Mechanisms of Contact Electrification at Aluminum-Polytetrafluoroethylene and Polypropylene-Water

Handle URI:
http://hdl.handle.net/10754/623459
Title:
Mechanisms of Contact Electrification at Aluminum-Polytetrafluoroethylene and Polypropylene-Water
Authors:
Nauruzbayeva, Jamilya ( 0000-0002-9585-6471 )
Abstract:
Contact electrification refers to the transfer of electrical charges between two surfaces, similar and dissimilar, as they are brought into contact and separated; this phenomenon is also known as static electrification or triboelectrification. For example, everyone has experienced weak electrical shocks from metal doorknobs, wool and synthetic clothing on dry days. While contact electrification might appear insignificant, it plays a key role in numerous natural and industrial processes, including atmospheric lightning, accumulation of dust on solar panels, charging of liquids during pipetting and flow in the tubes, and fire hazards in granular media. Contact electrification at metal-metal interfaces is well understood in terms of transfer of electrons, but a comprehensive understanding of contact electrification at interfaces of electrical insulators, such as air, water, polytetrafluoroethylene (PTFE), polypropylene remains incomplete. In fact, a variety of mechanisms responsible for transfer of electrical charges during mechanical rubbing, slipping, sliding, or flow at interfaces have been proposed via: electrons, ions, protons, hydroxide ions from water, specific orientation of dipoles, mechanoradicals, cryptoelectrons, and transfer of material. We have noticed that the extent of contact electrification of solids in water is influenced by surface free energies, mobile ions, surface roughness, duration of contact, sliding speeds, and relative humidity. Herein, we present results of our experimental investigation of contact electrification at the following interfaces: (i) PTFE-aluminum in air and (ii) polypropylene-water interfaces. To identify the underlying mechanism, we started with various hypotheses and exploited a variety of experimental techniques to falsify most of them until we got an answer; our techniques included high-voltage power supply (0-10,000 V), Faraday cages, Kelvin probe force microscopy, electrodeposition, X-ray photoelectron spectroscopy, energy-dispersive spectroscopy, optical microscopy, a contact angle cell, and high-speed imaging. We concluded that contact electrification at the PTFE-aluminum interface was driven by electrons transferred from aluminum to PTFE. In contrast, contact electrification at the polypropylene-water interface was driven by the specific adsorption of OH- ions onto polypropylene. These insights should be helpful in designing applications of polymers where electrical charging could have influence, or applications that could be based on electrical charging at such interfaces, such as triboelectric generator.
Advisors:
Mishra, Himanshu ( 0000-0001-8759-7812 )
Committee Member:
Santamarina, J. Carlos ( 0000-0001-8708-2827 ) ; Saikaly, Pascal ( 0000-0001-7678-3986 )
KAUST Department:
Biological and Environmental Sciences and Engineering (BESE) Division
Program:
Environmental Science and Engineering
Issue Date:
Apr-2017
Type:
Thesis
Appears in Collections:
Theses

Full metadata record

DC FieldValue Language
dc.contributor.advisorMishra, Himanshuen
dc.contributor.authorNauruzbayeva, Jamilyaen
dc.date.accessioned2017-05-10T06:41:56Z-
dc.date.available2017-05-10T06:41:56Z-
dc.date.issued2017-04-
dc.identifier.urihttp://hdl.handle.net/10754/623459-
dc.description.abstractContact electrification refers to the transfer of electrical charges between two surfaces, similar and dissimilar, as they are brought into contact and separated; this phenomenon is also known as static electrification or triboelectrification. For example, everyone has experienced weak electrical shocks from metal doorknobs, wool and synthetic clothing on dry days. While contact electrification might appear insignificant, it plays a key role in numerous natural and industrial processes, including atmospheric lightning, accumulation of dust on solar panels, charging of liquids during pipetting and flow in the tubes, and fire hazards in granular media. Contact electrification at metal-metal interfaces is well understood in terms of transfer of electrons, but a comprehensive understanding of contact electrification at interfaces of electrical insulators, such as air, water, polytetrafluoroethylene (PTFE), polypropylene remains incomplete. In fact, a variety of mechanisms responsible for transfer of electrical charges during mechanical rubbing, slipping, sliding, or flow at interfaces have been proposed via: electrons, ions, protons, hydroxide ions from water, specific orientation of dipoles, mechanoradicals, cryptoelectrons, and transfer of material. We have noticed that the extent of contact electrification of solids in water is influenced by surface free energies, mobile ions, surface roughness, duration of contact, sliding speeds, and relative humidity. Herein, we present results of our experimental investigation of contact electrification at the following interfaces: (i) PTFE-aluminum in air and (ii) polypropylene-water interfaces. To identify the underlying mechanism, we started with various hypotheses and exploited a variety of experimental techniques to falsify most of them until we got an answer; our techniques included high-voltage power supply (0-10,000 V), Faraday cages, Kelvin probe force microscopy, electrodeposition, X-ray photoelectron spectroscopy, energy-dispersive spectroscopy, optical microscopy, a contact angle cell, and high-speed imaging. We concluded that contact electrification at the PTFE-aluminum interface was driven by electrons transferred from aluminum to PTFE. In contrast, contact electrification at the polypropylene-water interface was driven by the specific adsorption of OH- ions onto polypropylene. These insights should be helpful in designing applications of polymers where electrical charging could have influence, or applications that could be based on electrical charging at such interfaces, such as triboelectric generator.en
dc.language.isoenen
dc.subjectContact Electrificationen
dc.subjectTriboelectricityen
dc.subjectChange Transferen
dc.subjectMetals-insulator interfaceen
dc.subjectInsulator- water interfaceen
dc.titleMechanisms of Contact Electrification at Aluminum-Polytetrafluoroethylene and Polypropylene-Wateren
dc.typeThesisen
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberSantamarina, J. Carlosen
dc.contributor.committeememberSaikaly, Pascalen
thesis.degree.disciplineEnvironmental Science and Engineeringen
thesis.degree.nameMaster of Scienceen
dc.person.id142852en
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