Northwestern University Ruoff Group Nanotechnology Mechanics of Nanostructures (Conformational...

Northwestern University Ruoff Group Nanotechnology

Mechanics of Nanostructures

(Conformational states of nanotubes & tensile-loading mechanics of CNTs)

Prof. Rod Ruoff

Department of Mechanical Engineering

Northwestern University

2145 Sheridan Road

Evanston, IL 60208-3111

[email protected]

http://bucky-central.mech.northwestern.edu/

NABIS Chicago August 2006

Support from the NSF, ONR, and NASA is appreciated


The group

Rod Ruoff Richard Piner Dmitry Dikin Xinqi ChenNUANCE staff member

Sasha Stankovich

Weiqiang Ding

Terry XuUNC-Charlotte

Shaoning LuTouchdown Technologies

Geoffrey Dommett, Physics

Kevin Kohlhaas Robbie Cantrell PhD-MD

Eric Zimney

Abel Thangawng

Jae ChungU Wash-Seattle

SupindaWatcharatone

Inhwa Jung


1-D Nanostructures

TEM image of a multi-wall carbon nanotube

SEM image of arc-grown MWCNTs from MER Corp. AZ.

Single-wall carbon nanotube (SWCNT) Multi-wall carbon nanotube (MWCNT)


R. S. Ruoff, J. Tersoff, D. C. Lorents, S. Subramoney, and B. Chan, Radial deformation of carbon nanotubes by van der Waals forces. Nature, 364, 514-16 (1993).

Mean values for inter-fringe distances:MWCNT B: 3.51 (outer) but 3.43 Angstroms (inner)MWCNT A 3.45 (outer) but 3.38 (inner)


J. Tersoff and R. S. Ruoff, Structural properties of a carbon-nanotube crystal. Phys. Rev. Lett., 73, 676-9 (1994).

DWCNTs: M. Endo et al Nature 433, 476 (2005)

Scale bar: 5 nm; measure of 5 DWCNTs present in this image, average diameters of

CNTs (inner) and (outer) are 1.31 and 2.23 nm

Novel polygonized single-wall carbon nanotube bundles M J Lopez et al Phys Rev Lett 86 (14): 3056-3059 APR 2 2001

Single-walled carbon nanotube bundle comprised of SWCNTs with diameter ~ 1.4 nm. Thess et al, Science.


Probing conformational states of MWCNTs. Embed in Formvar, deform at ~70 CRod Ruoff, Rob LaDuca, Shekhar Subramoney, unpublished results


Dong Qian, Wing Kam Liu, Shekhar Subramoney, and Rodney S. Ruoff, Effect of Interlayer Potential on Mechanical Deformation of Multiwalled Carbon Nanotubes, Journal of Nanoscience and Nanotechnology, 3(1/2), 185-191 (2003).

15-shell MWCNT


D. Srivastava, D. W. Brenner, J. D. Schall, K. D. Ausman, M. F. Yu and R. S. Ruoff, Predictions of enhanced chemical reactivity at regions of local conformational strain on carbon nanotubes: Kinky chemistry, J. Phys. Chem., B, 103, 4330-4337 (1999).

Left: Relative H atom binding energies (squares), relative cohesive energies (circles), and relative electronic energies (triangles) for the highlighted atoms. The center atom along the line of highlighted atoms corresponds to an abscissa equal to zero.

Right: Dependence of these energies on ‘POAV1’ pyramidalization angle.


Fracture Mechanics of One-Dimensional Nanostructures:

outer shell of MWCNTs





Testing Tool: Nanomanipulator

A home-built nanomanipulator is used to perform mechanics study inside vacuum chamber of ascanning electron microscope (SEM).

X-Y stage

Piezo bimorph

Z stageCantilever Holder

Specimen/Cantilever Holder

X-Y Stage Z-stage

Piezoelectric Actuator

Nanomanipulator inside vacuum chamber of FEI Nova 600 SEM (Ruoff group)

Home-built nano-manipulator


Setup: Nanoscale Tensile Test

Experimental Setup

X-Y Stage

rigid cantilever

soft cantilever

Z Stage

Tensile Test Schematic

L

L+

s

Atomic force microscope (AFM) cantilevers are used as manipulation tools and force-sensing elements.

