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CN118062834B - Graphene powder growth method and growth device for loading nanoscale spherical pyrolytic carbon - Google Patents

Graphene powder growth method and growth device for loading nanoscale spherical pyrolytic carbon Download PDF

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Publication number
CN118062834B
CN118062834B CN202410480134.1A CN202410480134A CN118062834B CN 118062834 B CN118062834 B CN 118062834B CN 202410480134 A CN202410480134 A CN 202410480134A CN 118062834 B CN118062834 B CN 118062834B
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inlet pipe
carbon source
molten metal
air inlet
graphene
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CN118062834A (en
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方崇卿
洪江彬
黄卫明
林建斌
刘威
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Xiamen Knano Graphene Technology Corp ltd
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Xiamen Knano Graphene Technology Corp ltd
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    • 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
    • C01B32/182—Graphene
    • C01B32/184—Preparation
    • 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

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  • Condensed Matter Physics & Semiconductors (AREA)
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  • Crystallography & Structural Chemistry (AREA)
  • Composite Materials (AREA)
  • Manufacturing & Machinery (AREA)
  • Carbon And Carbon Compounds (AREA)

Abstract

The application relates to the technical field of carbon materials, in particular to a graphene powder growth method and a graphene powder growth device for loading nanoscale spherical pyrolytic carbon, which comprise a reaction furnace, wherein a reaction container capable of containing molten metal is arranged in the reaction furnace, the reaction container is provided with an air inlet pipe through inlet and a discharge port positioned above the molten metal, the air inlet pipe through inlet is used for passing through a carbon source air inlet pipe capable of extending into the molten metal, and the discharge port is used for communicating with a powder collection device; a cavity is formed between the molten metal and the discharge hole, and the molten metal is heated to a preset reaction temperature; and introducing a mixed gas comprising carbon source gas and auxiliary gas into the molten metal from a carbon source gas inlet pipe so as to form bubbles in the molten metal, wherein in the rising process of the bubbles, the carbon source gas is heated, catalyzed and cracked to partially grow into graphene, and partially rises along with the bubbles to deviate from the molten metal, and at least partially grows into nano spherical pyrolytic carbon loaded on the surface of the graphene in a cavity. The method can remarkably improve the dispersibility of the graphene product.

Description

Graphene powder growth method and growth device for loading nanoscale spherical pyrolytic carbon
Technical Field
The application relates to the technical field of carbon materials, in particular to a graphene powder growth method and a graphene powder growth device for loading nanoscale spherical pyrolytic carbon.
Background
Graphene is widely applied to various fields such as photoelectricity and energy due to excellent electrical and physical and chemical properties, for example, the graphene can be used as a conductive agent to be added into a positive electrode material of an energy battery, such as LiCoO 2、LiMn2O4、LiFePO4 and other positive electrode materials with low conductivity, so that the conductivity of the positive electrode material is improved, the internal resistance of the battery is effectively reduced, the specific capacity of active substances is improved, and the rate capability, the cycle life and the charging rate of the lithium battery are improved. However, in the current preparation process of the graphene-added battery conductive slurry, the graphene powder presents a flaky approximate plane structure in the slurry, and meanwhile, due to the fact that the graphene microchip is very thin, the graphene microchip is very easy to agglomerate under the action of interfacial molecular force, so that the exertion of the high conductivity of the graphene is seriously influenced.
In the related art, researchers in the university of california in the united states published in 2019, 5, paper "CATALYTIC METHANE pyrolysis in molten MnCl 2 -KCl" on APPLIED CATALYSIS, and a mixture molten salt MnCl 2 -KCl was introduced with methane to generate bubbles, and the methane generated by pyrolysis reaction in the molten salt produced carbon powder. Application number 202210528819. X discloses a method for preparing a graphene/carbon black mixture using molten salt by first placing a solid salt in a reaction vessel for dehydration treatment, then heating the solid salt to a molten state and reaching a target temperature, then introducing hydrocarbon gas into the molten salt, and forming hydrocarbon bubbles in the molten solid salt to react the hydrocarbon bubbles in the molten solid salt to produce the graphene/carbon black mixture. However, the technology uses molten salt as a catalyst, the catalytic activity of the catalyst is very poor, the conversion rate of carbon materials generated by hydrocarbon gas pyrolysis reaction is very low (less than or equal to 8%), the quality of grown graphene is very poor, carbon black with poorer conductivity is produced at the same time and mixed into the catalyst in a non-adhering form, the product conductivity is poor, in addition, when the conductive slurry is mixed, the graphene and carbon black particles are easy to separate due to the density difference of the graphene and the carbon black particles, the conductive performance of carbon material powder in the slurry is further seriously influenced, and the application of the carbon material powder in the graphene conductive slurry is limited.
