List of Figures

Figure 1.1 Carbon orbitals, hybridization. 2
Figure 1.2 image100image image110image direction cuts across graphene plane to form zigzag and armchair faces. See also Fig. 1.3. The exposed electrons and sites are in red (dark grey in print versions). 4
Figure 1.3 Edges sites zigzag and armchair. 5
Figure 1.4 Different atomic spacing along the armchair (A) and zigzag (B) edges results in distinctly different electron density distributions, with armchair edge atoms forming shorter and stronger triple bonds. This distinction between the two types of atoms is preserved in a mixed chiral edge (C), as the computed electron density illustrates (from blue (dark grey in print versions) for zero up to red (light grey in print versions) for the highest value). Schematics of the edge (D) along the (n–m) direction assists the atom counting: 2m A-atoms (count along the red (dark grey in print versions) line at 30°), and (n-m) Z-atoms (count along the horizontal black line segment). Dividing these numbers by the length (n2+nm+m2)1/2 of the edge (the diagonal on the left) yields the necessary densities, cA and cz in this example of the (8,3) edge. So there are 6 A and 5 Z atoms. 6
Figure 1.5 (A) The disoriented edge of graphite. The edge consists of a series of kinks. (B) The view of a small graphite flake, which shows that no continuum edge geometry is possible at the nanoscale, and a circular flake accepts a polygonal shape. (C) Dangling bond density, ν, of the graphene edge versus chirality angle, ω. The surface energy of the graphene fragment is a periodic function of ω because of ν(ω). Horizontal lines represent the linear approximations at the extremum points: A, armchair edge; Z, zigzag edge. 11
Figure 2.1 Stacking configuration of graphene planes. (A) AAA—rare—noticed, (B) ABA—85% of graphite, and (C) rhombohedral 15%. 14
Figure 2.2 Bond configuration when new carbon in the new bond is located above the center of two planar bonded carbons. 15
Figure 2.3 Bond configuration when new carbon in the new bond is located directly above another carbon. 15
Figure 2.4 No bonds when new carbon in the new bond is located above the center of the hexagon. 15
Figure 2.5 (A) Carboxylic acid, (B) keto, (C) ether, (D) anhydride, (E) quinone, (F) phenolic, (G) hydroquinone, or (H) lactone. 17
Figure 2.6 The oxidation of PAHs by hydrogen peroxide. PAHs, polyaromatic hydrocarbons. 20
Figure 2.7 Chiral structure of nanotubes: by rolling a graphene sheet in different directions, typical nanotubes can be obtained: (A) zigzag, (B) armchair, and (C) chiral. 28
Figure 2.8 Graphical depiction of graphite oxidation and GN oxidation. (A) Graphite oxidation by the Hummer’s method to EG. (B) GN oxidation by mild acids. Platelet type GN do not get attacked on the basal planes. EG, expanded graphite; GN, graphitic nanofiber. 36
Figure 2.9 Types of GN—orientation of graphene planes. GN, graphitic nanofiber. 38
Figure 2.10 MD simulation of GN edges zipping. MD, molecular dynamics; GN, graphitic nanofiber. 39
Figure 2.11 GN “zipping.” GN, graphitic nanofiber. 40
Figure 3.1 (A and B) Single and multiple fiber growth from catalyst particles. 45
Figure 3.2 Conversion rates and time online with different reaction temperatures. 47
Figure 3.3 SEM and TEM images of GNs: (A and B) platelet, (C and D) Herringbone, (E and F) tubular. SEM, scanning electron microscope; TEM, transmission electron microscope; GNs, graphitic nanofibers. 50
Figure 3.4 Rod-type unit as a constructive unit of platelet GNs: STM pictures of platelet GNs as-prepared (A and B), a schematic model of rod-type unit stacking (C), STM pictures of heat-treated GNs (D and E), HR-TEM picture of heat-treated GNs (F) and platelet GNs as-prepared (G), and HR-TEM picture of separated rod-type unit (H). HR-TEM, high-resolution transmission electron microscope; STM, scanning tunneling microscope; GNs, graphitic nanofibers. 51
Figure 3.5 Plate-type unit as a constructive unit of platelet GNs: a schematic model of plate-type unit stacking (A), STM pictures of platelet GNs as-prepared (B and C), and graphitized platelet GNs (D–I). STM, scanning tunneling microscope; GNs, graphitic nanofibers. 51
Figure 3.6 Growth rates versus time and temperature. Length of VANT (vertically aligned nanotubes) as derived from the experimental Fabry–Perot fringes for two sets of the growth temperatures: (A) 575–700°C and (B) 700–850°C. The dotted horizontal lines show the maximum achievable length of VANT restricted due to the termination of the growth: 1.6 μm at 575°C, growth time 518 s; 9.0 μm at 600°C, growth time 518 s; and 2.6 μm at 850°C, growth time 400 s. (C and D) Growth rates of VANT for the two sets of the growth temperatures calculated as a derivative from the curves shown in (A) and (B). GN, graphitic nanofiber. 57
