LFA 1000 – Multilayer sample – Thermal conductivity
Multilayer model – Thermal conductivity – thermal diffusivity
With the LFA it is also possible to measure samples with multiple layers, where two or three layers can be characterized. For that the software offers a multilayer evaluation tool, which can evaluate the properties of each single layer.
The measurement graph shows in blue a LFA measurement of the total thermal diffusivity of a multilayer sample, which consists of a substrate and an organic coating of about 60 µm. It shows a nearly constantly decreasing diffusivity within the temperature range between RT and 700°C.
In order to evaluate the thermal diffusivity of the coating using a differential approach, it is required to know the properties of the substrate, as well as thickness of the layer. The thermal diffusivity of the blank substrate can be determined in a separate run or sample holder position (when the sample robot is used). The orange curve shows the result of this evaluation – the thermal diffusivity of the coating, which has a significantly lower value compared to the measurement of the complete sample.
If the density and specific heat are available for the layer (could be measured using a Dilatometry as well as Differential Scanning Calorimetry), it is also possible to determine the thermal conductivity of the substrate and coating.