Electrical Discharge Conditions Research Articles

AlC3 monolayer: Highly responsive and selective gas sensing material for SF6 decomposed gases (SOF2, SO2F2 and SO2)

Sulfur hexafluoride (SF6) is widely employed in industrial applications due to its interesting insulating properties. However, under electrical discharge conditions, it can undergo decomposition, yielding hazardous gases such as SOF2, SO2F2, and SO2, which can pose significant risks due to their increased toxicity and corrosive nature, affecting human health, the environment, and equipments. In this investigation, we employed density functional theory and ab-initio molecular dynamics to evaluate the stability of AlC3 monolayer and investigate its sensing capabilities. The findings establish the AlC3 monolayer as a champion material for detecting SF6 decomposition gases, specifically SOF2, SO2F2, and SO2. Importantly, the AlC3 monolayer exhibited low sensitivity to humidity and other gases, including CO2, CO, HF, H2, HCN, and H2S, highlighting its exceptional selectivity. SO2F2 exhibited the substantial adsorption energy of −1.36 eV, a work function of 5.2 eV, and a −0.69e charge transfer. Similarly, SO2 and SOF2 displayed significant adsorption energy (-1.19 eV and −1.08 eV, respectively), work functions (4.55 eV and 4.81 eV), and charge transfers (-0.61e and 0.78e). The significant variation in work function upon SO2F2 adsorption indicates the AlC3 monolayer's potential selectivity for SO2F2 over SO2 and SOF2, making it a promising material for surface work function modulated transistors. Ab-initio molecular dynamics simulations confirm AlC3 monolayer stability after adsorption at 300 K, validating predicted positions by density functional theory.

Analysis of treatment quality in electrical discharge conditions grinding with changing polarity of electrodes

Analysis of treatment quality in electrical discharge conditions grinding with changing polarity of electrodes

Deriving Optimized PID Parameters of Nano-Ag Colloid Prepared by Electrical Spark Discharge Method.

Using the electrical spark discharge method, this study prepared a nano-Ag colloid using self-developed, microelectrical discharge machining equipment. Requiring no additional surfactant, the approach in question can be used at the ambient temperature and pressure. Moreover, this novel physical method of preparation produced no chemical pollution. This study conducted an in-depth investigation to establish the following electrical discharge conditions: gap electrical discharge, short circuits, and open circuits. Short circuits affect system lifespan and cause electrode consumption, resulting in large, non-nanoscale particles. Accordingly, in this study, research for and design of a new logic judgment circuit set was used to determine the short-circuit rate. The Ziegler–Nichols proportional–integral–derivative (PID) method was then adopted to find optimal PID values for reducing the ratio between short-circuit and discharge rates of the system. The particle size, zeta potential, and ultraviolet spectrum of the nano-Ag colloid prepared using the aforementioned method were also analyzed with nanoanalysis equipment. Lastly, the characteristics of nanosized particles were analyzed with a transmission electron microscope. This study found that the lowest ratio between short-circuit rates was obtained (1.77%) when PID parameters were such that Kp was 0.96, Ki was 5.760576, and Kd was 0.039996. For the nano-Ag colloid prepared using the aforementioned PID parameters, the particle size was 3.409 nm, zeta potential was approximately −46.8 mV, absorbance was approximately 0.26, and surface plasmon resonance was 390 nm. Therefore, this study demonstrated that reducing the short-circuit rate can substantially enhance the effectiveness of the preparation and produce an optimal nano-Ag colloid.

Influence of cellulose paper on gassing tendency of transformer oil under electrical discharge

The intent of this work is to evaluate the influence of cellulose insulation paper on gassing tendency of transformer oil under electrical discharge conditions. For comprehensive enumeration, insulation oil was thermally stressed at 115°C as per ASTM D 1934 with a controlled thermal aging history. The thermally aged oils were considered for gassing tendency evaluation as per ASTM D 6180 (5 hours, 10 kV AC) in the presence of cellulose. Different cellulose Kraft paper proportions including 0, 10, 20, and 30% of aged oil were introduced in to discharge cell. Different cellulose proportions and aging conditions were considered to understand the impact of cellulose while understanding the decomposition aspects of insulation. Diagnostic measurements with those including dissolved gas analysis, moisture, interfacial tension, turbidity, dissolved decay contents, acidity, and dissipation factor were performed before and after gassing tendency evaluation. It was found that, cellulose paper aids significantly in increasing dissolved gases and moisture in oil during electrical discharge. Importantly, diagnostic measurements have shown the ability of paper to absorb certain decomposition products during the discharge process.

