Pyrolytic graphite as a coating

Although, as mentioned above, pyrolytic graphite is used by itself as free-standing structures such as crucibles or rocket nozzles (see Sec. 4.0), its major use is in the form of coatings on substrates such as molded graphite, carbon foam, carbon fibers, metals, and ceramics. 

Composite Nature of Coatings. The surfaces of many materials exposed to the environment are prone to the effects of abrasion, corrosion, radiation, electrical or magnetic fields, and other conditions. These surfaces must have the ability to withstand these environmental conditions and/or provide certain desirable properties such as reflectivity, semiconductivity, high thermal conductivity, or erosion resistance. 

To obtain these desirable surface properties, a coating is deposited on the bulk material to form a composite in which bulk and surface properties may be very different.  

Mechanical Wear Friction Hardness Adhesion Toughness 

Porosity Surface area Pore size Pore volume 

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