Infrared Imaging Methods for the Thermal Characterization of Materials

对当今使用的各种材料的基本热物性进行可靠测量的需求一直不减。材料在各种条件下的导热系数、比热等的大小被要求提供给计算机模型，而计算机模型已经成为现代设计过程的基础。新材料需要原始的性质测定，而许多长期使用的材料的性质的新测定是可取的。导电性尤其如此，在特定的生产过程中，材料中产生的特定成分和微结构可能会有很大的变化。在此背景下，当前的建议旨在开发专门为某些类型的这些先进材料的热性能表征而设计的新方法。计划中的研究将基于热成像，这已成为该领域的一项成熟技术。热成像技术已经被证明是有吸引力的，因为它允许实时非接触式地检测大面积表面的温度。此外，由于现代成像仪的高灵敏度，在属性确定中使用的温度变化可以非常小。当需要测量其性能随温度变化很大的材料时，该属性尤其重要。然而，热像仪仍然面临着一些障碍：帧速率有限，空间分辨率低，实验效果不佳。这项提议的目标旨在解决这些问题。*我们的第一个目标是提出一种仪器解决方案，以摆脱红外成像仪有限的时间和空间分辨率，从而将热成像技术在热物性测量领域的应用扩展到其他类型的材料(即，热速材料、对非均质材料热物性空间变化的微观成像)。为了解决帧速率问题，将研究一种电子频闪镜解决方案。为了解决空间分辨率问题，将考虑使用超分辨率方法改进软件。*我们的第二个目标是开发一种基于热成像的新技术，用于绘制高导电材料的微观扩散率图。这项技术将结合标准的闪光法和第一个目标的结果。如今，这种测量的唯一选择是光反射显微镜，其设置复杂，不适用于低反射材料。*我们的第三个目标是探索脉冲相位热成像(PPT)作为著名的热波干涉(TWI)的替代方法。TWI是用于表征涂层和多层膜的标准技术。然而，这是非常耗时的，特别是对于低电导率材料。PPT速度快，允许在频域进行数据处理，类似于TWI频率分析。

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.