Comparative study of coupling to symmetric and antisymmetric cladding modes in long-period fiber gratings

ABSTRACTWe analyse the influence of coupling to symmetric and antisymmetric cladding modes in arc-induced Long-Period Fiber Gratings for temperature and strain sensing. The origin of this difference in energy coupling is related to the fabrication process of these gratings and depends on the electric arc discharge conditions, which modulates the refractive index and geometry of the optical fiber. Finally, results demonstrate the performance of different cladding modes excited in arc-induced LPFGs to temperature and strain applications and, in addition, indicate which coupling might be appropriate to certain sensing applications.

An Experimental Study of Plasma Cracking of Methane Using DBDs Aimed at Hydrogen Production

We report the results of an experimental campaign about the production of hydrogen from methane cracking using a non-thermal plasma. Experiments have been performed using a nanosecond pulse high-voltage generator in a cylindrical dielectric barrier electrode setup. Our experiments show that high methane conversion could be achieved by pulsed electrical discharges in DBD configuration. Conversion could be as high as 60%, with a hydrogen yield of about 25%. The energy costs lie in the range 30–40 eV for molecule. Another set of experiments using a traditional sinusoidal dielectric barrier discharge reactor suggests that argon dilution could improve the performances of plasma methane reforming. A similar suggestion could be inferred by analyzing the results of numerical simulations of the gas-phase chemical kinetics evolution under pulsed electrical discharge conditions.

Stability of mineral oil and oil–ester mixtures under thermal ageing and electrical discharges

This study summarises the results of an experimental investigation on the stability of mineral-based oil mixtures when they are confronted with different ratios of synthetic ester under conditions of electrical discharge, electrical breakdown and a combination of both. The condition of the oil samples was assessed using diagnostic techniques such as gassing tendency, turbidity, dissolved decay products (DDP) and dielectric dissipation factor (DDF), according to ASTM standards. A comparison is made between the performances of fresh and aged samples. The results provide experimental evidence that the chemical composition of hydrocarbon blend is contributing factors to oil gassing. It was observed that aged oils release more gases than new one. It was also observed that the gassing tendency increased with increasing amount of ester for the mixed fluids. The pressure and the absorbance of gases vary proportionally with ester content. Under thermal stress, an increase in pressure is observed especially for the mineral oil sample. The turbidity, DDP and DDF measurements revealed higher values for mineral oil. Importantly, the stability improved with increasing ester content in the blends. Mixed mineral oil/ester therefore offers many advantages with concomitant cost reductions compared with pure synthetic esters.

Combined Gas–Liquid Plasma Source for Nanoparticle Synthesis

A gas–liquid plasma source for the synthesis of colloidal nanoparticles by spark erosion of the electrode material was developed and allowed the particle synthesis regime to be varied over a wide range. The source parameters were analyzed in detail for the electrical discharge conditions in water. The temperature, particle concentration, and pressure in the discharge plasma were estimated based on spectroscopic analysis of the plasma. It was found that the plasma parameters did not change signifi cantly if the condenser capacitance was increased from 5 to 20 nF. Purging the electrode gap with argon reduced substantially the pressure and particle concentration. Signifi cant amounts of water decomposition products in addition to electrode elements were found in the plasma in all discharge regimes. This favored the synthesis of oxide nanoparticles.

Mechanism of the Accelerated Reduction of an Oxidized Metal Catalyst under Electric Discharge

AbstractThe front cover artwork for Issue 04/2016 is provided by the Korea Institute of Machinery and Materials and Chosun University. The image shows a novel reaction pathway for the reduction of metal oxide under electric discharge conditions where activated intermediate species desorb without further surface reaction and react with gas‐phase radicals. See the Communication itself at http://dx.doi.org/10.1002/cctc.201500865.

Initial Growth of Functional Plasma Polymer Nanofilms

To gain deeper insights into the initial growth mechanism, with respect to functional group density and cross-linking, plasma polymer films (PPFs) were deposited from C2H4/NH3 discharges. Keeping gas phase processes and electrical discharge conditions constant all over the deposition process, the mass deposition rate of the PPF was found to be initially lower and regularly increasing before reaching steady-state conditions after a film thickness of about 5 nm on metal oxide substrates. The first gradient nano-layer, i.e. the first 5 nm deposited, were observed to possess less amino functional groups and to be more cross-linked and thus more stable compared to the film prepared in steady state conditions, in which the uniform film comprises more amino functional groups, yet is less cross-linked and thus less stable. Due to its sticking probability, the substrate thus influences the initial deposition rate. Over plasma exposure time, the substrate becomes covered by an initial layer of PPF and the film-forming species are no longer deposited onto the pristine substrate but onto the already deposited organic polymer film. The preparation of the highly stable functional nanofilm, i.e. the initial PPF layer, can lead to new possible applications and fast deposition processes.

