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Carbon Fibres from CelluloseJoining FP1205 and MP1206 “Electrospinning”
Stephen EichhornCollege of Engineering and Physical Sciences, University of Exeter
AcknowledgementsDr Libo Deng (Schenzen Institute for Advanced Technology, China)Dr Tommy Shyng (Exeter)Dr Kenny Kong (Nottingham)Professor Yanqiu Zhu (Exeter)Dr Anna Lewandowska (Exeter)Professor Robert Young (Manchester)Professor Ian Kinloch (Manchester)
EPSRC for funding “Hybrid Electrospun Fibres from Biomass-Based Carbon Nanostructures” (2008 – 2013)
EPSRC Centre for Innovative Manufacturing in Composites –follow on funding for feasibility study (2013)
Why Carbon?
Most relevant market segments for new low cost CFs and 2020 forecast per macro-area (Composites World’s annual Carbon Fibre 2011 conference, Washington, D.C., Dec. 5-7th 2011)
Various estimates on use suggest growth rates of 13%/year with a total global market worth $2.3bn by 2015
What precursors?• PAN (poly acrylonitrile) – oil based, non-renewable,
industrially proven and commercial, high modulus/strength, process produces toxins.
• Pitch – oil-based, industrially proven, high strength.• Lignin – non-oil-based, renewable, some industrial
proven technology (Oak Ridge, Innventia), low/medium modulus/strength.
• Cellulose – non-oil-based, renewable, industrially proven (Union Carbide), low-medium modulus.
• Polyethylene – oil or non-oil-based, not industrially proven yet (some activity from Oak Ridge), low strength/modulus.
Summary of Talk• Raman spectroscopy of carbon• Carbon nanostructures from cellulose• Introduction to materials
– Electrospun cellulose fibres– SiC/carbon fibres– SWNT/MWNT/cellulose
• Carbonisation of cellulose fibres• Carbonisation of electrospun fibres• Supercapacitance• Conclusions
Raman Spectroscopy - Carbon• Raman effect occurs due to inelastic
scattering of light• Two first-order Raman bands that
are present; D-band centred at ~1350 cm-1 and the G band located at ~1590 cm-1. Generally, the G band is considered to be an in-plane bond stretching motion of sp2-hybridised C atoms and the D band is related to the breathing mode of the six-fold aromatic ring near the basal edge
• At higher carbonisation temperatures (>2000°C) a G’ band is present –seen also in carbon nanotubes and graphene
• Various spectral indicators of graphitisation – one is the ID/IG ratio. Undergoes a transition for cellulose
500 1000 1500 2000 2500 3000 3500
4
G´
D´
G
Inte
nsity
, a.u
.
Raman Shift, cm-1
DB
Ferrari & Robertson (2000) PRB 61 14095
Carbon Fibres from Cellulose
Tang & Bacon (1964) Carbon 2, 211; ibid 221
Carbon Fibres from Cellulose
Zickler et al. (2006) Carbon 44 3239–3246
Data for a range of PAN and cellulose fibres
<2 nm: ID/IG=kLa2
>2nm: ID/IG=kL-1
Ferrari & Robertson (2000) PRB 61 14095
Carbon fibres from Cellulose Nanostructures
Kim et al. (2001) Carbon 39, 1051-1056
Kaburagi et al. (2012) Carbon 50, 4757-4760
Various forms of cellulose nanofibres have been converted to carbon eg. Bacterial cellulose, tunicate etc.
Electrospun Cellulose FibresCellulose acetate fibres
De-acetylated cellulose acetate fibres
• Cellulose acetate fibres electrospun in DMAc/acetone mix
• Fibres spun onto a rotating mandrel
• Mean fibre diameters were ~300 nm
Deng et al. (2013) Carbon, 58, 66-75
SiC/C Nanofibres
• Electrospun cellulose nanofibres were carbonised (grey sheet) above a bed of SiO2 beads or SiC whiskers. Pyrolysis temperature – 1500 °C for 2.5 hours under an Ar atmosphere
• After pyrolysis SiC nanostructures were observed.
