Continuous observation of deposition processes by controlled atmosphere electron microscopy

Baker, Rose M.; Feates, F.S.; Harris, Peter

doi:10.1016/0008-6223(72)90412-5

Cited by 42 publications

(59 citation statements)

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“…As a consequence, low catalyst activity and faster catalyst poisoning result in low yield of the grown carbon nanospecies. The slowdown in the growth rate is attributed to progressive blocking of the active surface by excess carbon deposition on the front face of the catalyst particle [24]. At temperatures~700°C the catalyst activity is increased and the catalyst poisoning effect is delayed/suppressed thus effective growth time is increased which leads to higher yield.…”

Section: Influence Of Process Parametersmentioning

confidence: 99%

Morphology study of carbon nanospecies grown on carbon fibers by thermal CVD technique

Sharma

Lakkad

2009

Surface and Coatings Technology

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Section: Influence Of Process Parametersmentioning

confidence: 99%

Morphology study of carbon nanospecies grown on carbon fibers by thermal CVD technique

Sharma

Lakkad

2009

Surface and Coatings Technology

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“…CNTs are thought to be formed by a modified version of the vapour-liquid-solid mechanism proposed by Baker et al [21,22]. A vapoursolid-solid mechanism has been proposed where carbon dissociates on the surface of a catalyst particle, diffuses across its surface and finally precipitates in the form of CNTs [23].…”

Section: Introductionmentioning

confidence: 99%

Control of steam input to the pyrolysis-gasification of waste plastics for improved production of hydrogen or carbon nanotubes

Acomb

2014

Applied Catalysis B: Environmental

164

102

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Carbon nanotubes (CNTs) have been proven to be possible as high-value by-products of hydrogen production from gasification of waste plastics. In this work, steam content in the gasification process was investigated to increase the quality of CNTs in terms of purity.Three different plastics -low density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) were studied in a two stage pyrolysis-gasification reactor. Plastics samples were pyrolysed in nitrogen at 600°C, before the evolved gases were passed to a second stage where steam was injected and the gases were reformed at 800°C in the presence of a nickelalumina catalyst. To investigate the effect that steam plays on CNT production, steam injection rates of 0, 0.25, 1.90 and 4.74 g h -1 were employed. The CNTs produced from all three plastics were multiwalled CNTs with diameters between 10 and 20 nm and several microns in length. For all the plastic samples, raising the steam injection rate led to increased hydrogen production as steam reforming and gasification of deposited carbon increased. High quality CNTs, as observed from TEM, TPO and Raman spectroscopy, were produced by controlling the steam injection rate. The largest yield for LDPE was obtained at 0 g h -1 steam injection rate, whilst PP and PS gave their largest yields at 0.25 g h -1 . Overall the largest CNT yield was obtained for PS at 0.25 g h -1 , with a conversion rate of plastic to CNTs of 32% wt.

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“…Most of the investigators cited do not attribute the change of shape to melting or surface melting of catalyst nanoparticles, which could provide a plausible explanation. Long back, Baker et al [9] in their in situ experiments inside TEM using nickel catalyst and acetylene at 600°C have observed that there is change in shape of the catalyst during the growth of carbon nanofiber (CNF) and attributed it to vapor-liquidsolid (VLS) mechanism of growth. Their estimate of activation energy for growth is similar to the activation energy for diffusion of carbon in liquid nickel, and it has been inferred that the fiber growth is diffusion-controlled.…”

Section: Introductionmentioning

confidence: 97%

Growth and morphology of carbon nanostructures on nickel oxide nanoparticles in catalytic chemical vapor deposition

2014

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The present study explores the conditions favorable for the growth of cylindrical carbon nanostructures such as multi-walled carbon nanotube (MWCNT) and carbon nanofiber by catalytic chemical vapor deposition (CCVD) method using nickel oxide-based catalyst nanoparticles of different average sizes as well as different levels of doping by copper oxide. The role of doping and the average size have been related to the observed melting behavior of nanoparticles of nickel oxide by thermal and diffraction analysis, and the importance of melting has been highlighted in the context of growth of cylindrical nanostructures. In the reducing environment prevailing in the CCVD chamber due to decomposition of flowing acetylene gas at elevated temperature, there is extensive reduction of oxide nanoparticles. Lack of melting and faster flow of carbon-bearing gases favor the formation of a carbon deposit cover over the catalyst nanoparticles giving rise to the formation of nanobeads. Melting allows rapid diffusion of carbon from the surface to inside catalyst particles, and reduced flow of gas lowers the rate of carbon deposit, both creating conditions favorable for the formation of cylindrical nanostructures, which grows around the catalyst particles. Smaller particle size and lower doping favor growth of MWCNT, while growth of fiber is commonly observed on larger particles having relatively higher level of doping.

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Continuous observation of deposition processes by controlled atmosphere electron microscopy

Cited by 42 publications

References 0 publications

Morphology study of carbon nanospecies grown on carbon fibers by thermal CVD technique

Morphology study of carbon nanospecies grown on carbon fibers by thermal CVD technique

Control of steam input to the pyrolysis-gasification of waste plastics for improved production of hydrogen or carbon nanotubes

Growth and morphology of carbon nanostructures on nickel oxide nanoparticles in catalytic chemical vapor deposition

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