Bottom up method for Bottom up method for preparing preparing nanostructuresnanostructures: :

growth of carbon growth of carbon nanotubesnanotubes

Akos KukoveczAkos KukoveczUniversität Wien 2002Universität Wien 2002

2/30

Talk layoutTalk layout

•• CarbonCarbon nanotube nanotube basicsbasics•• Overview Overview of of the synthesis techniquesthe synthesis techniques•• NT growth NT growth theories theories & & modelsmodels•• Application oriented Application oriented growth growth –– examplesexamples•• PurificationPurification

3/30

Carbon Carbon nanotube nanotube basicsbasics

(10,5) SWCNT(10,5) SWCNT

C(n,m) : C(n,m) : chiral vector diameterchiral vector diameter, , electrical propertieselectrical properties

FromFrom thethe websitewebsite of Dr. of Dr. MaruyamaMaruyama..

SWCNT: SWCNT: rolledrolled--up grapheneup graphene sheetsheetdiameterdiameter: ~0.7: ~0.7--3 nm, 3 nm, length length > 500 nm> 500 nm

R. R. Saito Saito et al.: et al.: Physical Properties Physical Properties of of Carbon NanotubesCarbon Nanotubes, Imperial Press, London, 1999,, Imperial Press, London, 1999,

4/30

SWCNT SWCNT morphologymorphology

Synthesis Synthesis yields entagled mat yields entagled mat of nanotube of nanotube bundlesbundles

Science, Science, 273273, 483., 483.

5/30

Multi wall Multi wall carboncarbon nanotubesnanotubesCoCo--axial axial set set of of increasing diameterincreasing diameter SWCNTsSWCNTs

•• Easier synthesis thanEasier synthesis than SWCNTsSWCNTs•• Accurate quality control is evenAccurate quality control is evenmore difficultmore difficult

6/30

Talk layoutTalk layout

•• Carbon Carbon nanotube nanotube basicsbasics•• Overview Overview of of the synthesis techniquesthe synthesis techniques•• NT growth NT growth theories theories & & modelsmodels•• Application oriented Application oriented growth growth –– examplesexamples•• PurificationPurification

7/30

Synthesis of Synthesis of multi multi wall wall tubestubes

•• No No catalyst neededcatalyst needed•• MWCNT in MWCNT in cathode depositcathode deposit, , •• dd = 2= 2--25 nm, 25 nm, ll ≤≤ 1 1 µµmm

PropertiesProperties

•• d.c. d.c. arcarc, 20 V, 100 A, 20 V, 100 A•• 500 500 torr torr He 10 ml/sHe 10 ml/s•• electrodeelectrode distance 1 mmdistance 1 mm•• ~3000 °C in ~3000 °C in plasmaplasma

ParametersParameters

SetupSetup

d.c. d.c. arcarc

•• Co/Co/graphitegraphite: 100 nm, 60 : 100 nm, 60 µµmm•• Co/SiOCo/SiO22: 30 nm, 10 : 30 nm, 10 µµmm•• Fe: Fe: more amorphous carbonmore amorphous carbon•• Ni, Cu: no Ni, Cu: no nanotubesnanotubes

••55--10 % C10 % C22HH22, C, C66HH66 in Nin N22, Ar, Ar•• Co (Fe, Ni) @ Co (Fe, Ni) @ MgOMgO, Al, Al22OO33, , SiOSiO22, , zeoliteszeolites, , graphitegraphite etc.etc.•• 700700--1100 °C, 1 atm1100 °C, 1 atm

Vapor depositionVapor deposition (CVD)(CVD)

APA APA 6767 1.1.

8/30

SWCNT SWCNT synthesissynthesis

CatalystCatalyst??nono

Exotic methodsExotic methods

9/30

Exotic Exotic SWCNT SWCNT synthesis synthesis I.I.

CH3

CH3

CH3

N

TPA TPA is template foris template forAlPOAlPO44--5 5 synthesissynthesis

AlPOAlPO44--5 5 is is a a zeolitezeoliteanalogoue analogoue

Pyrolysis Pyrolysis (550 (550 °°C) C) transformstransforms TPATPA intointo SWCNTSWCNT

APA APA 6969 381.381.

AlPOAlPO44--55

PyrolizedPyrolized

10/30

Exotic Exotic SWCNT SWCNT synthesis synthesis II.II.Coalescence Coalescence of Cof C6060 molecules into molecules into SWCNT SWCNT within thewithin the

nanospace nanospace of a of a larger larger SWCNT (SWCNT (peapod peapod system).system).

HeatingHeating: : vacuumvacuum, 1000 , 1000 °°C, 14 C, 14 hourshours CPL CPL 337 48.337 48.

FromFrom thethe websitewebsite of Dr. of Dr. MaruyamaMaruyama..

11/30

SWCNT SWCNT synthesissynthesis

nonoExotic methodsExotic methods

yesyes

In In situ generatedsitu generated??nono

CVDCVD

CatalystCatalyst??

