Constitutive Model of Aligned Carbon Nanotube/Nafion Nanocomposite Ionic Electroactive ...

144 Pages·2016·16.43 MB·English

Constitutive Model of Aligned Carbon Nanotube/Nafion
Nanocomposite Ionic Electroactive Polymer Actuators
by
Douglas S. Jacobs
B.S.E., Electrical Engineering
University of Michigan (2009)
Submitted to the Department of Mechanical Engineering
in partial fulfillment of the requirements for the degree of
Master of Science in Mechanical Engineering
at the
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
February 2016
(cid:13)c Massachusetts Institute of Technology 2016. All rights reserved.
Author .............................................................
Department of Mechanical Engineering
January 15, 2016
Certified by .........................................................
Brian L. Wardle
Professor of Aeronautics and Astronautics
Thesis Supervisor
Certified by .........................................................
Sang-Gook Kim
Professor of Mechanical Engineering
Thesis Reader
Accepted by.........................................................
Rohan Abeyaratne
Quentin Berg Professor of Mechanics
Chairman, Department Graduate Committee
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Constitutive Model of Aligned Carbon Nanotube/Nafion
Nanocomposite Ionic Electroactive Polymer Actuators
by
Douglas S. Jacobs
SubmittedtotheDepartmentofMechanicalEngineering
onJanuary15,2016,inpartialfulfillmentofthe
requirementsforthedegreeof
MasterofScienceinMechanicalEngineering
Abstract
Research is progressing rapidly on composite nano-structured materials, including aligned
carbon nanotube (A-CNT) polymer nanocomposites (PNC), and with device construction
utilizing these novel materials. However, the material constitutive relations of the PNCs
and tailoring of these is lagging. In this work, A-CNT and Nafion PNC electrodes are
manufactured and investigated as the key active element in ionic-electroactive polymer (i-
EAP) devices. i-EAP actuators are known to create relatively large strains with low input
voltages, and could therefore be used for future high-strain actuation mechanisms such as
synthetic muscles, microfluidic drug delivery, or low-frequency energy harvesting. Tailor-
ingthePNCisaccomplishedbyprocesscontrolandmovingtohighervolumefraction(Vf)
A-CNTs, in order to increase both the rate and magnitude of strain through increased non-
isotropy and specific surface area for ionic transfer efficiency. This work shows methods
to increase the A-CNT synthesis yield from below 50% to ∼90%, while keeping quality
and morphology stable. Porous A-CNT based i-EAP electrodes are synthesized with CNT
and Nafion volume fractions of 10-40% and 10-25%, respectively. Key elements of the
non-isotropic mechanical, electrical and electroactive constitutive law are discussed and
calculated for different morphologies of the electrodes. Tailored high Vf i-EAP devices
at ±3 V show ±4,130 microstrain in the transverse direction and an order of magnitude
smaller strain (±420 microstrain) in the CNT axis direction, with A-CNT and Nafion Vfs
of ∼20% and ∼15%, respectively. These large non-isotropic strains correspond to elec-
troactive coupling coefficients of 7.1 x 10−12 m/V in the transverse direction and 7.2 x
10−13 m/V along the CNT axis. In addition, the i-EAP material’s moduli are measured to
be ∼85 MPa in the CNT axis direction and ∼50 MPa in the transverse direction, with a
relative dielectric permittivity of 79, for this polymeric based i-EAP device. These coef-
ficients constitute the first assembly of mechanical, electrical and electroactive properties
intoaconstitutiverelationforsuchanactivenano-structuredmaterial. Moreextensivedata
sets for completing the full constitutive model and reducing measurement uncertainty are
recommendedforfuturework.
ThesisSupervisor: BrianL.Wardle
Title: ProfessorofAeronauticsandAstronautics
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Acknowledgements
I would like to acknowledge the following people who have helped not only make this re-
search a reality, but turned it into a successful work and a fun journey. First, I would like
to thank my adviser Professor Brian Wardle, who has been patient with my odd circum-
stanceswhilealwaysprovidinginsightandgreatadviceintermsofhowtotacklethemany
unforseen problems, and motivation for pushing the boundaries on CNT technologies. My
first postdoctoral adviser at MIT, Dr. Noa Lachman, for working with me on how to suc-
cessfullyand effectively conductresearch,as wellashow tokeepmytools andworkspace
clean. IwouldalsoliketothankDr. SunnyWicksforteachingmethefinerdetailsincreat-
ingPNCs,afterIhadmanyfailurestocurebubblefreePNCsamples;RichLiforassisting
mewithmanyprocessesinthelabandtocollecttheTGAdata;DianaLewiswhohastaught
me a lot about the CVD process and A-CNT forest growth; Itai Stein for teaching me La-
TeX which this thesis is written in; Dale Lidston for keeping the 1” furnace going when I
am not around, reviewing this thesis, and for the biltong; Dr. Estelle Cohen for her expert
TEM and SEM imaging used in this work; Mackenzie Devoe for her work on the Raman
spectroscopy; Dr. Bharath Natarajan and the National Institute of Standards and Technol-
ogy (NIST) team for attempting the first ever quantitative 3-D electron tomography of the
Nafion PNC samples, as well as SEM and TEM imaging; the Pennsylvania State Univer-
sity Zhang Research Group including Dr. Mehdi Ghaffari and Professor Q. M. Zhang for
sharing the processing and definition for the i-EAP manufacturing and collaborating; Luiz
AcauanandYueZhoufortheirtimespentreviewingthisthesis;AmyTatem-Bannisterand
Dr. Steven Kooi at the MIT Institute for Soldier Nanotechnologies (ISN) for the lab usage
andhospitality,specificallyfortheuseoftheglovebox,potentiostatandZwickequipment;
and the necstlab at MIT for providing a fun and challenging environment for completing
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advanced research. In addition, this work would not be possible without the Aero Astro
and Mechanical Engineering departments at MIT, and the GE Aviation Edison and ACE
programs who have supported this research. Last but most importantly, I would like to ex-
press my appreciation and love for my fiance Emily Altman, for providing moral support,
love,andhelpingmetofixmymanygrammaticalmistakes. Thankyoutoeveryoneonthis
listwhohasmadethisthesispossible!
