Study of the injection of liquid sprays into thermal plasmas has a number of important applications. Examples include Thermal Plasma Chemical Vapor Deposition (TPCVD), hazardous waste destruction and, ICP atomic emission or mass spectrometry in analytical chemistry. The spray is comprised of thousands of single liquid droplets. To calculate the mass, momentum and energy exchange between the gas and the spray, one must account for a distribution of droplet sizes, velocities, and temperatures. For some cases, droplet collision and breakup also are important. This paper developed a model for the transport and evaporation of liquid droplets sprayed into an radio frequency inductively coupled plasma (rf-ICP). The model considers the evolution of spray distribution function as the liquid spray travels through the discharge. Coupling calculations between plasma gas and water spray is performed for a typical rf-ICP torch. This model is capable of predicting the thermal and dynamic behavior of the liquid spray and its effects on the plasma gas for different rf-ICP operating conditions.

Nanopowders of amorphous SiO 2 , with typical particle sizes of 30-80 nm, were treated under non-equilibrium plasma conditions created by a capacitively coupled (CC) RF discharge in pure methane or ethane. The gas flow rate was varied between 0.02-0.06 slpm, with reactor pressures maintained between 1000 and 5000 Pa, and applied RF power inputs between 700 and 1500 W. The plasma properties were monitored through measurements of the C 2 rotational and the atomic hydrogen excitation temperatures. The compositions of the gases that passed through the plasma were analyzed by mass-spectrometry. In spite of the evidence indicating the presence of C n H 2n+2 and C n H 2n (n=1-3) species, as well as acetylene, in the discharge, the homogeneous formation of soot was not observed. At the same time, introduced nanoparticles acted as centers for the inception and growth of C:H thin coatings in the form of polymer-like hydrocarbon layers, whose thickness lay between < 5 - 30 nm. The results of TEM, IR spectroscopy, thermo-gravimetric and precision calorimetric analyses performed on the plasma treated powders provided evidence for the formation of an amorphous, high density C:H matrix on particles' surfaces.

By means of Schlieren photography, enthalpy probe, mass spectrometry and the particle measuring system DPV 2000 the influence of the internal and external anode nozzle and torch geometry, on plasma jet quality for atmospheric plasma spraying was investigated. It turned out that there is a strong geometrical effect of the inner contour and that with a proper expansion of the hot core of the plasma jet a considerable improvement of the melting and deposition quality can be obtained. Also the outer torch contour is of influence on the spray process because it controls the formation and the intensity of turbulence and the interaction of the plasma jet with its surrounding and hence the cold gas entrainment.

Plasma spraying of metals and metallic alloys performed in controlled atmosphere or soft vacuum results in coatings with a low oxidation level and excellent thermomechanical properties. Unfortunately, the spraying cost is drastically increased by one or two orders of magnitude compared to air plasma spraying (APS). Thus the minimisation of oxidation during APS is a key issue for the development of such coatings. Oxygen concentrations sucked into plasma jets have been measured by an enthalpy probe linked to a mass spectrometer. This technique allows to determine simultaneously plasma composition, temperature and velocity distributions within the plasma plume. Results have been compared to those obtained with a two-dimensional turbulent flow model. The obtained results have shown that surrounding air entrainment is reduced when using adequate Ar/H2/He mixtures which viscosity is higher than that of Ar/H, mixtures, limiting the turbulence in the jet fringes and pumping of the surrounding atmosphere.