Drifting inwards in protoplanetary discs I Sticking of chondritic dust at increasing temperatures

Bogdan, Tabea; Pillich, C.; Landers, Joachim; Wende, Heiko; Wurm, Gerhard

doi:10.1051/0004-6361/202038120

Cited by 15 publications

(30 citation statements)

References 54 publications

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“…We measured the splitting tensile strength on cylinders of compressed dust, which break into halves if subjected to a load on the mantle (Brazilian test). Previous works on tensile strength regularly find a power-law dependence on the volume-filling factor (Meisner, T. et al 2012;Steinpilz et al 2019;Bischoff et al 2020), and so did we in paper I (Bogdan et al 2020). These power laws agree with models by Rumpf (1970) and can be traced back to variations in grain number density associated with the filling factor Φ, changes in contact forces F, and variations in the number of contacts per grain in a dust aggregate (cylinder) N as outlined in paper I, or…”

Section: Basalt Sample Wet and Drysupporting

confidence: 82%

“…Dry samples measured imme-diately after drying or measured after spending one week under normal laboratory conditions did not show a significant difference in this behaviour. With respect to our first paper (Bogdan et al 2020), it might be tempting to attribute this increase in tensile strength to changes in composition upon drying (moderate heating) or changes in grain size. However, on the other hand, the strong increase corresponds to the findings by Steinpilz et al (2019) for pure SiO 2 grains, which neither changed size nor composition upon drying.…”

Section: Basalt Sample Wet and Drymentioning

confidence: 92%

“…We therefore applied the same method to the tempered chondritic sample. We milled the remaining mass of the same chondrite used in paper I to micrometre dust of the same size as in Bogdan et al (2020), and again tempered it for 1 h before each measurement in a temperature range from 600 K to 1400 K in vacuum, just like in paper I. In addition, for each heating temperature, the cylinders were dried before measuring.…”

Section: Dry Chondritic Samplementioning

confidence: 99%

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Drifting inwards in protoplanetary discs II: The effect of water on sticking properties at increasing temperatures

Pillich,

Bogdan,

Landers

et al. 2021

Preprint

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In previous laboratory experiments, we measured the temperature dependence of sticking forces between micrometer grains of chondritic composition. The data showed a decrease in surface energy by a factor ∼ 5 with increasing temperature. Here, we focus on the effect of surface water on grains. Under ambient conditions in the laboratory, multiple water layers are present. At the low pressure of protoplanetary discs and for moderate temperatures, grains likely only hold a monolayer. As dust drifts inwards, even this monolayer eventually evaporates completely in higher temperature regions. To account for this, we measured the tensile strength for the same chondritic material as was prepared and measured under normal laboratory conditions in our previous work, but now introducing two new preparation methods: drying dust cylinders in air (dry samples), and heating dust pressed into cylinders in vacuum (super-dry samples). For all temperatures up to 1000 K, the data of the dry samples are consistent with a simple increase in the sticking force by a factor of ∼ 10 over wet samples. Up to 900 K super-dry samples behave like dry samples. However, the sticking forces then exponentially increase up to another factor ∼ 100 at about 1200 K. The increase in sticking from wet to dry extends a trend that is known for amorphous silicates to multimineral mixtures. The findings for super-dry dust imply that aggregate growth is boosted in a small spatial high-temperature region around 1200 K, which might be a sweet spot for planetesimal formation.

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Section: Basalt Sample Wet and Drysupporting

confidence: 82%

Section: Basalt Sample Wet and Drymentioning

confidence: 92%

Section: Dry Chondritic Samplementioning

confidence: 99%

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Drifting inwards in protoplanetary discs II: The effect of water on sticking properties at increasing temperatures

Pillich,

Bogdan,

Landers

et al. 2021

Preprint

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“…To approach a realistic mix of minerals and its evolution in protoplanetary discs, we used a chondrite in Bogdan et al (2020) that we milled to micrometer dust. This dust was then subjected to increasing temperatures for 1 h under vacuum.…”

Section: Introductionmentioning

confidence: 99%

Drifting inwards in protoplanetary discs

Pillich

Bogdan

Landers

et al. 2021

A&A

Self Cite

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In previous laboratory experiments, we measured the temperature dependence of sticking forces between micrometer grains of chondritic composition. The data showed a decrease in surface energy by a factor ~5 with increasing temperature. Here, we focus on the effect of surface water on grains. Under ambient conditions in the laboratory, multiple water layers are present. At the low pressure of protoplanetary discs and for moderate temperatures, grains likely only hold a monolayer. As dust drifts inwards, even this monolayer eventually evaporates completely in higher temperature regions. To account for this, we measured the tensile strength for the same chondritic material as was prepared and measured under normal laboratory conditions in our previous work, but now introducing two new preparation methods: drying dust cylinders in air (dry samples), and heating dust pressed into cylinders in vacuum (super-dry samples). For all temperatures up to 1000 K, the data of the dry samples are consistent with a simple increase in the sticking force by a factor of ~10 over wet samples. Up to 900 K super-dry samples behave like dry samples. However, the sticking forces then exponentially increase up to another factor ~100 at about 1200 K. The increase in sticking from wet to dry extends a trend that is known for amorphous silicates to multimineral mixtures. The findings for super-dry dust imply that aggregate growth is boosted in a small spatial high-temperature region around 1200 K, which might be a sweet spot for planetesimal formation.

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“…Here, γ is the surface energy, E is Young's modulus, ν is the Poisson ratio, and ρ is the density of the material. For basaltic spheres, we use γ = 0.07 J/m 2 (Bogdan, T. et al 2020), E = 4 • 10 10 Pa (Deák & Czigány 2009), ν = 0.25 (Schultz 1995) and ρ = 2900 kg/m 3 and get v st = 1 mm/s. Therefore, the maximum measured sticking velocity is about two orders of magnitude higher than this theoretical value.…”

Section: Sticking Velocitiesmentioning

confidence: 99%

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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Drifting inwards in protoplanetary discs I Sticking of chondritic dust at increasing temperatures

Cited by 15 publications

References 54 publications

Drifting inwards in protoplanetary discs II: The effect of water on sticking properties at increasing temperatures

Drifting inwards in protoplanetary discs II: The effect of water on sticking properties at increasing temperatures

Drifting inwards in protoplanetary discs

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

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