Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K7/00—Use of ingredients characterised by shape
  • C08K7/22—Expanded, porous or hollow particles
  • C08K7/24—Expanded, porous or hollow particles inorganic
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/005—Reinforced macromolecular compounds with nanosized materials, e.g. nanoparticles, nanofibres, nanotubes, nanowires, nanorods or nanolayered materials
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/011—Nanostructured additives

Definitions

• the invention relates generally to polymeric materials incoiporating a carbon nanomaterial. More particularly, the present invention relates to polymeric materials incorporating carbon nanospberes. ⁇ . The Related Technology
• Carbon materials have been used in a variety of fields as high-performance and functional materials.
• Graphite is a well-known carbon material that has important properties such as conductivity and inertness.
• researchers have learned to manufacture graphitic structures on a nanometer scale.
• the most widely researched and understood graphitic nanostructures are carbon nanorubes.
• researchers have developed methods of making other carbon nanostructures such as carbon "na ⁇ -onions,” “nanohorns,” “nanobeads,” “nanofibers,” etc.
• the present invention relates to novel composites that incorporate a carbon nanomaterial into a polymeric material.
• the carbon nanomaterial includes carbon nanostructures that give the polymeric composites novel properties.
• the carbon nanostructures incorporated into the polymeric material are carbon nanospheres.
• the carbon nanospheres typically have multiple walls of graphite that define a generally round, hollow nanoparticle.
• the nanospheres can be made in various sizes.
• the outer diameter is in a range from about 2 nm to about 500 nm, more preferably from about 5 nm to about 250 nm, and most preferably from about 10 nm to about 150 nm.
• the inside diameter of the nanospheres depends on the outer diameter of the nanosphere and the wall thickness.
• the inside diameter (i.e., the diameter of the hollow portion) is typically between about 0.5 nm and about 300 nm, more preferably between about 2 nm and about 200 nm, and most preferably between about 5 nm and about 100 nm.
• the carbon nanomaterial can be treated to make the nanomaterial more dispersable in a polymeric material and/or to remove functional groups (e.g., acidic groups) from its surface.
• functional groups e.g., acidic groups
• carboxylic acid and other oxygenated functional groups are removed using a neutralizing base.
• the dispersability of the nanomaterial is improved by heat treating the material after it has been purified with oxidative agents.
• the polymeric material used to make the composite can be any polymer or polymerizable material compatible with graphitic materials.
• Example polymers include polyamines, polyacrylates, polybutadienes, polybutylenes, polyethylenes, polyethylenechlorinates, ethylene vinyl alcohols, fiuoropolymers, ionomers, polymethylpentenes, polypropylenes, polystyrenes, polyvinylchlorides, polyvinylidene chlorides, polycondensates, polyamides, polyamide-imides, polyaryletherketones, polycarbonates, polyketones, polyesters, polyetheretherketones, polyetherimides, polyethersulfones, polyimides, polyphenylene oxides, polyphenylene sulfides, polyphthalamides, polythalimides, polysulfones, polyarylsulfones, allyl resins, melamine resins, phenol-formaldehyde resins, liquid crystal polymers, poly
• the carbon nanospheres are mixed with the polymeric material in a range of about 0.1% to about 70% by weight of the composite, more preferably in a range of about 0.5% to about 50% by weight, and most preferably in a range of about 1.0% to about 30%.
• the carbon nanospheres can be added alone or in combination with other graphitic materials to give the composite conductive properties.
• any known method can be used.
• pellets or powder of the polymeric material and a desired amount of the carbon nanospheres can be dry-blended or wet-blended and then mixed in a roll kneader while heated, or fed in an extrusion machine to extrude as a rope and then cut into pellets.
• the carbon nanospheres can be blended in a liquid medium with a solution or dispersion of the resin.
• the carbon nanospheres can be mixed with a monomer or oligomer using any known method suitable for the particular resin.
• Nanospheres are much easier to disperse within polymeric or polymerizable materials owing to their more spheroidal shape. This allows nanospheres to be dispersed more easily like a particulate filler rather than a fibrous material. Fibrous materials are typically much more difficult to disperse than particles and require much higher shearing forces to ensure good dispersion. Nanospheres, in contrast, can be blended with polymeric and polymerizable materials using lower shear. Using lower shear to blend nanospheres is less likely to degrade the graphitic material and the polymeric materials into which it is dispersed.
• any known methods and/or materials suitable for use with graphitic carbon can be used.
• any known method for molding into a desired shape any known method such as extrusion molding, blow molding, injection molding, or press molding can be used.
• the composite materials of the present invention can have beneficial properties that result from the unique shape, chemistry and other features of the carbon nanospheres incorporated therein.
