碳纳米管化学沉积CeO₂/Fe₂O₃的研究

【作者】 张成国；

【导师】 温树林； 李士同；

【作者基本信息】 山东大学 ， 材料学， 2006， 硕士

【摘要】 碳纳米管自1991年由Iijima首先发现以来，因其纳米级的直径，大的有效比表面积，中空的管状结构，能够吸附和填充颗粒，较高的化学稳定性，而使得它成为备受关注的催化剂载体。纳米氧化物CeO₂、Fe₂O₃是工业中非常重要的催化剂材料。本文选用碳纳米管和纳米CeO₂，Fe₂O₃作为研究对象，采用化学沉积法制备了碳纳米管负载的纳米CeO₂和碳纳米管负载的纳米Fe₂O₃，并对其沉积机理进行了探讨。 本文首先利用盐酸—混酸对碳纳米管原料进行了纯化氧化处理，利用高分辨电镜和红外光谱等手段对氧化后的碳纳米管进行了表征，纯化氧化比较彻底，杂质基本除掉，部分碳纳米管开口，同时在碳纳米管表面产生了大量的结构缺陷和高密度的官能团。 本文以六水合硝酸铈为原料，氨水为沉淀剂，通过在液相沉淀反应中直接加入纯化氧化的碳纳米管作为沉淀承载基体制备了碳纳米管负载的二氧化铈纳米颗粒。运用高分辨电镜、X射线分析、红外等多种表征手段对碳纳米管负载CeO₂的形态、微结构和成分进行了深入研究，综合考虑溶剂、热处理温度等各种因素的影响，优化工艺参数，得到了二氧化铈粒子在碳管的表面连续、完整致密的包覆层，有些二氧化铈粒子进入开口碳纳米管的内腔，对碳纳米管形成填充。 本文还对二氧化铈沉积的机理进行了探讨，认为二氧化铈的沉积过程是一个形核长大过程。混酸氧化产生的高密度缺陷和官能团在沉积过程中作为吸附二氧化铈形核的活化中心。由于二氧化铈之间结合较强，因而可以得到多层二氧化铈粒子包覆的碳纳米管，文章提出了一个模型来解释这些现象，并对二氧化铈和碳纳米管的界面结合强度进行了测试。 将制备碳纳米管负载二氧化铈纳米粒子的方法扩展，采用类似的方法制备了碳纳米管负载的Fe₂O₃，并运用高分辨电镜、X射线分析、能谱等表征手段对碳纳米管负载Fe₂O₃的形态、微结构和成分进行了深入研究，对不同工艺条件处理对产物的影响进行了讨论，通过对热处理条件的控制可以实现结构调变，得到不同的非晶Fe₂O₃、γ-Fe₂O₃和α-Fe₂O₃的复相结构。更多还原

【Abstract】 Since discovered in 1991 by Iijima, Carbon nanotube has attracted intensive attention as catalyst supporter due to its nano-diameter, large specific surface area, tubuler structure thant can be filled by nanoparticles, and high chemical stability. Nano-oxides such as cerium oxide and ferric oxide are important catalytic materials in catalyst industry. In this paper, Multiwall Carbon nanotube, cerium oxide and ferric oxide are chosen as experimental material, carbon nanotube supported cerium oxide and carbon nanotube supported ferric oxide are prepared in chemical deposition method. The deposition mechanism are also discussed here.In this paper, raw Multiwall carbon nanotubes are first purified and oxided by hydrochloric acid and blend acid composed of vitriol and nitric acid. High Resolution Transimission electron microscopy(HRTEM) and Infrared spectroscopy are employed to characterize the treated carbon nanotubes. The treatment is quite thorough, and impurities are fully eliminated. Tips of some Multiwall carbon nanotubes are opened , high-dense flaw and functional group are generated or introduced on the surface of Multiwall carbon nanotubes.Using cerium nitrate hexahydrate as raw material, ammonia hydroxide as precipitator, Multiwall carbon nanotubes supported cerium oxide nanoparticles were prepared by adding Multiwall carbon nanotubes into the solution as precipitation bearing matrix. High Resolution Transimission electron microscopy, X-ray diffraction and Infrared spectroscopy are employed to characterize the morphology, microstructure and component of cerium oxide supported on Multiwall carbon nanotubes. Considering the affect of agent’s concentration, heat-treated temperature and other factors on deposition quality, we optimize the parameters and finally get dense, continuous coating of cerium oxide nanoparticles. Some cerium oxide nanoparticles even fill the internal channels of the carbon nanotubes.In this paper, the deposition mechanism of cerium oxide is dicussed. The process of cerium oxide deposition is considered to be a process of nucleation and growth. High-density flaw and functional groups generated by blend acid play a role as activated center for nucleation in the deposition process. High-resolution transmission electron microscopy evidenced several layers of spherical cerium oxide nanoparticles were更多还原