| Abstract:Energy-saving and emission reduction have become the theme of the Times. Transparent heat-insulating materials for windows with high performance are welcomed greatly. They must be characterized by high visible light transpancy and strong near-infrared rays absorption/reflection. Research on novel high transparent and heat-insulating materials for windows on theoretical and experimental basis has become an important research topic in today’s world. So far, most of researchers focus on the preparation and application of them, but there is very few theoretical study. It is necessary for researchers to accelerate the research process by combining theoretical studies and experimental designs. In this thesis, on the theoretical side, the electronic structure of several transparent and heat-insulating materials for windows were investigated using the first-principles method, and optical performance of different kinds of films made of these materials had been predicted in theory. Experimentally, nano-LaB6ethnol dispersion with excellent stability and dispersion was prepared, and its optical performance had been examined. The main research contents and achievements are listed as following:Firstly, the geometry, electronic structures and optical properties of rare earth hexaborides RB6(R=Sc, Y and La) were studied using the first-principle density function theory. The electronic structures of three compounds demonstrate that these compounds are all metallic conductor materials. The upmost valence bands and the bottommost conduction bands of RB6(R=Sc, Y and La) are mainly composed of B-2p states and metal R-nd(n=3,4,5) states, respectively. And as atomic radius and e-layer of metal R increase, conduction bands move away from the Fermi energy level. The optical properties of RB6(R=Sc, Y and La) were also investigated by calculating and analyzing their dielectric functions, absorption spectra, reflectivity and energy-loss spectra in details, and optical performance of their different films was analyzed theoretically. The results show that YB6and LaB6can be used as high transparent and heat-insulating materials with high performance for windows, but ScB6is not. That LaB6can be transparent to the visible light may be ascribed to a collective oscillation (volume plasmon) of carrier electrons and strong optical absorption for the near infrared (NIR) wavelength may be attributed to dipole mode of plasma oscillation. These findings provide theoretical data for the application of three rare earth hexaborides, and it is greatly important to extend their potential field of application.Secondly, the electronic structures, magnetic and optical properties of RB6(R=Ce, Pr, Nd, Sm, Eu, Gd, Er, Tm, Yb and Lu) had been investigated. The results show that RB6(R=Ce, Pr, Nd, Sm, Eu, Gd, Er and Tm) are all ferromagnetic materials, but YbB6and LuB6are non-ferromagnetic materials. The electronic properties of ten compounds RB6are determined mainly by metal R. Optical properties of them show that they all have high reflectivity in the low-energy infrared region and have weak volume plasmon. GdB6and LuB6are suitable for transparent and heat-insulating materials for windows, but RB6(R=Ce, Pr, Nd, Sm, Eu, Er, Tm and Yb) are not.Thirdly, the electronic structures and optical properties of TiN had been investigated. The calculations show that TiN is conductor. The valence bands and the conduction bands of TiN are mainly composed of N-2p states and Ti-3d states, respectively. The results of optical performance of TiN films indicate it has the character of high visible light transparency and strong absorbance/reflectivity in the near-infrared region.Fourthly, the electronic structures and optical properties such as dielectric function, absorption spectra, reflectivity and energy-loss spectra of monoclinic phase and rutile phase VO2had been studied. The calculated results indicate that monoclinic phase VO2has not the character of near-infrared radiation shielding. But rutile VO2is suitable for transparent and heat-insulating materials for windows.Finally, nano-LaB6/ethanol dispersion was prepared by surface modification and dispersion in ethanol medium. The influence of modifier type and amount, dispersing condition on the stability of nano- dispersion was studied. Nano-LaB6dispersion was characterized by TEM, FTIR and laser particle diameter analyzer, and the modification mechanism of nano-LaB6particles with anionic surfactants was discussed. Optical performance of nano-LaB6dispersion also had been studied. It confirms Nano-LaB6particles have the unique optical behavior of high visible light transparency and strong optical absorption for the NIR wavelength. |
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