Javad Mostaghimi

Plasma-particle interaction effects in induction plasma modeling under dense loading conditions

Abstract The injection of powders into an inductively coupled plasma is modeled. Attention is given to the plasma-particle interaction and its effect on plasma fields. It is demonstrated that for most applications, such interactions must be considered in any model. For the calculations, copper and alumina powders are used. The plasma gas is argon at atmospheric pressure.

Two-dimensional electromagnetic field effects in induction plasma modelling

Based on the electromagnetic vector potential representation, a two-dimensional, axisymmetric model is proposed for the calculation of the electromageetic fields in an inductively coupled, radiofrequency (r.f.) plasma. A comparative analysis made between the flow, temperature, and electromagnetic fields obtained using this model and those given by our earlier one-dimensional electromagnetic fields model show relatively little difference between the temperature fields predicted by the two models. Significant differences are observed, however, between the corresponding flow and electromagnetic fields. The new model offers an effective means of accounting for variations in the coil geometry on the flow and temperature fields in the discharge and for achieving a better representation of the electromagnetic fields under higher frequency conditions (f>10 MHz).

A two‐temperature model of the inductively coupled rf plasma

A two‐temperature model is proposed for the computation of the two‐dimensional flow and temperature fields in a rf inductively coupled plasma torch. The model is applicable to monatomic gases. The results obtained for an argon plasma indicate that, while at atmospheric conditions, deviations from local thermodynamic equilibrium (LTE) are relatively small, the situation is different under reduced pressure conditions, where substantial deviations from LTE have been noted, particularly in the energy addition region.

Heating of powders in an r.f. inductively coupled plasma under dense loading conditions

A study was carried out of the heating of powders in an r.f. inductively coupled plasma under dense loading conditions. The results obtained using a mathematical model taking into account plasma-particle interaction effects reveal an important cooling of the plasma caused by the presence of the particles. This, in turn, gave rise to a corresponding drop of the efficiency of the melting of the particles in the plasma. The effect is shown to depend strongly on the thermodynamic properties of the material of the powder.

Parametric study of the flow and temperature fields in an inductively coupled r. f. plasma torch

A theoretical investigation of the effect of different parameters on the flow and the temperature fields in a radiofrequency inductively coupled plasma is carried out. The parameters studied are: central injection gas flow rate, total gas flow rate, input power, and the type of plasma gas. The results obtained for argon and nitrogen plasmas at atmospheric pressure indicate that the flow and the temperature fields in the coil region, as well as the heat flux to the wall of the plasma confinement tube, are considerably altered by the changes in the torch operating conditions.

Effect of frequency on local thermodynamic equilibrium conditions in an inductively coupled argon plasma at atmospheric pressure

A theoretical investigation of the effect of induction frequency shows that deviations from local thermodynamic equilibrium (LTE) are strongly related to this parameter. Computations are carried out for an argon plasma at atmospheric pressure over the frequency range 3–40 MHz. Higher frequencies result in lower‐temperature levels in the torch, and also the difference between the electron and the atom/ion temperatures is increased. This is in agreement with the observations of other investigators. The results of the proposed model also show good agreement with the measured temperature profiles. Similar calculations, which are based on the LTE assumption, are reported and compared with the present non‐LTE model.

A turbulent flow model for the rf inductively coupled plasma

A mathematical representation is given for the turbulent fluid flow and energy transfer in an rf induction plasma. The flow and temperature fields are obtained through the solution of the two‐dimensional rotationally symmetric turbulent Navier–Stokes equations along with the energy and the one‐dimensional Maxwell’s equations for the electric and magnetic fields. The turbulent viscosity is determined using the standard k‐e model. Results are given for an argon plasma under atmospheric conditions. Different aspects of turbulent flows and their implications in rf plasmas are discussed. The results indicate the presence of both laminar and turbulent regimes in the same flow field. The effect of swirl in the plasma gas is to increase the overall turbulence level in the torch.

Computer modeling of the emission patterns for a spectrochemical ICP

Abstract A computer model has been developed for the calculation of the two-dimensional emission pattern from a spectrochemical ICP. Assuming local thermodynamic equilibrium (LTE), the flow, temperature and the concentration fields are computed. These are used to estimate the population density of different species present in the discharge, and accordingly the emission pattern for different atomic and ionic lines. Typical results are given for Li, Ca, Ni, Cu and Fe for an ICP torch operated at 500 and 750 W.

The induction plasma chemical reactor: Part I. Equilibrium model

A mathematical model is presented for the numerical simulation of the flow, temperature, and concentration fields in an rf plasma chemical reactor. The simulation is performed assuming chemical equilibrium. The extent of validity of this assumption is discussed. The system considered is the reaction of SiCl4 and NH3 for the production of Si3N4.

The induction plasma chemical reactor: Part II. Kinetic model

A kinetic model has been developed for the prediction of the concentration gelds in an rf plasma reactor. A sample calculation for a SiCl4/H2 system is then performed. The model considers the mixing processes along with the kinetics of seven reactions involving the decomposition of these reactants. The results obtained are compared to those assuming chemical equilibrium. The predictions indicate that an equilibrium assumption will result in lower predicted temperature fields in the reactor. Furthermore, for the chemical system considered here, while differences exist between the concentration fields obtained by the two models, the differences are not substantial.