Thermally exfoliated graphite oxide

mu uuuu ui iiui imi uui iiui iuu iuu uui iuu mui uu uii mi (12) United States Patent No.: US 8,066,964 B2 (45) Date of Patent: *Nov. 29, 2011 (1o) Patent Prud'Homme et al. (54) THERMALLY EXFOLIATED GRAPHITE OXIDE (75) Inventors: Robert K. Prud'Homme, Lawrenceville, NJ (US); Ilhan A. Aksay, Princeton, NJ (US); Ahmed Abdala, Suez (EG) (73) Assignee: The Trustees of Princeton University, Princeton, NJ (US) (*) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days. This patent is subject to a terminal disclaimer. 7,659,350 B2 7,745,528 B2 7,771,824 B2 2002/0054995 Al 2004/0127621 Al 2005/0271574 Al 2006/0121279 Al 2006/0229404 Al 2007/0142547 Al 2008/0302561 Al 200 8/03 123 68 Al 2009/0053433 Al 2009/0053437 Al 2009/0054272 Al 2009/0054578 Al 2009/0054581 Al 2009/0123752 Al 2009/0123843 Al 2009/0127514 Al 2009/0233057 Al 2010/0096595 Al (21) Appl. No.: 12/791,190 (65) Mar. 3, 2011 Related U.S. Application Data (63) Continuation of application No. 12/208,682, filed on Sep. 11, 2008, which is a continuation of application No. 11/249,404, filed on Oct. 14, 2005, now Pat. No. 7,658,901. (51) Int. Cl. C01B 31104 (2006.01) (52) U.S. Cl . ..................................... 423/415.1; 423/448 (58) Field of Classification Search ............... 423/415.1, 423/448 See application file for complete search history. (56) References Cited U.S. PATENT DOCUMENTS 4,987,175 A 5,019,446 A 5,065,948 A 5,876,687 A 6,596,396 B2 6,828,015 B2 6,927,250 B2 7,071,258 B1 7,105,108 B2 7,658,901 B2 1/1991 5/1991 11/1991 3/1999 7/2003 12/2004 8/2005 7/2006 9/2006 2/2010 Bunnell, Sr. Bunnell, Sr. Bunnell, Sr. Hung Hirata et al. Hirata et al. Kaschak et al. Jang et al. Kaschak et al. Prud'Homme et al. 2006-225473 8/2006 OTHER PUBLICATIONS Prior Publication Data US 2011/0052476 Al Prud'Homme et al. Prud'Homme et al. Herrera-Alonso et al. Mazurkiewicz Drzal et al. Jang et al. Petrik Lechtenboehmer Vaidya et al. Prud'Homme et al. Prud'Homme et al. Prud'Homme et al. Prud'Homme et al. Prud'Homme et al. Prud'Homme et al. Prud'Homme et al. Prud'Homme et al. Aksay et al. Korkut et al. Aksay et al. Prud'Homme et al. FOREIGN PATENT DOCUMENTS JP Jun. 1, 2010 (22) Filed: 2/2010 6/2010 8/2010 5/2002 7/2004 12/2005 6/2006 10/2006 6/2007 12/2008 12/2008 2/2009 2/2009 2/2009 2/2009 2/2009 5/2009 5/2009 5/2009 9/2009 4/2010 U.S. Appl. No. 12/866,306, filed Aug. 5, 2010, Aksay, et al. Celzard, et al., "Modelling of Exfoliated Graphite", Progress in Materials Science (www.elsevier.com/locat/pmatsci), Jan. 1, 2004, pp. 1-87. "Graphite", http://web.archive.org/web/20050827075854/http://en . wikipedia.org/wilci/Graphite, Aug. 20, 2005, 3 pp. L Bautista, et al., "Localizaed N2 Adsorption on Graphites, Graphite Oxides and Exfoliated Graphites", Materials Chemistry and Physics, vol. 21, No. 4. 1989, pp. 335-343. P. Ramesh, et al., "Preparation and physicochemical and electrochemical characterization of exfoliated graphite oxide", Journal of Colloid and Interface Science, vol. 274, 2004, pp. 95-102. Office Action issued Jul. 26, 2011 in Indian Patent Application No. 2672/DELNP/2008. U.S. Appl. No. 12/945,043, filed Nov. 12, 2010, Pan, et al. U.S. Appl. No. 13/077,070, filed Mar. 31, 2011, Prud'Homme, et al. Primary Examiner Stuart Hendrickson (74) A ttorney, A gent, or Firm Oblon, Spivak, McClelland, Maier & Neustadt, L.L.P. (57) ABSTRACT A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 m2/g to 2600 m2/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction. 14 Claims, 22 Drawing Sheets U.S. Patent Nov. 29, 2011 Sheet 1 of 22 US 8,066,964 B2 U.S. Patent Nov. 29, 2011 Sheet 2 of 22 US 8,066,964 B2 U.S. Patent Nov. 29, 2011 US 8 ,066,964 B2 Sheet 3 of 22 S'f{ F ^A'i^.'. vm,^..uu^erov^emvmroiYmv'^TM.v+wY^ ^n^'p y x' - r 4 PIN 3 r^ f' ff x^^-8 ^3 u r .. U.S. Patent Nov. 29, 2011 US 8,066,964 B2 Sheet 4 of 22 9 W) cm w Wa 0H o A ^ b' a 0 z c H Q LL m C1 .L W }- N 8 N IL! co ^^ LL G 60 U.S. Patent Nov. 29, 2011 Sheet 5 of 22 US 8,066,964 B2 U.S. Patent Nov. 29, 2011 US 8 ,066,964 B2 Sheet 6 of 22 r^ co 43 Q^ U 200 400 600 800 1000 Exfoliation temperature (C) FIG. 6 U.S. Patent Nov. 29, 2011 US 8 ,066,964 B2 Sheet 7 of 22 0 co C7 w I o LO 0^r m N U M O N • Q O • n • e `1qisuajuj ^T.^ U.S. Patent Sheet 8 of 22 Nov. 29, 2011 US 8,066,964 B2 00 C7 N .- (wu) ILAPH w U.S. Patent Nov. 29, 2011 US 8,066,964 B2 Sheet 9 of 22 L) O e) L- w 0 0 Nr W Od 00 N 0 0 0 00O 0 0 0 0 0 0 a 0 0 OD C%l .n 'e) Azis uazul w U.S. Patent Nov. 29, 2011 Sheet 10 of 22 US 8,066,964 B2 w U.S. Patent US 8,066,964 B2 Sheet 11 of 22 Nov. 29, 2011 0 CL 0 U <( w^ o ^ N V OR -alece a .I ! c^ a^ a E C) // J 0 O ^ M N (edw) sninpoVy e6e.1oiS m C^ z d a.d^ Z d O co Ua0 ^. V I^ ^U)WIW7 - e c oOR ^ U . I ! I m m a E r^ a 0 N O T OR (O N D O 0 O }yB18M Q V' p2711BWJON -^ O O O U.S. Patent Nov. 29, 2011 Sheet 12 of 22 US 8 ,066,964 B2 m C^ N U.S. Patent Nov. 29, 2011 US 8,066,964 B2 Sheet 13 of 22 rl w 0 co It— 4 ^ r N T- U 0 2 CL p CL a ^ Q .^• .`. . o o CL 1 zCLww0 S CO W ° ^ G t iI I LO u^ ^ o \ c? C o 0 C) T- ao O CD 0 O g u81 pOZIO IB JON cy v C Q U.S. Patent Nov. 29, 2011 US 8,066,964 B2 Sheet 14 of 22 rr (4 w U.S. Patent US 8,066,964 B2 Sheet 15 of 22 Nov. 29, 2011 Q Q CL Q Z (.)0-0 IT 3:C7 W (n W {0 a a-+ s .(D CV N0 N 1 (9 cy O N v 0 w O 0 0 0 0 0 0 W/S Aj!AljonpuoO r r t-- ^-- r r U.S. Patent Nov. 29, 2011 Sheet 16 of 22 Q Ca0 €W v ^3c^w awwf- 0)t m T, IVAN sonlen pazyewJoN E ^ 5U US 8,066,964 B2 U.S. Patent Nov. 29, 2011 US 8,066,964 B2 Sheet 17 of 22 0 0 (D 0 9 ^rp_j( 0 C 0 0 c!) 0 w W-1 0 0 Li o C b Q ^i- r i r Ln r ^ L 1 0 0 ^ L. r '^ n 0 r 0 0 ^ 0 r 't 0 0 ( Od 0 0 0 w 0 r O sninpoVi aftj oj ' 0 t-- ~ r h^ V ^I U.S. Patent Nov. 29, 2011 US 8,066,964 B2 Sheet 18 of 22 LO I - co 0 CD W 0 C% -J r- 0 0 Ln Bd!E)) 0 Ln snlnpoVq aftjojS 0 f 04 V U.S. Patent H He Name= 1-02.tif Nov. 29, 2011 Sheet 19 of 22 wu = z mm Ww,, - u.icw -time aru Stage at T - 0.0 Deg Date 23 May 2004 Extractor V Target - 4.30 kV User Name - LEOUSER FIG. 19(a) FIG. 19(b) US 8,066,964 B2 U.S. Patent Sheet 20 of 22 Nov. 29, 2011 US 8,066,964 B2 0 0 ^t 0 3 O y 0 ti 4 03. O co o 0 0 0 W '" WWW N 0 0 F- L E A^ V! ^ 0 f ,q. ^ I ^- 1 0 0 Q UP, I O N U.S. Patent Nov. 29, 2011 Sheet 21 of 22 US 8,066,964 B2 0 0 0 C.? d 0 0 C. E 0 Q N +^- ILIBIG MA POZIFLUJON ,1 0 N w U.S. Patent Nov. 29, 2011 US 8,066,964 B2 Sheet 22 of 22 ED i 0 0 r- } o ^2 6 q o ILJ CD CD 0 11r W W L Ln c ;R—C**j 00 0 Ln i I 1 1 I 1 t 2 I E O u f ^ I l I I 1 1 1 1 0 ^ E I ^ 1 1 1 I ^ I iL Q 0 T- t 0 0 z Iua^j 0 r- N N I^ w US 8,066,964 B2 1 THERMALLY EXFOLIATED GRAPHITE OXIDE CROSS REFERENCE TO RELATED APPLICATIONS This application is a Continuation of, and claims priority basedupon, U.S. patent application Ser. No. 12/208,682, filed Sep. 11, 2008, which is a Continuation of U.S. patent application Ser. No. 11/249,404, filed Oct. 14, 2005, now U.S. Pat. No. 7,658,901; the entire contents of each of which are hereby incorporated by reference. This invention was made with government support under Grant No. CMS0609049 awarded by the National Science Foundation and under Grant No. NCC-1-02037 awarded by NASA Langley Research Center. The government has certain rights in the invention. BACKGROUND OF THE INVENTION 2 called "organoclays." These materials have suffered from the cost of the added interfacial modifiers and the instability of these modifiers under processing conditions. In addition, it has been difficult to homogeneously disperse these organo5 clays in polymer matrices. Carbon nanotubes have also generated significant interest as nanofillers. They have good mechanical properties and large aspect ratios, and their surfaces should be more compatible with hydrocarbon polymers than clay-based nanofillers. As a nanofiller, CNTs have several limitations, one of l0 which is their cost of production. Since they are made in a gas-phase process, the production costs are more expensive than solution-based processes operating at high density. The production of single wall carbon nanotubes (SWCNTs) requires the addition of metal catalysts that must be removed 15 to produce pure SWCNT materials, or results in the presence of heavy metal contaminants in the final materials if not removed. Graphite is a "semi-metal," and recent efforts have demonstrated that extremely thin (few layers thick) nanoplates 20 obtained from highly oriented pyrolytic graphite (HOPG) are stable, semimetallic, and have exceptional properties for metallic transistor applications. Even though graphene sheets have the same sp2 carbon honey comb structure as carbon nanotubes (CNTs), until now, 25 it has not been possible to effectively produce the highly dispersed, thin sheets needed to make graphene applications possible. 1. Field of the Invention The present invention relates to a high surface area material based on modified graphite oxide. 2. Discussion of the Background There has been considerable interest in the area of nanoparticle-filled polymer composites (NCs), in particular composites in which the nanoparticle has dimensions comparable to those of the polymer chains, has a high aspect ratio of more SUMMARY OF THE INVENTION than 100 and is uniformly dispersed in the polymer matrix. There are several filler materials that have been extensively 30 It is therefore an object of the present invention to provide studied for improvement of mechanical properties, electrical exfoliated graphite oxide. and thermal conductivity of polymer composites, for It is another object of the present invention to provide a example, fractal agglomerated nanoparticles (silica and carmethod for making exfoliated graphite oxide sheet, in parbon black), carbon nanotubes (CNTs), inorganic clays and ticular thermally exfoliated graphite separated down to indialumina silicate nanoplates. 35 vidual graphene sheets. Initial attempts at producing nanoparticle-filled polymer It is another object of the present invention to provide a composites often resulted in materials with inadequate nanomaterial based on modified graphite that is appropriate, for particle dispersion and degraded mechanical properties. example, as a nanofillerforpolymer composites, a conductive Although often impractical for industrial applications, smallfiller for composites, an electrode material for batteries and scale dispersion methods involving solvent- or monomer 40 ultracapacitors, as a filler to improve diffusion barrier propbased processing have occasionally yielded NCs with multierties of polymers, and as a hydrogen storage material. functional capabilities and improved mechanical properties. It is another object of the present invention to provide a Several problems remain that affect the development of NCs filler material that has dimensions comparable to those of with consistent properties that are viable for use in real world polymer chains, has a high aspect ratio of more than 100 and applications: (1) many of the nanoparticles used are expen- 45 can be uniformly dispersed in a polymer matrix. sive (e.g., CNTs); (2) often chemical or mechanical manipuIt is another object of the present invention to provide a lations must be performed to achieve good dispersion that are material based on modified graphite that is electrically conimpractical for large-scale commercial production; and (3) ductive and can confer electrical conductivity when formuproblems of the interfacial energy mismatch of inorganic lated with a polymer matrix. nanofillers with hydrocarbon polymer matrix phases result in 50 It is yet another object of the present invention to provide a processing and mechanical property difficulties. material based on modified graphite that has a high aspect A significant amount of work has been done with nanoratio so that it can perform as a barrier to diffusion when clays. Nanoclay-reinforced composites have shown enhanceincorporated in a polymer composite. ments in stiffness, glass transition temperature, barrier resisThis and other objects have been achieved by the present tance, and resistance to flammability in a variety of polymer 55 invention the first embodiment of which includes a modified systems. Nanoclays are also high aspect ratio nanoplates that graphite oxide material, comprising a thermally exfoliated are, like graphene, derived from inexpensive commodity graphite oxide (TEGO) with a surface area of from about 300 materials (clays) and thus appropriate for comparison with m2/g to 2600 m2/g, wherein said thermally exfoliated graphthe projected graphene polymer composites of the present ite oxide displays no signature of graphite and/or graphite invention. The in-plane modulus of clays should be similar to 60 oxide, as determined by X-ray diffraction (XRD). that of mica, which is —178 GPa, significantly lower than the In another embodiment, the present invention relates to a 1060 GPa value of graphene (value from graphite in-plane). method of making the above TEGO. Recent studies point out that the hydrophilicity of clays makes them incompatible with most polymers, which are BRIEF DESCRIPTION OF THE DRAWINGS hydrophobic. One approach is to render the clays organo- 65 philic through a variety of approaches (amino acids, organic FIG. 1 illustrates XRD patterns of graphite and graphite ammonium salts, tetra organic phosphonium). Such clays are oxide prepared by oxidation for different durations. US 8,066,964 B2 4 3 FIG. 18 shows a RT storage modulus (GPa) vs. weight % of FIG. 2 shows selected area electron diffraction (SAED) patterns of GO oxidized for 96 hours, and the structure in the TEGO/PMMA composite. diffraction rings from stack spacing in GO. FIG. 19 shows a SEM picture of (a) 1 weight % and (b) 5 FIG. 3 illustrates a solid-state 13C-NMR spectra of GO, weight % of TEGO/PMMA composites. with the sample oxidized for 96 hours. 