Thermal plasma processes for use in research and development

The chemical use of plasmas for various applications has gained more importance in recent years. Examples are large scale deposition, surface modification, chemical conversion and effluent gas treatment. The plasmas are characterised by very large energy density and a high degree of activation. As the energy is applied by DC, RF or microwave form and large flows are employed, plasmas can be varied on short time constants and the scale of the plasma process can be chosen to satisfy the demands of the particular application. The essential ingredient of plasmas are electrons, first to create the plasma itself and secondly to serve (with the ions) as the primary source of chemistry. As the electron temperature is high (in the eV range) the activation of the plasma medium is much larger than those achievable with thermal chemistry. Therefore plasma chemistry can proceed at much lower pressures and ambient temperatures than is common in normal thermal chemistry including catalysis. As the specific activation is high, large flows and short residence times can be employed and the inventory of chemically active particles at any moment can be relatively small. This means that plasma processing has significant advantages regarding safety of the process, chemical selectivity and that it is easier to satisfy environmental constraints.