EP1198627A1 - Bande de graphite a partir de petrole calcine en mesophase fortement oriente et matiere carbonee en vrac - Google Patents

Bande de graphite a partir de petrole calcine en mesophase fortement oriente et matiere carbonee en vrac

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Publication number
EP1198627A1
EP1198627A1 EP00942193A EP00942193A EP1198627A1 EP 1198627 A1 EP1198627 A1 EP 1198627A1 EP 00942193 A EP00942193 A EP 00942193A EP 00942193 A EP00942193 A EP 00942193A EP 1198627 A1 EP1198627 A1 EP 1198627A1
Authority
EP
European Patent Office
Prior art keywords
tape
mesophase pitch
die
shear rate
carbon
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00942193A
Other languages
German (de)
English (en)
Inventor
Steven Philips Appleyard
Shilin Lu
Brian Rand
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Leeds
Original Assignee
University of Leeds
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GBGB9915346.2A external-priority patent/GB9915346D0/en
Application filed by University of Leeds filed Critical University of Leeds
Publication of EP1198627A1 publication Critical patent/EP1198627A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
    • D01F9/145—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues
    • D01F9/15—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues from coal pitch
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/253—Formation of filaments, threads, or the like with a non-circular cross section; Spinnerette packs therefor
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
    • D01F9/145—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
    • D01F9/145—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues
    • D01F9/155—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues from petroleum pitch

Definitions

  • the present invention relates to a method for producing highly oriented mesophase pitch-based tapes and to a method for producing highly oriented bulk carbon materials from the highly oriented mesophase pitch-based tapes, and to the tapes and the bulk carbon materials per se and to composite materials that contain continuous or discontinuous tapes.
  • the graphite crystal is rendered highly anisotropic by its structure which is composed of stacks of sheet-like layers of carbon atoms (graphene layers) .
  • the carbon atoms are covalently bonded by sp 2 hybridisation of the electron orbitals .
  • These layer planes are weakly held together by weak Van Der aals-type forces.
  • Theoretically graphite has exceptionally high elastic modulus (1060GPa) and it also displays extremely high thermal conductivity along the basal plane (significantly higher than that of most conductive metals such as copper and silver, even higher in specific terms) . It follows that in an article made of perfectly aligned graphene planes, the material would have extremely high tensile elastic modulus in the basal plane directions since the load would be opposed by the covalent bonds themselves .
  • Bulk carbon and graphite materials are produced from carbonaceous filler particles (cokes, graphite or carbon black) combined with a pitch binder.
  • the raw materials are mixed to ensure even distribution of the binder and then formed by extrusion or moulding.
  • the bulk product is calcined and the pitch binder decomposes to carbon.
  • a high temperature of >2500°C is required to convert the carbon to graphite.
  • the graphite bulk density is of the order of -1.7 Mgm "3 with a porosity in the region of -25%.
  • the fabrication process usually requires lengthy, multiple pitch impregnation and pyrolysis cycles to reduce the porosity.
  • Coke particles may show preferred orientation along the extrusion direction which is particularly true if anisotropic or "needle" cokes are used giving an electrode with anisotropic properties.
  • anisotropic or "needle” cokes are used giving an electrode with anisotropic properties.
  • the properties of carbon and graphite materials produced in this way are complicated by the anisotropic nature of the crystallites but (generally speaking) they are porous and of low strength.
  • the bulk anisotropic properties are dependent on the size and arrangement of crystallites within the structure.
  • the cokes used in this process are often produced from petroleum pitches. During pyrolysis most pitches pass through a discotic nematic liquid crystal phase when the polyaromatic molecules align in domains. This is an essential stage in the formation of graphitising carbon from such precursors. It is known as the carbonaceous mesophase and has been exploited to produce advanced carbon and graphite fibres and composites.
  • Carbonaceous mesophase may be formed in complex polycyclic aromatic hydrocarbon mixtures such as petroleum or coal tar pitches when heated within the temperature range 350-500°C [Brooks et al (1965) . Carbon 3, p 185] .
  • mesophase precipitates from the pyrolysing matrix as small spheres.
  • the mesophase layers lie parallel to define the polar diameter but curve to meet the interface with the pitch matrix at a high angle.
  • these mesophase spheres grow and coalesce to larger spheres .
  • Coalesced mesophase spheres show more complicated extinction patterns than the spheres which first appear (see Figure 1) .