5 FIG. 20 shows normalized tan delta with temperature FIGS. 4a and 4b illustrate XRD patterns of TEGO and GO sweep of different weight % of TEGO/PMMA composite. samples prepared by oxidation for 96 and 24 hours and rapFIG. 21 shows thermal degradation of TEGO/PMMA idly expanded at 1050° C. The incompletely oxidized GO in composite by TGA analysis. FIG. 4b produces a more pronounced peak at 20-26.5' after FIG. 22 shows real Z vs. frequency response of TEGO/ 10 PMMA composite. heat treatment. FIG. 5 shows a Selected Area Electron Diffraction (SAED) pattern of TEGO produced from fully oxidized GO (96 hours) DETAILED DESCRIPTION OF THE PREFERRED with no structure in the diffraction rings. The structure of EMBODIMENTS TEGO is found to be totally disordered commensurate with the XRD information in FIGS. 4a and b. 15 The relatively low cost of graphite as compared to CNTs FIG. 6 shows BET surface area of TEGO samples prepared make exfoliated graphite an attractive material. The use of by heating GO samples at different temperatures for 30 secgraphite nanoplatelets (GNPs) is advantageous because of the onds. chemistry of the graphene and graphene-like sheets compared to clay nanoplates. The inventors of the present invenFIG. 7 shows (A) a XRD pattern of EG and (B) a SEM 20 tion have found that exceptionally rich chemistry of carbon image of EG. FIG. 8 shows an atomic force microscope (AFM) image can be utilized for interface engineering in composites and illustrating the thin, wrinkled platelet structure. Superimalso for many other possible application areas, such as the use posed on the image is the height profile taken along the of graphene plates in nanoelectronics and sensors. Graphene indicated line scan. The average height is —2.8 mu. and graphene-like plates are hydrophobic and thus compatFIG. 9 shows the high-resolution X-ray photo electron 25 ible with a broad range of polymers and other organic materials, including proteins, and DNA. Additionally, it is possible (XPS) spectra of TEGO. FIG. 10 shows digital image of TEGO/PMMA samples at to "tune" the wettability of graphene sheets through chemical differing weight fraction loadings. coupling with functional groups. FIG. 11 shows (A) Thermal gravimetric analysis (TGA) Graphite or graphene sheets interact with each other traces showing the thermal degradation properties of different 30 through van der Waals forces to form layered or stacked nanofillers-reinforced PMMA composites and (B) Storage structures. Theoretically, graphene sheets may have a surface modulus vs. temperature of different nano fillers in PMMA. area as high as 2,600 m2/g, since they are composed of atomiFIG. 12 shows in (A) and (B) Scanning electron microcally thick layers. Graphite has anisotropic mechanical propscope (SEM) images of TEGO-PMMA fracture surface. By erties and structure. Unlike the strong sp 2 covalent bonds using a high acceleration voltage (20 W), the sub-surface 35 within each layer, the graphene layers are held together by morphology of TEGO nanoplates can be observed. The perrelatively weak van der Waals forces. Due to this anisotropy, sistent wrinkled nature of the TEGO nanoplates within the graphite has different properties in the in-plane and c-axis composite provides for better interaction with the host polydirection. mer matrix. The chemical modification of graphite to intercalate and FIG. 13 shows normalized tan delta peaks from the 40 oxidize the graphene sheets has been described in the literadynamic mechanical analysis (DMA) showing a —35° C. ture. Intercalation, a process in which guest materials are increase in Tg (even at the lowest 0.05 wt % loading) for inserted into the "gallery" of host layered materials, creates a TEGO/PMMA over those observed for SWCNT/PMMA or separation of these sheets beyond the 0.34 nm spacing of EG/PMMA nanocomposites. native graphite. Layered materials that form intercalation FIG. 14 shows a schematic of the current distribution 45 compounds include graphite, boron nitride, alkali metal through the composite sample resulting from a voltage bias oxides and silicate clays. Among these materials, graphite applied between two metal electrodes (light grey). and boron nitride are the only solid layered materials that are FIG. 15 shows electrical conductivity of TEGO/PMMA composed of atomically thin sheets of atoms and are unique in nanocomposites as a function of filler content based on transtheir ability to form "stages" in which a monolayer of guest verse AC measurements. 50 intercalant is separated by n multilayers of host to form FIG. 16 shows in (A) a summary of thermomechanical "stage-n" compounds. The intercalation process usually property improvements for 1 wt % TEGO-PMMA compared involves chemical reaction and charge transfer between the to S WCNT-PMMA and EG-PMMA composites. All property layered host material and reagent, resulting in the insertion of values are normalized to the values for neat PMMA and thus new atomic or molecular intercalant layers. Due to its amphorelative to unity on the scale above. Neat PMMA values are E 55 teric nature, graphite can react with reducing or oxidizing (Young's modulus)-2.1 GPa, Tg (glass transition temperaagents, leading to the formation of either donor or acceptor ture)=105° C., ultimate strength-70 MPa, thermal degradatype graphite intercalation compounds (GICs). For donor tion temperature=285° C. (B and C) SEM images of EGGICs, the intercalates (anions) donate electrons to the host PMMA vs. TEGO-PMMA, respectively: The size scale layers, whereas for acceptor GICs the intercalates (cations) (nanoplate thickness) and morphology (wrinkled texture) of 60 extract electrons from the host layers. The process of the the TEGO nanoplates as well as their surface chemistry lead present invention begins with, and is dependant on, the subto strong interfacial interaction with the host polymer as stantially complete intercalation of graphite to form stage n=1 illustrated by the fracture surface (C). In contrast, simple graphite oxide. expanded graphite exhibits thicker plates with poor bonding The effect of intercalation on the bond lengths of the car65 bon atoms in bounding layers also depends on whether to the polymer matrix (B). FIG. 17 shows storage modulus vs. temperature response donors or acceptors are considered. Furthermore, with alkalis of different weight % of TEGO in TEGO/PMMA composite. there is a small expansion over the pristine value of 1.420 A US 8,066,964 B2 5 that is roughly proportional to the valence and inversely proportional to the stage index and ionic radius of the metal. The intercalation process may result in deformation or rumpling of the carbon layer by the intercalant. A local buckling of the 5 carbon layers may also occur. The result of partial oxidation of graphite produces graphite oxide (GO). Many models have been proposed to describe the structure of graphite oxide. However, the precise structure of GO is still an area of active research. A process of making expanded graphite materials with an io accordion or "worm-like" structure has been proposed. These materials have many applications, including electromagnetic interference shielding, oil spill remediation, and sorption of biomedical liquids. The majority of these partially exfoliated graphite materials are made by intercalation of graphite with 15 sulfuric acid in the presence of fuming nitric acid to yield expanded graphitic material. These expanded materials are then heated to yield an increase in the c-axis direction. While these materials are sometimes referred to as "expanded graphite" or "exfoliated graphite," they are distinct from the 20 TEGO of the present invention. For these "worm-like" expanded graphite oxide materials, the individual graphite or GO sheets have been only partially separated to form the "accordion" structures. Although the heating results in an expansion in the c-axis dimension, the typical surface area of 25 such materials is in the order of 10-60 m2/g. Both the surface area below 200 m2/g and the presence of the 0002 peak of the pristine graphite corresponding to a d-spacing of 0.34 mu are indicative of the lack of complete separation or exfoliation of the graphene sheets. While the term "graphene" is used to 30 denote the individual layers of a graphite stack, and graphite oxide denotes a highly oxidized form of graphite wherein the individual graphene sheets have been oxidized, graphene will be used to denote the layered sheet structure that may be in a partially oxidized state between that of native graphene and 35 graphite oxide. The present invention relates to a material based on modified graphite that is appropriate, for example, as a nanofiller forpolymer composites, a conductive filler for composites, an electrode material for batteries and ultracapacitors, as a filler 40 to improve diffusion barrier properties of polymers, and as a hydrogen storage material. The graphite nanoplatelet (GNP) material is distinct from previous graphitic materials, which lack one or more of the attributes required for a successful nanofiller. Also, the present invention relates to a material 45 based on modified graphite that is electrically conductive and can confer electrical conductivity when formulated with a polymer matrix. The present invention further relates to a material based on modified graphite that has a high aspect ratio so that it can perform as a barrier to diffusion when 50 incorporated in a polymer composite. More specifically, the present invention relates to a novel material based on exfoliation of oxidized graphite by a novel process. The initial step of the process is the intercalation and oxidation of natural graphite to form oxidized graphite, or 55 graphite oxide (GO). The initial step causes the spacing between graphene layers to expand with loss of the native 0.34 nm spacing. During the expansion process, a peak associated with the 0.34 nm spacing as seen in XRD patterns will disappear and simultaneously a peak associated with a 0.71 60 mu spacing will appear. The best measure for substantially complete intercalation and oxidation of graphite is the disappearance of the 0.34 nm diffraction peak and its replacement with only the 0.71 peak. So far the literature has not reported such complete intercalation and oxidation of graphite. Sub- 65 stantially complete intercalation is represented, for example, in FIGS. 4 and 5. The resulting functional groups on GO, such 6 as hydroxyl, epoxy, and carboxylic groups, alone or in combination, facilitate the retention of water molecules in the galleries between the GO layers. Rapidly heating the GO (after the 0.34 mu XRD peak is completely replaced by the 0.71 nm peak) results in superheating and volatilization of the intercalants, imbibed solvent, such as water and mixture of water with water-soluble solvents, and evolution of gas, such as CO2, from chemical decomposition of oxygen-containing species in the graphite oxide. These processes, individually and collectively, generate pressures that separate or exfoliate the GO sheets. In the context of the present invention, the term "exfoliate" indicates the process of going from a layered or stacked structure to one that is substantially de-laminated, disordered, and no longer stacked. This procedure yields disordered GO sheets which appear as a fluffy, extremely low density material with a high surface area. Disordered GO shows no peak corresponding to 0.71 nm in the X-ray diffraction pattern. During rapid heating in an inert atmosphere, the GO is partially reduced and becomes electrically conductive. The rate of heating can be at least about 2000° C./min; preferably higher than 2000° C./min. The inert atmosphere is not particularly limited as long the gas or gas mixture is inert. Preferably, nitrogen, argon or mixtures thereof are used. In addition, reducing atmospheres may be used, such as carbon monoxide, methane or mixtures thereof. The TEGO can be readily dispersed in polar solvents and polymers, and can be used, for example, in composites as nanofillers, in ultracapacitors, as dispersants, and as hydrogen storage materials. The water enters through interactions with the polar oxygen functionality and the ionic intercalants. But water is not an intercalant. The water retention in the galleries between the water molecules may be 1 to 500%, preferably 1 to 300%, and most preferably 1 to 100% by weight based on the total weight of the GO. The water retention includes all values and subvalues there between, especially including 5, 10, 20, 40, 60, 80, 100, 150, 200, 250, 300, 350, 400, 450% by weight based on the total weight of the GO. The water used is preferably deionized water, preferably water having a resistivity between 100 and 0.2 MQ/cm, morepreferably between 50 to 0.2 MQ/cm, most preferably between 18 to 0.2 MQ/cm. The resistivity includes all values and subvalues there between, especially including 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1,3 1,4, 15, 16 and 17 MQ1cm. The solvent for conducting the oxidation of graphite to produce graphite oxide is not particularly limited. While the preferred medium is water, co-solvents or additives can be used to enhance wetting of the hydrophobic graphite flakes. Solvents and/or additives may be used alone or in combination. Preferred additives include alcohols such as