竹节状纳米碳纤维的制备及嵌锂性能研究

以泡沫镍为催化剂 ,在 6 0 0和 70 0℃下 ,以CVD法热解乙炔气体制备大量的纳米碳纤维 .随着制备温度增加 ,纳米碳纤维直径变小 ,竹节状含量减少 ,d0 0 2 值减小 ,微晶片层平面Lc 和La 值增大 ,碳材料的可逆容量则下降 .分别用透射电镜、X射线衍射和拉曼光谱观察和测定了纳米碳纤维的形貌、微结构 ,发现在不同条件下生长的纳米碳纤维有不同的形貌和结构 .对纳米碳纤维的电化学嵌锂性能的研究表明 ,纳米碳纤维的结构对其电化学嵌锂容量和充放电循环寿命起重要影响 ,制备温度越低 ,纳米碳纤维的石墨化程度越差 ,可逆嵌锂容量相应要高一些     

化学气相沉积法制备定向碳纳米管阵列

以二茂铁和二甲苯分别作为催化剂和碳源，采用一种无模板的化学气相沉积法，使用单温炉设备，成功地制备了高度定向的碳纳米管阵列.分别用扫描电子显微镜、透射电子显微镜和电子能量散射谱、拉曼光谱对碳纳米管阵列进行形貌观察和表征, 并研究了不同工艺参数对碳纳米管阵列形貌的影响.结果表明：在生长温度为800℃，催化剂浓度为0.02g/mL，抛光硅片上容易获得高质量的定向碳纳米管阵列，在此优化条件下生长的定向碳纳米管的平均生长速率可达25μm/min.     

阵列碳纳米管的石墨化程度

采用化学气相沉积法制备了阵列碳纳米管薄膜,对阵列碳纳米管的石墨化程度进行了系统研究。利用扫描电子显微镜(SEM)、拉曼光谱(Raman)对样品形貌以及结构进行了表征。探讨了不同实验参数对阵列碳纳米管石墨化程度影响的机理。结果发现,在一定催化剂浓度范围内,催化剂浓度过低时,阵列碳纳米管的石墨化程度较差,而随着催化剂浓度的增加,阵列碳纳米管的石墨化程度逐渐变好;生长石墨化程度较好的阵列碳纳米管需要合适的进液速度,进液速度过低或过高都会使得碳纳米管的石墨化程度变差;此外,生长石墨化程度较好的阵列碳纳米管也需要合适的生长温度,生长温度过低或过高都会使得碳纳米管的石墨化程度变差。     

ZnO纳米线的合成与生长机理

采用化学气相沉积系统制备ZnO纳米线,以覆盖一层约5nm厚的Ag薄膜的单晶Si(001)为衬底,纳米线的生长遵循气-液-固(VLS)机理。对得到的样品采用X射线衍射(XRD)和扫描电镜(SEM)进行晶体结构和形貌的表征。XRD结果表明衬底温度在600~700℃时生长的ZnO纳米线具有六方结构和统一的取向。通过扫描电子显微镜分析,比较了生长温度对纳米线直径和长度的影响。实验表明我们可以通过催化剂和温度来实现ZnO纳米线生长的可控。与传统的VLS生长方式不同的是在我们制备的ZnO纳米线顶端并没有看到催化剂颗粒,表明纳米线的生长方式是底部生长,我们对其生长机理进行了研究。     

利用飞秒激光加工碳纤维(英文)

为验证光学加工碳纤维材料的可行性,利用飞秒激光和连续激光对碳纤维块体材料进行了加工。获得了利用飞秒和连续激光加工的表面形貌。与连续激光加工相比,利用脉宽40fs的激光加工效率较高,加工区边缘形貌较好,加工质量较高。通过不同激光功率下加工孔径尺寸的研究获得了飞秒激光加工阈值在1012W/cm2量级。研究结果证明了光学加工碳纤维体材料的可行性。     

化学气相沉积法制备GaN纳米结构设计性实验

在无催化剂辅助条件下,采用化学气相沉积法生长了GaN纳米线.通过调整衬底、NH3气流、生长时间等,实现了半导体GaN纳米线的生长以及形貌调控.用X射线衍射仪和扫描电子显微镜对产物的物相及形貌进行了表征.获得了合成GaN纳米线的优化条件.     

不同厚度的Nd123片层的2-2复合籽晶对SmBCO样品生长的影响

采用MgO单晶与NdBa2Cu3O7-δ(Nd123)粉体的2-2复合体籽晶可以充分利用MgO与NdBCO籽晶的优势,对SmBCO晶体的生长起到了很好的诱导作用,成功制备出单畴SmBCO超导块材.本文采用不同厚度的Nd123片层和MgO单晶作为2-2复合体籽晶通过顶部籽晶熔渗生长工艺(TSIG)制备SmBCO超导块材,研究了Nd123片层的厚度对SmBCO样品生长的影响.结果表明,随着Nd123片层厚度的增加,样品的单畴形貌逐渐消失,并且出现了随机成核.通过对样品的生长特性和微观结构的研究,阐明了不同厚度的Nd123片层对SmBCO晶体生长形貌的影响机制.     