• SiC structures can be formed through the carbothermal reduction of silica according to
SiO2 + 3C→SiC + 2CO
Essentially this comprises two sub-reactions with an intermediate formation of SiO
Deng et al. (2013) Carbon, 58, 66-75
Deacetylation of Fibres
3500 3000 2500 2000 1500 100040
60
80
100
Tran
smis
sion
(%)
Wavenumber (cm-1)
CA Deacetylated CA
1746 cm-1a
800 900 1000 1100 1200 1300 1400 15000
2000
4000
6000
8000
10000
12000
Inte
nsity
(arb
.uni
t)
Raman shift (cm-1)
CA Deacetylated CA
b
Both infrared and Raman spectra indicate that the fibres are de-acetylated to cellulose
5 10 15 20 25 30 35 40
0
1000
2000
3000
4000
5000
Inte
nsity
2
CA Deacetylated CA
(101)
(101)(002)
Structure Developmenta b c
d e
5 nm 5 nm 5 nm
5 nm
(a) 800 ºC(b) 1000 ºC,(c) 1200 ºC,(d) 1500 ºC (e) 2200 ºC.
Deng et al. (2013) Carbon, 58, 66-75
Structure Development
500 1000 1500 2000 2500 3000
800 C
1000 C
1200 C
1500 C
2200 C
Inte
nsity
Raman shift (cm-1)
a
0.5 1.0 1.5 2.0 2.5 7 8 9
0.6
0.8
1.0
1.2
1.4
1.6
I D/I G
La (nm)
c
Deng et al. (2013) Carbon, 58, 66-75
Universal Band Shifts - Carbon
Huang & Young (1995) Carbon 33, 97-107
Universal Band Shifts - Carbon
Frank, Tsoukleri, Riaz, Papagelis, Parthenios, Ferrari, Geim, Novoselov, Galiotis (2011) Nature Comm. 2 255
Micromechanics of carbon nanofibres
-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.72660.2
2660.4
2660.6
2660.8
2661.0
2661.2
2661.4
2661.6
G'-b
and
posi
tion
(cm
-1)
Strain (%)
-3 cm-1/%
a
-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
2660.5
2661.0
2661.5
2662.0
2662.5
G'-b
and
posi
tion
(cm
-1)
Strain (%)
-5 cm-1/%
b
1500 °C; ~ 60 GPa 2200 °C; ~ 100 GPa
Deng et al. (2013) Carbon, 58, 66-75
Fibre Density
(g cm-3)
Elongation
at break
(%)
Tensile
Strength
(MPa)
Young’s
modulus
(GPa)
Specific
Modulus GPa
cm3 g-1
E-glass 2.5 2.5 2000 – 3500 70.0 28
Carbon 1.4 1.4 – 1.8 4000+ 230.0+ 234+
Our fibres 1.4(?) ? ? 100 71
SiC/C composite fibres
500 1000 1500 2000 2500 3000 3500
-SiC
G´
D´
G
Inte
nsity
, a.u
.
Raman Shift, cm-1
5
D
600 650 700 750 800 850 900 950 1000
Inte
nsity
, a.u
.
Raman Shift, cm-1
-SiCTO
LO
5
A B
?
Pyrolysed SWNT/cellulose electrospun fibres
500 1000 1500 2000 2500 3000 3500
4RBM
Inte
nsity
, a.u
.
Raman Shift, cm-1
G´
D´
GD
500 1000 1500 2000 2500 3000 3500
4RBM
Inte
nsity
, a.u
.
Raman Shift, cm-1
3
2
1
G´D´
GDA B
Carbon nanotube fingerprint (RBMs) are still visible inside a pyrolysedcarbon fibre
Carbon Nanotubes
(8,7)
(11,4)
Carbon nanotubes have what is called chirality
Chirality of nanotubes depends on how you role up the graphene sheet in order to make a tube
Nanotubes with different chiralities have different electronic properties (metallic, semiconducting etc)
Most samples of carbon nanotubes contain a variety of tubes of different chiralities
Methods must be employed to separate nanotubes in order to generate electroninc devices etc.