methanol, ethanol, butanol, propanol, glycols, water soluble esters and ethers, surfactants such as non-ionic ethylene oxide, propylene oxide and copolymers thereof, alkyl surfactants such as the Tergitol family surfactants, or the Triton family of surfactants, or surfactants with ethylene oxide and propylene oxide or butylene oxide units. Examples of these include the Pluronic orTetronic series of surfactants. Cosolvents and surfactants can be used at levels from 0.0001 to 10 wt. % of the solution phase. The amount of cosolvents and surfactants includes all values and subvalues there between, especially including 0.0005, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9 and 9.5% by weight based on the solution phase. The polar functional groups on TEGO, are preferably hydroxyl, epoxy groups and carboxylic acid groups or their derivatives. These polar groups can be functionalized using molecules that are reactive toward these polar functional US 8,066,964 B2 7 8 groups. More than one type of functional groups may be exposed to temperatures greater than 3000° C. excessive degincluded. For example, alkyl amines and dialkyl amines can radation of the GO structure may occur. However, that is the be used to add hydrophobicity to the surface by reaction to temperature experienced by the GO. GO samples exfoliated epoxides, and can be used to covalently crosslink the TEGO in flame burners may involve flame temperatures in excess of surfaces. Acid chlorides can react with hydroxyls to add alkyl 5 3000° C., but short residence times in the flames or the coolgroups. Reactions of amines or hydroxyls with carboxylic ing effects of vaporization of solvents or evolved gases may keep the temperature experienced by the particle less than acids can be used to attach groups to make the surface more hydrophobic by adding alkyl groups. The surfaces can be 3000° C., even though the flame temperature is greater. made more hydrophilic by adding ethylene oxide, primary The TEGO increases the conductivity of polymeric matriand secondary amines and acid functionality using, for io ces by factors of 10^ i to 10"' over the range of filler loadings between 0.1 to 20 wt %, preferably 1.5 and 5 wt %, based on example the chemistries listed above. An important class of modification includes the grafting of species on the surface to the weight of the polymer composite or ink formulation. The increase the cohesive interactions between the filler surface amount of filler includes all values and subvalues there between, especially including 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4 and and polymer matrices. These grafting agents can include low molecular weight analogs of the polymer matrix phase, or 15 4.5 wt %. This corresponds to conductivity increases from polymers with the same composition as the matrix phase that 10-19 S/m to 10-a -10-i S/m for a 1.5 to 5 wt % loading of have reactive functionality. These might include polyethylene TEGO in PMMA. Higher conductivities above 0.01 to 1000 or polypropylene copolymers of vinyl acetate or maleic anhyS/m can be attainable in more highly filled composite or ink dride or their mixtures to induce compatibility between formulations. The basic conductivity of the individual TEGO TEGO and olefin polymers. 20 sheet is on the order of 1/2 to Vio of the conductivity of graphite Intercalants include but are not limited to inorganic acids or based on the percentage of oxygens that disrupt the pure sp2 their salts, alone or in mixtures, preferably HNO 3, H2SO4, graphitic structure. Commonly reported values for the inHC1O4, KC1O4. plane conductivity of pure graphite sheets are 2 to 5x10 5 S/m. Gases evolved during heating include water vapor from Polymers in which TEGO can be dispersed include, but are bound water between the GO layers, oxides of sulfur SO, and 25 not limited to: polyethylene, polypropylene and copolymers H2 S from intercalated sulfates not removed by washing, thereof, polyesters, nylons, polystyrenes, polycarbonates, oxides of nitrogen NO if nitrates are used as intercalants, polycaprolactones, polycaprolactams, fluorinated ethylenes, CO2, CO, and C„H_O, species from partial reduction and polyvinyl acetate and its copolymers, polyvinyl chloride, elimination of oxygenated species from the GO precursor. X, polymethylmethacrylate and acrylate copolymers, high m, n, o are numbers, preferably integers. More than one kind 30 impact polystyrene, styrenic sheet molding compounds, of gas may evolve during the heating. In one embodiment, polycaprolactones, polycaprolactams, fluorinated ethylenes, IR-spectra of the decomposition products in the vapor phase styrene acrylonitriles, polyimides, epoxys, and polyureduring exfoliation show the presence of 50 21 CO2 and water thanes. Elastomers that can be compounded with TEGO in the unwashed GO sample and only CO 2 and water in the include, but are not limited to, poly [4,4'-methylenebi s(phenyl washed sample. The SO2 arises from decomposition of the 35 isocyanate)-alt-1,4-butanediol/poly(butylene adipate)], poly intercalated sulfate ions, and the CO2 comes from decompo[4,4'-methylenebis(phenyl isocyanate)-alt-1,4-butanediol/ sition of oxygenated species on GO. Minor amounts of higher poly(butylene adipate)], poly [4,4'-methylenebis (phenyl isocarbon number evolved gaseous products may be produced. cyanate)-alt-1,4-butanediol/poly(butylene adipate)], poly[4, And if nitrate intercalants are used there may be NOx species 4'-methylenebis(phenyl isocyanate)-alt-1,4-butanediol/di poly[4,4'40 (propylene glycol)/polycaprolactone, released. The rapid heating in an inert gas atmosphere occurs as methylenebis(phenyl isocyanate)-alt-1,4-butanediol/ follows. Rapid heating of the GO precursor is required to polytetrahydrofuran, amine terminated polybutadiene such as HYCARATB2000XI73, carboxyl terminated polybutadisuccessfully produce TEGO. If the temperature increase is too slow then evolved gases can escape through the lateral ene such as HYCAR CT132000X162, polybutadiene, dicarchannels between GO sheets without building pressures great 45 boxy terminated butyl rubber, styrene/butadiene copolymers, enough to exfoliate the GO. Inadequate heating rates can polyisoprene, poly(styrene-co-butadiene), polydimethysioccur because the temperature gradient between the sample loxane, and natural latex rubber. The polymers may be use and the oven is too low, the temperature gradient is applied too alone or in combination. slowly, or too large of a sample is processed at one time so that It is possible to compound TEGO into the monomeric heat transfer resistances inside the GO bed result in slow 50 precursors of these polymers and to effect the polymerization heating of the interior of the sample bed. Temperature gradiin the presence of the TEGO nanofiller. The polymers and/or ents on the order of 2000° C./min produce TEGO materials of their precursors may be use alone or in combination. surface areas as high as 1500 m2/g. This corresponds to 30 Polar solvents into which TEGO can be dispersed include second heating times in a 1050° C. tube furnace. Heating rates water, n-methylpyrolidone (NMP), dimethyformamide of 120° C./min produced TEGO samples with only 500 m2/g. 55 (DMF), tetrahydrofuran (THF), alcohols, glycols such as ethGradients even higher will produce even greater exfoliation, ylene glycol, propylene glycol and butylene glycol, aliphatic with the limit being the theoretical maximum value of 2600 and aromatic esters, phthalates such as dibutyl phthalate, M2/g. In order to attain the maximum surface area, it may chlorinated solvents such as methylene chloride, acetic necessary to colloidally disperse TEGO in polar solvent and esters, aldehydes, glycol ethers, propionic esters. Represenmeasure the surface area by adsorption methods in solution. 60 tative solvents of the desired classes can be found at the Dow This will ensure that all the surface area is available as a result Chemical web site (http://www.dow.com/oxysolvents/prod/ of colloidal dispersion. In addition to the rate of increase of index.htm). The polar solvent may be used alone or in comheating, the final temperature must be great enough to nuclebination. Mixtures with non-polar solvents are possible. ate boiling of the water and decomposition of the GO oxides The hydroxyl groups on the TEGO surface can be initiation and intercalated ions. Thermal gravimetric studies indicate 65 sites from which polymer chains can be grown using conthat temperatures of greater than 250° C. are required for trolled free radical polymerization (RAFT, ATR, NMP, or complex vaporization of volatile components. If the GO is MADIX polymerization) schemes. Any monomer having a US 8,066,964 B2 9 10 polymerizable can be used. Preferred monomers are aromatic The preferred water content forprocesses that involve heating monomers such as styrene, methacrylates, acrylates, butaGO granular powders is between 75% and 2% water, and the dienes and their derivatives. The monomers may be used most preferred range is 20% to 5%. These powders are subalone or in mixtures. sequently heated to induce exfoliation in a furnace, flame, The present invention relates to a thermally exfoliated 5 fluidized bed, or microwave heating device. Heating may also graphite oxide (TEGO) produced by a process which comoccur in a larger tube or by a flame process one could spray in prises: (a) oxidizing and/or intercalating a graphite sample, an aqueous slurry of the GO. In the flame process the excess resulting in a graphite oxide with expanded interlayers; and (superficial) water would vaporize without causing exfolia(b) heating the graphite oxide to cause superheating and gas tion. During the evaporation of superficial water, the vaporevolution from the intercalated water and/or solvent, the io ization keeps the temperature around the boiling point of the intercalant, and the decomposition of the graphite oxide. The solvent (i.e. ca 100° C.). Once the superficial water is evaporapid increase in pressure substantially exfoliates or disorders rated, then the partially dried GO experiences the very high the GO layer stacking. temperature and exfoliates. Substantial exfoliation of TEGO is defined by the absence Other processes for heating GO to rapidly expand it to of a X-ray diffraction peak from the original graphite peak at 15 TEGO may involve injecting slurries of GO in bulk aqueous 20-26.5° (0.34 mu separation distance between the graphene solution into the heating device. These slurries may contain GO concentrations from 1-85 wt % GO based on the total sheets), as shown by comparing the XRD pattern in FIG. 4a for TEGO and the original XRD pattern for pure graphite in weight of the slurry. The amount of GO includes all values FIG. 1. There is less than 1% peak area in the range of 20 and subvalues there between, especially including 5, 10, 15, between 24 and 29° relative to the area of the broad TEGO 20 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, and 80 wt. %. The peak between 20 of 10-20°. Improper or incomplete exfoliaslurries may be directly injected into a furnace which may be tion can result in materials shown in FIG. 4b which show the a tube furnace, a fluidized bed heater, a flame burner with a presence of the graphite peak and the broad TEGO peak. This reducing zone, or a microwave chamber. The superficial material is not the material we refer to in this patent as TEGO. water or solvent is initially evaporated and subsequently the For the TEGO material described in the present invention, the 25 GO with intercalated aqueous solvent is superheated and the area under the diffraction peak between 20=12.5 and 14.5°, GO is exfoliated. which is from the original GO sheet (see FIG. 4a), is less than The TEGO produced in accordance with the present invenis less than 15% of the total area under the TEGO peak tion preferably has a surface area of from about 300 m2/g to between 20=9 and 21°. 