On heat conduction between laser-heated nanoparticles and a surrounding gas

Kuhlmann, S.-A.; Reimann, Jörg; Will, Stefan

doi:10.1016/j.jaerosci.2006.06.009

Cited by 61 publications

(33 citation statements)

References 68 publications

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“…Previous experimental investigations on the relationship between aggregate size and heat transfer have suggested that aggregate size and morphology have an effect on the conductive cooling rate and LII signal decay rate [78,110,111]. Reduced conductive cooling is associated with larger particle aggregates because of a shielding effect and effective reduction in surface area.…”

Section: Effects Of Morphology On the LII Signalmentioning

confidence: 99%

“…[75] None of these studies directly addressed the impact of coating-induced restructuring of the particle. Several studies have targeted the effects of aggregate size on LII signals via its influence on particle conductive-cooling rates [76][77][78][79][80] and optical properties [81,82], but none of these studies has addressed the effects of fractal dimension on LII.…”

Section: Introductionmentioning

confidence: 99%

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Effects of volatile coatings on the morphology and optical detection of combustion-generated black carbon particles.

Bambha¹,

Dansson²,

Schrader³

et al. 2013

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We have measured time-resolved laser-induced incandescence (LII) from combustion-generated mature soot extracted from a burner and (1) coated with oleic acid or (2) coated with oleic acid and then thermally denuded using a thermodenuder. The soot samples were size selected using a differential mobility analyser and characterized with a scanning mobility particle sizer, centrifugal particle mass analyser, and transmission electron microscope. The results demonstrate a strong influence of coatings particle morphology and on the magnitude and temporal evolution of the LII signal. For coated particles higher laser fluences are required to reach LII signal levels comparable to those of uncoated particles. This effect is predominantly attributable to the additional energy needed to vaporize the coating while heating the particle. LII signals are higher and signal decay rates are significantly slower for thermally denuded particles relative to coated or uncoated particles, particularly at low and intermediate laser fluences. 4 ACKNOWLEDGMENTSWe thank Daniel Strong for the rendition of the experimental setup shown in Fig. 1. We are very grateful to Chris Sorensen for his sage advice on fractal analysis. We also appreciate Alexei Khalizov's insightful comments about soot restructuring and Jeff Headrick's assistance with the TEM image analysis.

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Section: Effects Of Morphology On the LII Signalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of volatile coatings on the morphology and optical detection of combustion-generated black carbon particles.

Bambha¹,

Dansson²,

Schrader³

et al. 2013

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“…Some consensus has been reached that the TAC of mature soot falls in the range of about 0.2 to 0.4 (Snelling et al 2004;Maffi et al 2011;Kuhlmann et al 2006;Michelsen 2009). However, there have been no studies in the literature to investigate the TAC of incipient soot.…”

Section: Thermal and Optical Properties Of Incipient Sootmentioning

confidence: 99%

Investigation of the size of the incandescent incipient soot particles in premixed sooting and nucleation flames of n-butane using LII, HIM, and 1 nm-SMPS

Betrancourt

Liu

Desgroux

et al. 2017

Aerosol Science and Technology

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(2017) Investigation of the size of the incandescent incipient soot particles in premixed sooting and nucleation flames of nbutane using LII, HIM, and 1 nm-SMPS, Aerosol Science and Technology, 51:8, 916-935, DOI: 10.1080/02786826.2017 Laser-induced incandescence (LII) measurements were conducted to explore the ability of LII to detect small soot particles of less than 10 nm in two sooting flat premixed flames of n-butane: a socalled nucleation flame obtained at a threshold equivalence ratio F D 1.75, in which the incipient soot particles undergo only minor soot surface growth along the flame, and a more sooting flame at F D 1.95. Size measurements were obtained by modeling the time-resolved LII signals detected using 1064 nm laser excitation. Spectrally-resolved LII signals collected in the nucleation flame display a similar blackbody-like behavior as mature soot. Soot particle temperature was determined from spectrally-resolved detection. LII modeling was conducted using parameters either relevant to those of mature soot or derived from fitting the modeled results to the experimental LII data. Particle size measurements were also carried out using (1) ex situ analysis by helium-ion microscopy (HIM) of particles sampled thermophoretically and (2) online size distribution analysis of microprobe-sampled particles using a 1 nm-SMPS. The size distributions of the incipient soot particles, found in the nucleation flame and in the early soot region of the F D 1.95 flame, derived from time-resolved LII signals are in good agreement with HIM and 1 nm-SMPS measurements and are in the range of 2-4 nm. The thermal and optical properties of incipient soot were found to be not radically different from those of mature soot commonly used in LII modeling. This explains the ability of incipient soot particles to produce continuous thermal emissions in the visible spectrum. This study demonstrates that LII is a promising in situ optical particle sizing technique that is capable of detecting incipient soot as small as about 2.5 nm and potentially 2 nm and resolving small changes in soot sizes below 10 nm.

