以Y/Ni为催化剂制备的单壁碳纳米管的拉曼光谱研究

采用电弧放电法以Y/Ni为催化制备了单壁碳纳米管（SWNTs），对样品进行了扫描电镜、透射电镜和拉曼光谱的研究。所制备的样品中单壁碳纳米管的含量较高。对单壁碳纳米管的共振拉曼散射增强效应进行了观察，随激光波长的不同，单壁碳纳米管的拉曼光谱也随之变化，尤其是低频区径向呼吸模的变化比较明显。利用布里渊区折叠法计算了单壁碳纳米管的电子态密度曲线，根据SWNTs电子态密度尖峰之间的能量差、管子的直径和呼吸模频率建立了一个图表，并对SWNTs的呼吸模进行了归属。分析结果表明：样品中单壁碳纳米管的直径分布在0.79-1.76nm范围，金属管和半导体管均存在，并且直径在1.45nm附近的碳管居多。     

高质量单壁纳米碳管的CVD法合成及催化剂酸碱性对碳管生长的影响

采用燃烧法制备了Fe/Mo/MgO催化剂,用化学气相沉积法在1000℃下催化裂解甲烷制得了单壁纳米碳管.实验结果表明,550℃下焙烧的催化剂效果最好,适宜的酸碱性应该是催化剂具有较高活性的原因.用扫描电镜、透射电镜、高分辨透射电镜、热重分析和拉曼光谱等方法对制备的纳米碳管粗产品进行了表征.结果表明,该产物确为高质量单壁纳米碳管,其形态基本都以束状存在,且单壁纳米碳管直径分布较窄(0.85～1.22nm);对反应气氛的考察表明,CH4/N2=50/300为最佳,该气氛下所制得粗产物中单壁碳管的含量接近40%,经稀盐酸室温处理后,碳管含量可达到75%以上.     

TEM纳米云纹法测量纳米碳管变形

提出了透射电子显微镜(TEM)纳米云纹法的新技术,首次将该方法用于单根单壁碳纳米管的残余变形测量。纳米云纹由计算机显示器扫描线与碳纳米管束TEM图像干涉而成。该方法具有纳米级空间分辨率,可直接测量碳纳米管的力学性能。对TEM纳米云纹法的原理进行了详细的阐述,并利用不同管径的单壁碳管束产生了云纹。对直径为7.5nm的弯曲碳管束的残余变形进行测量,直接得到了其中一根直径为1.0nm的单壁碳管的残余变形场。实验结果证明了该方法的可行性。该方法为纳米尺度的碳管力学性能测量提供了新途径。     

用微米级LaNi5为催化剂生长的碳管的ESR谱研究

用微米级LaNi₅合金粉末为催化剂, 以乙炔为原料, 采用化学气相沉积(CVD)法合成了多壁碳纳米管. 在100~290 K温度下测量了41 μm≤d≤150 μm粒径催化剂制备的不同直径分布的碳纳米管的电子自旋共振（ESR）谱,研究了测量温度、微米级催化剂粒径及制备过程的氢气氛对生成的碳纳米管的ESR谱线型、g因子、线宽的影响. 发现碳纳米管的g因子随其直径的增大而增大,分别为2.040 0（催化剂粒径41 μm≤d≤50 μm, 碳纳米管的直径分布为10 nm到20 nm）和2.089 8（催化剂粒径100 μm≤d≤150 μm,碳纳米管的直径分布为70 nm到120 nm）. 发现小管径纳米管的ESR谱图有一个峰, 而大管径纳米管的ESR谱图有两个峰A和B, 且随测量温度的升高, 峰B强度增大.     

酞菁裂解法多壁碳纳米管的制备、表征和应用

为了探究高温处理酞菁钴对O2 的催化还原作用 ,以酞菁钴作为催化剂的前体 ,通过化学气相沉积的方法 ,在 85 0℃下 ,氩气与氢气混合气流中 ,制备了双层定向碳纳米管 ,纳米管的直径分布在 6 0～ 12 0nm ,长度约为4 0 μm ,在纳米碳管中包裹有直径为 10nm的钴颗粒 .所得产品用透射电子显微镜和扫描电子显微镜进行了观察 ,并用拉曼谱和X射线衍射对样品进行了表征 .通过循环伏安法测量得到纳米碳管对金属颗粒在酸性溶液中的腐蚀具有一定抵抗作用 .认为少量的N对于竹节状碳纳米管的形成和金属对酸的抵抗作用是十分必要的 ,每节中碳壁的弯曲弧度则与N在碳纳米管中含量和N与金属的相互作用有关 .另外 ,碳纳米管较大的电化学活性区域在电化学方面具有潜在的应用价值 .     

