Experimental Micro/Nanoscale Thermal Transport

275 Pages·2012·3.878 MB·English

by  Xinwei Wang(auth.)

EXPERIMENTAL
MICRO/NANOSCALE
THERMAL TRANSPORT
EXPERIMENTAL
MICRO/NANOSCALE
THERMAL TRANSPORT
XINWEI WANG
AJOHNWILEY&SONS,INC.,PUBLICATION
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LibraryofCongressCataloging-in-PublicationData:
Wang,Xinwei,1948-
Experimentalmicro/nanoscalethermaltransport/XinweiWang.
pagescm
Includesbibliographicalreferences.
ISBN978-1-118-00744-0(hardback)
1. Nanostructuredmaterials—Thermalproperties.2.Heat—Transmission.
I.Title.
TA418.9.N35W3652012
620.1(cid:2)1596–dc23
2011047244
PrintedintheUnitedStatesofAmerica
10987654321
CONTENTS
PREFACE xi
1 INTRODUCTION 1
1.1 Unique Feature of Thermal Transport in Nanoscale
and Nanostructured Materials / 1
1.1.1 Thermal Transport Constrained by Material Size / 2
1.1.2 Thermal Transport Constrained by Time / 6
1.1.3 Thermal Transport Constrained by the Size of Physical
Process / 8
1.2 Molecular Dynamics Simulation of Thermal Transport
at Micro/Nanoscales / 10
1.2.1 Equilibrium MD Prediction of Thermal
Conductivity / 11
1.2.2 Nonequilibrium MD Study of Thermal Transport / 15
1.2.3 MD Study of Thermal Transport Constrained by
Time / 18
1.3 Boltzmann Transportation Equation for Thermal Transport
Study / 21
1.4 Direct Energy Carrier Relaxation Tracking (DECRT) / 32
1.5 Challenges in Characterizing Thermal Transport at
Micro/Nanoscales / 44
References / 45
v
vi CONTENTS
2 THERMALCHARACTERIZATIONINFREQUENCY
DOMAIN 47
2.1 Frequency Domain Photoacoustic (PA) Technique / 47
2.1.1 Physical Model / 48
2.1.2 Experimental Details / 50
2.1.3 PA Measurement of Films and Bulk Materials / 52
2.1.4 Uncertainty of the PA Measurement / 55
2.2 Frequency Domain Photothermal Radiation (PTR)
Technique / 57
2.2.1 Experimental Details of the PTR Technique / 57
2.2.2 PTR Measurement of Micrometer-Thick Films / 58
2.2.3 PTR with Internal Heating of Desired Locations / 60
2.3 Three-Omega Technique / 62
2.3.1 Physical Model of the 3ω Technique for
One-Dimensional Structures / 62
2.3.2 Experimental Details / 65
2.3.3 Calibration of the Experiment / 67
2.3.4 Measurement of Micrometer-Thick Wires / 69
2.3.5 Effect of Radiation on Measurement Result / 70
2.4 Optical Heating Electrical Thermal Sensing (OHETS)
Technique / 73
2.4.1 Experimental Principle and Physical Model / 73
2.4.2 Effect of Nonuniform Distribution of Laser Beam / 74
2.4.3 Experimental Details and Calibration / 77
2.4.4 Measurement of Electrically Conductive Wires / 79
2.4.5 Measurement of Nonconductive Wires / 81
2.4.6 Effect of Au Coating on Measurement / 83
2.4.7 Temperature Rise in the OHETS Experiment / 84
2.5 Comparison Among the Techniques / 85
References / 86
3 TRANSIENTTECHNOLOGIESINTHETIMEDOMAIN 87
3.1 Transient Photo-Electro-Thermal (TPET) Technique / 87
3.1.1 Experimental Principles / 88
3.1.2 Physical Model Development / 88
3.1.3 Effect of Nonuniform Distribution and Finite Rising
Time of the Laser Beam / 90
3.1.4 Experimental Setup / 92
3.1.5 Technique Validation / 93
CONTENTS vii
3.1.6 Thermal Characterization of SWCNT Bundles and Cloth
Fibers / 95
3.2 Transient Electrothermal (TET) Technique / 98
3.2.1 Physical Principles of the TET Technique / 98
3.2.2 Methods for Data Analysis to Determine the Thermal
Diffusivity / 100
3.2.3 Effect of Nonconstant Electrical Heating / 101
3.2.4 Experimental Details / 102
3.2.5 Technique Validation / 104
3.2.6 Measurement of SWCNT Bundles / 105
3.2.7 Measurement of Polyester Fibers / 107
3.2.8 Measurement of Micro/Submicroscale Polyacrylonitrile
Wires / 109
3.3 Pulsed Laser-Assisted Thermal Relaxation Technique / 113
3.3.1 Experimental Principles / 113
3.3.2 Physical Model for the PLTR Technique / 114
3.3.3 Methods to Determine the Thermal Diffusivity / 116
3.3.4 Experimental Setup and Technique Validation / 117
3.3.5 Measurement of Multiwalled Carbon Nanotube
(MWCNT) Bundles / 118
3.3.6 Measurement of Individual Microscale Carbon
Fibers / 122
3.4 Super Channeling Effect for Thermal Transport in
Micro/Nanoscale Wires / 123
