Method for producing an electrically conductive conductor strand with at least one carbon conductor

Abstract

The present invention relates to a method for producing an electrically conductive conductor strand (1) comprising at least one carbon conductor (3), comprising the steps of: producing or providing a conductor strand (1) as an intermediate product comprising at least one carbon conductor (3), which in particular comprises graphite, pyrolytic graphite, graphene, graphine and / or carbon nanotubes, introducing the conductor strand (1) and a plurality of intercalation substances (2), in particular a plurality of different metal chlorides, into a gas phase of a reactor volume (5), wherein the intercalation substances (2) are suitable for intercalation into the material of the at least one carbon conductor (3) of the conductor strand (1), carrying out a heat treatment of the conductor strand (1), in which the reactor volume (5) is brought to a process temperature to initiate an intercalation (100),in which atoms or molecules of the intercalation substances (2) are incorporated in the material of the respective carbon conductor (3), in particular are deposited on a carbon structural form of the carbon conductor (3), in particular in an intermediate region (4) between the layers of a multi-layer carbon structural form, treating the conductor strand (1) after the heat treatment of step c) with an oxidizing agent, in particular alcohol, to oxidize the intercalation substances (2) intercalated into the conductor strand (1), and treating the conductor strand (1) with hydrogen below a predefined reaction temperature to reduce the oxygen content of the oxidized intercalation substances (2), in particular to achieve superconductivity.

