Particle Morphology and Density Characterization by Combined Mobility and Aerodynamic Diameter Measurements. Part 2: Application to Combustion-Generated Soot Aerosols as a Function of Fuel Equivalence Ratio

Composition, shape factor, size, and fractal dimension of soot aerosol particles generated in a propane/O₂, flame were determined as a function of the fuel equivalence ratio (φ). Soot particles were first size-selected by a differential mobility analyzer (DMA) and then analyzed by an Aerodyne aerosol mass spectrometer (AMS). The DMA provides particles of known mobility diameter (d_m ). The AMS quantitatively measures the mass spectrum of the nonrefractory components of the particles and also provides the vacuum aerodynamic diam eter (d_va ) corresponding to the particles of known mobility diameter. The measured d_m, d_va , and nonrefractory composition are used in a system of equations based on the formulation presented in the companion article to estimate the particle dynamic shape factor, total mass, and black carbon (BC) content. Fractal dimension was estimated based on the mass-mobility relationship. Two types of soot particles were observed depending on the fuel equivalence ratio. Type 1: for φ < 4 (lower propane/O₂), d_va ; was nearly constant and independent of d_m . The value of d_va increased with increasing φ. Analysis of the governing equations showed that these particles were highly irregular (likely fractal aggregates), with a dynamic shape factor that increased with d_m and φ. The fractal dimension of these particles was approximately 1.7. These particles were composed mostly of BC, with the organic carbon content increasing as φ increased. At φ = 1.85, the particles were about 90% BC, 5% PAH, and 5% aliphatic hydrocarbon (particle density = 1.80 g/cm³). Type 2: for φ > 4 (high propane/O₂), d_va was linearly proportional to d_m . Analysis of the governing equations showed that these particles were nearly spherical (likely compact aggregates), with a dynamic shape factor of 1.1 (versus 1 for a sphere) and a fr actal dimension of 2.95 (3 for a sphere). These particles were composed of about 50% PAH, 45% BC, and 5% aliphatic hydrocarbons (particle density = 1.50 g/cm³). These results help interpret some measurement s obtained in recent field studies.     

Soot Particle Studies—Instrument Inter-Comparison—Project Overview

An inter-comparison study of instruments designed to measure the microphysical and optical properties of soot particles was completed. The following mass-based instruments were tested: Couette Centrifugal Particle Mass Analyzer (CPMA), Time-of-Flight Aerosol Mass Spectrometer—Scanning Mobility Particle Sizer (AMS-SMPS), Single Particle Soot Photometer (SP2), Soot Particle-Aerosol Mass Spectrometer (SP-AMS) and Photoelectric Aerosol Sensor (PAS2000CE). Optical instruments measured absorption (photoacoustic, interferometric, and filter-based), scattering (in situ), and extinction (light attenuation within an optical cavity). The study covered an experimental matrix consisting of 318 runs that systematically tested the performance of instruments across a range of parameters including: fuel equivalence ratio (1.8 ≤ φ ≤ 5), particle shape (mass-mobility exponent ( D _fm ), 2.0 ≤ D _fm ≤ 3.0), particle mobility size (30 ≤ d _m ≤ 300 nm), black carbon mass (0.07 ≤ m _BC ≤ 4.2 fg) and particle chemical composition. In selected runs, particles were coated with sulfuric acid or dioctyl sebacate (DOS) (0.5 ≤ Δ r _ve ≤ 201 nm) where Δ r _ve is the change in the volume equivalent radius due to the coating material. The effect of non-absorbing coatings on instrument response was determined. Changes in the morphology of fractal soot particles were monitored during coating and denuding processes and the effect of particle shape on instrument response was determined. The combination of optical and mass based measurements was used to determine the mass specific absorption coefficient for denuded soot particles. The single scattering albedo of the particles was also measured. An overview of the experiments and sample results are presented.     

