Novel Dispersion and Self- Assembly of Carbon Nanotubes of Carbon Nanotubes Mohammad F. Islam Department of Chemical Engineering and Department of Chemical Engineering and Department of Materials Science & Engineering 100g 100g http://islamgroup.cheme.cmu.edu Korea-US NanoForum 2010, Seoul, Korea A April 5-6, 2010 il 5 6 2010 Funding Agencies NSF: CBET- 0708418, DMR- 0619424 and DMR- 0645596 ACS PRF ACS- PRF Sloan Foundation DARPA
Outline Outline • Introduction to Soft Materials I d i S f M i l • Single Wall Carbon Nanotubes (SWNTs) g • Purification, Dispersions and Their Properties • Carbon Nanotube Aerogels • Carbon Nanotube Aerogels • Conclusions
Soft Materials Soft Materials - - Introduction Introduction
Introduction to Single Wall Carbon Nanotubes Introduction to Single Wall Carbon Nanotubes Diamond Diamond C60 C60 “Buckminsterfullerene” “Buckminsterfullerene” Single wall Carbon Single wall Carbon Graphite Graphite Nanotube ( Nanotube (SWNT SWNT) Multiwall Carbon Multiwall Carbon Nanotube ( Nanotube (MWNT MWNT) )
SWNTs have extraordinary anisotropic properties SWNTs have extraordinary anisotropic properties ~ 1 nm 1 100 nm – 10,000 nm SWNT Strength (~100x Steel) Electrical Conductivity (~Copper) Tensile strength ~200 GPa Stiffness ~1 TPa Dekker et al. , Nature 386 , 474 (1997) Elongation ~30% Salvetat et al. , PRL 82 , 944 (2000) Thermal Conductivity ~3x Diamond Incorporate anisotropic properties of SWNTs into composites
Challenges Challenges • Large scale production of clean nanotubes. • H • Homogeneous dispersion in solvents and host materials. di i i l d h i l van der Waals attraction: 40 KBT/ nm • Control of diameter, chirality and length. • Determination of bulk properties and structural behavior. • Effective integration into composites. • Controlled integration into electronic circuits.
Synthesis of SWNTs Synthesis of SWNTs Research Experience for Undergraduates 2007 Hata et. al., Science 306 , 1362 (2005)
Purification of SWNTs Purification of SWNTs Standard wet air burn with H 2 O 2 Standard wet air burn with H 2 O 2 Mild acid reflux Magnetic gradient fractionation Vacuum anneal Collect 20 nm Flow in nanotube 20 nm 20 nm 20 nm magnet magnet magnetically magnetically suspension suspension fractionated nanotubes 3 3.0 Purification only -3 2 2 2 5 2.5 u/mg) x 10 nsity x 10 5 1 2.0 Fractionated 0 1.5 Inten -1 M (emu 1 0 1.0 LMNT Purified LMNT puried and Fractionated HiPCO Purified -2 0.5 HiPCO Purified and Fractionated -3 0.0 -12 -8 -4 0 4 8 12 500 1000 1500 2000 H (Tesla) wavenumber (cm -1 ) Nature Materials 4 , 589 (2005)
Surfactants Surfactants Surfactant Surfactant micelle + H d Hydrophilic headgroup hili h d Hydrophobic tail water Shake + + + oil water water water water Oil droplets +
Dispersing SWNTs: Our Work Dispersing SWNTs: Our Work Sodium Dodecyl Benzene Sulfonates (NaDDBS) - Na + C 12 H 25 SO 3 Surfactant: Surfactant: SDS SDS TX- 100 TX 100 NaDDBS N DDBS 5.00 2x10 - 2 SWNTs: 3x10 - 4 6x10 - 4 Time: 2 months 5 days 5 days 2.50 0 0 2.50 5.00 m Nano Letters 3 , 269 (2003)
Purified and Suspended SWNTs Are Undamaged Purified and Suspended SWNTs Are Undamaged Optical Properties 0.5 50 0.4 40 bance sion 0.3 30 Emiss Absorb 0.2 20 0.1 10 0.0 0 800 1200 1600 Wavelength (nm) Electrical Properties p 6 Metallic (x5) 5 t (nA) 4 3 3 Curren 2 1 Semiconducting (x10) 0 0 -10 -5 0 5 10 Gate Voltage (V) Nature Materials 4 , 589 (2005)