Description

Prior ArtThe present invention relates to a method for producing an electrically conductive conductor strand having at least one carbon conductor.Carbon conductors are known from the prior art. For example, the prior art discloses electrical conductors made of graphite, pyrolytic graphite, carbon nanotubes or graphene. DE 10 2020 206 563 A1 discloses the production of an electric graphene conductor. EP 1404908B1 discloses that carbon nanotubes (CNTs) can be dispersed in superacids and thus make it possible to produce continuous fibers from carbon nanotubes. Such electrical conductors are used, for example, in electric motors as shown in WO 2018 / 233897 A1 or WO 2018 / 15803 A1.In order to increase the electrical conductivity of the carbon conductor, it is known to dope the carbon conductor. For example, DE 10 2019 220 177 A1 discloses that graphene can be doped by intrinsically doped graphene. WO 2021 / 004692 A1 shows how graphene can be doped by oxides on transition metals in such a way that the electrical conductivity is increased. EP 0 081 004 B1 shows that the electrical conductivity of graphite is determined by doping with BF 3, SiF 4, HfF 4, TiF 4, ZrF 4, PF 5, NbF 5, TaF 5, AsF 5 or. SbF 5 can be increased.CN 106 744 888 A discloses preparing graphene in a graphene dispersion by addition of aluminum fluoride and amines. From Nakajima, T., Kawaguchi, M., & Watanabe, N. (1981). Ternary intercalation compounds of graphite with aluminum fluoride and fluorine. Journal for Natural Research B, 36(11), 1419-1423, it is also known that aluminum fluoride intercalates into graphite if equimolar fluorine is present in the gas phase and if sufficiently high temperatures are present. A disadvantage is that intercalation requires high temperatures, which leads to the fluorine fluorinating the graphite already from 300° C. and thus degrading the electrical conductivity.EP 0 212 940 A1 shows that metal chlorides are particularly well suited for intercalation doping if they have a low sublimation or boiling point. EP0212940 therefore uses aluminum chloride, which has a low sublimation point at 180° C., to intercalate other metal chlorides, which have a higher sublimation or boiling point, into the graphite more quickly and at lower temperatures.It is likewise disadvantageous according to the prior art that, as described by Matsumoto et al. (Matsumoto, K., Minori, D., Takagi, K., & Hagiwara, R. (2014), Expansion of tetrachloroaluminate-graphite intercalation compound by reaction with anhydrous hydrogen fluoride. Carbon, 67, 434-439), fluorination of graphite intercalated with metal chloride with anhydrous hydrofluoric acid (HF) has the effect that gases are formed in the graphite and the graphite thereby expands. This would similarly also lead to the expansion of the conductors and thus to their destruction.A further possibility for doping is shown in WO 2021 / 128495 A1.Ekin et al. ( Ekin, J.W., Praganski, A.I., Panson, A.J., Janoko, M.A., Capone, D.W., Zaluzec, N.J., ..& Liou, pp. (1987). Evidence for weak link and anisotropic limitations on the transport critical current in bulk polycrystalline Y1Ba 2 Cu 3 O x. Journal of applied physics, 62(12), 4821-4828.) discloses that superconducting phases having a transition temperature of 93 K can be produced in the system YBa 2 Cu 3 O x.Lejay, P., De Rango, P., Sulpice, A., Giordanengo, B., Tournier, R., Retoux, R.,... & Raveau, B. (1989), Conductoritivity up to 110 K in Bi2Sr2Ca2Cu3O10 compounds. Revue de physics application, 24(5), 485-488 show a transition temperature of 110K for the system Bi 2 Sr 2 Ca 2 Cu 3 O 10. These transition temperatures are of industrial interest since the boiling point of nitrogen is 77 K and thus represents a cost-effective cooling fluid for these superconductors compared with noble gases such as helium, for example. In addition, this document shows how a heat treatment under protective gas leads to the formation of a superconducting phase.JP1157456 A2 shows how barium, yttrium and copper are intercalated into graphite. Elemental barium is intercalated and copper and yttrium in the form of their chlorides. After intercalation, the composite is subjected to a heat treatment in an oxygen-containing atmosphere. At this time, graphite is selectively decomposed to CO2and the intercalants are oxidized to form a YbaCuO compound having superconducting properties.Disclosure of the InventionThe method according to the invention makes it possible to increase the electrical conductivity of conductors based on doped, in particular metal chloride-doped, carbon conductors, in particular conductors based on graphene or carbon nanotubes, by treatment with oxygen-containing gaseous oxidants. For this purpose, an intercalated intercalation substance, in particular metal chloride, is converted to the oxide or sulfate, in particular metal oxide or metal sulfate. In this way, intercalation compounds are obtained which are not accessible according to the methods of the prior art.In particular, constituents of a superconducting compound, preferably as metal chlorides, can be introduced into the carbon conductor by intercalation, these constituents being oxidized by means of an oxidizing agent. A superconductor formed in this way is flexible and has a higher current-carrying capacity than superconductors constructed from powders. Furthermore, the superconducting ceramic regions can also be present as islands. It is in particular not necessary to produce these continuously over the entire conductor strand. Rather, the Josphson effect enables the carbon conductor, in particular