• carbon nanospheres can reduce the electrical resistance of many polymers significantly more than a comparable amount of carbon nanotubes or carbon black. For example, where about 16 wt% of carbon black or 7 wt% carbon nanotubes in a polymeric material will achieve a desired low electrical resistance, surprisingly, only about 3 wt% of carbon nanospheres is needed to achieve the same desired low electrical resistance.
• Figures IA is a high resolution SEM image of a carbon nanomaterial formed according to an embodiment of the present invention, which includes a plurality of nanosphere clusters;
• Figure IB is a high resolution SEM image showing a closer image of individual clusters of carbon nanostructures and showing one cluster that has been broken open to reveal the plurality of carbon nanostructures that make up the cluster;
• Figure 2 is a high resolution TEM image of the carbon nanomaterial of Figure
• Figure 3 is a high resolution TEM image showing a close up of a carbon nanostructure that has a catalytic templating nanoparticle in its center;
• Figure 4 shows the intensity of x-ray diffraction of the carbon nanomaterial of
• Figure 5 is a graph showing the Raman spectra of a carbon nanomaterial manufactured according to the present invention and showing differences in the carbon nanomaterial as a result of different heat treatments;
• Figure 6 is a high resolution TEM of a purified intermediate carbon material manufactured according to the invention, but that has not been treated to remove functional groups;
• Figure 7 is a high resolution TEM of the carbon nanomaterial of Figure 6 that has been treated with a base to remove functional groups
• Figure 8 is an image of a polymer with the purified intermediate carbon material of Figure 6 incorporated therein;
• Figure 9 is an image of a polymer with the carbon nanomaterial of Figure 7 incorporated therein.
• DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS I. COMPONENTS USED TO MANUFACTURE THE COMPOSITES
• the composite polymeric materials of the invention include a mixture of a polymeric material and a carbon nanomaterial.
• the carbon nanomaterial includes carbon nanospheres, which give the composite novel properties such as reduced electrical resistance.
• the composite polymeric materials can also include other additives such as fillers or other carbon nanomaterials.
• the term nanosphere includes graphitic, hollow particles or balls that have a regular or irregular outer shape.
• the polymeric material can be a polymer or a polymerizable material.
• the polymeric material can be a synthetic, natural, or modified natural polymer or resin. Suitable polymeric materials include thermoset and thermoplastic polymers and/or polymerizable materials.
• Suitable polymeric materials useful in the composites of the present invention include the following polymers (and/or polymerizable materials selected to form one or more of the following polymers): polyamines, polyacrylates, polybutadienes, polybutylenes, polyethylenes, polyethylenechlorinates, ethylene vinyl alcohols, fluoropolymers, ionomers, polymethylpentenes, polypropylenes, polystyrenes, polyvinylchlorides, polyvinylidene chlorides, polycondensates, polyamides, polyamide-imides, polyaryletherketones, polycarbonates, polyketones, polyesters, polyetheretherketones, polyetherimides, polyethersulfones, polyimides, polyphenylene oxides, polyphenylene sulfides, polyphthalamides, polythalimides, polysulfones, polyarylsulfones allyl resins, melamine resins, phenol-formaldehyde resins,
• the polymeric material can be a thermoplastic polymer that is heated and then mixed with the carbon nanospheres.
• a thermoset polymer can be used.
• a thermoset polymer is provided as one or more polymerizable monomers or oligomers and then mixed with the carbon nanospheres and polymerized to form the composite.
• Those skilled in the art are familiar with the monomers and/or oligomers that can be used to form the foregoing polymers.
• polyurethanes are derived from a reaction between an isocyanate group and a hydroxyl group
• polyureas are derived from the reaction between an isocyanate and an amine
• silicones can be derived from the hydrolysis of silanes and/or siloxanes, etc.
• the present invention also includes copolymers that include blocks of one or more of the polymers listed above. Additional polymers and polymerizable materials are disclosed in U.S. Patent No. 6,689,835.
• thermo-plastic polymerizable materials include acrylonitrile-butadiene-styrene, acrylonitrile-ethylene/propylene-styrene, methylmethacrylate-butadiene-styrene, acrylonitrile-butadiene-methylmethacrylate- styrene, acrylonitrile-n-butylacrylate-styrene, rubber modified polystyrene (high impact polystyrene), polyethylene, polypropylene, polystyrene, polymethylmethacrylate, polyvinylchloride, cellulose-acetate, polyamide, polyester, polyacrylonitrile, polycarbonate, polyphenyleneoxide, polyketone, polysulphone, polyphenylenesulfide, fluoride resin, silicone, polyimide, polybenzimidazole, polyamide elastomer, combinations thereof, and derivatives thereof, and the like.