2600 m2/g, preferably 300 m2/g to 2400 m2/g, more preferThe present invention further relates to a method for manu- 3o ably 300 to 1100 m2/g, a bulk density of from about 40 kg/m3 facturing TEGO which comprises the steps noted above. The to 0.1 kg/m3 and a C/O ratio, after high temperature expanheating in step b) may take place in a furnace at a temperature sion, in the range of from about 60/40 to 95/5, with a range of of from 300 to 2000° C., preferably, 800 to 1200° C. and most about 65/35 to 85115 particularly preferred. The maximum preferably at about 1000° C. The temperature includes all calculated surface area will be 2600 m 2/g. based on the survalues and subvalues there between, especially including 35 face area of a single graphite sheet. The surface area includes 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, all values and subvalues there between, especially including 1500, 1600, 1700, 1800, and 1900° C. The higher the tem400, 500, 600, 700, 800, 900, 100, 110, 1200, 1300, 1400, perature, the shorter the heating time. The heating time also 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, and 2500 m2/g. The bulk density includes all values and depends on the volume of the sample and on any limitations heat conduction may pose. A sample having a larger volume 40 subvalues there between, especially including 0.5, 1, 5, 10, may require a longer heating time. The heating time is pref15, 20, 25, 30, 35 kg/m3 . The C/O ratio includes all values and erably between 1 sec and 5 min. The heating time includes all subvalues there between, especially including 65/35, 70/30, 75/25, 80/20, 85115 and 90/10. High temperature expansion values and subvalues there between, especially including 5, 10, 20, 30, 40, 50, seconds, 1 min, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 occurs in the temperature range of 250° C. or more, preferably 45 at temperatures of from 250 to 3000° C. minutes. In another embodiment, step b) may take place by spraying The TEGO of the present invention displays essentially no through a flame at a temperature of about 2500° C. The transit signature of the original graphite and/or graphite oxide as time in this case is in the order of a fraction of a second to determined by XRD, and is produced by a process that about 1 second. The superheating in step b) refers to the local involves oxidation of layered graphite to produce graphite hating of the water between the sheet to a temperature of more 50 oxide, using a material selected from e.g., sulfuric acid, nitric than 100° C. acid, hydrogen peroxide, perchlorate, or hydrochloric acid as In a preferred embodiment, the process further comprises oxidizers. The oxidant is not particularly limited. Preferred the steps of removing acids and salts from the graphene oxidants include KC1O4, HNO3 +KClO3 , KMNO4+NaNO31 interlayers prior to heating the graphite oxide, as well as K2 S2O8+P2O5 +KMNO4, KMNO4+HNO3 , HNO3 . Another drying the graphite oxide to remove excess water and solvent, 55 preferred method is polarization at a graphite electrode by while leaving intercalated species, adequate water and solelectrochemical oxidation. Mixtures or combinations of these vent for exfoliation, prior to heating the graphite oxide. The oxidants may be used. The resulting thermally exfoliated salts being removed are the ionic species involved in the graphite oxide functions as a nanofiller. The TEGO material initial oxidation and intercalation. They include H', K', chlodisplays essentially no signature of the original GO stacking rate ions, nitrate ions, sulfate ions, and organic acids that may 6o as determined by XRD. The height of the X-ray peak between arise from decomposition of the graphite structure. 20-10-15' is less than 20% of the height of the peak between 20=22-30° in the original GO material when X-ray measureIn the context of the present invention, the phrase adequate water refers to the following. During heating to produce exfoments are calibrated for absolute scattering intensities. For liated TEGO the superficial water that is water on the surfaces improvement of mechanical properties, electrical and thermal of the oxidized GO sheets must be removed. This can be done 65 conductivity of polymer composites, the aspect ratio of the in a "predrying" step to reduce the water content to between nanofiller should he greater than 100, the filler should be of a 500 wt % to 0.5 wt % (weight of water to weight of dry GO). size such that its minor dimension is comparable to the US 8,066,964 B2 11 12 dimensions of the polymer chains, and the filler should be age medium, as material for supercapacitors, in flexible elecuniformly dispersed in the polymer network. trodes, as adsorbent material, as dispersant, as lubricant, in The thermally exfoliated graphite oxide (TEGO) of the coatings, particularly in coatings that require UV stability. present invention shows no visible sign of the 002 peak (either Further TEGO can be used in glass or ceramic composites, in at 0.34 mu or 0.71 mu interplane separation distance) that 5 thermoelectric composite materials, as pigments in inks, or as characterizes graphitic materials neither in the XRD nor in UV protective filler in composites. TEGO can also be used for the SAED patterns. In a preferred embodiment of the present electromagnetic shielding, and oil spill remediation. invention, there are several steps involved in the preparation TEGO nanofillers can be added to polymer matrices to of TEGO: First is the complete intercalation and oxidation of prepare polymer composites. The large aspect ratio of the graphite. This is needed so as to permit disruption of the io nano-sheets and the very high surface area interfacing with London-van der Waals forces and to allow the incorporation the polymer matrix will produce composites with enhanced of water or other volatile solvent molecules into the stack mechanical properties. Simulations (Gusev et al. Macromolstructure. The acids and salts are then removed from the ecules 34 (2001) 3081) show that fillers with aspect ratios graphene interlayers. The GO is then appropriately dried to greater than 100 increase the tensile modulus at loading levels remove excess water or solvent, while leaving adequate sol- 15 as low as 3%. Work on surface-modified clay nanosheets has vents and intercalants to effect exfoliation. The drying shown enhancement in mechanical properties. However, the method is not particularly limited. Drying may take place at dielectric mismatch between the organic carbon matrix and room temperature, at a temperature of from room temperature the clay sheet has created problems in dispersion of clays in to 100° C., or in a vacuum oven. The GO is dried until the composites. Further, the elastic modulus of graphene sheets water or other solvent content is between 1 and 500% by 20 vs. clays provides an added advantage in tuning the elastic weight, preferably, 1 to 300% by weight and most preferably properties of the composites to higher stiffness values. The 1 to 20% by weight, based on the total weight of the GO. The organic composition of TEGO and its surface functionality amount of water or other solvent includes all values and allows its incorporation into composites without extensive subvalues there between, especially including 1, 2, 3, 4, 5, 6, surface functionalization and with facile dispersion. Poly7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 19, 20, 30, 40, 50, 60, 25 mers that can be compounded with TEGO nanofillers include, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, and 450% by but are not limited to: polyethylene, polypropylene and weight. Finally, the GO is rapidly heated to cause superheatcopolymers thereof, polyesters, nylons, polystyrenes, polying of the intercalated water and the decomposition of the carbonates, polycaprolactones, polycaprolactams, fluoriintercalants. This causes the intercalated water and the internated ethylenes, polyvinyl acetate and its copolymers, polycalants to vaporize or decompose faster than they can diffuse 30 vinyl chloride, polymethylmethacrylate and acrylate out of the interlayer spaces, generating large local pressures copolymers, high impact polystyrene, styrenic sheet molding that force the graphite oxide layers apart. The result is the compounds, polycaprolactones, polycaprolactams, fluorihighly expanded TEGO structure with unique properties as a nated ethylenes, styrene acrylonitriles, polyimides, epoxys, nanofiller. and polyurethanes. Elastomers that can be compounded with The polarity of the TEGO surface can be modified to adjust 35 TEGO include, but are not limited to, poly[4,4'-methylenebis the dispersion of the TEGO in liquid or polymeric matrices. (phenyl isocyanate)-alt-1,4-butanediol/poly(butylene adiThis modification can be accomplished during processing by pate)], poly [4,4'-methylenebis (phenyl isocyanate)-alt-1,4controlled the extent of reduction during exfoliation. This is butanediol/poly(butylene adipate)], poly[4,4'-methylenebis accomplished by controlling the time and temperature history (phenyl isocyanate)-alt-1,4-butanediol/poly(butylene of the sample. After the initial exfoliation leaving the sample 4o adipate)], poly [4,4'-methylenebi s(phenyl isocyanate)-alt-1, at an elevated temperature will result in less polar function4-butanediol/di(propylene glycol)/polycaprolactone, poly[4, ality. Exfoliation in an atmosphere with gas compositions 4'-methylenebis(phenyl isocyanate)-alt-1,4-butanediol/polyfavoring reduction will enhance reduction (such as CO or tetrahydrofuran, amine terminated polybutadiene such as CH4), and gas compositions with higher oxidative power will HYCARATB2000X173, carboxyl terminatedpolybutadiene enhance polar functionality (such as mixed inert and oxygen 45 such as HYCAR CT132000X162, polybutadiene, dicarboxy gases). It is possible to alter the polarity of the TEGO surface terminated butyl rubber, styrene/butadiene copolymers, polyafter production by chemical reaction through the OH, isoprene, polystyrene-co-butadiene), polydimethysiloxane, epoxide, and carboxylate groups on the TEGO surface. and natural latex rubber. TEGO-polymer composites can be In spite of nearly 150 years of extensive research on graphapplied as building material reinforcements, wire coatings, ite intercalation and expansion, complete exfoliation of 50 automotive components (including body panels) etc. graphite down to individual graphene sheets has not been The conductivity imparted by the conductive TEGO filler achieved. Thus far, thermal or chemical expansion and exfoat low loading levels enables the preparation of conductive liation of graphite have only produced materials with surface composites. The advantage of conductivity at low loadings is areas <600 m2/g, well below the theoretical value of -2.600 that the mechanical, and especially the fracture, properties of m2/g predicted for completely delaminated graphene sheets. 55 the composite are not compromised. The amount of TEGO in The rapid thermal expansion of GO of the present invention the polymer composite is 0.1 to 90%, preferably 1 to 80%, offers a unique opportunity for very thin nanoplates to be used more preferably 5-50% by weight based on the total weight of as a nanoscale reinforcer in polymer matrices. Due to the the composite. Another preferred range is 0.1 to 5%, preferably 0.5 to 2% by weight based on the total weight of the presence of polar oxygen functional groups on the surface of what the present invention refers to as TEGO, a polymer with 60 composite. The conductive polymer composites find great polar or potentially reactive side groups reinforced with utility in the area of electrostatic spray painting of polymer parts. The low levels of conductivity imparted by the TEGO TEGO has superior properties in comparison to similarly processed nanocomposites containing single-wall carbon allow dissipation of the charge from the charged aerosol nanotubes (SWCNTs) and traditional EG. drops. Electrostatic spraying eliminates "overspray" (i.e. TEGO may be used in polymer composites, particularly in 65 spray that misses the target) and minimizes environmental conductive polymer composites, as additive in elastomeric hazards associated with aerosol sprays and solvents. The materials, in elastomer diffusion barriers, as hydrogen storconductivity of TEGO also enables applications of electrical US 8,066,964 B2 13 14 shielding, such as for computer housings. It can be used for inner tubes. However it is significantly more expensive than other elastomers. Rubbers and elastomers that are used in tire making thermal overload protective devises wherein heat or excess current flow through the conductive composites applications do not have sufficient gas diffusion barrier propcauses an expansion of the matrix and a drop in conductivity erties to function in tire applications without the butyl rubber as the TEGO sheets no longer percolate. The level of conduc- 5 lining layer. TEGO nano platelets with aspect ratios between tivity and decrease in conductivity upon heating can be tai1000 and 10,000 can provide excellent barrier properties lored to make either current-limiting devices or thermal when added to conventional rubbers and elastomers and oriswitches. Very conductive TEGO-polymer composites can be ented perpendicular to the direction of gas diffusion. Barrier used as conductive inks and for making conductive circuitry. properties of up to 1000 times greater than that of the unfilled The lines or conductive features can be patterned by applica- io rubber are possible. Elastomers that can be compounded to tion of a polymer-TEGO-solvent fluid with subsequent dryproduce materials with enhanced barrier properties include, ing. Polymers which can be employed in the production of but are not limited to, poly [4,4'-methylenebis (phenyl isocyconductive composites include, but are not limited to: polyanate)-alt-1,4-butanediol/poly(butylene adipate)], poly[4,4'ethylene, polypropylene and copolymers thereof, polyesters, methylenebis(phenyl isocyanate)-alt-1,4-butanediol/poly nylons, polystyrenes, polyvinyl acetates and its copolymers, 15 (butylene adipate)], poly[4,4'-methylenebis(phenyl polycarbonates, polyvinyl chloride, polymethylmethacrylate isocyanate)-alt-1,4-butanediol/poly(butylene adipate)], poly and acrylate copolymers, polycaprolactones, polycaprolac[4,4'-methylenebis(phenyl isocyanate)-alt-1,4-butanediol/di tams, fluorinated ethylenes, high impact polystyrene, styrenic (propylene glycol)/polycaprolactone, poly[4,4'-methylsheet molding compounds, styrene acrylonitriles, polyimenebis(phenyl isocyanate)-alt-1,4-butanediol/ ides, epoxys, and polyurethanes. Elastomers that can be com- 20 polytetrahydrofuran, amine terminated polybutadiene such pounded with TEGO include, but are not limited to, poly[4, as HYCARATB2000X173, carboxyl terminatedpolybutadi4'-methylenebis(phenyl isocyanate)-alt-1,4-butanediol/poly ene such as HYCAR CTB2000X162, butyl rubber, polybutaadipate)], poly[4,4'-methylenebis(phenyl diene, dicarboxy terminated styrene/butadiene copolymers, (butylene isocyanate)-alt-1,4-butanediol/poly(butylene adipate)], poly polyisoprene, poly(styrene-co-butadiene), polydimethysi[4,4'-methylenebis(phenyl isocyanate)-alt-1,4-butanediol/ 25 loxane, and natural latex rubber. poly(butylene adipate)], poly [4,4'-methylenebis (phenyl isoTEGO added to polymer films, packaging materials, flexcyanate)-alt-1,4-butanediol/di(propylene glycol)/ ible tubing for medical applications, suits for chemical and polycaprolactone, poly[4,4'-methylenebis(phenyl biological warfare, gloves for chemical protection and other isocyanate)-alt-1,4-butanediol/polytetrahydrofuran, amine applications required enhanced barrier properties are also terminated polybutadiene such as HYCAR AT132000X173, 3o achievable. Also, the metal liners used as gas diffusion barricarboxyl terminated polybutadiene such as HYCAR ers in glass or carbon fiber wrapped high-pressure gas storage CT132000X162, polybutadiene, butyl rubber, dicarboxy tercylinders add extra weight and reduce the cycle-life of the minated styrene/butadiene copolymers, polyisoprene, poly cylinders. TEGO filled gas diffusion barrier composites can (styrene-co-butadiene), polydimethysiloxane, and natural be used to in place of the metal liners to improve the perforlatex rubber. 