3.5 Multidimensional Thermal Characterization / 128
3.5.1 Sample Preparation / 129
3.5.2 Thermal Characterization Design / 130
3.5.3 Thermal Transport Along the Axial Direction of
Amorphous TiO Nanotubes / 131
2
3.5.4 Thermal Transport in the Cross-Tube Direction of
Amorphous TiO Nanotubes / 133
2
3.5.5 Evaluation of Thermal Contact Resistance Between
Amorphous TiO Nanotubes / 136
2
3.5.6 Anisotropic Thermal Transport in Anatase TiO
2
Nanotubes / 137
3.6 Remarks on the Transient Technologies / 139
References / 139
4 STEADY-STATETHERMALCHARACTERIZATION 141
4.1 Generalized Electrothermal Characterization / 142
viii CONTENTS
4.1.1 Generalized Electrothermal (GET) Technique: Combined
Transient and Steady States / 142
4.1.2 Experimental Setup / 144
4.1.3 Experimental Details / 145
4.1.4 Measurement of MWCNT Bundle with L=3.33 mm
and D =94.5 μm / 147
4.1.5 Measurement of MWCNT Bundle with L=2.90 mm
and D =233 μm / 153
4.1.6 Analysis of the Tube-to-Tube Thermal Contact
Resistance / 157
4.1.7 Effect of Radiation Heat Loss / 158
4.2 Get Measurement of Porous Freestanding Thin Films Composed
of Anatase TiO Nanofibers / 159
2
4.2.1 Sample Preparation / 160
4.2.2 R–T Calibration / 162
4.2.3 TET Measurement of Thermal Conductivity and Thermal
Diffusivity / 163
4.2.4 Thermophysical Properties of Samples with Different
Dimensions / 167
4.2.5 The Intrinsic Thermal Conductivity of TiO
2
Nanofibers / 170
4.2.6 Uncertainty Analysis / 172
4.3 Measurement of Micrometer-Thick Polymer Films / 173
4.3.1 Sample Preparation / 173
4.3.2 Electrical Resistance (R)-Temperature Coefficient
Calibration / 175
4.3.3 Measurement of Thermal Conductivity and Thermal
Diffusivity / 175
4.3.4 Thermophysical Properties of P3HT Thin Films with
Different Dimensions / 178
4.4 Steady-State Electro-Raman Thermal (SERT) Technique / 182
4.4.1 Experimental Principle and Physical Model
Development / 183
4.4.2 Experimental Setup for Measuring CNT
Buckypaper / 187
4.4.3 Calibration Experiment / 188
4.4.4 Thermal Characterization of MWCNT
Buckypapers / 190
4.4.5 Thermal Conductivity Analysis / 192
CONTENTS ix
4.4.6 Uncertainty Induced by Location of Laser Focal
Point / 195
4.4.7 Effect of Thermal and Electrical Contact Resistances and
Thermal Transport in Electrodes / 196
4.5 SERT Measurement of MWCNT Bundles / 197
4.6 Extension of the Steady-State Techniques / 202
References / 202
5 STEADY-STATEOPTICAL-BASEDTHERMAL
PROBINGANDCHARACTERIZATION 205
5.1 Sub-10-nm Temperature Measurement / 205
5.1.1 Introduction to Sub-10-nm Near-Field Focusing / 206
5.1.2 Experimental Design and Conduction / 208
5.1.3 Measurement Results / 210
5.1.4 Physics Behind Near-Field Focusing and Thermal
Transport / 213
5.2 Thermal Probing at nm/SUB-nm Resolution for Studying
Interface Thermal Transport / 219
5.2.1 Introduction / 219
5.2.2 Experimental Method / 220
5.2.3 Experimental Results / 221
5.2.4 Comparison with Molecular Dynamics Simulation / 225
5.2.5 Discussion / 226
5.3 Optical Heating and Thermal Sensing using Raman
Spectrometer / 234
5.3.1 Thermal Conductivity Measurement of Suspended
Filmlike Materials / 234
5.3.2 Thermal Conductivity Measurement of Suspended
Nanowires / 236
5.4 Bilayer Sensor-Based Technique / 237
5.5 Further Consideration for Micro/Nanoscale Thermal Sensing and
Characterization / 238
5.5.1 Electrothermal Sensing in Thermal Characterization of
Coatings/Films / 239
5.5.2 Transient Photo-Heating and Thermal Sensing of
Wirelike Samples / 240
References / 242
INDEX 247
PREFACE
With the fast development of nanoscience and nanotechnology, it has become
more and more important to understand various physical properties of nanoscale
and nanostructured materials in order to evaluate their unique characteristics
and apply them to different engineering applications. Nanoscale and nanostruc-
tured materials could have very different thermal conductivity, since the energy
carriers (phonons or electrons) can be strongly scattered by the extremely con-
strained material feature size, and their dispersion relation can also be altered.