Improvement in Surface Characteristics by EDM with Chromium Powder Mixed Fluid

Surface finishing technology by EDM has recently progressed, and very small surface roughness can be readily obtained by controlling the electrical discharge conditions, or by using metal powder mixed working fluids. In addition, it was reported that EDMed surface using metal powder mixed fluids sometimes has high surface functions, such as high hardness, high corrosion resistance and so on. Therefore, the high functional EDM finished surface is well expected to be applied as a final metal mold surface. In this study, formation of chromium containing layer on the EDMed surface was tried by using chromium powder mixed fluid. Furthermore, the EDMed surface characteristics with chromium powder mixed fluid were experimentally evaluated.

Effect of machining area on material removal rate in strip EDM

Strip EDM is similar to wire EDM, except that the electrode is a roll of brass strip. In this study, investigated is the effect of machining area on material removal rate (MRR) in strip EDM, The MRR was measured according to different machining areas and different electrical discharge conditions. For a given discharge condition, optimal machining area for maximum MRR was identified. The optimal machining area was larger under higher discharge energy condition. It is shown that strip EDM is much more efficient than wire EDM because material removal rate is much higher and the electrode consumption is much less.

Study on Surface Characteristics of EDMed Surface with Nickel Powder Mixed Fluid

EDM finishing technology has progressed recently, and very small surface roughness can be obtained by controlling the electrical discharge conditions. Also, EDM using powder mixed fluids can improve the surface characteristics. Therefore, the EDM finished surface is highly expected to be applied as a final metal mold surface. In that case, the characteristics of EDMed surface influence the molding performance and the life of metal molds. As a new surface finishing method by EDM, the characteristics of EDMed surface using a nickel powder mixed fluid was experimentally discussed in this study, since nickel coatings have been widely applied to improve the corrosion resistance and the mold releasability of metal molds. Experimental analysis clarified that the resolidified layer containing nickel content could be formed on the surface by EDM in nickel powder mixed fluid. Also, the water repellency and the releasability of molded resin from the EDM finished surface could be improved.

Formation of Nanospheres and Nanorods of Titanium Dioxide in a Low-pressure Ar/O2 Plasma Controlled by a Sputtering Method

Formation of nanoparticles and nanorods of titanium dioxide (TiO2) in Ar/O2 plasma was investigated by controlling the discharge parameters, such as partial pressure and applied voltage. The nanostructures were produced by reactions of oxygen with titanium atoms, sputtered from a titanium target by reactive sputtering. The deposits were analysed by the SEM, TEM and EDX. Many nanospheres were observed on thin films composed of nanorods, deposited on a silicon substrate at an applied voltage from 1,500 to 3,000 V and a total pressure of 0.5 Torr with a deposition time of 1.5 h. These properties were nearly independent of the partial pressure ratio of oxygen to argon, The diameter of the nanospheres varied from 15 to 100 nm. The thin film quality was controllable by adjusting the electric discharge conditions.

S134012 ニッケル粉末混入放電加工面の表面特性に関する研究([S134]先進特殊加工技術)

Recently, EDM finishing technology has remarkably progressed, and very small surface roughness can be readily obtained by controlling the electrical discharge conditions. Also, EDM using powder mixed working fluids can improve the surface characteristics, such as wear resistance and corrosion resistance. Therefore, the EDM finished surface is well expected to be applied as a final metal mold surface in the near future. In that case, the surface characteristics of EDMed surface would influence the molding performance and the life of metal mold. As a new surface functionalization of EDMed surface, the surface characteristics of EDMed surface using a nickel powder mixed fluid is experimentally discussed in this study, since nickel coating has been widely applied to improve the corrosion resistance and the mold releasability of metal mold surface. Experimental analysis clarified that the resolidified layer containing nickel content could be formed on the surface by EDM in nickel powder mixed fluid. Also, the water repellency and the releasability of molded resin from the EDMed surface could be improved.