graphene, to likewise become superconducting in a limited region and thus the individual superconducting islands to connect to form a continuous superconducting conductor. The Josphson effect is described, for example, in the following publication: Borzenets, I. V., Amet, F., Ke, C. T., Draelos, A. W., Wei, M. T., Seredinski, A.,... & Finkelstein, G. (2016), Ballistic graphenee Josephson junctions from the short to the long junction schemes. Physical review letters, 117(23), 23702.The method serves for producing an electrically conductive conductor strand. The conductor strand has at least one carbon conductor. A first step a) takes place for producing or providing a conductor strand as an intermediate product. The conductor strand has at least one carbon conductor which comprises in particular graphite, pyrolytic graphite, graphene, graphin and / or carbon nanotubes.Furthermore, a second step b) takes place for introducing the conductor strand and a plurality of intercalation substances into a gas phase or liquid phase of a reactor volume, wherein each intercalation substance is suitable for intercalation into the material of the at least one carbon conductor of the conductor strand. The intercalation substances are preferably various metal chlorides.A third step c) is then carried out for carrying out a heat treatment of the conductor strand. In the heat treatment, the reactor volume is brought to a process temperature to initiate intercalation. During intercalation, atoms or molecules of the intercalation substance are incorporated into the material of the respective carbon conductor. In particular, said atoms or molecules of the intercalation substance are attached to a carbon structure form of the carbon conductor, in particular in an intermediate region between the layers of a multi-layer carbon structure form.The intercalation substances incorporated into the carbon conductor are oxidized in a further step d), wherein step d) is carried out after the heat treatment of step c) and includes treating the conductor strand with at least one oxidizing agent. The oxidizing agent is in particular alcohol. The intercalation substances intercalated into the conductor strand are thus oxidized, the metal chlorides preferably being converted into metal oxides.Finally, a step e) of treating the conductor strand with hydrogen is carried out under a predefined reaction temperature. This results in a reduction of the oxygen content of the oxidized intercalation substances, in particular to achieve a superconductivity. By this step, the oxygen content can be adjusted preferably to a desired level. This produces in particular water which is discharged. At least one superconducting connection is thus generated in the carbon conductor.The dependent claims show preferred developments of the invention.Preferably, the intercalation substances are a plurality of metal chlorides. The intercalation substances comprise in particular yttrium chloride and / or barium chloride and / or copper chloride and / or bismuth chloride and / or strontium chloride and / or calcium chloride. These metals can preferably achieve a superconducting property.In step b), a mixture of yttrium chloride and barium chloride and copper chloride as intercalation substances is particularly advantageously introduced into the reactor volume. In particular, the ratio YCI is 3: BaCl 2: CuCl 2= 1:2:3. This mixture is in particular the basis for the preparation of a YBa 2 Cu 3 O 7-x complex, said ratio corresponding to the stoichiometric ratio of the metals of this compound. Alternatively, it is provided that a mixture of bismuth chloride, strontium chloride, calcium chloride and copper chloride is introduced into the reactor volume as intercalation substances. The ratio is in particular BiCl 3: SrCl 2: CaCl 2: CuCl 2= 2:2:2:3. This mixture serves in particular as a basis for the preparation of a Bi 2 Sr 2 Ca 2 Cu 3 O 10 complex, said ratio corresponding to the stoichiometric ratio of the metals of this compound.Preferably, the respective metal chlorides of the mixture are mixed for a period of at least 5 hours. The metal chlorides of the mixture are particularly preferably ground for said period of time, in particular by means of a ball mill. The mixing or grinding takes place in particular in a protective gas atmosphere.In step d), the intercalation substances are oxidized. In this case, it is provided that the oxidizing agent absorbs the chlorine of the metal chloride of the intercalated intercalation material and releases oxygen to the metal chloride. The newly formed chloride can be discharged, and the metal oxide remains in the carbon conductor of the conductor strand.In step e), a stoichiometry of YBa 2 CuO 7-x or of Bi 2 Sr 2 Ca 2 Cu 3 O 10 required for superconductivity is preferably set by reducing the oxygen fraction. This is effected in particular by oxygen present reacting to form water which is discharged. This reaction is carried out until the desired oxygen level is reached as described.The heat treatment in step c) is advantageously carried out at a process temperature of 400° C. to 600° C. Alternatively or additionally, it is provided that the heat treatment is preferably carried out over a period of 24 hours. This leads to reliable intercalation of the intercalation substances into the carbon conductor, the basis for a production of a superconductor being achieved.The heat treatment in step c) is advantageously carried out in a chlorine atmosphere. A chlorine gas pressure is preferably at least 2 bar. This allows advantageous intercalation of the intercalation