Measurement of size-dependent dynamic shape factors of quartz particles in two flow regimes

Understanding and modeling the behavior of quartz dust particles, commonly found in the atmosphere, requires knowledge of many relevant particle properties, including particle shape. This study uses a single particle mass spectrometer, a differential mobility analyzer, and an aerosol particle mass analyzer to measure quartz aerosol particles mobility (d_m), vacuum aerodynamic, and volume equivalent diameters, mass, composition, effective density, and dynamic shape factor as a function of particle size, in both the free molecular and transition flow regimes. The results clearly demonstrate that dynamic shape factors can vary significantly as a function of particle size. For the quartz samples studied here, the dynamic shape factors increase with size, indicating that larger particles are significantly more aspherical than smaller particles. In addition, dynamic shape factors measured in the free-molecular (χ_v) and transition (χ_t) flow regimes can be significantly different, and these differences vary with the size of the quartz particles. For quartz, χ_v of small (d_m < 200 nm) particles is 1.25, while χ_v of larger particles (d_m ～ 440 nm) is 1.6, with a continuously increasing trend with particle size. In contrast, χ_t of small particles starts at 1.1 increasing slowly to 1.34 for 550 nm diameter particles. The multidimensional particle characterization approach used here goes beyond determination of average properties for each size, to provide additional information about how the particle dynamic shape factor may vary even for particles with the same mass and volume equivalent diameter.

© 2016 American Association for Aerosol Research     

An Inter-Comparison of Instruments Measuring Black Carbon Content of Soot Particles

Inter-comparison studies of well-characterized fractal soot particles were conducted using the following four instruments: Aerosol Mass Spectrometer-Scanning Mobility Particle Sizer (AMS-SMPS), Single Particle Soot Photometer (SP2), Multi-Angle Absorption Photometer (MAAP), and Photoacoustic Spectrometer (PAS). These instruments provided measurements of the refractory mass (AMS-SMPS), incandescent mass (SP2) and optically absorbing mass (MAAP and PAS). The particles studied were in the mobility diameter range from 150 nm to 460 nm and were generated by controlled flames with fuel equivalence ratios ranging between 2.3 and 3.5. The effect of organic coatings (oleic acid and anthracene) on the instrument measurements was determined. For uncoated soot particles, the mass measurements by the AMS-SMPS, SP2, and PAS instruments were in agreement to within 15%, while the MAAP measurement of optically-absorbing mass was higher by ～ 50%. Thin organic coatings (～ 10 nm) did not affect the instrument readings. A thicker (～ 50 nm) oleic acid coating likewise did not affect the instrument readings. The thicker (～60 nm) anthracene coating did not affect the readings provided by the AMS-SMPS or SP2 instruments but increased the reading of the MAAP instrument by ～ 20% and the reading of the PAS by ～ 65%. The response of each instrument to the different particle types is discussed in terms of particle morphology and coating material.     

Nanosize Effect on the Deliquescence and the Efflorescence of Sodium Chloride Particles

The deliquescence and efflorescence relative humidity values of 6- to 60-nm NaCl particles were measured using a tandem nano-Differential Mobility Analyzer. The deliquescence relative humidity (DRH) increased when the dry particle mobility diameter decreased below approximately 40 nm. The efflorescence relative humidity (ERH) similarly increased. For example, the DRH and ERH of 6-nm particles were 87% and 53%, respectively, compared to 75% and 45% for particles larger than 40 nm. Power law fits describing the nanosize effect are: DRH(d _m) = 213 d _m ^?1.6+ 76 and ERH(d _m) = 213 d _m ^?1.65+ 44, which are calibrated for 6 < d _m < 60 nm with less than 1% RH uncertainty and where d _m is the dry particle mobility diameter (nm). Two independent methods were used to generate the aerosol particles, namely by vaporizing and condensing granular sodium chloride and by electrospraying a high-purity sodium chloride aqueous solution, to investigate possible effects of impurities on the results. The DRH and ERH values were the same within experimental uncertainty for the particles generated by the two methods. The physical explanation for the nanosize effect of increasing DRH and ERH for decreasing dry particle mobility diameter is that the free energy balance of NaCl increasingly favors smaller particles (i.e., those without water) because the surface areas and hence surface free energies per particle are less for small, anhydrous particles than for bloated, aqueous particles. [Supplementary materials are available for this article. Go to the publisher's online edition of Aerosol Science and Technology for the following free supplemental resources: Graphs and data of the size distribution measurements of the deliquescence- and the efflorescence-mode experiments of the 6-, 8-, 15-, 20-, 30-, and 60-nm dry mobility diameter particles.]     

