Carbon structure and the resulting graphitizability upon oxygen evolution

Abrahamson, Joseph P.; Jain, Abhishek; Duin, Adri C. T. van; Wal, Randy L. Vander

doi:10.1016/j.carbon.2018.04.055

Cited by 27 publications

(20 citation statements)

References 37 publications

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“…Pentagonal and heptagonal rings have been resolved by use of high resolution transmission electron microscopy (HRTEM) in microporous carbons and charcoal [19,23,54] as well as closed cages, and curved fragments in carbon heated to higher temperatures (>1500 • C) such as glassy carbon [20]. A recent review of the nanostructure of non-graphitising carbon, focusing on charcoal in particular, has also highlighted the role of oxygen in inhibiting planarisation of the structure [42] and experimental results have suggested the mechanism for pentagon integration is the loss of oxygenated fragments along the zig-zag edge of aromatic species [1].…”

Section: Introductionmentioning

confidence: 99%

Nanostructure of Gasification Charcoal (Biochar)

Martin

Nyadong

Ducati

et al. 2019

Environ. Sci. Technol.

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In this work, we investigate the molecular composition and nanostructure of gasification charcoal (biochar) by comparing it with heat-treated fullerene arc-soot. Using ultrahigh resolution Fourier transform ion-cyclotron resonance and laser desorption ionisation time of flight mass spectrometry, Raman spectroscopy and high resolution transmission electron microscopy we analysed charcoal of low tar content obtained from gasification. Mass spectrometry revealed no magic number fullerenes such as C 60 or C 70 in the charcoal. The positive molecular ion m/z 701, previously considered a graphitic part of the nanostructure, was found to be a breakdown product of pyrolysis and not part of the nanostructure. A higher mass distribution of ions similar to that found in thermally treated fullerene soot indicates that they share a nanostructure. Recent insights into the formation of all carbon fullerenes reveals that conditions in charcoal formation are not optimal for fullerenes to form, but instead curved carbon structures coalesce into fulleroid-like structures. Microscopy and spectroscopy support such a stacked, fulleroid-like nanostructure, which was explored using reactive molecular dynamics simulations. Highlights • Gasification charcoal (biochar) was analysed using high resolution mass spectrometry revealing no magic number fullerenes i.e. C 60 or C 70. • Heated fullerene arc-carbon also lacked magic number fullerenes but contained oxygenated fragments matching that of charcoal indicating a shared fulleroidlike nanostructure. • Raman spectroscopy and high resolution transmission electron microscopy supported a stacked, fulleroid-like nanostructure.

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Section: Introductionmentioning

confidence: 99%

Nanostructure of Gasification Charcoal (Biochar)

Martin

Nyadong

Ducati

et al. 2019

Environ. Sci. Technol.

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“…Anthracene (98+% purity was purchased from Alfa Aesar, Tewksbury, MA, USA) and sucrose (food grade sucrose of 99.9% purity obtained from Dunkin Donuts, State College, PA, USA) were selected as model graphitizing and non-graphitizing carbon precursors based on historical precedents [11,12,14,15].…”

Section: Materials Selectionmentioning

confidence: 99%

“…Heating duration and temperature were 5 h and 500 • C. Carbonization occurred under autogenous pressure (no pressure control), pressures reached~6.9 MPa. Additional details and a schematic of the reactor have been provided elsewhere [15].…”

Section: Carbonizationmentioning

confidence: 99%

Trajectories of Graphitizable Anthracene Coke and Non-Graphitizable Sucrose Char during the Earliest Stages of Annealing by Rapid CO2 Laser Heating

Abrahamson

Jain

Duin

et al. 2018

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The earliest stages of annealing of graphitizable anthracene coke and non-graphitizable sucrose char were observed by rapid heating with a CO 2 laser. Structural transformations were observed with transmission electron microscopy. Anthracene coke and sucrose char were laser heated to 1200 • C and 2600 • C for 0.25-300 s. The transformations are compared to traditional furnace heating at matching temperatures for a 1 h duration. Traditional furnace and CO 2 laser annealing followed the same pathway, based upon equivalent end structures. Graphitizable anthracene coke annealed faster than non-graphitizable sucrose char. Sucrose char passed through a structural state of completely closed shell nanoparticles that opened upon additional heat treatment and gave rise to the irregular pore structure found in the end product. The observed curvature in sucrose char annealed at 2600 • C results from shell opening. The initial presence of curvature and loss by heat treatment argues that odd membered rings are present initially and not formed upon heat treatment. Thus, odd membered rings are not manufactured during the annealing process due to impinging growth of stacks, but are likely present in the starting structure. The observed unraveling of the closed shell structure was simulated with ReaxFF.

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“…Sulfur is thermally stable in carbon at up to~1000 • C and thus, plays little role at the initial low temperature (500 • C) carbonization, whereas oxygen is released at temperatures as low as 300 • C [24,25]. Thus, oxygen removal impacts carbon at the earliest stages of carbon annealing [26,27]. The structural defects imparted on the carbon from oxygen removal set the stage for the trajectory of lamellae growth upon additional heat treatment, whereas in the case of sulfur, the lamellae are significantly annealed with trajectory set after heat treatment at 1000 • C. As such, sulfur imparts a relatively unobservable impact on the nanostructure, but rather, acts to cause micro-cracks upon release upon subsequent graphitization heat treatment, in the forms of H 2 S and CS 2 .…”

Section: Introductionmentioning

confidence: 99%

Carbon Nanostructure Curvature Induced from the Rapid Release of Sulfur upon Laser Heating

Abrahamson

Wal

2018

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Laboratory-generated synthetic soot from benzene and benzene-thiophene was neodymium-doped yttrium aluminum garnet (Nd:YAG) laser and furnace annealed. Furnace annealing of sulfur doped synthetic soot resulted in the formation of micro-cracks due to the high pressures caused by explosive sulfur evolution at elevated temperature. The heteroatom sulfur affected the carbon nanostructure in a different way than oxygen. Sulfur is thermally stable in carbon up to~1000 • C and thus, played little role in the initial low temperature (500 • C) carbonization. As such, it imparted a relatively unobservable impact on the nanostructure, but rather, acted to cause micro-cracks upon rapid release in the form of H 2 S and CS 2 during subsequent traditional furnace heat treatment. In contrast, Nd:YAG laser heating of the sulfur doped sample acted to induce curvature in the carbon nanostructure. The observed curvature was the result of carbon annealing occurring simultaneously with sulfur evolution due to the rapid heating rate.

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Carbon structure and the resulting graphitizability upon oxygen evolution

Cited by 27 publications

References 37 publications

Nanostructure of Gasification Charcoal (Biochar)

Nanostructure of Gasification Charcoal (Biochar)

Trajectories of Graphitizable Anthracene Coke and Non-Graphitizable Sucrose Char during the Earliest Stages of Annealing by Rapid CO2 Laser Heating

Carbon Nanostructure Curvature Induced from the Rapid Release of Sulfur upon Laser Heating

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