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.

An Electron Spin Resonance Study of Carbon Nanotubes Synthesized Using LaNi5 Alloy Micro-Particles as Catalyst

Multi-wall carbon nanotubes were synthesized from C₂H₂ by chemical vapor deposition (CVD) method using LaNi₅ alloy micro-particles with diameters ranging from 41 to 150 μm as catalyst. Electron spin resonance (ESR) spectra of purified carbon nanotubes were acquired at different temperatures between 100 and 290 K. The effects of the size of the catalyst particles used and addition of hydrogen gas during synthesis on the ESR characteristics (i.e., line shape, g-value and linewidth) of the produced nanotubes were investigated. It was found that the g-values of the produced nanotubes increase with their diameters: nanotubes having diameters between 10 and 20 nm (synthesized with catalyst particles having diameters between 41 to 50 μm) have an averaged g of 2.0400, while those having diameters between 70 and 120 nm (synthesized with catalyst particles having diameters between 100 to 150 μm) have an averaged g of 2.0898. It was also found that there is only one peak in the ESR spectra of carbon nanotubes with small diameters, while the nanotubes having larger diameters show two peaks, and the intensity of the additional peak increases with temperature.