Desalination by electret technology

Ni, Haifeng; Amme, Robert C.; Jin, Yixin

doi:10.1016/j.desal.2004.10.002

Cited by 3 publications

(3 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…When the DC-DC converter is switched to ground the deposited negative ions remain on the surface.The electret is lamina of 3 to 4 0.4 mm thick corona charged PMMA sheets. The electric field strength scales with the number of dielectric lamina as has also been shown in work on electret based vibrational energy harvesters[42] and in water desalinization[43].The electret is established on a superhydrophobic substrate produced by laser etching PMMA and depositing a thin layer of PTFE on the roughened surface. The surface charge density can be modulated during the experiment using the high-voltage DC-DC converter, which can re-polarize the dielectric substrate by means of an embedded electrode.…”

mentioning

confidence: 90%

Electro-drop bouncing in low-gravity

Schmidt

Weislogel

2020

Physics of Fluids

View full text Add to dashboard Cite

We investigate the dynamics of spontaneous jumps of water drops from electrically charged superhydrophobic dielectric substrates during a sudden step reduction in gravity level. In the brief free-fall environment of a drop tower, with a non-homogeneous external electric field arising due to dielectric surface charges (with surface potentials 0.4-1.8 kV), body forces acting on the jumped drops are primarily supplied by polarization stress and Coulombic attraction instead of gravity. This electric body force leads to a drop bouncing behavior similar to well-known phenomena in 1-g 0 , though occurring for much larger drops (∼ 0.5 mL). We show a simple model for the phenomenon, its scaling, and asymptotic estimates for drop time of flight in two regimes: at short-times close to the substrate when drop inertia balances Coulombic force due to net free charge and image charges in the dielectric substrate and at long-times far from the substrate when drop inertia balances free charge Coulombic force and drag. The drop trajectories are controlled primarily by the dimensionless electrostatic Euler number Eu, which is a ratio of inertial to electrostatic forces. To experimentally determine values of Eu we conduct a series of drop tower experiments where we observe the effects of drop volume, net free charge, and static surface potential of the superhydrophobic substrate on drop trajectories. We use a direct search optimization to obtain a Maximum Likelihood Estimate for drop net charge, as we do not measure it directly in experiment. For φEu/8π > 1 drops escape the electric field, where φ is a drop to substrate aspect ratio. However, we do not observe any escapes in our dataset. With an eye towards engineering applications I am also greatly indebted to Andrew Greenberg for his frequent and sage technical advice, and to Joe Shields for his assistance with drop tower experiments.

show abstract

mentioning

confidence: 90%

Electro-drop bouncing in low-gravity

Schmidt

Weislogel

2020

Physics of Fluids

View full text Add to dashboard Cite

show abstract

“…2 The ones used in ª-radiation dosimeters measure the reduction in the charge of an electret upon the neutralisation of surface charges due to the air ionised by the ª-radiation. The amount of loss in charge is directly proportional to the radiation present.…”

Section: Introductionmentioning

confidence: 99%

Controlling and increasing the inherent voltage in cement paste

Huang¹,

Chung²

2009

Advances in Cement Research

View full text Add to dashboard Cite

An inherent voltage occurs in cement paste, making the material an electret. Both poling (up to 225 V/m DC, causing long-range ion movement) during the 24 h setting and the use of sodium silicate liquid (which provides Na þ ions) as an admixture were found to increase the inherent voltage, in addition to making the voltage more stable and better controlled. Without poling and sodium silicate, the inherent voltage after curing varied in sign and magnitude in an uncontrolled fashion among specimens poured from the same mix; for the same specimen, it varied significantly with the curing time and asystematically during the first 10 days of curing and stabilised thereafter. With both sodium silicate and poling, the voltage was positive (same polarity as the poling voltage), decreased with time throughout curing, and levelled off at a voltage that increased with increasing sodium silicate content, with the highest value attained in the present study being 0 . 35 V. The time constant for depoling during curing ranged from 2 to 7 days in the initial depoling period (up to 11 days), and ranged from 74 to 150 days in the subsequent period.

show abstract

“…Electrets are used for the manufacturing of transducers (e.g. microphones, headphones and loudspeakers), motors and generators, air filters [2], electret floppy disc for storing digital information [3], as well as dosimeters, implants for medicine and even for the desalination of water [4]. Although the applications are mainly restricted to polymer electrets, there is also a considerable interest in nonorganic electrets since they exhibit better mechanical properties and may operate in a wider temperature range, as well as in aggressive atmospheres [5].…”

Section: Introductionmentioning

confidence: 99%