Characterization of structure of single particles from various automobile engines under steady-state conditions

The effective density ρ_eff of particles emitted from various types of automobile engines was measured using a differential mobility analyzer (DMA)–aerosol particle mass analyzer method, and their morphology was investigated via transmission electron microscopy analysis. The measured exhaust particles were particles emitted from diesel engines (DEs), gasoline direct injection spark ignition (DISI) engines, gasoline port fuel injection (PFI) engines, and liquefied petroleum gas (LPG) engines. ρ_eff and the morphology of the particles were measured after classification with the DMA, and six electrical mobility diameters D_m ranging from 30 to 300 nm were selected. ρ_eff was found to decrease as D_m increased for all particles. A morphological study showed that DE and DISI particles were mainly agglomerates and PFI and LPG particles were mainly nonagglomerates. Numbers and diameters of the primary particles in the agglomerates showed no systematic differences between DE and DISI particles at a given D_m. Rather, the primary particle diameter d_p increased with increasing D_m of the agglomerates; the empirical relationship between the two diameters was found to be d_p = 8.498ln(D_m) – 12.781 for DE and DISI particles. The core (elemental carbon) diameters in the primary particles of the DE particles increased as D_m increased and were estimated to range from 8.5 nm for D_m = 70 nm to 22.1 nm for D_m = 300 nm. Although the primary particle diameter and core diameter depend on D_m, the organic coating (shell) thickness, which ranged from 5.1 to 7.4 nm, was found to be independent of D_m.

Copyright © 2016 American Association for Aerosol Research     

Drag Force and Slip Correction of Aggregate Aerosols

The drag force on aggregate particles of uniform spheres was measured in a Millikan apparatus as a function of Knudsen number. Our experiment was designed to study the effect of particle orientation on the slip correction factor of nonspherical particles. The velocities of charged particles in a gravitational field with and without an applied electrical field were measured. An electrical field strength of 2000 V/cm was used to align doublet and triplet particles. Results showed that an aggregate particle moved in random orientation while in the gravitational field. The same particle moved with its polar axis parallel to the electric field (doublets) or with its plane of centers parallel to the electrical field (triangular triplets). Using a nonlinear regression method, both the dynamic shape factor and slip correction factor could be determined separately from the data. The dynamic shape factors at different orientations were in good agreement with those obtained previously in a sedimentation tank. The slip correction factor of singlet particles agreed with results previously obtained by Allen and Raabe for latex particles. Slip correction factors of doublets and triangular triplets can also be expressed in the Knudsen-Weber form: 1 + 2λ/d _a [1.142 + 0.558 exp(?0.999 d _a/2λ)]. The adjusted sphere diameter d _a was 1.21 d ₁ (primary diameter) for doublets moving parallel to the flow and 1.31 d ₁ for doublets randomly oriented. These results show that the slip correction factor of a nonspherical particle depends on the orientation and confirm the theory proposed by Dahneke.     

Effective Density and Volatility of Particles Emitted from Gasoline Direct Injection Vehicles and Implications for Particle Mass Measurement

The effective density and volatility of particulate emissions from five gasoline direct injection (GDI) passenger vehicles were measured using a tandem differential mobility analyzer (DMA) and centrifugal particle mass analyzer (CPMA) system. The measurements were conducted on a chassis dynamometer at three steady-state operating conditions. A thermodenuder was employed to find the volatility and mixing state of the particles as well as the effective density of nascent and non-volatile particles (defined as particle phase remaining after denuding at 200°C). The mass–mobility exponent ranged between 2.4 and 2.7 for nascent (or undenuded) particles and between 2.5 and 2.7 for non-volatile particles; higher than typical diesel soot. The effective density function was 4278d_m^?0.438 ± 76.3 kg/m³ (for mobility diameter, d_m, in nm) for nascent particles and 3215d_m^?0.395 ± 37.9 kg/m³ for non-volatile particles. The effective density functions of the non-volatile particles were fairly similar for the conditions studied. The uncertainty in using the effective density and mixing state data to determine the mass concentration of the aerosol by integrating mobility size distributions was examined. The uncertainty in mass concentration is minimized when only the non-volatile component is measured. However, the uncertainty in the mass concentration increases substantially if nascent particles are measured due to uncertainties in the particle mixing state and their associated effective densities. Furthermore, transient vehicle operation (cold-starts, accelerations, and decelerations) would likely change the mixing state of the exhaust particles suggesting it is difficult to accurately measure the mass concentration of undenuded GDI exhaust particulate using integrated size distribution methods.