Disclosure of Invention
Aiming at the problems in the prior art, the application provides a graphene powder growth method and a graphene powder growth device for loading nanoscale spherical pyrolytic carbon, which have the following specific technical scheme:
In one aspect, a method for growing graphene powder loaded with nanoscale spherical pyrolytic carbon, the method comprising:
providing a reaction furnace, wherein a reaction container capable of containing molten metal is arranged in the reaction furnace, the reaction container is provided with an air inlet pipe through hole and a discharge hole positioned above the molten metal, the air inlet pipe through hole is used for passing through a carbon source air inlet pipe capable of extending into the molten metal, and the discharge hole is used for communicating with a powder collecting device; a cavity is formed between the molten metal and the discharge hole, and the molten metal is heated to a preset reaction temperature;
Introducing a mixed gas comprising carbon source gas and auxiliary gas into the molten metal from the carbon source gas inlet pipe to form bubbles in the molten metal, wherein the bubbles are heated, catalyzed and cracked to be partially grown into graphene in the rising process, and partially rise along with the bubbles to be separated from the molten metal, and at least partially grow into nano spherical pyrolytic carbon loaded on graphene powder in the cavity to form graphene powder loaded with nano spherical pyrolytic carbon and are collected in the powder collecting device through the discharge hole;
The distance between the air outlet of the carbon source air inlet pipe and the liquid level of the molten metal is a distance which can enable part of non-cracked carbon sources and part of carbon source cracking intermediate products in the bubbles to remain and rise into the cavity; in the reaction vessel, the air pressure in the cavity above the molten metal is micro-positive pressure.
In a possible embodiment, the preset reaction temperature is 1090 ℃ to 1400 ℃.
In a possible embodiment, the preset reaction temperature is 1120 ℃ to 1220 ℃.
In a possible embodiment, the temperature in the cavity above the level of the molten metal is 1050-1150 ℃.
In a possible embodiment, the distance between the air outlet of the carbon source air inlet pipe and the liquid level of the molten metal is 10-15cm.
In a possible embodiment, the distance between the liquid surface of the molten metal and the discharge port is 30cm or more.
In a possible embodiment, the distance between the level of the molten metal and the discharge opening is 30-50cm.
In a possible embodiment, the air pressure in the external space of the reaction vessel in the reaction furnace is normal pressure.
In a possible embodiment, the air pressure in the cavity above the molten metal is 106-115KPa.
In a possible implementation manner, the flow rate of the mixed gas introduced into the carbon source air inlet pipe is 120L/min-180L/min.
In a possible embodiment, the ratio of the flow rates of the auxiliary gas and the carbon source gas forming the mixed gas is 1:0.5-1:1.5.
In a possible implementation manner, the air inlet pressure of the mixed gas in the carbon source air inlet pipe is 0.12-0.18MPa.
In a possible implementation mode, the inner diameter of the exhaust pipe communicated with the discharge port is n times of the inner diameter of the carbon source air inlet pipe, and n is more than 1 and less than or equal to 3.
In a possible implementation mode, the inner diameter of the exhaust pipe communicated with the discharge port is n times of the inner diameter of the carbon source air inlet pipe, and n is more than 1.5 and less than or equal to 2.5.
In a possible embodiment, the carbon source gas inlet pipe has an inner diameter of 7-10mm.
In a possible embodiment, the inner diameter of the exhaust pipe communicated with the discharge port is 15-18mm.
In a possible implementation manner, the exhaust pipe connected with the discharge port is of a double-layer water-cooled structure so as to prevent carbon deposition in the cracking reaction of the exhaust port and cause pipeline blockage.
In a possible embodiment, the reaction vessel comprises a vessel body and a vessel cover which are in sealing connection, the inlet pipe through hole is formed in the vessel cover, and the carbon source inlet pipe is in sealing connection with the inlet pipe through hole.