• thermo-setting resins examples include phenol resin, urea resin, melamine-formaldehyde, urea-formaldehyde latex, xylene resin, diallylphthalate resin, epoxy resin, aniline resin, furan resin, silicon resin, polyurethane resin, combinations thereof, derivatives thereof, and the like.
• a carbon nanomaterial is included in the composite material to give the composite desired properties.
• the novel properties of the composite are due, at least in part, to carbon nanostructures that make up all or a part of the carbon nanomaterial.
• the carbon nanostructures within the carbon nanomaterial have useful properties such as unique shape, size, and/or electrical properties.
• the carbon nanostructures are carbon nanospheres.
• the carbon nanomaterials can include materials other than carbon nanospheres.
• the carbon nanomaterial can include graphite (i.e., graphitic sheets), amorphous carbon, and/or iron nanoparticles.
• the percentage of carbon nanospheres can affect the properties of the composite.
• the weight percent of carbon nanospheres in the carbon nanomaterial is in a range from about 2% to about 100% by weight.
• the percent of carbon nanospheres is at least about 10 wt%, more preferably at least about 15%.
• the novel carbon nanomaterials can be characterized by the absence of surface functional groups.
• the functionalization of the carbon nanomaterial is determined by the acidity of an aqueous wash.
• the carbon nanomaterials have an acid functionalization that gives a wash solution a pH in a range from about 5.0 to about 8.0, more preferably about 6.0 to about 7.5, and most preferably in a range from about 6.5 to about 7.25, based on a 1 :1 weight ratio of washing solution to carbon nanomaterial.
• Carbon nanomaterials that have a pH in the foregoing ranges can be advantageously mixed with polymeric resins that are sensitive to acidic filler materials (e.g.
• the invention includes carbon nanomaterials with a pH outside the foregoing ranges and, if desired, these carbon nanomaterials can be used with polymeric resins that are sensitive to acidic filler materials. 1. Carbon nanospheres
• the carbon nanospheres can be regular or irregularly shaped hollow nanoparticles.
• the carbon nanospheres are generally spheroidal in shape.
• the carbon nanostructures are manufactured from templating nanoparticles and a carbon precursor. During this process, the carbon nanostructures form around the templating nanoparticles. In this embodiment, the size and shape of the nanostructure is determined in large part by the size and shape of the templating nanoparticles. Because the carbon nanostructures form around the templating nanoparticles, the hole or inner diameter of the carbon nanostructures typically corresponds to the outer diameter of the templating nanoparticles. The inner diameter of the carbon nanostructures can be between 0.5 nm to about 90 nm.
• Figures IA and IB show SEM images of example nanospheres made using catalytic templating nanoparticles, the details of which are described in Example 1 below.
• Figures 2 and 3 are TEM images of the nanomaterial shown in Figures IA and IB. The TEM images interpreted in light of the SEM images show that in one embodiment the nanospheres can have a generally spheroidal shape.
• the SEM image reveals that, at least in some embodiments, the carbon nanomaterial includes spheroidal or "grape-like" clusters of carbon nanospheres.
• Figure IB is a close-up of a cluster of carbon nanospheres that has been partially broken open thereby exposing a plurality of carbon nanospheres.
• the TEM image in Figure 2 further shows that the clusters are made up of a plurality of smaller nanospheres.
• the cluster of nanospheres in Figure 2 reveals that the nanostructures are hollow and generally spheroidal.
• Figure 3 is an even closer view of a carbon nanosphere that appears to have an iron templating nanoparticle remaining in its center.
• the carbon nanospheres of Figure 3 illustrates that the formation of the carbon nanostructures occurs around the catalytic templating nanoparticles.
• the outer diameter of the nanospheres is between about 10 nm and about 60 nm and the hollow center diameter is about 10 nm to about 40 nm.
• the present invention includes nanostructures having larger and smaller diameters.
• the carbon nanospheres have an outer diameter that is less than about 100 nm to maintain structural integrity.
• the thickness of the nanosphere wall is measured from the inside diameter of the wall to the outside diameter of the wall.
• the thickness of the nanostructure can be varied during manufacture by limiting the extent of polymerization and/or carbonization of the carbon precursor as described below.
• the thickness of the carbon nanosphere wall is between about 1 nm and 20 nm.
• thicker and thinner walls can be made if desired.
• the advantage of making a thicker wall is greater structural integrity.
• the advantage of making a thinner wall is greater surface area and porosity.
• the wall of the carbon nanostructure can also be formed from multiple graphitic layers.
• the carbon nanospheres have walls of between about 2 and about 100 graphite layers, more preferably between about 5 and 50 graphite layers and more preferably between about 5 and 20 graphite layers.
