Lect 5 graphene & MWNT


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Prof. Dr. Mohamed Khedr
Dean of Beni Swef Faculty - postgraduate studies for Advanced Sciences

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Lect 5 graphene & MWNT

  1. 1. MULTI WALLED CARBON NANOTUBES (MWCNT) & GRAPHENE NANO-SHEETS FOR DYES REMOVAL M. H. Khedr, A. A. Fargali M. Bahgat and W.M.A.EL Rouby Beni-Suif University
  2. 2. What are carbon nanotubes? • Tubes with walls made of carbon (graphite) Nanometers in diameter • Up to tens of micrometers in height • Extremely good strength and field emission properties Roll up
  3. 3. Classification of CNTs: Single-wall Carbon nanotubes (SWNTs,1993) • one graphite sheet seamlessly wrappedup to form a cylinder • typical radius 1nm, length up to mm
  4. 4. Classification of CNTs: Ropes • Ropes: bundles of SWNTs – triangular array of individual SWNTs – ten to several hundreds tubes – typically, in a rope tubes of different diameters and chiralities
  5. 5. Classification of CNTs: Multiwall nanotubes (Iijima 1991) • russian doll structure, several inner shells •typical radius of outermost shell > 10 nm (From Iijima, Nature 1991) (Copyright: A. Rochefort, Nano-CERCA, Univ. Montreal)
  6. 6. CNTs Current Applications •Technological applications – conductive and high-strength composites – energy storage and conversion devices – sensors, field emission displays – nanometer-sized molecular electronic devices • Pipe • Wires • Springs • Gears • Pumps
  7. 7. CNTs Production Methods • Arc discharge • Laser ablation • Chemical Vapor Deposition (CVD)
  8. 8. Arc–Discharge Process • High-purity graphite rods under a helium atmosphere. • T > 3000oC • 20 to 40 V at a current in the range of 50 to 100 A • Gap between the rods approximately 1 mm or less • Lots of impurities: graphite, amorphous carbon, fullerenes Arc-discharge apparatus
  9. 9. Laser Ablation Process • Temperature 1200oC • Pressure 500 Torr • Cu collector for carbon clusters • MWNT synthesized in pure graphite • SWNT synthesized when Co, Ni, Fe, Y are used • Laminar flow • Fewer side products than Arc discharge but still high temperature Laser ablation apparatus
  10. 10. Chemical Vapor Deposition (CVD) • Catalysts: Fe, Ni, Co, or alloys of the three metals • Hydrocarbons: CH4, C2H2, etc. • Temperature: First furnace 1050oC Second furnace: 750oC • Advantages: Higher production of CNTs High Purity Fewer by-Products Low Temperature
  11. 11. What is Graphene? • “Imagine a piece of paper but a million times thinner. This is how thick graphene is. • Imagine a material stronger than diamond. This is how strong graphene is [in the plane]. • Imagine a material more conducting than copper. This is how conductive graphene is. • Imagine a machine that can test the same physics that scientists test in, say, CERN, but small enough to stand on top of your table. Graphene allows this to happen. • Having such a material in hand, one can easily think of many useful things that can eventually come out. As concerns new physics, no one doubts about it already...''