Aerogels Aerogels: Ultra : Ultra- - light light M Mesoporous esoporous M Materials aterials Ultra- light Highly porous materials Very high strength- to- weight Very high strength to weight Very high surface- area- to- volume ratio Ultra- light structural media Radiation detector Thermal insulator Battery electrode Supercapacitor Supercapacitor Density ( g/ cm 3 ) Aerogel type Electrical Therm al Conductivity Conductivity ( S/ cm ) Conductivity ( S/ cm ) ( W / m -K) ( W / m K) Silica N/ A ~ 0.003 0.0019 ~ 0.1
Rigidity Percolation Rigidity Percolation Network formation Strong network Strong network at low 10 5 a) s, G' (Pa 10 4 10 3 Modulus 10 2 ateau M 10 1 10 0 Pl 10 -1 10 -3 10 -2 10 -1 Phys. Rev. Lett. 93 , 168102 (2004)
CNT CNT Aerogels Aerogels Increasing CNT concentration Phys. Rev. Lett. 93 , 168102 (2004) NanoLetters 6 , 313 (2006) CNT gels do not break apart
CNT CNT Aerogels Aerogels Density: 0.02 g/cm 3 Advanced Materials 19 , 661 (2007) 1 µm
SWNT Aerogels SWNT Aerogels 100g weight on 3 aerogel posts Total aerogel mass: 12.8 mg 12.8 mg Density 0.02 g/ cm 3 10 µm 100g 100g 100g 100g Supports at least ~8,000x own weight own weight 20 nm SWNT Aerogel posts g p Electrical Conductivity up to ~10 S/ cm Surface area 1860 m 2 / g Thermal Conductivity ~0.3 W/ m- K Advanced Materials 19 , 661 (2007) 3 µm
CNT Aerogels CNT Aerogels Current (mA) 1500 750 0 -0.8 0 8 -0.4 0 4 0 0 0.4 0 4 0.8 0 8 Voltage (V) -750 -1500
Backfilling with Backfilling with epoxy epoxy Epon 828 Resin + EpiKure 3234 Crosslinker Vacuum Aerogel Resin “wicks” into sample Vacuum removed Epoxy + cross linker • Conductivity largely C d i i l l unaffected by backfilling • Improved composite conductivity Adv. Mater. 17, 1186, 2005 • Can be backfilled with Fracture - Complete fill various substances
Fusing CNT Aerogel Fusing CNT Aerogel PRL 89 , 075505 (2002)
Fusing CNT Aerogel Fusing CNT Aerogel Nature Nanotech. 3 , 17 (2008)
Fusing CNT Aerogel Fusing CNT Aerogel Irradiation gives rise to covalent bonds between the tubes. The overall strength of the nanotube materials may increase. Th ll t th f th t b t i l i Increase the tensile strength of macroscopic nanotube products. A beneficial effect on the electronic properties A beneficial effect on the electronic properties Irradiation with moderate doses may increase the conductivity of nanotube networks. Spatially localized irradiation can be used for creating functional Spatially localized irradiation can be used for creating functional electronic nanotube- based devices. Is it possible to fuse CNTs in 3D structure?
CNT Aerogel Fused CNT Aerogel Fused
CNT Aerogel Fused CNT Aerogel Fused
A fused CNT junction Defects on CNTs CNT Aerogel Fused CNT Aerogel Fused
Fused Fused CNT Aerogel CNT Aerogel HP Outside_hole holder_400V_annealing Outside_carbontape_200V_annealing 8 7 6 5 4 3 2 2 1 2 ) J (A/cm 0 -1 -2 -3 -4 -5 -6 -7 7 -8 -5 -4 -3 -2 -1 0 1 2 3 4 5 Voltage (V)
Conclusions Conclusions • We W f b i fabricated t d self- assembled lf bl d carbon b nanotube t b b based d ultra- light, lt li ht l large surface area- to- volume ratio electrically conducting porous structure – CNT aerogel. • CNTs can be fused at junction points to increase mechanical strength and CNTs can be fused at junction points to increase mechanical strength and thermal properties. 100g 100g
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