The Machining Characteristics of Insulating AlN Ceramics by EDM

AlN ceramic materials have high thermal conductivity and electrical insulation, prompting consideration of their use as a semiconducting material. Although AlN should be machined with a high accuracy of form and dimension to achieve products and components with requisite precision, mechanical and other machining methods such as the micro blasting technology or laser method cannot be used because of the brittleness and high thermal conductivity of AIN. Recently, we have succeeded in machining many insulating ceramics by EDM with the assisting electrode method. We have already machined many insulating ceramic materials such as Si3N4, ZrO2 and Al2O3. However, inferior machining characteristics were obtained with AlN than with other materials. In this study, the effects of several electrical discharge conditions were examined to obtain better machining properties, such as high material removal rate and a low electrode wear ratio. It was found that machining time decreased with an increase in capacitance, while the electrode wear ratio increased. In addition, the machining hole profiles were straight along the depth direction, and the shape of holes was non-tapered

Characteristics of Micro EDM for Insulating Aluminum Nitride Ceramics

Aluminum Nitride (AlN) ceramic materials have high thermal conductivity and electrical insulation, prompting consideration of their use as a semiconducting material. Although AlN should be machined with a high accuracy of form and dimension to achieve products and components with requisite precision, mechanical and other machining methods such as the laser method cannot be used because of the brittleness and high thermal conductivity of AIN. Recently, we have succeeded in machining many insulating ceramics by sinking (SEDM) and Wire-Electrical Discharge Machining (WEDM) with the assisting electrode method. We have already machined many insulating ceramic materials such as Si3N4, ZrO2 and Al2O3. However, inferior machining characteristics were obtained with AlN than with other materials. In this study, the effects of several electrical discharge conditions were examined to obtain better machining properties, such as high material removal rate and a low electrode wear ratio. It was found that machining time decreased with an increase in capacitance, while the electrode wear ratio increased. The electrode wear ratio of the W electrode was low, suggesting that it is suited for accurate machining of AlN. Additionally, the electrically conductive layer was analyzed using Energy Dispersive X-ray Spectrometry (EDS) and X-ray Diffraction (XRD). As a result, the architectural component of the EDMed AlN surface is considered mostly Al that is resolution of the workpiece. Therefore, in the EDM of AlN using the assisting electrode method, machinability using deionized water may be superior to dielectric oil. To investigate the effect of the dielectric working fluid, AlN was machined using deionized water and dielectric oil. In the case of machining with deionized water, the removal rate was faster and electrode wear ratio was lower, compared to dielectric oil.

Carbon in oxide layers formed under electric discharge conditions

The presence of carbon on the surface and in deep layers of oxide coatings produced by plasmaelectrolytic oxidation is studied. Graphite is found in the coatings formed on titanium under the conditions of cathodic polarization in an organic electrolyte. Carbon in the amount of 16–40 at % is present on the surface of coatings produced on aluminum at the anodic polarization in aqueous electrolytes. Compounds with C-O (oxidized carbon), C-C or C-H (aliphatic carbon), and C-M (carbide carbon) bonds are determined. The carbon content decreases to a few atomic percents upon etching the surface with a high-energy argon beam and removing a nearly 3-nm layer. Aliphatic and metal-oxide carbon is present at this depth. The carbon content on either the surface or in deep layers of the coatings is the same, regardless of the stage of the coating formation, namely, prespark, spark, or microarc anodizing.

Characterization of In-Flight Processing of Alumina Powder Using a DC-RF Hybrid Plasma Flow System at Constant Low Operating Power

The aim of this study is to provide the optimum operating conditions for enhancing in-flight alumina particle heating as much as possible for particle spheroidization and aggregation of melted particles using a DC-RF hybrid plasma flow system even at constant low operating power based on the thermofluid considerations. It is clarified that the swirl flow and higher operating pressure enhance the particle melting and aggregation of melted particles coupled with increasing gas temperature downstream of a plasma uniformly in the radial direction at constant electrical discharge conditions.

Optimizing the operation of an electrostatic precipitator by developing a multipoint electrode supplied by a hybrid generator

The authors investigated and improved the filtration efficiency of an electrostatic precipitator (ESP). A laboratory-scale pilot unit was developed to allow experimentation under conditions approaching those of the industrial ESPs used by the CEA at Marcoule (France). After elucidating the electrical phenomena and optically analysing the physical processes occurring inside the precipitator, a specific electrode was developed for use with a hybrid power supply. The experiments were based on analysing the variation over time of the electric charge injected into the particle separator, the particle mass collected at the ground electrode and the charges quantity measured on a grid in the airstream after the electrode unit. Photos were also taken under different electrical discharge conditions. The results show that combining a multipoint electrode and a hybrid generator (30 kV dc and 30 kV, 1 kHz) improves the process efficiency and significantly extends the time frame (more than 10 h) during which the process operates at optimum efficiency.