Synthesis of MWCNT Forests with Alumina-Supported Fe₂O₃ Catalyst by Using a Floating Catalyst Chemical Vapor Deposition Technique

Abstract

In this study, multiwalled CNT bundles were synthesized with an alumina-supported Fe2O3 catalyst by using a floating catalyst chemical vapor deposition (FCCVD) technique. The metal catalyst was synthesized by dispersing Fe2O3 on alumina support. Ethylene molecules were decomposed over different amounts of metal nanoparticles in a FCCVD reactor. The CVD temperature was elevated from 600°C to 1000°C. The large active surface area of the metal nanobuds promoted the decomposition of a carbon precursor and the fast growth of CNT bundles. Least dense bundles of varying heights were observed at lower CVD temperatures of 600°C and 700°C. At 800°C, CVD process conditions were found suitable for the fast decomposition of hydrocarbon. The relatively better yield of well-structured CNTs was obtained with a catalyst weight of 0.3 g at 800°C. Above 800°C, CNT forests start losing alignment and height. The forest density was also decreased at temperatures above the optimum. The elemental composition of CNT bundles revealed the presence of carbon, aluminium, oxygen, and iron in percentages of 91%, 0.76%, 8.2%, and 0.04%, respectively. A very small ID to IG ratio of 0.22 was calculated for CNTs grown under optimized conditions.

A review of thermal interface material fabrication method toward enhancing heat dissipation

“…The experimental set up for CVD involves hydrocarbon decomposition with the catalyst and gas decomposition. The growth process, which can be scaled, usually results in high production of high‐purity materials 78,79 . Material growth includes various forms, such as powder and film, and in terms of the types of catalyst, it can be well‐aligned, entangled, flaked, and layered 35 .…”

“…Therefore, the use of the method is advantageous due to the low cost of fabrication and optimize the production. The exploration of many nanomaterials can be achieved with flexible and practical modification methods. Therefore, these methods can be used with conductive nanomaterials, such as CNTs and Gr 79 …”

“…The growth process, which can be scaled, usually results in high production of high-purity materials. 78,79 Material growth includes various forms, such as powder and film, and in terms of the types of catalyst, it can be well-aligned, entangled, flaked, and layered. 35 During growth, the decomposition temperature ranges from 600 C to 1200 C within 15 to 60 minutes upon the completion of the reaction.…”

Supported Metal Oxide Catalysts for CO2 Fischer–Tropsch Conversion to Liquid Fuels─A Review

“…One deduction made is that the formation of carbides is stabilized in γ-alumina . A low-temperature alumina phase until the temperature range of 700–800 °C exhibited high surface areas of about 150–250 m 2 /g. , Phase transformation of γ-Al 2 O 3 to α-Al 2 O 3 further occurs when the calcination temperature was increased from 800 to 1300 °C, which decreases the specific surface area and the amount of tetrahedral Al 3+ sites . The improved thermal stability hinders thermal sintering by the synergistic stabilization effect, attributed as the “diffusion barrier effect”.…”

Effect of a Metallocene Catalyst Mixture on CNT Yield Using the FC-CVD Process

“…In the synthesis of carbon nanotubes (CNTs) by the FC-CVD method, metal catalyst, sulfur and carbon play an imperative role. For CNT synthesis, the use of transition metals (Fe, Co, Ni) [29][30][31][32] is common because of their high catalytic activity and high carbon diffusion rate through the metal [33]. In the FC-CVD method, metallocenes are typically used as the precursor of metal catalyst in the presence of argon and hydrogen as carrier gasses [33].…”