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