Figure 4.1 Process flow from LFG to GN. Pilot project by author’s team at a San Diego County Landfill. 62
Figure 4.2 Conceptual process flow for manufacturing GN from syngas generated by waste biomass gasification. 63
Figure 4.3 Energy (A) and force (B) and potential curves as a dimensionless distance parameter. 71
Figure 4.4 A typical fluidized bed reactor with external solids separator. 72
Figure 4.5 Recirculating type FBRs. FBR, fluidized bed reactor. 73
Figure 4.6 Rotating chamber FBCVD. FBCVD, fluidized bed chemical vapor deposition. 74
Figure 4.7 Static chamber rotating bed reactor. 75
Figure 4.8 Gravity flow reactor—1 kg/day GN. 77
Figure 4.9 Conceptual fractal distributor: pressure drop across a=b=c=d, resulting in uniform flow rates. The gas is fed from the top of the feed pipe (also known as the “hub”) and flows through the nozzles at uniform flow rates. Depending on the kind of flow regime required by the process, all lengths of a,b,c,d may be equal or different in size. In some processes multiple assemblies can be used to provide uniform physical as well as chemical environments. 78
Figure 5.1 Oxidation of graphite particles with uneven lateral plane dimensions by the Hummers’ method. The product has higher d spacing and is also called expanded graphite. 84
Figure 5.2 Platelet-type GNs are oxidized with mild acid. Unlike graphite, GN oxidize with no increase in d spacing. Only edges are functionalized, only glyphCOOH & glyphOH groups found, do not get attacked on the basal plane. 85
Figure 5.3 Phase diagram for ScCO2. 90
Figure 6.1 Ziegler–Natta in situ polymerization of polyethylene. (A) Functionalizing with MAO. (B) Catalyzed in situ polymerization with GN embedded in the polymer matrix. GN, graphitic nanofiber; MAO, methyl aluminoxane. 111
Figure 6.2 Ziegler–Natta in situ polymerization of polypropylene. NOTE: GN is used in the illustration as a substitute for Graphite used in the referenced work. 111
Figure 6.3 In situ polymerization of styrene. 112
Figure 6.4 In situ polycondensation of MDI and PTMG for polyurethane in the presence of graphite sheets. (A) Embed isocyanate onto graphene platelets. (B) Polymerization. MDI, 4,40-Diphenylmethane diisocyanate; PTMG, poly(tetramethyleneglycol). 113
Figure 6.5 PVC enhancement in situ. 117
Figure 6.6 Condensation reaction in situ for nylon. 118
Figure 7.1 Poly(N-vinyl pyrrolidone). 123
Figure 7.2 (A) Polyacrylic acid and (B) poly vinyl alcohol. 123
Figure 7.3 CglyphO. 123
Figure 7.4 Hydrogen bonding. (A) Ribbon GN for improvement of electrical properties. (B) Platelet GN for strength improvement. GN, graphitic nanofiber. 128
Figure 7.5 Hydrogen bonding with polyamides. (A) Carboxylic with Nylon 6,6 and (B) Hydroxyl with Nylon 6,6. 132
Figure 7.6 (A) PLA through carboxylic and (B) PLA through hydroxyl. PLA, polylactic acid. 134
Figure 7.7 Disordered graphite edges with SEI deposits. SEI, solid electrolyte interface. 138
Figure 7.8 (A) Schematic showing the suggested mechanism of GPC growth around a carbon nanotube core; (B) SEM micrograph of pyramidal surfaces of two GPCs and (C) TEM micrographs of a GPC tip showing arches formed by folding graphene sheets. 139
Figure 7.9 Structural difference between Activated Carbon and Platelet GN. (A) Activated carbon—(typically these are not perfect spheres). Catalyst particles deposit on surface and within pores as globules. (B) Platelet GN—catalyst particles deposit on edges, as flat surfaces. GN, graphitic nanofiber. 144
Figure 7.10 (A) Incumbent Industrial Process for EB to Styrene. (B) ODH process for EB to Styrene. 163
Figure 7.11 Double-layered hydrogel FO membrane composite. 172
Figure 7.12 Pervaporation membrane system and passive solar distiller. GN enhanced membranes would increase flux rates. GN, graphitic nanofiber. 176
Figure 7.13 Capacitive Deionization. (A) Service cycle. Ions in aqueous stream are attracted to the GN electrode through an ion selective membrane for the respective electrodes, resulting in desalting of the stream. (B) Regeneration cycle. When potential is reversed or grounded, ions are forced away from electrodes and exit as a concentrated stream, resulting in ion free electrodes. 183
   
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