• the graphitic characteristic of the carbon nanostructures is believed to give the carbon nanostructures beneficial properties that are similar to the benefits of multi-walled carbon nanotubes (e.g., excellent conductivity).
• the carbon nanospheres can be substituted for carbon nanotubes and used in many applications where carbon nanotubes can be used but often with predictably superior results and/or reduced costs.
• the present invention extends to nanostructures having shapes other than spheriodal.
• the nanostructures may be fragments of what were originally spheriodal shaped nanospheres.
• the shape of the carbon nanostructure will be at least partially determined by the shape of the templating nanoparticles.
• formation of non-spherical templating nanoparticles can lead to carbon nanostructures with non-spheroidal dimensions.
• the carbon nanostructures of the present invention can have high porosity and large surface areas. Adsorption and desorption isotherms indicate that the carbon nanostructures form a mesoporous material.
• the BET specific surface area of the carbon nanostructures can be between about 80 and about 400 m /g and is preferably greater than about 120 m /g, and typically about 200 m /g, which is significantly higher than the typical 100 m /g observed for carbon nanotubes. Even where the methods of the invention results in carbon nanostructures combined with non- structured graphite, this graphitic mixture (i.e., the carbon nanomaterial) typically has a surface area greater than carbon nanotubes.
• the carbon nanostructures of the present invention can be manufactured using all or a portion of the following steps: (i) forming a precursor mixture that includes a carbon precursor and a plurality of templating nanoparticles, (ii) allowing or causing the carbon precursor to polymerize around the catalytic templating nanoparticles, (iii) carbonizing the precursor mixture to form an intermediate carbon material that includes a plurality of nanostructures (e.g., carbon nanospheres), amorphous carbon, and catalytic metal, (iv) purifying the intermediate carbon material by removing at least a portion of the amorphous carbon and optionally a portion of the catalytic metal, and (v) optionally removing at least a portion of any functional groups that remain on the surface of the purified intermediate carbon material by heat treating the purified intermediate material and/or treating the purified intermediate material with a base.
• steps forming a precursor mixture that includes a carbon precursor and a plurality of templating nanoparticles, (ii) allowing
• the precursor mixture is formed by selecting a carbon precursor and dispersing a plurality of catalytic templating nanoparticles in the carbon precursor.
• any type of carbon material can be used as the carbon precursor of the present invention so long as it can disperse the templating particles and carbonize around the templating particles upon heat treating.
• suitable polymerizable carbon precursors include resorcinol-formaldehyde gel, resorcinol, phenol resin, melamine- formaldehyde gel, poly(furfuryl alcohol), poly(acrylonitrile), sucrose, petroleum pitch, and the like.
• Other polymerizable benzenes, quinones, and similar compounds can also be used as carbon precursors and are known to those skilled in the art.
• the carbon precursor is a hydrothermally polymerizable organic compound. Suitable organic compounds of this type include citric acid, acrylic acid, benzoic acid, acrylic ester, butadiene, styrene, cinnamic acid, and the like.
• the catalytic templating nanoparticles which are dispersed in the carbon precursor, can be provided in several different ways.
• the templating nanoparticles can be formed in the carbon precursor (i.e., in-situ) or formed in a separate reaction mixture and then mixed with the carbon precursor. In some cases, particle formation may partially occur in a separate reaction and then be completed as the templating particles are mixed and/or heated in the carbon precursor (e.g., at the onset of a precursor polymerization step).
• the templating nanoparticles can also be formed using a dispersing agent that controls one or more aspects of particle formation or the templating nanoparticles can be made from metal salts.
• the templating nanoparticles are formed in the carbon precursor from a metal salt.
• the templating nanoparticles are formed by selecting one or more catalyst metal salts that can be mixed with the carbon precursor. The metal salts are mixed with the carbon precursor and then allowed or caused to form nanoparticles in-situ.
• the templating particles are formed (in-situ or ex-situ) using a dispersing agent to control particle formation.
• a dispersing agent to control particle formation.
• one or more types of catalyst atoms and one or more types of dispersing agents are selected.
• the dispersing agent is selected to promote the formation of nanocatalyst particles that have a desired stability, size and/or uniformity.
• Dispersing agents within the scope of the invention include a variety of small organic molecules, polymers, and oligomers.
• the dispersing agent is able to interact and bond with catalyst atoms dissolved or dispersed within an appropriate solvent or carrier through various mechanisms, including ionic bonding, covalent bonding, Van der Waals interaction/bonding, lone pair electron bonding, or hydrogen bonding.
• the catalyst atoms e.g., in the form of a ground state metal or metal salt
• dispersing agent e.g., in the form of a carboxylic acid or its salt
• the catalyst complexes are generally formed by first dissolving the catalyst atoms and dispersing agent in an appropriate solvent and then allowing the catalyst atoms to bond with the dispersing agent molecules.
