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WO2001016023A1 - Procede de production d'un materiau de carbone nanotubulaire et materiau obtenu - Google Patents

Procede de production d'un materiau de carbone nanotubulaire et materiau obtenu Download PDF

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Publication number
WO2001016023A1
WO2001016023A1 PCT/EP2000/008424 EP0008424W WO0116023A1 WO 2001016023 A1 WO2001016023 A1 WO 2001016023A1 EP 0008424 W EP0008424 W EP 0008424W WO 0116023 A1 WO0116023 A1 WO 0116023A1
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Prior art keywords
carbon
nanotubes
purity
nanotubular
carbide
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PCT/EP2000/008424
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English (en)
Inventor
Tommy Ekström
Michael Jacob
Jie Zheng
Peter Alberius-Henning
Ulrik Palmqvist
Jaan Leis
Anti Perkson
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Ultratec Ltd
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Priority to AU12702/01A priority Critical patent/AU1270201A/en
Publication of WO2001016023A1 publication Critical patent/WO2001016023A1/fr

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    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/16—Preparation
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
    • C04B38/0051—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof characterised by the pore size, pore shape or kind of porosity
    • C04B38/0054—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof characterised by the pore size, pore shape or kind of porosity the pores being microsized or nanosized
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/20—Nanotubes characterized by their properties
    • C01B2202/30—Purity
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/20—Nanotubes characterized by their properties
    • C01B2202/34—Length
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/20—Nanotubes characterized by their properties
    • C01B2202/36—Diameter

Definitions

  • the present invention relates to a method for producing nanoporous carbon materials with nanotube-like structures - here called nanotubes - in large quantities.
  • the invention also relates to the nanotubular carbon material produced by said method.
  • Fullerenes belong to a new type of carbon materials having new properties compared to crystalline carbon diamond, diamond like carbon, and graphite.
  • the fullerenes are closed-cage carbon molecules with each carbon being bonded to three other carbon atoms tiling spherical or nearly spherical surfaces.
  • the carbon atoms are usually arranged in hexagons or pentagons.
  • the most familiar and the smallest of these molecules is the Buckminster fullerene, C 0 , having 60 carbon atoms of a structure resembling a soccer ball with equivalent covalent bonds.
  • Carbon nanotubes are extended fullerene structures and are often referred to as buckytubes. They consist of concentric graphitic cylinders.
  • the carbon nanotube takes almost an infinite number of structures, being characterised e. g. by the diameter and the degree of helicity.
  • the nanotubes can be either single- or multi-walled.
  • the inner tube diameters are typically in the order of some nanometers, and the diameter of the outermost wall could be up to 20-30 nm. Typical aspect ratios (length to diameter) are about 50-100.
  • the separation between the concentric walls are typically about 3.5 A.
  • the nanotubular, nanotube-like material is a porous carbon material consisting of nanotubes having multiple wall aggregates of short tubes that are intergrown with each other. See fig. 1 for the nanotube structure being built up by intergrown short and thick tube-like structures as shown in transmission electron microscopy (TEM). There also exists a nanoporous amorphous carbon material and a lamellar carbon material, described here for the purpose of comparison.
  • TEM transmission electron microscopy
  • the nanoporous amorphous carbon has a structure of interconnected hyperbolic carbon networks building up three-dimensional channel networks with narrow pore size distribution, and the nanoporous lamellar carbon has nanographitic lamellae with around 3-15 graphitic layers in each lamella, where the lamellae may be curved or not, and are interconnected by regions of amorphous carbon to form larger particles. These materials are not nanotube-like and do not belong to the fullerene family.
  • thermochemical treatment is a treatment of a certain carbide or mixture of carbides in gaseous halogen or halogens at elevated temperatures to remove the carbide forming element and to produce a porous carbon material.
  • the rods are evaporated to a light fluffy condensate called fullerene soot. Under suitable conditions substantial fractions of the soot is comprised of fullerenes.
  • the soot also comprises large quantities of carbon impurities such as graphite, amorphous carbon, carbon nanoparticles etc. Thus further extraction and separation of the fullerenes is necessary.
  • This process pioneered the electric arc method for the production of fullerenes and it has since become a standard technique with a large amount of different variants, some of which will be described below.
  • the typical fullerene-soot generators of the above described methods can be divided into small bench-top chambers producing about a few tens of grams per day, and large high- output chambers producing about hundreds of grams of soot per day.
  • the small chambers are usually simple and of low cost. Larger chambers have several disadvantages, such as requiring more complicated equipment and several parameters being more complicated to control, e.g. the installation of rods, pump systems, generation of large amount of heat etc.