Although tremendous effort has been dedicated to modeling the thermal trans-
port in micro/nanoscale materials and exploring how and to what extent their
uniquematerialsizeandstructurechangetheirthermalconductivity,itultimately
requires experiments to validate these modeling predictions. Owing to the great
complexity and variety of micro/nanoscale material structures, largely because
of varying manufacturing/growth conditions, measurement is becoming critical
for obtaining accurate information about the thermophysical properties of these
materials, monitor their quality, and provide the knowledge base for device per-
formance optimization. One example of thermal characterization application is
the performance evaluation of thermoelectric materials, which can be used to
convert thermal energy to electricity. The performance of thermoelectric materi-
alscanbedescribedusingthefigureofmeritZ =σS2/k,whereσ istheelectric
conductivity; S, the Seebeck coefficient; and k, thermal conductivity. It can be
seen that accuracy of k measurement directly affects the figure of merit. Many
novel thermoelectric materials are in the form of thin films or nanowires, which
make accurate thermal conductivity measurement more challenging. Although
such measurement is critical to confirm the novel performance claims of these
materials.
xi
xii PREFACE
In the past, various books were published to introduce to micro/
nanoscale thermal transport. These books, together with some excellent journal
reviews, cover comprehensive knowledge about micro/nanoscale thermal
transport, from its unique feature, physics background, and material structure
to theoretical analysis, numerical modeling, and experimental characterization.
On the other hand, it is realized that this area is still under fast development,
partly owing to the emergence of novel materials. Instead of an extended
review to cover various technologies developed by researchers to characterize
thermophysical properties and thermal phenomena, this book focuses on the
novel technology development, material thermal characterization, and thermal
transport study conducted by the author and his laboratory. From the perspective
of materials, the thermal characterization study covers materials of films (micro-
to nanometers thick); single one-dimensional materials, wire/tube bundles,
and highly packed and highly aligned one-dimensional materials; and material
interface thermal transport phenomena. In terms of technology development for
thermal excitation, pulsed, step, and periodic photon and electric excitations
have been employed. To measure the thermal response of the material, its
electrical resistance, thermal radiation, acoustic vibration, and photon scattering
have been used.
This book is designed to cover the details of the novel technology develop-
ment,fromexperimentalprinciple,physicalmodel,andexperimentconductionto
data analysis, result uncertainty assessment, and result physical interpretation. It
will help readers adopt the covered technologies, or design specific technologies
to characterize their unique materials, and to realize high accuracy thermophys-
ical properties measurement and thermal transport study. Chapter 1 provides
a general introduction to thermal transport at micro/nanoscales, including the
micro/nanoscale thermal transport constrained by the material dimension or
internalstructurefeaturesize,thermaltransportconstrainedbytime,andthermal
transport constrained by the size of physical process. Numerical techniques
are discussed on how to predict the thermal conductivity or thermal transport
phenomenon at micro/nanoscales, including the molecular dynamics simulation,
lattice Boltzmann method (LBM), and direct energy carrier relaxation tracking.
Chapter 2 discusses how to characterize thermal transport using thermal
excitation and sensing in the frequency domain. The frequency domain photoa-
coustic technique, photothermal radiation technique, three-omega technique, and
optical heating and electrical thermal sensing technique are discussed in detail.
These techniques can be used to measure the thermophysical properties of
films/coatings and conductive/nonconductive wires. Chapter 3 covers transient
technologies in the time domain, involving photon and electric heating. The
thermal response of the sample is tracked by observing its electrical resistance
change. For nonconductive samples, a metallic coating (e.g., Au) is deposited on
thesurfaceofthesampletofunctionasaheaterandthermalsensor.InChapter4,
the focus is on techniques in which the material is subjected to static heating
(electric or photon heating), and its temperature is measured by evaluating its
electricalresistanceorRamansignal.Variousmaterialsarediscussedforthermal