12/30

ChemicalChemical vaporvapor deposition deposition (CVD)(CVD)

NTs grow from the NTs grow from the metal metal clustersclusters..Metal Metal clusters can be positioned by clusters can be positioned by e.g. e.g. litographylitography, , ink printingink printing, , laser etchinglaser etching......

APA APA 6767 1.1.

UniqueUnique: NT growth NT growth location controlledlocation controlled!: !

SWCNTSWCNTd=1.4 nm, l>10 d=1.4 nm, l>10 µµmm

•• strongstrong metalmetal--support support interactioninteraction

•• large surface arealarge surface area•• large mesopore volumelarge mesopore volume

Fe/Mo @ Fe/Mo @ aluminaaluminaCo @ Co @ MgOMgO

800800--1000 1000 °°CCCHCH44: 1 dm: 1 dm33/min/min

ProductProductCatalystCatalystParametersParameters

13/30

SWCNT SWCNT synthesissynthesis

nonoExotic methodsExotic methods

yesyes

In In situ generatedsitu generated??nono

CVDCVD yesyes

Starting phaseStarting phase??solidsolid

•• d.c. d.c. arc dischargearc discharge•• pulsed laser vaporization pulsed laser vaporization (PLV)(PLV)

CatalystCatalyst??

14/30

d.c. d.c. arc dischargearc dischargeSWCNTsSWCNTs: in : in sootsoot, , collarettcollarett..

ConditionsConditions: : as for as for MWCNT.MWCNT.

Anode Anode contains catalystcontains catalyst!!

Good SWCNT Good SWCNT yieldyield::Co, Co/Ni, Co/Fe, Ni/Y, Ni/FeCo, Co/Ni, Co/Fe, Ni/Y, Ni/Fe

Product:Product: diameter controldiameter control notnot straightforwardstraightforwardtubes often covered with amorphous carbontubes often covered with amorphous carbon

15/30

Pulsed laserPulsed laser vaporizationvaporization (PLV)(PLV)

target Collectorlaser

He (Ar)

SWCNTSWCNTd=1.4 nm, l>10 d=1.4 nm, l>10 µµmm

GraphiteGraphite+0.5% +0.5% catalystcatalyst (Ni, Co)(Ni, Co)

T = 1200 °CT = 1200 °C2 2 successive pulsessuccessive pulses

ProductProductTargetTargetParametersParameters

Good Good diameter controldiameter control, , little amorphous carbonlittle amorphous carbon..APA APA 6767 1.1.

16/30

SWCNT SWCNT synthesissynthesis

nonoExotic methodsExotic methods

yesyes

In In situ generatedsitu generated??nono

CVDCVD yesyes

Starting phaseStarting phase??solidsolid

•• d.c. d.c. arc dischargearc discharge•• pulsed laser vaporization pulsed laser vaporization (PLV)(PLV)

gasgas

•• flame pyrolysisflame pyrolysis•• gas gas phase phase decompositiondecomposition

CatalystCatalyst??

17/30

Flame Flame pyrolysispyrolysisContinuous productionContinuous production, , familiar familiar plant engineering plant engineering --> CHEAP!> CHEAP!

SWCNTs growSWCNTs grow in in sooting flamesooting flame: O: O22++fuelfuel++catalystcatalyst. .

NT NT yieldyield < 1%< 1%Mostly SWCNTsMostly SWCNTs

FuelFuel: C: C22HH22, C, C66HH66 11--3 dm3 dm33/min + x(2/min + x(2--4) O4) O22CatalystCatalyst: : ferrocenesferrocenes, , metallocenesmetallocenes, Fe(NO, Fe(NO33))33TTflameflame=1200 =1200 °°C, p=80 C, p=80 TorrTorr, t=250 ms, t=250 ms JPC B JPC B 104104 9615.9615.

18/30

Gas Gas phase catalytic decompositionphase catalytic decompositionContinuous productionContinuous production --> > low costlow cost!!Carbon sourcesCarbon sources:: hexanehexane,, benzenebenzene,, acetyleneacetylene, CH, CH44, CO,..., CO,...Catalyst precursorsCatalyst precursors: metal: metal--carbonylscarbonyls & & metallocenesmetallocenes

HiPCO processHiPCO processCO: CO: 10 atm10 atm

1 dm1 dm33/min/minFe(CO)Fe(CO)55: 5 : 5 ppmppm

d = 0.7d = 0.7--1.4 nm1.4 nml > 1 l > 1 µµmm

BoudouardBoudouard: 2 CO : 2 CO C + COC + CO2 TresholdTreshold: 500 : 500 °°CCn Fe(CO)n Fe(CO)55 = = FeFenn + 5n CO + 5n CO TresholdTreshold: 250 : 250 °°CC

CPL CPL 313313 91.91.