  • the prior art arcing methods are not easily scaled up to commercially practical systems.
  • Carbon nanotubes also called buckytubes
  • the needles grow on the cathode, and are comprised of multilayer coaxial tubes of graphitic sheets, with outer diameters up to 30 nm, and lengths up to a few micrometers.
  • Recently the method was further developed to produce a carbon plasma using a typical fullerene production apparatus resulting in carbon nanotubes mixed with nanoparticles.
  • An arc discharge is accomplished by applying a suitable AC or DC potential between graphite rods and having a higher pressure of about 500 Torr 1 (200-2500 Torr) instead of the usual 100-200 Torr.
  • the nanotubes are typically comprised of two or more concentric shells, with diameters ranging from 2-20 nm, and lengths up to several micrometers, and the nanoparticles are typically tens of nanometers in diameter.
  • the nanotubes and nanoparticles are formed under a broader range of conditions than do other fullerenes. There are however no ideal methods for separating these nanotubes from the nanoparticles (graphite and amorphous carbon).
  • One carbon nanotube separation method is to heat a carbon mixture at a temperature of about 750°C (600 - 1000°C) in an oxidising atmosphere to burn away the nanoparticles. The method leaves pure nanotubes but the starting material is consumed to a very large extent. The method has a low yield of carbon nanotubes, since the amount of graphite is so large and the difference in oxidising temperatures between them is not large. An improvement of the production method has been made in order to get longer fullerenes.
  • Fullerene fibres of 0.5 cm or longer can be produced by focusing a laser beam between the growing needle tip and the opposing electrode.
  • a carbon feedstock is placed in the space around the electric field to provide the vaporised carbon.
  • the needle electrode may be moved to lengthen the fullerene network to a fullerene fibre.
  • Other related techniques involve laser ablation of graphite, sputtering or electron beam evaporating of graphite, inductive heating of graphite, vaporisation of graphite powder in an Ar plasma jet and the use of concentrated solar radiation to vaporise graphite etc.
  • the common features are that pure graphite is vaporised in the presence of an inert quenching atmosphere, and that the product is a condensated fullerene bearing soot.
  • Another type of method is the forming of carbon nanotubes on a carbonaceous body (comprising fullerenes, graphite or amorphous carbon) by irradiating a surface of the shaped body with an ion beam to form a layer of carbon nanotubes on the surface by sputtering, resulting in a composite material.
  • a carbonaceous body comprising fullerenes, graphite or amorphous carbon
  • an ion beam to form a layer of carbon nanotubes on the surface by sputtering, resulting in a composite material.
  • An improved method of producing carbon nanotubes is to submerge carbonaceous electrodes in liquid nitrogen or other suitable liquefied materials such as helium or hydrogen.
  • a direct current is passed between the electrodes to strike a plasma arc between the anode and cathode that erodes carbon from the anode and deposits carbon nanotubes on the surface of the cathode.
  • a mechanism for controlling the position of the electrodes that is situated in air above the liquid is used.
  • Another solution to the separation problem is to pulverise a mixture of nanotubes and graphite particles, to disperse them in a liquid and to centrifuge the liquid solution to obtain a precipitate graphite phase and supernatant carbon nanotube and fine graphite phase. The supernatant is then divided into a solid and liquid phase. The solid phase is then heated in oxygen atmosphere to selectively burn away the graphite particles. The purity is improved but the method is complicated.
  • Yet another purification method includes reacting the mixture of nanotubes and graphite with a metal compound to intercalate the metal into the graphite; reducing the reaction mixture and converting the intercalated metal compound to elemental metal, and heating the reduction mixture at 450 - 600°C in an oxygen containing atmosphere to selectively oxidise the graphite and the elemental metal.
  • a process for purifying carbon nanotubes has been reported that avoids the disadvantages of conventional purification of nanotubes by oxidising under high temperatures (about 600-1000°C) that might be difficult to control.
  • the purifying is carried out by reacting a mixture of nanotubes and carbon impurities with liquid phase oxidation, nitration or sulfonation agents at temperatures of about 120-180°C. The impurities are dissolved and the nanotubes may then be separated, washed and dried. Further the nanotubes are reacted once again thereby dissolving carbon fragments (being carbon pentagon rings or carbon impurities) from the tips of the tubes.