  • the coalescence proceeds and eventually the material becomes entirely or substantially converted to the mesophase state.
  • Certain mesophase pitches can be formed into fibres through melt spinning.
  • the mesophase pitch melt is usually extruded through a multiple-hole spinneret.
  • the extrudates are draw down as they cool and eventually solidify to form the fibres.
  • the planar polyaromatic molecules are lined up in the flow direction. The alignment is further improved during the fibre drawdown.
  • the polyaromatic molecules are aligned more or less parallel to the fibre axis in the "as-spun" fibres and thereby producing fibres with exceptional stiffness after carbonisation and graphitisation.
  • the spinning conditions have a strong impact on the degree of preferred orientation of "as-spun" fibres which is higher when the spinning viscosity is low. It has been suggested that mesophase pitch-based fibres of larger diameter produced from lower viscosity precursors have a higher degree of preferred orientation. The fibres of smaller diameter cool more rapidly during the elongation process thereby inheriting a lower degree of preferred orientation as disordered states at higher temperature are locked in.
  • "as-spun" fibres In order to retain the fibre shape and the preferred orientation of mesophase molecules induced during spinning, "as-spun" fibres must be stabilised to render them infusible before further heat treatment. Stabilisation is normally achieved through oxidation in which the "as-spun" fibres are heated in an oxygen-containing atmosphere to temperatures between 200 and 350°C for a period of time sufficient to prevent fibres deforming and/or sticking during carbonisation. The stabilisation step can have a significant impact on the microstructure as well as the mechanical strength of the finished fibres . Two kinds of chemical reactions take place simultaneously during stabilisation. The first is oxygen uptake into the fibre constituents and the second is the evolution of volatile organic vapours and oxygen-containing gases.
  • the weight gain is rapid in the early stages of oxidation but decreases with prolonged exposure.
  • the amount of oxygen uptake is critical. It must be adequate to preclude interfusion of fibres yet low enough not to disrupt the fibre structure when it is eventually expelled as CO and C0 2 during carbonisation.
  • An oxygen uptake of 6 to 7 wt% is known to be adequate for stabilisation.
  • the oxygen absorbed by the fibre forms oxygen-containing functional groups that may cross-link and preserve the axial preferred orientation of the fibre during carbonisation and reduce the solubility of the fibre constituents .
  • Stabilised pitch fibres are infusible. They have poor mechanical properties, are fragile and difficult to handle. Carbonisation of the stabilised fibres is required to convert the molecular solid into a paracrystalline carbon state. Graphitisation at temperatures above 2000°C is a further option and is known to confer exceptional properties. Graphitisation involves the development of graphitic order in the fibres . The highly oriented structure of the "as-spun" fibres is enhanced in the carbonised state provided that they have been sufficiently well oxidised prior to carbonisation. Increasing the final heat treatment temperature brings about an increase in crystallite size and perfection and in the degree of preferred orientation of layer planes along the fibre axis thereby resulting in an improvement in mechanical and other properties.
  • pitch-based carbon fibres produced by BP-Amoco are listed in Table 1 [BP-Amoco data sheet] .
  • these mesophase pitch-based carbon fibres may display a high modulus which is very close to the theoretical value of single crystalline graphite.
  • Carbon fibres may have excellent mechanical and transport properties but only in one direction. For effective use in composites they are combined in woven structures to give two, three and multi-directional properties. The formation of complete woven structures is an additional cost in the production of high performance composites.
  • a carbon-carbon composite is a carbon fibre-reinforced carbon matrix material. Carbon fibres are produced from a variety of precursors including pitch, polyacrylonitrile (PAN), rayon and organic vapours. The carbon matrix phase is typically formed by solid, liquid, or gaseous-phase pyrolysis of an organic precursor material. Carbon-carbon composites seek to combine the high strength, stiffness and toughness of carbon fibre with the excellent thermomechanical properties of bulk polygranular carbons . There are two main methods of formation of the carbon matrix, namely (1) chemical vapour deposition from a hydrocarbon gas (CVD) or (2) carbonisation of a carbonaceous resin or pitch.
  • CVD hydrocarbon gas
  • the very high thermal conductivity of mesophase pitch-based carbon fibres is due to a highly oriented graphite crystalline structure along the fibre axis.
  • the thermal conductivity of the mesophase pitch-based carbon fibre Thornel K-1100 is SJOO-lOOOWm ⁇ K "1 which is more than twice that of copper or 10 times in specific terms.
