Biomimetic Superhydrophobic Surface Fabrication by Plasma Processing - Biomimetic Architectures by Plasma Processing - page 158

Figure 5.5 Four states of matter.

Most of the matter in the known universe exists as plasma.
Examples of them are the inner region and the atmosphere of the
stars, the solar corona, the solar wind, and the nebula. On Earth,
lightning is the most common natural plasma that is caused by
ionisation of particles in the Earth's atmosphere [23]. Artificial
plasmas can also be generated by applying enough energy to
the gas. Fridman stated that “plasma offers three major features
that are attractive for applications in chemistry and related
disciplines: (i) temperatures of at least some plasma components
and energy density can significantly exceed those in conventional
chemical technologies, (ii) plasmas are able to produce very high
concentrations of energetic and chemically active species (e.g.,
electrons, ions, atoms and radicals, excited states, and different
wavelength photons), and (iii) plasma systems can essentially be
far from thermodynamic equilibrium, providing extremely high
concentrations of the chemically active species and keeping bulk
temperature as low as room temperature. These plasma features
permit significant intensification of traditional chemical processes,
essential increase of their efficiency, and often successful stimulation
of chemical reactions impossible in conventional chemistry” [24].
Plasma generated in laboratory and industry can be generally
categorised in several ways as shown in Table 5.1.
Plasmas are typically obtained when gases are excited into
energetic states by an electrical source, such as, direct current, radio
frequency, or microwave. Several gases such as He, Ar, O

, N , NH ,

2 2 3

and CF , as well as mixtures such as air can be selected to initiate

a wide assortment of effects. Examples of the type of plasma gases,
along with their effects for the surface treatment, are given in
Table 5.2 [25].

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