范德华力对双壁碳纳米管轴向压缩屈曲行为的影响

使用分子动力学方法研究几种不同半径尺寸的单壁碳纳米管组成的双壁碳管，预测了其初始稳定构型；分析了其自由弛豫阶段的特征；并模拟了它们在轴向压缩载荷作用下的屈曲行为；研究了不同层间距导致的范德华力变化对屈曲行为的影响.采用Tersoff-Brenner势描述单壁碳纳米管内原子间作用，Lennard-Jones势描述内外层间的范德华相互作用.计算结果表明：在通常意义下的双壁管间距(约0.34 nm)外还可以存在稳定的双壁碳管构型，并且这些新的稳定构型表现出了不同的力学性质. 关键词： 双壁碳纳米管 分子动力学 屈曲     

单壁碳纳米管的高压拉曼研究

采用金刚石对顶砧装置对直径分布在1.3 nm左右的单壁碳纳米管进行了高压拉曼光谱研究.实验结果表明随压力的增加碳管的截面形状发生了由圆到椭圆再到扁平的变化,这和我们之前的研究结果一致.从31 GPa卸压至常压后碳管的结构得到了较好的保持,这个压力值明显高于传统的Sp2键结构的碳材料所能稳定存在的压力范围(20 GPa以...     

金属铈催化剂对单壁纳米碳管生长和结构的影响

研究了一种利用新型催化剂制备单壁纳米碳管（SWNTs）的工艺方法.将金属铈的氧化物（Ce O₂）与石墨粉按一定比例混合，填充到已打好孔的石墨棒中制成复合石墨电极 ，以其为阳 极在高温氦电弧中实施电弧放电.放电后的生成物经高分辨透射电子显微镜（HRTEM）和拉曼 光谱(Raman)的观察及分析表明：生成物中含有大量呈束状存在的单壁纳米碳管，管径均匀 ，平均直径为120—132nm. 关键词： 单壁纳米碳管 电弧放电 透射电镜分析     

乙醇做碳源Mo-Co/MgO做催化剂合成单壁碳纳米管

本文采用柠檬酸法制备Mo-Co/MgO催化剂, 在小型流化床中, 以Ar气为载气直接携带乙醇蒸汽进入反应器, 通过化学气相沉积（CCVD）技术来合成制备单壁碳纳米管（SWCNTs）。利用扫描电镜和拉曼光谱方法研究了催化剂组分比例和载气流量等对SWCNTs制备的影响。研究结果表明: 以乙醇做碳源, Mo1-Co10/MgO做催化剂, Ar气流量为150sccm时制备的单壁碳纳米管质量最佳。     

CO2连续激光蒸发制备单壁碳纳米管及其Raman光谱的研究

讨论了在室温下用波长10.6μm的CO2连续激光制备单壁碳纳米管的工艺条件和生长机理.用大功率CO2连续激光蒸发制备单壁碳纳米管,所用激光功率400—900W,高分辨透射电镜观察表明单壁碳纳米管直径1.1—16nm,随着激光功率的增加稍微增加.本文还分别用波长为514.5nm和632.8nm激发光测量了CO2红外激光制备的单壁碳纳米管的一级和二级Raman光谱,发现在Raman特征峰的位置、强度上都存在差异.还将用CO2红外激光制备的单壁碳纳米管的Raman光谱与用YAG激光制备的单壁碳纳米管的Raman光谱进行了比较. 关键词： 单壁碳纳米管 CO2连续激光 Raman光谱     

Preparation of single-walled nanotubes with the help of a Ni/Cr-based catalyst

The high-yield synthesis of single-walled carbon nanotubes (SWNTs) is carried out in an electric-arc discharge using the Ni-Cr alloy as a catalyst. A new method of introducing the catalyst into the plasma hot region is used in the synthesis. In this method, the anode with a sandwich structure consists of two longitudinal graphite rods of a rectangular cross section, between which the Ni-Cr alloy in the form of a foil having a thickness approximately equal to 0.2 mm is placed. The obtained samples are investigated using transmission electron microscopy (TEM), Raman spectroscopy, and thermogravimetry. According to the results of TEM observations, SWNTs are tied into bundles with a length of several micrometers and a diameter of about 10 nm. The Raman spectra indicate that the diameter distribution of SWNTs lies between 1.2 and 1.5 nm with a peak at approximately 1.24 nm. The SWNT content in the obtained samples is approximately 20%. Heat treatment at various temperatures with a dosed air supply leads to a noticeable mass loss of the sample and to a change in its composition. For example, thus heating to 600 K causes a mass loss of about 40%, leading to an increase in the content of SWNTs up to 35% without their noticeable destruction. Further heating above 600 K leads to a virtually complete thermal decomposition of SWNTs.     

Comparative study on diameter distribution of single-walled carbon nanotubes using growth templates with different pore sizes: Zeolite-L,ZSM-5, and MCM-41

We report a comparative study on diameter distribution of single-walled carbon nanotubes (SWNTs) grown using nanoporous templates having different pore sizes, namely, zeolite-L, ZSM-5, and MCM-41. The change in the tube diameter based on catalytic film thickness and growth temperature was systematically investigated. We prepared very thin Fe catalyst films with nominal thicknesses of 0.5, 0.7, 1, and 2 Å, and the growth temperature was varied from 850 to 925 °C. We found that the SWNT mean diameter and size distribution width decreased with decreasing catalyst film thickness, growth temperature, and pore sizes of the templates. In addition, all SWNTs grown from the nanoporous templates have narrower diameter distribution compared to the SWNTs grown from SiO₂ planar surface. The obtained results are straightforward and suggest that the template growth has potential for SWNT growth with very narrow diameter distribution.     

