Soot particle size distributions in premixed stretch-stabilized flat ethylene–oxygen–argon flames

Camacho, J.J.; Singh, Ajay V.; Wang, Weijing; Shan, Ruiqin; Yapp, Edward Kien Yee; Chen, Dongping; Kraft, Markus; Wang, Hai

doi:10.1016/j.proci.2016.06.170

Cited by 36 publications

(22 citation statements)

References 38 publications

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“…Each series comprises three flames (labeled as a-c), making a total of 15 baseline CNP samples covering the volume median diameter of the primary particles from 4 to 23 nm (SI Appendix, section S1). In a stretch-stabilized flame, a premixed unburned mixture is issued from an aerodynamic nozzle, forming a radially diverging flow that impinges against a water-cooled surface (20). As depicted in Fig.…”

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confidence: 99%

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Flame-formed carbon nanoparticles exhibit quantum dot behaviors

Liu

Singh

Saggese

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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We examine the quantum confinement in the photoemission ionization energy in air and optical band gap of carbon nanoparticles (CNPs). Premixed, stretched-stabilized ethylene flames are used to generate the CNPs reproducibly over the range of 4-23 nm in volume median diameter. The results reveal that flameformed CNPs behave like an indirect band gap material, and that the existence of the optical band gap is attributed to the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap in the polycyclic aromatic hydrocarbons comprising the CNPs. Both the ionization energy and optical band gap are found to follow closely the quantum confinement effect. The optical band gaps, measured both in situ and ex situ on the CNPs prepared in several additional flames, are consistent with the theory and the baseline data of CNPs from stretched-stabilized ethylene flames, thus indicating the observed effect to be general and that the particle size is the single most important factor governing the variation of the band gap of the CNPs studied. Cyclic voltammetry measurements and density functional theory calculations provide additional support for the quantum dot behavior observed. carbon nanoparticles | quantum dots | flames N anosized carbon grains composed of disordered polycyclic aromatic hydrocarbons (PAHs) are one of the most abundant forms of carbon material in nature (1). As a less-celebrated allotrope of carbon in comparison with fullerenes, nanotubes, and graphene, carbon nanoparticle (CNP) has its share of importance in a wide range of physical phenomena. Studies of interstellar emission spectra suggest that PAH dust grains or CNPs are ubiquitous in the interstellar media (2-5); and they are considered as the tracer of the star formation process (3, 6). CNPs are formed in flames during incomplete combustion. They are part of the soot-formation process. Mature soot or atmospheric black carbon particles often contain both elemental and organic carbon, the relative amounts of which vary by source (7). Soot impacts the global and region climate systems (8, 9) because of its light-absorbing properties (10, 11) and also as cloud condensation nuclei (12). CNPs 10-20 nm in size or fine carbon particles are themselves abundant in diesel exhausts (13). Their light-absorption properties and impact on climate forcing remain poorly characterized (14). As a material, however, CNPs have found their applications in photovoltaic and electrochemical devices, including perovskite solar cells in which flame CNPs act as a hole transfer medium (15).In contrast to the notion that soot, young or mature with respect to its growth in flames, is a broadband light absorber, recent studies have shown that CNPs several nanometers in size have well-defined optical band gaps or band edges (16)(17)(18). The band gap arises from the energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the constituent PAHs (18,19). While previous studies (16-18) explored the vari...

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“…We measure the CNP size distribution function in gas extracted through a pinhole orifice on a circular probe imbedded in the stagnation surface plate by a mobility sizer (20,23). Fig.…”

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confidence: 99%

Flame-formed carbon nanoparticles exhibit quantum dot behaviors

Liu

Singh

Saggese

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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“…The twodimensional axisymmetric computation also used CHEMKIN to evaluate the chemical kinetic, thermal and transport aspects of the reacting flow. The reaction kinetic model considered for both computations was USC Mech II [20], which has been shown to calculate heat release rates and premixed stagnation flame structure more accurately than other foundational mechanisms [21,22].…”

Section: Methodsmentioning

confidence: 99%

“…For example, the strain rate was systematically decreased, in previous work, for a given unburned mixture to observe soot formation at increasing growth time [21]. The flame position will be measured by analyzing the flame projection captured by DSLR camera as described previously [21,23]. Premixed ethylene-oxygen-argon laminar flames doped with MMT precursor will be studied in the current work.…”

Section: Experimental Methodsmentioning

confidence: 99%

Synthesis of Manganese Oxide Nanoparticles in Premixed Flames

Dasappa¹,

Camacho²

2020

Preprint

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Synthesis of manganese oxide nanoparticles was carried out in premixed stagnation flames. The deposition surface was stationary to enable rigorous comparison to flame structure computations using pseudo one-dimensional and full two-dimensional calculations. The pseudo one-dimensional assumption taken by OPPDIF to calculate the flame structure performs reasonably well for the narrow aspect ratio stagnation flow currently studied. Agreement between the measured flame position and both computational methods was within 0.25 cm. The variation in manganese oxidation state in the products observed here is shown to be caused by competing oxidation and particle nucleation processes. Complimentary experimental and modeling studies of flame synthesis were carried out under well-defined boundary conditions to examine this competition. Manganese oxide products having II, II,III, III and IV valence were observed depending on the flame conditions. Unlike iron oxide and titanium oxide systems, complete oxidation to MnO2 is only observed for the most oxidizing growth conditions. The first observation of phase pure MnO by flame synthesis is reported here. Manipulation of the balance between manganese oxidation and particle nucleation through control of the time-temperature-oxygen history may enable selective synthesis of manganese oxide nanoparticles with tailored morphology and oxidation state.

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“…The setup, shown in Fig. 2, is similar to that used in previous studies of titania and soot formation [2,3,29]. An aerodynamic nozzle issues a laminar jet of TTIPdoped premixed C 2 H 4 /O 2 /Ar that impinges on a water-cooled stagnation plate.…”

Section: Introductionmentioning

confidence: 99%

A two-step simulation methodology for modelling stagnation flame synthesised aggregate nanoparticles

Lindberg

Manuputty

Akroyd

et al. 2019

Combustion and Flame

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A two-step simulation methodology is presented that allows a detailed particle model to be used to resolve the complex morphology of aggregate nanoparticles synthesised in a stagnation flame. In the first step, a detailed chemical mechanism is coupled to a one-dimensional stagnation flow model and spherical particle model solved using method of moments with interpolative closure. The resulting gas-phase profile is post-processed with a detailed stochastic population balance model to simulate the evolution of the population of particles, including the evolution of each individual primary particle and their connectivity with other primaries in an aggregate. A thermophoretic correction is introduced to the post-processing step through a simulation volume scaling term to account for thermophoretic transport effects arising due to the steep temperature gradient near the stagnation surface. The methodology is evaluated by applying it to a test case: the synthesis of titanium dioxide from titanium tetraisopropoxide (TTIP) precursor. The thermophoretic correction is shown to improve the fidelity of the post-process to the first fully-coupled simulation, and the methodology is demonstrated to be feasible for simulating the morphology of aggregate nanoparticles formed in a stagnation flame, permitting the simulation of quantities that are directly comparable to experimental observations.

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Soot particle size distributions in premixed stretch-stabilized flat ethylene–oxygen–argon flames

Cited by 36 publications

References 38 publications

Flame-formed carbon nanoparticles exhibit quantum dot behaviors

Flame-formed carbon nanoparticles exhibit quantum dot behaviors

Synthesis of Manganese Oxide Nanoparticles in Premixed Flames

A two-step simulation methodology for modelling stagnation flame synthesised aggregate nanoparticles

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