【作者】 张斌；

【导师】 康鹏超；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2009， 硕士

【摘要】 本文以高能球磨后的C、Si纳米粉末为原料,在900~1450℃反应合成了βSiC纳米线。利用扫描电子显微镜(SEM)、能量色散谱分析(EDS)、X射线衍射分析( XRD)、透射电子显微镜( TEM)、高分辨电镜(HRTEM)、傅里叶变换红外光谱(FT IR)及拉曼光谱(Raman)等多种分析测试手段对SiC纳米线的形貌、结构以及光谱性能进行了表征;研究了制备工艺中不同基片、反应温度、保温时间、环境气氛和粉体中的碳硅比等因素对SiC纳米线生长的影响;通过热力学理论计算,分析了SiC纳米线生长的生长过程及生长机理。对形貌观察发现,SiC纳米线大量生长,直径在十几到几十个纳米的范围内,粗细均匀,纳米线较长,可达到几百个微米。纳米线的表层存在一层均匀的SiOx非晶层,厚度约为十几个纳米。纳米线主要有直线交错状和弯曲缠绕状两种形态,局部有分叉现象。对纳米线进行结构分析表明,本方法制备的纳米线为面心立方结构的βSiC。SiC纳米线中存在堆垛层错、孪晶等结构缺陷,孪晶面由{111}面组成,纳米线的生长方向为<111>方向。各影响因素对SiC纳米线制备的影响:低温下纳米线弯曲生长,直径较细,随着制备温度的升高,SiC纳米线逐渐变为直线生长,直径也变粗;纳米线的生长存在一个孕育期,在1000℃、真空条件下制备时,SiC纳米线生长的孕育期约为90~120min;在Si基片上制备SiC纳米线时,增加粉体中碳粉的比例,有利于SiC纳米线的生长,当采用纯C粉和Si基片反应制备SiC纳米线时,可以得到没有SiOx非晶层外壳的SiC纳米线。SiC纳米线的生长满足热力学条件, Si(s,l)+C(s)→SiC(s),SiO(g)+3C(s)→SiC(s)+2CO(g), 3SiO(g)+CO(g)→SiC(s)+2SiO2 (g)等反应是本方法合成SiC纳米线主要反应形式。反应中的SiO和CO气体来自于C Si纳米粉体的氧化。SiC纳米线主要通过C粉吸附SiO气体发生气固反应,或SiO和CO直接发生气相反应形成SiC晶核的,在C Si纳米粉体球磨时产生的SiC纳米晶粒起到了籽晶的作用。在生长过程中,纳米线的Si/SiOx端头充分吸收了周围的Si、C、SiO及CO,从中达到过饱和析出,维持纳米线的生长。更多还原

【Abstract】 βSiC nanowires were synthesised at 900~1450℃from carbon and silicon nanopowders, which were prepared by high energy ball milling. Scanning electron spectroscopy (SEM), energy disperse spectrum (EDS), X ray diffraction (XRD), transmission electron microscopy (TEM), high resolution electron microscopy (HREM), Fourier transform infrared spectroscopy (FT IR) and Raman spectra were used to analysis the morphology, structure and spectrum properties ofβSiC nanowires. We researched different technological parameters in the preparation processing, such as substrates, temperature, time, atmosphere, ratio of carbon and silicon. At last, thermodynamic parameters were calculated, the growth process and mechanism of SiC nanowires were analyzed.By morphology analysis, SiC nanowires were synthesized in large quantity with uniform diameter from ten to several tens nanometer and longth of several hundreds micrometer. There is a uniform SiOx amorphous layer on the surface of SiC nanowires. There are two kinds of SiC nanowires, which are linearity and forniciform. The microstructure analysis indicate that the nanowires areβSiC with face centered cubic structure. There are stacking faults and twin lamellaes in the SiC nanowires, and the growth direction of SiC nanowire is <111>.SiC nanowires can be prepareed at the temperture from 900 to 1450℃. The nanowires grow at low temperture are forniciform, and the diameter is thiner than that grow at high temputerture. As preparation temperture increased, the nanowires become straight and thick. There is a incubation period before SiC nanowires nucleating, the incubation period is about 90~120min in vacuum at 1000℃. When the SiC nanowires prepared on the silicon substrate, if we increase the proportion of carbon powder in the mixed powders, the nanowires will grow better. If we only use pure carbon powder react with silicon substrate, the pure SiC nanowires without any amorphous layer can be obtain.The growth of SiC nanowires satisfy the thermodynamics condition, Si(s,l)+C(s)→SiC(s), SiO(g)+3C(s)→SiC(s)+2CO(g), 3SiO(g)+CO(g)→SiC(s)+2SiO 2(g) are main reactions in the growth process. The SiC crystal nucleus comes from gas phase reaction or gas solid reaction. The Si/SiOx meltdown particle on the end of nanowires just like the metal catalyst particles in VLS mechanism, absorb Si, C, SiO and CO, when it reaches saturation, SiC phase precipitat and then the SiC nanowires grow continuously.更多还原