Zinc oxide catalyzed growth of single-walled carbon nanotubes

We demonstrate that zinc oxide can catalyze the growth of single-walled carbon nanotubes (SWNTs) with high efficiency by a chemical vapor deposition process. The zinc oxide nanocatalysts, prepared using a diblock copolymer templating method and characterized by atomic force microscopy (AFM), were uniformly spaced over a large deposition area with an average diameter of 1.7 nm and narrow size distribution. Dense and uniform SWNTs films with high quality were obtained by using a zinc oxide catalyst, as characterized by scanning electron microscopy (SEM), Raman spectroscopy, AFM, and high-resolution transmission electron microscopy (HRTEM).     

Mono-dispersed single-walled carbon nanotubes made by using arc-burning method in nitrogen atmosphere

Single-walled carbon nanotubes made by using arc-burning technique in nitrogen atmosphere were dispersed in sodium cholate (SC) solution, and the diameter and chirality distribution of semiconductive SWNTs was investigated by UV-VIS-NIR and Raman spectroscopy, and photoluminescence mapping technique. In the typical formation condition, the diameter distribution of them is found to be relatively narrow (1.2 nm–1.4 nm in diameter), less chirality dependent, almost the same as the diameter distribution of SWNTs obtained by using laser-furnace technique.     

微孔对单壁纳米碳管储氢性能的影响

用巨正则蒙特卡罗分子模拟方法研究了单壁纳米碳管中的微孔即单壁纳米碳管基本孔-内管腔和管间孔对单壁纳米碳管储氢性能的影响.与低温下氮气吸附实验结果的比较发现单壁纳米碳管的内管腔是吸附的主要位置.分析单壁纳米碳管内管腔中吸附势的叠加和利用效率，发现管径为2nm左右时单壁纳米碳管内管腔的储氢容量最高.当单壁纳米碳管阵列的管间距增加时，单壁纳米碳管的管间孔也会成为有效的氢吸附位. 关键词： Monte Carlo方法 单壁纳米碳管 储氢 微孔     

Filling of single-walled carbon nanotubes by CuI nanocrystals via capillary technique

The present study is focused on the synthesis and investigation of the nanocomposite CuI@SWNT obtained by the filling of metallic single-walled carbon nanotubes (SWNTs) (inner diameter 1–1.4 nm) by wide-gap semiconducting CuI nanocrystals using so-called capillary technique. The method is based on the impregnation of pre-opened SWNTs by molten CuI in vacuum with subsequent slow cooling to room temperature. SWNTs and CuI@SWNT nanocomposites were studied by nitrogen capillary adsorption method, EDX microanalysis, HRTEM microscopy and Raman spectroscopy. The changing of electronic properties of CuI@SWNT as compare to row nanotubes was observed.     

碳纳米管中封装富勒烯的机理

利用经典分子动力学模型,发现C60进入单壁碳纳米管(SWNTs)形成(C60)n@SWNTs的吸入和俘获机理.揭示了吸入和俘获势垒只局域于SWNTs的管口区,而在SWNTs的管内区,C60沿管轴方向的运动几乎不受力.最后,系统地计算了吸入和俘获势垒随SWNTs管径的变化,发现只有当SWNTs的管径大于阈值1238nm时才能吸入C 关键词： 富勒烯相关材料 碳纳米管 类虹吸作用     

A detailed Raman study on thin single-wall carbon nanotubes prepared by the HiPCO process

The Raman spectrum of single wall carbon nanotubes (SWNTs) prepared by high pressure CO decomposition (HiPCO process) has been recorded at nine excitation laser energies ranging from 1.83 eV to 2.71 eV. The characteristic nanotubes features: G band, D band and radial breathing mode (RBM) have been analyzed and compared to those of an arc discharge SWNT material of similar diameter. A strong Breit-Wigner-Fano type (metallic) contribution to the G band was found in the spectra measured with green lasers, while spectra measured with red lasers indicate resonances of semiconducting SWNTs. Analysis of the energy dependence of the position of the D band revealed sinusoid oscillations superimposed on a linear trend. The validity of full DOS calculations for HiPCO materials has been confirmed by a match found between the estimated spectral contribution of metallic SWNTs as calculated from the components of the measured G band and as predicted by the (n, m) indexes of the major scatterers of DOS simulations. The RBM region of the HiPCO spectrum is more complex than usually observed for SWNTs. The analysis performed with a Gaussian distribution and improved fitting parameters leads to a mean diameter and variance of 1.05 nm and 0.15 nm, respectively. A bimodal Gaussian distribution had little influence on the error sum but reduced the standard error slightly. The major spectral features of the RBM could be interpreted using available resonance Raman theory. Received 5 February 2002 / Received in final form 3 April 2002 Published online 19 July 2002