Chemical Vapor Deposition
Chemical vapor deposition (CVD) may be defined as the deposition of a solid on a heated surface from a chemical reaction in the vapor phase. It is a versatile process suitable for the manufacturing of coatings, powders, fibers, and monolithic components. It is possible to produce most metals, metal oxides, and non-metallic elements such as carbon and silicon as a large number of compounds including carbides, nitrides, oxides, intermetallics, and many others. The main advantage of CVD is that the deposition rate is high and thick coatings or nanoparticles can be readily obtained. The process is generally competitive and, in some cases, more economical than the physical vapor deposition (PVD). Additionally, it is not restricted to a line of sight deposition, which is a general characteristic of sputtering, evaporation, and other PVD processes. However, two major areas of applications of CVD have rapidly developed the last 20 years or so, namely, in the semiconductor industry and in the metallurgical coating industry which includes cutting tool fabrication. Very recently, the CVD process has been given enormous attention owing to the possibility of mass production of monodisperse nanoscale powders; however, the mechanism of powder synthesis kinetics is still not clear.[43-46] Kim, Yu, and Lee[46] have synthesized nanosize TiO2 powders using CVD. Carbon nanotubes have also synthesized by CVD method using Fe-Mo nanoparticles.[47]
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