  • One high profile application of mesophase pitch-based carbon fibre reinforced composites is their use as thermal management materials such as satellite radiators and electronic packagings . Perceived new widespread applications such as heat sinks leads to a need for improved materials and new production methods.
  • Sintered carbons can be made by grinding a mesophase pitch into particles, forming the ground particles into desired shape and finally heating the shaped article to carbonise it.
  • This ground mesophase has to be stabilised to a certain degree or otherwise treated to control its thermoplasticity; too little thermoplasticity and the powder becomes undeformable and yields low green densities, too much thermoplasticity and the powder becomes too fluid and 'bloats' .
  • the intrinsic density of the powder increases progressively with heat treatment through to graphitisation temperatures.
  • the particle shrinkage is due to the decrease in its inter-basal plane spacing (d 002 ) which approaches that of graphite crystal.
  • high strength carbons the shrinkage of the bulk material must be matched by the shrinkage of the particles to avoid the formation of pores.
  • high strength high-density bulk materials can be produced, they still have isotropic properties due to a lack of preferred orientation of the crystallites .
  • Mesophase pitch-based carbon fibres may have different transverse textures which are evident under a scanning electron microscope. Schematic drawings of the transverse textures commonly found in circular mesophase pitch-based carbon fibres are shown in Figure 2. The radial structure is the most commonly found transverse texture. It is believed that the transverse texture is "set in” during the extrusion of mesophase pitch through the spinneret and is preserved by stabilisation.
  • noncircular fibres such as C-shaped, trilobal and rectangular ribbons. The desire to produce non-circular carbon fibres is driven by the readiness for stabilisation of such fibres (compared with round fibres with equivalent cross-sectional area) because non-circular fibres can have shorter oxygen diffusion distance from the surface.
  • Ribbon fibres can be beneficial for making a bidirectional arrangement and are suitable for thermal management applications due to their structure which has high thermal conductivity compared with circular fibres .
  • known ribbon fibres have small transverse areas and the layer structures which allow graphite growth are constrained.
  • Ribbon fibres developed by Edie et al and Mochida et al have small cross-sectional areas.
  • different transverse textures are known for circular mesophase pitch- based carbon fibres (radial, onion-skin, flat-layer, radial- folded and random - see Figure 2) , only line-origin texture has been reported for ribbon fibres.
  • Edie e ⁇ al used slot dies to produce ribbon fibres (see Figure 2) . The largest aspect ratio adopted was 9.
  • the present invention is based on the recognition that when the aspect ratio of the die slot is increased above conventional levels, the molecular orientation in the extruded and drawn tape undergoes a transition that is a function of shear rate.
  • the invention represents an efficient method for producing carbon materials for inter alia thermal management applications and potentially has enormous commercial value .
  • the present invention provides a method for preparing mesophase pitch-based tape comprising: extruding mesophase pitch through a slot shaped die ⁇ eg a rectangular die) with an aspect ratio of 10 or more and drawing at a draw ratio greater than 5.
  • the method of the invention permits preparation of wider tapes (or sheets) having enhanced properties in directions parallel to the plane and over a wider area.
  • Conventional fibre structures may be replaced with tapes (or sheets) of the invention in the manufacture of polymer matrix composites or carbon matrix composites or metal matrix composites .
  • the mesophase pitch-based tape is subjected to an elevated temperature.
  • the mesophase pitch-based tape may be carbonised to carbon tape or graphitised to graphite tape.
  • the mesophase pitch-based tape is stabilised in a stabilisation step ⁇ eg oxidatively stabilised) .
  • stabilisation is followed by heat treatment at an elevated temperature ⁇ eg at a temperature above 400°C) .
  • the aspect ratio of the die is 20 or more, particularly preferably 30 or more, more preferably 40 or more, more especially preferably about 50 or more, even more especially preferably 60 or more, yet even more especially preferably 70 or more (eg about 80) .
  • mesophase pitch-based tape may be produced in which the planar molecules predominantly arrange either parallel to the major tape surface or perpendicular to the major tape surface.
  • a die of aspect ratio greater than 10 a lower shear rate is generally required to produce a tape in which the planar molecules arrange mainly parallel to the major tape surface.
  • a higher shear rate in the die is generally required to produce a tape in which the planar molecules arrange mainly perpendicular to the major tape surface .
  • shear rate as used herein is defined as:
  • the shear rate in the die is in the range 1700 to 33000s “1 .
  • the shear rate in the die is in the range 1700 to 5000s "1 .
