【作者】 祝洪洋；

【导师】 杨海滨；

【作者基本信息】 吉林大学 ， 凝聚态物理， 2007， 硕士

【摘要】 本文首次用液体中电爆炸方法,分别以六甲基二硅烷（HMT）和二甲基硅油（DOS）为前驱物,成功合成了立方相纳米碳化硅。以HMT所得产物粒度分布均匀且分散性好,粒度分布为4-7nm,DOS所得产物粒度分布较宽。研究了纳米碳化硅的微波吸收特性。以纳米碳化硅颗粒为核,采用化学沉淀方法制备了SiC/ZnO纳米复合材料;对SiC/ZnO纳米复合材料的荧光特性研究发现,在325nm He-Ge激光的激发下,出现370-392nm的紫外发射峰,和中心分别在520nm和610nm的二个可见光发射带;首次发现二个可见光发射带的强度随退火温度的升高,出现了先减弱后增强的现象,探讨了产生这种现象的机制。用化学沉淀法进行了对BaMgAl₁₀O₁₇: Eu²⁺包覆MgO研究,获得了均匀包覆层,厚度为100-150nm;,包覆前后的样品分别经400-1000℃范围空气中热处理,通过对比包覆前后的样品热处理之后的Eu²⁺和Eu3+的发射谱和激发谱表明,MgO包覆层能显著抑制Eu²⁺氧化成Eu3+,明显提高了BaMgAl₁₀O₁₇: Eu²⁺发光粉的光发射热稳定性。更多还原

【Abstract】 Recent years, nano-scaled materials have attracted much attention because of their special properties compared with bulk materials. Their small sizes may result in quantum confinement effect and interface effect, which may lead to potential application in many fields. Nano-composite with core-shell structure material, usually prepared by the surface coating or surface modification technology, is one of the most interesting nano-materials because of their special properties in optics, electrics and magnetism by the coupling of the core and the shell. Synthesis and control of the nano-composite on purpose to discover new properties and rules become one of the most interesting part of material science research. In this paper, SiC nanoparticles were synthesized by electrical explosion method, The microwave absorption property of the SiC nanoparticles was discussed.Using the SiC nanoparticles as precursor, SiC/ZnO nanocomposites were synthesized by co-precipitation processes. A nucleation and crystal growth model for this structure was proposed. The resultant nano-composites were characterized by X-ray diffraction, transmission electron microscope, field emission scanning electron microscope and photoluminescence spectroscope. The spectrum of as-synthesized sample exhibits three emission peaks. One is a strong UV emission peaking around 370-392 nm, others are weak around 520 nm and 610 nm. The ultraviolet emission occurs in ZnO nanoparticles and shifts to short wavelengths as the dimension decreases. This blueshift behavior of PL peak position is naturally explained by the expected effect of quantum confinement. To our interest is that after heat-treatment at 200 oC and 300 oC, the green and orange emissions decrease compared with as synthesized sample. However, when the annealing temperatures further increase to 400 oC and 500 oC, the two emissions simultaneously increased. The observed changes in green emission with increasing annealing temperatures can be explained by following models: one is oxygen vacancy and another is band bending and impurities. The former plays a dominant role at lower temperature and the later is in action at higher temperatures.BaMgAl₁₀O₁₇: Eu²⁺ （BAM）/MgO were synthesized by co-precipitation processes. The resultant nano-composites were characterized by X-ray diffraction, transmission electron microscope, field emission scanning electron microscope and photoluminescence spectroscope. SEM and TEM images show that nanometer MgO was homogenously coated on it. Photoluminescence spectroscope indicated that the thermal stability was improved after coating. MgO as a protective layer can prohibit the oxidation of Eu²⁺; therefore the surface coating that could prohibit a surface chemical reaction would improve the phosphor longevity and thermal stability.更多还原