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Novel Dispersion and Self-Assembly of Carbon Nanotubesof Carbon Nanotubes
Mohammad F. Islam
Department of Chemical Engineering and
100g100gDepartment of Chemical Engineering and
Department of Materials Science & Engineering
http://islamgroup.cheme.cmu.edu
Korea-US NanoForum 2010, Seoul, KoreaA il 5 6 2010April 5-6, 2010
NSF: CBET-0708418, DMR-0619424 and DMR-0645596ACS PRF
Funding Agencies
ACS-PRFSloan FoundationDARPA
OutlineOutline
I d i S f M i l• Introduction to Soft Materials
• Single Wall Carbon Nanotubes (SWNTs)g• Purification, Dispersions and Their Properties
• Carbon Nanotube Aerogels• Carbon Nanotube Aerogels
• Conclusions
Soft Materials Soft Materials -- IntroductionIntroduction
Introduction to Single Wall Carbon NanotubesIntroduction to Single Wall Carbon Nanotubes
DiamondDiamond C60 C60 “Buckminsterfullerene”“Buckminsterfullerene”
GraphiteGraphite Single wall Carbon Single wall Carbon Nanotube (Nanotube (SWNTSWNT))
Multiwall CarbonMultiwall CarbonNanotube (Nanotube (MWNTMWNT) )
1
SWNTs have extraordinary anisotropic propertiesSWNTs have extraordinary anisotropic properties
~1 nm100 nm – 10,000 nm
Strength (~100x Steel)SWNT
Dekker et al., Nature 386, 474 (1997)
Electrical Conductivity (~Copper)Tensile strength ~200 GPaStiffness ~1 TPaElongation ~30%
Salvetat et al., PRL 82, 944 (2000) Thermal Conductivity ~3x Diamond
Incorporate anisotropic properties of SWNTs into composites
ChallengesChallenges
• H di i i l d h i l
• Large scale production of clean nanotubes.
• Homogeneous dispersion in solvents and host materials.van der Waals attraction: 40 KBT/nm
• Control of diameter, chirality and length.
• Determination of bulk properties and structural behavior.
• Effective integration into composites.
•• Controlled integration into electronic circuits.
Synthesis of SWNTsSynthesis of SWNTs
Research Experience for Undergraduates 2007
Hata et. al., Science 306, 1362 (2005)
Purification of SWNTsPurification of SWNTsStandard wet air burn with H2O2Standard wet air burn with H2O2Mild acid refluxMagnetic gradient fractionationVacuum anneal
20 nm20 nm Flow in nanotube suspension
Collect magneticallymagnet 20 nm20 nm suspension magnetically fractionated nanotubes
magnet
-3 2
3 Purification only2 5
3.0
u/m
g) x
10
0
1
2
Fractionatedns
ity x
105
1 0
1.5
2.0
2.5
LMNT PurifiedLMNT puried and Fractionated
HiPCO PurifiedHiPCO Purified and Fractionated
M (e
mu
-3
-2
-1In
ten
0.0
0.5
1.0
H (Tesla)-12 -8 -4 0 4 8 12
wavenumber (cm-1)500 1000 1500 2000
Nature Materials 4, 589 (2005)
SurfactantsSurfactants
Surfactant+
Surfactant
H d hili h d
micelle
Hydrophobic tail Hydrophilic headgroup water
water
oil +water
Shake++water water
Oil droplets
+
Dispersing SWNTs: Our WorkDispersing SWNTs: Our WorkSodium Dodecyl Benzene Sulfonates (NaDDBS)
SDSSurfactant: TX 100 N DDBS
C12H25 SO3- Na+
3x10-4SWNTs:Time:
SDSSurfactant: TX-1006x10-4
5 days 5 days 2 months2x10-2NaDDBS 5.00
2.50
0 2.50 5.00m
0
Nano Letters 3, 269 (2003)
Purified and Suspended SWNTs Are UndamagedPurified and Suspended SWNTs Are UndamagedOptical Properties
banc
e
0.3
0.4
0.5
sion30
40
50
Abs
orb
0.1
0.2 Em
iss
10
20
Wavelength (nm)800 1200 1600
0.0 0
Electrical Properties
t (nA
)
3
4
5
6Metallic (x5)
p
Cur
ren
0
1
2
3
