First LDA Measurements of Nanoparticle Velocities in a Low-Pressure Impacting Jet

Reuter-Hack, Kerstin; Weber, Alfred P.; Rösler, Stefan; Kasper, Gerhard

doi:10.1080/02786820601160549

Cited by 13 publications

(3 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While the gas velocity profile in such low-pressure impactors (LPI) has been investigated thoroughly in simulations and experiments [4][5][6], only fluid dynamic calculations are available for the particle velocity profile. The first direct measurements of the particle velocities by laser Doppler anemometry (LDA) on specially structured nanoparticles have been recently performed [7]. Thus far, these results support the assumption, which has been made generally since the work of Marple [4], that the particle velocity at impact is ca.…”

Section: Background Theorymentioning

confidence: 59%

Impact Fragmentation of Metal Nanoparticle Agglomerates

Seipenbusch¹,

Toneva

Peukert

et al. 2007

Part & Part Syst Charact

Self Cite

View full text Add to dashboard Cite

Deagglomeration experiments were performed with agglomerates of nanoparticles of Ni and Pt. The fragmentation was induced by high velocity impaction of the agglomerates in a single-stage low pressure impactor and the fragmentation patterns were evaluated by TEM analysis. Weibull statistics are employed for a quantitative description of the fragmentation behavior. This study shows that for well-defined interparticle contacts, the impact fragmentation technique combined with the evaluation according to Weibull statistics, allows the recovery of the expected size dependencies. For Pt and Ag, the adhesion force particle size dependency was dominated by van der Waals forces. In contrast, the adhesion force between Ni particles in the size range from 12-28 nm revealed a much stronger increase with particle size. This phenomenon may be attributed to permanent magnetic dipole moments which are also reflected in the chain-like shape of the agglomerates. For nanoparticle agglomerates with less well-defined contacts, such as those in industrial environments, the method provides a promising application to reveal the bond strength and cohesiveness of nanoparticle powders.

show abstract

Section: Background Theorymentioning

confidence: 59%

Impact Fragmentation of Metal Nanoparticle Agglomerates

Seipenbusch¹,

Toneva

Peukert

et al. 2007

Part & Part Syst Charact

Self Cite

View full text Add to dashboard Cite

show abstract

“…By varying the nozzle flow velocity via the pressure in the impaction chamber from about 30 to 300 m/s, one can adjust the impact velocity (ca. 85% of mean nozzle exit velocity [ 16 ]) and hence the degree of fragmentation.…”

Section: Introductionmentioning

confidence: 99%

Fragmentation and bond strength of airborne diesel soot agglomerates

2008

Self Cite

View full text Add to dashboard Cite

Background: The potential of diesel soot aerosol particles to break up into smaller units under mechanical stress was investigated by a direct impaction technique which measures the degree of fragmentation of individual agglomerates vs. impact energy. Diesel aerosol was generated by an idling diesel engine used for passenger vehicles. Both the aerosol emitted directly and aerosol that had undergone additional growth by Brownian coagulation ("aging") was investigated. Optionally a thermo-desoption technique at 280°C was used to remove all high-volatility and the majority of low-volatility HC adsorbates from the aerosol before aging.

show abstract

“…However, recent calculations by Li and Wang showed that a transition to pure specular reflection occurs for very small nanoparticles leading to a reduced friction force 3) . Even stronger deviations from the Cunningham correction were observed in direct measurements of the velocity of nanoparticles in rectilinear acceleration by means of Laser Doppler Anemometry (LDA) 4) . However, no systematic investigation of the drag coefficient for nanoparticles at large mean free paths has been undertaken so far.…”

Section: Introductionmentioning

confidence: 99%

Drag on Gasborne Nanoparticles in the High Knudsen Number Regime

Weber

2009

KONA

Self Cite

View full text Add to dashboard Cite

At small Knudsen numbers (continuum regime) and sufficiently small Reynolds numbers, the friction resistance of particles with the carrier gas is described by means of the Stokes formula assuming no slip of the gas molecules at the particle surface. However, at high Knudsen numbers, this assumption does not hold anymore and the deviation from the continuum character is considered with the slip or Cunningham correction. In the present work, measurements of the separation curve of nanoparticles in a single-stage low-pressure impactor are presented to systematically investigate the disagreement of classical theory of friction resistance of nanoparticles in low-pressure flows. At the same time, the impaction process of nanoparticles is simulated with a CFD code based on the classic theory. An effective Cunningham correction is determined as a function of the Knudsen number from fitting the calculated separation curve to the measured one. Moreover, the so far unresolved finding of too low densities determined for metal nanoparticles by low-pressure impaction is explained for the first time.

show abstract

First LDA Measurements of Nanoparticle Velocities in a Low-Pressure Impacting Jet

Cited by 13 publications

References 13 publications

Impact Fragmentation of Metal Nanoparticle Agglomerates

Impact Fragmentation of Metal Nanoparticle Agglomerates

Fragmentation and bond strength of airborne diesel soot agglomerates

Drag on Gasborne Nanoparticles in the High Knudsen Number Regime

Contact Info

Product

Resources

About