【作者】 王存景；

【导师】 刘旭光；

【作者基本信息】 太原理工大学 ， 应用化学， 2008， 硕士

【摘要】 迄今为止,国内外对纳米洋葱状富勒烯（NOLFs）的合成进行了广泛的研究。目前制备NOLFs的方法虽多,但均存在一些问题,如成本高、产量低等。多种合成方法中,化学气相沉积（CVD）法被认为较适宜于宏量制备,并且利用该法已经实现了碳纳米管（CNTs）的大量合成,但是此法合成NOLFs还不够成熟,合成的产物中往往伴有CNTs等杂质,因此很有必要进一步探索适宜于CVD法合成NOLFs的条件。本文首先选用Fe/Al（OH）₃作催化剂以乙炔为碳源、氩气作载气,在400℃、460℃、600℃、700℃和1000℃下进行反应,详细探讨了温度对产物形貌的影响。应用场发射扫描电子显微镜（FESEM）、能谱分析（EDS）、高分辨透射电子显微镜（HRTEM）和X射线衍射（XRD）测试手段对产物进行了结构表征和分析。结果显示:反应温度为400℃时合成了内包Fe₃C的NOLFs,这些NOLFs的石墨片层呈层状堆积结构,产物中无CNTs杂质出现;反应温度为460℃时也合成了内包Fe₃C的NOLFs,但同时产物中还出现了CNTs;当温度为600℃、700℃时,CNTs则成了主要产物;进一步将反应温度升至1000℃时有大量的碳微球（CMBs）生成。说明反应温度为400℃时较适宜于NOLFs的生长。基于氢氧化铝等载体较难从产物中分离和400℃时产物中没有CNTs和CMBs等杂质出现,又以水溶性氯化钠为载体用浸渍法制备了Fe含量分别为0.3wt%,1.6wt%,3.3wt%和5.2wt%的Fe/NaCl催化剂,在400℃下催化裂解乙炔合成纳米碳材料,通过FESEM、EDS、HRTEM和XRD测试手段对产物进行了结构表征和分析。结果显示:用Fe含量为0.3wt%的Fe/NaCl催化剂在400℃下合成了直径在15-50nm之间石墨片层呈层状堆积结构的内包Fe₃C的NOLFs,进一步将产物在1100℃下真空热处理得到了石墨化程度较高的NOLFs;并基于实验现象,详细探讨了内包金属NOLFs的生长机理,建立了本实验条件下内包金属NOLFs的生长所遵循的汽-固生长模型。更多还原

【Abstract】 Until now,extensive research has been devoted to the synthesis of nano onion-like fullerenes（NOLFs）.Although several methods to fabricate NOLFs have been developed,there are still a few problems such as expensive production costs and low production in their synthesis.Among several methods, chemical vapor deposition（CVD）is considered the most efficient for large scale production and the commercial production of carbon nanotubes（CNTs）has been achieved by CVD.However,NOLFs have not yet been commercialized because there are still a lot of problems in their CVD synthesis and further research is necessary.At first,synthesis reactions were carried out by CVD using an iron catalyst supported on aluminum hydroxide at 400℃,460℃,600℃,700℃and 1000℃in the presence of argon as carrier gas and acetylene as carbon source.The samples were characterized by field-emission scanning electron microscopy （FESEM）,energy dispersive spectroscopy（EDS）,high-resolution transmission electron microscopy（HRTEM）and X-ray diffraction（XRD）.The results show that NOLFs encapsulating an Fe₃C core with a structure of stacked graphitic fragments were obtained at the low temperature of 400℃,and no CNTs were observed in the product.As the reaction temperature was raised to 460℃, CNTs were grown along with NOLFs.With the reaction temperatures increased to 600℃and 700℃,CNTs became the main products,while NOLFs were by-products.When the temperature was further raised up to 1000℃,large quantities of carbon micro-spheres（CMBs）were shown.These data suggest that the low temperature of 400℃is suitable for the growth of NOLFs.As it was difficult to separate aluminum hydroxide support from the final product and no CNTs or CMBs were observed in the product synthesized at 400℃,nano-carbon materials were synthesized by the catalytic decomposition of acetylene at 400℃using iron supported on sodium chloride as catalyst.The catalysts contain about 0.3,1.6,3.3 and 5.2 wt%iron.The samples were examined by FESEM,EDS,HRTEM and XRD.The results show that NOLFs surrounding an Fe₃C core were obtained using the catalyst containing 0.3 wt% iron.The NOLFs had a structure of stacked graphitic fragments,with diameters in the range of 15-50 nm.When the product was further heat-treated under vacuum at 1100℃,NOLFs with a clear concentric graphitic layer structure were obtained.The growth mechanism of NOLFs encapsulating metallic cores was suggested to be in accordance with a vapor-solid growth model.更多还原