• the various components may be combined or mixed in any sequence or combination, hi addition, a subset of the components can be premixed prior to addition of other components, or all components may be simultaneously combined.
• the components for the templating nanoparticles are allowed or caused to form nanoparticles by mixing the components for a period of about 1 hour to about 14 days. This mixing is typically conducted at temperatures ranging from 0 0 C to 200 0 C. In one embodiment, the temperature does not exceed 100 0 C. Particle formation can also be induced using a reagent. For example, in some cases formation of particles or intermediate particles can be caused by bubbling hydrogen through the solution of catalyst complexes.
• the templating nanoparticles of the present invention are capable of catalyzing polymerization and/or carbonization of the carbon precursor.
• concentration of catalytic templating nanoparticles in the carbon precursor is typically selected to maximize the number of carbon nanostructures formed.
• the amount of catalytic templating particles can vary depending on the type of carbon precursor being used.
• the molar ratio of carbon precursor to catalyst atoms is about 0.1 :1 to about 100:1, more preferably about 1 : 1 to about 30:1.
• suitable catalyst materials include iron, cobalt, nickel, and the like.
• the precursor mixture is typically allowed to cure for sufficient time such that a plurality of intermediate carbon nanostructures are formed around the templating nanoparticles. Because the templating nanoparticles are catalytically active, the templating nanoparticles can preferentially accelerate and/or initiate polymerization of the carbon precursor near the surface of the templating particles.
• the time needed to form intermediate nanostructures depends on the temperature, the type and concentration of the catalyst material, the pH of the solution, and the type of carbon precursor being used.
• the intermediate carbon nanostructures can be individual organic structures or an association of nanostructures that break apart during carbonization and/or removal of amorphous carbon.
• Ammonia added to adjust the pH can also effect polymerization by increasing the rate of polymerization and by increasing the amount of cross linking that occurs between precursor molecules.
• polymerization typically occurs at elevated temperatures.
• the carbon precursor is heated to a temperature of about 0 0 C to about 200 0 C, and more preferably between about 25 °C to about 120 °C.
• An example of a suitable condition for polymerization of resorcinol- formaldehyde gel is a solution temperature between 0 0 C and 90 0 C and a cure time of less than 1 hour to about 72 hours.
• a suitable condition for polymerization of resorcinol- formaldehyde gel is a solution temperature between 0 0 C and 90 0 C and a cure time of less than 1 hour to about 72 hours.
• the polymerization is not allowed to continue to completion. Terminating the curing process before the entire solution is polymerized can help to form a plurality of intermediate nanostructures that will result in individual nanostructures, rather than a single mass of carbonized material.
• the present invention includes embodiments where the carbon precursor forms a plurality of intermediate carbon nanostructures that are linked or partially linked to one another.
• individual nanostructures are formed during carbonization and/or during the removal of amorphous carbon.
• Forming intermediate carbon nanostructures from the dispersion of templating nanoparticles causes formation of a plurality of intermediate carbon nanostructures having unique shapes and sizes.
• the properties of the nanostructure can depend at least in part on the shape and size of the intermediate carbon nanostructure. Because of the unique shapes and sizes of the intermediate carbon nanostructures, the final nanostructures can have beneficial properties such as high surface area and high porosity, among others.
• the precursor mixture is carbonized by heating to form an intermediate carbon material that includes a plurality of carbon nanostructures, amorphous carbon, and catalyst metal.
• the precursor mixture can be carbonized by heating the mixture to a temperature between about 500 0 C and about 2500 0 C.
• atoms such as oxygen and nitrogen are volatilized or otherwise removed from the intermediate nanostructures (or the carbon around the templating nanoparticles) and the carbon atoms are rearranged or coalesced to form a carbon-based structure.
• the carbonizing step typically produces a graphite based nanostructure.
• the graphite based nanostructure has carbon atoms arranged in structured sheets of sp hybridized carbon atoms.
• the graphitic layers can provide unique and beneficial properties, such as electrical conduction and structural strength and/or rigidity.
• the intermediate carbon material is purified by removing at least a portion of non-graphitic amorphous carbon. This purification step increases the weight percent of carbon nanostructures in the intermediate carbon material.
• the amorphous carbon is typically removed by oxidizing the carbon.
• the oxidizing agents used to remove the amorphous carbon are selective to oxidation of the bonds found in non-graphitic amorphous carbon but are less reactive to the pi bonds of the graphitic carbon nanostructures.
• the amorphous carbon can be removed by applying the oxidative agents or mixtures in one or more successive purification steps.
• Reagents for removing amorphous carbon include oxidizing acids and oxidizing agents and mixtures of these.
