Particle-Size-Dependent Triboelectric Charging in Single-Component Granular Materials: Role of Humidity

Toth, Joseph R.; Phillips, Amber K.; Rajupet, Siddharth; Sankaran, R. Mohan; Lacks, Daniel J.

doi:10.1021/acs.iecr.7b02328

Cited by 32 publications

(12 citation statements)

References 38 publications

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“…This partitioning of charge polarity among particles of different sizes in the small and medium samples is consistent with previous descriptions of triboelectricity in granular materials (Forward et al, 2009a;Waitukaitis et al, 2014;Toth III et al, 2017). As noted by Forward et al (2009a), such size effect appears to be a universal characteristic of chemically-homogeneous triboelectrification.…”

Section: Size-dependent Bipolar Chargingsupporting

confidence: 90%

“…More recently, Méndez Harper et al (2020) showed that even smaller amounts of water (below the saturation limit) can reduce the magnitude of triboelectric charging if pyroclasts have high residence times in humid environments. Using a fludizied bed, Toth III et al (2017) showed that granular materials still charge at high humidities, but that these conditions effectively nullify SDBC (i.e. a large particle is equally likely to be charged negatively as a small particle).…”

Section: Electrical Effects Beyond the Gas Thrust Regionmentioning

confidence: 99%

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Charge injection into the atmosphere by explosive volcanic eruptions through triboelectrification and fragmentation charging

Harper,

Cimarelli,

Cigala

et al. 2021

Preprint

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Volcanic eruptions are associated with a wide range of electrostatic effects. Increasing evidence suggests that high-altitude discharges (lightning) in maturing plumes are driven by electrification processes that require the formation of ice (analogous to processes underpinning meteorological thunderstorms). However, electrical discharges are also common at or near the volcanic vent. A number of "ice-free" electrification mechanisms have been proposed to account for this activity: fractocharging, triboelectric charging, radioactive charging, and charging through induction. Yet, the degree to which each mechanism contributes to a jet's total electrification and how electrification in the gas-thrust region influences electrostatic processes aloft remains poorly constrained. Here, we use a shock-tube to simulate overpressured volcanic jets capable of producing spark discharges in the absence of ice. These discharges may be representative of the continual radio frequency (CRF) emissions observed at a number of eruptions. Using a suite of electrostatic sensors, we demonstrate the presence of size-dependent bipolar charging (SDBC) in a discharge-bearing flow for the first time. SDBC has been readily associated with triboelectric charging in other contexts and provides direct evidence that contact and frictional electrification play significant roles in electrostatic processes in the vent and near-vent regions of an eruption. Additionally, we find that particles leaving the region where discharges occur remain moderately electrified. This degree of electrification may be sufficient to drive near-vent lightning higher in the column. Thus, near-vent discharges may be underpinned by the same electrification mechanisms driving CRF, albeit involving greater degrees of charge separation.

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Section: Size-dependent Bipolar Chargingsupporting

confidence: 90%

Section: Electrical Effects Beyond the Gas Thrust Regionmentioning

confidence: 99%

Charge injection into the atmosphere by explosive volcanic eruptions through triboelectrification and fragmentation charging

Harper,

Cimarelli,

Cigala

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…To isolate the triboelectric charging effects arising solely from particle to particle interactions, a system was designed using a particle fountain and an electrostatic separator, as shown in Figure 2 [9,10]. An air stream passing up through a bed of particles forms a fountain where particles are colliding with other particles but not any other surfaces.…”

Section: Methodsmentioning

confidence: 99%

“…Here we describe experiments used to investigate the triboelectric charging of particles in wind-blown dust [9,10]. One system mimics a sandstorm with wind blowing the across a bed and then between two electrodes.…”

Section: Introductionmentioning

confidence: 99%

Electrostatic charging of wind-blown dust and implications on dust transport

et al. 2019

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It is well known that electric fields occur in wind-blown dust, due to the triboelectric charging of particles as they collide. Triboelectric charging, or contact electrification, is a poorly understood and complex phenomenon. It is especially important in granular systems, as the high surface-to-volume ratio can lead to the build-up of large amounts of charge. A particularly surprising effect, which is important in dust systems, is that charge transfer occurs in systems of a single composition, such that there is a particle-size dependent polarity of the particles. Here, we use a combined experimental and theoretical approach to elucidate the electrostatic charging that occurs during dust storms, and the effects of this electrostatic charging on dust transport. We create laboratory-scale wind-blown dust systems, and study the electrostatic charging. We find that larger particles tend to charge positive and to stay at or near the sand bed, while smaller particles tend to charge negative and get lofted to higher elevations. This self-segregating of charged particles would lead to electric fields within a dust storm. Our results show that electric fields then increase the dust transport by more easily lofting charged particles.

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“…Due to the cancelling contributions of positive and negative particles, the volumetric charge density in lofted dust systems is expected to be very small, while the charge on each individual particle can still be large. Studies have shown that, to some extent, smaller and larger particles tend to charge with different polarities (Zhao et al, 2002;Forward et al, 2009;Bilici et al, 2014;Waitukaitis et al, 2014;Toth et al, 2017). This particle-size-dependent polarity of charge, combined with the separation of small and large particles in a gravitation field such that smaller 60 particles are lofted higher, generates the electric fields in dust storms.…”

mentioning

confidence: 99%

Electrostatic forces alter particle size distributions in atmospheric dust

Toth¹,

Rajupet²,

Squire³

et al. 2019

Preprint

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<p><strong>Abstract.</strong> Large amounts of dust are lofted into the atmosphere from arid regions of the world before being transported up to thousands of kilometers. This atmospheric dust interacts with solar radiation causing changes in the climate, with larger-sized particles having a heating effect, and smaller-sized particles having a cooling effect. Previous studies on the long-range transport of dust have found larger particles than expected, without a model to explain their transport. Here, we investigate the effect of electric fields on lofted airborne dust by blowing sand through a vertically-oriented electric field, and characterizing the size distribution as a function of height. We also model this system, considering the gravitational, drag, and electrostatic forces on particles, to understand the effects of the electric field. Our results indicate that electric fields keep particles suspended at higher elevations and enrich the concentration of larger particles at higher elevations. We extend our model from the small-scale system to long-range atmospheric dust transport to develop insights on the effects of electric fields on size distributions of lofted dust in the atmosphere. We show that the presence of electric fields and the resulting electrostatic force on particles can help explain the transport of unexpectedly larger particles and cause the size distribution to become more uniform as a function of elevation. Thus, our experimental and modelling results indicate that electrostatic forces should be considered when determining the effect of atmospheric dust on the climate.</p>

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Particle-Size-Dependent Triboelectric Charging in Single-Component Granular Materials: Role of Humidity

Cited by 32 publications

References 38 publications

Charge injection into the atmosphere by explosive volcanic eruptions through triboelectrification and fragmentation charging

Charge injection into the atmosphere by explosive volcanic eruptions through triboelectrification and fragmentation charging

Electrostatic charging of wind-blown dust and implications on dust transport

Electrostatic forces alter particle size distributions in atmospheric dust

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