An Investigation into the Production and Application of Carbon nanofibers

By Russell PetrieSupervisor: Professor P J Hall

Introduction

Carbon PrecursorFiber Diameter vs. Surface AreaElectrospinning TechniqueHeat TreatmentsCharacterizationResultsConclusion

Carbon Precursor

Coal Tar pitch55ºC Softening PointFiltration and Distillationn-methyl pyrrolidinone solution

Fiber Diameter vs. Surface Area

Electrospinning Technique

15 kV Potential DifferenceRapid Diameter ShrinkageWater Bath

V

Protective plastic coverResistor

Plastic Syringe

Syringe Pump

High Voltage GeneratorCollector Plate

Stand

Hollow Needle

Heat Treatments

350ºC Stabilisation - Sets fiber structure and removes some organic compounds

1100ºC Carbonisation - Removes non-carbon elements including nitrogen

1500ºC Graphitisation - Little weight loss, aligns and improves crystallite structure in carbon fiber

Characterisation

Softening Point TestWeight LossBET surface areaSANS (Small Angle Neutron

Scattering)Microscopy

Results

The softening point is determined when the viscosity starts to rise sharply, this is usually in the region of 3500-4000 Pa.s

Softening Point Test

Distilled Flurastic PitchSample D3F4

0

1000

2000

3000

4000

230 245 260 275 290 305 320

Temperature (ºC)

Vis

cosi

ty (

Pa.

s)

Softening Point 245ºC

Weight Loss

350ºC Stabilisation - 26% weight loss350ºC - 1100ºC Carbonisation - 79% loss350ºC - 1500ºC Graphitisation - 70% loss

BET

N2 Adsorption at 77K

Type II Isotherm

HysteresisSurface Area

- 266m2/g

Isotherm Plot of 1100ºC Fiber

60

65

70

75

80

85

90

95

100

0 0.2 0.4 0.6 0.8 1

Relative Pressure (P/Po)

Vo

lum

e A

dso

rbed

(cm

3/g

) S

TP

Adsorption

Desorption

SANS

Data corrected for background and sample holder scattering Contrast matched using deutrerated toluene Data suggests non-porous structure

Contrast Matching of 1100ºC Carbon Nanofiber

0.01

0.1

1

10

100

1000

0.001 0.01 0.1 1

Scattering Wave Vector, q (Å-1)

Sca

tter

ing

in

ten

sity

, I(

q)

(cm

-1)

Contrast MatchedSample

Dry Sample

Microscopy

50x Magnification

Fig 1. Melt spun carbon fiber, 40m diameter

Fig 2. Fiber spun on glass slide

Fig 3. Fiber spun onto water

Fig 4. Stabilised fiber

Fig 2Fig 1

Fig 3 Fig 4

Conclusions

Novel technique to produce carbon nanofibers

Produces high surface area carbons without porous structure

Potential use in the fuel cell field as catalyst supports