Search Results (6)

Thermal propagation events are characterized by fire and thick black smoke, leading to propagation methods with a focus on preventing heat transfer and optimizing gas flow. Yet little attention is being paid to the electric conductivity of the gas, leading to possibly unexpected battery casing openings due to lightning arcs as well as potentially providing the minimum ignition energy. This gas composition (omitting particles) was used at different temperatures and pressures in a lightning arc test bench, leading to the Paschen curve. Using a mini-module cell setup, filtered venting gas was flowed through another lightning arc test bench, allowing for in situ measurements. Full article

The breakdown of CF₃I gas at low pressure is of significant importance for applications in fields such as aerospace and microelectronics. However, the DC low-pressure breakdown characteristics of CF₃I remain underexplored. In this work, we utilize a one-dimensional implicit particle-in-cell/Monte Carlo collision (PIC/MCC) algorithm to investigate the complete DC breakdown process of low-pressure CF₃I. Our model accounts for ion–molecule collisions, recombination reactions, and external circuit influences. The breakdown process is delineated into three stages: before breakdown, breakdown, and after breakdown. In the before-breakdown stage, both the density and energy of particles are low. In the breakdown stage, the rapid increase in electron density and energy accelerates ionization reactions, leading to successful breakdown. The circuit behavior transitions from capacitive to resistive, sharing voltage with the external resistance. In the after-breakdown stage, continued positive ion growth leads to the formation of a thin anode sheath and a negative plasma potential. Energy production, including heating power and secondary electron emission (SEE) power, balances with energy loss through collision and boundary absorption. Specifically, 62% of the total heating power comes from positive ions, 1.5% from negative ions, and approximately 85% of electron energy is lost via boundary absorption. Finally, we compare the Paschen curves of CF₃I with those of SF₆, providing insights that are beneficial for the application of CF₃I as an SF₆ alternative. Full article

Electron impact scattering from C${}_3$F${}_6$O is studied in this work. The R-matrix method was used for the calculations of elastic, momentum transfer, and excitation cross sections. The attachment cross section was obtained through a parametric estimator based on the R-matrix outputs. The Binary-Encounter-Bethe (BEB) method was used for computing the ionization cross section. The obtained cross section set was used for the transport studies using the BOLSIG+ code, which is a two-term Boltzmann equation solver. The present calculation was performed for steady-state Townsend experimental conditions for E/N, covering a range of 100–1000 Td. The critical dielectric strength of pure C${}_3$F${}_6$O was found to be 475 Td, which is much greater than that of SF${}_6$ (355 Td). The effect of the addition of different buffer gases, such as CO${}_2$, N${}_2$, and O${}_2$, was also examined. For the C${}_3$F${}_6$O–CO${}_2$, C${}_3$F${}_6$O–N${}_2$, and C${}_3$F${}_6$O–O${}_2$ mixtures with 65%, 55%, and 60% C${}_3$F${}_6$O, respectively, the critical dielectric strength was determined to be essentially the same as that of pure SF${}_6$. The presence of synergism was confirmed for these gas mixtures. We further derived the Paschen curve using a fitting method with the transport parameters as the basic inputs. The minimum breakdown voltage of C${}_3$F${}_6$O accounted for only 55% of that of SF${}_6$. The buffer gas mixture improved the condition; however, the performance of CO${}_2$ and O${}_2$ mixtures was not satisfactory. The addition of N${}_2$ as the buffer gas significantly improved the breakdown property of the gas. The mixture of ≥99% of N${}_2$ or ≤1% of C${}_3$F${}_6$O gave a better breakdown characteristic than SF${}_6$. Any proportion ≥90% of N${}_2$ or ≤10% of C${}_3$F${}_6$O was suitable in the higher pressure ranges. The present work demonstrates the potential of C${}_3$F${}_6$O as a substitute gas for SF${}_6$ with a negligible environmental threat. Full article

This paper presents the simulation results for dielectric barrier discharge (DBD) at atmospheric pressure in argon gas for different relative permittivity, granule shape, thickness layer, and granule diameter measurements for starch on the breakdown voltage. DBD is commonly utilized to generate cold plasma for starch modification. The electric field was computed using COMSOL Multiphysics 5.3a software. The breakdown voltage was calculated employing Paschen’s law for this electric field. The voltage was found according to the breakdown criterion for gap distance 0.2–1.0 cm, and then the Paschen curve could be plotted. The results show that the top electrode of the plasma system may be replaced with the parallel plate electrode by a mesh electrode with a bigger mesh size to achieve a lower breakdown voltage. In addition, increasing the relative permittivity and decreasing the thickness layer can reduce the applied voltage for plasma formation. When compared to the sphere and ellipsoid shapes, starch with a polyhedral granule shape requires a significantly lower voltage for breakdown. The starch granule diameter does not affect the breakdown voltage. These findings can be utilized to determine the optimal breakdown voltage for each type of starch modification, contributing to the construction of a high-efficiency plasma production system for starch modification. Full article

An experimental study was performed on a low-density plasma discharge using two different configurations of the plasma cell cathode, namely, the one mesh system electrodes (OMSE) and the one mesh and three system electrodes (OMTSE), to determine the electrical characteristics of the plasma such as current–voltage characteristics, breakdown voltage (V_B), Paschen curves, current density (J), cathode fall thickness (d_c), and electron density of the treated sample. The influence of the electrical characteristics of the plasma fluid in the cathode fall region for different cathode configuration cells (OMSE and OMTSE) on the performance quality of a surgical gown was studied to determine surface modification, treatment efficiency, exposure time, wettability property, and mechanical properties. Over a very short exposure time, the treatment efficiency for the surgical gown surface of plasma over the mesh cathode at a distance equivalent to the cathode fall distance d_c values of the OMTSE and for OMSE reached a maximum. The wettability property decreased from 90 to 40% for OMTSE over a 180 s exposure time and decreased from 90 to 10% for OMSE over a 160 s exposure time. The mechanisms of each stage of surgical gown treatment by plasma are described. In this study, the mechanical properties of the untreated and treated surgical gown samples such as the tensile strength and elongation percentage, ultimate tensile strength, yield strength, strain hardening, resilience, toughness, and fracture (breaking) point were studied. Plasma had a more positive effect on the mechanical properties of the OMSE reactor than those of the OMTSE reactor. Full article

Micro plasma devices (MPD) with power gains are of interest in applications involving operations in the presence of ionizing radiations, in propulsion, in control, amplification of high power electromagnetic waves, and in metamaterials for energy management. Here, we review and discuss MPDs with an emphasis on new architectures that have evolved during the past seven years. Devices with programmable impact ionization rates and programmable boundaries are developed to control the plasma ignition voltage and current to achieve power gain. Plasma devices with 1–10 μm gaps are shown to operate in the sub-Paschen regime in atmospheric pressures where ion-assisted field emission results in a breakdown voltage that linearly depends on the gap distance in contrast to the exponential dependence dictated by the Paschen curve. Small gap devices offer higher operation frequencies at low operation voltages with applications in metamaterial skins for energy management and in harsh environment inside nuclear reactors and in space. In addition to analog plasma devices, logic gates, digital circuits, and distributed amplifiers are also discussed. Full article