Carbon high thermal conductivity

Silicon Carbide. Sihcon carbide is made by the electrofusion of siUca sand and carbon. SiUcon carbide is hard, abrasion resistant, and has a high thermal conductivity. It is relatively stable but has a tendency to oxidize above 1400°C. The siUca thus formed affords some protection against further oxidation (see Carbides). 

Carbon—graphite materials do not gall or weld even when mbbed under excessive load and speed. Early carbon materials contained metal fillers to provide strength and high thermal conductivity, but these desirable properties can now be obtained ia tme carboa—graphite materials that completely eliminate the galling teadeacy and other disadvantages of metals. 

Edie, D. D., Robinson, K. E., Fleurot, O., Jones, S. P. and Fain, C. C., High thermal conductivity ribbon fibers from naphthalene-based mesophase. Carbon, 1994, 32(6), 1045 1054. 

Duffy, D.R., Ting, J.-M., Guth, J.R. and Lake, M.L., Carbon fiber reinforced lightweight composites with ultra high thermal conductivities, Proc. Int. JEPC, Atlanta, GA, Sept., 1994, pp. 442 448. 

Ting, J.M. and Lake, M.L., Vapor grown carbon fiber reinforced aluminum composites with very high thermal conductivity J. Mat. Res., 1995, 10(2), 247 250. 

The mechanisms described above tell us how heat travels in systems, but we are also interested in its rate of transfer. The most common way to describe the heat transfer rate is through the use of thermal conductivity coefficients, which define how quickly heat will travel per unit length (or area for convection processes). Every material has a characteristic thermal conductivity coefficient. Metals have high thermal conductivities, while polymers generally exhibit low thermal conductivities. One interesting application of thermal conductivity is the utilization of calcium carbonate in blown film processing. Calcium carbonate is added to a polyethylene resin to increase the heat transfer rate from the melt to the air surrounding the bubble. Without the calcium carbonate, the resin cools much more slowly and production rates are decreased. 

Next generation machines will impose increasingly greater thermal loads on their PFCs. High thermal conductivity CFC materials may offer a solution to the high-heat loads, but further research is needed to overcome the problems noted above and to assure the place of carbon materials in future fusion power reactors. 

A pure form of sp3 hybridized carbon is known as diamond and this may also be synthesized at the nanoscale via detonation processing. Depending on their sizes, these are classified as nanocrystalline diamond (10 nm 100 nm), ultrananocrystalline diamond (< 10 nm) and diamondoids (hydrogenated molecules, 1 nm-2 nm). Nanodiamond exhibits low electron mobility, high thermal conductivity and its transparency allows spectro-electrochemistry [20,21]. However, ultrananocrystalline diamond exhibits poor electron mobility, poor thermal conductivity and redox activity [21,22]. 

To ease the dissipation of thermal flow, it is worthwhile to use dissipative additives such as ceramics, metal powders or carbon fibres that have a high thermal conductivity. 

Graphite is used widely in process plants for its high thermal conductivity (about six times that of stainless steel). Typical properties of impregnated carbon and graphite are given in Table 3.39. 

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