NOVEL RESULTS ON THERMAL-DIFFUSIVITY MEASUREMENTS ON ANISOTROPIC MATERIALS USING PHOTOTHERMAL METHODS

We have applied two photothermal techniques (infrared radiometry and m irage) and conventional procedures to measure the thermal diffusivity of a highly anisotropic sample of pyrolytic graphite. Unexpected and s trongly differing results are obtained with each technique. A theoreti cal analysis indicates that whereas the mirage technique gives a measu re of the elements of the thermal diffusivity tenser, infrared radiome try yields the elements of another thermal magnitude represented by th e inverse of this tensor. (C) 1995 American Institute of Physics.