Effect of growth temperature on the synthesis of carbon nanotube arrays and amorphous carbon for thermal applications

Abstract

Phone/Fax: þ86 10 623 32743Though carbon nanotube (CNT) arrays have tremendous potential due to their attractive mechanical, electrical, and thermal properties, the growth kinetics of CNTs are still not fully understood. Thus, we report on the effect of synthesis parameters, such as growth temperature, on the resulting arrays. In this work, CNT arrays were synthesized using catalytic chemical vapor deposition (CCVD) with furnace temperatures varying from 680 to 900 8C. Microscopy was used to investigate the effect of growth temperature on the structural properties, such as tube diameter, array length, and the amount of amorphous carbon produced at the top of the canopy as a growth by-product. Additionally, Raman spectroscopy was used to elucidate the effect growth temperature has on the resulting purity of the CNTs. It was then revealed that crystalline inhomogeneity exists along the length of the tubes with respect to crystallinity. Transmission electron microscopy (TEM) further determines the degree of tube crystallinity as well as the thickness of amorphous carbon coating around the nanotubes. Through both microscopy and spectroscopy, we found two distinct temperature regimes within the range of 680-900 8C. Below 800 8C, the growth of tube length and diameter remained relatively stagnant followed by a rapid growth rate above 800 8C with the highest tube crystallinity obtained within the regime of 800-840 8C. This indicates the presence of an important transitional temperature for CNT CCVD growth. Additionally, growth temperature was determined to play an important role in the amount of the resulting amorphous carbon by-product.

The Effect of Catalyst Sublimation Temperature on the Purity of Multi-Walled Carbon Nanotube Vertically Aligned Arrays

“…attempted to perform CVD at furnace temperatures below 800ºC which resulted in a low yield of CNTs and lumps of amorphous carbon, this aligns with Quang's findings for ideal growth temperatures [65]. Carbon diffusibility and solubility within Fe drives the resulting nucleation and growth of the MWCNTs.…”

Reduction of short wavelength reflectance of multi-wall carbon nanotubes through ultraviolet laser irradiation

“…VACNT growth is initially randomly oriented, until the growth forces a self-oriented vertical alignment. 11,17 Crust layers of tangled CNTs 17 and of amorphous carbon 18,19 can be formed on top of the VACNTs during growth. When the crust layer is removed so that incident radiation impinges directly on the VACNT surface, the reflectance of the VACNTs decreases.…”

Optimization of Carbon Nanotube-Coated Monolith by Direct Liquid Injection Chemical Vapor Deposition Based on Taguchi Method

“…The measurement for disordered carbon was evaluated using Raman spectroscopy by WITec Raman Microscope model Alpha 300R at 531.861 nm excitation wavelength within spectrum range about 100.36-3736.45. [38,39,[42][43][44][45] The flowchart of the experimental procedures of the CNT monolith is depicted in Figure 11. The particle size and the size of distribution of the CNT monolith were characterized using FESEM by Thermo Scientific NovaNano 230 at 100k magnification and atomic composition by energy-dispersive X-ray (EDX) by Oxford Instruments which was attached to the FESEM.…”