  12. 12. Allotropes of Carbon Graphene And Diamond, graphite, lonsdalerite, C60, C70, carbon, amorphous carbon, carbon nanotube
  13. 13. What is Graphene? • Is a 2D structure and 1 atom thick • Hexagonal array of sp2 carbon atoms. – Sigma orbital = valence band – Pi orbital = conduction band (2) • C-C bond is 120° and ~ 0.142nm bond length • Is electrically “metallic”
  14. 14. What is Graphene? Graphene: A Honeycomb Lattice
  15. 15. Types of Graphene: • Theoretical graphene (1947 -present) • Mechanically exfoliated/cleaved graphene (1997-2004) • Epitaxially grown graphene (1986-2004) • Chemically exfoliated and intercalated graphene (c.1980-2004) • Chemical decomposition graphene (1997-still under development)
  16. 16. 1. Drawing – mechanical exfoliation of 3D graphite crystals 2. Epitaxial growth – use of the atomic structure of substrate to grow graphene 3. Silicon Carbide Reduction – heating of silicon carbide to 1100C and reduce it to form graphene 4. Other processes (5) – Hydrazine Reduction – Sodium Reduction of Ethanol – CVD (4)
  17. 17. • Transistors • Sensors • TEM • Inert Coatings • Nanoribbons and Semiconductors • Integrated circuits • Ultracapacitors • Biodevices (6)
  18. 18. 1- Preparation of Fe-Co/CaCO3 catalyst/support: 1- The support material (CaCO3) 2- Fe(NO3)3·9H2O + Co(NO3)2·6H2O + milled CaCO3 3- The produced fine powder Ball milled 10 hrs Ball milled 2 hrs dispersed in a few drops of water and mixed well to get a homogeneous paste dried in oven at 120oC for 12 hrs 4- The paste cooled and ground well to obtain a fine powder of Fe-Co/CaCO3 catalyst/support mixture
  19. 19. Influence of reaction time and temperature on Carbon yield and morphology 400 oC Balance Purification tower Kanthal wire 500 oC Alumina tube Tube furnace 600 oC 700 oC 800 oC C2H2 Kanthal basket CO C2H2 Flo CO w Mass flow controller Gas regulator C % = [W3 – (W1 – W2) / (W1 – W2)]*100 W is the initial weight of the catalyst (Fe Co ), Fig. 12.1: Schematic diagram for the -reaction system W2 is the weight loss of catalyst at operating temperature, W3 is the weight of carbon deposited and catalyst. N2
  20. 20. 2. Influence of reaction time and temperature on Carbon yield: Figure 2: Effect of growing time on the deposited carbon percent during acetylene decomposition over Fe- Co /CaCO3 catalyst/support at different temperatures (400-800 oC) M. Bahgat, M. Khedr and M. Shaaban, Materials Technology: Advanced Performance Materials, 2008, 23, 13-18. M. Bahgat, M. Khedr, M. Radwan and M. Shaaban, Mineral Processing and Extractive Metallurgy, 2007, 116, 217-220.
  21. 21. 4. CNTs Purification: purification process was achieved by using chemical oxidation method. Specific amount of the as-grown carbon nanotubes added to mixture of conc. HNO3 &H2SO4 refluxed (3:1 by volum) the reaction mixture is diluted with distilled water filtered through a filter paper (3 μm porosity) washing oil bath for 4 hrs at 120 °C cooling to room temperature drying at 100 °C.
  22. 22. As-growing CNTs Acid treated Functionalized HOOC COOH C=O O=C OH HO COOH HOOC COOH Inner pores blocked Catalyst removed Adsorption increased Functional group added For nonpolar and/ or planer chemicals: Adsorption decreased. For polar chemicals : Adsorption increased. The effect of CNT functional groups on organic molecule adsorption M. H. Khedr, A. A. Farghali and A. Abdel-Khalek, Journal of analytical and applied pyrolysis, 2007, 78, 1-6. A. A. Farghali, M. H. Khedr and A. A. Abdel Khalek, Journal of materials processing technology, 2007, 181, 81-87.
  23. 23. 6. Effect of acid treatment on MWCNTs a MWCNT Oxidized MWCNT Scheme 1: Schematic preparation of the functionalized carbon nanotubes. b Figure 6 : TEM (a) and SEM (b) image of CNTs synthesized at 600 oC and oxidized in concentrated acid for 4 hrs. Figure 8: FTIR spectra of MWCNTs synthesized at 600 oC and then oxidized in concentrated acid for 4 hrs.
  24. 24. 3. Effect of operating temperature on MWCNTs morphology: Figure 3 : TEM image of the synthesized MWCNTs at 600 oC (a) and 700 oC (b). a Walls of MWCNT with thickness about 36 nm the inner and outer diameter of the tube about 28 and 112 nm respectively b 60 nm 22 nm 15 nm Internal diameters of approximately 12–15 nm and external diameters of 55–60 nm. M. Bahgat, M. Khedr and S. Abdel-Moaty, Materials Technology: Advanced Performance Materials, 2007, 22, 139-146. M. Bahgat and M. Khedr, Materials Science and Engineering: B, 2007, 138, 251-258.
