Abstract
We propose the quantitative method of evaluating the purity of multiwall carbon nanotubes (MWCNTs) using Raman spectroscopy. High purity MWCNTs were prepared by chemical vapor deposition (CVD) to be used as a reference material with 100% purity. Since the intensity and wavenumber of D′′‐band located at around 1500 cm−1 were found to be independent of the excitation wavelength of a laser, the purity of MWCNTs was measured by comparing the intensity ratio of D′′‐band to G‐band (/IG) of the sample with that of a reference material. The established method was verified by testing the mixture of amorphous carbon particles and reference MWCNTs.
Highlights
Since multiwall carbon nanotubes (MWCNTs) possess high electrical conductivity, high thermal conductivity, and excellent mechanical properties [1,2,3], they have been extensively studied for being used in the electrical, thermal, and mechanical applications [4,5,6,7]
Most of the catalyst particles are residing inside MWCNTs after the synthesis [20], which does not affect Raman spectrum
This high purity MWCNTs could be considered as a reference material with 100% purity
Summary
Since multiwall carbon nanotubes (MWCNTs) possess high electrical conductivity, high thermal conductivity, and excellent mechanical properties [1,2,3], they have been extensively studied for being used in the electrical, thermal, and mechanical applications [4,5,6,7]. In order to achieve better characteristics of application products, the advancement in the synthesis technology has been tried to improve the properties of MWCNTs, including crystallinity, dispersibility, and purity [8,9,10]. Among these characteristics, purity is one of the most important properties from the viewpoint of better performance of application products. Apart from the fact that the intensity and position of D-band peak are varied with the excitation wavelength of a laser to a great extent [15], D-band originates from amorphous carbon particles and nanotube-related aspects including defects in the curved graphene sheets, tube ends, and finite size of crystalline domains of the tubes [16]. We propose here the quantitative method evaluating the purity of MWCNTs using the D-band Raman spectrum of MWCNTs as a signal for amorphous carbon particles
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