Characterization of flame-generated 2-D carbon nano-disks

Minutolo, P.; Commodo, Mario; Santamarı́a, Alexander; Falco, Gianluigi De; D’Anna, Andrea

doi:10.1016/j.carbon.2013.10.073

Cited by 61 publications

(38 citation statements)

References 49 publications

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“…As discussed earlier, the reasons why they have an almost atomic-thick and disk-like shape may be the particle molecular structure and the deposition/sampling procedure. Indeed, these compounds are probably small, defective graphene-like sheets, which have a crumbled, three-dimensional shape in the aerosol phase due to the possibility of twisting and bending around nonaromatic bonds at the high temperatures of the flame, but they assume a plane, atomic-thick morphology when they collide and deposit on the mica support (Minutolo et al 2014). It is worth noting that moving from the less rich flames (F D 1.85 and 1.89) where the particles typically have a height of about 0.45 nm, i.e., they are atomically thick, to the flames with F D 1.95, the particle height increases to 0.70 nm, thus indicating the formation of stacked molecular clusters.…”

Section: Morphology Analysismentioning

confidence: 99%

“…Even so, particle height is always much lower than particle base diameter showing that the shape of the particles collected on the sampling plate is not spherical. In order to obtain results that may be compared to the diameter of the particles measured in aerosol phase by scanning mobility particle sizer, the particle volume equivalent diameter was therefore calculated from the measured particle volume, under the hypothesis of a spherical shape (Minutolo et al 2014).…”

Section: Morphology Analysismentioning

confidence: 99%

“…Nascent carbon nanoparticles with equivalent diameter of about 2-4 nm are generated both in sooting conditions, where they coexist with larger primary soot particles and soot aggregates, and in less fuel-rich bluish flame conditions where they are formed alone or coexist with the larger 4-10 nm particles (Maricq 2004(Maricq , 2005Dobbins 2007;Commodo et al 2015). Nascent particles were reported to be liquid-like or bidimensional structures which assume an atomically thin disk-like shape when deposited on a substrate Dobbins 2007;Abid et al 2008;Minutolo et al 2014). Gas-phase precursors of freshly nucleated nanosized particles have been identified in polycyclic aromatic hydrocarbons (PAHs) (Ricther et al 2005; D'Anna 2009).…”

Section: Introductionmentioning

confidence: 99%

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Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

Falco

Commodo

Minutolo

et al. 2015

Aerosol Science and Technology

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Interaction forces acting between combustion-generated carbon particles were studied by using atomic force microscopy (AFM). To this aim, carbon nanoparticles were produced in fuelrich ethylene/air laminar premixed flames with different equivalent ratios F, and analyzed at a fixed residence time in the flame. Particles were collected on mica substrates by means of a thermophoretic sampling system and then analyzed by AFM. A characterization of particle dimension and morphology were performed operating AFM in semicontact mode, showing that the shape of the particles collected on a sampling plate is never spherical. Increasing the flame-equivalent ratio, particle shape moves from an almost atomically thick object to thicker compounds, indicating the transformation from particles made of small, defective graphene-like sheets to particles containing stacked aromatic layers. Attractive and adhesive forces between a titanium nitride probe and sampled particles were calculated from force-distance curves acquired in AFM force spectroscopy mode. Assuming that van der Walls forces are the main contribution to attractive forces, the measurement of attractive forces allowed the evaluation of the Hamaker constant for the carbon particles as a function of the flame-equivalent ratio. The comparison of the measured Hamaker constants with the values for benzene and HOPG, suggests a continuous increase of the aromatic domains and the three-dimensional order within the particles when the flame-equivalent ratio increases.

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Section: Morphology Analysismentioning

confidence: 99%

Section: Morphology Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

Falco

Commodo

Minutolo

et al. 2015

Aerosol Science and Technology

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“…1) reproduces typical signals of a high graphitic material with a narrow and marked G band at 1575 cm -1 and a less pronounced D band at 1360 cm -1 [24]. Conversely, the spectra of beech wood and Sulcis coal chars are characterized by a wide and pronounced D band that is an indication of the presence of defects and/or amorphous carbon [21,24]. The qualitative analysis of the Raman spectra suggests the presence of a more ordered molecular structure in the beech wood char than in the Sulcis coal char.…”

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confidence: 83%

“…A Raman spectroscopy analysis of graphite, beech wood char, and Sulcis coal char was carried out with a Horiba XploRA Raman microscope system following the procedure reported by Minutolo et al [21]. The Raman spectra were recorded in a is strong interest in developing novel thermoelectric materials, in particular for smart power generation.…”

