Speaker
Description
Phase-change materials (PCMs) and PCM-based metamaterials represent an emerging field of research. These materials can change their infrared emissivity under external stimuli such as applied electric current, mechanical strain, or optical laser pulses. Owing to this ability, they find applications in various industries, from novel building materials and fabrics to drug delivery, solar panel design, and special applications. Research in the literature usually focuses on material fabrication, growth, and laboratory characterization. Such studies make it possible to optimize material design to achieve the largest possible IR emissivity switching range, which is not always the most cost-effective solution.
However, these studies do not address what emissivity ranges are actually needed to manage the thermal contrast of typical PCM-covered ground objects in various real-world scenarios. In such scenarios, the apparent temperature of PCM-covered surfaces and their thermal contrast with the background are significantly affected by weather conditions (insolation, cloud cover, ambient air temperature, humidity, time of day, season, etc.).
Thus, the goals of this work were twofold: to investigate the influence of weather and scene factors on the apparent thermal contrast of PCM-covered surfaces with varying infrared emissivity, and to estimate the effect of this contrast variation on the detection range of ground objects.
We simulated the relative change in the maximum detection range (MDR) of such objects caused by changes in their apparent thermal contrast, using the Johnson criteria [1]. Our results showed that a tenfold decrease in the contrast value reduces the MDR by approximately one third. Since these calculations assume a uniform background temperature, they can serve as an upper-bound estimate, while real background clutter would further degrade the MDR.
We also systematized field measurement data available in the literature on the thermal dynamics of typical European landscapes in winter and summer. This allowed us to estimate the temperature swings of typical background objects (such as soil, asphalt, tree canopy, grass, rocks, snow, and ice) over the diurnal cycle in different seasons. On this basis, we estimated which IR emissivity switching ranges would be sufficient for thermal contrast management of PCM-covered ground objects with different intrinsic temperatures.
By combining the obtained data, we systematized the requirements for the design of novel PCMs for various thermal contrast management applications.
Acknowledgments. This work was partially supported by the National Academy of Sciences of Ukraine (projects #0125U000799 and III-10-24).
References
- Ye.O. Melezhyk, Z.F. Tsybrii, V.V. Zabudsky et al., Numerical estimations of the maximal distance of target detection in the IR spectrum with decreasing the target–background temperature contrast // Semiconductor Physics, Quantum Electronics & Optoelectronics, 2024, V. 27, No. 4, P. 397–403.