ZnO纳米线薄膜的合成参数、表面形貌和接触角关系研究

水浴法合成ZnO纳米线薄膜的工艺参数直接影响其表面形貌, 并使其接触角及润湿性能发生变化. 本文仿真分析了轮廓算数平均偏差、偏斜度、峭度、相关长度等特征参数对随机粗糙表面特性的影响规律; 改变生长时间、种子层溶液和生长液的浓度, 批量制备了表面形貌不同的ZnO纳米线薄膜; 提出了取样长度的确定方法, 并基于扫描电镜图像和Matlab图像处理算子对ZnO纳米线薄膜表面形貌的特征参数进行了提取; 将表面形貌高度和水平方向的特征参数引入Wenzel模型, 分析了合成参数、表面形貌特征参数与接触角的影响关系. 结果表明, 合成参数变化时, 选择取样长度5.0 μm为宜; 生长液浓度大于0.125 mol/L时, ZnO纳米线之间发生重结晶, 并呈现疏水性; 改变种子层溶液浓度和生长时间, 均得到超亲水表面. 上述结论可用于不同氧化酶、细胞等在ZnO纳米线薄膜上的有效吸附及相应传感器测试性能的进一步提高. 关键词： ZnO纳米线 水浴合成 表面形貌 接触角     

掺杂NaCl水溶液结晶形貌的分形研究

水溶液结晶是研究分形形貌的重要实验之一。本文通过改变溶液浓度,溶质组分和结晶温度等宏观实验参数,用分形维数的方法研究了这些参数对结晶形貌的影响。指出在低浓度下的非平衡态中溶液结晶形貌具有分形结构;不同晶体的生长作用力相互竞争,混乱度最大的情况下形成的分形结构最凸出,生长作用力是影响晶体形貌的主要因素;同时,分子热运动也是影响结晶形貌的因素之一。     

薄膜系列实验的教学研究

从薄膜制备、生长过程动态分析以及形貌表征3方面设计了薄膜系列实验.用离子束溅射制备金属薄膜,研究了制备条件对溅射速率的影响,测量了薄膜生长过程中电阻的变化,用扫描隧道显微镜或原子力显微镜观测薄膜的表面形貌,并分析不同制备条件得到的薄膜的表面形貌特征.     

固体单相催化剂CVD法制备成束或分散MWCNT*

CVD法制备纳米碳管的催化剂多是以Al2 O3、SiO2 或MgO作载体 ,Fe、Ni或Co等过渡族金属为活性组分[1- 3] .催化剂与载体之间的关系存在多种形式[1] ,其中固溶体催化剂[4 ,5] 使过渡金属离子能均匀地分布在载体的内部和表面 .在后续反应过程中 ,均匀分布在表面或体内的金属离子被还原成具有催化活性的金属微粒 .此法称为“原位催化分解法 (insituCVD法 )” ,常用于制备直径分布较为均匀的纳米碳管 ,但以往的这些固溶体催化剂在制备纳米碳管的产量上并没有明显的改善 .本工作报道用燃烧法制备的Fe Mo Mg O固溶体 ,不但在用于CVD法生长…     

Production of carbon nanotubes by self-propagating high-temperature synthesis

Carbon nanotubes are prepared by the method of self-propagating high-temperature synthesis for the first time. The initial components for this synthesis are carboniferous materials (soda, limestone, and Teflon) and reducers (magnesium, lithium, and sodium) with addition of a nickel or iron catalyst. The morphology of the nanotubes (straight multiwall nanotubes apparently free of a catalyst, bent nanotubes completely filled with a catalyst, and carbon nanofibers) is similar to that of nanotubes grown by chemical methods. The nanotubes account for 2–4 wt % of the product synthesized.     

The growth of multi-walled carbon nanotubes on natural clay minerals (kaolinite, nontronite and sepiolite)

The suitability of clay minerals - kaolinite, nontronite and sepiolite - is studied for synthesis of nanocomposites based on carbon nanotubes. Particles of iron were used as catalysts. Prior to synthesis, kaolinite and sepiolite were doped by the catalytically active metal, whereas in the case of nontronite the presence was used of this metal in the matrix of this mineral. Synthesis of CNTs was performed by hot filament chemical vapor deposition method. The produced nanocomposites were examined by transmission and scanning electron microscopies and energy dispersive X-ray spectroscopy. The experiment verified the potential of the three microcrystalline phyllosilicates for the growth of carbon nanotubes. Under the same technology conditions, the type of catalyst carrier affects the morphology and structure of the nanotube product markedly.     