  • the yield of nanotubes is rather low. Further, the purity (of nanotube content) is not very high. Typical previously known production methods require elaborate refining methods that are costly, and often also reduce the yield. In view of the above, there remains a need of a method of producing nanoporous carbon materials consisting of nanotube-like carbon, or simply nanotubes, at a low cost, and in large quantities.
  • WO 98/54111 describes a production method for a porous carbon article, said method comprising the steps of first forming a work piece with microporosity, and then forming nanopores in the work piece by a thermochemical process at 350 - 1200°C. Materials having controlled and predetermined nanopores, high mechanical strength, and complicated shapes may be produced. The nanopores generated during the thermochemical treatment process are considered to be formed by ordered or disordered graphite planes of carbon, and to be shaped as slots.
  • WO 97/20333 describes a capacitor with a double electric layer with nanoporous carbon electrodes.
  • the skeleton nanoporous electrodes are made by forming a silicon carbide body, with resin or pyrocarbon binders, saturating the body with liquid silicon at 1450 -1700°C, and treating the body in a gaseous halogen atmosphere at 900 - 1100°C.
  • Al or elements from the groups IV, V, VI of the periodic system of the elements is also mentioned in this document.
  • U.S. Patent 5,876,787 and U.S. Appl. No. 09/193,192 (being a divisional application of the U.S. patent), which describe a process of manufacturing a porous carbon material and a double layer capacitor using the same.
  • the U.S. patent 5,876,787 discloses the method of producing the electrodes.
  • the U.S. application 09/193,192 discloses the electrodes and the capacitor using the electrodes.
  • the process involves forming a blank having a porosity of 30-50 % made of a carbide material of Si or metals from the groups IV, V, and VI of the periodic system of the elements.
  • the blank is then deposited with pyrolytic carbon until the mass has increased about 10-25 %.
  • the blank may optionally be saturated with liquid metal, e.g. Si at 1500 - 1700°C, before it is exposed to gaseous chlorine at 900 - 1100°C (for SiC), about 600°C (for TiC).
  • liquid metal e.g. Si at 1500 - 1700°C
  • gaseous chlorine at 900 - 1100°C (for SiC), about 600°C (for TiC).
  • the carbide forming element and eventual metal from the saturation step is removed and pores are formed.
  • Mass yield The mass of the resulting material produced after thermochemical treatment of aluminium carbide related to the theoretical maximum mass of carbon. This mass may comprise nanotube-like material and other type(s) of carbon(s), residual carbide and possible impurities like aluminium oxide. Theoretically, each kg of A1 4 C 3 would result in, at the most, 250 g carbon.
  • An object of the present invention is to provide a rapid, simple method for the production of nanotube-like carbon materials, which makes it possible to produce the material in large scale.
  • the amount of produced nanotubes by the process depends on the capacity of the equipment (the size of the reaction sites of the furnaces), the heating and cooling of the furnace, and also the diffusion of gaseous halogens and halogenides into and from the structure, all of which are controllable parameters in an industrial process by optimising the equipment and the processing parameters, for instance using equipment of a large capacity and of a "continuous" type (avoiding the interruptions by heating and cooling of the equipment).
  • the process gives large amounts of the produced nanotube-like carbon material, with a high purity of nanotubes.
  • the mass yield of the process is high, i.e.
  • the losses of carbon material in the process are low. Further, the amount of unwanted by-products, produced in the process is also low. It is possible to increase the purity of the nanotubular material, i.e. the amount of the produced nanotubes even more by tuning the process parameters. Thus the process has the advantages of not being dependent of time consuming extraction and purification methods.
  • a further object of the invention is to enable control of mass yield and purity of the nanotubular material produced.
  • the mass yield and the desired purity of the material are to some extent interrelated.
  • the process may be adjusted to give a material of very high purity of nanotubes, which may affect the mass yield, e.g. some carbon or nanotubes may be consumed during a prolonged processing time. Vice versa, an extremely high mass yield may be achieved at some expense of purity.
  • Fig.l shows a TEM image of the nanotubular carbon structure synthesised from aluminium carbide (A1 4 C 3 ) at 700°C;
  • Fig. 2 shows schematically the crystal structure of A1 4 C 3 ;
  • Fig. 3a shows a TEM image of nanotubular carbon synthesised from A1 4 C 3 at 700°C;
  • Fig. 3b shows a TEM image at low magnification of the nanotubular structure synthesised from A1 4 C 3 at 700°C
  • Fig. 3 c shows a TEM image of the nanotubular structure at higher magnification
  • Fig. 4 shows a TEM image of a carbon particle with amorphous structure chlorinated from A1 4 C 3 at 300°C.
