【作者】 尹彩流；

【导师】 黄启忠；

【作者基本信息】 中南大学 ， 材料学， 2008， 博士

【摘要】 微纳米碳球由于具有密度低（<2．26g／cm³）、物理化学性质稳定、结构特殊、较大的比表面积、优异的电磁性能和良好的生物相容性，在锂离子电池负极材料、催化剂载体、复合材料增强体、药物包裹等方面具有潜在的应用价值，有望成为高科技领域的先进材料。碳球是继富勒烯和纳米碳管之后新兴的纳米炭材料，已经引起各国研究人员的重视。本研究采用CaC₂-CCl₄（CHCl₃）体系，通过氧化还原反应制备新型结构微纳米碳球（管），对其进行结构表征，提出其生长模型，初步评估碳球作为锂离子电池负极材料的应用前景。提出以碳化钙-氯代烷这一新型无机反应体系，通过氧化还原反应在不同工艺条件下制备微纳米碳球（管）。该方法具有设备简便、反应时间短和产率较高的特点。通过热力学数据计算了CaC₂-CCl₄体系和CaC₂-CHCl₃体系反应吉布斯自由能和反应热效应。这两种体系均为强放热的自发反应，在较低温度下可以生成石墨、金刚石和C₃原子气等。按等压反应条件计算CaC₂-CCl₄（CHCl₃）体系的反应热力学能够较好地反映微纳米碳球（管）的实际合成条件。系统研究了工艺因素对CaC₂-CHCl₃体系制备碳球（管）的影响。无催化剂条件下制备了直径为200nm团聚程度小和结晶程度较高的实心碳球。以二茂铁、氯化铁和氧化铁为催化剂可分别制备直径约为150nm毛绒结构无定形结构碳球、100-200nm的Brooks-Taylor碳球和70-135nm包覆无定形炭薄膜的碳球。体系中的氩气压力为1．0MPa时，可合成四种直径为12-200nm空心碳结构：空心绒球、空心纳米角、光滑空心球／棒和多边形化的空心球。反应物量对碳球（管）直径影响不大，但随反应物量的增加，结晶程度增大。块体碳化钙可制备定向生长、直径均匀和分散性好的直管亚微米碳管（外径：160-200nm，壁厚：70nm）。无水乙醇作为反应缓冲剂可合成薄壁碳纳米空心球和锥形空心碳管。研究了不同催化剂对CaC₂-CCl₄体系制备碳球的影响。无催化剂CaC₂-CCl₄体系合成200nm左右、表面光滑而后团聚程度较小的碳球。以二茂铁、氯化铁和氧化铁为催化剂时分别合成了直径为60-200nm多孔碳球、0．3-1．8μm的空心毛绒结构无定形碳球和150nm分散性好的碳球、750nm高的碳树。提出CaC₂-CHCl₃体系合成碳球的基底催化生长模型。二茂铁热解的铁原子从基底参与催化，是生成发散的丝状结构的毛绒碳球主要原因。分别提出加压二茂铁催化CaC₂-CHCl₃体系和氯化铁催化CaC₂-CCl₄体系合成空心球形碳的液滴模板催化生长模型。CHCl₃和CCl₄雾化形成小液滴作为模板是形成空心碳结构的关键。研究了高温热处理对碳球形貌和显微结构的影响，探讨了碳球转变为碳空心多面体的转变机理。采用恒流放电法测试碳球作为锂离子电池负极材料的电化学性能。CaC₂-CHCl₃体系制备碳球经2100℃热处理经5次充放电可逆容量保持在280 mAh／g以上，11次循环库仑效率在97％以上。CaC-2-CCl₃体系制备碳球高温热处理经15次循环，其可逆容量保持在190mAh／g，库仑效率接近100％。CaC₂-CHCl₃（CCl₄）体系制备碳球经高温热处理可望应用于锂离子二次电池负极材料。更多还原

