【作者】 任文芳；

【导师】 刘旭光；

【作者基本信息】 太原理工大学 ， 物理化学， 2010， 硕士

【摘要】 C₆₀、洋葱状富勒烯（OLFs）及碳微球（CMSs）等零维碳材料以其独特的笼状结构和电学、磁学、化学等特殊的性能而受到人们的广泛关注,其中,C₆₀可看作最简单的OLFs,CMSs可以看作是石墨化程度较低的长大的OLFs。光子晶体是一种将不同介电常数的介质在空间中按一定周期排列而形成的人造晶体。光子晶体的基本特征是具有光子带隙,频率落在带隙中的光将不能传播,这使其比普通光学材料具有更广泛的应用。将碳材料用于制备光子晶体有着巨大的应用前景,关于这方面的研究也正成为人们的研究热点。本文主要采用化学气相沉积（CVD）法,以C2H2为碳源,制备了OLFs和CMSs,考察了催化剂对产物的影响,然后对产物进行了后处理并测试了产物的铁磁性能;本文以CMSs作为结构基团进行自组装,考察了溶剂、组装方法、基片、悬浮液pH值、悬浮液浓度和反应温度对自组装效果的影响。采用场发射扫描电子显微镜、高分辨透射电子显微镜、热重分析、拉曼光谱、X-射线衍射和原子力显微镜等对产物进行了表征分析,并利用振动样品磁强计（VSM）测试了产物的铁磁性能。结果表明:1、以NaCl分别担载Fe、Co、Ni作催化剂,采用CVD法在420℃进行反应,结果表明Fe/NaCl和Co/NaCl作催化剂时产物为内包金属的OLFs,而Ni/NaCl作催化剂时产物大部分为碳纳米管（CNTs）;用Co/NaCl作催化剂,进一步探讨催化剂含量对产物的影响:当Co含量为2wt.%时,在此温度下用CVD法合成了大量直径分布在10-60 nm之间的内包Co的OLFs;没有催化剂时在420℃的低温下没有产物生成,将温度升高至950℃进行反应制备了CMSs;将OLFs用浓盐酸浸泡后,Co核仍被碳壳层包覆,说明碳包覆层保护Co颗粒免受浓酸腐蚀;进一步将样品在900℃热处理后,碳包覆层的石墨化程度略有提高;铁磁性能测试表明:产物具有独特的铁磁性能。2、用浓HNO3和H2O2（体积比为1:1）对CMSs进行了表面修饰,使其团聚现象有所改善;用NaOH溶液作溶剂配制悬浮液,以载玻片为基片,采用垂直沉积法可实现CMSs的自组装,得到CMSs薄膜。在一定温度下,pH≈13时得到了排列较为致密的薄膜;在此温度和pH值时,随着悬浮液浓度的增大,薄膜厚度增大,当浓度为2wt.%时,可得到排列较为致密的薄膜;进一步对反应温度进行探讨,发现较为适宜的沉积温度为50℃。所得样品在自然光的照射下,呈现出一定强度的反射光且颜色较为均匀,说明所得自组装膜有较好的均匀性,为下一步光学性能的测试奠定了基础。更多还原

【Abstract】 Because of their unique spherical structure and special properties in electronics, magnetic, chemistry and so on, zero-dimensional carbon materials, such as C₆₀, onion-like fullerenes （OLFs）, and carbon microspheres （CMSs）, have attracted much research interest. Among these materials, C₆₀ is the simplest OLFs and CMSs are giant OLFs with low graphitized degree. Photonic crystals are artificially arranged periodic structures of materials with different dielectric constants in optical wavelength scale. The transmittance of light is forbidden in a wavelength range called photonic band gap. Photonic crystals have broader application prospect than common optical materials. It is promising to prepare photonic crystals using carbon materials as building blocks. The research in this area is becoming hot.In this paper, OLFs and CMSs were prepared by chemical vapor deposition （CVD） using acetylene as carbon source and the effects of the catalysts on the products were studied. Then the products were modified and the magnetic property of the products was measured. CMSs were used as building blocks of self-assembly. The effects of solvent, assembly method, substrate, pH value of the suspension, concentration of suspension and reaction temperature were investigated. Field emission scanning electron microscopy, high resolution transmission electron microscopy, thermogravimetry, Raman spectroscopy, X-ray diffraction, and atomic force microscopy were employed to characterize the samples. The ferromagnetic property of the products was measured with a vitrating sample magnetometer （VSM）. The results are as follows:1. Metal-encapsulating OLFs were prepared using Fe/NaCl and Co/NaCl as catalysts by CVD at 420℃, while carbon nanotubes （CNTs） were prepared using Ni/NaCl as catalyst. The influence of catalyst content on the products was further discussed using Co/NaCl as catalyst. Lots of cobalt-encapsulating OLFs were prepared when the content of cobalt was 2wt.%. In absence of catalyst, no products were obtained at 420℃, while CMSs were prepared at elevated temperature of 950℃. After immersing in concentrated HCl, cobalt nanoparticles encapsulated by carbon shells were not removed. It means that carbon shells can protect the encapsulated cobalt cores against acid. When the products were further heat-treated at 900℃, cobalt-encapsulating OLFs with higher graphitization degree were obtained. Moreover, the results from the measurement of VSM also showed a unique magnetic property.2. CMSs oxidized by HNO3 and H2O2 （volune ratio 1:1） had better dispersion than as-synthsized CMSs. Suspension of oxidized CMSs was prepared using NaOH as solvent. Vertical deposition method was adopted for the self-assembly of CMSs into films using glass slide as substrate. Film with a more compact array was obtained by self-assembly at a fixed temperature when pH value of the suspension was about 13. The thickness of the film increased with increasing suspension concentration under fixed temperature and pH value. When suspension concentration was 2wt.%, a more dense film was prepared. Further investigation on the reaction temperature showed that the suitable temperature was 50℃. Sample showed a good reflection of light with uniform color, which indicates the formation of uniform CMSs film and thus good potential for preparation of photonic crystals.更多还原