The carbon source air inlet pipe is connected with the container cover in a sealing way and is introduced after the metal catalyst in the container body forms the molten metal.
In a possible embodiment, the molten metal is copper or an alloy of copper and one or more of iron, nickel, cobalt, gallium, tin, chromium, lead, germanium, antimony, bismuth, silver, and palladium.
In another aspect, a graphene powder growth device loaded with nanoscale spherical pyrolytic carbon is provided, and is applied to the growth method, wherein the device comprises a reaction furnace, a reaction container and a powder collection device:
the reaction furnace is internally provided with a reaction container capable of containing molten metal, the reaction container is provided with an air inlet pipe inlet and a discharge hole positioned above the molten metal, the air inlet pipe inlet is used for passing through a carbon source air inlet pipe capable of extending into the molten metal, and the discharge hole is used for communicating with a powder collecting device; a cavity is formed between the molten metal and the discharge port.
In a possible embodiment, the distance between the air outlet of the carbon source air inlet pipe and the liquid level of the molten metal is 10-15cm.
In a possible implementation mode, the inner diameter of the exhaust pipe communicated with the discharge port is n times of the inner diameter of the carbon source air inlet pipe, and n is more than 1 and less than or equal to 3.
In a possible implementation mode, the inner diameter of the exhaust pipe communicated with the discharge port is n times of the inner diameter of the carbon source air inlet pipe, and n is more than 1.5 and less than or equal to 2.5.
In a possible embodiment, the carbon source gas inlet pipe has an inner diameter of 7-10mm.
In a possible embodiment, the inner diameter of the exhaust pipe communicated with the discharge port is 15-18mm.
In a possible implementation manner, the reaction vessel comprises a vessel body and a vessel cover which are in sealing connection, the air inlet pipe access port is arranged on the vessel cover, and the carbon source air inlet pipe is in sealing connection with the air inlet pipe access port;
after the container cover is in sealing connection with the container body, the carbon source air inlet pipe can be led into the inner cavity of the reaction container from the air inlet pipe inlet.
In a possible embodiment, the container body and the container cover are in threaded sealing connection;
The carbon source air inlet pipe is in threaded sealing connection with the air inlet pipe through inlet.
On the other hand, the graphene powder loaded with the nano-scale spherical pyrolytic carbon is prepared by the graphene powder growth method loaded with the nano-scale spherical pyrolytic carbon.
On the other hand, the application of the graphene powder loaded with the nanoscale spherical pyrolytic carbon in conductive slurry is provided.
Based on the technical scheme, the application has the following beneficial effects:
The technical scheme of the application provides a reaction furnace, wherein a reaction container capable of containing molten metal is arranged in the reaction furnace, the reaction container is provided with an air inlet pipe through hole and a discharge hole positioned above the molten metal, the air inlet pipe through hole is used for passing through a carbon source air inlet pipe capable of extending into the molten metal, and the discharge hole is used for communicating with a powder collecting device; a cavity is formed between the molten metal and the discharge hole, and the molten metal is heated to a preset reaction temperature; introducing a mixed gas comprising carbon source gas and auxiliary gas into the molten metal from a carbon source gas inlet pipe to form bubbles in the molten metal, wherein in the rising process of the bubbles, the carbon source gas is heated, catalyzed and cracked to partially grow into graphene, and part of the graphene rises along with the bubbles to deviate from the molten metal, and at least part of the graphene grows into nano spherical pyrolytic carbon loaded on the graphene in a cavity to form graphene powder loaded with nano spherical pyrolytic carbon and is collected in a powder collecting device through a discharge port, and the distance between the gas outlet of the carbon source gas inlet pipe and the liquid level of the molten metal is a distance which can enable part of non-cracked carbon sources in the bubbles and part of cracked intermediate products of the carbon sources to remain and rise into the cavity; in the reaction vessel, the air pressure in the cavity above the molten metal is micro positive pressure; in this way, the molten metal is used as a heating carrier and a catalyst to realize the growth of high-quality graphene, part of the carbon source gas which is introduced through the control of the reaction distance is catalytically decomposed and then is reserved and lifted to the surface of the liquid metal, and then the reserved hydrocarbon component in the upper Fang Kongqiang grows into nanoscale spherical pyrolytic carbon on the surface of the graphene powder under the catalytic action of the graphene powder which is lifted along with the airflow, and the nanoscale spherical pyrolytic carbon is firmly attached to the high-quality graphene powder, so that the operation is simple, the process is controllable, the quality and the carbon conversion rate of a graphene product are high, the nanoscale spherical pyrolytic carbon loaded on the surface of a graphene microchip is easy to disperse in the preparation process of the slurry, and the graphene powder loaded with the nanoscale spherical pyrolytic carbon is beneficial to obtaining high-performance graphene conductive slurry.