【Abstract】 Micro/nano carbon spheres have low density （<2.26g/cm³）, stable physico-chemical properties, special structure, big specific surface area, excellent electromagnetic properties and good biocompatibility. Therefore, carbon spheres are potential candidates in cathode material of Li-ion batteries, carrier of catalysts, enforcement of composites and drug capsules, and are probably applied in advanced materials of high-tech fields. Carbon spheres are another hot of novel carbon nanomaterials after fullerenes and carbon nanotubes, and are absorbing more and more attentions all over the world. In this study, the structures of carbon spheres （tubes） via oxidation reduction reaction are characterized, and their growth models are proposed. Furtheremore, carbon spheres as negative electrodes of Li-ion batteries are also primarily accessedCalsulm carbide-chloroalkane is proposed to fabricate micro/nano carbon spheres （tubes） by oxidation reduction reaction under different process conditions. The advantages of this metheod are simple, quick and high carbon yield.Gibbs energies and heat effects of CaC₂-CCl₄ system and CaC₂-CHCl₃ system were calculated based on thermodynamics data. These two systems are all intensely exothermix and spontaneous, and graphite, diamond and C₃ （atom gas） can be produced through these systems under lower temperature. According to isobaric reaction condition, the thermodynamics of two reaction systems can accord with the synthesis conditions of micro/nano carbon spheres （tubes）.Effects of process factors on carbon spheres （tubes） through CaC₂-CHCl₃ system were systematically investigated. With no-catalyst condition, carbon spheres with diameter about 200nm, low agregation degree and better crystallinity were synthezied. With ferrocene, iron chloride and iron oxide as catalysts, fluffy carbon spheres with diameters approximate 150nm and amorphous carbon, Brooks-Taylor carbon spheres with diamemters between 100-200nm and carbon spheres with diameters 70-135nm were fabricated, repectively. When the autolave was filled with 1.0MPa Ar gas, four hollow carbons with diameters between 12-200nm were formed, including fluffy hollow carbon spheres, hollow carbon nanohorns, smooth hollow carbon spheres/rods and hollow carbon polyhedrons. With the increase of reaction contents, the crystallization degree carbon spheres （tubes） increases, but is not effective to the diameters. With bulk CaC₂ as reactants, submicro-carbon tubes with directional growth, uniform diameter （external diameter: 160-200nm, wall thichness:70nm） were synthesized. Hollow carbon speres and hollow cones were formed while absolute acohol as reaction buffer.Effects of different catalyst on smooth carbon spheres （tubes） by CaC₂-CCl₄ systems were studied. Under no-catalyst condition, t diameter about 200nm and low agreegation were studied. While ferrocene, iron chloride and iron oxide as catalysts, porous carbon spheres （diameters :60-200nm）, fluffy hollow carbon spheres with amorphous structure （diameters: 0.3-1.8μm）, and well-distributed carbon spheres （diameters: approximate 150nm） and carbon tree （height: 750nm） were formed.The substrate catalysis growth model of carbon spheres by CaC₂-CHCl₃ system was proposed. Fluffy carbon spheres with filamentous and scattering structure cause from the substracte catalysis of iron atoms pyrolyzed from ferrocene.The droplet model substrate growth models of hollow spherical carbon of pressure ferrocene catalyzed CaC₂-CHCl₃ system and FeCl₃ catalyzed CaC₂-CCl₄ system were proposed, respectively. During the reaction process, CHCl₃ and CCl₄ droplets by atomization are the key fators to form hollow carbon strutures.Effect of high temperature treatment on morphology and structure of carbon spheres were studied. The transformation mechanism of carbon spheres to hollow carbon polyhedrons was discussed.The electrochemical properties of carbon spheres as negative electrodes of Li-ion batteries using constant current discharge were studied. Though 2100℃heat treatment, the reversible capacity of carbon spheres of CaC₂-CHCl₃ system after 5 cycles is 280mAh/g with coulomb efficiency of above 97% after 11 cycles. The reversible capacity and coulomb efficiency of carbon spheres of CaC₂-CCl₄ system after 15 cycles is 190mAh/g and near 100%, respectively. Carbon spheres of these two systems through high temperature heat treatment are candidate materials of negative electrodes of Li-ion batteries.更多还原