Infrared Imaging Methods for the Thermal Characterization of Materials

对当今广泛使用的材料的基本热性能进行可靠测量的需求不断减少。材料在各种条件下的导热系数、比热等的大小需要提供给计算机模型，这些模型已成为现代设计过程的基石。新材料需要进行原始性质测定，对许多长期使用的材料进行新的性质测定是可取的。对于电导率来说尤其如此，在特定的生产过程中，电导率会随着材料的特定成分和微观结构而发生很大的变化。******目前的提案旨在在此背景下开发专门为某些类型的这些先进材料的热性能表征设计的新方法。计划中的研究将以热成像技术为基础，热成像技术已成为该领域的一项成熟技术。事实证明，热成像技术很有吸引力，因为它允许对大表面进行非接触式实时温度传感。此外，由于现代成像仪的高灵敏度，在性质测定中使用的温度变化可以非常小。当需要对性能随温度变化很大的材料进行测量时，这一特性尤为重要。然而，热成像技术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。本提案的目标是解决这些问题。******我们的第一个目标是提出仪器解决方案，以摆脱红外成像仪有限的时间和空间分辨率，从而将热成像在热性能测量领域的应用范围扩大到其他类型的材料（即热快速材料，异质材料热性能空间变化的显微成像）。为了解决帧率问题，我们将研究电子频闪仪的解决方案。为了解决空间分辨率问题，将考虑使用超分辨率方法对软件进行改进。******我们的第二个目标是开发一种新的基于热成像的技术，用于高导电性材料的微观扩散率映射。该技术将标准闪光法与第一个物镜的结果结合起来。如今，这种测量的唯一选择是光反射显微镜，其设置复杂且无法用于低反射材料。******我们的第三个目标是探索脉冲相位热成像（PPT）作为众所周知的热波干涉测量（TWI）的替代方案。TWI是一种用于表征涂层和多层的标准技术。但是，对于低导电性材料来说，这是非常耗时的。PPT速度快，允许在频域处理数据，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.