【作者】 刘伯洋；

【导师】 贾德昌；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2008， 博士

【摘要】 本文采用二茂铁分别与多种无机铵盐反应合成了碳空心球、空心六臂碳颗粒、非晶态碳纳米管以及碳空心球包覆四氧化三铁或氮化铁的复合粉末。采用XRD、SEM、TEM、Raman光谱、FIB和热分析,系统研究了它们的微观组织结构与合成机理。研究发现,二茂铁和氯化铵在气压炉或密封的石英管中反应可以合成出直径分布在1～10μm,表面光滑的碳空心球。气压炉中初始气压与合成温度的提高有利于提高碳空心球的产量和纯度,初始气压为2MPa,温度为600℃时,碳空心球的产量和纯度基本达到最大值。在反应过程中伴随有Fe（NH₃）₂Cl₂、Fe（NH₃）₆Cl₂、（NH₄）₃FeCl₅和NH₄FeCl₃等铁铵络合物的生成,其中Fe（NH₃）₂Cl₂在高温下是液态球形液滴,碳在其表面沉积得到碳空心球。保持二茂铁和氯化铵质量比为2:1,通过加大原料量,可以增大碳空心球尺寸,原料总量为12.8、6.4和3.2g时,合成的碳空心球中值直径分别为6.4、4.4和3.4μm。提高氯化铵的相对含量,碳空心球中值直径有所增加,但在小直径范围内存在集中分布。而且,二茂铁与溴化铵或碳酸铵在密封石英管中500℃反应也可以合成非晶态碳空心球。采用氯化铵600℃合成的碳空心球在氩气保护下800～1200℃范围内进行热处理后出现少量4nm介孔,石墨化程度略有提高。热处理能改善以碳空心球为负极的锂离子电池循环性能,在800℃热处理后,电池的容量显著提高,首次容量可达357mA·h/g,经过40个循环后仍为303mA·h/g;热处理温度继续升高后,容量降低,但首次库仑效率由42.1%提高到65.4%。对气压炉中600℃合成地碳空心球粉末依次进行水解和热处理可以合成碳空心球包覆Fe3O4纳米颗粒的复合粉末。其中Fe3O4纳米颗粒质量百分数为13.24%。Fe3O4具有两种形貌,一种为等轴状颗粒,直径在15～90nm之间;另一种为针状颗粒,直径约为20nm,长度在120～450nm之间。碳空心球包覆Fe₃O₄的饱和磁化强度、剩余磁化强度和矫顽力分别为4.29emu/g,0.74emu/g和198.4Oe。对气压炉中500℃合成地碳空心球粉末进行适当酸洗可以得到碳空心球包覆Fe3N针状纳米颗粒的复合粉末。Fe3N针状纳米颗粒的质量百分数约为38.7%,直径约为100nm,长度在600～800nm之间。碳空心球包覆Fe₃N的饱和磁化强度、剩余磁化强度和矫顽力分别为10.61emu/g,0.67emu/g和180Oe。二茂铁和碳酸氢铵在密封石英管中500℃反应,自组装模板法可以合成碳包覆Fe3O4六臂颗粒和少量直径1～2.5μm的碳实心球。其中Fe₃O₄六臂颗粒的六个臂长度相等,约为4～6μm,且互相垂直,臂的生长方向为<100>。六臂颗粒具有鲱鱼骨状结构规则的楞。这种碳包覆Fe₃O₄颗粒经过浓盐酸清洗,变成空心六臂碳颗粒。首次采用二茂铁和氯化铵在空气中200℃下自组装合成了非晶态碳纳米管。纳米管均为开口结构,其直径分布均匀,外径约为100nm,内径约为50nm。其中还存在竹节状的碳纳米管。在真空中2200℃热处理后,仍然不能完全石墨化,但纳米管表面的碳原子倾向于有序排列。更多还原

