Catalytic Synthesis of Substrate-Free, Aligned and Tailored High Aspect Ratio Multiwall Carbon Nanotubes in an Ultrasonic Atomization Head CVD Reactor

Abstract

Chemical vapor deposition (CVD) method has proven its benchmark, over other methods, for the production of different types of carbon nanotubes (CNT) on commercial and lab scale. In this study, an injection vertical CVD reactor fitted with an ultrasonic atomization head was used in a pilot-plant scale (height 274 cm, radius 25 cm) for semicontinuous production of multiwall carbon nanotubes (MWCNTs). p-Xylene was used as a hydrocarbon precursor in which ferrocene was dissolved and provided the cracking catalyst. Atomization of the feed solution resulted in full and even dispersion of the catalytic solution. This dispersion led to the production of high aspect ratio MWCNTs (ranging from 8,000 to 12,000) at 850°C. Different experimental parameters affecting the quality and quantity of the produced CNTs were investigated. These included temperature, reaction time, and flow rate of the reaction and carrier gases. Different properties of the produced CNTs were characterized using SEM and TEM, while TGA was used to evaluate their purity. Specific surface area of selected samples was calculated by BET.

Enhanced Carbon Nanotubes Growth Using Nickel/Ferrocene-Hybridized Catalyst

“…This increment of the CNT height can be attributed to the higher decomposition rate of ferrocene at a higher temperature, which increases the catalytic effect of ferrocene. 16 The CNT height reaches a saturation point of 34.28 μm at 860 °C. As the temperature increases further to 880 °C, the CNT height reduces to 17.4 μm due to the encapsulation of catalyst nanoparticles by hydrocarbon precipitates, 38 as predicted by Bai et al.…”

“…As shown in Figure , the CNT height increases from 1.45 to 31.32 μm on the bare Si substrate as the growth temperature rises from 790 to 840 °C. This increment of the CNT height can be attributed to the higher decomposition rate of ferrocene at a higher temperature, which increases the catalytic effect of ferrocene . The CNT height reaches a saturation point of 34.28 μm at 860 °C.…”

“…13,14 For instance, crystalline CNTs with substantial height are needed for realizing an efficient bottom-up filling of the via holes in miniatured interconnects; 15 moreover, tall, high-aspect-ratio CNTs are required in field emission applications to achieve high emission current density. 16…”

“…Among the reported potential applications, there has been increasing interest in the application of CNTs in electronic interconnects due to their outstanding electrical conductivity. , At the same time, CNTs also show promise in field emission applications due to their exceptionally high aspect ratio and unique electrical properties . To integrate CNTs in these applications, tall CNT pillars with specified degree of crystallinity are needed. , For instance, crystalline CNTs with substantial height are needed for realizing an efficient bottom-up filling of the via holes in miniatured interconnects; moreover, tall, high-aspect-ratio CNTs are required in field emission applications to achieve high emission current density …”

Frictional Behaviour of Composite Anodized Layers on Aluminium Alloys

“…Another hypothesis is the incomplete crystallization of alumina or due to unexpected temperature variation during the melting/crystallization of alumina during MAO process [ 28 , 29 ]. This is partially confirmed by the results of Ali et al [ 30 ], who have proved that anodizing aluminium begins at lower temperatures with the formation of the η-Al 2.667 O 4 phase, and at higher temperatures it rebuilds into Al 2 O 3 phase.…”