Semiconducting (x10)
Gate Voltage (V)-10 -5 0 5 10
0
Nature Materials 4, 589 (2005)
AerogelsAerogels: Ultra: Ultra--light light MMesoporousesoporous MMaterialsaterials
Ultra-light
Highly porous materials
Very high strength-to-weightVery high strength to weight
Very high
surface-area-to-volume ratio
Ultra-light structural media
Radiation detector
Thermal insulator
Battery electrode
SupercapacitorSupercapacitor
Aerogel type Electrical Conductivity (S/cm)
Thermal Conductivity (W/m-K)
Density (g/cm3)Conductivity (S/cm) (W/m K)
Silica N/A ~ 0.003 0.0019 ~ 0.1
Rigidity PercolationRigidity PercolationNetwork formation Strong network
a)105
at low Strong networks,
G' (
Pa
103
104
Mod
ulus
102
atea
u M
100
101
10-3 10-2 10-1
Pl
10-1
Phys. Rev. Lett. 93, 168102 (2004)
CNT CNT AerogelsAerogelsIncreasing CNT
concentration
Phys. Rev. Lett. 93, 168102 (2004)
NanoLetters 6, 313 (2006)
CNT gels do not break apart
CNT CNT AerogelsAerogels
Density: 0.02 g/cm3
1 µmAdvanced Materials 19, 661 (2007)
SWNT AerogelsSWNT Aerogels100g weight on 3 aerogel posts
Total aerogel mass:
12.8 mg
100g100g
12.8 mg
10 µmDensity 0.02 g/cm3
100g100gSupports at least~8,000x
own weight
SWNT Aerogel posts20 nm
own weight
g pElectrical Conductivity up to ~10 S/cmSurface area 1860 m2/gThermal Conductivity ~0.3 W/m-K
3 µmAdvanced Materials 19, 661 (2007)
CNT CNT AerogelsAerogels
1500Current (mA)
750
00 8 0 4 0 0 4 0 8
-750
-0.8 -0.4 0 0.4 0.8Voltage (V)
-1500
Backfilling with Backfilling with epoxyepoxyEpon 828 Resin +EpiKure 3234 Crosslinker
Vacuum
Epoxy + cross linker
AerogelVacuum removedResin “wicks” into sample
C d i i l l• Conductivity largely unaffected by backfilling• Improved composite
conductivityAdv. Mater. 17, 1186, 2005
• Can be backfilled with various substancesFracture - Complete fill
Fusing CNT AerogelFusing CNT Aerogel
PRL 89, 075505 (2002)
Fusing CNT AerogelFusing CNT Aerogel
Nature Nanotech. 3, 17 (2008)
Fusing Fusing CNT AerogelCNT Aerogel
Irradiation gives rise to covalent bonds between the tubes.
Th ll t th f th t b t i l iThe overall strength of the nanotube materials may increase.Increase the tensile strength of macroscopic nanotube products.
A beneficial effect on the electronic propertiesA beneficial effect on the electronic properties Irradiation with moderate doses may increase the conductivity of nanotube networks. Spatially localized irradiation can be used for creating functional Spatially localized irradiation can be used for creating functional electronic nanotube-based devices.
Is it possible to fuse CNTs in 3D structure?
Fused Fused CNT AerogelCNT Aerogel
Fused Fused CNT AerogelCNT Aerogel
Fused Fused CNT AerogelCNT Aerogel
Defects on CNTs
A fused CNT junction
Fused Fused CNT AerogelCNT Aerogel
78
HP Outside_hole holder_400V_annealing Outside_carbontape_200V_annealing
23456
-2-1012
J (A
/cm
2 )
7-6-5-4-3
-5 -4 -3 -2 -1 0 1 2 3 4 5-8-7
Voltage (V)
ConclusionsConclusions
W f b i t d lf bl d b t b b d lt li ht l• We fabricated self-assembled carbon nanotube based ultra-light, largesurface area-to-volume ratio electrically conducting porous structure – CNTaerogel.
• CNTs can be fused at junction points to increase mechanical strength andCNTs can be fused at junction points to increase mechanical strength andthermal properties.
100g100g