19/30

Talk layoutTalk layout

•• Carbon Carbon nanotube nanotube basicsbasics•• Overview Overview of of the synthesis techniquesthe synthesis techniques•• NT growth NT growth theories theories & & modelsmodels•• Application oriented Application oriented growth growth –– examplesexamples•• PurificationPurification

20/30

Nanotube growth Nanotube growth theoriestheories

Common Common pointspoints::

•• All All go go to to atomization temperatureatomization temperature

Hexagonal spHexagonal sp22 graphite is the mostgraphite is the moststablestable form of form of carboncarbon..

•• ConstrainConstrain ::Steric limit Steric limit / / catalyst presentcatalyst present

Nanotubes insteadNanotubes insteadofof graphene sheetsgraphene sheets!!

Are Are they really they really so different?so different?

21/30

Possible Possible growth growth arrangementsarrangements

Root Root growth: VLSgrowth: VLSTip growth: Tip growth: scooterscooter SkullcapSkullcap

CC CC

CC

Grow

th G

rowth directio n

directio n

CCCC

CC

Grow

th G

rowth directio n

directio n

CC CC

CC

Grow

th G

rowth directio n

directio n

22/30

Tip growth: Tip growth: scooter modelscooter model

TEM: no metal in NT TEM: no metal in NT tiptip

Co (Ni) Co (Ni) atom cyclesatom cycles: : C C atoms add atoms add toto hexagonshexagons

Co (Ni) Co (Ni) atom stops atom stops (e.g. (e.g. gets too largegets too large): ): Dangling bonds make pentagonsDangling bonds make pentagons, , close domeclose dome..

Topics in Topics in ApplAppl. Phys. . Phys. 8080 55.55.

23/30

Root Root growth: VLS growth: VLS modelmodel

VaporVapor--LiquidLiquid--Solid (VLS)Solid (VLS) modelmodel

NTs grow radially from NTs grow radially from NiNi--carbid particecarbid partice..

TEMTEM

Carbon from vapor phase dissolves Carbon from vapor phase dissolves in in liquid metal liquid metal nanoclusternanocluster, , then segregates then segregates on on cluster surface cluster surface to to give give solid solid nanotubesnanotubes..

PRL PRL 8787 275504.275504.

24/30

RootRoot growth: MD growth: MD simulationsimulationI.I. NucleationNucleation

Red: Red: CoCoGray: Gray: CC

2000 K2000 KHomogeneous distrHomogeneous distr..

1500 K1500 KC C segregates segregates to to surfacesurface25 25 psps

Aromatic Aromatic ringsrings

1500 K1500 K

15 15 psps

5 5 new new C C enter the enter the tubetube

II. GrowthII. Growth PRL PRL 8787 275504.275504.

25/30

SkullcapSkullcap growth: MD growth: MD simulationsimulationNi Ni cluster cluster ((blueblue): d=1.2 nm): d=1.2 nmFree C Free C atoms atoms come come from from gas.gas.

FromFrom thethe websitewebsite of Dr. of Dr. MaruyamaMaruyama..CPL CPL 260260 471.471.

26/30

Talk layoutTalk layout

•• Carbon Carbon nanotube nanotube basicsbasics•• Overview Overview of of the synthesis techniquesthe synthesis techniques•• NT growth NT growth theories theories & & modelsmodels•• Application oriented Application oriented growth growth –– examplesexamples•• PurificationPurification

27/30

Application oriented Application oriented growth: CVDgrowth: CVDElectronic Electronic industry can industry can not not use random use random NT NT matsmats!!

SWCNT gas SWCNT gas sensorsensor

1010 ppm rangeppm range

0.1 % 0.1 % rangerange

SWCNT SWCNT network between network between Si Si pillarspillarsAPL APL 8181 2261.2261.

•• Field emission displaysField emission displays

•• FET FET mass productionmass production

28/30

Talk layoutTalk layout

•• Carbon Carbon nanotube nanotube basicsbasics•• Overview Overview of of the synthesis techniquesthe synthesis techniques•• NT growth NT growth theories theories & & modelsmodels•• Application oriented Application oriented growth growth –– examplesexamples•• PurificationPurification

29/30

Nanotube Nanotube purificationpurificationI.I. Contaminants: catalyst metal & amorphous carbonContaminants: catalyst metal & amorphous carbon

II.II. Removal: metals by dissolving in acid (HCl, HNORemoval: metals by dissolving in acid (HCl, HNO33))

carbon by selective oxidation (Ocarbon by selective oxidation (O22, wet air, , wet air, HNOHNO33, H, H22OO22 etc.)etc.)

III.III. Challanges: Challanges: NTs not soluble in any solventNTs not soluble in any solvent

sonication can break NTssonication can break NTs

thin NTs sensitive to oxidationthin NTs sensitive to oxidation

30/30

Thanks for your attentionThanks for your attention!!

AkoskaAkoska®®