  • the shear rate in the die is in the range 5000 to 33000s "1 .
  • a tape in which the planar molecules arrange mainly parallel to the major tape surface may be produced using a shear rate in the range 1900 to 4000s "1 (for example 1961s “1 , 2017s “1 , 2178s “1 , 2338s “1 , 2599s “1 , 2684s “1 , 3150s “1 , 3273s “1 , 3363s “1 or 3830s “1 ) .
  • a tape in which the planar molecules arrange mainly perpendicular to the major tape surface may be produced using a shear rate in the range 5400 to 11100s "1 (for example 5405s “1 , 5463s “1 , 8053s “1 , 8828s “ ⁇ 8881s “1 , 9126s “1 , 9864s “1 , 10953s “1 , 11084s “1 or 32921s “1 ) .
  • a tape in which the planar molecules arrange mainly parallel to the major tape surface may be produced using a shear rate in the range 1700 to 4900s "1 (for example 1758s “1 , 2688s “1 , 3189s “1 or 4828s “1 ) .
  • a tape in which the planar molecules arrange mainly perpendicular to the major tape surface may be produced using a shear rate in the range 6600 to 12600s "1 (for example 6617s "1 , 6991s "1 or 12585s "1 ) .
  • a die with an aspect ratio of 50 has been used to produce highly oriented continuous mesophase pitch- based tapes which have novel flat-layer transverse texture and a cross-sectional area about 100 times greater than conventional mesophase pitch-based carbon fibres.
  • the tape maintains excellent mechanical properties.
  • the tensile strength of the carbonised mesophase pitch-based tape with a cross-sectional area of 5000 ( ⁇ m) 2 is of the order of lGPa. This transverse area is equivalent to that of a circular fibre with a diameter of 80 ⁇ m.
  • Such a circular fibre would take several days to stabilise and once carbonised would only have a tensile strength of the order of 0.2GPa due to the presence of defects.
  • the electrical resistivity of 2700°C heat-treated mesophase pitch-based tape with cross-sectional area -8000 ( ⁇ m) 2 is ⁇ 1.2 ⁇ m. This is equivalent to that of the most thermally conductive known mesophase pitch-based carbon fibres K1100 which have been heat treated to >3000°C. This suggests that the novel mesophase pitch-based tape of the invention may have lower electrical resistivity when heat-treated to >3000°C.
  • the measured electrical resistivity indicates that high thermal conductivity is expected in accordance with Lavin et al , Carbon, 1993, 31, 1001 (see Figure 3).
  • the present invention provides a mesophase pitch-based tape (or sheet) obtainable by extruding mesophase pitch through a slot-shaped die with an aspect ratio of 10 or more, preferably 20 or more, particularly preferably 30 or more, more preferably 40 or more, more especially preferably about 50 or more, even more especially preferably 60 or more, yet even more especially preferably 70 or more ⁇ eg about 80) .
  • the draw ratio should be greater than 5.
  • the mesophase pitch-based tape of the invention can have novel orientation with graphite basal planes parallel to the major surface of the tape. This is beneficial to the development of extended graphitic plane structure.
  • the tape may have two-dimensional graphitic properties due to the extended layer structure.
  • the mesophase pitch-based tape comprises a flat layer transverse texture .
  • the mesophase pitch-based tape comprises graphite basal planes parallel to the major surface of the tape.
  • the mesophase pitch based tape of the invention has an extended planar graphitic structure.
  • the tape is wound to make pipes or bars .
  • the tape is laminated with one or more ceramic materials as interlayers to give oxidation resistance at high temperatures.
  • the tape is formed into a honeycomb structure .
  • the tape or sheet of flat-layer transverse texture is laminated with fibre, ribbon, tape or sheet of line-origin transverse texture or any other material to control the thermomechanical properties, transport properties and resistance to oxidation.
  • the mesophase pitch-based tape is mixed with stabilised tapes from oxidation resistant material [see for example: Lu et al, Journal of Mater Sci , 34, 571-578, 1999] to produce oxidation resistant bulk carbon material .
  • the present invention provides a process for preparing bulk carbon material, said process comprising: processing a mesophase pitch-based tape as hereinbefore defined.
  • the process advantageously comprises the additional step of carbonising to carbonised bulk material or graphitising to graphitised bulk material.
  • the processing step comprises: laminating or pressing the mesophase pitch-based tape.