MWCNT


Nanoparticle Chain Aggregates Mechanics

• Breaking Force: 42 25 nN

• Tensile Strength: 40 -100 MPa

• Elastic Modulus : 200 - 600 MPa

• Particle Contact Force: 8 4 nN

Tensile TestingStretching a chain

Contact Force MeasurementCarbon nanoparticle chain aggregates

• Nanoparticle diameter: 25-35 nm• Chain length: ~ 2 m

Mechanical properties of nanoparticle chain aggregates by combined AFM and SEM: Isolated aggregates and networks, collaboration with S. FriedlanderGroup, UCLA, submitted to Nano Letters.


In situ Clamping - EBID

Electron beam induced deposition (EBID) is the process of using a high-intensity electron beam to deposit structures on a scanned surface. EBID is commonly used to make clamps in situ inside SEM.

A CNT in contact with an AFM tip, before and after EBID clamping

EBID principle

Hydrocarbon molecules

EBID clamp

Exposure area


MWCNT: Carbon Nanotube Source

SEM image of powdered cathode deposit core material with 30-40% MWCNT content from MER Corp.

SEM image of separated MWCNTs on a silicon wafer, after fractionation.

Arc-grown Multi-wall Carbon Nanotubes (MWCNTs) from MER Corp. AZ. were studied in this work. A simple fractionation process was used to remove some impurities and increase nanotube concentration.


MWCNT: “Sword-in-sheath” Fracture

Outer shellInner shells

Cross-sectional area: πDΔA

D

: inter-layer separation of graphite, 0.34 nm

Multi-wall carbon nanotubes fracture in a “sword-in sheath” manner during tensile test.


MWCNT: Diameter Measurement

(a) AFM chip holder model

AFM cantilevers (c) Gatan TEM straining holder (model 654)

(d) SEM and TEM images of a MWCNT fragment attached to an AFM tip.

(b) An AFM chip in the AFM chip holder

Cantilever holders were designed to hold a shortened AFM chip for nanotube diameter measurement in TEM.


MWCNT: Stress & Strain Measurements

The whole tensile testing process was recorded by taking SEM images at each loading step.


MWCNT: Tensile Testing Result

Fracture Strength Elastic Modulus

Average elastic modulus: ~ 910 GPa


MWCNT: Multiple Loading (Tube #6)

Test #

Gauge Length

(m)

Breaking Force

(nN)

Tensile Strength

(GPa)

Failure Strain

(%)

Elastic Modulus

(GPa)

1 4.08 220 21 1.4 1.8 0.3 1200 210

2 3.75 240 23 1.4 1.9 0.3 1250 210

3 3.46 420 41 2.6 3.0 0.2 1230 130

(1) (2) (3)


SWCNT fracture mechanics…

Collaboration with Jim Hone group, Columbia UniversityAlan Cassell, NASA Ames


SWCNT Sample

Individual or small bundle of SWCNTs spanning across a trench (from Prof. Jim Hone’s group, Columbia Univ.)


This is the one that Weiqiang measured.Does Hone team know n and m?

We wonder if you have n and mfor this (these) tubes?

Notes accompanying samples sent


Tensile Testing ConfigurationExperimental Setup EBID Clamping

X-Y Stage

Z Stage

Tipless AFM cantilever

AFM cantilever


Tensile Testing

Assuming a diameter of 1.0 nm, the corresponding Young’s modulus is 870 GPa for this specific SWCNT; with this diam strength would be ~45 GPa.


piezodriver

TEM testing stage adapted to TEM sample holder

TEM testing stage: postdoc Henry Rohrs, 1997-99 (fabricated CNF-Hui Huang, postdoc)


Why Nanorope?AA

BB

To achieve load transfer so that the full bundle cross-section would be participating in load-bearing up to the intrinsic SWCNT breaking strength, the SWCNT contact length must be on the order of 10 to 120 microns (but note that Dong gets 1.3 um for the relaxed case,3.8 um for rigid cylinders-preliminary results)

There is strong evidence, however, that the typical length of individual SWCNTs in such bundles is only about 300 nm

What happens when the bundle is naturally in atwisted form or can be assembled into twisted ropes?

Dong Qian, Gregory J Wagner, and Wing Kam Liu, Min-Feng Yu, Rodney S Ruoff, Mechanics of carbon nanotubes, Appl. Mech. Rev. 55, 495 (2002).

Wire Rope Users Manual

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Northwestern University Ruoff Group Nanotechnology Mechanics of Nanostructures (Conformational...

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