Influence of humidity on tribo-electric charging and segregation in shaken granular media

Schella, André; Herminghaus, Stephan; Schröter, Matthias

doi:10.1039/c6sm02041k

Cited by 80 publications

(81 citation statements)

References 87 publications

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“…This problem motivated the search for further parameters relevant to charge separation. Experiments identified, among others, hydrophobicity [24,25], humidity [26][27][28], temperature [29], strain [30], particle size [14,31], impact velocity and angle [28,32,33] and particle shape and contact mode [34][35][36] as relevant parameters influencing triboelectric charging.…”

Section: Mechanisms Of Triboelectricitymentioning

confidence: 99%

“…If mobile ions are present on the surfaces in contact, the concentrations will equilibrate by thermal motion, and the amount of charge exchanged correlates directly to the surface density of separable surface groups [23,25,38]. Alternative models exist for surfaces without separable surface molecules, which rely on aqueous ions in surface water films [24,27] or in the atmosphere [15].…”

Section: Mechanisms Of Triboelectricitymentioning

confidence: 99%

“…All distributions possess approximately exponential tails and a strong asymmetry and have a positive excess kurtosis (from 0.72 to 1.96). Because environmental conditions influence triboelectricity, we perform additional experiments where we vary the relative air humidity using the climate chamber described in [24]. The samples and the setup are kept at constant conditions for at least half an hour before the start of the measurements.…”

Section: B Multiple Contactsmentioning

confidence: 99%

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Double origin of stochastic granular tribocharging

et al. 2018

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The mechanisms underlying triboelectric charging have a stochastic nature. We investigate how this randomness affects the distributions of charges generated on granular particles during either a single or many collisions. The charge distributions we find in our experiments are more heavy-tailed than normal distributions with an exponential decay of the probability, they are asymmetric, and exhibit charges of both signs. Moreover, we find a linear correlation between the width and mean of these distributions. We rationalize these findings with a model for triboelectric charging which combines stochastic charge separation during contact and stochastic charge recombination after separation of the surfaces. Our results further imply that subsequent charging events are not statistically independent.

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Section: Mechanisms Of Triboelectricitymentioning

confidence: 99%

Section: Mechanisms Of Triboelectricitymentioning

confidence: 99%

Section: B Multiple Contactsmentioning

confidence: 99%

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Double origin of stochastic granular tribocharging

et al. 2018

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“…Tribocharging has been shown to be sensitive to a wide variety of conditions, including the ambient environment conditions [18][19][20], impact velocity [21], material strain [22], the contact force [23], and the microscopic details of the surface contact [24,25]. Previous work has reduced these effects by making highly controlled, precision measurements of the impact charging of a small particle [16,[26][27][28], or by using single-crystal materials that are flat to nanometer precision [29,30].…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of nylon and PTFE triboelectrification

Harris

Lim

Jaeger

2019

Phys. Rev. Materials

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Contact electrification, or tribocharging, is pertinent to a broad range of industrial and natural processes involving dielectric materials. However, the basic mechanism by which charge is transferred between insulators is still unclear. Here, we use a simple apparatus that brings two macroscopic surfaces into repeated contact and measures the charge on the surfaces after each contact. We vary the temperature of the surfaces, and find that increasing temperature leads to a decrease in the magnitude of charge transfer. When paired with a Monte-Carlo simulation and TGA measurements, our results support a mechanism where adsorbed surface water is crucial for charge exchange. Our setup is easily extendable to a variety of industrially relevant materials.

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“…Wall layer development in a tribocharged fluidized bed 861 as impurities and oxides, surface roughness, object geometry and relative humidity, which pose challenges in numerical modelling (Castle 1997;Karner et al 2014;Schella, Herminghaus & Schroter 2017).…”

mentioning

confidence: 99%

Experimental and numerical study of wall layer development in a tribocharged fluidized bed

Sippola

Kolehmainen

Özel³

et al. 2018

J. Fluid Mech.

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The effects of triboelectricity in a small-scale fluidized bed of polyethylene particles were investigated by imaging the particle layer in the vicinity of the column wall and by measuring the pressure drop across the bed. The average charge on the particles was altered by changing the relative humidity of the gas. A triboelectric charging model coupled with a computational fluid dynamics-discrete element method (CFD-DEM) model was utilized to simulate gas-particle flow in the bed. The electrostatic forces were evaluated based on a particle-particle particle-mesh method, accounting for the surface charge on the insulating walls. It was found that simulations with fixed and uniform charge distribution among the particles capture remarkably well both the agglomeration of the particles on the wall and the associated decrease in the pressure drop across the bed. With a dynamic tribocharging model, the charging rate had to be accelerated to render the computations affordable. Such simulations with an artificial acceleration significantly over-predict charge segregation and the wall becomes rapidly sheeted with a single layer of strongly charged particles.

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Influence of humidity on tribo-electric charging and segregation in shaken granular media

Cited by 80 publications

References 87 publications

Double origin of stochastic granular tribocharging

Double origin of stochastic granular tribocharging

Temperature dependence of nylon and PTFE triboelectrification

Experimental and numerical study of wall layer development in a tribocharged fluidized bed

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