Copyright 2015 American Association for Aerosol Research     

Formation of metal oxide nanoparticles in combustion of titanium and aluminum droplets

A study was performed of the formation of metal oxide nanoparticles during combustion of aluminum and titanium drops which moved in air at a velocity of up to 3 m/sec. The source of the burning particles was a pyrotechnic mixture which contained an oxidizer, a binder, and metal particles of size 4–350 μm. Transmission electron microscopic studies showed that the combustion products were 1–10 μm aggregates of fractal structure consisting of primary particles (spherules) of Al₂O₃/TiO₂ 5–150 nm in diameter. The Brownian diffusion of the aggregates and their motion in electric and gravitational fields were observed using videomicroscopic recording. The charge distribution of TiO₂ aggregates and the equivalent radius of Brownian mobility were determined. In Al combustion, the zone of nanoparticle formation is separated from the particle surface by a distance approximately equal to the particle radius, and in Ti combustion, this zone is located directly near the surface. Coagulation of the oxide aerosol in the track of a burning particle leads to aerogelation with the formation of huge aggregates. Analytical expressions for approximate calculation of the parameters of the oxide particles and zones of their formation are proposed. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 6, pp. 33–47, November–December, 2006.     

Studies on poly(vinyl chloride)-copper composites. Part 1: State of segregation of filler particles,electrical and mechanical properties in presence of plasticizer and stabilizer

The presence of additives influences the state of segregation of filler particles in the polymer matrix which in turn controls the electrical and mechanical properties of poly(vinyl chloride)-copper composites. The liquid plasticizer seems to form a coating on the filler surface which introduces quasirandomness in the segregated network. In accordance with the mathematical model proposed earlier, the strength properties were found to be proportional to d_m^?½ where d_m is the mean free path between the filler particles. Calculations of d_m were based on two different models, one for segregated network (unplasticized and low plasticized composites) and the other for quasi-random distribution of filler particles (plasticized composites). Extruded samples in general show more randomness in the filler distribution than the compression molded samples.     

High Precision Density Measurements of Single Particles: The Density of Metastable Phases

We describe a system designed to measure the size, composition, and density of individual spherical particles in real time. It uses a Differential Mobility Analyzer (DMA) to select a monodisperse particle population and the single particle mass spectrometer to measure individual particle aerodynamic diameter. Together the mobility and aerodynamic diameters yield particle density. The mass spectrometer aerodynamic sizing resolution d _{ν a} /Δ d _{ν a} is ～ 50 and > 100 for 200 nm and 800 nm particles respectively and together with the DMA the overall system resolution is 20. We demonstrate that the line shape of the aerodynamic size distribution can be used to identify asphericity. We present results from two operational schemes: one suitable for most applications, yielding particle density with a precision of ± 2.5%, and a high precision variant, that uses an internal calibrant to remove any of the systematic errors and significantly improves the measurement quality. The high precision scheme is most suitable for laboratory studies, making it possible to follow slight changes in particle density. An application of the system to measure the density of hygroscopic particles in deep metastable phases near zero relative humidity is presented. The density data presented here are consistent with conclusions reached in a number of other studies, namely, that some particle systems, once deliquesced, persist as droplets down to near zero relative humidity.     

Coating Mass Dependence of Soot Aggregate Restructuring due to Coatings of Oleic Acid and Dioctyl Sebacate

Soot particles in the atmosphere can be coated with organic or nonorganic material, which may affect particle morphology and optical properties. The effect of the mass of coating on the morphology of soot particles was studied using oleic acid and dioctyl sebacate (DOS) coatings. A wide range of coatings were used, with up to 10 times as much coating as the mass of the soot. It is shown that as the coating mass increases the degree of collapsing increases until the coating is so large that the soot particle becomes completely contained within a spherical droplet of the coating material. Higher amounts of coating will not cause further collapse of the particle. The degree of collapse is also a function of the initial size of the soot particle but was independent of the coating materials tested, which have similar surface tensions. A model is presented to predict the change in mobility diameter as a function of coating mass ratio. The effect of coating mass on effective density, shape factor, and fractal dimension is also reported.

Copyright 2013 American Association for Aerosol Research     

Relation between Electrical Mobility,Mass, and Size for Nanodrops 1–6.5 nm in Diameter in Air

