Plasmas are ionized gases containing free electrons, ions and excited neutrals. The charged particles can respond to external electric and magnetic fields and transport energy. A plasma can be created, for example, by striking a discharge between two electrodes; the ohmically heated plasma at temperatures more than 10,000 degrees can be ejected out, resulting in a 'plasma torch'. This torch can melt or vaporize any material. Plasma metallurgy, synthesis of ceramics, waste pyrolysis, etc. result from the high temperature gradients that aid in rapid quenching and selective reactions. In low-pressure'molecular gases, a different type of plasma referred to as 'nonequilibrium plasma', can be created by glow discharge. The electrons in this plasma have temperatures in the region of 10-50,000 degrees, whereas the ions and neutrals are left cold. One can use the resulting plasma for synthesis of thin films and for surface coatings and modification.
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