substances from the gas phase.Preferably, in step d) the alcohol is benzyl alcohol. In the oxidation of the intercalation substances, in particular benzyl chloride is formed, which is subsequently discharged. The use of benzyl alcohol leads to reliable oxidation of the metal chlorides of the intercalation substances.The reaction temperature during step e), i.e. during the treatment of the conductor strand with hydrogen, is preferably between 200° C. and 500° C. This ensures optimum reaction of the hydrogen with the oxygen of the metal oxides, wherein the oxygen content is reduced to the desired level with formation of water.Preferably, after step e), a further heat treatment takes place. In this heat treatment, the conductor strand is heated to a specific temperature. The heating is effected in particular under a protective gas atmosphere. The specific temperature is in particular between 400° C. and 900° C. Advantageously, such a heat treatment under inert gas can be used to form a superconducting phase, as was described at the beginning.Brief Description of the DrawingsHereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawing, the following is: FIG. 1 shows a schematic illustration of a conductor strand which can be produced with a method according to an exemplary embodiment of the invention, FIG. 2 shows a schematic cross section through the conductor strand from FIG. 1, which is arranged in a reactor volume, and FIG. 3 shows a schematic illustration of the intercalation during a heat treatment within the scope of the method according to an exemplary embodiment of the invention,Embodiments of the InventionAll the same components, elements and / or units are preferably provided with the same reference numerals in all the figures.To carry out the method according to the invention, at least one conductor strand 1 is provided or produced as an intermediate product in a first step. This conductor strand 1 is a conductor composite, for example a yarn, which is constructed, for example, from a plurality of carbon conductors 3, wherein the carbon conductor 3 can each be a conductor film, a filament or a fiber. Alternatively, however, the carbon conductors 3 can also be yarns or conductor composites with a smaller diameter than the conductor strand 1. The carbon conductors 3 are made of a carbon material such as graphite, pyrolytic graphite, graphene, graphin and / or carbon nanotubes, or compounds based thereon, for example graphene oxide. FIG. 1 schematically shows such a conductor strand 1, which has at least one carbon conductor 3.In a second step of the method, the conductor strand 1 is introduced together with a plurality of intercalation materials 2 into a gas phase or liquid phase of a reactor volume 5 (FIG. 2 ). Each intercalation substance 2 is selected such that they are suitable for intercalation into the material of the at least one carbon conductor 3 of the conductor strand 1.In a third step of the method, a heat treatment of the conductor strand 1 is carried out, in which the reactor volume 5 is brought to a process temperature for initiating an intercalation 4, in which atoms or molecules of the intercalation substances 2 are incorporated into the material of the respective carbon conductor 3, for example are deposited onto a carbon structure shape of the carbon conductor 3, e.g. in the region between the layers of a multi-layer carbon structure shape.FIG. 3 schematically shows a principal sequence of intercalation 100, showing by way of example how intercalation substance 2 intercalates in intermediate layers 4 of the carbon material of the at least one carbon conductor 3 of conductor strand 1, which is formed from graphene in the example. FIG. 3 shows various stages of intercalation 100, in which different amounts of intercalation substance 2 are intercalated into the carbon material of carbon conductor 3.As intercalation substances, for example, bismuth chloride BiCl 3, strontium chloride SrCl 2, calcium chloride CaCl 2 and copper chloride CuCl 2 are placed in the initial charge stoichiometrically corresponding to the ratio of the metals Bi 2 Sr 2 Ca 2 Cu 3 O 10 and are ground together in a ball mill under inert gas for five hours. Alternatively, yttrium chloride, barium chloride and copper chloride can be used stoichiometrically according to the ratio of the metals in YBa 2 CuO 7-x.The metal chloride mixture thus produced is introduced together with the conductor strand 1 into the reactor volume 5 of a chlorreactor. The intercalation 100 of the metal chlorides into the carbon conductor 3 takes place, for example, at a process temperature between 400° C. and 600° C. and a chlorine gas pressure of at least 2 bar over a period of 24 h from the gas phase.In the next step, the metal chlorides are oxidized by the reaction with at least one oxidizing agent, in particular with alcohols. The alcohol herein releases an oxygen atom to the metal chloride and, for this purpose, takes up a chlorine atom. An example of a suitable alcohol is benzyl alcohol. This reacts with metal chlorides to form benzyl chloride with oxidation of the transition metal.The oxygen content is then reduced by a hydrogen treatment at temperatures in the range from 200° C. to 500° C. in such a way that the stoichiometry of Bi 2 Sr 2 Ca 2 Cu 3 O 10( alternatively YBa 2 Cu 3 O 7-x) required for superconductivity, is achieved. A further heat treatment in protective gas is then carried out at temperatures of 400° C. to 900° C., which leads to the formation of the superconducting phase.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2020 206 563 A1