• An example of a mixture suitable for removing amorphous carbon includes sulfuric acid, KMnO 4 , H 2 O 2 , 5M or greater HNO 3 , and aqua regia.
• substantially all or a portion of the catalytic metals can be removed. Whether the catalytic metal is removed and the purity to which the catalytic metal is removed will depend on the desired use of the carbon nanomaterial. In some embodiments of the invention, the presence of a metal such as iron can be advantageous for providing certain electrical properties and/or magnetic properties.
• the templating nanoparticles are removed using acids or bases such as nitric acid, hydrogen fluoride, or sodium hydroxide.
• acids or bases such as nitric acid, hydrogen fluoride, or sodium hydroxide.
• the method of removing the templating nanoparticles or amorphous carbon depends on the type of templating nanoparticle or catalyst atoms in the composite.
• Catalyst atoms or particles e.g., iron particles or atoms
• Any removal process can be used to remove the templating nanoparticles and/or amorphous carbon so long as the removal process does not completely destroy the carbon nanostructures. In some cases it may even be beneficial to at least partially remove some of the carbonaceous material from the intermediate nanostructure during the purification process.
• the oxidizing agents and acids can have a tendency to introduce hydronium groups and oxygenated groups such as, but not limited to, carboxylates, carbonyls, and/or ether groups to the surface of the carbonaceous materials. It is believed that the functional groups may be on the surface of the carbon nanostructures, graphite mixed with the carbon nanostructures, and/or remaining non-graphitic amorphous carbon.
• the functional groups on the surface of the intermediate carbon material can be removed using either a heat treatment step and/or a neutralizing base. Removing the surface functional groups and/or neutralizing the surface functional groups is typically performed in cases where removing and/or neutralizing the functional groups improves the dispersion of the carbon nanomaterial in the polymeric material and/or improves the properties of the composite material.
• the functional groups on the surface of the intermediate carbon material can be removed using a heat treatment step.
• the heat treatment step can be beneficially carried out at a selected temperature, which is selected depending on the particular functional groups that need to be removed. Generally, the higher the temperature of the heat treatment, the more types of functional groups that can be removed.
• the heat treatment step following purification can be carried out at a temperature greater than about 100 0 C, more preferably greater than about 200 0 C and most preferably greater than about 500 0 C.
• the heat treatment following purification can be at a temperature sufficient to carry out carbonization of amorphous carbon.
• heating the intermediate carbon material to a carbonizing temperature after purification can beneficially convert a significant portion of any remaining amorphous carbon to graphite. It has been found that by removing a significant percentage of amorphous carbon in the purification step and then carbonizing the purified material, the remaining carbon can be more easily converted to graphite.
• the graphite formed in this second carbonization step can be added to the carbon nanostructures, the secondary structure of carbon nanostructures (e.g., the grape-like agglomerations of nanospheres), or can ,be free graphite mixed with the carbon nanostructures. Converting residual amorphous carbon to graphite significantly increases the graphitic purity of the carbon nanomaterial. High purity carbon nanomaterials can be produced more efficiently using the two step carbonization method of the invention compared to attempts to achieve the same level of purity in a single carbonization step.
• some functional groups can be removed from the intermediate carbon material using a neutralizing base.
• the intermediate carbon material is mixed with a solution that includes one or more neutralizing bases.
• Suitable bases include hydroxides, including sodium hydroxide and potassium hydroxide, ammonia, Li-acetate, Na-acetate, K-acetate, NaHCO 3 , KHCO 3, Na 2 CO 3, K 2 CO 3, and the like, and combinations of these.
• the reaction of the base with the hydronium group can form byproducts that can be removed by washing with water.
• functional groups are removed by soaking the intermediate carbon material in a washing solution.
• the step to remove functional groups from the carbon nanomaterial may be used to remove functional groups for the carbon nanostructures, amorphous carbon (graphitic or non-graphitic) or any other component of the purified intermediate carbon material.
• the functional groups are removed from the carbon nanostructures or other graphitic materials that form part of the carbon nanomaterial.
• a high temperature heat treating step can also be beneficial if it is desirable to remove certain impurities such as iron, in addition to removing functional groups from the nanomaterials.
• the nanospheres can be manufactured using other suitable technique.
• Methods for making nanomaterials suitable for use in the present invention are disclosed in applicant's co-pending U.S. application Serial No. 11/539,120, filed October 5, 2006, entitled “Carbon Nanorings Manufactured From Templating Nanoparticles” and U.S. application Serial No. 11/539,042, filed October 5, 2006, entitled “Carbon Nanostructures Manufactured From Catalytic Templating Nanoparticles," as well as Han, et al. "Simple Solid-Phase Synthesis of Hollow Graphitic Nanoparticles and their Application to Direct Methanol Fuel Cell Electrodes,” Adv. Mater. 2003, 15. No. 22 November 17, all of which are incorporated herein by reference in their entirety.