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Table of Contents
1 Introduction 27
1.1 AlignedCarbonNanotubeNafionNanocompositeIonicElectroactivePoly-
merActuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
1.2 ThesisOutline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2 Background 31
2.1 ElectroactivePolymerMaterialsandApplications . . . . . . . . . . . . . . 31
2.2 AlignedCarbonNanotubeComposites . . . . . . . . . . . . . . . . . . . . 35
2.2.1 CarbonNanotubes . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.2.2 AlignedCarbonNanotubePolymerNanocomposites . . . . . . . . 38
2.3 Nano-structuredIonicElectroactivePolymerMaterials . . . . . . . . . . . 41
2.4 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.4.1 NafionPolymer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.4.2 IonicLiquidsandSolvents . . . . . . . . . . . . . . . . . . . . . . 44
2.4.3 Dimethylformamide . . . . . . . . . . . . . . . . . . . . . . . . . 46
2.5 ElectroactivePolymerChallengesandLiteratureGaps . . . . . . . . . . . 46
3 ObjectivesandApproach 49
4 Experimental 51
4.1 AlignedCarbonNanotubeSynthesis . . . . . . . . . . . . . . . . . . . . . 51
4.1.1 ChemicalVaporDepositionProcessing . . . . . . . . . . . . . . . 51
4.1.2 Delamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
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4.1.3 BiaxialDensification . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.2 GrowthEnhancementsforHighYield1mmTallAlignedCarbonNanotube
Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.2.1 CatalystRipeningandFurnaceOvershoot . . . . . . . . . . . . . . 57
4.2.2 HumidityandWaterUsage . . . . . . . . . . . . . . . . . . . . . . 59
4.2.3 ForestHeightControl . . . . . . . . . . . . . . . . . . . . . . . . 61
4.2.4 WaferPositioning . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.2.5 SummaryofGrowthConditions . . . . . . . . . . . . . . . . . . . 62
4.3 PolymerNanocompositeFabrication . . . . . . . . . . . . . . . . . . . . . 63
4.3.1 NafionSolutionPreparation . . . . . . . . . . . . . . . . . . . . . 64
4.3.2 NafionInfusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.3.3 AnnealingProcess . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.3.4 AirbrushSpeckling . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.4 ElectroactivePolymerNanocomposite . . . . . . . . . . . . . . . . . . . . 72
4.4.1 IonicLiquidPreparation . . . . . . . . . . . . . . . . . . . . . . . 72
4.4.2 IonicLiquidInfusion . . . . . . . . . . . . . . . . . . . . . . . . . 76
5 Results 79
5.1 GrowthEnhancementsandAlignedCarbonNanotubeCharacterization . . 80
5.1.1 ProcessEnhancement . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.1.2 ScanningElectronMicroscopy . . . . . . . . . . . . . . . . . . . . 83
5.1.3 TransmissionElectronMicroscopy . . . . . . . . . . . . . . . . . 84
5.2 PolymerNanocompositeCharacterization . . . . . . . . . . . . . . . . . . 85
5.2.1 ThermogravimetricAnalysis . . . . . . . . . . . . . . . . . . . . . 85
5.2.2 ScanningElectronMicroscopy . . . . . . . . . . . . . . . . . . . . 87
5.2.3 TransmissionElectronMicroscopy . . . . . . . . . . . . . . . . . 93
5.3 ElectroactivePolymerDeviceCharacterization . . . . . . . . . . . . . . . 96
5.3.1 Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.3.2 DigitalImageCorrelation . . . . . . . . . . . . . . . . . . . . . . 104
5.3.3 Mechanical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
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5.3.4 Electroactive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
5.4 ConstitutiveModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
5.4.1 ModelDerivation . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.4.2 IonicElectroactivePolymerDeviceConstitutiveModel . . . . . . . 124
6 ConclusionsandRecommendations 127
6.1 AlignedCarbonNanotubeContributions . . . . . . . . . . . . . . . . . . . 127
6.2 IonicElectroactivePolymerDeviceContributions . . . . . . . . . . . . . . 128
6.3 RecommendedFurtherResearch . . . . . . . . . . . . . . . . . . . . . . . 129
6.3.1 MaterialandDeviceProcessingTechniques . . . . . . . . . . . . . 129
6.3.2 RecommendedPropertyStudies . . . . . . . . . . . . . . . . . . . 131
A FinalA-CNTGrowthProcedureandRecipe 133
B FullSummaryofDevicesManufactured 137
References 141
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