A Flame Structure Approach for Controlling Carbon Nanotube Growth in Flame Synthesis

Zainal, Muhammad Thalhah; Yasin, Mohd Fairus Mohd; Wahid, Mazlan Abdul; Sies, Mohsin M.

doi:10.1080/00102202.2019.1694518

Cited by 7 publications

(8 citation statements)

References 30 publications

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“…For each case, a wire mesh geometry is integrated within the simulation domain at 13 mm height above burner (HAB) to mimic the placement of wire mesh substrate inside the flame during the flame synthesis experiment. Previous study neglects the presence of wire mesh insertion into the flame with the assumption of negligible effects toward the flame flow field [11]. However, the same assumption cannot be applied in the present study as the wire mesh employed in the experiment significantly alters the flame shape.…”

Section: Experimental Conditions and Numerical Models 21 Experimental Conditionsmentioning

confidence: 97%

“…The coupled computation of the growth rate model and the flame model is based on the published model by Zainal et al, [11]. A previous experimental study by Hamzah [19] shows that the location of wire mesh will affect the CNT growth region.…”

Section: Cnt Growth Region Validation Of Flame Under Wire Meshmentioning

confidence: 99%

“…Previous flame synthesis experiments showed that an increase in inlet oxygen concentration improves CNT growth [15,16]. A previous study pointed out that an increase in oxygen concentration provides more combustion and thus larger high temperature region [11]. In relation to this, Zhang et al, [17] mentioned that availability of abundant high temperature within the flame results in CNT with better quality and improved yield.…”

Section: Introductionmentioning

confidence: 98%

“…In a flame structure, the flame temperature and species concentration are linked by the mixture fraction, utilized to identify the potential CNT growth region. A previous study employed a flame structure analysis to describe the CNT growth region in inverse diffusion flame with methane and ethylene gas mixture as the fuel source [11]. However, only a few studies relate the flame structure with CNT production [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the published CFD modeling and relevant experimental investigations have not included a detailed study of the influence of external heat source on CNT growth [9,11]. In the present study, a thorough validation of the coupled CFD-growth rate model computation will first be carried out.…”

Section: Introductionmentioning

confidence: 99%

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The Influences of Oxygen Concentration and External Heating on Carbon Nanotube Growth in Diffusion Flame

Zainal

Yasin

et al. 2021

CFDL

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Tight control of the carbon nanotube (CNT) synthesis process in flames remains a challenge due to the highly non-uniform gradient of flame thermochemical properties. The present study aims to establish a baseline model for flame-enhanced chemical vapor deposition (FECVD) synthesis of CNT and to analyze the CNT growth region at varying flame and furnace conditions. The numerical model comprises a computational fluid dynamics (CFD) simulation that is coupled with the CNT growth rate model to simulate the flow field within the furnace and the CNT growth respectively. Validation of the flame shape, flame length, and temperature profile are carried with a reasonable comparison to experimental measurements. A parametric study on the effects of furnace heating capacity and oxidizer concentration is conducted. The results of the CNT growth rate model reveal that there is a positive correlation between the heater power and CNT length. Supplying a higher concentration oxidizer at a fixed furnace power is predicted to result in further improvement in CNT length and high yield region. Flame structure analysis showed that with the heater turned on at 750 W (corresponding to heat flux of 21,713W/m2), the growth region expands twofold when oxygen concentration is increased from 19% to 24%. However, the growth region shrinks when the oxygen concentration is further increased to 27% which indicates depletion of carbon source for CNT growth due to excess oxygen. The finding of this research could guide and optimize the experiment of the flame-assisted CNT production in the future.

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Section: Experimental Conditions and Numerical Models 21 Experimental Conditionsmentioning

confidence: 97%

Section: Cnt Growth Region Validation Of Flame Under Wire Meshmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Influences of Oxygen Concentration and External Heating on Carbon Nanotube Growth in Diffusion Flame

Zainal

Yasin

et al. 2021

CFDL

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Carbon precursor analysis for catalytic growth of carbon nanotube in flame synthesis based on semi-empirical approach

et al. 2020

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Although flame synthesis promises economic benefit and rapid synthesis of carbon nanotube (CNT), the lack of control and understanding of the effects of flame parameters (e.g., temperature and precursor composition) impose some challenges in modelling and identifying CNT growth region for obtaining better throughput. The present study presents an investigation on the types of carbon precursor that affect CNT growth region on nickel catalyst particles in an ethylene inverse diffusion flame. An established CNT growth rate model that describes physical growth of CNT is utilised to predict CNT length and growth region using empirical inputs of flame temperature and species composition from the literature. Two variations of the model are employed to determine the dominant precursor for CNT growth which are the constant adsorption activation energy (CAAE) model and the varying adsorption activation energy (VAAE) model. The carbon precursors investigated include ethylene, acetylene, and carbon monoxide as base precursors and all possible combinations of the base precursors. In the CAAE model, the activation energy for adsorption of carbon precursor species on catalyst surface E-a,E-1 is held constant whereas in the VAAE model, E-a,E-1 is varied based on the investigated precursor. The sensitivity of the growth rate model is demonstrated by comparing the shi ing of predicted growth regions between the CAAE model and the VAAE model where the CAAE model serves as a control case. Midpoint-based and threshold-based techniques are employed within each model to quantify the predicted CNT growth region. Growth region prediction based on the midpoint-VAAE approach demonstrates the importance of acetylene and carbon monoxide to some extent towards CNT growth. Ultimately, the threshold-VAAE model shows that the dominant precursor for CNT growth is the mixture of acetylene and carbon monoxide. A simplified reaction mechanism is proposed to describe the surface chemistry for precursor reactions with nickel catalyst where decomposition of the ethylene fuel source into acetylene and carbon monoxide is accounted for by chemisorption.

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Zero-dimensional model for the prediction of carbon nanotube (CNT) growth region in heterogeneous methane-flame environment

et al. 2023

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A Flame Structure Approach for Controlling Carbon Nanotube Growth in Flame Synthesis

Cited by 7 publications

References 30 publications

The Influences of Oxygen Concentration and External Heating on Carbon Nanotube Growth in Diffusion Flame

The Influences of Oxygen Concentration and External Heating on Carbon Nanotube Growth in Diffusion Flame

Carbon precursor analysis for catalytic growth of carbon nanotube in flame synthesis based on semi-empirical approach

Zero-dimensional model for the prediction of carbon nanotube (CNT) growth region in heterogeneous methane-flame environment

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