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“…This is only achieved if the energy uptake rate from absorption of the laser light exceeds the energy loss rate across the whole temperature range passed by the particle until eventually reaching the vaporisation temperature of the BC core. Heat conduction to the surrounding air is the main energy loss term during the phase when the bare BC core approaches vaporisation, while thermal radiation gives a negligible contribution at atmospheric pressure (Kuhlmann et al, 2006). The diameter of the BC core influences the competition between absorption of the laser light and heat conduction to the surrounding air, which are proportional to ∼ D 3 and to ∼ D 2 (or less), respectively (Bladh et al, 2008).…”

Section: Counting Efficiencymentioning

confidence: 99%

Technical Note: The single particle soot photometer fails to reliably detect PALAS soot nanoparticles

et al. 2012

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Abstract. The single particle soot photometer (SP2) uses laser-induced incandescence (LII) for the measurement of atmospheric black carbon (BC) particles. The BC mass concentration is obtained by combining quantitative detection of BC mass in single particles with a counting efficiency of 100 % above its lower detection limit. It is commonly accepted that a particle must contain at least several tenths of a femtogram BC in order to be detected by the SP2.Here we show the result that most BC particles from a PALAS spark discharge soot generator remain undetected by the SP2, even if their BC mass, as independently determined with an aerosol particle mass analyser (APM), is clearly above the typical lower detection limit of the SP2. Comparison of counting efficiency and effective density data of PALAS soot with flame generated soot (combustion aerosol standard burner, CAST), fullerene soot and carbon black particles (Cabot Regal 400R) reveals that particle morphology can affect the SP2's lower detection limit. PALAS soot particles are fractal-like agglomerates of very small primary particles with a low fractal dimension, resulting in a very low effective density. Such loosely packed particles behave like "the sum of individual primary particles" in the SP2's laser. Accordingly, most PALAS soot particles remain undetected as the SP2's laser intensity is insufficient to heat the primary particles to their vaporisation temperature because of their small size (D pp ≈ 5-10 nm). Previous knowledge from pulsed laser-induced incandescence indicated that particle morphology might have an effect on the SP2's lower detection limit, however, an increase of the lower detection limit by a factor of ∼ 5-10, as reported here for PALAS soot, was not expected.In conclusion, the SP2's lower detection limit at a certain laser power depends primarily on the total BC mass per particle for compact particles with sufficiently high effective density. By contrast, the BC mass per primary particle mainly determines whether fractal-like particles with low fractal dimension and very small primary particles are detectable, while their total BC mass has only a minor influence. This effect shifts the lower detection limit to much higher BC mass, or makes them completely undetectable. Consequently, care has to be taken when using the SP2 in applications dealing with loosely packed particles that have very small primary particles as building blocks.

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On heat conduction between laser-heated nanoparticles and a surrounding gas

Cited by 61 publications

References 68 publications

Effects of volatile coatings on the morphology and optical detection of combustion-generated black carbon particles.

Effects of volatile coatings on the morphology and optical detection of combustion-generated black carbon particles.

Investigation of the size of the incandescent incipient soot particles in premixed sooting and nucleation flames of n-butane using LII, HIM, and 1 nm-SMPS

Technical Note: The single particle soot photometer fails to reliably detect PALAS soot nanoparticles

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