Drawings
In order to more clearly illustrate the technical solution of the present application, the following description will make a brief introduction to the drawings used in the description of the embodiments or the prior art. It is evident that the drawings in the following description are only some embodiments of the present application and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
Fig. 1: the embodiment of the application provides a structural schematic diagram of a graphene powder growth device loaded with nanoscale spherical pyrolytic carbon;
Fig. 2: FIG. 1 is a schematic view of the structure of a carbon source gas inlet pipe extending into molten metal;
fig. 3: an enlarged view of a portion of FIG. 1 defined by dashed line Fang Kuangkuang;
fig. 4: the embodiment of the application provides an SEM image of graphene powder loaded with nanoscale spherical pyrolytic carbon;
fig. 5: the embodiment of the application provides a Raman diagram of graphene powder loaded with nanoscale spherical pyrolytic carbon;
Fig. 6: the embodiment of the application provides another Raman diagram of the graphene powder loaded with the nanoscale spherical pyrolytic carbon;
Fig. 7: the application provides a Raman diagram of graphene powder;
fig. 8: SEM (scanning electron microscope) images of graphene powder provided by comparative examples;
Reference numerals: the device comprises a 1-reaction furnace, a 2-induction heating device, a 3-refractory filler, a 4-base, a 5-reaction container, 6-molten metal, a 7-temperature measuring device, an 8-container cover, a 9-inlet pipe inlet, a 10-exhaust pipe, an 11-exhaust pipe boss, a 12-heat shield, a 13-carbon source inlet pipe, a 14-inlet pipe boss, a 15-first interface, a 16-third interface, a 17-fifth interface, a 18-fourth interface, a 19-second interface, a 20-valve, a 21-powder collecting device, a 22-collector exhaust port, a 23-cavity, a 24-upper boss and a 25-sealing joint.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. All numerical values, whether or not explicitly indicated, are defined herein as modified by the term "about". The term "about" generally refers to a range of values that one of ordinary skill in the art would consider equivalent to the stated value to produce substantially the same properties, functions, results, etc. A range of values indicated by a low value and a high value is defined to include all values included within the range of values and all subranges included within the range of values.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present application and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the application described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion.
The following describes a graphene powder growth device loaded with nano-scale spherical pyrolytic carbon provided by the embodiment of the application, please refer to fig. 1-3, and fig. 1-3 are schematic structural diagrams of a graphene powder growth device loaded with nano-scale spherical pyrolytic carbon. It should be understood that the method structure in the drawings is merely a technical solution of one specific embodiment of the present application, and the method of the present application may include fewer or more structural features, and is not limited to the proposed device structure described in the drawings.
The device comprises a reaction furnace 1, a reaction container 5 and a powder collecting device 21: a reaction vessel 5 capable of containing the molten metal 6 is arranged in the reaction furnace 1, the reaction vessel 5 is provided with an air inlet pipe inlet 9 and a discharge hole positioned above the molten metal 6, the air inlet pipe inlet 9 is used for passing through a carbon source air inlet pipe 13 capable of extending into the molten metal 6, and the discharge hole is used for communicating with a powder collecting device 21; a cavity 23 is present between the molten metal 6 and the tap hole.
Specifically, the reaction furnace 1 is a heating furnace with a heating device, and comprises a furnace cover and a furnace body, wherein the furnace cover and the furnace body are sealed by a sealing piece and are in fastening connection, such as fastening sealing by a sealing gasket and a fastening bolt. The furnace cover and the furnace body of the reaction furnace 1 are also provided with a first interface 15, a second interface 19, a third interface 16 and a fourth interface 18, wherein the first interface 15 is used for introducing a carbon source air inlet pipe 13, the fourth interface 18 is used for communicating a discharge hole of the reaction container 5 and a feed hole of a powder collecting device 21, the third interface 16 is used for communicating an air inlet device, and the fifth interface 17 is used for exhausting air; inert gas is introduced through the third interface 16 and is discharged from the fifth interface 17, so that the gas replacement of the inner cavity of the growth device and the maintenance of the inert environment in the furnace cavity in the reaction process can be realized; the carbon source air inlet pipe 13 is led into through the first interface 15, so that mixed gas can be led in, and the product collection is realized through the communication arrangement of the fourth interface 18; the second port 19 may be in communication with a vacuum pump. Preferably, the reaction furnace 1 may further be provided with a fifth port 17, and the fifth port 17 communicates with the furnace chamber of the reaction furnace 1 and the powder device to introduce inert gas into the powder device at the time of gas replacement.