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confidence: 99%

Thermoelectric properties of carbonaceous solids

Miccio¹

2016

Carbon letters

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The application of thermoelectric measurements to characterize carbonaceous materials, such as graphite and chars, can be helpful for monitoring the chemical/physical evolution of the material during gasification, which occurs upon steps of gas diffusion and heterogeneous chemical reactions at moderate and high temperature. The present article reports on an experimental study on the application of thermoelectric measurements for qualitative and semi-quantitative characterization of carbonaceous materials, such as graphite and chars, also in course of high temperature chemical conversion.Among carbonaceous fuels, graphite and cokes are poorly reactive, whereas the reactivity increases moving from coal to biomass derived chars (e.g., carbonized wood) [1]. To date, investigations have normally been carried out in thermo-balance, providing information on the weight loss of the sample during the test interval as well as on the evolution of gaseous products, when coupled with mass-spectrometry. In addition to the morphology and the degree of order at molecular level being relevant in determining the gasification reactivity of carbons, the presence of some elements in the ashes (e.g., alkalis) can accelerate the carbon conversion [2]. Conversely, high ash content has a negative impact because of the increased diffusional resistances and heat dispersion [3]. The enlargement of the porosity and the possible melting and coalescence of ash inclusions [4] are also correlated to some degree to the loss of reactivity. During carbon gasification tests in a thermo-gravimetric (TG) apparatus, the weight loss enables quantitative characterization of the fuel reactivity, but the internal structural evolution of the particles cannot be detected. Notably, it is difficult to perform on line measurements in the core of the oxidizing particle (for example, X-ray tomography to obtain a 3-D map of pores and materials) during conversion [5].The thermoelectric or Seebeck effect is the generation of an electromotive force (EMF) in a solid, when a gradient of temperature is established for any reason [6]. The thermoelectric effect is induced by the interactions between heat carriers in the solid and thermally excited electrons, leading to the accumulation of electrons and holes at the opposite sides of the body [7]. The ratio between the EMF, measured in μV, and the temperature difference is defined as the Seebeck coefficient [8], which in most cases is referred to as a temperature gap of 100 K. The Seebeck coefficient is an absolute property of a material; however, for practical reasons, it is usually referred to the property of a standard element, in most cases Pt. Technological applications of the Seebeck effect can be found in temperature measurements by thermocouples, in sensors for measuring gas concentration, and in micro-generation of electricity.The generated EMF depends on the temperature difference between the body ends as well as on the properties of the material. The thermoelectric effect of a pure material is the combination of...

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Graphitic‐Shell Encapsulation of Metal Electrocatalysts for Oxygen Evolution, Oxygen Reduction, and Hydrogen Evolution in Alkaline Solution

Khani

Grundish

Wipf

et al. 2019

Advanced Energy Materials

152

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Developing highly efficient, cost effective, and environmentally friendly electrocatalysts for the oxygen reduction (OER), oxygen evolution (ORR), and hydrogen evolution (HER) reactions is of interest for sustainable and clean energy technologies, including metal-air batteries and fuel cells. In this work, the screening of electrocatalytic activities of a series of single metallic iron, cobalt, and nickel nanoparticles and their binary and ternary alloys encapsulated in a graphitic carbon shell towards the OER, ORR, and HER in alkaline media is reported. Synthesis of these compounds proceeds by a two-step sol-gel and carbothermal reduction procedure. Various ex situ characterizations show that with harsh electrochemical This article is protected by copyright. All rights reserved. 2 activation, the graphitic shell undergoes an electrochemical exfoliation. The modified electronic properties of the remaining graphene layers prevent their exfoliation, protect the bulk of the metallic cores, and participate in the electrocatalysis. The amount of near-surface, higher-oxidation-state metals in the as-prepared samples increased with electrochemical cycling, indicating that some metallic nanoparticles are not adequately encased within the graphite shell. Such surface oxide species provide secondary active sites for the electrocatalytic activities. The Ni-Fe binary system gives the most promising results for the OER, and the Co-Fe binary system shows the most promise for ORR and HER.

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Characterization of flame-generated 2-D carbon nano-disks

Cited by 61 publications

References 49 publications

Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

Thermoelectric properties of carbonaceous solids

Graphitic‐Shell Encapsulation of Metal Electrocatalysts for Oxygen Evolution, Oxygen Reduction, and Hydrogen Evolution in Alkaline Solution

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