Carbon spherules: synthesis, properties and mechanistic elucidation

Pol, Vilas G.; Motiei, Menachem; Gedanken, Aharon; Calderón-Moreno, José Maria; Yoshimura, Masahiro

doi:10.1016/j.carbon.2003.10.005

Cited by 157 publications

(103 citation statements)

References 20 publications

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“…The current mechanism for sphere growth is consistent with the results found in earlier studies [7,29]. What is unusual is that the sizes of the spheres are uniform in diameter (refer to distribution plot).…”

Section: Characterisation Of Csssupporting

confidence: 89%

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Controlled syntheses of carbon spheres in a swirled floating catalytic chemical vapour deposition vertical reactor

Mhlanga

Coville

Iyuke

et al. 2010

Journal of Experimental Nanoscience

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Onion-like graphite structures, also called carbon spheres (CSs), represent another new allotropic nanophase of carbon materials, which can be potentially used as single electron devices, magnetic refrigerators, nanodiodes, nanotransistors, nanoball bearings, insulator lubricants as well catalyst supports. In this study, carbon nanospheres were synthesised in a vertical swirled floating catalytic chemical vapour deposition reactor for the first time. This process allows for continuous and large scale production of these materials. The CSs were obtained by the pyrolysis of acetylene in an inert atmosphere. The effect of pyrolysis temperatures and the flow rate of argon carrier gas on the size, quality and quantity of the synthesised CSs were investigated. Transmission electron microscope analysis of the carbon material revealed graphitic spheres with a smooth surface and a uniform diameter that could be controlled by varying reaction conditions (size: 50-250 nm). The materials were spongy with very low density. The CS production rate was found to increase with the increase in pyrolysis temperature (900-1000 C) and with flow rates of the carbon source (70-370 mL min À1 ) and carrier gas (70-480 mL min À1 ). Thermogravimetric analysis, powder X-ray diffraction and carbon, hydrogen and nitrogen analysis of the samples revealed that the products mainly contained CSs (98% carbon) and Raman spectroscopy revealed that the degree of graphitisation increased with the increase in pyrolysis temperature (900-1000 C).

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Section: Characterisation Of Csssupporting

confidence: 89%

“…This peak was found to be present even after post-heating of the CSs. At this stage the origin of this absorption is unknown and instrumental error is suspected [29].…”

Section: Effect Of C 2 H 2 Flow Rate and Temperaturementioning

confidence: 99%

Controlled syntheses of carbon spheres in a swirled floating catalytic chemical vapour deposition vertical reactor

Mhlanga

Coville

Iyuke

et al. 2010

Journal of Experimental Nanoscience

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“…7 The final disposition of these units depends on the precursor, heating treatment, feeding time and the interface between the carbon atoms and their surroundings during the thermal process. 7,35,36 Anyway, the exact role of the catalyst in the formation of spheres mediated by CVD procedures is not yet fully revealed. It seems that the FeNi 3 catalyst may act as a template, providing nucleation sites for the subsequent formation of spheres.…”

Section: Resultsmentioning

confidence: 99%

“…The accretion of spheres into clusters of several microns (see SI 5, ESI †) was described by Kroto et al for feeding times higher than 10 min, 34 or by Pol and co-workers as a result of cooling the system from high temperature to room temperature. 35 Anyway, it is worth noting that this coalescence is related to the presence of reactive dangling bonds on the surface, which gives them a high surface reactivity. 4,10 Indeed, the EDAX analysis of the sample revealed a carbon content of 93.2 atomic% and an oxygen content of 6.8%.…”

Section: Resultsmentioning

confidence: 99%

CVD synthesis of carbon spheres using NiFe-LDHs as catalytic precursors: structural, electrochemical and magnetoresistive properties

et al. 2016

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The gram-scale synthesis of carbon spheres with a diameter of ca. 740 nm has been achieved by means of a chemical vapour deposition method using NiFe-layered double hydroxides as a solid catalytic precursor. The presence of the catalyst (FeNi 3 ) allows controlling the final size distribution, resulting in a monodisperse sample. Their structural properties exhibited a high degree of graphitization according to their I D /I G ratio. In addition, their morphological features were unveiled by FIB-SEM and HRTEM, showing that they are formed by solid inner cores, and presenting labile chain-like structures due to accretion procedures. The solution and posterior sonication of the samples in toluene gave rise to the well-defined isolated spheres. The textural and electrochemical properties of the spheres have been tested showing non-mesoporous structures with a good behaviour as electrode materials for supercapacitors due to the presence of redox functionalities on their surface. Finally, magneto-transport measurements have been carried out, demonstrating semiconductor behaviour, as well as a positive magnetoresistance effect (ca. 72%) for the lowest studied temperature (2 K).

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“…In our recent publication we have discussed the synthesis of carbon spherules, its properties and the mechanism of its formation [9]. To the best of our knowledge there are no direct reports of the effect of applying a magnetic field on the synthesis of pure carbon bodies.…”

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confidence: 99%