【Abstract】 Ferrocene and several inorganic ammonium salts were used to prepare hollow carbon spheres, hollow six-armed carbon particles, amorphous carbon nanotubes and hollow carbon spheres encapsulating Fe₃O₄ or Fe3N nanoparticles. The microstructures and formation mechanisms of the products were systematically investigated by XRD, SEM, TEM, Raman, FIB and thermal analysis.The experimental results show that hollow carbon spheres of 1～10μm in diameter and smooth surface can be prepared via the reaction of ferrocene and ammonium chloride in a gas pressure furnace or a sealed quartz tube. With increase of initial gas pressure and synthesis temperature, the yield of hollow carbon spheres is enhanced and reaches a maximum value at 600℃with an initial gas pressure of 2MPa. Several iron compounds, including Fe（NH₃）₂Cl₂, Fe（NH₃）₆Cl₂, （NH₄）₃FeCl₅ and NH₄FeCl₃, are formed in different temperature ranges and Fe（NH₃）₂Cl₂ has a low melting point and serves as the core templates for carbon enwrapping to form hollow carbon spheres. The median diameter increases with the total amount of the reactants with the same weight ratio of ferrocene to ammonium chloride. When the excessive ammonium chloride was used, the hollow carbon spheres of a bimodal diameter distribution are produced. However the median diameter is almost the same. It is also found that amorphous hollow carbon spheres can be prepared in a sealed quartz tube at 500℃via the reaction between ferrocene and ammonium bromide or ammonium carbonate. The graphitization of the as-prepared hollow carbon spheres is slightly improved by the heat treatment between 800～1200℃. The mesopores of 4nm are formed after the heat treatment. The discharge capacity of hollow carbon spheres as anode material in Lithium-ion batteries is improved after heat treatment at 800℃compared with the as-prepared hollow carbon spheres and has a maximum value of 357mA·h/g and still retains 303mA·h/g after 40 cycles. However, the discharge capacity decreases and the cycling performance is improved with the increase of heat treatment temperature. In addition, the coulomb efficiency is raised from 42.1 to 65.4%。Hollow carbon spheres encapsulating magnetite nanoparticles were obtained in high pressure argon at 600℃followed by a hydrolysis of Fe（NH₃）₂Cl₂ in the hollow interiors at room temperature and a heat treatment in argon at 450℃. The weight percent of magnetite nanoparticles is about 13.2%. The dimensions of the equiaxed magnetite nanoparticles range from 15 to 90nm while the acicular magnetite nanoparticles have diameters of ca. 20nm and lengths of 120～450nm. The saturation magnetization, remanent magnetization and coercivity of the hollow carbon spheres encapsulating magnetite nanoparticles are 4.29emu/g, 0.74emu/g and 198.4Oe, respectively. Hollow carbon spheres encapsulating Fe3N nanoparticles were obtained in high pressure argon at 500℃followed by a proper acid washing process. The weight percent of Fe3N nanoparticles is about 38.7%. The acicular Fe3N nanoparticles have diameters of ca. 100nm and lengths of 600～800nm. The saturation magnetization, remanent magnetization and coercivity of the hollow carbon spheres encapsulating Fe3N nanoparticles are 10.61emu/g, 0.67emu/g and 180Oe, respectively.Carbon encapsulated six-armed Fe3O4 particles and a few carbon spheres of 1～2.5μm in diameter are synthesized by the reaction of ferrocene and ammonium acid carbonate in a sealed quartz tube at 500℃. The six arms of the Fe3O4, which have a herringbone structure, grow along <100> and they are equal in length of 4～6μm and perpendicular to each other. Hollow six-armed carbon particles can be obtained after acid washing.Amorphous carbon nanotubes with open ends are prepared via the reaction of ferrocene and ammonium chloride in air at 200℃. The amorphous carbon nanotubes have an external diameter of about 100nm, an internal diameter of 50nm and a length of several micrometers, respectively. Some bamboo-like amorphous carbon nanotubes can also be found. The atoms on the surface of carbon nanotubes become ordered after heat treatment at 2200℃.更多还原