采用铁基催化剂在V型热解火焰中合成碳纳米管的实验研究

催化剂的选取对于V型热解火焰合成碳纳米管具有重要的影响.实验中分别采用五羰基铁、二茂铁、纳米铁粉等作为催化剂,取样时间为10 min,温度约为1150 K,催化剂的引入方式为喷雾热解方法,利用扫描电镜和透射电镜对合成的碳纳米管进行形态和结构表征分析.实验结果表明:利用V型热解火焰合成碳纳米管时的关键物质是纳米氧化铁颗粒...     

Effect of nickel,iron and cobalt on growth of aligned carbon nanotubes

The effect of pure nickel, iron and cobalt on growth of aligned carbon nanotubes was systematically studied by plasma-enhanced hot-filament chemical vapor deposition. It is found that the catalyst has a strong effect on the nanotube diameter, growth rate, wall thickness, morphology and microstructure. Ni yields the highest growth rate, largest diameter and thickest wall, whereas Co results in the lowest growth rate, smallest diameter and thinnest wall. The carbon nanotubes catalyzed by Ni have the best alignment and the smoothest and cleanest wall surface, whereas those from Co are covered with amorphous carbon and nanoparticles on the outer surface. The carbon nanotubes produced from Ni catalyst also exhibit a reasonably good graphitization. Therefore, Ni is considered as the most suitable catalyst for growth of aligned carbon nanotubes. Received: 30 November 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002     

The synthesis of multi-walled carbon nanotubes (MWNTs) by catalytic pyrolysis of the phenol-formaldehyde resins

A series of carbon nanomaterials, particularly multi-walled carbon nanotubes (MWNT), are obtained as products from catalytic pyrolysis of the cross-linked phenol-formaldehyde resins with different ferrocene under inert atmosphere. The morphology and structure of the samples were evaluated by TEM and XRD techniques. CNTs morphology is dependent on the iron nanoparticles and their forms (Fe, Fe₃C) resulted from ferrocene decomposition. The amount of nanotubes increases with iron content released from ferrocene catalyst during the pyrolysis process. Fe₃C nanoparticles drive the nucleation and the growth of carbon nanotubes during the pyrolysis process. Long (up to microns) well-defined MWNTs with small defects, ropes and disordered carbon are representatives in the pyrolyzed resins composition.     

Large diameter MWNTs growth on iron-sprayed catalyst by CCVD method under atmospheric pressure

In this work, we have synthesized large diameter multi-walled carbon nanotubes (MWNTs), by simple catalyst chemical vapor deposition (CCVD). Fe powder was spread on quartz substrate as a catalyst by a simple method and then heated under Ar atmosphere. Carbon’s products can be synthesized by the decomposition of ethylene gas and deposition of carbon atoms on the Fe catalyst particles in Ar atmosphere at 930°C. XRD pattern, SEM and TEM images were used to investigate the characteristics, morphology and structure of carbon’s products.     

The role of precursor gases on the surface restructuring of catalyst films during carbon nanotube growth

Catalyst films undergo considerable surface morphology restructuring prior to carbon nanotube nucleation, deeply influencing the nanostructures obtained. Here we study the influence of different gaseous atmospheres on the structure of thin Fe films. The morphology is influenced by process temperature and substrate interactions and varying the gas type and pressure can control the average catalyst island height.     

The synthesis of carbon coils using catalyst arc discharge in an acetylene atmosphere

Novel carbon coils were synthesized by an arc discharge process on a metal plate under different gas pressures from 160 to 460 Torr. The morphology and yield of carbon coils were examined by scanning (SEM) and transmission (TEM) electron microscopy. The influence of the gas pressure and impurities such as sulfur and phosphorus on the growth of product is also discussed. It was demonstrated that the morphology and yield of the coils were greatly controlled by the gas pressure. On the other hand, a new model was proposed to describe the coil growth. Our method offers a preferable alternative for the efficient, abundant and economical growth of carbon coils.     

A continuous synthesis of carbon nanotubes by dc thermal plasma jet

In this contribution we present a dc thermal plasma jet route for the continuous synthesis of single- and multi- walled carbon nanotubes. Our findings show the as produced product to be dependent on the plasma atmosphere and catalyst. Multi walled carbon nanotubes can be synthesized without a catalyst. Single walled carbon nanotubes require the presence of a catalyst (Ni-Ce) and the addition of hydrogen to the buffer gas. Increasing the amount of hydrogen added to the reaction significantly improves the nanotube yield. PACS 81.07.De; 36.40.Gk; 63.50.+x; 68.37.Lp; 68.37.Hk