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Composition of species is one of the key parameters in calculating the plasma properties and assessing the plasma chemical processes. Unlike the calculation of LTE plasma composition, the calculation of 2T plasma composition still remains in dispute. Different researchers have chosen different methods which lead to different results. In this work, we compare two kinds of methods for calculating 2T plasma composition: the mass action law methods and extremum searching methods. The former methods include the two described by Potapov and van de Sanden et al mass action laws, respectively. The latter methods include those of searching minimum Gibbs free energy and maximum entropy of a plasma system respectively. The entropy maximization method is first reported in this work and has the same power as the commonly used Gibbs free energy minimization method. We demonstrate both mathematically and numerically that the method of 2T Gibbs free minimization is completely the same as the 2T Potapov mass action law, and the method of 2T entropy maximization is exactly consistent with the 2T van de Sanden et al mass action law if we assume that the term μi/Ti is independent of the number density ni. It is also found that the assumption of number density-independent μi/Ti mainly affects the density of charged particles. When the plasma reaches the LTE state, the composition obtained by the methods of entropy maximization with and without this assumption will be exactly the same. [ABSTRACT FROM AUTHOR]

The assumption of gaseous species is not always valid in non-LTE plasmas. This requires the consideration of condensed phases in the determination of plasma composition. In this work, we compare two methods for calculating 2T multi-phase plasma composition: the Gibbs free energy minimization method and the entropy maximization method. The latter method is first reported in this work and has the same power as the former method for the calculation of 2T plasma composition taking into account condensed species. Based on these two methods, we present a case study of the multi-phase compositions of N2–Cu, CO2–Cu, and C2F4–Cu plasmas. It is found that the 2T entropy maximization method is less sensitive to the non-equilibrium degree than the 2T Gibbs free energy minimization method. This leads to the large difference between the composition predicted by the two methods, for example, in the phase transition temperature. The case study shows that due to the high electron temperature at large non-equilibrium degree, the ionic species (e.g. Cu+ and C+) can be generated directly from the condensed species (e.g CuF2, Cu2O, Cu, and C). Such ionization does not occur if the copper proportion is very low (e.g only 1%). [ABSTRACT FROM AUTHOR]

Perfluoroketone (PFK) gases are widely used in industry, e.g. as an insulating medium in high-voltage apparatus and as a cleaning agent in chemical vapor deposition (CVD) chambers. A great deal of attention has been paid to them recently because of their low global warming potential (GWP). In order to describe the ionization processes in various plasmas resulting from PFK gases, the electron-impact ionization cross sections (Qion) of PFK molecules CxF2xO (x = 1–5) were calculated by the Binary-Encounter Bethe (BEB) and the Deutsch-Märk (DM) methods. The chemical structures of PFK molecules were optimized by the hybrid Density Functional Theory (DFT) method with the Austin-Petersson-Frisch functional including dispersion (APF-D). The binding and kinetic energies of electrons in molecular orbitals were also determined with the APF-D hybrid DFT method. The binding energies of valence electrons were then improved by the electron propagator theory (EPT) method. The ionization potentials of PFK molecules were calculated as the difference between the energy of a molecule and its cation using the complete basis set (CBS) method. The molecular orbital compositions were obtained by the natural atomic orbital (NAO) analysis. The results show that Qion determined by the BEB method are always larger than those by the DM method. The difference is reduced with the EPT corrections considered. The comparison between the theoretical and experimental Qion demonstrates that the EPT correction improves Qion considerably. [ABSTRACT FROM AUTHOR]

This paper is devoted to the calculation of fundamental properties of CO2 mixed with C2F4. The species composition and thermodynamic properties (mass density, entropy, enthalpy and specific heat at constant pressure) are based on Gibbs free energy minimization. The transport properties (electrical conductivity, viscosity and thermal conductivity) are calculated by the well-known Chapman-Enskog method. The Lennard-Jones like phenomenological potential and some recently updated transport cross sections are adopted to obtain collision integrals. The calculation is developed in the temperature range between 300 and 30 000 K, for a pressure between 1 to 16 bar and for several C2F4 proportions. Transport coefficients for CO2 are also compared with previous published values, and the reasons for discrepancies are analyzed. The results obtained for CO2–C2F4 mixtures provide reliable reference data for the simulation of switching arcs in CO2 circuit breakers with the ablation of PTFE. [ABSTRACT FROM AUTHOR]

The dielectric breakdown properties of hot SF6 gas during the dielectric recovery phase play an important role in understanding gas breakdown occurring in high-voltage circuit breakers. This paper is devoted to the theoretical investigation of dielectric breakdown properties of hot SF6 gas contaminated by copper at temperatures of 300–3500 K and pressures of 0.01–1.6 MPa. The equilibrium compositions of SF6–Cu mixtures are obtained with the consideration of condensed species. The unknown ionization cross sections for CuS, CuF and CuF2 are calculated using a Deutsch–Märk (DM) formalism based on quantum chemistry. The two-term Boltzmann equation is adopted to numerically calculate the electron energy distribution function, collision ionization coefficient and electron attachment coefficient. Then the reduced critical electric field strength is determined when the effective ionization coefficient equals to zero. The influences of the Cu proportion and gas pressure on the dielectric breakdown properties are investigated. It is shown that the existence of copper compounds increases the concentration of high-energy electrons significantly, even for the case with a very low percentage (e.g. 1% Cu). With the increase of copper content, the value of (E/N)cr is reduced remarkably at temperatures below 3000 K, but enhanced slightly above 3000 K. It is also found that the increase of pressure can improve the dielectric breakdown performance of hot SF6–Cu mixtures. [ABSTRACT FROM AUTHOR]

The equilibrium compositions and thermodynamic properties of SF6–Cu mixtures with copper proportions up to 50% are calculated as a function of temperature from 300 to 30 000 K and pressure from 0.01 to 1.0 MPa. The condensed phases and Debye–Hückel corrections are both taken into account. The influences of condensed phases, Debye–Hückel corrections, copper proportions and gas pressures on the composition and/or thermodynamic properties are discussed in detail under various conditions. Some results are tabulated for the modelling of SF6 arc plasmas contaminated by Cu. [ABSTRACT FROM AUTHOR]

The transport coefficients (including electrical conductivity, viscosity and thermal conductivity) of SF6-Cu mixtures with copper proportions up to 50% are calculated as a function of temperature from 300 to 30,000 K and pressure from 0.01 to 1.0 MPa. The Lennard–Jones like phenomenological potential and some recently updated transport cross sections are adopted to obtain collision integrals. The influence of copper proportion and gas pressure on transport coefficients under various conditions are discussed in detail. Some results are tabulated for the modeling of SF6 arc plasmas contaminated by Cu. [ABSTRACT FROM AUTHOR]