  • Fig. 5 shows a TEM image of a carbon particle with nanotubular structure chlorinated from A1 4 C 3 at 600°C.
  • Fig. 6 shows an TEM image of a carbon particle of graphitic-like structure chlorinated from A1 4 C 3 at 1 100°.
  • the large scale synthesis of the nanotubular carbon material, according to the present invention is performed by halogenation of aluminium carbide at elevated temperature, causing the carbide forming element, aluminium, to leave the system as a halogenide, thus leaving a residue of porous carbon.
  • the nanotubes may be synthesised from aluminium carbide of any form, like powders or formed articles (bodies).
  • Nanotubes begin to form from aluminium carbide at furnace temperatures around and above 450 °C and temperatures below 800°C are preferred.
  • chlorinating aluminium carbide at furnace temperatures 500°-800°C, preferably at 550°-750°C, at the chosen process parameters produces a fundamentally different structure than all other tested carbides.
  • nanoporous amorphous carbon multiple wall nanotube-like structures, nanotubes in bulk are produced.
  • the reaction between aluminium carbide and chlorine is exothermic, in order to avoid that the desired nanotubular structure transforms into the more graphitic lamellar type, the reaction must therefore be controlled.
  • the synthesis of the nanotubes depend on the precursor particle size range, the batch size, the temperature, the time, the furnace type used etc.
  • the purity of the produced nanotubular carbon is increased if the aluminium carbide is controlled for presence of oxide and is stored and handled in a way avoiding or minimising exposure to air, and especially humid air.
  • Residual aluminium chloride can be removed from the nanotubular carbon by raising the temperature in Ar atmosphere and letting the chloride sublimate, and residual Cl 2 in the structure may be removed by treatment with H 2 , where Cl is removed by forming HC1, which evaporates out of the structure.
  • H 2 where Cl is removed by forming HC1, which evaporates out of the structure.
  • Other reagents are also possible. - The purity of the process gases is important.
  • the porous carbon structures synthesised from SiC, TiC and Mo 2 C consist of interconnected hyperbolic carbon networks building up porous 3 -dimensional channel networks with a narrow channel size distribution.
  • the pore sizes are a result of the carbon sub-structure of the precursor carbide, which results in smaller nanopores for SiC and TiC, whereas Mo 2 C has larger pores.
  • Aluminium carbide, A1 4 C 3 is the only carbide formed by aluminium, and it has a crystal structure consisting a mixture between hexagonal and cubic close packing of the carbons, with aluminium residing in layers of carbon tetrahedra. See figure 2 showing the crystal structure of A1 4 C 3 .
  • the black spheres are the C atoms inside the tetrahedra and octahedra, with Al at the vertices.
  • nanotubular carbon material from aluminium carbide precursor is synthesized with the following steps, some of them being only optional, i.e. not necessary for the formation of the nanotubular structures:
  • thermochemical treatment is applied to either carbide powder in particle form or to a body produced according to any of the optional steps according to the embodiments described above.
  • the thermochemical treatment is carried out in a medium of gaseous halogen or halogens at elevated temperatures, preferably 450°-800°C, creating volatile halogenides of the carbide forming element (e g Aluminum chloride).
  • the aluminium carbide is transformed to porous carbon, and the formed halogenides are removed from the material, e.g. by the halogen gas flow or by washing in Ar gas.
  • the nanotubes are formed by the halogenation of the aluminium from the aluminium carbide at certain synthesis conditions.
  • the halogenisation is performed at a most preferred limited temperature range around 550°-750°C, the resulting nanoporous bulk structure is comprised of short, thick, multi-layer nanotubes entangled and interconnected to each other.
  • the resulting material comprises nanotubular particles bonded by pyrocarbon, unless the optional step of purification above has been applied.
  • the resulting structure is a nanoporous amorphous one, similar to the structures obtained from halogenisation of e.g. silicon carbide or titanium carbide.
  • the resulting nanoporous structure is a mixture between amorphous and lamellae structure parts; the graphitic characteristics increasing with increasing temperature.
  • These structures contains nanographitic lamellae with around 3-15 graphitic layers in each lamella, where the lamellae may be curved or not, and are interconnected to form larger particles.
  • the halogenation is carried out similarly to other known methods.
  • the halogens and halogenides do not normally react with the formed carbon under the given temperature conditions.
  • the process time may be adjusted depending on the accentuation of a high yield or a high purity.
  • the treatment is carried out at a furnace temperature, i.e. the set temperature for the furnace, of 200°-1200°C.
