Dale W. Schaefer, Jian ZhaoDepartment of Materials Science and Engineering

University of CincinnatiCincinnati, OH 45221-0012

Janis Brown, Dave Anderson, Max Alexander, Liz Donaldson, Lindsay Richardson and Jeff Baur

Air Force Research LaboratoryDayton, Ohio

Jan Ilavsky National Institutes of Standards and Technology

UNICATAdvanced Photon Source

Argonne National Laboratory, 9700 South Cass AvenueArgonne, IL 60439

Hierarchical Structure of Carbon Nanotubes and Nanofibers

Multi-walled Nanofibers Single-walled Nanotubes

300 nm

1.2 µ

TEM comparing MWNFs (left) and SWNTs (right). Note the branched polymer character of the SWNTs. The SWNTs are clustered into “ropes” that are not disrupted upon water suspension. Images are from Air Force Research Laboratory (AFRL).

MWNF SWNT

Scattering from Nanotubes

3000 Å

10-2

10-1

100

101

102

103

104

105

106

107

108

109

Cro

ss S

ecti

on (

cm-1

)

10-5 10-4 10-3 10-2 10-1

q (Å)-1

28µ

0.22µ = 220nm

72nm = 720Å

-4

-2.1

-2.2

-4

RLSWNT_PSSO3_Comb RUnifFt99 RLSWNT_PSSO3_pwd_Comb

CLSWNT/PSSO3Level 1 Level 2 Level 3

G 549.02 16876 3.24e+09Rg 721.5 2196.5 2.79e+05B 0.00050344 1.0878e-08 0.00804Pow 2.0999 4.0051 2.216

PSSO3 Dry Powder (USAXS)

PSSO3 Susspension (LS + USAX)

Short-Scale Structure (dried suspension)

0.001

0.01

0.1

1

10

100

Inte

nsi

ty

0.012 3 4 5 6 7 8 9

0.12

q(Å-1)

-4

18 Å =1.8 nm

-2.0

r043_CLSWNT_H2O_PWD_avg_N_B r053_CLSWNT_PAAHCl_DRY_avg_N_B r054_ARSWNT_H2O_pwd_avg_N_B

Power Law Slope= -2.76

ARSWNT_H2O_pwd Level 1 Level 2

G 3.8573 0Rg 18.114 0B 0.0040198 0.021294Pow 2.1332 1.9831

Hard Particle Diameter = 2.4 x RG = 4.3 nm= 43 ÅToo small?

As Received (dirty)

ASI Nanofibers

0.1

1

10

Inte

nsit

y

3 4 5 6 7 8

10-52 3 4 5 6 7 8

10-42 3 4 5 6

q(Å-1)

-1

rASI_21_PSSO3 rASI_21_PMMA rASI_21_PAAHCL

10-3

10-2

10-1

100

101

102

103

104

105

106

107

108

x-r

ay

Cro

ss S

ecti

on

(cm

-1)

10-5 10-4 10-3 10-2 10-1

q(Å-1)

-1.06

-2.80

-3.27

210 Å

4570 Å

Jian PULS Soln USAX Soln

1.2 µ

Light

Light +USAXS+SAXS

Surface roughness?

Large-Scale Structure of Suspended SWNTs and MWNFs

0.1

1

10

Inte

nsi

ty3 4 5 6 7 89

10-5

2 3 4 5 6 7 89

10-4

2 3 4 5 6

q(Å-1)

ASI Nanofibers

-1.0

PSSO3 PMAA PAAHCL

0.01

0.1

1

10

100

1000

Inte

nsi

ty

10-6

2 3 4 5 6 7

10-5

2 3 4 5 6 7

10-4

2 3 4 5 6

q(Å-1)

Clean SWNT

PMAA PSS03 PAAHCL

-1.87

-2.54

-2.22

Comparison of Small-angle Light scattering from nanotubes and nanofibers.Dispersing agents of PMAA, PSSO3 and PAAHCl were used to assist dispersion in water.

SWNT Fractal Structure MWNF Rod-like Structure

SWNT Aggregates are Very Robust

0.1

1

10

100

1000

Inte

nsi

ty

2 4 6 8

10-5

2 4 6 8

10-4

2 4 6

q(Å-1)

Cl SWNT

PSSO3 5 m PSS03 30 s PSSO3 0 s

0.1

1

10

100

1000

Inte

nsi

ty

10-6

2 4 6 8

10-5

2 4 6 8

10-4

2 4 6

q(Å-1)

Cl SWNT

PMAA_5 m PMAA_30 s PMAA_0 s

Reciprocal space data on SWNTs dispersed in water with polystyrene sulfonate and polymethylacrylic acid.. The data is from a Micromeritics Digisizer.

Sonication has little effect on Large Scale Structure of SWNTs

Stress-Strain Data SWNT/PU

0.5

0.4

0.3

0.2

0.1

0.0

Load

(Lb

s)

1.00.80.60.40.20.0Displacement (in/in)

'19.3 %' '24.2%' '10.7 %' '3.8%' '0 %'

Dynamic Mechanical PropertiesStrain Softening

2

3

4

5

6

789

100S

tora

geM

od

ulu

s_M

Pa

0.12 4

12 4

102

Strain_pct

D162_Heather1_17_r1 D163_Heather1_17_r2 D164_Heather1_17_r3

Loading Dependence (MWNTs in PU)

400

300

200

100

0

Sto

rag

eM

od

ulu

s (

MP

a)

0.12 4 6

12 4 6

102

Strain (%)

D187_22_1 D162_17C_1 D181_11C_1 D184_2C_1 D178_0C_1

21.9 %

16.7%

10.7%

1.9%

0 %

0.4

0.3

0.2

0.1

0.0

Tan

Delt

a

0.12 4 6

12 4 6

102

Strain (%)

D187_22_1 D162_17C_1 D181_11C_1 D184_2C_1 D178_0C_1

Modulus Loss

Align De network

Dispersion Strategies: Polyelectrolyte coatings

---- -

Generic Colloid

++

++

+

Nanofiber -Polyelectrolyte Dispersion in PU

Mechanical Properties of Coated Nanofiber/PU Composites

Comparison of DMA data from uncoated, one layer and two layers coated 15wt% nanotubes PU films. The loss as Tan delta (lower three curves) is plotted on the right axis. The legend in the figure indicates the strain sweep sequence. These samples were all swept three times.

50

40

30

20

10

00.01 0.1 1 10

1.0

0.8

0.6

0.4

0.2

0.0

1 Layer 15%

1 2 3 1 2 3

50

40

30

20

10

00.01 0.1 1 10

1.0

0.8

0.6

0.4

0.2

0.0

Uncoated 15% 1 2 3 1 2 3

50

40

30

20

10

00.01 0.1 1 10

1.0

0.8

0.6

0.4

0.2

0.0

2 Layer 15%C

1 2 31 2 3