Engineering Carbon Nanotube Fibers by a Mechanical Twisting

Method

Graduate Research Mentor, Ji Hao, Northeastern UniversityGary Hu, YSP Student, North Quincy High SchoolJames Zhou, YSP Student, Andover High School

Professor Yung Joon Jung, Mechanical and Industrial Engineering, Northeastern University

Carbon Nanotubes (CNTs)High tensile strengthStiffest material yet discoveredHigh strength to weight ratio

What’s the Problem?Current applications limitedStrength does not scaleManufacturing deformitiesPoor alignment

Twisting FibersImproves alignmentIncreases uniformityDistributes forceGreater strength

PurposeTo design a fiber twisting

apparatusTo compare mechanical

properties of twisted and untwisted fibers

To investigate the morphological effect of twisting fibers

Our FiberMicroscopic image of pristine CNT fiber (Diameter: ~800μm) (bottom left)SEM image inside small bundles of CNT (Diameter: ~10-100nm) (bottom right)TEM image of individual DWNTs and TWNTs (Diameter: ~5nm) (upper right)

STP-PWR-3204 (power source)

STP-DRV-405(micro-

stepping drive)

6221 SourceMeter(DC source)

DWNT/TWNT fibers

STP-MTR-17040(micro-

stepping motor)

AC 110V(outlet)

Computer with

LabVIEW2011 SP1

Schematic of the Motor Setup

(b) Overhead view of the fiber clamps(a) Entire motor system

(c) Fiber cutting procedure

Morphological Data

Larger twisting angles

Smaller diameter

Greater fraying

20 30 40 50 60

24

28

32

36

40 Twisting angle Diameter

Cycles

Tw

istin

g an

gle

of tw

iste

d C

NT

fibe

r (d

egre

e)

130

140

150

160

170

Dia

met

er o

f tw

iste

d C

NT

fibe

r (

m)

(b) The dependence of fiber diameter on the number of cycles

(a) The dependence of twisting angle on the number of cycles

Mechanical Testing DataMore cycles

—stronger fiber

Occasional failure

Conclusion and Future WorkTwisted fibers have higher

performanceFraying and other defects limit

the extent of useful twistingImprove setupReduce deformitiesChange motor frequencyControl angle and diameter

individually

AcknowledgementsCenter for STEM EducationYoung Scholars Program & Team

Claire Duggan – DirectorMaureen Cabrera, Madeline Leger – YSP Coordinators

Yung Joon Jung – Advising professor

Ji Hao – Graduate student mentor

References

Kai Liu et al, Nanotechnology 21, 045708 (2010).

Yu MF et al, Science 287, 637–640 (2000).

Zhang M, Atkinson KR and Baughman RH, Science 306, 1358-1361 (2004).

Any questions?