| Summary: | 碩士 === 逢甲大學 === 纖維與複合材料學系 === 106 === In this study, tungsten oxide nanoparticles with different oxygen ratios and crystallinity were synthesized by using sol-gel method and calcination. The microstructure of nanoparticles were investigated to reveal the influences of oxidant and calcination on the microstructure and radiation absorption properties of obtained tungsten oxide. These various tungsten oxide nanoparticles were composited into a polyurethane matrix as a function additives to produce the thermal radiation shielding WO3-x / DPU films.
First, tungsten oxide nanoparticles with different oxygen ratios were synthesized by adjusting the amount of oxidant for sol-gel process. Half of synthesized nanoparticles were calcined. The XRD and TEM analysis shows that increasing the concentration of oxidants enhances the crystallinity of nanoparticles. The XPS analysis results shows that the oxygen ratio affects the fractions of W6+, W5+, and W4+ configurations in tungsten oxide powder and causes the apparent color difference. The increase of oxidant concentration gradually shifts the particle color from dark blue to yellowish green. The average particle size of D95 of WO3-x (3M) was 269.93 nm.
In the second part, tungsten oxide powders were composed into polyurethane. The composite films were sliding formed. The FTIR spectra evident the powder and matrix are physically mixed. The apparent color of composite films also reflects the powder colors.
Through the UV-Vis-NIR transmittance spectra, it was found that the tungsten oxide contained composite film show excellent near-infrared shielding ratio. The sample of CWO3-x(0.5M)/DPU-5wt%, exhibits a maximum shielding ratio 95.06% for 940 nm wavelength. It also perform a maximum temperature rise 33 ̊C under the halogen lamp illumination, and a maximum temperature rise 59.1 ̊C under the near-infrared lamp illumination. The measured thermal conductivity coefficient per unit thickness value was found to be 162.0 mWm-1K-1, the thermal diffusion value was 0.105 mm2/s, the thermal absorption value was 1530.6 Ws1/2/m2K, and the thermal resistance value was 26.6 m2mK/W.
The tungsten oxide composite film prepared in this study exhibits a photothermalysis and visible-near-IR shielding properties. These reveals its potential to be applied to solar receivers to improve their reception efficiency and used as an infrared ray absorbing material, heat-insulating affixing material, glass affixing material for automobiles or buildings, military, indoor, industrial, transportation, and other functional textiles or related products.
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