On-line measurement of ultrafine aggregate surface area and volume distributions by electrical mobility analysis: I. Theoretical analysis

Lall, Anshuman A.; Friedlander, Sheldon K.

doi:10.1016/j.jaerosci.2005.05.021

Cited by 124 publications

(101 citation statements)

References 18 publications

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“…Here, the highest soot concentrations are found under fuelrich flame conditions. The overall soot volume can be computed from the SMPS number size distribution by accounting for the aggregate non-sphericity as in Lall and Friedlander (2006), assuming a soot primary particle diameter of 20 nm (Mamakos et al 2013). This soot volume is shown to correlate well with the bulk adiabatic flame temperature from chemical equilibrium calculations when the soot size exceeds 30 nm diameter (Figure 3).…”

Section: Soot Size and Concentrationmentioning

confidence: 99%

Mapping the Operation of the Miniature Combustion Aerosol Standard (Mini-CAST) Soot Generator

Moore

Ziemba

Dutcher

et al. 2014

Aerosol Science and Technology

107

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The Jing Ltd. miniature combustion aerosol standard (Mini-CAST) soot generator is a portable, commercially available burner that is widely used for laboratory measurements of soot processes. While many studies have used the Mini-CAST to generate soot with known size, concentration, and organic carbon fraction under a single or few conditions, there has been no systematic study of the burner operation over a wide range of operating conditions. Here, we present a comprehensive characterization of the microphysical, chemical, morphological, and hygroscopic properties of Mini-CAST soot over the full range of oxidation air and mixing N 2 flow rates. Very fuel-rich and fuel-lean flame conditions are found to produce organic-dominated soot with mode diameters of 10-60 nm, and the highest particle number concentrations are produced under fuel-rich conditions. The lowest organic fraction and largest diameter soot (70-130 nm) occur under slightly fuel-lean conditions. Moving from fuel-rich to fuel-lean conditions also increases the O:C ratio of the soot coatings from ∼0.05 to ∼0.25, which causes a small fraction of the particles to act as cloud condensation nuclei near the Kelvin limit (κ ∼ 0-10 −3 ). Comparison of these property ranges to those reported in the literature for aircraft and diesel engine soots indicates that the Mini-CAST soot is similar to real-world primary soot particles, which lends itself to a variety of process-based soot studies. The trends in soot properties uncovered here will guide selection of burner operating conditions to achieve optimum soot properties that are most relevant to such studies.

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Section: Soot Size and Concentrationmentioning

confidence: 99%

Mapping the Operation of the Miniature Combustion Aerosol Standard (Mini-CAST) Soot Generator

Moore

Ziemba

Dutcher

et al. 2014

Aerosol Science and Technology

107

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“…involve simplifying assumptions about the size distribution of the primary particles (often assumed to be monodisperse), the angular distribution of the primaries relative to the center of mass (often assumed to be uniform), the extent to which "inner" primary particles are shielded from interactions with the carrier gas by other primary particles in the agglomerate, and the transport regime (free molecular, continuum, transition) (SchmidtOtt et al 1990;Chakrabarty et al 2007;Lall and Friedlander 2006). Efforts have also been made to theoretically account for those dependencies (Naumann 2003).…”

Section: Introductionmentioning

confidence: 99%

Processing of Soot by Controlled Sulphuric Acid and Water Condensation—Mass and Mobility Relationship

Pagels

Khalizov

McMurry

et al. 2009

Aerosol Science and Technology

191

262

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. To simulate atmospheric processing, combustion soot agglomerates were altered by sulphuric acid vapor condensation, relative humidity (RH) cycling, and evaporation of the sulphuric acid and water by heating. Primary investigated properties were particle mobility size and mass. Secondary properties, derived from these, include effective density, fractal dimension, dynamic shape factor, and the mass fraction of condensed material. A transformation of the soot particles to more compact forms occurs as sulphuric acid and water condense onto fresh soot. The particle mass increases and initially the mobility diameter decreases, indicating restructuring of the soot core, likely due to surface tension forces. For a given soot source and condensing liquid, the degree of compaction depends strongly on the mass (or volume) fraction of condensed material. For water and sulphuric acid condensing on combustion soot, a mass increase of 2-3 times is needed for a transformation to spherical particles. In the limit of spherical particles without voids, the effective density then approaches the inherent material density, the fractal dimension approaches 3 and the dynamic shape factor approaches 1. Our results indicate that under typical atmospheric conditions, soot particles will be fully transformed to spherical droplets on a time scale of several hours. It is expected that the morphology changes and addition of soluble material to soot strongly affect the optical and hygroscopic properties of soot.

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“…The measured primary particle size as well as the measured agglomerate number distribution are introduced into the Lall et al (2006a) model. The agglomerate number concentration distribution as function of mobility diameter is corrected for the effect of the different charge distribution for chain like loose agglomerates compared with spheres using the Wen et al (1984a, b) model.…”

Section: Existing Technologies and Data Evaluation Proceduresmentioning

confidence: 99%

“…Due to unavoidable coagulation and unwanted or wanted sintering processes they often occur in form of loose agglomerates consisting out of primary particles touching each other in one point or sintered aggregates with stronger chemical bonds. In this paper we will not only consider loose agglomerates as has been done in the past (Lall and Friedlander, 2006a;Lall et al, 2006b;Wang et al, 2010), but we will consider data evaluation procedures for the structurally more complicated aggregates. Although the primary particles in agglomerates can have different shapes (spheres, fibers, plates) depending on the material and the synthesis process, very often they are spherical with diameters of a few nanometer to below 100 nm.…”

Section: Introductionmentioning

confidence: 99%

Rationale for Data Evaluation of the Size Distribution Measurements of Agglomerates and Aggregates in Gases with Extended SMPS-Technology

Fißan

Kaminski

Asbach

et al. 2013

Aerosol Air Qual. Res.

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Engineered nanoparticles (ENP) very often occur in form of agglomerates built up from spherical primary particles and sintered aggregates. The properties of materials making use of ENPs depend on the distributions of the structural properties of agglomerated/aggregated ENPs. The amount and structural properties of accidentally released ENPs are also of interest with regard to their transport and environmental effects.We report on the possibilities of using extended SMPS-technology with the addition of an Aerosol Particle Mass Analyzer (APM) and/or an Electrical Sensor (ES), as well as the results of recently developed sintering models, to describe the structures of agglomerates and aggregates. Proposals are made for suitable data evaluation procedures to yield accurate property distributions.

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On-line measurement of ultrafine aggregate surface area and volume distributions by electrical mobility analysis: I. Theoretical analysis

Cited by 124 publications

References 18 publications

Mapping the Operation of the Miniature Combustion Aerosol Standard (Mini-CAST) Soot Generator

Mapping the Operation of the Miniature Combustion Aerosol Standard (Mini-CAST) Soot Generator

Processing of Soot by Controlled Sulphuric Acid and Water Condensation—Mass and Mobility Relationship

Rationale for Data Evaluation of the Size Distribution Measurements of Agglomerates and Aggregates in Gases with Extended SMPS-Technology

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