Research On Heat Radiation Regulation Based On Ordered Micro-nano Structure

Thermal emission is a universal phenomenon in nature,which is,in essence,an object radiating electromagnetic waves and releasing energy outward due to its own temperature.In recent years,there has been a certain research foundation for thermal emission regulation based on micro-and nano-structures.At present,many applications have been realized including but not limited to the fields of thermoelectric conversion,infrared camouflage,and visible light.In this thesis,combining the ordered micro-and nano-structures with the refractory metal and the plasmonic metal,we designed and fabricated two kinds of thermal emitters applicated in the high-temperature and roomtemperature environments,achieving thermal emission regulation in near-infrared and mid-infrared bands,respectively.Aiming at these two kinds of thermal emitters,we carried out a series of studies on theoretical calculations,physical mechanism analysis,and experimental preparation.The details are as follows.(1)Thermal emitter based on refractory metal microstructures:In order to realize the selective emission for the thermal emitter in the thermophotovoltaic system,a twodimensional circular-hole array structure was designed on the surface of refractory metal.Through scanning calculation and iteration optimization of structural parameters,the ideal structural parameters were finally proposed.The results show that the optimized period is 1.4 μm,the hole depth is 3 μm and the hole diameter is 1 μm.Theoretically,this structure has a selective high emissivity in the waveband of 1-2 μm,with a value of more than 80%,and the emissivity decreases in the waveband after 2 μm,realizing selective emissivity regulation.The prepared nanostructured area on the surface of the emitter sample is 12×12 mm,and the hole depth is characterized as 3.4 μm.The emissivity of the thermal emitter in the wavelength range of 1～2 pm is about 80%,measured by the Fourier spectrometer.After 2μm,the emissivity of the band decreased in accordance with the theoretical calculation.(2)Intelligent infrared switch based on Al cross-slot structure:In order to realize the reception and cut-off function in the infrared band,we designed an intelligent infrared switch that can achieve transmittance regulation in the infrared band.We used the superposition of the aluminum frequency selective surface(Al-FSS)and the phasechange material VO2 layer,to form an intelligent infrared switching device at dynamic temperature,which can realize the high transmission in the infrared band at low temperature(e.g.,300K)and the cutoff at high temperature(e.g.,350K).After the optimized design,the structural parameters were obtained as follows:the period of Al cross hole is 5.5 μm,the length of Al cross hole is 4.5 μm,the width of Al cross hole is 1μm,the thickness of Al-FSS is 200 nm,the thickness of phase change material VO2 is 50 nm.It was found that the transmittance peak of the optimized intelligent infrared switch reaches 64.74%at 10.6μm at low temperature,and has good emissivity characteristics in greater angles;while at high temperature,the transmittance of all angles is less than 1%.We also used laser direct writing and pulsed laser deposition technology to prepare the square array of cross-slot intelligent infrared switches,the preparation area of which is 15×15 mm and has good scalability and wide applications.After the test of the prepared samples,the transmittance peak of the actual prepared infrared switch reached 37%at 10.6 μm,and the transmittance was cut off in all bands at high temperatures,realizing a good dynamic temperature control.