Exploring nanoscale surfaces and interfaces.
Item
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Title
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Exploring nanoscale surfaces and interfaces.
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Identifier
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AAI3287110
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identifier
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3287110
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Creator
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Helt, James M.
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Contributor
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Adviser: James D. Batteas
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Date
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2005
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Polymer
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Abstract
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The atomic force microscope (AFM) offers a definitive approach for investigating the fundamental interactions of contacting surfaces in relative motion. AFM nanotribology investigations of muscovite mica wear under aqueous environments is discussed. Defect nucleation on the atomic scale has been directly observed and is found to present itself initially as surface charging due to stress-induced tribochemical bond scission as OH- breaks open the terminal surface bonds. As surface bonds are continually cleaved, an ensemble of defects contribute to the observed native crystal lattice reconstruction from a 5.2 A to ∼3 A periodicity. Following lattice restructuring, displacement of mica surface materials ensues, yielding wear scars ranging from ∼ 2--10 A in depth. This work is the first in situ demonstration of the tip-mediated tribochemical lattice reconstruction of mica with atomic scale resolution.;A new AFM experimental analysis methodology is also outlined that corrects for a common systematic error in AFM nanotribology studies and provides a more accurate account of an AFM tips scan history during wear trials. Comparison of the contact radius to the line step indicates that overlap of successive scans will result unless the contact radius - line step ratio (CRLS) is less than ½. If this relationship is not considered then the contact history associated with a single scan is not equivalent at different loads owing to the scaling of contact radius with load. The CRLS model is derived and presented in conjunction with empirical wear tests on mica to evaluate the effects of scan overlap. CRLS predictions and empirical tests demonstrate that scan overlap pervades nanoscale wear trials even under low loads and can have deleterious effects on evaluating a materials nanotribological behavior.;Also discussed are two soft lithography techniques which use interfacial surface energetics to control and direct diffusive transport for nanofabrication purposes. First, a chemo-mechanical patterning method is introduced that exploits interfacial forces and local contact stresses for the facile production of nanoscale metal structures on polymers. Lastly, a rapid, reagent free soft lithography technique for the fabrication of self-aligned nanometer scale polymer-metal-polymer (PMP) multilayer structures on ceramic surfaces will also be described.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