Preferably, the first interface 15 is provided with an upper boss 24 and a sealing joint 25, and a sealing gasket is arranged between the sealing joint 25 and the upper boss 24; preferably, the sealing joint 25 can be screwed to the first interface 15 of the lid.
The reaction vessel 5 is placed in the cavity of the reaction furnace 1, preferably in the middle position in the lateral direction; preferably, the reaction vessel 5 may be a crucible. The bottom of the reaction vessel 5 is provided with a base 4 for heat insulation.
Specifically, an induction heating device 2 is arranged outside the reaction vessel, the induction heating device 2 is arranged inside the heating furnace, and a refractory filler 3, such as refractory sand, is arranged between the reaction vessel and the induction heating device 2 for heat insulation; the induction heating device 2 is provided with the base 4 at the lower part, and a bottom heat insulating member such as a ceramic plate is arranged between the reaction vessel and the base 4, so that the induction heating device is not only used for heat insulation, but also has excellent compression resistance.
In some embodiments, the material of the reaction vessel 5 may include one or more of graphite, silicon carbide/graphite, and corundum.
Specifically, the reaction vessel 5 includes a vessel body and a vessel cover 8 that are hermetically connected; the container cover 8 is provided with a heat shield 12, preferably a composite ceramic heat shield 12, and the material can comprise silicon dioxide composite ceramic, aluminum oxide composite ceramic, aluminum silicate composite ceramic, silicon carbide composite ceramic or the like. Preferably, a gasket seal is provided at the junction between the container body and the container lid 8.
Specifically, the air inlet pipe inlet 9 is arranged on the container cover 8, and the carbon source air inlet pipe 13 is in sealing connection with the air inlet pipe inlet 9; after the container cover 8 is in sealing connection with the container body, the carbon source air inlet pipe 13 can be led into the inner cavity of the reaction container 5 from the air inlet pipe inlet 9. The carbon source gas inlet pipe 13 can pass through the first interface 15 of the reaction furnace 1 to enter the furnace chamber and pass through the gas inlet pipe inlet 9 on the container cover 8 to be introduced into the inner cavity of the reaction container 5. The carbon source air inlet pipe 13 is a high temperature resistant pipeline, and can be specifically a graphite pipe, a silicon carbide/graphite pipe, a corundum pipe, a carbon-carbon composite material pipe and the like.
Preferably, the container body and the container cover 8 are in threaded sealing connection; the carbon source air inlet pipe 13 is in threaded sealing connection with the air inlet pipe inlet 9. Correspondingly, the air inlet pipe through hole 9 can be a threaded through hole, and the carbon source air inlet pipe 13 is provided with external threads matched with the air inlet pipe through the pipeline in a rotary sealing connection mode so as to improve the sealing performance.
In some embodiments, the carbon source air inlet pipe 13 is further sleeved with an air inlet pipe boss 14, a sealing gasket is arranged on one side of the carbon source air inlet pipe 13 facing the container cover 8, and after the carbon source air inlet pipe 13 is led into the inner cavity of the reaction container 5, the air inlet pipe boss 14 can be abutted with the container cover 8 and seal the air inlet pipe inlet 9. Preferably, the position of the intake pipe boss 14 on the carbon source intake pipe 13 is adjustable.
The carbon source gas inlet pipe 13 can pass through the first interface 15 of the reaction furnace 1 to enter the furnace chamber and pass through the gas inlet pipe inlet 9 on the container cover 8 to be introduced into the inner cavity of the reaction container 5.
Preferably, the first port 15 of the reaction furnace 1 is further provided with a sealing joint 25, and after the carbon source air inlet pipe 13 passes through the first port 15, the sealing joint 25 further seals the connection between the carbon source air inlet pipe 13 and the reaction furnace 1.
