current. In comparison with cross-section scar profiles and surface roughness of pin samples in different stiffness, it is found that the wear of pins is severest when it is supported with rigidity and is slightest when it is supported by spring with an appropriate stiffness (19,000 N/m).

Coating deposition using vacuum arc and ablation metal plasma

An innovative concept in the development of advanced coating deposition and ion implantation method including an application of filtered DC metal plasma or ablation plasma and high-frequency short-pulsed negative bias voltage with a duty factor in the range 10–99% is considered. The regularities of metal ion implantation and vacuum arc metal plasma or ablation plasma deposition for conducting and insulating materials are considered. It was shown that plasma based ion implantation as well as high-concentration plasma ion implantation with compensation of ion surface sputtering by plasma deposition as well as ion-assisted coating deposition may be realized for metal and dielectric samples by variation of negative bias potential in the range of 0–4·10 3 V, pulse repetition rate smoothly adjusted in the range of (2–4.4) × 10 5 pps and pulse duration in the range of 0.5–2 µs. It was experimentally shown that at coating deposition from ablation plasma obtained by high intensity ion beam ( j = 300 A/cm 2, E = 350 keV, τ = 90 ns) influence on the target, the breakdown of the plasma sheet occurred at dc negative bias potential on a substrate more than 60 V. The transfer to 0.5 µs duration pulses allowed us to increase the bias potential up to − 4 kV. The possibility of high-frequency, short-pulsed plasma-immersion ion implantation and deposition method application for coating deposition from vacuum arc and ablation plasma with high adhesive strength and improved exploitation characteristics is discussed in the paper.

Friction and wear behaviour of stainless steel rubbing against copper-impregnated metallized carbon

A series of experimental tests were carried out using stainless steel rubbing against copper-impregnated metallized carbon under electrical current on a pin-on-disc test rig. The test parameters include the sliding speed of 60–100 km/h, normal force of 40–80 N and electrical current of 0–50 A. During testing, the friction coefficient and wear volume were recorded. The topography of worn surfaces was also observed with SEM. The cross sectional profiles of worn surfaces of stainless steel were measured with Ambios profiler. The result displays that electrical current, normal load and sliding speed have a distinct effect on the friction and wear behaviour of stainless steel rubbing against copper-impregnated metallized carbon. Without electric current, the friction coefficient is largest but the wear volume of copper-impregnated metallized carbon is lowest. With increasing electric current, the friction coefficient decreases while the wear volume of copper-impregnated metallized carbon increases. Through the whole test, it is found that the wear loss of stainless steel was light. The wear of copper-impregnated metallized carbon becomes severe when electrical current or sliding speed is high. When the electrical current or sliding speed is high, arc ablation is a dominant wear mechanism of copper-impregnated metallized carbon.

Single-Walled Carbon Nanotubes Synthesis: A Direct Comparison of Laser Ablation and Carbon Arc Routes

Carbon arc and chemical vapor deposition are at present the most efficient methods for mass production of single-walled carbon nanotubes. However, laser ablation is renowned for high quality nanotubes with narrow diameter distributions and hence is also of great interest. The aim of this work was to compare both the carbon arc and laser ablation techniques with respect to the quality--and relative yield of the produced SWCNTs. For this comparative study we used Fe as the catalyst, which is known not to be very active in laser ablation. However, we show this is not the case when H2 is included in the reaction. The reactions for both synthesis routes were carried out in a N2-H2 (95-5% vol.) atmosphere. The same homogenous carbon rods with different iron contents, between 1 and 5 at.% were used as the carbon feedstock and catalyst supply in both synthesis routes. Additionally, two types of carbon rods containing 1 at.% Fe with different graphitization degrees were also investigated. In the arc-discharge case, the low-graphitized electrode produced a web-like product rich in SWCNTs, while the high-graphitized carbon rods yielded soot containing carbon-encapsulated iron nanocrystallites, amorphous carbon nanoparticles, and surprisingly a small fraction of SWCNTs. With laser ablation synthesis, the Fe content and the reactor temperature significantly influenced the SWCNTs yield. Carbon arc plasma diagnostics were also performed. By using optical emission and Absorption spectroscopy the plasma temperature, C2 and CN radical content in the arc zone were determined.

Environmental Assessment of Single‐Walled Carbon Nanotube Processes

SummaryThe environmental assessment of nanomanufacturing during the initial process design phase should lead to the development of competitive, safe, and environmentally responsible engineering and commercialization. Given the potential benefits and concerns regarding the use of single‐walled carbon nanotubes (SWNTs), three SWNT production processes have been investigated to assess their associated environmental impacts. These processes include arc ablation (arc), chemical vapor deposition (CVD), and high‐pressure carbon monoxide (HiPco). Without consideration of the currently unknown impacts of SWNT dispersion or other health impacts, life cycle assessment (LCA) methodology is used to analyze the environmental impact and provide a baseline for the environmental footprint of each manufacturing process. Although the technical attributes of the product resulting from each process may not be fully comparable, this study presents comparisons that show that the life cycle impacts are dominated by energy, specifically the electricity used in production. Under base case yield conditions, HiPco shows the lowest environmental impact, while the arc process has the lowest impact under best case yield conditions.

The performances of TiB2-contained iron-based coatings at high temperature

The TiB2-contained composite Fe–B–C coatings are deposited by the plasma transferred-arc (PTA) powder surfacing process. The coating's thermal ability, arc ablation resistance and wear resistance at high temperature were analyzed. It is concluded that TiB2-contained composite Fe–B–C coating having excellent wear resistance at 600 °C and tempering resistance at 900 °C. Furthermore, this coating can effectively resist the arc ablation (120 A arc currents) within 7 s.

