【作者】 李振涛；

【导师】 邱介山；

【作者基本信息】 大连理工大学 ， 化学工艺， 2010， 博士

【摘要】 微纳米炭材料尺度和形貌多样,具有独特的光、电、磁和机械性能,在功能材料领域展现出广阔的应用前景。规模化、低成本、尺度和形态可控制备是实现微纳米炭材料实际广泛使用的基本前提条件。本论文根据煤的组成和结构特征,采用“分子剪裁”的技术策略,借助电弧等离子体及其耦合化学气相沉积技术手段,实现了多种功能性微纳米炭材料的选控制备,主要研究内容和成果如下：1.自行研制一套多功能电弧等离子体实验装置、煤基炭棒炭化装置并实现等离子体原位光谱诊断。电弧等离子体实验装置阴极卡套设进气管,不同种类的碳氢气体可直接进入电弧等离子体区域；通过发射光谱,对炭材料的制备过程进行检测和分析。2.以煤为碳源,通过电弧等离子体法实现煤基一维纳米炭材料—单壁碳纳米管(SWCNTs)及双壁碳纳米管(DWCNTs)的大量制备,建立了适于SWCNTs纯化的技术方法。以Y2O3和Ni为催化剂,在氦气条件下制得大量的SWCNTs,其产率在10%以上放电过程的原位光谱诊断结果显示,电弧等离子体中存在C2和CN物种,电弧区域温度为3150 K,通过氧化性酸处理与空气氧化,SWCNTs纯度可达近90wt.%；使用FeS催化剂,在氦气和氢气混合气氛中制备了大量的DWCNTs,其生成速率可达25 mg/min,光谱诊断发现其生长过程中存在C2和CH物种,电弧区域温度为3050 K。3.以煤基炭棒为阳极,将有机气体引入等离子体区域,实现电弧等离子体技术和化学气相沉积技术的耦合,通过调节催化剂用量等条件选控制备了零维纳米炭材料—纳米洋葱状富勒烯(NOLFs)和碳包覆磁性金属纳米颗粒(CEMNs)。NOLFs石墨层数可以达到数十甚至数百层,呈现同心圆状,具备良好的洋葱状结构；CEMNs具有较窄的直径分布和良好的石墨化程度,在室温下具有铁磁性、高磁响应性和抗酸腐蚀性。4.以煤基炭棒为阳极,利用电弧等离子体耦合化学气相沉积技术,通过调节反应条件如催化剂种类及用量和气氛种类及压力等,实现多种功能性微米炭材料—碳带、螺旋炭纤维、炭微米树以及分级结构炭材料的选控制备。碳带的宽厚比为7.5-50,长度可以达到几百微米乃至毫米量级,碳带尺度由催化剂尺寸决定,放电气氛是影响碳带形貌的关键因素；螺旋炭纤维由单根炭纤维规则地螺旋卷合而成,螺旋方向有左旋和右旋两种形式,存在交叉螺旋现象；制备的炭微米树具有实心结构、良好的石墨化程度和与碳纳米管相接近的弹性模量,其生长的关键性因素是铁催化剂和有机气体的使用；碳纤维阵列呈现锥状结构,由直径50-200 nm的纳米碳纤维组装构成,通过对煤基炭棒的预处理,实现了分级结构炭材料形貌的可控调变,基本结构单元变为顶部填充金属的荆棘状碳纤维。更多还原

【Abstract】 Micro/nano-sized carbon materials have attracted extensive research interests across the world in recent years due to their unique physical and chemical properties as well as potential applications in many high-tech fields. Selective and controlled preparation with low price is the precondition of commercial application of these functional carbon materials. Based on the specific structure and chemical composition of coals, a series of functional carbon materials have been successfully fabricated via the technique of arc plasma or arc plasma coupled with chemical vapor deposition (CVD) and the results obtained are summarized as follows.A multi-functional device of arc plasma system was designed and built. Various hydrocarbons could be introduced into the plasma zone via the hole in the cathode for making different carbon materials. The process of arc plasma could be diagnosed in-situ by optical emission spectroscopy (OES).One-dimensional (1 D) nanomaterials, single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs), were synthesized by arc plasma method using coal-based carbon rods as the evaporating anode. The influences of experimental parameters, such as the catalyst, atmosphere, pressure, coal types and carbonization temperature of rods, on the production of SWCNTs were investigated systematically. The results show that Taixi anthracite is a suitable carbon source for mass production of SWCNTs with Y2O3 and Ni as catalysts at a helium pressure of 0.05 MPa. The yield of the SWCNTs could reach up to 10%. The species in the arc plasma during the preparation process were analyzed using OES. The OES analysis reveals that active species such as C2 dimers and CN species were present in the arc plasma and the active intermediates involved in the formation and growth of SWCNTs. The impurity was removed by mixture acids combined with air and the purity of the SWCNTs was about 90 wt.%. High quality DWCNTs could be obtained in large scale in the mixture of hydrogen and helium using FeS as catalyst. The production rate of DWCNTs was 25 mg/min. The CH species as well as C2 dimers were identified in the preparation process of DWCNTs.Zero-dimensional (0 D) nanomaterials, nano onions-like fullerences (NOLFs) and carbon-encapsulated magnetic nanoparticles (CEMNs), were fabricated on a large scale by arc plasma combined with CVD in acetylene atmosphere. The NOLFs have several hundred graphene layers with concentric circle structure. The as-obtained CEMNs with well-ordered graphitic shells have narrow diameter distribution and ferromagnetic properties at room temperature. The results suggested that the magnetic nanoparticles could be well protected from the acid eroding.A series of micrometer sized carbon materials were selectively prepared with high efficiency on a large scale by arc plasma coupled with CVD in the presence of hydrocarbons, of which coal-based carbon rods were used as consuming anode. The synthesis of micrometer carbon materials, such as carbon belts, carbon micrcoils (CMCs), carbon microtrees, carbon strings and hierarchical carbon microfibers, have been accomplished by adapting the experimental condition. It is found that the carbon belts obtained have the width of 1.5-2.5μm, the thickness of 50-200 nm and the length of hundreds of micrometers, of which possess a large width-to-thickness ratio. A combination process has been demonstrated in which catalyst grain with a shape of cuboid formed during arc plasma was responsible for the growth of carbon belts during the subsequent chemical vapor deposition. The CMCs are composed of almost amorphous carbon without any pore in the fiber axis, existing both left-chirality and right-chirality. It is found that the carbon micro-trees grew on the anode surface with highly-oriented arrays when iron was used as catalyst in the presence of acetylene. The carbon micro-trees have a solid inner core and an anisotropic yet highly graphitized structure. The Young’s modulus of the micro-trees is comparable to that of carbon nanotubes reported in literature. In the case of the un-treated coal-based anodes, a large amount of whisker-like strings that are perpendicular to the anode surface in aligned arrays and composed of nano-sized carbon fibers in diameter 50-200 nm are obtained. When the coal-based anodes are impregnated with salt solution, thorn-shaped fibers act as their basic building blocks.更多还原