Quantification of nano-scale carbon structure by HRTEM and lattice fringe analysis

Abstract

An image analysis algorithm is applied to materialsfor characterization of solid-state structure on a nanometer scale using model carbon materials. Nanoscale carbons in the form of "soots" offer ease of demonstration while being relevant to human health and climate concerns. Demonstrated here is an image analysis algorithm applied to three nanoscaled carbon materials: a disordered soot, and two highly ordered soots featuring flat or curved atomic layer planes. Nanostructure parameters consisting of graphene layers' length and tortuosity are extracted from high-resolution transmission electron microscopy images. The algorithm is composed of two major parts: a) image processing that generates a skeletonized binary image, and b) characterization that generates statistics on length and tortuosity based on the skeletonized image of the graphene layers. Algorithm robustness for variations in image processing parameters of contrast and threshold is demonstrated by similarity of output distributions of disordered diesel engine produced soot. Algorithm processing range was illustrated using highly ordered soots with flat (graphitic) and curved lattice nanostructure. Time resolved image analysis of an image sequence for polyhedral onions under electron irradiation demonstrate algorithm utility for tracking solid-state transformations.

Internal structure of soot particles in a diffusion flame

“…Interestingly, at the particle core the tortuosity of the fringes decreases and their degree of stacking increases. This could be due to thermally-driven graphitisation given the high temperatures and the possible lack of internal oxidation [13,56].…”

Influence of on-board produced hydrogen and three way catalyst on soot nanostructure in Gasoline Direct Injection engines

“…Soot nanostructure is related to particle formation history in the combustion chamber [14] and its dependent of the initial fuel [15]. Also, soot surface chemistry, which it is linked to soot's environmental and health impact, is dependent on its nanostructure [16,17]. Furthermore, soot reactivity, defined as the ease to oxidise mature soot [9], depends on its physicochemical properties.…”

“…The morphology, nanostructure, chemical functional groups and ash content has been reported to impact the soot oxidation characteristics [8,9,15,16,18,19], although there is no clear agreement about the contribution of each property [18]. In diesel engines, it is thought that soot properties can be altered, in order to produce a more reactive soot resulting in less demanding regeneration events in diesel particulate filters [8,9].…”

“…However, for GDI engine, the influence of EGR on nanostructure has not been documented yet. In this research, GDI soot nanostructure parameters (interlayer spacing, fringe length and fringe tortuosity) have been obtained following the methods used in the diesel literature [10][11][12]16]. For first time, the effect of high EGR percentages on GDI soot nanostructure has been assessed and compared to reformate gas exhaust recirculation (REGR) conditions.…”

Nanoscale Characteristics and Reactivity of Nascent Soot from n-Heptane/2,5-Dimethylfuran Inverse Diffusion Flames with/without Magnetic Fields

“…It was reported that the fringe length and tortuosity obtained from HRTEM images could change with a long exposure time of the electron beam irradiation [70]. Here this effect of the electron beam was ignored due to the short exposure time.…”