  • the different nanoporous carbons are formed at the removal of volatile chlorides of the aluminium in accordance with the chlorinating redox reaction: Al 4 C 3 + 6C1 2 ⁇ 3C + 4A1C1 3 (I)
  • the chlorination is performed by leading a Cl 2 (g) stream over the aluminium carbide at an appropriate temperature. It is essential that the carbide forming element, aluminium, forms a volatile chloride.
  • the volatile chloride is lead away from the reaction site by the gas stream. Possible unwanted side-reactions are
  • reaction III can occur for the formed nanoporous carbon at temperatures around 800°C, and above.
  • Another undesirable reaction involving the formed nanoporous carbon is oxidation of carbon with H 2 O or O (which may occur as impurities in Ar and Cl 2 gases) to CO and CO , according to formulas IV, V and VI:
  • the formed H 2 in the reaction according to formula VI can react with the carbon and give hydrocarbons and, because of the presence of chlorine, hydrochlorocarbons.
  • the halogenation reaction of the present invention is simple and proceeds rapidly, which make possible large scale production and the method is new for the production of nanotube-like carbon materials.
  • the mass yield is dependent of the quality of the reactants and can be increased with higher purity of the inlet gas, and by optimising the reaction time and the flow of the inlet gases.
  • the purity also by not exposing the A1 4 C 3 to air, and by evaporating residual A1C1 3 out of the carbon by increasing the temperature.
  • the mass yield may be controlled but to some extent at the expense of purity; not sacrifying any initial carbon material may result in not quite perfect purity because of difficulties in absolute fine tuning of time and temperature.
  • the process may give a nanotubular material of lower purity by changing the process parameters.
  • the aluminium carbide can be formed to a work piece before further treatment.
  • the forming step of the aluminium carbide particles to a work-piece is achieved by any known method, e.g. by pressing with or without a temporary binder or an organic binder that leaves a carbon residue, by using slip, tape or slurry casting, by using injection moulding, or partly sintered by known high pressure, high temperature techniques or using pulsed high currents.
  • the binder is then evaporated or hardened after the forming step.
  • the size and shape of the initially formed work piece is retained during all the different steps to the final body.
  • the work piece porosity and the pore size range are chosen to obtain executability of the following process step(s) and are dependent upon the chosen method of forming the work piece and on particle size(s).
  • the powder or work piece of the aluminium carbide material is further subjected to a treatment in a medium of gaseous hydrocarbon or hydrocarbon mixtures at a temperature exceeding the decomposition temperature of the hydrocarbon(s).
  • a treatment in a medium of gaseous hydrocarbon or hydrocarbon mixtures at a temperature exceeding the decomposition temperature of the hydrocarbon(s).
  • pyrolytic carbon also known as pyrocarbon is deposited on the particles or on the surface and in the pores of the work piece thereby forming an intermediate body.
  • This step is performed to achieve an additional bonding of the carbide particles into a continuous, rigid, porous skeleton structure.
  • the duration of the treatment in the said medium is decided by the mass increase and controlled by measuring the mass of the powder or work piece, and the intermediate body.
  • the process is completed when the strength of the body has increased to the desired level, which usually occurs after the mass has been increased by a few percent.
  • the hydrocarbons used during the treatment in hydrocarbons medium may be selected from the group of acetylene, methane, ethane, propane, pentane, hexane, benzene and their derivatives.
  • the temperature range is about 550-1200°C, the optimal decomposition temperatures for each of these hydrocarbons falling within this range.
  • natural gas may be used as a mixture of hydrocarbons and the temperature range used is 750-950°C.
  • the formed intermediate body or intermediate powder is a rigid carbonaceous skeleton comprising aluminium carbide particles bonded by the deposited pyrocarbon. The skeleton structure is kept throughout the following process steps, to the final material.
  • a purification step may be included. If the shaped body according to anyone or both of the above embodiments contains carbon bonding the carbide particles (which is the case when pyrocarbon has been applied and when an alternative binder is decomposed to carbon) a pre-treatment purification step is used.
  • porous work piece, or intermediate body or intermediate powder is infiltrated by liquid or gaseous aluminium in vacuum or argon.
  • the carbon in the work piece, or intermediate body or intermediate powder will then react with the aluminium to form aluminium carbide (secondary), thus creating a composition of primary and secondary aluminium carbide with some excess free aluminium.
  • the nanotubes according to the present invention are shorter than many reported nanotubes, and rather barrel-like.
  • the nanotubes are thick with multiple walls, varying between 2 and about 15 layers.
