Nanocarbon

1. Nanocarbon NANO54 Foothill College

2. Carbon Engineering Current trends in fullerene chemistry and nanochemistry

3. Allotropy and Allotropes of Carbon (family) http://chemistry.tutorvista.com/inorganic-chemistry/allotropes-of-carbon.html

4. Allotropes of Carbon There are several allotropes of carbon of which the best known are graphite, diamond, and amorphous carbon.[12] The physical properties of carbon vary widely with the allotropic form. For example, diamond is highly transparent, while graphite is opaque and black. Diamond is among the hardest materials known, while graphite is soft enough to form a streak on paper. Diamond has a very low electrical conductivity, while graphite is a very good conductor. Under normal conditions, diamond has the highest thermal conductivity of all known materials. More recent discoveries of carbon allotropes include fullerenes (buckyballs), carbon nanotubes (single and mutliwalled) and carbon nanospheres, also known as ‘nano-onion’ (graphitic) carbon. http://en.wikipedia.org/wiki/Carbon

5. Nanocarbon Structures • Diamond • Fullerenes • Carbon nanotubes (CNT) multiwalled (MNT) • Diamond Like Carbon (DLC) • Graphene • Nanospheres

6. Nanotube Geometry The (n,m) nanotube naming scheme can be thought of as a vector (Ch) in an infinite graphene sheet that describes how to "roll up" the graphene sheet to make the nanotube. T denotes the tube axis, and a1 and a2 are the unit vectors of graphene in real space

7. Armchair Nanocarbon A SWNT can be rolled by a sheet of graphite, for example the armchair type SWNT

8. Graphene Nanostructure Extended sp2 hybridized carbon and p-p* network

9. Graphene as a System

10. Graphene as a Network Lattice constants m and n Delocalized pi e- bonding network pi-stacking interactions from a ‘structure’ to a ‘system’

11. Networked Carbon Nanostructures From the network architecture, add interactions, observe emergent properties

12. Phase Diagram of Deposited Carbon Material http://drajput.com/notes/carbon_materials/images/carbon-ternary-phase-diagram.jpg

13. Properties => Uses • Diamond => hard, thermal conductivity • Graphite => soft, clean industrial lubricant • Graphene => electrically conductive thin film • Fullerenes => conductive filler, biomedical, ultrasensitive dispersed sensor, catalysts • Nanotubes => stiffness, strength / weight, electrical conductivity, composite filler

14. Nanocarbon Applications • Nanolithography (decrease feature size; improve environmental impact) • High density data storage • In situ synthesis of electrical connects • Improve efficiency of internal combustion engines (laser spark plugs) • Ultra-high resolution displays (feature size) • Photo acoustic imaging • Cancer therapy (safe, biocompatible target for photo thermal ablation) • Explosion initiation (lower energy requirement and increase safety and portability – extension of use as a catalyst in combustion efficiency) • Hydrogen storage and release at room temperature • Low-energy, catalyst-free carbon nanotube synthesis at room temperature • Ultra-high sensitivity oxygen sensors • Carbon overcoat on rigid magnetic disks (tribology)

15. Fabrication Techniques • Diamond • Graphite • Graphene • Fullerenes • Nanotubes • Heat and pressure • CVD (with seed crystal) • High temperature conversion of diamond • CVD / plasma deposition (C2H2 plasma arc) • Gas phase reactions, electrical arc carbon rods • Plasma / CVD (CH4/H2) Partial list of fabrication techniques for various types of carbon nanostructures

16. Carbon Nanospheres • Relatively newer form of carbon • Formed by CVD, thermal decomposition • Thought to have a fullerene core – then wrapped with smaller sp2 graphene motifs • Motifs ‘converge’ upon heat treatment • Can grow from 100 to 1,000 Angstroms • Actually a ‘natural’ form of carbon (soot) • But need heat treatment to become dense

19. TEM Images of Nanocarbon

20. Carbon Nanosphere Characterization • Nanocarbon (grey powder) • SEM – overall microstructure • TEM – detailed nanostructure • XPS – C/O ratio and degree of graphitization (pi-pi* shake-up) • Raman spectroscopy – detailed structural bonding (G/D ratio)

22. Raman Overlay Spectra

23. Researchers Apply NanodiamondNanoreinforced Polymer Composite Coatings by High-Velocity Oxy-Fuel Combustion Spraying Onion-like carbon (OLC) was fabricated by annealing nanodiamond at 1000 °C for 2 hours in low vacuum (1 Pa). The OLC was characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and differential scanning calorimetry (DSC). The experimental results show that the OLC exhibits similarity to the original nanodiamond particles in shape. The size of the OLC is found to be approximately 5 nm. The transformation mechanism of the OLC from nanodiamond was discussed also.

