Quantitatively consistent scale-spanning model for same-material tribocharging

Grosjean, Galien; Wald, Sebastian; Sobarzo, Juan Carlos; Waitukaitis, Scott

doi:10.1103/physrevmaterials.4.082602

Cited by 32 publications

(30 citation statements)

References 46 publications

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“…The measurements could be modeled with patches of charge on the surface of the particles. Irregularly charged surfaces are also consistent with the work by Grosjean et al (2020) and Apodaca et al (2010) on identical material charging. Strong interactions between charge patches should also influence a collision between two dielectric grains and their final approach to one another if these particles have a non-homogeneous charge distribution.…”

Section: Introductionsupporting

confidence: 79%

Observation of bottom-up formation for charged grain aggregates related to pre-planetary evolution beyond the bouncing barrier

Jungmann

Wurm

2021

A&A

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Context. Particles in protoplanetary disks go through a number of phases that are dominated by collisions. In each of these events, grains exchange electrical charge via triboelectric effects. This enhances the stability of particle aggregates. Aims. Dielectric grains are easily charged by collisions. Here, we investigate whether a charge is capable of inducing an aggregation of particles and we consider how collision properties, such as sticking velocities and collisional cross-sections, are altered. Methods. We explored aggregation in microgravity experiments based on the observation of the motion of submillimeter (submm) grains following many collisions. In the process, grains attract each other, collide, stick, and ultimately form small aggregates. Results. We observed a bottom-up formation of irregular aggregates from submm grains. While some of the observed trajectories during the approach of grains reflect the presence of a pure Coulomb potential, the motion is not always in agreement with pure Kepler motion. Higher-order potentials of multipole charge distributions stand as a plausible explanation for this behavior. An immediate consequence of charging is that the particles continue to stick to each other at velocities of ~10 cm s−1, while surface forces of neutral grains are only expected to allow sticking below ~1 mm s−1. No bouncing collision was observed among hundreds of collisions in the given parameter range. Applied to early phases of planet formation, the forming aggregates are therefore the first steps in a new growth phase beyond the traditional bouncing barrier in planet formation.

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Section: Introductionsupporting

confidence: 79%

Observation of bottom-up formation for charged grain aggregates related to pre-planetary evolution beyond the bouncing barrier

Jungmann

Wurm

2021

A&A

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“…However, the agitation method and therefore the process of particle charging is almost identical to previous studies, either with glass beads (Jungmann et al 2018(Jungmann et al , 2021Steinpilz et al 2020a) or with basalt beads (Wurm et al 2019). The width (FWHM) of the corresponding charge distribution scales with the particle size (Wurm et al 2019), with many studies treating charges on insulators as surface charges only (Lee et al 2018;Grosjean et al 2020;Steinpilz et al 2020b). With a similar charge density on the surface as in Wurm et al (2019), a charge distribution centered at zero charge with a FWHM of about 3 • 10 −13 C can be expected.…”

Section: Chargesmentioning

confidence: 69%

“…A dimer or a more complex aggregate still hold charges on their surface. It has to be noted at this point that collisions lead to charge separation (not neutralization) in the first place and grains charged this way have a complex charge pattern with patches of negative and positive charges on their surface (Grosjean et al 2020;Steinpilz et al 2020b). This is also valid for grains which are net neutral.…”

Section: Charge Driven Aggregation and Stabilitymentioning

confidence: 94%

A Smoking Gun for Planetesimal Formation: Charge Driven Growth into a New Size Range

Teiser,

Kruss,

Jungmann

et al. 2021

Preprint

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Collisions electrically charge grains which promotes growth by coagulation. We present aggregation experiments with three large ensembles of basalt beads (150 µm − 180 µm), two of which are charged, while one remains almost neutral as control system. In microgravity experiments, free collisions within these samples are induced with moderate collision velocities (0 − 0.2 m s −1 ). In the control system, coagulation stops at (sub-)mm size while the charged grains continue to grow. A maximum agglomerate size of 5 cm is reached, limited only by bead depletion in the free volume. For the first time, chargedriven growth well into the centimeter range is directly proven by experiments. In protoplanetary disks, this agglomerate size is well beyond the critical size needed for hydrodynamic particle concentration as, e.g., by the streaming instabilities.

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“…It was shown that, as long as charges are considered to be located in the center of the beads, neither the Coulomb force of randomly distributed net charges nor the electric field of a conducting plane can reproduce the observed values. Based on results of Jungmann et al (2018), Steinpilz et al (2020b) and Grosjean et al (2020) among others, we also applied a model of charged surface patches. We note that there is no detailed analysis of the surface charge pattern, i.e., the size of the patches and the charges incorporated in them.…”

Section: Discussion and Application To Marsmentioning

confidence: 99%

Lifting of Tribocharged Grains by Martian Winds

Kruss,

Salzmann,

Parteli

et al. 2021

Preprint

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It is a long-standing open question whether electrification of wind-blown sand due to tribocharging -the generation of electric charges on the surface of sand grains by particle-particle collisionscould affect rates of sand transport occurrence on Mars substantially. While previous wind tunnel experiments and numerical simulations addressed how particle trajectories may be affected by external electric fields, the effect of sand electrification remains uncertain. Here we show, by means of wind tunnel simulations under air pressure of 20 mbar, that the presence of electric charges on the particle surface can reduce the minimal threshold wind shear velocity for the initiation of sand transport, u * ft , significantly. In our experiments, we considered different samples, a model system of glass beads as well as a Martian soil analog, and different scenarios of triboelectrification. Furthermore, we present a model to explain the values of u * ft obtained in the wind tunnel that is based on inhomogeneously distributed surface charges. Our results imply that particle transport that subsides, once the wind shear velocity has fallen below the threshold for sustained transport, can more easily be restarted on Mars than previously thought.

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Quantitatively consistent scale-spanning model for same-material tribocharging

Cited by 32 publications

References 46 publications

Observation of bottom-up formation for charged grain aggregates related to pre-planetary evolution beyond the bouncing barrier

Observation of bottom-up formation for charged grain aggregates related to pre-planetary evolution beyond the bouncing barrier

A Smoking Gun for Planetesimal Formation: Charge Driven Growth into a New Size Range

Lifting of Tribocharged Grains by Martian Winds

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