  25. 25. Graphene preparation: 1-Preparation of graphite oxide 2-Preparation graphene 10 g Natural Graphite powders Treated by 5% HCl twice temperature was held at 353 ◦C for 30 min filtered, Washed and dried at 110 ◦C for 24 h distilled water (460 mL) was added slowly to an increase in temperature to 98 ◦C distilled water (1.4 L) and 30% H2O2 solution (100 mL) were added after the reaction The mixture was stirred for 40 min “Hummers method” “Hummers method” placed (0 ◦C) concentrated H2SO4 (230 mL) The solution was Graphite filtered, washed and dried at 60 oC 24h oxide Graphene Added to distilled water and sonicated for 30 min solution temperature was not allowed to go up to 20 ◦C The solution was the mixture was filtered held atThe solution was room temperature 50 µ of and washed with 5% HCl for with treated 24 h microwave 900 W for 3 min “On and Off” KMnO4 (30 g) was added gradually with stirring and cooling The reaction product was dried hydrazine under vacuum at 50 ◦C for 24 h hydrate was added
  26. 26. Graphene characterizations SEM of graphene sheets prepared by hummer method M. Bahgat, A. Farghali, W. El Rouby and M. Khedr, Journal of analytical and applied pyrolysis, 2011, 92, 307-313. A. Farghali, M. Moussa and M. Khedr, Journal of alloys and compounds,2010, 499, 98-103.
  27. 27. Graphene characterizations SEM of graphene sheets decorated with CoFe2O4 nanoparticles M. Khedr, A. Farghali, A. Moustafa and M. Zayed, International Journal of Nanoparticles, 2009, 2, 430-442. M. Khedr, K. Abdel Halim and N. Soliman, Materials Letters, 2009, 63, 598-601.
  28. 28. Graphene characterizations TEM of graphene sheets decorated with CoFe2O4 nanoparticles M. Bahgat, A. Farghali, W. El Rouby and M. Khedr, Journal of analytical and applied pyrolysis, 2011, 92, 307-313. A. Farghali, M. Moussa and M. Khedr, Journal of alloys and compounds,2010, 499, 98-103.
  29. 29. Organic dyes Removal:
  30. 30. Organic dyes Removal: 50 ml of dye solution dye solution of increased initial concentrations (C0) from 50 to 400 mg/L. 5 ml separated 0.05 g oxidized CNTs or graphene was added equilibrium (UV-Vis) spectrophotometer (Jasco 530) temperature control box to maintain water temperature (298, 313,323K)
  31. 31. X-Ray analysis for Catalyst: X-ray diffraction pattern for Fe, Co supported on CaCO3. ( 1: CaCO3, 2: Fe2O3, 3: CoO)
  32. 32. FTIR spectra for CNTs: 871 a 3369 2916 2848 1428 b 3369 2916 2848 1146 674 596 1704 1569 FTIR spectra of (a) as grown MWNT , (b) acid treated purified MWNT. HNO3/H2SO4 MWCNT Oxidized MWCNT schematic preparation of the functionalized carbon nanotubes.
  33. 33. Electron microscope examination for CNTs TEM for nonoxidized CNTs TEM for oxidized CNTs
  34. 34. Electron microscope examination for CNTs SEM image of the oxidized CNTs synthesized at 600 oC and refluxed in concentrated acid for 4 hrs.
  35. 35. Electron microscope examination for Graphene SEM of prepared graphene
  36. 36. Adsorption studies: The amount of dye adsorbed per unit of CNT mass increased as initial dye concentration increased due to the increase in the driving force of the concentration gradient for mass transfer with the increase in initial dye concentration. Effects of dye concentration on the adsorption of methyl green dye (CNTs = 0.1 g/100 ml and T = 298 K).
  37. 37. Adsorption studies: Effects of CNTs dosage on the adsorption of methyl green dye (dye concentration = 4.36 x 10-5 M and T = 298 K).
  38. 38. Adsorption Isotherm: Adsorption isotherms of methyl green onto Graphene at different temperature. Adsorption isotherms of methyl green onto MWCNTs at different temperature.
  39. 39. Electron microscope examination for CNTs • The adsorption capacity of methyl green onto MWCNTs and Graphene nano-Sheets 298 K 313 K 323 K MWCNTs 119.05 mg/g-1 160.12 mg/g-1 181.2 mg/g-1 Graphene 203.51 mg/g-1 258.39 mg/g-1 312.80 mg/g-1