25. Nanocarbon Structures Nanocarbon structures include common allotropes of carbon from sp2 and sp3 bonding. Graphite, graphene, fullerenes, carbon nanotubes (single and multiwall) and more recently nanospheres. The novel structure described in this work comprises a mixture of sp3 and sp2 hybridized carbon, thought to be a nucleus (seed) of sp3 diamond wrapped with fullerene structures (corannulene) also described as ‘graphitic flakes’ thought to be the building blocks of nanospheres. There are multiple routes to nanocarbon synthesis, including carbon furnaces, Chemical Vapor Deposition (CVD), and thermal decomposition . In each of these processes, intermediate carbon structures interact, fuse, etc. to form more complex nanostructures. http://nanopatentsandinnovations.blogspot.com/2009/12/drexel-researchers-apply-nanodiamond.html

26. Combustion Synthesis of Fullerenes (nano-onion) Combustion synthesis of fullerenes and fullerenic nanostructures. Courtesy Vander Sande Lab. MIT Open Courseware - http://ocw.mit.edu/courses/materials-science-and-engineering/

27. COMBUSTION SYNTHESIS OF FULLERENES AND FULLERENIC NANOSTRUCTURES Fullerenes were discovered by Kroto et al. in 1985 as products of the evaporation of carbon into an inert gas [1]. They consist of closed spherical shells comprised only of carbon atoms. This special structure results in unusual physical and chemical properties with a large potential for applications such as superconductors, sensors, catalyst, optical and electronic devices, polymers, and biological and medical applications. Fullerenes can also be formed in low-pressure fuel-rich flames of certain hydrocarbons [2,3,4], the highest yields being obtained under conditions of substantial soot formation. Other interesting classes of fullerenic or curved-layer carbon that can also be found in fullerene producing systems are nanostructures having tubular, spheroidal, or other shapes and consisting of onion-like or nested closed shells [5,6,7,8] and soot particles having considerable curved-layer content [9,10,11]. More information on the formation of fullerenic carbon in flames under different conditions is needed to understand the formation mechanisms and kinetics and to enable the design of practical systems for large-scale production.

29. Carbon Nanotube Synthesis • Laser Ablation: Nanotubes produced by pulsed YAG laser ablation of graphite target in a furnace at 1200 °C. (R. Smalley, 1996) • Chemical Vapor Deposition (CVD): Nanotubes are grown from nucleation sites of a catalyst in carbon based gas environments (Ethylene, Methane, etc.) at elevated temperatures (600 - 1000 °C). • Control Parameters for CVD nanotube synthesis: catalyst material, gas, temperature, flow-rate, synthesis time.

30. Electric Arc Discharge • Ebbesen and Ajayan 1992 • Arc discharge involving various types of plasmas and electrodes are known to produce a range of carbonaceous structures as the vaporized carbon is condensed. The condensed state can be described as a carbonaceous web, which generally radiates from the cathode, and a solid deposit on the cathode surface. Amorphous carbon, fullerenes, single- or multi-walled carbon nanotubes are among the structures present in these condensed areas. Polymorphs of carbon contained in the web and cathode deposits are variable in terms of the arc discharge operating conditions which include pressure and composition of the gas, arc voltage, and catalyst particles. In this study, we explore the effects an accompanying magnetic and/or electrical bias has on the form of deposited carbon by analyzing the condensed states as a function of the operating characteristics. A primary goal is increasing the yield of single-walled carbon nanotubes formed.

31. Continuous carbon nanotube production in underwater AC electric arc A simple, low cost and continuous growth method for the production of well graphitized multi-wall carbon nanotubes, combines the underwater growth with the use of an AC power supply and computer control. An AC electric arc is generated between two identical carbon rods of 6 mm in diameter, submerged in deionized water. Two computer controlled stepper motors are used to regulate the distance between the electrodes. At a voltage of 40 V the arc is stable in the range of 85–45 A. At lower current values a higher fraction of carbon nanotubes is obtained in the product. There is no product on the electrodes, the deposit peels off the actual cathode into the water in the next half cycle when the role of the electrodes is reversed. No vacuum is needed, a continuous flow of water makes easy the removal of the product from the system. This makes our method suitable for up-scaling. http://www.nanotechnology.hu/results/arc.html

32. Laser Ablation Laser ablation of graphite doped with 1-2% metal ions such as nickel and cobalt produces loose nanotube material called single walled nanotubes (SWNTs) and single walled nanohorns (SWNHs). These short pulse duration lasers, however, produced only a few tens of watts and a rather low vaporization rate of about 0.2g/hour. http://www.gsiglasers.com/MarketSectors.aspx?page=56

33. Early work in KrF excimer laser ablation The plasma plume created above a graphite target irradiated by a KrF laser beam (248 nm) has been investigated using three experimental methods: ion detection, time and spatially resolved emission spectroscopy and double Langmuir probe. Measurements give information on the energetic distribution of ionic species, on the kinetic temperature of the gas and on the electronic density of the plasma plume. Carbon thin films have been deposited on silicon substrates: for high fluence values (above 1000 J cm−2) and low temperature (30°C), the films are harder than c-BN, their refractive index is 2.4, and XPS analysis gives spectra with a high sp3 configuration http://www.sciencedirect.com/science/article/pii/0925963594902321