  • Pressing is preferred and may be conducted at a carefully chosen pressures for a suitable length of time. By controlling the pressure used during pressing, it is possible to produce a range of bulk carbon materials with different thermal and mechanical properties. Typically pressing may be carried out a pressure of about 15-35MPa at an elevated temperature (eg about 400°C) for an extended period of time (eg about 2 hours) .
  • the mesophase pitch-based tapes are stabilised (eg oxidatively stabilised) prior to pressing.
  • the process of the invention produces a high density bulk carbon material without any need for liquid phase impregnation or vapour phase infiltration.
  • the present invention provides a bulk carbon material obtainable by processing a mesophase pitch-based tape as hereinbefore defined.
  • the highly oriented mesophase pitch-based graphite (HOMG) tapes and the bulk HOMG carbon materials have superior properties due to the two-dimensional extensive planar graphitic structure of the tapes and higher density of the final bulk product . Due to the high degree of orientation of the mesophase pitch-based tape, the bulk carbon (eg graphite material) is expected to have excellent transport properties.
  • the bulk carbon materials of the invention can be utilised in the aerospace, nuclear, metallurgical, chemical, mechanical, electronic and electrical industry. In particular, they are best suited in areas where heat generation limits efficiency or leads to component failure such as in high power electronic devices, high energy friction and braking systems, propulsion and energy generation equipment, as well as processing equipment operating in corrosive environments.
  • the low production costs of the method and process of the invention will assist widespread applications in these thermal management areas. Manufacturers will benefit from cheaper production cost and high performance products and user will benefit from improved devices with greater thermal properties and reliability.
  • Figure 1 Schematic illustration of mesophase spheres coalescing to a larger sphere
  • Figure 2 Schematic illustration of the transverse textures of various pitch-based carbon fibres (a) radial (b) onion skin (c) random (d) flat layer (e) line-origin ribbon fibre;
  • Figure 3 Relationship between electrical resistivity and thermal conductivity of mesophase pitch-based carbon fibres
  • Figure 4 A flow diagram representing the route to graphite tape and its bulk material
  • Figure 6 Schematic illustrations of bulk carbon material from tapes and circular fibres .
  • An embodiment of the method of the invention for producing mesophase pitch-based tapes is outlined schematically in Figure 4.
  • a commercial mesophase pitch ARA24 (100% anisotropic content, softening point 237°C) was used to prepare pitch tapes .
  • the spinning precursor was formed into tape by a bench-scale melt-extrusion system at a temperature of 290°C through slit-shaped dies and drawing the extrudate .
  • the molten mesophase pitch was forced through the die by nitrogen gas.
  • Three dies were used with rectangular slot dimensions of 0.14mm x 2.4mm, 0.1mm x 5 mm, and 0.1 mm x 8mm respectively. The depth of the slot is 0.5mm.
  • the tapes Upon exiting the slot dies, the tapes were draw down and collected under ambient conditions on a variable speed winder.
  • the draw ratio is defined as the thickness of the slot (eg 0.14 mm or 0.1 mm) divided by the thickness of the as-spun pitch tape prior to further treatment.
  • the cross-sectional area of the tape was varied with the aspect ratio of the dies, shear rate and winding speed.
  • the mesophase pitch-based tape was produced using a die of aspect ratio 50 at a shear rate of 2338s "1 (spinning temperature 290°C, pressure 8 bar) .
  • the shear rate in the slot die is defined as the product of four times the volume flow rate (cm 3 /sec) divided by the product of ⁇ times the cube of the hydraulic radius (cm) of the slot die.
  • the hydraulic radius of the slot die is defined as the product of two times the cross-sectional area of the slot die (cm 2 ) divided by the perimeter of the slot die (cm) .
  • the as-spun tape was oxidatively stabilised in air or oxygen at a temperature below 300°C producing a weight gain of 8-10% and then carbonised at 1000°C under nitrogen atmosphere. Some carbon tapes were further heat-treated at a higher temperature eg 2700°C.
  • the parallel sheet-like texture of carbon tapes is evident under the optical microscope and scanning electron microscope. This texture has been confirmed by results of X- ray diffraction (XRD) texture scan.
  • the 1000°C heat-treated carbon tape is highly flexible with a transverse area comparable to a combined transverse area of 100-200 conventional mesophase pitch-based carbon fibres.
  • the carbon tape can be coiled into a sample vial with internal diameter of 20 mm.
