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Study of confinement and sliding fri...

Nanjundiah, Kumar.

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Study of confinement and sliding friction of fluids using sum frequency generation spectroscopy.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Study of confinement and sliding friction of fluids using sum frequency generation spectroscopy./
Author:	Nanjundiah, Kumar.
Description:	203 p.
Notes:	Adviser: Ali Dhinojwala.
Contained By:	Dissertation Abstracts International68-12B.
Subject:	Chemistry, Polymer. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3292837
ISBN:	9780549362531

Study of confinement and sliding friction of fluids using sum frequency generation spectroscopy.
Nanjundiah, Kumar.

Study of confinement and sliding friction of fluids using sum frequency generation spectroscopy. - 203 p.

Adviser: Ali Dhinojwala.

Thesis (Ph.D.)--The University of Akron, 2007.

Friction and wear are important technologically. Tires on wet roads, windshield wipers and human joints are examples where nanometer-thick liquids are confined between flexible-rigid contact interfaces. Fundamental understanding of the structure of these liquids can assist in the design of products such as artificial joints and lubricants for Micro-electromechanical systems [MEMS]. Prior force measurements have suggested an increase in apparent viscosity of confined liquid and sometimes solid-like responses. But, these have not given the state of molecules under confinement. In the present study, we have used a surface sensitive, non-linear optical technique (infrared-visible sum frequency generation spectroscopy [SFG]) to investigate molecular structure at hidden interfaces. SFG can identify chemical groups, concentration and orientation of molecules at an interface.

ISBN: 9780549362531Subjects--Topical Terms:

1018428
Chemistry, Polymer.

Study of confinement and sliding friction of fluids using sum frequency generation spectroscopy.
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020 $a 9780549362531
035 $a (UMI)AAI3292837
035 $a AAI3292837
040 $a UMI $c UMI
100 1 $a Nanjundiah, Kumar. $3 1280768
245 1 0 $a Study of confinement and sliding friction of fluids using sum frequency generation spectroscopy.
300 $a 203 p.
500 $a Adviser: Ali Dhinojwala.
500 $a Source: Dissertation Abstracts International, Volume: 68-12, Section: B, page: 8085.
502 $a Thesis (Ph.D.)--The University of Akron, 2007.
520 $a Friction and wear are important technologically. Tires on wet roads, windshield wipers and human joints are examples where nanometer-thick liquids are confined between flexible-rigid contact interfaces. Fundamental understanding of the structure of these liquids can assist in the design of products such as artificial joints and lubricants for Micro-electromechanical systems [MEMS]. Prior force measurements have suggested an increase in apparent viscosity of confined liquid and sometimes solid-like responses. But, these have not given the state of molecules under confinement. In the present study, we have used a surface sensitive, non-linear optical technique (infrared-visible sum frequency generation spectroscopy [SFG]) to investigate molecular structure at hidden interfaces. SFG can identify chemical groups, concentration and orientation of molecules at an interface.
520 $a A friction cell was developed to study sliding of a smooth elastomeric lens against a sapphire surface. Experiments were done with dry sliding as well as lubricated sliding in the presence of linear alkane liquids. SFG spectra at the alkane/sapphire interface revealed ordering of the confined alkane molecules. These were more ordered than alkane liquid, but less ordered than alkane crystal. Cooling of the confined alkane below its melting temperature [TM] led to molecular orientation that was different from that of bulk crystal next to a sapphire surface. Molecules were oriented with their symmetry axis parallel to the surface normal. In addition, the melting temperature [Tconf] under confinement for a series of linear alkanes (n =15--27) showed a surprising trend. Intermediate molecular weights showed melting point depression. The T conf values suggested that melting started at the alkane/sapphire interface.
520 $a In another investigation, confinement of water between an elastomeric PDMS lens and sapphire was studied. SFG spectra at the sapphire/water/PDMS interface revealed a heterogeneous morphology. The presence of peaks related to PDMS, as well as water, suggested water puddles in the contact area and the sapphire surface had a layer of bound water. This heterogeneity picture provides insight into high friction and stick-slip behavior found in boundary lubrication.
520 $a For the first time, a broadband SFG system has been coupled with a friction cell to study dynamics and molecular changes at an interface during sliding; sliding of confined alkane between sapphire and PDMS was investigated. A series of SFG spectra were taken while the confined alkane contact spot moved in and out of the laser beam. Even though the experiments were done 15°C above melting temperature, the spectra showed ordering of alkane molecules, similar to that of the confined crystal at the leading and trailing edge. The results suggest that a large portion of the resistance to sliding may come from ordering of molecules at the lens front.
590 $a School code: 0003.
650 4 $a Chemistry, Polymer. $3 1018428
650 4 $a Engineering, Materials Science. $3 1017759
650 4 $a Physics, Condensed Matter. $3 1018743
690 $a 0495
690 $a 0611
690 $a 0794
710 2 $a The University of Akron. $3 1018399
773 0 $t Dissertation Abstracts International $g 68-12B.
790 $a 0003
790 1 0 $a Dhinojwala, Ali, $e advisor
791 $a Ph.D.
792 $a 2007
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3292837