Specifically, the carbon source gas inlet pipe 13 is connected to a driving device to drive it to move into and out of the reaction vessel 5.
The discharge port is arranged on the container cover 8 and is communicated with a fourth interface 18 of the reaction furnace 1 through an exhaust pipe 10; preferably, the container cover 8 is connected to the exhaust pipe 10 as a unitary structure.
Preferably, the mouth of the exhaust pipe 10 is also provided with an exhaust pipe boss 11, and a sealing gasket is arranged between the exhaust pipe boss and the top surface of the container cover 8; the upper part of the exhaust pipe 10 is connected with the fourth interface 18 through a metal hose so as to be convenient for connecting the upper part and the fourth interface, and meanwhile, the problem of interface loosening caused by vibration generated during ventilation in liquid metal is avoided, and in addition, the assembly and the separation of the container cover 8 and the reaction container 5 are convenient. The exhaust pipe 10 may be a tungsten pipe or a tungsten steel pipe; the exhaust pipe 10 is of a double-layer water-cooled structure, and a water inlet and a water outlet of the exhaust pipe 10 are connected with a water-cooled circulating interface of the reaction furnace 1 through a metal hose, so that the problems of interface loosening and cooling water leakage caused by vibration generated by ventilation in liquid metal are avoided, and the problem of carbon deposition and blockage of a pipe orifice of the exhaust pipe 10 during reaction in the cavity 23 is also avoided.
A proper amount of metal catalyst is placed in the reaction vessel 5, and is heated and melted to form molten metal 6, and a cavity 23 in the reaction vessel 5 is formed between the liquid surface and the discharge port.
In some embodiments, the growth device is further provided with a temperature measuring device 7, specifically comprising at least one first temperature measuring member and at least one second temperature measuring member, wherein the temperature measuring point of the first temperature measuring member is located in the molten metal 6 to detect the metal temperature, and is preferably located in the middle of the molten metal 6 in the longitudinal direction; the temperature measuring point of the second temperature measuring member is located in the cavity 23 to detect the temperature in the cavity 23, preferably at a longitudinally intermediate position between the level of the molten metal 6 and the discharge opening.
The powder collecting device 21 is provided with a collector exhaust port 22 to realize gas replacement and exhaust gas discharge.
A valve 20 is arranged on the connecting pipeline of the powder collecting device 21 and the reaction furnace 1 so as to facilitate the vacuum pumping of the furnace chamber.
In some embodiments, the powder collecting device 21 includes a powder collecting vessel and a filter, the filter is sealingly connected to an inner wall of the powder collecting vessel, and the filter is located between a feed inlet of the powder collecting device 21 and a collector exhaust port 22, and is used for separating powder from exhaust gas, the exhaust gas is discharged from the collector exhaust port 22 after passing through the filter, and graphene powder cannot pass through the filter and remains in the powder collecting device 21. Specifically, the filter element can be a dust filter and is provided with a back blowing device, and the filter element is tightly fixed with the inner wall of the powder collecting vessel without gaps; the back blowing device is located above the filter piece and is used for blowing away dust attached to the filter to prevent the filter holes from being blocked, the back blowing pressure is 0.3-0.5 MPa, and the back blowing frequency is 1 time/5 s-1 time/10 s.
Preferably, the bottom of the powder collecting vessel is cone-shaped so as to facilitate the discharge of graphene powder.
In the preparation process of graphene powder loaded with nano spherical pyrolytic carbon, a metal catalyst is placed in an inner cavity of a reaction container 5, after a cover and a furnace cover are sealed, vacuumizing is carried out through a second interface 19, and inert gas is introduced through a third interface 16 to replace air in the inner cavities of the whole growth device, including a furnace cavity, the inner cavity of the reaction container 5 and the like; covering the container cover 8 for sealing connection, heating the metal catalyst until the metal catalyst is melted and reaches a preset reaction temperature; then, a carbon source gas inlet pipe 13 is channel-fitted from an inlet pipe inlet 9 on the vessel cover 8 and extends to the bottom of the molten metal 6; and introducing a mixed gas of carbon source gas and auxiliary gas to enable the mixed gas to grow in the liquid metal subsurface and the liquid surface cavity 23, so that the mixed gas grows into graphene loaded with nano spherical pyrolytic carbon, enabling powder to enter a powder collector through a discharge hole along a pipeline, enabling a powder product to be reserved in the powder collecting device 21, and discharging tail gas.
