The thermal conductivity of each material was measured on dry
20 20 5 cm3 half-cubic samples using a non-stationary method [18]. The nonstationary
method provided several measurement advantages in terms of the contact
resistance, power and duration of the emitted signal. The experimental device
was composed of a transient plane source (TPS) element, a power supply stabilised
in tension with a Wheatstone bridge, an acquisition power station and a microcomputer
for data control and processing. To protect the probe against damage and
ensure that the flow was distributed over a representative surface, two copper
plates with thicknesses of 1 mm and areas of 5 5 cm2 were introduced between
the TPS sensor and two 20 20 5 cm3 blocks composed of the same material.
The surfaces of the two half samples were polished beforehand to minimise the
influence of contact resistance. A chucking device was used to ensure good contact
between the various elements. The thermal conductivity was calculated directly by
a computer. Before testing, all specimens were kept in a hot air oven at 60 C until
they attained constant weight.