35 mane of high-pressure gas storage cylinders. Currently, carbon blacks are added to elastomers to impart There is significant interest in materials for hydrogen stordesirable mechanical properties. Most importantly the carbon age. TEGO has three unique characteristics that make it black creates a modulus that increases with strain. This nonattractive as a hydrogen storage medium that will operate at linearity protects rubber from damage during large deformamore moderate pressures and temperatures than conventional tions. The TEGO filler will provide similar enhanced non- 40 materials or carbon nano tubes. (1) The ability to covalently linear strain hardening to elastomers. The interface is similar "stitch" TEGO or graphite oxide layers using divalent chains to that of carbon black, but the flexibility of the TEGO nanoallows the preparation of TEGO or graphite oxide sheets with sheet enables deformation at low strains and hardening at interlayer spacings of approximately 1-1.4 mu. This is the higher deformations. The TEGO is superior to other clay predicted spacing that maximizes hydrogen storage between nano-platelets that have been considered for these applica- 45 graphite sheets. Stitching can be accomplished, for example, tions for two reasons: (1) the carbon structure of TEGO has with alkyl diamines reacting with the surface epoxides on the better interfacial compatibility with elastomeric matrices TEGO surfaces. The interlayer spacing is determined by the than do inorganic clay sheets, and (2) the greater flexibility of alkyl chain length. (2) The Stone-Wales defects introduced to the TEGO sheet, compared to clays, decreases interfacial the graphene sheet by oxidation provide enhanced hydrogen fatigue and debonding. Polymers that can be compounded to 5o binding relative to binding to pure graphite sheets. (3) The produce elastomers with enhanced modulus and toughness polar functionality on TEGO can be used to localize metal include, but are not limited to, include, but are not limited to, clusters on the surface that act to dissociate diatomic hydropoly [4,4'-methylenebi s(phenyl isocyanate)-alt-1,4-butanedigen into molecular hydrogen and increase the rate of saturatapoly(butylene adipate)], poly[4,4'-methylenebis(phenyl isoing and emptying the TEGO nano-sheet. This phenomenon is cyanate)-alt-1,4-butanediol/poly(butylene adipate)], poly[4, 55 called "spillover" in the hydrogen storage literature. Only 4'-methylenebis(phenyl isocyanate)-alt-1,4-butanediol/poly TEGO and graphite oxide have these multiple characteristics (butylene adipate)], poly[4,4'-methylenebis(phenyl that make them effective hydrogen storage materials. isocyanate)-alt-1,4-butanediol/di(propylene glycol)/polycaSupercapacitors are playing a significantly important role prolactone, poly[4,4'-methylenebis(phenyl isocyanate)-alt-1, in hybrid energy sources. The material of choice in all com4-butanediol/polytetrahydrofuran, amine terminated polyb- bo mercial supercapacitors is high surface area carbon either as utadiene such as HYCAR ATB2000X173, carboxyl carbon aerogel or expanded graphite. TEGO provides an terminated polybutadiene such as HYCAR CT132000X162, advantage over both materials in due to its higher surface area butyl rubber, polybutadiene, dicarboxy terminated styrene/ and planar structures. butadiene copolymers, polyisoprene, polystyrene-co-butadiThe ability to make conductive TEGO dispersions and 65 pastes, as well as conductive polymer composites opens the ene), polydimethysiloxane, and natural latex rubber. Butyl rubber has excellent gas diffusion barrier properties door for applications as electrodes for batteries, sensors, and and is, therefore, used as the lining for tubeless tires and for electronic devices. The relative inertness of the TEGO gra- US 8,066,964 B2 15 16 phitic sheet, coupled with its deformability makes it an attracreaction through the surface epoxides, amines, and hydroxyls can be used to further tune or modify polarity. The materials tive candidate for electrode applications. The planar structure of TEGO makes it an attractive material to make very thin are especially effective at dispersing crude oil in water emulelectrodes for flat surface applications. sions that are being used as drilling fluids in oil and gas The high surface area of TEGO and the layered structure 5 operations, and as mobility control agents in the recovery of that is possible to achieve make it an attractive adsorbent oil from tar sands (Canadian patent Exxon Chemical material to compete with activated carbon. The gallery size 2067177). They are especially preferred for emulsification of between layers can be tailored by "stitching" (described tars and asphaltenes in applications such as paving comabove) to produce samples with interlayer spacings between pounds and sealing compounds. 7.1 nm and 15 mu. Therefore, the adsorption can be tailored to 10 Graphite is an excellent lubricant especially in high temoptimize the binding of species with specific sizes. This size perature applications due easy sliding of graphene sheets over selectivity, polar sites on the TEGO surface, the ability to each other. We expect TEGO to display superior lubricating functionalize the TEGO surface, enable the production of properties since the interactions between the graphene sheets adsorbents with unique size selectivity and chemical speciare significantly weakened in comparison to graphite. ficity. The size specificity is shown between molecules over a 15 The UV light absorption capabilities of TEGO make it an range of 1 to 50 mu, preferably 1-20 mu. The size includes all attractive additive to coatings that must maintain stability values and subvalues there between, especially including 5, exposed to sunlight. Coatings include preferably black coat10, 15, 20, 25, 30, 35, 40 and 45 mu. It is especially useful in ings. TEGO can be used as an additive for roofing sealers, the separations of proteins. caulks, elastomeric roofing membranes, and adhesives. Current absorbents and absorptive media for protein and 20 TEGO absorbs UV radiation and can therefore be used to DNA fragment separations are often based on silica or celluimpart UV protection and to improve the lifetime of plastic lose particulates in the size range of 10-1000 microns. The components in outdoor use, such as hoses, wire coatings, substrates provide mechanical support and reactive groups plastic pipe and tubing etc. that canbe used to couple ligands and functional groups to the TEGO can be added to a ceramic matrix to improve the particle surfaces. A disadvantage of the silica-based media is 25 electrical conductivity and the fracture toughness of the matethe relative instability of the particles and surface linkages at rial. The partially oxidized surface of TEGO offers stronger pH's above 8. The disadvantage of the cellulose-based supinteraction with the ceramic matrix, especially with metal ports is the relative difficulty in conjugating ligands and funcoxides and silicon oxides in particular. For example, TEGO tionality to the hydroxyls on the cellulose surfaces. can be mixed with a silicon alkoxide material and then the The TEGO material combines the advantages of high sur- 30 silicon alkoxide can be condensed to form an amorphous face area and readily functionalizable epoxide and carboxyl material silicon oxide material containing well-dispersed groups on the TEGO surfaces. In this invention the surface of TEGO nano-platelets. The hydroxyl and epoxide groups on the TEGO is made anionic by reaction of carboxylic acid the TEGO surface can condense with the silicon alkoxide to and/or sulfonic acid containing reactants with amine funcform strong covalent bonds between the matrix and the tionality. The facile reaction with the TEGO epoxides under 35 TEGO filler. Low loadings of TEGO in such materials impart mild conditions of reflux conditions in ethanol enable surface improved fracture strength and conductivity. TEGO-glass modification. To provide anionic surfaces. Reaction with and TEGO-ceramic composites can also be applied as therdiamines provides amine surface functionality that can be moelectric materials. Similar techniques can also be used to further quaternized to create permanent cationic charge. create tinted and UV-protective grades of glass. TEGO can Functionalization using reactions commonly employed to 4o also be used to reinforce cement and in other building matefunctionalize cellulose media can be used to functionalize rial applications. through the TEGO surface hydroxides. Once the surface is Due to the very low loadings of TEGO required to impart functionalized with the ion exchange moiety or an affinity tag electrical conductivity to a non-conductive matrix, TEGO can ligand, the surface can be further functionalized with PEG or form composite materials with greatly enhanced electrical dextran functional reagents to passivate the surface to make it 45 conductivities but with thermal conductivities approximately resistant to protein adsorption or denaturation. The TEGO, the same as those of the matrix materials. This combination thus functionalized can be used as a bulk filling for chromaleads to TEGO-composites with improved thermoelectric figtography columns or can be compressed or agglomerated to ures of merit. The matrix material for this application can be make a macro-particulate media in the size range 10-5000 either organic or inorganic, with excellent thermoelectric microns that can be used as a chromatography packing. 50 properties expected from the TEGO-silica composites, as The native and functionalized TEGO can also be used as an noted above. The electrical conductivity of and nature of the adsorptive media for gas phase separations. The functionalcarrier (i.e. electrons versus holes) in the material can be ized TEGO described above can be directly used as packings tailored by altering the surface chemistry of the TEGO filler for gas chromatography applications. or by modifications to the matrix material. The unique blend of hydrophilicity and hydrophobicity 55 Carbon black and other carbon materials are frequently that arise from the polar and non-polar groups on the TEGO used as a pigment in inks. The very small size of the TEGO surface and its large platelet size make it an effective dispersnano-platelets can lead to an ink with an exceptionally high ant for oil in water and water in oil emulsions. Oils include gloss (i.e. low surface roughness of the dried ink). The surface alkanes, aromatic hydrocarbons, chlorinated hydrocarbons, chemistry of TEGO can also be easily modified to produce heterocyclics, petroleum distillates ranging from light hydro- 6o different colors, tones and tints. carbons (C4-C8), to heavy vacuum residuals (C18-C40+), The conductive properties of TEGO enable its use in elecnatural oils such as corn, safflower, linseed, olive, grape seed, tromagnetic shielding. Applications such as the enclosures silicone fluids and oils, fatty acids and fatty acid esters. The for computer housings, computer screens, electronic devices polarity of the TEGO can be tuned by the exfoliation condisuch as medical diagnostics, and consumer electronics often tions. The degree of reduction during the high temperature 65 require screening so that electromagnetic signals are either treatment determines the balance of oxidized surface groups contained in the device and do not escape to provide interfer(polar) to reduced graphitic sites (nonpolar). Further, post ence for other devices, or to prevent external fields from US 8,066,964 B2 17 interfering with the electronic components inside the enclosure. Currently conductive carbon black fillers are often used in these applications or conductive expanded graphite fillers. The TEGO conductive fillers can be used in these applications at lower loading levels and with less deleterious impact on the mechanical properties of the polymer matrices. In addition to the TEGO being added to the structural polymer used in these applications, the TEGO can be incorporated into a solvent phased system with binder to make a conductive paint that can be applied to the interior of the housing to provide electromagnetic shielding. Currently expanded graphite is used as an absorbent for oil spill remediation and for the cleanup of other hazardous organic liquid spills. The hydrophobic surfaces are wetted by oil and thereby bind and hold oil. Other compounds used for spill remediation are clays, but these must be surface treated to may them hydrophobic enough to bind organic liquids. The high surface area of TEGO and its hydrocarbon surfaces make it an excellent absorbent material for oil and organic liquids. The TEGO can be contained in large porous sacks made from polypropylene or polyethylene fabric or porous film. The low bulk density of TEGO make it attractive in that the amount of liquid that can be imbibed on a weight basis can be high. Liquid loadings between 100 to 10,000 wt wt oil to TEGO can be achieved. In another embodiment the TEGO is co-processed with a polymeric binder in the form of a foam sheet. These open cell structure of the foam allow contact between the oil and the TEGO surfaces. The advantage of this system is that the absorbent system can be rolled for storage. While the present invention shows a high surface area value for the exfoliated graphene by Nz adsorption, this may not be the most relevant measure of the ability to disperse the graphene sheets, in, for example, a polymeric matrix. While adsorption measurements reflect porosity and surface area of three dimensional structures and powders, graphene comprises two-dimensional, flexible sheets. In the solid dry state the graphene sheets must be in contact, and the contact areas will occlude nitrogen intrusion in the adsorption measurement. A more appropriate analogy for graphene may be to consider it as a two-dimensional polymer. An important question for applications involving graphene in polymer matrices is the degree of dispersion, or the effective surface area, in the dispersed state. The present invention TEGO materials disperse readily in polar organic solvents such as THE to form a uniform dispersion. Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only, and are not intended to be limiting unless otherwise specified. EXAMPLES Materials and Methods: SWCNTs (BuckyPearls, lot no. CTU3-2005B-2) from Carbon Nanotechnologies, Inc. (Texas, USA); PMMA (M_-350000, PDI=2.7) from Polysciences (Warrington, Pa., USA); and organic solvents, all HPLC grade, from Fisher Scientifics (Hanover Park, Ill., USA) were used as received. Flake 1 Graphite was from Asbury Carbon Co. (Asbury, N.7., USA). Preparation of Graphite Oxide (GO): Graphite oxide was prepared from Flake 1 graphite according to the method of Staudenmaier (L. Staudenmaier, Ber. Dtsh. Chem. Gies, 31, 1481, (1898)). Graphite (1 g) was added to a 500-m1 round-bottom flask containing a stirred and cooled (0° C.) mixture of concentrated sulfuric and nitric acid 18 (2:1 v/v, 27 ml). Potassium chlorate (11 g) was then added gradually in small portions to ensure that the temperature of the reaction mixture did not rise above 30° C. After the addition of potassium chlorate, the mixture was allowed to reach 5 room temperature and stirring was continued for 96 h. Next, the mixture was poured into deionized water (11) and filtered over a 60-m1 fritted funnel (coarse). The product was washed on the funnel with 5% aqueous HCl until sulfates were no longer detected (when 5-ml of the aqueous filtrate does not 10 turn cloudy in the presence of one drop of saturated aqueous BaClz) and then with deionized water (2x50 ml). The resulting graphite oxide was dried in an oven at 100° C. for 24 h. Elemental analysis (Atlantic Microlab, Norcross, Ga.): C, 15 53.37%; O, 39.45%; H, 1.62%; N, 0.14%. Preparation of Expanded Graphite (EG): Flake 1 Graphite (1 g) was treated with 4:1 v/v mixture of concentrated sulfuric and nitric acid (50 ml) for 24 h at room temperature. Upon completion, the suspension was diluted 20 with water (150 ml) and filtered. The solid residue was washed with copious amounts of water until the filtrate was no longer acidic. The resulting material was dried in an oven at 100° C. overnight. Next, the dried material was placed in a quartz tube and the tube heated rapidly with a propane blow 25 torch (Model TX9, BernzOmatic, Medina, N.Y.) set at medium intensity while under dynamic vacuum to produce the expanded graphite (FIG. 7). Preparation of TEGO By Method A: Graphite oxide (0.2 g) was placed in an alumina boat and 30 inserted into a 25-mm ID, 1.3-m long quartz tube that was sealed at one end. The other end of the quartz tube was closed using rubber stopper. An argon (Ar) inlet and thermocouple were then inserted through the rubber stopper. The sample 35 was flushed with Ar for 10 min, then the quartz tube was quickly inserted into a Lindberg tube furnace preheated to 1050° C. and held in the furnace for 30 s. Elemental analysis of a sample oxidized for 96 h indicates a C/H/O ratio of 54/25/21 (by mol) while the elemental analysis of TEGO 40 shows an increase in C/O ratio from 6/4 in GO to 8/2. Preparation of TEGO By Method B: Graphite oxide (0.2 g) was placed in a 75-m1 quartz tube equipped with a 14/20 ground glas s j oint. The tube was evacuated and backfilled with nitrogen three times and then 45 attached to a nitrogen bubbler. Next, the GO was heated rapidly with a propane blow torch (Model TX9, BernzOmatic, Medina N.Y.) set at medium intensity until no further expansion of graphite oxide was observed (typically 15 s.). Elemental Analysis: C, 80.10%; O, 13.86%; H, 0.45%; N, 50 0%. Dispersion of TEGO in Organic Solvents: The dispersions of TEGO were made at 0.25 mg/ml concentrationby sonicatingTEGO (prepared by method B, 5 mg) in a given solvent (20 ml) for 5 h in a Fisher Scientific FS6 55 ultrasonic bath cleaner (40 watt power). The dispersions were then left standing under ambient conditions. The following was observed: TEGO dispersions in methylene chloride, dioxane, DMSO and propylene carbonate precipitated within 8 h after sonication. The dispersion in 6o nitrobenzene was more stable, but after 24 h the precipitation of TEGO was complete. In THE, a moderately stable dispersion was observed accompanied by fairly substantial precipitation after 24 h. However, the THE dispersion still remained blackish after a week. More stable dispersions can be 65 obtained in DMF, NMP, 1,2-dichlorobenzene, and nitromethane: they were still quite black after one week albeit with a small amount of sedimentation. US 8,066,964 B2 19 20 A Experimental Procedure for the AFM Imaging: C. under 2 MPa to approximately 0.12-0.15 min The AFM images were taken on an AutoProbe CP/MT neat PMMA control sample was prepared in the same manScanning Probe Microscope (MultiTask), Veeco Instruments. ner. TEGO was dispersed in 1,2-dichlorobenzene by sonication Mechanical Analysis: (vide supra) and the dispersion deposited on a freshly cleaved 5 The viscoelastic response of these composites was meamica surface. Imaging was done in non-contact mode using a sured using Dynamic Mechanical Analysis (DMA 2980, TA V-shape "Ultralever" probe B (Park Scientific Instruments, instruments, DE, USA). Strips of uniform width (6 mm) were B-doped Si with frequency f,-78.6 kHz, spring constants cut from the film using a razor blade. A tensile force with k=2.0-3.8 N/m, and nominal tip radius r=10 nm). All images 0.1-N pre-load was applied to the test specimen using a film were collected under ambient conditions at 50% relative io tension clamp and dynamic oscillatory loading at a frequency humidity and 23° C. with and a scanning raster rate of 1 Hz. of 1 Hz and amplitude of 0.02% strain was applied. Storage The AFM image in FIG. 8 shows stacks of TEGO nanostack modulus (FIG. 10) and tan delta (FIG. 13) were obtained in with thickness of –2 nm. temperature sweeps of Y C./min. The stress-strain curves and X-Ray Photoelectron Spectroscopy (XPS): ultimate strength of the composites were obtained according XPS measurements were performed using an Omicron 15 to ASTM D882 using Minimat (TA Instruments, DE, USA). ESCA Probe (Omicron Nanotechnology, Taunusstein, GerThermal Property Measurements: Thermal degradation properties of the composites were many) located at Northwestern University's Keck Interdisciplinary Surface Science Center with monochromated Al Ka examined by thermal gravimetric analysis (TGA) on a TA Instruments SDT 2960 Simultaneous DTA-TGA instrument. radiation (hv=1486.6 eV). The sample was oriented with a 45° photoelectron take-off angle from the sample surface to 20 Pieces of the composites (-10 mg) were loaded into to the TGA instrument and heated from 40° to 800° C. at a rate of the hemispherical analyzer. Data were collected using a 10° C. per minute under N2 atmosphere. Data are shown in 15-kV acceleration voltage at 20-mA power and vacuum of FIG. 11. 10' mbar. An analyzer pass-energy of 50 eV with 500-meV steps was used for single-sweep survey scans. High-resoluScanning Electron Microscopy (SEM): tion spectra were averaged over three sweeps using an ana- 25 SEM imaging was used to examine EG and TEGO morlyzer pass energy of 22 eV with 20-meV steps. TEGO phology ex situ as well the fracture surfaces of the nanocomposites using a LEO 1525 SEM (LEO Electron Microscopy samples were de-gassed overnight within the XPS chamber (10-3 mbar) prior to analysis. The raw C is XPS data (FIG. 9) Inc, Oberkochen, Germany) (FIG. 12). Nanocomposite samples were mounted on a standard specimen holder using were analyzed using multipak and XPS peak 41 fitting software to determine the relative peak locations and areas in 3o double-sided carbon conductive tape with the fracture surrelation to standard binding energies for known carbon funcfaces toward the electron beam. An acceleration voltage was tionalities (Handbook of X -ray photoelectron spectroscopy, varied between 1 kV-20 kV depending on different imaging edited by J. Chestain, R. C. King Jr., Physical Electronic, Inc., purposes and sample properties. Eden Prairie, USA (1992)). The main component at 284.6 eV Glass Transition Temperature Measurements: is attributed to C in C C bond. An additional component at 35 The glass transition temperature, Tg of each composite was 286.1 eV is attributed to C in —C-0— or C O—C moiobtained from the tan delta peaks from the DMA experiment eties. described in SI-5 (FIG. 13). DMA results (normalized tan The atomic concentration was calculated from the relation delta peak) are shown for all nanocomposites at 1 wt % (Surface analysis method in materials science, edited by D. J. loading as well as for TEGO/PMMA at two lower wt % O'Connor, B. A. Sexton, R. St. C. Smart, Springer-Verlag, 40 loadings. Results show a peak broadening but no shift in the Tg for SWNT/PMMA and a modest increase in T g for Heidelberg, (1992)): C–(I,/S,)/Ez(I,/S,), where I, is the peak intensity for element i and S is the sensitive factor for the peak EG/PMMA. TEGO/PMMA nanocomposite shows a rheoi. Sensitive factor for C, is 1 and 0, is 2.85. From peak logical percolation even at the lowest wt % measured, 0.05%, intensity integration, the oxygen concentration is calculated with a nearly-constant Tg shift of 35° C. for all wt % mea45 sured. to be 8.4 atomic %. Processing of Nanocomposites: AC Conductivity Measurements: The TEGO used for nanocomposite was prepared via both Composite samples were microwave plasma-etched methods A and B. Consistent composite properties were (Plasma-Preen II-862, Plasmatic Systems, N7) for 1 min at 2 obtained regardless of the method of TEGO preparation. Torr of O2 and 350 W of power. AC impedance measurements Depending on the wt % of the composite, each type of nano- 50 were performed using an impedance analyzer (1260 Solarfiller was initially dispersed in tetrahydrofuran (THE, 10 ml) tron, Hampshire, UK) with a 1296 Solar-ton dielectric interby bath sonication (Branson 3510, 335 W power) at room face. The specimen was sandwiched between two copper temperature. These solutions were then combined with a electrodes that are held tightly together with two 2-mm thick solution of PMMA in THE (10-30 ml). Shear mixing (Silverpolycarbonate plates. Electrically conductive colloidal son, Silverson Machines, Inc., MA. USA) at 6000 rpm was 55 graphite (Product no. 16053, Ted Pella Inc., Redding Calif., then applied to the TEGO/PMMA and EG/PMMA systems USA) was applied between the sample and copper electrode for 60 min in ice-bath to reduce the frictional heat produced in to avoid point-contacts caused through surface roughness of polymer by the shear mixer while the S WNT/PMMA systems the nano-composites. Impedance values were taken for the received additional bath sonication for 60 min (shear mixing nanocomposites between 0.01-10 6 Hz. Conductivity of the was not used for SWNT/PMMA). The composite solutions 60 polymer nanocomposites (see FIG. 15) is taken from the were then coagulated with methanol, filtered under vacuum plateau at low frequencies at 0.1 Hz. using polycarbonate filter paper (Millipore, Cat. No. DC Conductivity Measurements: TCTPO4700; 10-µm pore size), and dried at 80° C. for 10 h to Hot-pressed composite samples having thickness about 0.1 min yield a solid flaky materials. Nano-filler/PMMA composite cut into strips that are 1-2 min and 15-20 mm samples for mechanical testing were pressed into a thin film 65 long. The strips were microwave plasma-etched (Plasmabetween stainless steel plates using 0.1-mm thick spacers in a Preen II-862, Plasmatic Systems, NJ) for 1 min at 2 Torr of O2 Tetrahedron (San Diego, Calif.) hydraulic hot-press at 210° and 350 W of power. Subsequently, 25-nm thick gold films US 8,066,964 B2 21 22 were thermally deposited on the specimen surfaces: four pads Example 3 on one side of the composite strip for the longitudinal measurements and one pad on two opposing sides of the strip for XRD patterns of graphite, GO, and TEGO were recorded in a Rigaku MiniFlex diffractometer with Cu Ka radiation. Inithe transverse measurements. Pad spacing for longitudinal measurement were always 0.16 mm (determined by mask 5 tial, final and step angles were 5, 30 and 0.02, respectively. geometry during the deposition). Pad spacing for transverse The surface area of TEGO was measured by nitrogen adsorpmeasurements were preset by the sample thickness. Copper tion at 77K using a Micromeritics F1owSorb apparatus with a wires were attached to these gold-platted pads using silvermixture of Nz and He 30/70 by volume as the carrier gas. filled epoxy (H20E, EPO-TEK, MA). Four-point probe DCHigh-resolution XPS spectra were obtained using an Omiresistive measurements were performed using an HP multi- l0 cron ESCA Probe (Germany). Samples were de-gassed overmeter (HP34401A). As a first approximation, the composite night within the XPS chamber (10-3 mbar) prior to analysis electrical resistivity was calculated from known specimen of the sample. Data were collected using 15 kV and 20 mA geometry. In these initial results, longitudinal and transverse power at 10-9 mbar vacuum. The raw XPS data were anaresistivities diverged considerably, especially for EG-filled 15 lyzed to determine peak locations and areas in relation to composites. Transverse resistivities were always higher than specific binding energies that best fit the experimental data. longitudinal ones. However longitudinal measurements, conThe main C C peak (Cis) at 284.6 eV was observed. An sidering the electrical leads configuration, include both lonadditional photoemission present at higher binding energy gitudinal, h and transverse, I, components of the current path peaks at 286.1 eV represented C O or C O—Cbond(FIG. 14). In order to separate these two components, the current distribution across the specimen was modeled based 20 ing. on the finite-element method (Femlab 3. 