In the embodiment of the application, the distance between the air outlet of the carbon source air inlet pipe 13 and the liquid surface of the molten metal 6 is a distance that can enable part of the uncleaved carbon source in the bubbles and part of the carbon source pyrolysis intermediate product to remain and rise into the cavity 23, so that the carbon source gas is heated in the molten metal 6, part of the carbon source gas is cracked to form graphene, and part of the carbon source gas rises into the cavity 23 along with the bubbles, and the carbon source gas continuously reacts in the cavity to generate nano-scale carbon spheres and is attached to the graphene.
In some embodiments, the distance between the air outlet of the carbon source air inlet pipe 13 and the liquid level of the molten metal 6 is 10-15cm, that is, after the bubbles rise to the liquid level to break, the maximum rising distance of the carbon source lysate without forming graphene is 30-50cm, and graphene powder rising along with the air flow exists in the cavity at the stage, and under the catalysis of the graphene powder, nano spherical pyrolytic carbon grows on the surface of the graphene powder and adheres to the surface of the graphene powder. By setting the distance, it is possible to ensure a sufficient reaction time period to form the supported nano-sized spherical pyrolytic carbon having a suitable quality and size.
In some embodiments, the inner diameter of the exhaust pipe 10 communicated with the discharge port is n times of the inner diameter of the carbon source air inlet pipe 13, and n is more than 1 and less than or equal to 3. Thus, by setting the inner diameter ratio between the air inlet pipe and the air outlet pipe 10, smooth discharge of powder products can be ensured on one hand, and micro-positive pressure setting in the cavity 23 can be realized on the other hand, so that the concentration of hydrocarbon components of a carbon source which is not cracked in molten metal and a part of carbon source cracking intermediate product can be improved, and the growth efficiency of nano-scale spherical pyrolytic carbon on the surface of graphene powder can be improved.
Preferably, the inner diameter of the exhaust pipe 10 communicated with the discharge port is n times of the inner diameter of the carbon source air inlet pipe 13, and n is more than 1.5 and less than or equal to 2.5; through the above preferred range, the micro-positive pressure range is optimized while ensuring smooth discharge of the powder product.
In some embodiments, the carbon source gas inlet pipe 13 has an inner diameter of 7-10mm. In some embodiments, the internal diameter of the vent tube 10 through which the discharge port communicates is 15-18mm. The inner diameter of the air inlet pipe is controlled to be in the range, so that the air flow speed of the mixed gas is conveniently regulated and controlled, and the cracking degree of the carbon source gas in the molten metal, namely the growth efficiency of the graphene powder, is controlled, and the pipe diameter of the air outlet pipe 10 is controlled to be in the range, so that the smooth collection of the powder product is facilitated.
The growth device can controllably grow the graphene powder loaded with the nano spherical pyrolytic carbon, the nano spherical pyrolytic carbon loaded on the surface of the graphene powder in the product is tightly combined with the interface of the carrier graphene, and in the process of rising along with airflow in the cavity, the nano spherical pyrolytic carbon and the carrier graphene can be welded together through carbon atom rearrangement at high temperature due to the high-temperature environment inside the cavity. Experiments prove that the obtained graphene powder loaded with the nano-scale spherical pyrolytic carbon is not easy to fall off when being stirred and mixed after being added into the slurry, and meanwhile, the graphene powder additive loaded with the nano-scale spherical pyrolytic carbon is well dispersed in the slurry, so that aggregation caused by Van der Waals force adsorption can be avoided, and the performance of the conductive slurry is improved.