  • the structure of the novel nanotubular carbon consists of intergrown nanotubes, i.e. each nanotube is connected to at least another nanotube.
  • the nanotubes are short and thick tube-like structures, rarely perfectly cylindrical. In other words, there can be some angle between the nanotubes indicating a somewhat polyhedral shape.
  • Typical ranges and sizes in the nanotube structure are inner diameters in the orders of 5.5-27 nm, typically 10-14 nm, outer diameters of about 6-30 nm, typically 14-19 nm, distance between inner and outer diameter 0.7-5 nm, and length of the nanotubes 6-50 nm, typically 14-22 nm.
  • the number of walls is 2-15, typically 5-10.
  • the distance between the walls is about 0.335 nm, which results in the stated total wall thickness of about 0.7-5 nm, and typically of about 1.6-3.4 nm.
  • the inventive method includes possibilities to adapt the shape of the final product by the forming the work pieces and intermediate bodies and machining of those.
  • the final body produced by the described method thus has a predetermined shape and size.
  • the different synthesised carbons have been examined in high resolution transmission electron microscopes (TEM).
  • TEM transmission electron microscopes
  • a large number of nanotubular samples have been studied with TEM, and it is clear that the bulk of the nanotubular material consists of the structure of intergrown nanotubes. In very rare cases onion structures was found, but the extent of these are negligible.
  • Figure 3a shows the edge of a particle of nanotubular carbon from A1 4 C 3 synthesised at 700°C, where short and multiple wall nanotubes lie in different orientations.
  • Figures 3b and 3c show another particle synthesised at 700°C at different magnifications, where the walls of the nanotubes are more clearly seen.
  • the tubes are not isolated from each other, but are normally intergrown, thus forming solid networks with mechanical stability.
  • the exact size and number of walls differ from nanotube to nanotube, but optimising the experimental conditions may produce a more uniform material. It is, for instance, desirable to minimise the possible oxidation during prolonged processing times.
  • chlorination of aluminium carbide is a method for the bulk synthesis of amorphously ordered carbon nanotubes, being a completely unique method and material.
  • A1 C 3 has shown to be the only precursor carbide giving bulk amounts of nanotube-like structures, whereas all other tested carbides gave nanoporous amorphous networks of interconnected carbon channel structures with different bulk densities and pore sizes.
  • Mass yield m pro duct x M A ⁇ c3 / (3 x m A ⁇ c3 x M c ) wherein m denotes the mass and M the molar weight;
  • Purity is estimated from the TEM investigations of a large number of fragments in each of the specimens.
  • An appropriate amount of aluminium carbide is weighed (typically abt. 2 g for laboratory scale), the sample is inserted into a reactor in a furnace, e.g. a quartz-glass reactor tube,
  • the gas flow is switched from Ar to Cl process gas at a stable desired temperature, and the reaction is allowed to proceed during a chosen time (usually 30 - 60 min). 5. After full reaction time, the system is switched back to Ar gas and kept at the reaction temperature for typically one hour to allow the metal chloride to diffuse out of the nanoporous carbon, and a subsequent short thermal treatment at an increased temperature to diffuse all possible residual metal chloride and chloride gas. 6. the furnace temperature is decreased to room temperature, and
  • the resulting material is retrieved from the reactor and examined e.g. by weighing, SEM, XPD, TEM, gas porosimetry, and BET.
  • steps can be supplemented with additional steps, such as pre- treatment, forming of a work piece, deposition of pyrocarbon, and purification, as described above as optional embodiments of the present invention.
  • A1 4 C 3 (Lot. A18K02) from Johnson Matthey GmbH, Alfa Aesar, Germany, at temperatures from 200 to 1200°C was carried out.
  • the purity (assay) of the carbide was 99+% and the average particle size (APS) was 4 micrometers.
  • the chlorine gas with the purity up to 99.8%, argon with an assay 99.998% and carbon dioxide were provided from AGA corporation, Estonia.
  • the chlorine flow was started when the reactor chamber reached the desired temperature.
  • the chlorination time was lh in all experiments.
  • Dechlorination was performed by argon flow at 1000°C for lh. In all experiments reduced argon flow continued until the reactor cooled down to the room temperature.
  • the mass yield, as determined by wheight, of the resulting material retrieved from the carbide was quite close to theoretically estimated maximum carbon values.
  • Table 1 summarizes some characteristics for different nanoporous carbon samples synthesised from A1 C 3 . l i
  • chlorination temperature reveals that the carbon made at below 500°C has a similar, almost amorphous structure.