  • This carbon tape is also strong with a tensile strength of the order of lGPa . After graphitisation at 2700°C, it shows unusual fracture behaviour with evidence of progressive failure and sliding of layers. Together with the highly irregular and fibrillar tensile fracture surface, this indicates that the tape has significant fracture toughness. This is believed to be due to the predominantly planar orientation of the structure combined with limited regions of locally misoriented structure that deflect the crack path and so hinder crack propagation. The ultimate strength was around 2GPa and the initial Young modulus is of the order of 500GPa.
  • the HOMG tape (HTT 2700°C) has an average electrical resistivity of 1.2 ⁇ m equivalent to the value of K1100 that has been heat treated at a much higher temperature (>3000°C) . This suggests that the HOMG tape can have a thermal conductivity value equivalent to K1100 if the inverse relationship between electrical resistivity and thermal conductivity for mesophase pitch-based carbon fibres is still valid for carbon tape (Fig. 3) .
  • the Raman spectrum and XRD profile demonstrate the highly graphitic structure of the HOMG tape.
  • Mesophase pitch was melt extruded from a rectangular die with an aspect ratio of 50 and continuously wound on to carbon felt which was fastened on a roller.
  • the as-spun tapes were oxidatively stabilised and then cut into desired length.
  • the tapes were loaded into a rectangular mould along one direction and compacted under hot press with a ram pressure of 5-10 ton at a temperature of 400°C for 2 hours (see Fig. 6) . These tapes softened under the effect of pressure and temperature and fuse together. However, the preferred orientation induced during extrusion and winding was retained.
  • the bulk material was removed from the mould and heat treated under inert atmosphere to convert it into bulk carbon material .
  • FIG. 6 A schematic diagram of the various materials is shown in Figure 6. After carbonisation, the bulk carbon material from circular fibres cracked into a few pieces . However the bulk carbon material from a tape of the invention maintained integrity with no obvious cracks developed on the surfaces. This is attributable to the circular fibre structural constraints which inhibit shrinkage while the parallel nature of the layer planes in the tapes allows shrinkage and dissipation of such stresses.
  • the advantage of pressing stabilised tapes into desired shape is that the size of bulk materials is not limited by the subsequent stabilisation process as in Amoco' s method. Additionally the tapes may be pressed at higher pressure to achieve higher bulk density of the order of 1.8 Mgm "3 .
  • the bulk carbon material after carbonisation at 1000°C, the bulk carbon material has an apparent density of the order of 1.9 Mgm "3 and the tapes are closely bonded together with little inter- tape porosity.
  • the bulk carbon material has preferred orientation of layer structure parallel to the main bulk carbon surface.
  • the pressure used for formation of the bulk materials must be carefully controlled so as not to destroy the individual tape to ensure high strength of the bulk material .
  • the bulk carbon materials obtained from tapes have higher density than those from circular fibres due to the lower porosity. This leads to a self -reinforced carbon material with two-dimensional ultra-high thermal conductivity at considerably reduced production cost.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Textile Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Mechanical Engineering (AREA)
  • Inorganic Fibers (AREA)

Abstract

L'invention concerne un précédé pour produire des bandes à partir de pétrole calciné en mésophase fortement orienté ainsi que de la matière carbonée fortement orientée en vrac en utilisant des bandes à partir de pétrole calciné en mésophase fortement orienté, le pétrole calciné en mésophase étant extrudé au moyen d'une filière avec un facteur de forme supérieur à 10.
EP00942193A 1999-07-01 2000-07-03 Bande de graphite a partir de petrole calcine en mesophase fortement oriente et matiere carbonee en vrac Withdrawn EP1198627A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
GBGB9915346.2A GB9915346D0 (en) 1999-07-01 1999-07-01 Method
GB9915346 1999-07-01
GB9915857 1999-07-07
GBGB9915857.8A GB9915857D0 (en) 1999-07-01 1999-07-07 Method
PCT/GB2000/002363 WO2001002632A1 (fr) 1999-07-01 2000-07-03 Bande de graphite a partir de petrole calcine en mesophase fortement oriente et matiere carbonee en vrac

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EP1198627A1 true EP1198627A1 (fr) 2002-04-24

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EP (1) EP1198627A1 (fr)
AU (1) AU5690300A (fr)
WO (1) WO2001002632A1 (fr)

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DE102004006588B4 (de) * 2004-02-10 2007-11-15 Sgl Carbon Ag Kontinuierliche Herstellung von Profilen aus Kohlenstoffwerkstoff und so hergestelltes Profil
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