A large number of data on mobility and mass have been newly obtained or reanalyzed for clusters of a diversity of materials, with the aim of determining the relation between electrical mobility (Z) and mass diameter d _m = (6m/ π ρ ) ^1/3 (m is the particle mass and ρ the bulk density of the material forming the cluster) for nanoparticles with d _m ranging from 1 nm to 6.5 nm. The clusters were generated by electrospraying solutions of ionic liquids, tetra-alkyl ammonium salts, cyclodextrin, bradykinin, etc., in acetonitrile, ethanol, water, or formamide. Their electrical mobilities Z in air were measured directly by a differential mobility analyzer (DMA) of high resolution. Their masses m were determined either directly via mass spectrometry, or assigned indirectly by first distinguishing singly (z = 1) and doubly (z = 2) charged clusters, and then identifying monomers, dimers, … n-mers, etc., from their ordering in the mobility spectrum. Provided that d _m > 1.3 nm, data of the form d _m vs. [z(1+m _g /m) ^1/2 /Z)] ^1/2 fall in a single curve for nanodrops of ionic liquids (ILs) for which ρ is known (m _g is the mass of the molecules of suspending gas). Using an effective particle diameter d _p = d _m + d _g and a gas molecule diameter d _g = 0.300 nm, this curve is also in excellent agreement with the Stokes-Millikan law for spheres. Particles of solid materials fit similarly well the same Stokes-Millikan law when their (unknown) bulk density is assigned appropriately.     

Characterization of Soot Aerosol Produced from Combustion of Propane in a Shock Tube

The knowledge of yields and properties of soot from combustion of hydrocarbon fuels is crucial for accurate evaluation of the impacts of primary aerosols on air quality and climate. This study presents measurements of soot generated from combustion of propane in a shock tube, using independently adjustable fuel equivalence ratio (φ), temperature, and pressure. The characterization of soot yields inside the shock tube by in situ laser extinction is complemented with a set of comprehensive measurements of soot transferred into a fluoropolymer chamber, including particle size distributions, elemental carbon (EC) mass fraction, effective density, mass fractal dimension (Dfm), dynamic shape factor (χ), and optical properties. The properties of soot particles and the soot yield are sensitive to combustion conditions and the duration of the combustion experiment. High-temperature combustion with φ = 2.5 produces small fractal (Dfm = 2) soot particles composed mainly of EC (up to 90%), at a low mass yield. Particles from lower temperature combustion contain a significant fraction of organic material (～50%). Using rich fuel mixtures (φ = 4.0 and 8.0) significantly increases particle size and soot mass yield. At lower temperatures, compact (Dfm = 3) and nearly spherical (χ = 1.1) aggregates with high organic content are formed, whereas at higher temperatures, the particles are fractal and closely resemble those obtained using φ = 2.5. Single scattering albedo (SSA) varies from 0.15 for fractal particles to 0.75 for compact particles. For soot generated at high equivalence ratios, SSA can be used as a proxy for particle morphology and EC content.

Copyright 2012 American Association for Aerosol Research     

A Granular Bed for Use in a Nanoparticle Respiratory Deposition Sampler

A granular bed was designed to collect nanoparticles as an alternative to nylon mesh screens for use in a nanoparticle respiratory deposition (NRD) sampler. The granular bed consisted of five layers in series: a coarse mesh, a large-bead layer, a small-bead layer, a second large-bead layer, and a second coarse mesh. The bed was designed to primarily collect particles in the small-bead layer, with the coarse mesh and large-bead layers designed to hold the collection layer in position. The collection efficiency of the granular bed was measured for varying depths of the small-bead layer and for test particles with different shape (cuboid, salt particles; and fractal, and stainless steel and welding particles). Experimental measurements of collection efficiency were compared to estimates of efficiency from theory and to the nanoparticulate matter (NPM) criterion, which was established to reflect the total deposition in the human respiratory system for particles smaller than 300 nm. The shape of the collection efficiency curve for the granular bed was similar to the NPM criterion in these experiments. The collection efficiency increased with increasing depth of the small-bead layer: the particle size associated with 50% collection efficiency, d₅₀, for salt particles was 25 nm for a depth of 2.2 mm, 35 nm for 3.2 mm, and 45 nm for 4.3 mm. The best-fit to the NPM criterion was found for the bed with a small-bead layer of 3.2 mm. Compared to cubic salt particles, the collection efficiency was higher for fractal-shaped particles larger than 50 nm, presumably due to increased interception.

Copyright 2015 American Association for Aerosol Research     

Particle Size Effect on CH4 Oxidation Over Noble Metals: Comparison of Pt and Pd Catalysts

Intrinsic catalytic activities (TOF values) in CH₄ complete oxidation under lean conditions were estimated as a function of Pt and Pd particle sizes (d_m) for two series of Pt/Al₂O₃ and Pd/Al₂O₃ catalysts. Comparison of TOF ~ f(d_m) relationships revealed significant difference between Pt and Pd catalysts. For Pt catalyst TOF showed tendency to increase by 2–3 times with increasing particle size from 1 to ca 3 nm and remained constant, when Pt particles became larger than 3 nm. On the other hand, for Pd catalyst TOF increased almost linearly when particle size grew from 1 to 20 nm. These different tendencies were attributed to the different mechanisms of CH₄ oxidation over Pt and Pd catalysts: Langmuir–Hinshelwood and Mars-Van Krevelen respectively.     