  • the ⁇ significantly drops and decreases with increasing temperature.
  • Very small ⁇ value (4°) at 900°C corresponds to the structure were almost all carbon mono-layers have been reoriented to form the graphite-like multi-layers. Above 900°C the ⁇ reaches an almost constant value at
  • the obtained material consists of practically pure carbon.
  • the 700 - 800°C samples shows intensive 002 peak in XRD.
  • the surface area ( ⁇ 600m 2 /g) by BET indicates that the carbon consists of a very high percentage of multi-walled nanotube- like structures, which is confirmed by TEM observations.
  • Main difference between 700 and 800°C carbons is that majority of the barrels in first one seems to be whereas these are opened in the latter.
  • Surprisingly low mass yield indicates that at 800°C the C+C1 2 reaction activation energy is reached for the more active amorphous carbon and/or nanotube caps (five-ringed carbon structures).
  • Fig. 6 shows a TEM image of a carbon particle of graphitic-like structure elements chlorinated from A1 4 C 3 at 1100°C.
  • the experiments show that the mass yield is above 70%), and that mass yields above 85%) and even above 90% are reachable. Also, in the samples with nanotubes the purity is usually between 70 and 90 %, reaching a peak for A1 4 C 3 processed at 700°C, as estimated from TEM observations. Lower purity is also achievable. These examples are only illustrative and not limiting.
  • XPD X-ray Powder Diffraction
  • SEM Scanning Electron Microscopy
  • TEM Transmission Electron Microscopy
  • XPD is an X-ray technique performed on powders, and reveals the content of different crystalline phases due to diffraction of the X-rays in the crystals. Each single phase shows up as a unique finger print of the structure, and XPD is therefore of big use in characterisation of solids. Amorphous compounds do not produce sha ⁇ diffraction patterns, why the method is used for the system here to make sure that the samples are devoid of crystalline phases, such as the carbide starting material.
  • Electron microscopy is analogous to normal light microscopy, but can magnify much higher since electrons are used instead of light, and magnetic lenses instead of glass lenses.
  • SEM is the technique used to study the mo ⁇ hology of particles. It is often combined with energy dispersive X-ray analysis (EDX), a method to analyse the X-ray emitted from the sample when it is irradiated with electrons, which gives the content of the different elements present in the sample.
  • EDX energy dispersive X-ray analysis
  • the JEOL 880 instrument used in this study is particularly effective since it has a technology which allows detection of very light elements, such as carbon. This means that it is possible to distinguish between e.g. a particle of Si from one of SiC.
  • the inventive method it is possible to easily produce nanotube like materials e.g. nanotubes on a large batch scale. By this method, high purity and high yield can be reached. It is also possible to control the levels of yield and purity. Furthermore, the present method, besides the advantages presented above, also makes possible the production of bodies of complex shapes - when desired - with minimum machining required. Owing to their high mechanical strength, the bodies according to the invention can be used under conditions demanding retaining of their shape. Refining by means of creating secondary aluminium carbide is possible.
  • the nanotubular carbon material according to the invention can find wide application e.g. for energy storage, for adso ⁇ tion and microdosage of substances, for purification and separation of cryogenic liquids and gas mixtures, etc. because of their advantageous properties, and especially their specific nano-structure.
  • the foregoing description of the invention, with specific embodiments thereof, has been presented for the pu ⁇ ose of illustration and description. The description and examples are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications, embodiments, and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.

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Abstract

L'invention porte sur un carbone nanoporeux de type nanotube, pouvant être produit en grandes quantités, avec un excellent rendement et une excellente pureté et à faible coût, selon un nouveau procédé comprenant l'halogénation du carbure d'aluminium à une température supérieure à 450 °C, de préférence comprise entre environ 500° et 800 °C, et idéalement comprise entre 550° et 750 °C. Le matériau nanotubulaire présente des nanotubes dont les dimensions approchées sont les suivantes : longueur comprise entre environ 6 et 50 nm, généralement entre 14 et 22 nm; diamètre interne compris entre 5.5 et 27 nm, généralement entre 10 et 14 nm; diamètre externe compris entre environ 6 et 30 nm; et épaisseur totale de la paroi comprise entre environ 0.7 et 5 nm, généralement entre 1.6 et 3.4 nm.
