The electrostatic charge that is generated when two materials are contacted or rubbed and then separated is a well-known physical process that has been studied for more than 2500 years Contact electrification occurs in many contexts, both natural and technological For example, in dust storms the collisions between particles lead to electrostatic charging and in extreme cases, extraordinary lightning displays In electrophotography, toner particles are intentionally charged to guide their deposition in well-defined patterns Despite such a long history and so many important consequences, a fundamental understanding of the mechanism behind contact electrification remains elusive An open question is what type of species are transferred between the surfaces to generate charge—experiments suggest various species ranging from electrons to ions to nanoscopic bits of material, and theoretical work suggests that non-equilibrium states may play an important role Another open question is the contact electrification that occurs when two insulating materials with identical physical properties touch—since there is no apparent driving force, it is not clear why charge transfer occurs A third open question involves granular systems—models and experiments have shown that a particle-size dependence for the charging often exists In this review, we discuss the fundamental aspects of contact electrification and highlight recent research efforts aimed at understanding these open questions

https://iopscience.iop.org/article/10.1088/0022-3727/44/45/453001/pdf

Contact electrification of insulating materials

CFD simulation of fluidized bed reactors for polyolefin production – A review

Electrostatics in gas-solid fluidized beds: A review

Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kV m−1 to 100 kV m−1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m−1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)—MicroARES (Atmospheric Radiation and Electricity Sensor) instrumentation to Mars in 2016 for the first in situ electrical measurements.

/pdf/applications-of-electrified-dust-and-dust-devil-3m511288an.pdf

Leigh Miller

Papers

Investigation of electrostatic charge distribution in gas–solid fluidized beds