1.2 Plasma Generation and Application

Plasmas are more or less ionized gases, often referred to as the fourth state of matter. They can be generated by a number of methods, such as combustion, flames, electrically heated furnaces, electric discharges (glow discharge, corona discharge, dielectric barrier discharge, arc discharge, microwave discharge, and radio frequency discharge), and shocks (electrically, magnetically, and chemically driven)[1-2]. Electric discharge plasmas are mostly used for laboratory and industrial applications and are created by applying direct or alternating high voltage to a gas or a gas mixture. This is generally referred to as gas discharge plasmas. Depending on the energy level, the gas discharge plasmas can also be classified into two categories: thermal and non-thermal plasmas[2-3]. In thermal plasmas, the temperatures of the plasma components approach thermal equilibrium, which is why these plasmas are often referred to as equilibrium plasmas. On the other hand, in non-thermal plasmas, also referred to as nonequilibrium plasmas, the temperatures of the plasma components are not the same and electrons often have much greater temperatures than the other gas components. Thermal plasmas are generated in conventional electric arcs or plasma torches. Nonthermal plasmas are generated in conventional glow discharge, dielectric barrier discharge, corona discharge, gliding arc discharge, and microdischarge[1-5].