PCT/EP2000/008424 1999-08-31 2000-08-29 Procede de production d'un materiau de carbone nanotubulaire et materiau obtenu WO2001016023A1 (fr)

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WO2003029141A1 (fr) * 2001-10-01 2003-04-10 Rosseter Holdings Ltd Nanotubes de carbone courts
US6878361B2 (en) 2001-07-10 2005-04-12 Battelle Memorial Institute Production of stable aqueous dispersions of carbon nanotubes
US6896864B2 (en) 2001-07-10 2005-05-24 Battelle Memorial Institute Spatial localization of dispersed single walled carbon nanotubes into useful structures
EP1977999A1 (fr) * 2007-04-04 2008-10-08 Samsung SDI Co., Ltd. Système hybride de nanotubes de carbone utilisant du carbone dérivé de carbure, son procédé de fabrication, émetteur d'électrons le comprenant, et dispositif émetteur d'électrons doté de l'émetteur d'électrons
WO2007130869A3 (fr) * 2006-05-01 2008-12-31 Yazaki Corp Ensembles organisés de carbone ou non, et leurs méthodes d'obtention
US7591989B2 (en) 2002-05-09 2009-09-22 Institut National De La Recherche Scientifique Method and apparatus for producing single-wall carbon nanotubes
US7744843B2 (en) 2004-06-21 2010-06-29 Drexel University Methods for bulk synthesis of carbon nanotubes
US9576694B2 (en) 2010-09-17 2017-02-21 Drexel University Applications for alliform carbon
US9752932B2 (en) 2010-03-10 2017-09-05 Drexel University Tunable electro-optic filter stack
GB2563207A (en) * 2017-06-02 2018-12-12 Stuart Turner Ltd Liquid transfer device
CN111373249A (zh) * 2017-12-15 2020-07-03 Uxn有限公司 具有纳米多孔结构的胶体以及用于非酶葡萄糖感测的装置和系统
US11751781B2 (en) 2017-11-21 2023-09-12 Uxn Co., Ltd. Glucose-sensing electrode and device with nanoporous layer

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Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6878361B2 (en) 2001-07-10 2005-04-12 Battelle Memorial Institute Production of stable aqueous dispersions of carbon nanotubes
US6896864B2 (en) 2001-07-10 2005-05-24 Battelle Memorial Institute Spatial localization of dispersed single walled carbon nanotubes into useful structures
US7968073B2 (en) 2001-07-10 2011-06-28 Battelle Memorial Institute Stable aqueous dispersions of carbon nanotubes
US7731929B2 (en) 2001-07-10 2010-06-08 Battelle Memorial Institute Spatial localization of dispersed single walled carbon nanotubes into useful structures
US7244408B2 (en) 2001-10-01 2007-07-17 Rosseter Holdings Limited Short carbon nanotubes
WO2003029141A1 (fr) * 2001-10-01 2003-04-10 Rosseter Holdings Ltd Nanotubes de carbone courts
US7591989B2 (en) 2002-05-09 2009-09-22 Institut National De La Recherche Scientifique Method and apparatus for producing single-wall carbon nanotubes
US7744843B2 (en) 2004-06-21 2010-06-29 Drexel University Methods for bulk synthesis of carbon nanotubes
US7938987B2 (en) 2006-05-01 2011-05-10 Yazaki Corporation Organized carbon and non-carbon assembly and methods of making
WO2007130869A3 (fr) * 2006-05-01 2008-12-31 Yazaki Corp Ensembles organisés de carbone ou non, et leurs méthodes d'obtention
EP1977999A1 (fr) * 2007-04-04 2008-10-08 Samsung SDI Co., Ltd. Système hybride de nanotubes de carbone utilisant du carbone dérivé de carbure, son procédé de fabrication, émetteur d'électrons le comprenant, et dispositif émetteur d'électrons doté de l'émetteur d'électrons
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US9752932B2 (en) 2010-03-10 2017-09-05 Drexel University Tunable electro-optic filter stack
US9576694B2 (en) 2010-09-17 2017-02-21 Drexel University Applications for alliform carbon
US10175106B2 (en) 2010-10-29 2019-01-08 Drexel University Tunable electro-optic filter stack
GB2563207A (en) * 2017-06-02 2018-12-12 Stuart Turner Ltd Liquid transfer device
US11751781B2 (en) 2017-11-21 2023-09-12 Uxn Co., Ltd. Glucose-sensing electrode and device with nanoporous layer
CN111373249A (zh) * 2017-12-15 2020-07-03 Uxn有限公司 具有纳米多孔结构的胶体以及用于非酶葡萄糖感测的装置和系统
CN111373249B (zh) * 2017-12-15 2023-04-04 Uxn有限公司 具有纳米多孔结构的胶体以及用于非酶葡萄糖感测的装置和系统

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