1, Comsol AB). For Example 4 each measured sample, we input actual specimen and electrical pads geometry, transverse resistivity, and longitudinal The solid-state magic angle spinning (MAS) 13C NMR resistance to obtain the computed longitudinal resistivities 25 spectrum of the graphite oxide was obtained using a Chemagthat are reported in this paper. netics CMX-II 200 spectrometer with a carbon frequency of X-ray Diffraction (XRD) Measurement 50 MHz, a proton frequency of 200 MHz, and a zirconia rotor XRD patterns of graphite, GO, and TEGO are recorded in of 7.5 mm diameter spinning at 4000 Hz. To enable separation a Rigaku MiniFlex diffractometer with Cu Ka radiation. Initial, final and step angles were 5, 30 and 0.02° respectively. of the carbon peaks of the solid GO sample a so called, "Block 30 pulse sequence" was used. This employs a decay pulse Example 1 sequence with a 45° pulse angle of 2.25 ms, high-power proton decoupling (-50 kHz), and a 20 s delay between Graphite oxide was prepared from graphite by a process of pulses. The spectrum was run at room temperature and 5120 oxidation and intercalation, referred to as the Staudenmaier scans were acquired with 4 K data points each. The chemical method. The method uses a combination of oxidizers and 35 shifts were given in ppm from external reference of the hexintercalants: sulfuric acid, nitric acid and potassium chlorate amethylbenzene methyl peak at 17.4 ppm. under controlled temperature conditions. Ratios of graphite to potassium chlorate in the range of 1:8 to 1:20 (wt/wt) are Example 5 preferred. Ratios of sulfuric to nitric acid from 5:1 to 1:1 are preferred. The Staudenmaier method is the preferred oxida- 40 FIG. 1 shows the XRD diffraction patterns of the graphite tion procedure. flakes after oxidation for 48, 96, 120 and 240 hours. Note that In this example, 5 g graphite flake with a 400 µm average as oxidation proceeds, a new peak characteristic of GO flake size (Asbury Carbon, Asbury, N.7.) was added to an appears at a d-spacing of about 0.7 mu (20=12.2°), and the ice-cooled solution containing 85 ml sulfuric acid and 45 ml intensity of the native graphite 002 peak (20=26.7°) nitric acid. This was followed by the addition of 55 g potas- 45 decreases significantly. Note also that after oxidation for 96 sium chlorate over 20 minutes such that the temperature did hours or longer, the graphite 002 peak essentially disappears. not exceed 20° C. After this oxidation/intercalation process At this point, intercalation is achieved, as the graphene layers are no longer about 0.34 nm apart (as they were initially), but proceeded for 96 hours, the reaction mixture was poured into 7 1 of deionized water and filtered using an aspirator. The are now about 0.71 mu apart. The graphite oxide samples oxidized graphite was then washed with 5% HCl until no 50 having d spacings of about 0.71 mu correspond to about 12% sulfate ions were detected in the filtrate, using the barium adsorbed water. chloride test. The oxidized graphite was then washed with DI Example 6 water until the filtrate had a pH of 5 or greater. The sample was examined by XRD to demonstrate complete oxidation by the elimination of the original sharp diffraction peak of graphite. 55 The selected area electron diffraction (SAED) pattern of the oxidized, but not exfoliated, sample is shown in FIG. 2. SAED patterns are observed by focusing beam at a selected Example 2 area to obtain electron diffraction information on the structure In preparing thermally exfoliated graphite oxide (TEGO), of matter. The SAED was taken over a large area; therefore, it graphite oxide (0.2 g) was placed in a ceramic boat and 60 contains the information from many GO grains. A typical inserted into a 25 mm ID, 1.3 m long quartz tube that was sharp, polycrystalline ring pattern is obtained. The first ring 21 originates from the (1100) plane, with the second ring 22 sealed at one end. The other end of the quartz tube was closed using a rubber stopper. An argon (Ar) inlet and thermocouple arising from the (1120) plane. In addition, strong diffraction were then inserted through the rubber stopper. The sample spots were observed on the ring. The bright spots correspondwas flushed withAr for 10 minutes; the quartz tube was then 65 ing to the (1100) reflections within the ring retain the hexagoquickly inserted into a preheated Lindberg tube furnace and nal symmetry of the [0001] diffraction pattern. It is therefore heated for 30 seconds. postulated that the GO sheets, before thermal treatment, are US 8,066,964 B2 24 23 not randomly oriented with respect to one another, and the interlayered coherence is not destroyed at this stage. Example 7 It is further postulated that GO contains aromatic regions composed entirely of sp 2 carbon bonds and aliphatic spa regions that contain hydroxyl, epoxy, and carboxylic groups. Elemental analysis of a sample oxidized for 96 hours indicates a C/H/O ratio of 54/25/21 (by mol). The 13C-NMR spectrum for a sample oxidized for 96 hours is shown in FIG. 3. The spectrum contains three distinguishable peaks, at chemical shifts (6) of about 60-70, 133, and 210-220 ppm. The peak between 60 and 70 ppm is anticipated to be composed of two peaks, which can be assigned to hydroxyl and epoxy groups. The peak at 133 ppm corresponds to aromatic carbons, while the third peak at 210-220 ppm may be assigned to carbon attached to carbonyl oxygen. Example 8 In an exemplary embodiment, in order to form TEGO, a graphite oxide sample that has been oxidized for 96 hours is heated under argon for 30 seconds at different temperatures. It was found that heating the expanded GO at 200° C. is sufficient for partial exfoliation. However, the extent of exfoliation increases as the temperature increases. The exfoliation results in a large apparent volume expansion (about 200-400 times the original volume). The TEGO prepared from completely oxidized samples has a fluffy "black ice-like" structure. FIGS. 4a and 4b show the XRD spectrum of graphite, GO oxidized for 96 hours, and a TEGO sample prepared by rapid heating of the GO sample. TEGO samples show no sign of the 002 peak for either the graphite oxide (20=12.2°) or for the pristine graphite (20=26.5°). In contrast, heating a partially oxidized sample yields an XRD diffraction pattern that contains the 002 peak of the pristine graphite, as shown in FIG. 4b. Example 9 Large area SAED patterns (FIG. 5) demonstrate enhanced exfoliation of the layers. The diffusion rings (51 and 52) are very weak and diffuse. These weak and diffuse diffraction rings, typically observed with disordered or amorphous materials, suggest that the alignment between the sheets and the long-range coherence along the c direction is essentially lost in the thermal exfoliation. Due to the elimination of water and some oxygen functional groups during the rapid heating step, the structure of TEGO has a higher C/O ratio than the parent GO. Elemental analysis shows an increase in the C/O ratio of from 6/4 in GO to 8/2 in TEGO. The surface area of TEGO samples prepared from a GO sample that was oxidized for 120 hours and heated for 30 seconds at different temperatures is shown in FIG. 6 ("•" denotes samples dried in vacuum oven for 12 hours at 60° C., and `7" represents samples equilibrated at ambient temperature and relative humidity prior to exfoliation). Note that there is an increase in the surface area as the heating temperature increases. Surface areas of 1500 m2/g are achieved by heating the sample at 1030° C. This value is lower than a theoretical upper surface area of atomically thick graphene sheets, typically 2,600 m2/g. Since the adsorption experiment takes place on a bulk TEGO sample, part of the graphene sheets overlap, thus denying access to N2 molecules, resulting in a lower surface area value. An important aspect for applications involving graphene in polymer matrices is the degree of dispersion, or the effective surface area, in the dispersed state. The TEGO materials disperse readily in polar organic solvents such as THE to form a uniform disper5 sion. Heating temperatures of from about 250-2500° C. may be employed, with a temperature range of from about 5001500° C. preferred. The bulk density of a TEGO sample with a surface area of 800 m2/g was measured gravimetrically to be 4.1 kg/m3. to Another sample with a measured surface area of 1164 m2/g had a bulk density of 1.83 kg/m3. Example 10 For a comparative study of polymer nanocomposite properties, TEGO, SWCNT, and EG were incorporated into PMMA using solution-based processing methods. Thin-film samples (-0.1-mm thick) were prepared using a hot press and fully characterized for thermal, electrical, mechanical, and 20 theological properties (FIG. 16A). Examination of the fracture surface of EG-PMMA and TEGO-PMMA nanocomposites (FIGS. 16B, 16C) reveals an extraordinary difference in the interfacial interaction between the polymer matrix and the nanofiller in these two systems. While the multilayer EG 25 fillers protrude cleanly from the fracture surface indicating a weak interfacial bond, the protruding TEGO plates of the present invention are thickly coated with adsorbed polymer indicating strong polymer-TEGO interaction. The present inventors suggest that two main differences between EG and 3o TEGO lead to these interaction differences: First, distortions caused by the chemical functionalization of the "sp2" graphene sheet and the extremely thin nature of the nanoplates lead to a wrinkled topology at the nanoscale. This nanoscale surface roughness leads to an enhanced mechani35 cal interlocking with the polymer chains and consequently, better adhesion. Such an effect is in agreement with the recent suggestion by molecular dynamic studies that show altered polymermobility dueto geometric constraints atnanoparticle surfaces. Second, while the surface chemistry of EG is rela40 tively inert, TEGO nanoplates contain pendant hydroxyl groups across their surfaces, which may form hydrogen bonds with the carbonyl groups of the PMMA. Together with TEGO's high surface area and nanoscale surface roughness, this surface chemistry is believed to lead to stronger interfa45 cial bonding of TEGO nanoplates with PMMA and thus substantially larger influence on the properties of the host polymer. In polymer nanocomposites, the very high surface-to-volume ratio of the nanoscale fillers provides a key enhancement 50 mechanism that is equally as important as the inherent properties of the nanofillers themselves. Because the surface area of the nano filler particles can fundamentally affect the properties of the surrounding polymer chains in a region spanning several radii of gyration surrounding each individual nano55 particle, it is most preferred to have an optimal dispersion of the particles within the polymer matrix. The high surface area and oxygen functional groups in the present invention TEGO nanoplates offer a superb opportunity to achieve outstanding dispersion and strong interfacial properties of nanofiller in 60 polymers. While SWCNTs may offer similar potential without the inherent chemical functionality, in practice it has proven difficult to extract SWCNTs from their bundles to obtain dispersions to the individual tube level which limits their enhancement potential. 