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Effective conductivity of polycrystalline graphite

1993; Elsevier BV; Volume: 31; Issue: 6 Linguagem: Inglês

10.1016/0008-6223(93)90197-i

1873-3891

D. F. Pedraza, P. G. Klemens,

Thermal properties of materials

An effective conductivity (thermal or electrical) is derived for polycrystalline graphite using a very simple approach. The material is modeled as a series of links and junctions, the former representing the crystallies and the latter the intercrystallite region. The large anisotropy of the principal conductivities permits definition of an excluded region in which conduction contributes negligibly to the overall thermal/electrical transport. Two approximations are obtained for the value of the excluded region, which depend not only upon the principal conductivities ratio, but also upon the crystallite shape anisotropy. This model allows estimation of the effective conductivity of polycrystalline graphite from a knowledge of the principal conductivities ratio, the conductivity along the graphite basal plane, the microstructural features (crystallite shape and size, number, and geometry of intercrystallite contacts per crystallite), and the density. Applications to nuclear-grade graphites gave satisfactory agreement with experimentally measured electrical and thermal conductivities.