Preparation And Thermal Radiation Spectral Properties Of The Microstructure Surface Functional Materials

Recently, great progress has been made in the investigation on the control of surface thermal radiation spectral properties using microstructure. Studies have shown that the thermal radiation will be quite different from macroscopic thermal radiation if the feature size of the substances is close to the thermal radiation wavelength, and the microstructure will exhibit good selection control on thermal radiation spectral properties. The basic method of controlling thermal radiation spectral properties by using microstructure is as follows:The microstructured surface of certain morphology is designed with proper material based on the spectral control requirements in the target wavelength band to achieve better energy transfer and spectral control of the thermal radiation. Therefore, there have many important applications for the microstructure spectral control on spacecraft thermal control technology, solar technology, manufacturing technology, materials industry and other fields. Perovskite manganese oxides based on thermochromic principle can be used as self-regulating thermal management materials on spacecraft due to their unique surface thermal radiation properties. However, due to the limitations of their inherent properties, the thermochromic effect of the materials is not so satisfied, which seriously affects their application in intelligent thermal control coatings on spacecraft. Solar photovoltaic cells which mainly take crystalline silicons as bases can be used in solar power, but currently there has a high cost and low efficiency problem. Therefore, how to improve the conversion efficiency of the solar photovoltaic cells so as to reduce the production cost is particularly vital. Based on this, this paper is aimed to study the thermal radiation spectral properties of the microstructure surfaces, and investigate the regulation of the microstructures on surface thermal radiation spectral properties of the function materials by fabricating microstructures on the surfaces of the perovskite manganese oxides and the monocrystalline silicons. There may have some useful guides for the engineering applications. This paper is focused on the following aspects.1. Preparation of one-and two-dimensional periodic structured surfaces of the thermochromic materialsThe bulk perovskite-type manganite thermochromic materials are prepared using solid state reaction method. The influences of preparation conditions, such as doping ratio and sintering temperature, on structures and properties of the thermochromic materials are investigated. Then, the structured surfaces of the thermochromic materials with one-dimensional gratings and two-dimensional cavity arrays are fabricated by means of the photolithographic technique, and the effects of fabricating processes on the properties of microstructure are studied. The structural parameters of the grating are as follows:the period10μm, the width of the grating groove6.0μm and the depth2.0μm. And the structural parameters of the cavity arrays are as follows:the period10μm, the diameter of the cavity6.0μm, and the depth2.0μm.2. Investigation on thermal radiation spectral properties of the thermochromic materials with one-and two-dimensional periodic structured surfacesThe optical properties of the thermochromic materials with one-and two-dimensional periodic structured surfaces are tested. Then the thermal radiation characteristics of the surfaces are obtained by calculation. The effects of one-dimensional gratings and two-dimensional cavity arrays structures on thermochromic effect of the perovskite-type manganese materials are studied to analyze the mechanisms of the effects. Testing results show that the thermal radiation properties of the structured surfaces with one-dimensional gratings and two-dimensional cavity arrays both increase markedly, and the thermochromic characteristic of La0.825Sr0.175MnO3is enhanced effectively.3. Preparation of three-dimensionally ordered macroporous (3DOM) thermochromic materialsThree-dimensionally ordered macroporous (3DOM) materials are typical three-dimensional photonic crystals. Three-dimensionally ordered macroporous (3DOM) perovskite-type manganese materials are prepared via colloidal crystal template method and the thermochromic functional materials with different apertures and different components are obtained by varying the experimental conditions. The influences of preparation conditions on structures and properties of the thermochromic materials are investigated. Experiment results show that the period of the3DOM thermochromic materials is well, and they all have formed the perovskite-type structure.4. Investigation on thermal radiation spectral properties of the thermochromic materials with three-dimensionally ordered macroporous (3DOM) structuresThe optical properties of the three-dimensionally ordered PS colloidal crystals are studied. Since the structures of the3DOM thermochromic materials are entirely inverse replications of the PS colloidal crystal templates and the performance of the three-dimensionally ordered PS colloidal crystals will directly affect the quality of the structures of the3DOM materials, it is so important to investigate the optical performance of the three-dimensionally ordered PS colloidal crystals. The optical properties of the perovskite-type manganese materials with different apertures and different components are tested. And the thermal radiation spectral properties of the thermochromic materials are obtained. Experiment results show that the PS colloidal crystals possess marked photonic band-gaps. The emittance of the3DOM materials increases markedly, but it has almost no thermochromic characteristic.5. Preparation and thermal radiation spectral properties of the structured surfaces of crystalline silicons (Si)With closely-packed monolayer PS colloidal crystals being used as masks, the structured surfaces of the crystalline silicons (Si) are constructed by using plasma etching (PE), inductively coupled plasma etching (ICP) and reactive ion etching (RIE) methods, respectively. The effects of the different etching processes on performance of the structured surfaces are investigated. The optical performances of the structured surfaces are tested to research the regulation on spectral properties of the microstructures. Experiment results show that it can obtain periodic microstructure on the crystalline silicon surfaces by using plasma etching method, but there has no periodic microstructure by using inductively coupled plasma etching and reactive ion etching methods. Optical testing results show that all the microstructure surfaces can effectively decrease the reflectivity of the crystalline silicon. Moreover, the antireflection effect of the periodic microstructure surfaces is much better than that of the disordered microstructure surfaces.