• Additives such as fillers or dispersing agents can be added to the polymeric material to give the composite desired properties and/or to disperse the carbon nanospheres in the polymeric material.
• Any filler material can be used with the present invention. Suitable fillers include carbon black, silica, diatomaceous earth, crushed quartz, talc, clay, mica, calcium silicate, magnesium silicate, glass powder, calcium carbonate, barium sulfate, zinc carbonate, titanium oxide, alumina, glass fibers, other carbon fibers, and organic fibers.
• Other suitable additives include softening agents, plasticizers, molding aids, lubricants, anti-aging agents, and UV absorbing agents.
• the composite materials of the present invention are formed by mixing an amount of carbon nanospheres with a polymeric material and optionally one or more additives such as fillers or dispersing agents.
• the carbon nanospheres can be mixed with the polymeric material in a range of about 0.1% to about 70% by weight of the composite, more preferably in a range of about 0.5% to about 50% by weight, and most preferably in a range of about 1.0% to about 30%.
• the carbon nanospheres can be added to the polymeric material in a substantially pure form. Alternatively, the carbon nanospheres can be added to the polymeric material as a component of a carbon nanomaterial. In one embodiment, the carbon nanospheres comprise at least about 2% of the carbon nanomaterial by weight, more preferably at least about 10%, and most preferably at least about 15%.
• the carbon nanospheres When mixed with the polymeric materials of the present invention, the carbon nanospheres can provide unique benefits due to the spheroidal shape of the nanospheres. In contrast to carbon nanotubes, which are fiber like, the carbon nanospheres have a more particle-like shape. In some embodiments of the invention the particle-like shape gives the composite some properties that are more similar to particulate fillers rather than fiber-containing composites.
• the carbon nanospheres can be added to the polymeric material in an amount that provides a desired property.
• the carbon nanospheres can be added to the polymeric material in an amount that imparts electrical conductivity and/or reduces surface resistivity.
• the amount of carbon nanospheres needed to produce a desired reduction in electrical surface resistance is substantially less than the amount of carbon nanotubes or carbon black needed to accomplish the same reduction in resistance. It is believed that the carbon nanomaterials provide this improvement, because of a more uniform network of particles that allows improved percolation as compared to carbon nanotubes. Lower surface resistivity is particularly noticeable for polished surfaces.
• the polymeric composites of the invention have a surface resistivity in a range from about 1x10 4 to about 1x10 6 ( ⁇ /sq) with a carbon nanosphere loading in a range from about 0.5 wt% to about 7 wt%, more preferably in a range from about 1 wt% to about 5 wt%.
• the carbon nanospheres can be incorporated into polymeric material as a flame retardant.
• composites can be manufactured by melting the polymeric materials and then mixing the polymers and carbon nanomaterials together.
• the polymeric material can be made
• pellets or powder of the polymeric material and a desired amount of carbon nanospheres can be dry-blended or wet-blended and then mixed in a roll kneader while heating.
• the mixed composite can be fed into an extrusion machine in order to extrude the composite as a rope and then cut it into pellets.
• the carbon nanospheres can be blended in a liquid medium with a solution or dispersion of the resin. It is also possible to mix the composite by the
• the carbon nanospheres can be mixed with a monomer or oligomer using any known method suitable for the particular polymerizable material.
• any known methods and materials suitable for use with graphitic carbon can be used.
• any known method for molding into a desired shape any known method such as extrusion molding, blow molding, injection molding, or press molding can be used.
• the composites of the present invention may be made into a foamed product by adding a foaming agent in order to obtain a foamed resin with electrical conductivity and/or blackness.
• a foaming agent any of the aforementioned various polymeric materials can be used for making such foamed product, thermo-plastic resins such as polyethylene, polypropylene, polyvinylchloride, polystyrene, polybutadiene, polyurethane, ethylene-vinylacetate copolymer, and the like, and thermo-plastic polymeric materials are preferable.
• a foaming agent various resin foaming agents, organic solvents, as well as gases such as butane can be used.
• any known method can be used as a method for producing the electro- conductive foamed body covered by the present invention.
• a thermo-plastic resin when used, the resin is melted and mixed with a desired amount of the carbon nanospheres by an extrusion machine. Then a gas such as butane is injected into the polymeric material.
• a chemical foaming agent can be used instead of a gas.
• the compound covered by the present invention is also useful as a paint to give electrical conductivity and/or blackness to the surface of other substrates.
• Suitable substrates include various resins, elastomers, rubber, wood, inorganic materials, and the like. In addition these materials can be further molded or formed.
