Novel Dispersion and Self-Assembly of Carbon Nanotubes Mohammad F. Islam Department of Chemical Engineering and 100g Department of Materials Science & Engineering http://islamgroup.cheme.cmu.edu Korea-US NanoForum 2010, Seoul, Korea April 5-6, 2010 Funding Agencies NSF: CBET-0708418, DMR-0619424 and DMR-0645596 ACS-PRF Sloan Foundation DARPA Outline • IdiIntroduction to SfSoft MilMaterials • Single Wall Carbon Nanotubes (SWNTs) • Purification, Dispersions and Their Properties • Carbon Nanotube Aerogels • Conclusions Soft Materials - Introduction Introduction to Single Wall Carbon Nanotubes Diamond C60 “Buckminsterfullerene” Graphite Single wall Carbon Nanotube (SWNT) Multiwall Carbon Nanotube (MWNT) SWNTs have extraordinary anisotropic properties ~1 nm 100 nm – 10,000 nm SWNT Strength (~100x Steel) Tensile strength ~200 GPa Electrical Conductivity (~Copper) 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 • Large scale production of clean nanotubes. • HdiiildhilHomogeneous dispersion in solvents and host materials. 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 Research Experience for Undergraduates 2007 Hata et. al., Science 306, 1362 (2005) Purification of SWNTs Standard wet air burn with H2O2 Mild acid reflux Magnetic gradient fractionation Vacuum anneal Flow in nanotube Collect 20 nm suspension magnet magnetically 20 nm fractionated nanotubes 3.0 3 Purification only -3 252.5 2 5 2.0 1 Fractionated 0 1.5 sity x 10 sity /mg) x 10 nn uu LMNT Purified 101.0 -1 LMNT puried and Fractionated HiPCO Purified Inte -2 HiPCO Purified and Fractionated 0.5 M (em -3 0.0 -12 -8 -4 0 4 8 12 500 1000 1500 2000 -1 H (Tesla) wavenumber (cm ) Nature Materials 4, 589 (2005) Surfactants Surfactant + micelle Hydrophobic tail Hy drop hilic hea dgroup water + Shake oil + + water water Oil droplets + Dispersing SWNTs: Our Work Sodium Dodecyl Benzene Sulfonates (NaDDBS) - + C12H25 SO3 Na Surfactant: SDS TX-100 Na DDBS 5.00 SWNTs: 3x10-4 6x10-4 2x10-2 Time: 5 days 5 days 2 months 2.50 0 0 2.50 5.00 m Nano Letters 3, 269 (2003) Purified and Suspended SWNTs Are Undamaged Optical Properties 0.5 50 0.4 40 ion ance 0.3 30 ss bb 0.2 20 Emis Absor 0.1 10 0.0 0 800 1200 1600 Wavelength (nm) Electrical Properties 6 Metallic (x5) 5 4 t (nA) 3 2 Curren 1 Semiconducting (x10) 0 -10 -5 0 5 10 Nature Materials 4, 589 (2005) Gate Voltage (V) AerogelsAerogels:: UltraUltra--lightlight MesoporousMesoporousMaterials Materials Ultra-light Highly porous materials Very high strength-to-weight Very high surface-area-to-volume ratio Ultra-light structural media Radiation detector Thermal insulator Battery electrode Supercapacitor Aerogel type Electrical Thermal Conductivity Density (g/cm3) Conductivity (S/cm) (W/m-K) Silica N/A ~ 0.003 0.0019 ~ 0.1 Rigidity Percolation Network formation Strong network at low 105 ) aa 104 , G' (P 103 ss 102 odulu MM 101 0 ateau 10 Pl 10-1 10-3 10-2 10-1 Phys. Rev. Lett. 93, 168102 (2004) CNT Aerogels Increasing CNT concentration Phys. Rev. Lett. 93, 168102 (2004) NanoLetters 6, 313 (2006) CNT gels do not break apart CNT Aerogels Density: 0.02 g/cm3 Advanced Materials 19, 661 (2007) 1 µm SWNT Aerogels 100g weight on 3 aerogel posts Total aerogel mass: 12.8 mg Density 0.02 g/cm3 10 µm Supports at least 100g ~8,000x own weight 20 nm SWNT Aeroggpel posts Electrical Conductivity up to ~10 S/cm Surface area 1860 m2/g Thermal Conductivity ~0.3 W/m-K Advanced Materials 19, 661 (2007) 3 µm CNT Aerogels Current (mA) 1500 750 0 -080.8 -040.4 0 040.4 080.8 Voltage (V) -750 -1500 Backfilling with epoxy Epon 828 Resin +EpiKure 3234 Crosslinker Vacuum Aerogel Resin “wicks” into sample Vacuum removed Epoxy + cross linker • CdConduct iilivity large ly unaffected by backfilling • Improved composite conductivity Adv. Mater. 17, 1186, 2005 • Can be backfilled with Fracture - Complete fill various substances Fusing CNT Aerogel PRL 89, 075505 (2002) Fusing CNT Aerogel Nature Nanotech. 3, 17 (2008) Fusing CNT Aerogel Irradiation gives rise to covalent bonds between the tubes. The overa ll st rength of th e nanot ub e mat eri al s may i ncrease. Increase the tensile strength of macroscopic nanotube products. 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 electronic nanotube-based devices. Is it possible to fuse CNTs in 3D structure? Fused CNT Aerogel Fused CNT Aerogel Fused CNT Aerogel Defects on CNTs A fused CNT junction Fused CNT Aerogel HP Outside_hole holder_400V_annealing 8 Outside_carbontape_200V_annealing 7 6 5 4 3 2 ) 2 1 0 -1 J (A/cm -2 -3 -4 -5 -6 -7 -8 -5 -4 -3 -2 -1 0 1 2 3 4 5 Voltage (V) Conclusions • We fbifabrica tdted self-assemble d carbon nanotbtube bdbased ultra-lig ht, large surface area-to-volume ratio electrically conducting porous structure – CNT aerogel. • CNTs can be fused at junction points to increase mechanical strength and thermal properties. 100g.