Thermal conductivity versus depth profiling of inhomogeneous materials using the hot disc technique

Transient measurements of thermal conductivityare performed with hot disc sensors on samples having a thermal conductivityvariation adjacent to the sample surface. A modified computational approach is introduced, which provides a method of connecting the time-variable to a corresponding depth-position. This allows highly approximate—yet reproducible—estimations of the thermal conductivityvs. depth. Tests are made on samples incorporating different degrees of sharp structural defects at a certain depth position inside a sample. The proposed methodology opens up new possibilities to perform non- destructive testing; for instance, verifying thermal conductivityhomogeneity in a sample, or estimating the thickness of a deviating zone near the sample surface (such as a skin tumor), or testing for presence of other defects.