35. Chemical Vapor Deposition (CVD) • Colomer et al 2000; Awasthi et al 2003 • Thermal catalytic CVD • Acetylene, hydrogen, and argon mixtures • Methane, hydrogen, and argon mixtures • Hydrocarbon ~1%, hydrogen 10 to 30% • Temperature of 500 to 900 Celsius • Transition metal catalyst (lower temps)

37. Chemical vapor deposition of novel carbon materials Nanocrystalline diamond thin films have been prepared using hot filament CVD technique with a mixture of CH4/H2/Ar as the reactant gas. We demonstrated that the ratio of H2 to Ar in the reactant gas plays an important role in control of the grain size of diamonds and the growth of the nanocrystalline diamonds. In addition, we have investigated the growth of carbon nanotubes from catalytic CVD using a hydrocarbon as the reactant gas. Furthermore, focused ion beam technique has been developed to control the growth of carbon nanotubes individually. Fig. 1. Surface morphology of diamond thin films as a function of methane concentrations. (a) 3% of CH4, (b) 4% of CH4, and (c) 5% of CH4. The corresponding Raman spectra are shown on the right panel L. Chow et al. / Thin Solid Films 368 (2000) 193-197

38. CVD Diamond Chemical vapor deposition of diamond has received a great deal of attention in the materials sciences because it allows many new applications of diamond that had previously been considered too difficult to make economical. CVD diamond growth typically occurs under low pressure (1–27 kPa; 0.145–3.926 psi; 7.5-203 Torr) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate. The gases always include a carbon source, and typically include hydrogen as well, though the amounts used vary greatly depending on the type of diamond being grown. Energy sources include hot filament, microwave power, and arc discharges, among others. http://en.wikipedia.org/wiki/Chemical_vapor_deposition_of_diamond

39. Nanocarbon Growth Mechanisms • Hydrocarbons are first broken down into smaller carbon molecular/atomic fragments • Hydrogen is lost in the process • PAH ‘motifs’ form from carbon fragments • PAH combines with other PAH ‘motifs’ • Motifs assemble into graphene patterns • Fullerenes, nanotubes, nanospheres, etc

40. Fullerene Synthesis • Acetylene or methane • Mixed with argon and hydrogen • Plasma, arc discharge • Acetylene decomposes (transition metal) • Carbon fragments combine into PAH • Corannulene is a common

41. Buckyball (Fullerene) • 60 carbon atoms • 12 pentagons surrounded by 20 hexagons (C60) • All sp2 hybridized carbon double bonds • All atoms identical • System is in full p-p* bonding resonance

44. Poly Aromatic Hydrocarbons (PAH) • Polycyclic aromatic hydrocarbons (PAHs), also known as poly-aromatic hydrocarbons or polynuclear aromatic hydrocarbons, are potent atmospheric pollutants that consist of fused aromaticrings and do not contain heteroatoms or carry substituents.[2]Naphthalene is the simplest example of a PAH. PAHs occur in oil, coal, and tar deposits, and are produced as byproducts of fuel burning (whether fossil fuel or biomass). http://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon

45. Polycyclic Aromatic Hydrocarbon (PAH) PAHs are one of the most widespread organic pollutants. In addition to their presence in fossil fuels they are also formed by incomplete combustion of carbon-containing fuels such as wood, coal, diesel, fat, tobacco, and incense.[8] Different types of combustion yield different distributions of PAHs in both relative amounts of individual PAHs and in which isomers are produced. Crystal structure of a hexa-tert-butyl derivatized hexa-peri-hexabenzo(bc,ef,hi,kl,no,qr)coronene, reported by Klaus Müllen and co-workers.[1] The tert-butyl groups make this compound soluble in common solvents such as hexane, in which the unsubstituted PAH is insoluble. Other PAH structures can include naphthalene, pyrene, and benzene additions to pyrene. http://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon

46. NASA Analysis of Soot Nanocarbon forms in a series of steps with increasing time and temperature

47. Corannulene http://en.wikipedia.org/wiki/Corannulene

48. Carbon Soot Nanostructure – PAH motifs Carbon nanostructures including nanotubes, fullerenes, and nanospheres are comprised of ‘graphitic motifs’ which combine at varied geometries to produce extended networks of sp2 carbon. PAH motifs are thought to form in combustion flames, and also during annealing of amorphous carbon (soot etc.). During high temperature annealing, PAH motifs are hypothesized to ‘fuse’ and additionally drive off hydrogen along basal planes. Conversion of amorphous carbon to PAH can be both an external and internal process.

49. HRTEM Fringe Analysis Selected samples of heat-treated carbon black

50. Characterization Tools Characterization Tools Structure being analyzed Carbon phase state Diamond Graphite Graphene Fullerenes Diamond Like Carbon (DLC) Carbon bonding (C-C / C-H), C=C, branching Atomic / lattice imaging • Raman Spectroscopy • XPS (X-ray Photoelectron Spectroscopy) • FE-SEM (Field Emission SEM) • FTIR (Fourier Transform Infrared Spectroscopy • TEM (Transmission Electron Spectroscopy)