Radial Breathing Modes (RBMs)
= 785 nm = 632 nm
200 220 240 260 280 3005000
10000
15000
20000
25000 272268
238232
210Inte
nsity
Raman shift (cm-1)180 200 220 240 260 280 300 320 340
0
5000
10000
15000
20000
25000
30000
292
261223
199
Inte
nsity
Raman shift (cm-1)
HiPco
• The HiPco material contains a range of different sizes of nanotubes• Different ones are in resonance with the different lasers
RBMs in our Fibres
180 200 220 240 260 280 300 320 3401,6
1,8
2,0
2,2
2,4
2,6
ESE22
EME11
ESE33
218.5
Opt
ical
Tra
nsiti
on E
nerg
y E ii, e
VRBM position, cm-1
2.33 eV274
290
264
A B
150 200 250 300 350 400 450
427
626
1216
Inte
nsity
, a.u
.
Raman Shift, cm-1
281
254
217
255
218 27
529
328
1
218
3
2
1
Prabharakaran, Eichhorn & Young (2007) Nanotechnology, 18, 235707. Prabharakaran, Young & Eichhorn (2008) Small, 4, 930-933.
Can “see” individual CNTs in fibres in resonance with the laser!
MWNTs/Cellulose Electrospun
5 m 5 m
• Cellulose fibres electropsun with/without the presence of MWNTs (0.5 -1.5%)• Fibres were de-acetylated as before• Fibres then
Stabilised (at 240 °C) in air, followed by Carbonised (at 1000 °C) in Ar, followed by Activated in steam/Ar (at 800 °C) – making ACNFs (Activated
Carbon Nanofibres)
Deng et al. (2013) – ACS Appl Mater Interf – in press
TEM of samples• Can see MWNTs inside
fibres
• Would not be able to image SWNTs – contrast not good enough in TEM between Cellulose/MWNTs
• MWNTs protude from the fibre surfaces
• Some alignment of the nanotubes noted
Preparation of SupercapacitorElectrodes
ACNFs ground & mixed with 10% of carbon black (CB) and 10% of PVDF binder. + small amount of NMP produce a paste
Paste cast onto Ni foam, dried under vacuum at 50 °C for 24 h and pressed under a pressure of 7 MPa to make electrodes.
Supercapacitor cells were built by assembling two pieces of 1.0 cm2
electrode, with a Whatman filter paper as a separator, in a coin cell containing 6 M aqueous KOH as the electrolyte.
The loading of ACNF in each electrode was 3 mg.Cyclic voltammetry (CV) and galvanostatic charge/discharge
measurements of the as-built supercapacitor cells were carried out using an Iviumstat Electrochemical Interface.
Electrochemical Impedance Spectroscopy (EIS) analysis was carried out using a Solartron 1287 Electrochemical Interface, in the frequency range from 0.1 Hz to 100 kHz at an open circuit potential with an AC amplitude of 10 mV.
CV Curves and Capacitance
Sample Crystallinitya Activationenergy (kJmol-1)b
ID/IG Specificsurfacearea(m2 g-1)
Electricalconductivity(S m-1)
RS () Rct () Specificcapacitance(F g-1)c
ACNF 60% 22920 1.210.08 86520 101095 0.380.03 0.370.03 105102%MWNT/ACNF
61% 21820 1.250.1 91023 1120104 0.350.03 0.340.03 12111
4%MWNT/ACNF
62% 20918 1.280.12 105020 1185110 0.330.03 0.320.03 13612
6%MWNT/ACNF
64% 182 17 1.310.08 112025 1255100 0.300.03 0.310.03 14511
Specific capacitances comparable with those derived from poly(acrylonitrile), poly(benzimidazole) and polyimide nanofibers
Comparable with those of cornstalk-carbon
Lower than coconut shell but critically more stable under cycling
Conclusions• We need new precursors for carbon fibre production• Some interesting and potentially useful carbon fibres can
be made from cellulose• Electrospinning offers a way to make fine structured
carbon fibres – volume production for electrospinningand shrinkage an issue
• Modulus of fibres looks promising. Lots of work to do improving processing
• Catalysis of graphitization possible using SiC/SWNTs• Potential for making new family of carbon fibres for
applications (automotive composites, batteries, supercapacitors)
Topsham (near Exeter), February 2013
Thankyou for listening
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