Infrared Imaging Methods for the Thermal Characterization of Materials

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There is an undiminishing demand for reliable measurements of the basic thermal properties of the vast range of materials in use today. The magnitudes of thermal conductivity, specific heat etc. of materials subjected to all manner of conditions are required to feed the computer models that have become the bed-rock of the modern design process. Original property determinations are required for new materials and new determinations of the properties of many of the long used materials are known to be advisable. This is particularly true for conductivity which can vary considerably with the particular composition and microstructure produced in a material during a specific production process.******The current proposal aims in this context to develop new methods specifically designed for the thermal property characterization of some types of these advanced materials. Planned research will be based on thermography, which has become a well-established technique in this field. Thermography has proved attractive because it allows non-contact temperature sensing of large surfaces in real-time. Moreover, the temperature changes employed in a property determination can be very small because of the high sensitivity of modern imagers. This attribute is particularly important where measurements are needed for a material whose properties vary significantly with temperature. Nevertheless, thermography still faces some obstacles: limited frame rate, low spatial resolution, ineffective experiments. The objectives of this proposal are oriented to solve these issues.******Our first objective is to propose instrumentation solutions to get rid of the limited temporal and spatial resolution of IR imagers and thereby widen the use of thermography in the field of thermal property measurement to other types of materials (i.e. thermally fast materials, microscopic imaging of the spatial variation of thermal properties across heterogeneous materials). To solve the frame rate issue, an electronic stroboscope solution will be investigated. To solve the spatial resolution issue, software improvements with super resolution methods will be considered.******Our second objective is to develop a new thermography based technique for the microscopic diffusivity mapping of highly conductive materials. The technique will combine the standard flash method with the outcome of the first objective. Nowadays, the only option for such measurement is Photoreflectance Microscopy whose setup is complex and fails for low reflective materials.******Our third objective is to explore Pulsed Phase Thermography (PPT) as an alternative to the well-known Thermal Wave Interferometry (TWI). TWI is a standard technique used for the characterization of coatings and multi-layers. However, it is very time consuming especially for low conductivity materials. PPT is fast and allows data processing in the frequency domain, similar to TWI frequency analysis.