Atmospheric pressure microwave torch for synthesis of carbon nanotubes

The microwave (mw) plasma torch at atmospheric pressure has been studied for carbon nanotube (CNT) synthesis. The depositions were carried out on silicon substrates with 5–15 nm thin iron catalytic overlayers from the mixture of argon, hydrogen and methane. The optical emission spectroscopy of the torch showed the presence of C2 and CH radicals as well as carbon and hydrogen excited atoms. The vicinity of the substrate influenced the relative intensities and increased the emission of C2. For fixed mw power, the temperature of the substrate strongly depended on its position with respect to the nozzle electrode and on the gas mixture, particularly the amount of H2. The speed of the substrate heating during an early deposition phase had a significant effect on the CNT synthesis. An abrupt increase of the temperature at the beginning increased the efficiency of the CNT synthesis. Areas of dense straight standing CNTs, 30 nm in average diameter, with approximately the same sized iron nanoparticles on their tops were found in accordance with the model of growth by plasma enhanced chemical vapour deposition. However, the deposit was not uniform and a place with only several nanometres thick CNTs grown on much larger iron particles was also found. Here, taking into account the gas temperature in the torch, 3100–3900 K, we can see similarities with the ‘dissolution–precipitation’ model of the CNT growth by high temperature methods, arc or laser ablation.

Chemical models for simulating single-walled nanotube production in arc vaporization and laser ablation processes.

Chemical kinetic models for the nucleation and growth of clusters and single-walled carbon nanotube (SWNT) growth are developed for numerical simulations of the production of SWNTs. Two models that involve evaporation and condensation of carbon and metal catalysts, a full model involving all carbon clusters up to C80, and a reduced model are discussed. The full model is based on a fullerene model, but nickel and carbon/nickel cluster reactions are added to form SWNTs from soot and fullerenes. The full model has a large number of species--so large that to incorporate them into a flow field computation for simulating laser ablation and arc processes requires that they be simplified. The model is reduced by defining large clusters that represent many various sized clusters. Comparisons are given between these models for cases that may be applicable to arc and laser ablation production. Solutions to the system of chemical rate equations of these models for a ramped temperature profile show that production of various species, including SWNTs, agree to within about 50% for a fast ramp, and within 10% for a slower temperature decay time.

Thermomechanical properties of TiC particle-reinforced tungsten composites for high temperature applications

Tungsten and tungsten alloys are widely used in high temperature environments where arc ablation or mechanical deformation and damage are the main sources of materials failure. For high temperature critical applications in thermomechanical environments, however, the low strength limits the use of tungsten and tungsten alloys. Hence, new tungsten based materials with good high temperature thermomechanical properties need to be developed in order to extend the use of tungsten. TiC particle-reinforced tungsten based composites (TiC p/W) were fabricated by hot pressing at 2000 °C, 20 MPa in a vacuum of 1.3×10 −3 Pa. The composites were examined with respect to their thermophysical and mechanical properties at room temperature and at elevated temperature. Vickers hardness and elastic modulus increased with increasing TiC content from 0 to 40 vol.%. The highest flexural strength, 843 MPa, and the highest toughness, 10.1 MPa m 1/2, of the composites at room temperature were all obtained when 20 vol.% TiC particle were added. As the test temperature rose, the flexural strength of the TiC p/W composites firstly increased and then decreased, except in the monolithic tungsten. The highest strength of 1155 MPa was measured at 1000 °C in the composite containing 30 vol.% TiC particles. The strengthening effect of TiC particles on the tungsten matrix is more significant at high temperatures. With the addition of TiC particles, the thermal conduction of tungsten composites was drastically decreased from 153 W m −1 K −1 for monolithic W to 27.9 W m −1 K −1 for 40 vol.% TiC p/W composites, and the thermal expansion was also increased. The new composites are successfully used to make high temperature grips and moulds.

Effects of dielectric material on arc plasma pressure and ablation measurement in high-power apparatus

We measure some characteristic parameters to investigate the electrical discharge in different types of insulators in the energy range 150-500 J. By varying the type of insulator and the confining geometry, we quantify their specific influence on the pressure, the dissipated energy, and the ablated mass. These considerations are useful to increase the knowledge of the physical mechanisms which play a role in the high-current plasma-wall interaction. In agreement with previous theoretical works, we show two opposite behaviors between polyethylene and polyoxymethylene in terms of ablated mass and graphite formation.

Relation between Gas Blast Characteristics and Gas Passage Structure of the Thermal Puffer Type Gas Circuit Breaker

In order to evaluate thermal interruption capability of gas circuit breaker, we consider that mass flow rate in nozzle throat at around current zero points is the most effective parameter, because it is closely related to the cooling capability of arc. In thermal puffer type gas circuit breaker, the mass flow rates depend not only on puffer pressure but also on gas passage structure. So using a calculation program of gas blast characteristics taking both arc energy and ablation gas into consideration, the relations between the mass flow rate at current zero points and gas passage structure were investigated. As the results, we found that shorter gas passage length greatly increases the mass flow rate at current zero points, although it does not influence puffer pressure formation so much. We also found that optimum cross sectional area of gas passage is a bit smaller than that of nozzle throat. If thermal interruption limit were determined by mass flow rate at current zero points, the shorter gas passage length and optimized cross section area will increase the SLF interruption capability of thermal puffer type gas circuit breaker.This paper describes the detail of the results of simulations and discussions.