KVS2002

Activated Nitrogen Activated Nitrogen Effect in Vertically Effect in Vertically

Aligned CNTAligned CNT

Tae-Young Kim, Kwang-Ryeol Lee, Kwang-Yong Eun*

Future Technology Research Division, Korea Institute of Science and Technology

*Thin Film Technology Research center, Korea Institute of Science and Technology

Carbon Nano-Tubes(CNT)Carbon Nano-Tubes(CNT)• Unique Structure and Properties

• Suggested Applications

Strength: bending strength

Young’s modulus: average 1.8TPa

Current Conductivity: resistivity<10-4 Ohm.cm

Thermal Conductivity: nearly that of diamond

Capillary effect…..

GPa0.82.14

Probe tip Field emitter Electrode in batteries Conducting wire

Synthesis of CNTSynthesis of CNT

• Arc discharge, Laser ablation, Plasma CVD, Thermal CVD

• Thermal CVDThermal CVD

Reaction hydro-carbon gas with metal catalyst particle

Environment gas affect CNT growthEnvironment gas affect CNT growth

Environment Gas EffectEnvironment Gas Effect

NN22 HH22 HH22+N+N22(3:2)(3:2)

300nm300nm

300nm300nm

3.00㎛3.00㎛

+ 2.4 vol. % C2H2

Growth of Vertically Aligned CNTsGrowth of Vertically Aligned CNTs

300nm300nm

2.4 vol. %2.4 vol. % C2H2 in H2 + N2 (3:1)

5.00㎛5.00㎛

16.7 vol. %16.7 vol. % C2H2 in NH3

H2+N2 vs. NH3

Environment gas effect

Ni particles after pretreatment for 1h…

Environment Gas Effect on CatalystEnvironment Gas Effect on Catalyst

Activated NitrogenActivated Nitrogen

Pretreatment Reaction(x)

H 2 , N 2 , H 2 +N 2, NH 3

Add C2H2 to the environmental gas

H2+N2 vs. NH3

Activated Nitrogen EffectActivated Nitrogen Effect•Activated nitrogen in NH3 environment play a significant role in the CNT growth kinetics.

Suggestion Suggestion : : Activated nitrogenActivated nitrogen Enhance formation of the graphitic layer on the catalystEnhance formation of the graphitic layer on the catalyst Enhance the separation of the graphitic layer from the Enhance the separation of the graphitic layer from the

catalyst surface.catalyst surface.

Purpose of Present WorkPurpose of Present Work• Research Reaction Kinetics and Growth MechanismReaction Kinetics and Growth Mechanism

of Vertically Aligned Carbon nano-tube in the view point of activated nitrogen.

When, Where, How does Activated Nitrogen affect CNT growth in overall process?.

A. Does nitrogen modify the surface of catalyst in pretreatment process?

B. Does nitrogen affect the CNT growth in reaction process?

Experimental ProcedureExperimental Procedure

Formation of Catalyst Particles

Thermal CVD

Tube type reactor with quartz tube (5800L) at 1 atm.

Procedure:

Sample loading after increasing temperature in Ar

PretreatmentPretreatment : for 1hr in H 2 , N 2 ,

H 2+N 2 , NH 3

ReactionReaction :C2H2 + environmental gas

Cooling in Ar

300nm300nm

When, Where, HowWhen, Where, How does Activated Nitrogen does Activated Nitrogen affect CNT growth in overall process?affect CNT growth in overall process?

A.A. Does nitrogen modify the surface of catalyst Does nitrogen modify the surface of catalyst in pretreatment process?in pretreatment process?

B. Does nitrogen affect the CNT growth in reaction Does nitrogen affect the CNT growth in reaction process?process?

Purpose of Present WorkPurpose of Present Work• Research Reaction Kinetics and Growth MechanismReaction Kinetics and Growth Mechanism

of Vertically Aligned Carbon nano-tube in the view point of activated nitrogen.

Ni catalyst Co catalyst

Catalyst Pretreatment Effect

NH3 pretreatment for 4hr, React C2H2+H2

Pretreatment Reaction

NH 3H2 + C2H2

Ni catalyst

Co catalyst

No pretreatment H2 pretreatment

Catalyst Pretreatment Effect

Pretreatment(x) Reaction

NH3 + C2H2

Pretreatment Reaction

H2NH3 + C2H2

Catalyst Pretreatment Effect

Reaction

PretreatmentH2+C2H2 NH3 +C2H2

H2 XO

NH3 + H2O

NH3X O

When, Where, HowWhen, Where, How does Activated Nitrogen does Activated Nitrogen affect CNT growth in overall process?affect CNT growth in overall process?

A. Does nitrogen modify the surface of catalyst in Does nitrogen modify the surface of catalyst in pretreatment process?pretreatment process?

B.B. Does nitrogen affect the CNT growth in Does nitrogen affect the CNT growth in reaction process?reaction process?

Purpose of Present WorkPurpose of Present Work• Research Reaction Kinetics and Growth MechanismReaction Kinetics and Growth Mechanism

of Vertically Aligned Carbon nano-tube in the view point of activated nitrogen.

0.170.17

0.2310.231

Reaction –Various C2H2 ratio ( X = C2H2/C2H2+NH3,, fixing NH3 100sccm)

Effect of NH3 Atmosphere in Reaction

0.050.05

Pretreatment Reaction

H2NH3 + C2H2

0.0150.015

Activated Nitrogen in CNT

Fixing NH3 flux 100sccm

Role of Nitrogen in CNTRole of Nitrogen in CNT

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PRB. VOLUME 59, 5162PRB, VOLUME 64, 235401

Surface modification of catalyst by activated Surface modification of catalyst by activated nitrogen would not affect the vertically aligned nitrogen would not affect the vertically aligned CNT growth.CNT growth.

Activated nitrogen in CNT would have relation Activated nitrogen in CNT would have relation with CNT growth rate.with CNT growth rate.

----Activated nitrogen incorporated into the CNTActivated nitrogen incorporated into the CNT

would would decrease the activation energy ofdecrease the activation energy of CNT formation.CNT formation.

ConclusionConclusion