With the LFA, it is also possible to measure samples with several layers, whereby two or three layers can be characterised. For this purpose, the software offers a multi-layer tool that can analyse the properties of the individual layers.
The graph above shows in blue an LFA measurement of the thermal diffusivity of a multilayer sample consisting of a substrate and a coating of approx. 60 µm. It shows an almost constant decrease in diffusivity with temperature. The measurement of the complete sample was then analysed using the multilayer tool. To do this, it is necessary to know the thickness of both the substrate and the coating. In addition, the thermal diffusivity of the substrate must also be specified or measured. By knowing other properties of the individual layers, namely the density and the specific heat, it is also possible to determine the thermal conductivity of both layers (substrate, coating). The orange-coloured curve shows the result of this evaluation – the thermal diffusivity of the coating, which has a significantly lower thermal diffusivity than can be seen when measuring the complete sample.