Laboratory and Ambient Particle Density Determinations using Light Scattering in Conjunction with Aerosol Mass Spectrometry

A light scattering module has been integrated into the current AMS instrument. This module provides the simultaneous measurement of vacuum aerodynamic diameter (d _va) and scattered light intensity (R_LS) for all particles sampled by the AMS above ～180 nm geometric diameter. Particle counting statistics and correlated chemical ion signal intensities are obtained for every particle that scatters light. A single calibration curve converts R_LS to an optical diameter (d _o). Using the relationship between d _va and d _o the LS-AMS provides a real-time, per particle measurement of the density of the sampled aerosol particles. The current article is focused on LS-AMS measurements of spherical, non-absorbing aerosol particles. The laboratory characterization of LS-AMS shows that a single calibration curve yields the material density of spherical particles with real refractive indices (n) over a range from 1.41 < n < 1.60 with an accuracy of about ±10%. The density resolution of the current LS-AMS system is also shown to be 10% indicating that externally mixed inorganic/organic aerosol distributions can be resolved. In addition to the single particle measurements of d _va and R_LS, correlated chemical ion signal intensities are obtained with the quadrupole mass spectrometer. A comparison of the particle mass derived from the physical (R_LS and d _va) and chemical measurements provides a consistency check on the performance of the LS-AMS. The ability of the LS-AMS instrument to measure the density of ambient aerosol particles is demonstrated with sample results obtained during the Northeast Air Quality Study (NEAQS) in the summer of 2004.     

Small‐angle X‐ray scattering analysis of nanophase titanium dioxide,poly[N‐(4‐sulfophenyl)aniline], and their composite

Small‐angle X‐ray scattering and spectroscopic (infrared and ultraviolet–visible) techniques were used to investigate the interactions between titanium dioxide (TiO₂) and the semiconductor polymer poly[N‐(4‐sulfophenyl)aniline] (PSA) in a poly[N‐(4‐sulfophenyl)aniline]/TiO₂ composite (TPSA). The radius of gyration of the cross section, the radius and length of the rodlike particle, the persistence length, the surface fractal dimension, and the PSA layer thickness on TiO₂ in aqueous solutions and in powder form were calculated. The results indicated that the aggregation of TiO₂ particles on drying was reduced by the formation of the composite with the semiconductor polymer. Only the particle length of the TPSA particle (which had a rodlike shape) increased on drying, probably because of increasing void sizes and the formation of aggregation. The persistence length of the TPSA particles decreased with respect to its individual components. The PSA layer thickness on TiO₂ was about 3.6 nm and decreased (to 2.6 nm) on dehydration because of the expulsions of water molecules from the TiO₂/PSA composite. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3183–3187, 2003     

Determination of volume,scaling exponents,and particle alignment of nanoparticle agglomerates using tandem differential mobility analyzers

Tandem Differential Mobility Analyzers (TDMA) were used along with TEM analysis to determine agglomerate volume, scaling exponents for both mass-mobility diameter (D_fm) and friction coefficient-number of primary particles (η) for the mobility diameter in the range 30–300 nm. The larger agglomerates with d_m=250 and 300 nm require a temperature of 800 °C and a sintering time of 0.7 s to form a spherical shape compared to 600 °C for a mobility diameter of 150 nm. It is shown that the 3% decrease in mobility size of the 250 and 300 nm agglomerates with increasing sintering temperature (600–800 °C) is a result of a morphology change from an ellipsoid to a sphere during the sintering process. The effect of sublimation on the sintered particle size is negligible with less than a 0.5% decrease in diameter for a 300 nm mobility diameter agglomerate at 800 °C. The TDMA results show that D_fm is not dependent on mobility size range and that η is dependent on the size range. Both results are counter to predictions based on free molecular models. These results confirm previous results obtained using a DMA together with an aerosol particle mass analyzer (APM) and are shown to have about a factor of two smaller uncertainty. It is also experimentally demonstrated that the agglomerate particles with d_m=300 nm are partially aligned in the electric field of DMA. The correction for a random orientation results in a significant decrease in D_fm by 3.5% and a significant increase in η by 3%.