Diameter dependence of oxidative stability in multiwalled carbon nanotubes: Role of defects and effect of vacuum annealing
Diameter dependence of oxidative stability in multiwalled carbon nanotubes: Role of defects and effect of vacuum annealing
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DOI：
10.1063/1.3491022
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发表时间：
2010-10-15
影响因子：
3.2
通讯作者：
Giri, P. K.
中科院分区：
文献类型：
--
作者：
Singh, Dilip K.;Iyer, Parameswar K.;Giri, P. K.
虽然单壁碳纳米管的氧化稳定性已被广泛研究，但对多壁碳纳米管（MWNTs）中氧化稳定性的直径依赖性以及真空退火对这种稳定性的影响知之甚少。采用热重分析（TGA）方法对六组直径在5-100 nm范围内的样品在真空退火前后进行了系统的研究。高分辨率透射电子显微镜研究提供了证据的结构缺陷的纳米管壁。此外，它揭示了随着直径的增加，同心管之间的层间d-间距减小。实验TGA曲线被发现构成多个组件的氧化从反向S形拟合揭示。TGA曲线的分析表明，氧化温度遵循指数恢复函数与直径的增加，而分化的TGA谱的宽度减小。结果表明，小直径碳纳米管的氧化稳定性主要受晶格应变的控制，而大直径碳纳米管的氧化稳定性主要受碳纳米管壁缺陷的影响。在300-1000摄氏度温度范围内的高真空退火研究表明，在500摄氏度下退火的多壁碳纳米管的结构和氧化稳定性得到了重大改善。与单壁纳米管的结果进行了比较。所观察到的直径依赖性的基础上解释的应变在纳米管晶格和缺陷的纳米管壁。(C)2010年美国物理学会。[doi：10.1063/1.3491022]
While the oxidative stability of single walled carbon nanotubes has been studied extensively, very little is known about the diameter dependence of oxidative stability in multiwalled carbon nanotubes (MWNTs) and the effect of vacuum annealing on such stability. We have investigated six sets of samples with different diameters in the range of 5-100 nm systematically by thermogravimetric analysis (TGA) before and after vacuum annealing. High resolution transmission electron microscopy studies provide evidence for structural defects in the nanotube walls. Further, it reveals that with increasing diameter, interlayer d-spacing between concentric tubes decreases. Experimental TGA profile is found to constitute multiple components of oxidation as revealed from reverse Sigmoidal fitting. Analysis of the TGA profile shows that the oxidation temperature follows an exponential recovery function with increasing diameter, while width of the differentiated TGA spectra decreases. It is shown that oxidative stability of lower diameter MWNTs are primarily controlled by lattice strain, while that of large diameter MWNTs is decided by the defects in the nanotube wall. High vacuum annealing studies in the temperature range 300-1000 degrees C show major improvement in the structure and oxidative stability for MWNTs annealed at 500 degrees C. Results are compared with those of the single walled nanotubes. The observed diameter dependence is explained on the basis of strain in the nanotube lattice and defects in the nanotube walls. (C) 2010 American Institute of Physics. [doi:10.1063/1.3491022]