Kinetics of the processes in a nitrogen plasma flow with carbon admixture

The evolution of the kinetics of plasma moving from the outlet of a plasma torch to the object of impact is studied in order to study the effectiveness of action of a nitrogen plasma flow on graphite surfaces. The motion is accompanied by a decrease in temperature from $10$ to $7$ kK with a loss of $\sim60\%$ of the input energy and an increase in the density of carbon-containing admixtures with partial conservation of the local thermodynamic equilibrium. The main reactions are the thermal processes of the formation and dissociation of molecules, the dissociative recombination and recharge of nitrogen ions, and, in the presence of carbon admixtures, the substitution reaction $\rm C + \rm N_2 \leftrightarrow \rm CN + \rm N$, the electron-collisional processes of stepwise ionization and recombination, and the entire ionic–molecular cascade of recharges and substitutions. It was found that a small amount of carbon impurity $(\sim0.1\%)$ manifests itself only in ionic–molecular kinetics. It increases the electron concentration, determines the ionic composition of the plasma, and thereby violates the equilibrium between its neutral and charged components. This leads, in particular, to a recombination nonequilibrium distribution of carbon atoms over the electron states. Other carbon-containing impurities $(\rm CN$ and $\rm C_2)$ are insignificant.