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1.1 ,This test method describes a steady state technique for the determination of the thermal conductivity, λ,, of homogeneous-opaque solids (see Notes 1 and 2). This test method is applicable to materials with effective thermal conductivities in the range 0.2 <, λ, <, 200 W/(m·,K) over the temperature range between 90 and 1300 K. It can be used outside these ranges with decreased accuracy.
Note 1—,For purposes of this technique, a system is homogeneous if the apparent thermal conductivity of the specimen, λ, A, does not vary with changes of thickness or cross-sectional area by more than ±,5 ,%. For composites or heterogeneous systems consisting of slabs or plates bonded together, the specimen should be more than 20 units wide and 20 units thick, respectively, where a unit is the thickness of the thickest slab or plate, so that diameter or length changes of one-half unit will affect the apparent λ,A by less than ±,5 ,%. For systems that are non-opaque or partially transparent in the infrared, the combined error due to inhomogeneity and photon transmission should be less than ±,5 ,%. Measurements on highly transparent solids must be accompanied with infrared absorption coefficient information, or the results must be reported as apparent thermal conductivity, λ,A.
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