• the desirable thickness of the coated film of such compounds covered by the present invention is greater than 0.1 micron.
• Example 1 describes the preparation of a carbon nanomaterial having carbon nanospheres.
• a 0.1 M iron solution was prepared by using 84 g iron powder, 289 g of citric acid, and 15 L of water.
• the iron-containing mixture was mixed in a closed bottle on a shaker table for 3 days, with brief interruptions once or twice daily to purge the vapor space of the bottle with air gas before resuming mixing.
• the polymerized precursor mixture was placed in a crucible with a cover and transferred to a furnace.
• the carbonization process was carried out under ample nitrogen flow using the following temperature program: room temperature — » 1160 0 C at a rate of 20 °C/min — > hold for 5 hrs at 1160 °C — » room temperature.
• the carbonization step yielded an intermediate carbon material having carbon nanostructures, amorphous carbon, and iron.
• the purification of the carbonized carbon product was performed as follows: reflux carbonized product in 5M HNO 3 for -12 hrs -» rinse with de-ionized (DI)-H 2 O -» treat with a mixture of KMnO 4 + H 2 SO 4 + H 2 O at a mole ratio of 1 : 0.01 : 0.003 (keep at -90 0 C for - 12 hrs) -> rinse with DI-H 2 O ⁇ treat with 4M HCl (keep at -90 0 C for - 12 hrs) ⁇ rinse with Di- H 2 O — » collect the product and dry in the oven at ⁇ 100 °C for two days.
• the carbon nanomaterial manufactured in Example 1 was then analyzed by SEM and TEM.
• the SEM images of the carbon nanostructures are shown in Figure IA and IB, which reveal a plurality of carbon nanospheres that agglomerate to form a cluster that has a grape-like shape.
• the TEM images in Figures 2 and 3 show that the grape-like clusters are made up of a plurality of small, hollow graphitic nanostructure or carbon nanospheres.
• FIG. 4 is a graph showing the X-ray diffraction pattern of the carbon nanomaterial of Example 1.
• the broad peak at about 26° is due to the short range order of graphitic nanostructures. This is in contrast to the typical diffraction pattern of graphite sheets, which tend to have a very narrow peak.
• the broad peak at about 26° also suggests that the material is graphitic, since amorphous carbon tends to have a diffraction peak at 20°.
• Raman spectroscopy was used to determine the graphitic content of the carbon nanomaterial at different temperatures during the heat treating step (e).
• Sample A was taken from the carbon nanomaterial at a heat treated temperature of 1000 0 C
• Sample B was taken during heat treating to 600 0 C
• Sample C was a sample with no heat treating (i.e., Sample C was the purified intermediate carbon material of step (d)).
• the results for Raman Spectroscopy are shown in Figure 5.
• the graph in Figure 5 has two significant peaks, one at 1354 cm “1 and the other at 1581 cm "1 .
• Sample A and B which were heat treated, have larger peaks at 1354 cm "1 .
• the heat treatment step is effective for increasing the graphitic content of any remaining carbon. Surprisingly this conversion can happen at relatively low temperatures, for example, between 500 0 C and 1400 0 C.
• the higher graphitic content of carbon nanomaterial manufactured according to the present invention using an additional heat treatment step results in a carbon nanomaterial with superior conductive properties and purity.
• heat treating was also shown to substantially reduce other impurities such as iron.
• Example 2 describes a carbon nanomaterial manufactured using the same method as Example 1 , except that in step (e) the heat treatment step was replaced with a treatment using a neutralizing base.
• a portion of the purified carbon material obtained in step (d) of Example (1) was mixed with ample amount of DI-H 2 O, followed by drop-wise addition of 5M NaOH to adjust the pH of the solution to ⁇ 7.0.
• the resulting carbon nanomaterial was collected by filtration and rinsed with ample amount of DI-H 2 O to remove Na + ions.
• the final product was collected and dry in an oven at ⁇ 100 0 C for two days.
• Example 2 For comparison purposes, a portion of the purified carbon material obtained in step (d) of Example 1 was collected and was not subject to the heat treatment step described in step (e) of Example 1, nor was it subjected to a neutralizing base as in Example 2.
• the beneficial properties of the acid-free carbon nanomaterial of Example 2 can be illustrated by incorporating the acid-free nanomaterial into a polymer and comparing it to polymers that include nanomaterials that are identical except for the presence of acid functional groups. To test this scenario, the carbon nanomaterials of
• FIG. 8 shows the polymer with the carbon nanomaterial having acid functional groups. This polymer shows significant blistering and irregularities on its surface. In contrast, the polymer that includes the neutralized carbon nanomaterials of Example 2 show a smooth surface.

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