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EDX of the as-grown ACNTs at 825°C.
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Figure 4: EDX of the as-grown ACNTs at 825°C.

Mentions: Low magnification SEM images (Figure 2a, b) viewed from the lateral face and front face, respectively, depict a well-aligned array of nanotubes. Figure 3a-c shows the TEM images of CNTs grown at 825°C. It can be noticed in Figure 3b, c that amorphous carbon and metal particles are nearly absent. The magnified TEM image shows the high-density growth of CNTs having inner diameter ranging from 10 to 30 nm (Figure 3b). From TEM micrographs (Figure 3b), the approx CNT density was estimated to be of the order of 1011 nanotubes/cm2. The high-resolution TEM (HRTEM) images of the as-grown CNTs are shown in Figure 3c. The nanotube exhibits 16 concentric graphene cylinders for which the straight fringes indicate a high degree of crystallinity. HRTEM image reveals well-graphitized MWNT layers at d00.2 lattice spacing of 0.34 nm. Energy dispersive X-ray (EDX) (Figure 4) analysis of CNTs grown at 825°C revealed the iron content of 0.23 wt%, which is in agreement with our TEM observation that metal particle in our sample is negligibly small.

Scalable synthesis of aligned carbon nanotubes bundles using green natural precursor: neem oil

Kumar R, Tiwari RS, Srivastava ON - Nanoscale Res Lett (2011)

Bottom Line: High-resolution TEM analysis reveals these nanotubes to be multi-walled CNTs.These multi-walled CNTs were found to have inner diameter between 15 and 30 nm.It was found that present technique gives high yield with high density of bundles of ACNTs.

Affiliation: Nanoscience and Nanotechnology Unit, Department of Physics, Banaras Hindu University, Varanasi-221005, India. rstiwariphy@yahoo.com.

ABSTRACT
Practical application of aligned carbon nanotubes (ACNTs) would have to be determined by a matter of its economical and large-scale preparation. In this study, neem oil (also named Margoaa oil, extracted from the seeds of the neem--Azadirachta indica) was used as carbon source to fabricate the bundles of ACNTs. ACNTs have been synthesized by spray pyrolysis of neem oil and ferrocene mixture at 825°C. The major components of neem oil are hydrocarbon with less amount of oxygen, which provided the precursor species in spray pyrolysis growth of CNTs. The bundles of ACNTs have been grown directly inside the quartz tube. The as-grown ACNTs have been characterized through Raman spectroscopy, scanning and transmission electron microscopic (SEM/TEM) techniques. SEM images reveal that the bundles of ACNTs are densely packed and are of several microns in length. High-resolution TEM analysis reveals these nanotubes to be multi-walled CNTs. These multi-walled CNTs were found to have inner diameter between 15 and 30 nm. It was found that present technique gives high yield with high density of bundles of ACNTs.

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National Institutes of Health, Department of Health & Human Services
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