65 In FIG. 16A, the thermal and mechanical properties for all three of the aforementioned thin-film samples are provided. Although both glass transition temperature (Tg) and thermal 15 US 8,066,964 B2 25 26 degradation temperature for PMMA increased significantly in the presence of the nanofillers, the TEGO-PMMA nanocomposites significantly outperformed both the EG-PMMA and the SWCNT-PMMA materials. The glass transition, Tg, data are particularly striking: an unprecedented shift of 35' C. occurred for the TEGO-PMMA composite at only 0.05 wt % of the nanofiller. Although the SWCNT-PMMA composite exhibited a broadening of the loss peak, indicating additional relaxation modes in the polymer, no significant shift of T'-was observed even at 1 wt % loading. While the SWCNTs were well distributed in the matrix and well wetted by the polymer, there was evidence of localized clustering leading to nanotube-rich and nanotube-poor regions in the composite. Consequently the SWCNT-PMMA composite retained the rheological signature of bulk PMMA. For the EG-PMMA composite, although no clustering of the EG platelets was observed, the platelets were thicker, resulting in a decrease of the surface area in contact with the polymer and a smaller Tg shift compared to TEGO-PMMA composites. Functionalization of SWCNTs can lead to better dispersion and a similar Tg shift in SWCNT-PMMA composites, but only at 1 wt % loading. Furthermore, functionalizing SWCNTs requires an additional processing step that is not needed for the TEGO material. In the TEGO nanocomposites, good dispersion of the nanoplate filler and strong interaction with the matrix polymer resulted in overlapping interaction zones between the nanoparticles in which the mobility of the polymer chains was altered, leading to a shift in the bulk T g of the nanocomposite at very low weight fractions. The room temperature values for tensile Young's modulus (E), ultimate strength, and the values for storage modulus at elevated temperatures followed a similar trend: the values for TEGO-PMMA exceeded those for SWCNT- and EG-PMMA composites. This increased enhancement in mechanical properties for TEGO-PMMA nanocomposite can again be attributed to the superior dispersion of the TEGO in the polymer matrix and their intimate interactions. Even with the partial clustering of the SWCNTs and the lower surface area of the EG platelets, some enhancement of polymer properties was observed; however, the TEGO nanoplates are believed to fundamentally alter the behavior of the entire polymer matrix even at low wt % loadings. While GO itself is electrically non-conducting, an important feature of TEGO is its substantial electrical conductivity. The longitudinal electrical conductivity of our TEGOPMMA nanocomposite greatly surpasses those of pure PMMA and SWCNT-PMMA nanocomposites (Table 1). TABLE 1 Electrical conductivity of different nanoscale reinforcements in PMMA at 5 wt % loading. PMMA SWCNT/PMMA EG/PMMA TEGO/PMMA DC transverse conductivity (S/m) DC longitudinal conductivity (S/m) <1E-10 4.7E-03 1.1E-03 2.9E-02 <1E-10 0.5 33.3 4.6 Conductivity measured byAC impedance spectroscopy through the thiclmess for transverse values and measured by a four-probe steady-state method along the length of the samples for longitudinal values. That the composites of the present invention approach the conductivity value measured for the EG-PMMA system suggests the presence of a significant conjugated carbon network in the thin TEGO nanoplates consistent with the observation that GO underwent partial deoxygenation (reduction) during its rapid high temperature exfoliation into TEGO. The data obtained in the comparison also indicate that all three nanocomposite samples were anisotropic, yielding a significantly higher conductivity longitudinally at the same percolation threshold (1-2 wt % level, FIG. 15). For the 5 wt % samples, 5 basic geometric constraints dictate that the nanoplates cannot be oriented randomly in space. For flat disks with an aspect ratio of 100, complete random orientation is possible only at volume fractions less than 5% using an Onsager-type model. As the TEGO nanoplates and processed EG have aspect ratios 10 of —250-1000, an isotropic arrangement is not possible. This geometric constraint, combined with the hot-press processing method used to prepare the nanocomposite samples, thus results in partial orientation of the nanoplates parallel to the top and bottom faces of the samples. The EG/PMMA had a 15 higher anisotropy ratio ostensibly due to the more rigid nature of the thicker plates, leading to more longitudinal alignment and higher conductivity. As the conductivity of filled composites is controlled by the filler's conductivity and contact resistance between filler particles and the number of filler 20 contacts, it appears that the combination of flexibility and crumpling morphology of the TEGO plates, together with their exceedingly high aspect ratio, enables percolation at low concentrations. The longitudinal conductivity of the present invention TEGO-PMMA sample was several times that 25 quoted for 4-6 wt % iodine-doped polyacetylene blended with polyethylene (1 S/m). That the conductivity of 5 wt % TEGO-PMMA composite is quite close to the conductivity for several commercially important conducting polymer such as polythiophene and 30 polyaniline opens up potential uses for TEGO-polymer nanocomposites in electronic and photonic applications. In addition, since single-layer graphene has been dubbed a zero-gap semiconductor or small overlap semi-metal as well as the material of choice for true nanoscale metallic transistor appli35 cations, novel graphite oxide-derived nanosize conducting materials such as TEGO offer very attractive opportunities indeed. Example 11 40 Mechanical Properties of TEGO Filled Polymer Nanocomposites TEGO/PMMA composites with different weight percentages such as 0.25, 0.5, 1, 2, and 5% were prepared using a 45 solution evaporation technique. TEGO/PMMA composite thin films were made using a hot-press molding method. Viscoelastic response of these composites was measured using Dynamic Mechanical Analysis (DMA). Strips of uniform width composite film were cut from the film using a 5o razor blade. A tensile force with 0.1 N pre-load was applied to the test specimen using a `film tension clamp' in DMA. Then the specimen had applied to it, a dynamic oscillatory force with frequency of 1 Hz. The dynamic properties such as storage modulus (E'), loss modulus (E") and tan 6 values were 55 measured with temperature sweep between 25° C. and 170° C. at the rate of 3° C./min. Storage modulus (E') vs. temperature response is shown in FIG. 17. Storage modulus increment is in the range from 40% for 0.25% weight of TEGO to the maximum of 85% for 1% weight of TEGO than that of 60 PMMA. Further increasing the TEGO concentration decrease the storage modulus. Storage modulus (average taken from 4 or 5 samples for each weight percent) vs. weight percentage of TEGO is shown in FIG. 18. It is believed that the reason for decrease in storage modu65 lus for higher TEGO content maybe due to cavities (voids) or clumping of particles, which are seen in SEM pictures in FIG. 19. The storage modulus for expanded graphite in each of US 8,066,964 B2 27 (EG)/PMMA and (EG)/PE has been previously shown to increase with filler content up to a few weight percent. However, the surface of the expanded graphite and TEGO are quite different from each other. The presence of oxide in the surface of TEGO may create a strong mechanical interaction or inter- 5 locking between the polymer and reinforcement particles. In addition, the TEGO platelets are considerably thinner than the EG plates. Consequently, the limiting volume fraction for ideal, isolated plate, random dispersion without encountering 10 effects of particle clumping will preferably be lower for the TEGO particles. The samples here at 1 wt % exhibit an increase of modulus of nearly 100%, while the published data on EG/PMMA achieved an increase of only 10%. FIG. 20 shows that a significant shift is seen in the tan 6 15 peak for TEGO/PMMA composites. The glass transition temperature is normally measured using the tan 6 peak. It is evident that Tg is nearly 40% higher for TEGO/PMMA composite than pure PMMA, compared to the reported EG/PMMA composites which showed only a 12%-20% 20 increment in Tg by tan 6 peak shift for composites with 1 wt %-3 wt % respectively. An interesting feature in Tg is that the tan 6 peak shift is nearly constant for all volume fractions, but the peak broadens considerably with the higher volume fractions. Since the Tg is related to the molecular mobility of the 25 polymer, it may considered to be affected by molecular packing, chain rigidity and linearity. Since the TEGO plates have a high surface area and thickness on the order of the Rg for a polymer chain, well-dispersed TEGO can have a significant impact on a large volume fraction of local polymer. In this 30 manner, the interaction of the polymer chains with the surface of the particles can drastically alter the chain kinetics in the region surrounding them even at lower reinforcement content. From FIG. 20, it is evident that chain mobility is altered at the low concentrations and increasing reinforcement load- 35 ing appears not to change the major shift in Tg but instead to add additional relaxation modes, perhaps by interconnectivity of the particles at higher loadings. The translation of Tg is indicative that the TEGO particle interaction with the polymer matrix is nearly all-inclusive: very little "bulk" polymer 40 remains. A consistent result on Tg was observed by DSC experiment for these composite samples. FIG. 21 shows the thermal degradation of the samples. It is clearly seen that the degradation temperature for the composites are shifted up to 15% higher than that of pure polymer. 45 Again, this is viewed as evidence that the TEGO plates are acting to change the nature of the polymer as a whole in the composite. AC impedance measurements at room temperature were recorded using a Solarkron 1290 impedance analyzer with a So 1296 dielectric interface. The sample was sandwiched between two rectangular copper electrodes with dimension of 21 mmx6 mm held tight to the specimen by two flat polycarbonate plates. Electrically conductive paste (graphite particle filled epoxy) was applied between the copper electrode and 55 sample in order to eliminate the point contacts due to the surface roughness of the composite surface. FIG. 22 shows that a significant reduction in the real Z (resistance) is observed with increasing reinforcement filler content. A sharp decease of real Z for 2% and higher TEGO concentration indicates the onset of electrical percolation. Increase of 60 electrical conductivity has been previously reported for EG/PMMA and graphite/PMMA composites over that of 28 pure PMMA. Further the literature suggests that the difference in conductivity behavior between EG/PMMA and graphite/PMMA at higher filler concentration is due to the enhanced number of conductivity paths in the EG composites. Similar results werereported in HDPE/graphite composites with different filler sizes. The electrical conductivity of the present invention composites exhibited a pronounced transition with the increase of filler content, from an insulator to nearly a semiconductor at the percolation limit. All references cited herein are incorporated by reference. Numerous modifications and variations on the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. The invention claimed is: 1. A modified graphite oxide material, comprising: a thermally exfoliated graphite oxide (TEGO) having a surface area of from about 500 m 2/g to about 2600 m2/g, wherein the thermally exfoliated graphite oxide has an X-ray diffraction pattern in which an area under a diffraction peak between 20=12.5 and 14.5° is less than 15 percent of a total area under a diffraction peak between 20=9 and 21'. 2. The modified graphite oxide material as claimed in claim 1, wherein said TEGO has a bulk density of from about 40 kg/m3 to 0.1 kg/m3. 3. The modified graphite oxide material as claimed in claim 1, wherein said TEGO has a C/O ratio of from about 60/40 to 95/5. 4. The modified graphite oxide material as claimed in claim 3, wherein said TEGO has a C/O ratio of from about 65/35 to 95/5. 5. The modified graphite oxide material as claimed in claim 4, wherein said TEGO has a C/O ratio of from about 65/35 to 90/10. 6. The modified graphite oxide material as claimed in claim 5, wherein said TEGO has a C/O ratio of from 65/35 to 85115. 7. The modified graphite oxide material as claimed in claim 6, wherein said TEGO has a C/O ratio of from 70/30 to 85115. 8. The modified graphite oxide material as claimed in claim 7, wherein said TEGO has a C/O ratio of from 70/30 to 80/20. 9. The modified graphite oxide material as claimed in claim 1, wherein the thermally exfoliated graphite oxide has a surface area of from 500 m2/g to 2600 m2/g. 10. The modified graphite oxide material as claimed in claim 1, wherein the thermally exfoliated graphite oxide has a surface area of from 600 m 2/g to 2600 m2/g. 11. The modified graphite oxide material as claimed in claim 1, wherein the thermally exfoliated graphite oxide has a surface area of from 700 m 2/g to 2600 m2/g. 12. The modified graphite oxide material as claimed in claim 1, wherein the thermally exfoliated graphite oxide has a surface area of from 800 m 2/g to 2600 m2/g. 13. The modified graphite oxide material as claimed in claim 1, wherein the thermally exfoliated graphite oxide has a surface area of from 900 m 2/g to 2600 m2/g. 14. The modified graphite oxide material as claimed in claim 1, wherein said thermally exfoliated graphite oxide displays no signature of graphite and/or graphite oxide, as determined by X-ray diffraction.