Carbon Nanotube Growth Enhanced by Nitrogen Incorporation Tae-Young Kim a), Kwang-Ryeol Lee, Kwang Yong Eun and Kyu-Hwan Oh a) Future Technology Research Division, Korea Institute of Science and Technology a)Department of Materials Engineering, Seoul National University

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….. Probe tipField emitterElectrode in batteriesConducting wire

Synthesis 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 growth Most previous results using the CVD process showed that the vertically aligned CNTs were obtained in N 2 or NH 3 gas environments, which reveals the key role of nitrogen in CNT growth

Synthesis condition CNT MorphologyCitation method Temperatue( o C)Reaction GasCatalyst PE-CVD666C 2 H 2 +NH 3 NiAligned CNTScience 282, 1105 (1998) PE-CVD660C 2 H 2 +NH 3 NiAligned CNTAPL (1999) PE-CVD825C 2 H 2 +NH 3 CoAligned CNTAPL (2000) Thermal-CVD750~950C 2 H 2 +NH 3 FeAligned CNTAPL (2000) PE-CVD825C 2 H 2 +NH 3 CoAligned CNTAPL (2000) Thermal-CVD800C 2 H 2 +NH 3 FeAligned CNTAPL (2001) Thermal-CVD 950C 2 H 2 +NH 3 Ni, Co Aligned CNT TSF (2001) 850 C 2 H 2 +H 2, C 2 H 2 +N 2 Tangled CNT Thermal-CVD 950C 2 H 2 +NH 3 Ni Aligned CNT DRM (2001) 950C 2 H 2 +H 2, C 2 H 2 +N 2 Tangled CNT Thermal-CVD 800~900C 2 H 2 +NH 3 Ni Aligned CNT JAP (2002) 600~900C2H2+H2C2H2+H2 Tangled CNT PE-CVD660<C 2 H 2 +NH 3 NiAligned CNTAPL (2002) Thermal-CVD850~900C 2 H 2 +ArNi, CoTangled CNTAPL (1999) PE-CVD500CH 4 +N 2 Fe, NiAligned CNTAPL (1999) PE-CVD550CH 4 +N 2 FeAligned CNTJAP (2001) PE-CVD700CH 4 +H 2 NiAligned CNTAPL (2000) Thermal-CVD800ferrocene+xylene Fe Aligned CNTAPL (2000) Environment gas effect in CNT growth

Environment Gas Effect N2N2N2N2 H2H2H2H2 H 2 +N 2 (3:2) 300nm 3.00 ㎛ vol. % C 2 H 2 CNT did not grow in N 2, H 2 and their mixture gas environment

Growth of Vertically Aligned CNTs 300nm 2.4 vol. % 2.4 vol. % C 2 H 2 in H 2 + N 2 (3:1) 5.00 ㎛ 16.7 vol. % 16.7 vol. % C 2 H 2 in NH 3 H 2 +N 2 vs. NH 3 Environment gas effect But Vertically aligned CNTs grow in an NH 3 environment

Ni particles after pretreatment for 1h… Environment Gas Effect on Catalyst Activated Nitrogen Pretreatment Reaction(x) H 2, N 2, H 2 +N 2, NH 3 Add C 2 H 2 to the environmental gas H 2 +N 2 vs. NH 3 Nitrogen peak was observed only in an NH 3 environment

Activated Nitrogen Effect Activated nitrogen in NH 3 environment play a significant role in the CNT growth kinetics. Suggestion : Activated nitrogen Enhance formation of the graphitic layer on the catalyst Enhance formation of the graphitic layer on the catalyst Enhance the separation of the graphitic layer from the catalyst surface. Enhance the separation of the graphitic layer from the catalyst surface.

Purpose of Present Work Reaction Kinetics and Growth MechanismResearch Reaction 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 Procedure Formation of Catalyst Particles Thermal CVD Tube type reactor with quartz tube (5  800L) at 1 atm. Procedure:  Sample loading after increasing temperature in Ar  Pretreatment  Pretreatment : for 1hr in H 2, N 2, H 2 +N 2, NH 3 Reaction  Reaction :  C 2 H 2 + environmental gas  Cooling in Ar 300nm

Purpose of Present Work Reaction Kinetics and Growth MechanismResearch Reaction Kinetics and Growth Mechanism of Vertically Aligned Carbon nano-tube in the view point of activated nitrogen.

Catalyst Pretreatment Effect Reaction Pretreatment H 2 +C 2 H 2 NH 3 +C 2 H 2 H2H2 NH 3 + H 2 NH 3 Pretreatment in an NH 3 environment is neither a sufficient nor a necessary condition for the vertically aligned CNT growth

Purpose of Present Work Reaction Kinetics and Growth MechanismResearch Reaction Kinetics and Growth Mechanism of Vertically Aligned Carbon nano-tube in the view point of activated nitrogen.

Reaction –Various C 2 H 2 ratio ( X = C 2 H 2 /C 2 H 2 +NH 3,, fixing NH 3 100sccm) Effect of NH 3 Atmosphere in Reaction 0.05 Pretreatment Reaction H2H2 NH 3 + C 2 H Pretreatment in an NH 3 environment is neither a sufficient nor a necessary condition for the vertically aligned CNT growth

Activated Nitrogen in CNT Fixing NH 3 flux 100sccm Nitrogen concentration in CNT increased with increasing CNT growth rate and the degree of alignment, which exhibits an intimate relationship between CNT growth and nitrogen incorporation Nitrogen in the CNT is chemically bonded with the carbon atoms of the graphitic basal plane.

Role of Nitrogen in CNT PRB. VOLUME 59, 5162 PRB, VOLUME 64, Nitrogen incorporation to the CNT would reduce the strain energy (E str ) required to form a tubular graphitic layer. The reduced strain energy would in turn enhance the nucleation rate of the graphitic layer on the curved catalyst surface. Further CNT growth also requires continuous deposition of the tubular graphitic layer, where nitrogen incorporation can reduce the strain energy

Surface modification of catalyst by activated nitrogen would not affect the vertically aligned CNT growth. Surface modification of catalyst by activated nitrogen would not affect the vertically aligned CNT growth. Activated nitrogen in CNT would have relation with CNT growth rate. Activated nitrogen in CNT would have relation with CNT growth rate. -- Activated nitrogen incorporated into the CNT -- Activated nitrogen incorporated into the CNT would decrease the activation energy of would decrease the activation energy of CNT formation. CNT formation. Conclusion