[0002] EP 1404908B1

[0002] WO 2018 / 233897 A1

[0002] WO 2018 / 15803 A1

[0002] DE 10 2019 220 177 A1

[0003] WO 2021 / 004692 A1

[0003] EP 0 081 004 B1

[0003] CN 106 744 888 A

[0004] EP 0 212 940 A1

[0005] EP 0212940

[0005] WO 2021 / 128495 A1

[0007] JP 1157456 A2

[0010] Cited Non-Patent LiteratureNakajima, T., Kawaguchi, M., & Watanabe, N. (1981). Ternary intercalation compounds of graphite with aluminum fluoride and fluorine. Journal for Natural Research B, 36(11), 1419-1423

[0004] Matsumoto, K., Minori, D., Takagi, K., & Hagiwara, R. (2014), Expansion of tetrachloroaluminate-graphite intercalation compound by reaction with anhydrous hydrogen fluoride. Carbon, 67, 434-439

[0006] Ekin, J.W., Praganski, A.I., Panson, A.J., Janoko, M.A., Capone, D.W., Zaluzec, N.J.,... & Liou, pp. (1987). Evidence for weak link and anisotropic limitations on the transport critical current in bulk polycrystalline Y1Ba 2 Cu 3 O x. Journal of applied physics, 62(12), 4821-4828

[0008] Lejay, P., De Rango, P., Sulpice, A., Giordanengo, B., Tournier, R., Retoux, R.,... & Raveau, B. (1989), Conductoritivity up to 110 K in Bi2Sr2Ca2Cu3O10 compounds. Review de physics application, 24(5), 485-488

[0009] Borzenets, I.V., Amet, F., Ke, C.T., Draelos, A.W., Wei, M.T., Seredinski, A.,... & Finkelstein, G. (2016), Ballistic graphene Josephson junctions from the short to the long junction schemes. Physical review letters, 117(23), 23702

[0012]

Claims

Method for producing an electrically conductive conductor strand (1) comprising at least one carbon conductor (3), having the steps: a) producing or providing a conductor strand (1) as an intermediate product comprising at least one carbon conductor (3) which comprises in particular graphite, pyrolytic graphite, graphene, graphin and / or carbon nanotubes, b) introducing the conductor strand (1) and a plurality of intercalation substances (2), in particular a plurality of different metal chlorides, into a gas phase of a reactor volume (5), wherein the intercalation substances (2) are suitable for intercalation into the material of the at least one carbon conductor (3) of the conductor strand (1), c) carrying out a heat treatment of the conductor strand (1), in which the reactor volume (5) is brought to a process temperature for initiating intercalation (100), in which atoms or molecules of the intercalation substances (2) are incorporated into the material of the respective carbon conductor (3), in particular are attached to a carbon structure form of the carbon conductor (3), in particular in an intermediate region (4) between the layers of a multi-layer carbon structure form, d) treating the conductor strand (1) after the heat treatment of step c) with at least one oxidizing agent, in particular alcohol, for oxidizing the intercalation substances (2) intercalated into the conductor strand (1), and e) treating the conductor strand (1) with hydrogen under a predefined reaction temperature, for reducing the oxygen content of the oxidized intercalation substances (2), in particular for achieving a superconduction.Method according to Claim 1, characterized in that the intercalation substances (2) have a plurality of metal chlorides, in particular yttrium chloride and / or barium chloride and / or copper chloride and / or bismuth chloride and / or strontium chloride and / or calcium chloride.Method according to Claim 2, characterized in that in step b) a mixture of yttrium chloride, barium chloride and copper chloride, in particular in the ratio YCI 3: BaCl 2: CuCl 2= 1:2:3, or a mixture of bismuth chloride, strontium chloride, calcium chloride and copper chloride, in particular in the ratio BiCl 3: SrCl 2: CaCl 2: CuCl 2= 2:2:2:3, is introduced into the reactor volume as intercalation substances (2).Method according to Claim 3, characterized in that the respective metal chlorides of the mixture are mixed, in particular ground, for a period of at least 5 hours, in particular in a protective gas atmosphere, in particular by means of a ball mill.Method according to one of Claims 2 to 4, characterized in that, in step d), the oxidizing agent absorbs the chlorine of the metal chloride of the intercalated intercalation substances (2) and releases oxygen to the metal chloride.Method according to one of the preceding claims, characterized in that in step e) a stoichiometry of YBa 2 CuO 7-x or of Bi 2 Sr 2 Ca 2 Cu 3 O 10 required for superconductivity is set by reducing the oxygen fraction.Method according to one of the preceding claims, characterized in that the heat treatment in step c) is carried out at a process temperature of 400°C to 600°C and preferably over a period of 24 hours.Method according to one of the preceding claims, characterized in that the heat treatment in step c) is carried out in a chlorine atmosphere, a chlorine gas pressure preferably being at least 2 bar.The method according to any one of the preceding claims, wherein in step d) the alcohol is benzyl alcohol, wherein benzyl chloride is preferably formed during the oxidation of the intercalation substances.Process according to any one of the preceding claims, characterized in that the reaction temperature during step e) is between 200°C and 500°C.Method according to one of the preceding claims, characterized in that after step e) a heat treatment is carried out, during which the conductor strand (1) is heated, in particular in a protective gas atmosphere, to a specific temperature, in particular between 400°C and 900°C.

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