Real-time observation of soot aggregate oxidation in an Environmental Transmission Electron Microscope

Sediako, Anton D.; Soong, Charles; Howe, Jane Y.; Kholghy, Mohammad Reza; Thomson, Murray J.

doi:10.1016/j.proci.2016.07.048

Cited by 60 publications

(29 citation statements)

References 16 publications

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“…Previous work has suggested that, under some conditions, soot can oxidize internally rather than at the surface through a process by which oxygen percolates into the particle and reacts with the less stable primary-particle core (Vander Wal et al 2007). Our study is consistent with a recent study that showed that mature soot tends to oxidize at the surface (Sediako et al 2017). Ouf et al (2016) have demonstrated that a small amount of surface oxidation can occur on ex situ samples of soot, even under conditions where atmospheric exposure is limited.…”

Section: Trends In Surface-maturity Level Derivedsupporting

confidence: 92%

Evolution of maturity levels of the particle surface and bulk during soot growth and oxidation in a flame

Johansson

Gabaly

Schrader

et al. 2017

Aerosol Science and Technology

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We performed a study of the evolution of soot composition and fine structure, i.e., maturity level, in an atmospheric ethylene-air diffusion flame. We used laser-induced incandescence (LII) to provide information about maturity level of the bulk primary particle and X-ray photoelectron spectroscopy (XPS) to provide complementary information about particle-surface-maturity level. The results demonstrate that the bulk material and the particle surface evolve separately in the flame. Increased soot-maturity level is associated with increased long-range order of the particle fine structure. This increased order leads to an increase in the absorption cross-section in the visible and near-infrared and a shift of the absorption to longer wavelengths with increasing maturity level of the bulk particle. These trends result in a decrease in the dispersion exponent (ξ) and increase in the absorption cross-section scaling factor (b), as inferred from LII measurements. LII measurements demonstrate that bulk-maturity level increases with height-above-the-burner (HAB) until it reaches a plateau in the center of the flame at the maximum in the soot volume fraction. Bulk-maturity level only slightly decreases as soot is oxidized at larger HABs. Increased maturity level also leads to an increase in long-range sp 2 hybridization. XPS measurements of the sp 2 /defect ratio demonstrate an increase in soot surface-maturity level with increasing HAB, but the surface-maturity level increases more gradually with HAB than the bulk-maturity level. Whereas the bulk-fine-structure order decreases slightly in the oxidation region, the surface order decreases dramatically, indicating that oxidation occurs preferentially at the surface under these conditions.

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Section: Trends In Surface-maturity Level Derivedsupporting

confidence: 92%

Evolution of maturity levels of the particle surface and bulk during soot growth and oxidation in a flame

Johansson

Gabaly

Schrader

et al. 2017

Aerosol Science and Technology

View full text Add to dashboard Cite

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“…High resolution transmission electron microscopy (HRTEM) images also showed fringe lengths increasing and interplanar distances decreasing with soot maturity and the flame temperature (Alfè et al, 2009;Kholghy et al, 2016;Alfè et al, 2010;Apicella et al, 2015). These observations have been interpreted as an indication that carbonisation processes are occurring from the outside in, which could impact the reactivity of these particles as well as the gas phase chemistry by evolving hydrogen (Heckman and Harling, 1966;Sediako et al, 2017).…”

Section: Introductionmentioning

confidence: 87%

Mechanical Properties of Soot Particles: The Impact of Crosslinked Polycyclic Aromatic Hydrocarbons

Pascazio

Martin

Botero

et al. 2019

Combustion Science and Technology

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“…[57] To achieve stable in situ heating experiments, a micro-electromechanical-system heating substrates (pn: HTN-0101H) from Norcada Inc was used, shown in Figure S1A (Supporting Information). The HF3300 ETEM employed in this study provided an exceptional platform for fully characterizing the material on one instrument pre and post pyrolysis-instead of requiring multiple other specialized instruments.…”

Section: Methodsmentioning

confidence: 99%

In Situ Mechanistic Elucidation of Superior Si‐C‐Graphite Li‐Ion Battery Anode Formation with Thermal Safety Aspects

Parekh

Sediako

Naseri

et al. 2019

Advanced Energy Materials

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understanding of the material synthesis/ fabrication, interfacial behavior, and thermal-chemical stabilities are vital. [3] With electronic appliances requiring stable voltage delivery, the current LIBs employ graphite or mixtures with soft carbons (carbon black) to achieve stable performance at discharge curves. [4] Since 1991, various forms of ordered and disordered (i.e., soft and hard) carbon have been primarily used as anode materials. [5] With graphitic carbon, a compromise was identified, which delivered a theoretical maximum capacity of 372 mAh g −1 , while maintaining stability and cycling characteristics. This stability comes at a cost of battery capacity, as it takes six carbon atoms to bind a single lithium ion (LiC 6 ) during charging process. [6] By contrast, alternative anode materials such as silicon, can bind about four lithium atoms (SiLi 4.4 ), improving energy densities by an order of magnitude. [7] Silicon anodes have garnered huge attention as they provide over ten times more theoretical capacity (3579 mAh g −1 ) than graphite anode. Problematically, the intercalated Si, Li 3.75 Si, swells in volume by about 320% during charging. Such huge volumetric expansion causes large material stresses, resulting in anode cracking, fracturing, loss of electrical contact (delamination), unstable solid electrolyte interface (SEI) and even catastrophic cell failure. [8][9][10][11] Naturally, this is unacceptable for practical and industrial applications. To overcome the capacity limitations of carbon, and the mechanical limitations of silicon, manufacturers have moved into composite materials-with the primary structure consisting of graphitic carbon, with silicon nanoparticles implanted within. First reported by Yoshio and co-workers in 2002, the C/Si composites did improve capacity, but the silicon nanoparticles were difficult to merge with the carbon bulk. [12,13] After repeated cycling, it was found that the particles separate and capacity drops. [14] Li et al. reported fabrication of graphite-Si composite using polymer blends of poly(diallyl dimethyl-ammonium chloride) and poly(sodium 4-styrenesulfonate) to obtain capacity of 450 mAh g −1 with 95% capacity retention after 200 cycles. [15] Zhang et al. prepared core-shell structure (Si@C) using silicon nanoparticles (Si-NPs) and emulsion polymerization of acrylonitrile, followed by pyrolysis. [16] The composite [15] retained A composite anode material synthesized using silicon nanoparticles, micrometer sized graphite particles, and starch-derived amorphous carbon (GCSi) offers scalability and enhanced electrochemical performance when compared to existing graphite anodes. Mechanistic elucidation of the formation steps of tailored GCSi composite are achieved with environmental transmission electron microscopy (ETEM) and thermal safety aspects of the composite anode are studied for the first time using specially designed multimode calorimetry for coin cell studies. Electrochemical analysis of the composite anode demonstrates a high initial discharge capaci...

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Real-time observation of soot aggregate oxidation in an Environmental Transmission Electron Microscope

Cited by 60 publications

References 16 publications

Evolution of maturity levels of the particle surface and bulk during soot growth and oxidation in a flame

Evolution of maturity levels of the particle surface and bulk during soot growth and oxidation in a flame

Mechanical Properties of Soot Particles: The Impact of Crosslinked Polycyclic Aromatic Hydrocarbons

In Situ Mechanistic Elucidation of Superior Si‐C‐Graphite Li‐Ion Battery Anode Formation with Thermal Safety Aspects

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