The following describes the preparation method of graphene powder provided by the embodiment of the present application in conjunction with the above-mentioned growth device, and the present specification provides method operation steps as an example or a flowchart, but may include more or fewer operation steps based on conventional or non-creative labor. The order of steps recited in the embodiments is merely one way of performing the order of steps and does not represent a unique order of execution. In the actual implementation of the preparation method, the method may be performed sequentially or in parallel according to the method shown in the embodiment or the drawings. The method comprises the following steps:
S1, providing a reaction furnace 1, wherein a reaction container 5 capable of containing molten metal 6 is arranged in the reaction furnace 1, the reaction container 5 is provided with an air inlet pipe inlet 9 and a discharge hole positioned above the molten metal 6, the air inlet pipe inlet 9 is used for passing through a carbon source air inlet pipe 13 capable of extending into the molten metal 6, and the discharge hole is used for communicating with a powder collecting device 21; a cavity 23 is arranged between the molten metal 6 and the discharge hole, and the molten metal is heated to a preset reaction temperature;
S2, introducing a mixed gas comprising carbon source gas and auxiliary gas into the molten metal 6 from a carbon source gas inlet pipe 13 to form bubbles in the molten metal 6, heating and catalyzing the carbon source gas to crack the carbon source gas to partially and completely dehydrogenate and grow into graphene in the rising process of the bubbles, rising part of carbon source and hydrocarbon components of a cracking intermediate product along with the bubbles to deviate from the molten metal 6, growing at least part of carbon source and hydrocarbon components into nano spherical pyrolytic carbon loaded on graphene powder in a cavity 23, forming graphene powder loaded with nano spherical pyrolytic carbon, and collecting the graphene powder in a powder collecting device 21 through a discharge hole. In the process, as graphene powder rising along with the airflow exists, part of carbon sources and a pyrolysis intermediate product hydrocarbon component grow into nanoscale spherical pyrolytic carbon on the surface of the graphene powder under the catalysis of the graphene powder and are attached to the surface of the graphene powder.
Specifically, the distance between the gas outlet of the carbon source gas inlet pipe 13 and the liquid surface of the molten metal 6 is such that a part of the non-cracked carbon source and a part of the cracked intermediate product of the carbon source in the bubbles remain and rise into the cavity 23.
Alternatively, the molten metal 6 is copper, or an alloy of copper and one or more of iron, nickel, cobalt, gallium, tin, chromium, lead, germanium, antimony, bismuth, silver, and palladium. The molten metal 6 may also be other metals capable of achieving catalytic cracking of the carbon source gas.
Alternatively, the carbon source gas may be at least one selected from methane, natural gas, ethane, propane, butane, ethylene, propylene, acetylene, liquefied petroleum gas, coalbed methane, biogas. The carbon source gas may also be other substances capable of forming a gas state that can realize the growth of graphene.
Alternatively, the assist gas may include, but is not limited to, at least one of nitrogen, helium, hydrogen, and the like. The inert gas may also be other gases that can act as a growth aid for graphene.
Specifically, a metal catalyst (such as copper or copper alloy) is added into the inner cavity of the reaction vessel 5, and under the protection of inert atmosphere, the induction heating device 2 is started to heat the metal to a molten state and reach a preset reaction temperature, so that the subsequent graphene growth is facilitated. Then, a carbon source air inlet pipe 13 is filled in from an air inlet pipe through hole 9 on the container cover 8 and extends into the bottom of the molten metal 6; the other end of the carbon source air inlet pipe 13 is communicated with an external air passage, and mixed gas is introduced into the molten metal 6 through the carbon source air inlet pipe 13, and the formed bubbles contain carbon source gas and auxiliary gas. In the bubble under the liquid surface, due to the catalysis of interface metal, in the rising process of the bubble in the liquid metal, the carbon source gas is cracked and dehydrogenated, part of the carbon source gas is dehydrogenated and grows into graphene on the surface of the bubble, the rest of hydrocarbon components which are not cracked and not dehydrogenated are risen to the liquid surface of the molten metal 6 along with the bubble, the bubble is cracked and enters into the cavity 23 at the upper part of the liquid surface, and by controlling the temperature and the pressure of the cavity at the upper part of the liquid surface, the graphene powder rising along with the air flow exists in the cavity, the high-concentration hydrocarbon component is cracked on the surface of the graphene powder under the catalysis of the graphene powder, so that the nanoscale spherical pyrolytic carbon loaded on the surface of the graphene powder is formed, and is firmly attached to the high-quality graphene powder, and meanwhile, in the rising process along with the air flow, the structural defect of the nanoscale spherical pyrolytic carbon on the surface of the graphene powder is repaired to a certain extent, so that the graphene powder loaded with the nanoscale spherical pyrolytic carbon with good electric conduction performance is formed.
The graphene powder loaded with the nano spherical pyrolytic carbon rises along with the airflow to enter a discharge port and enters a powder collecting device 21 through a pipeline.
In conclusion, the growth of high-quality graphene is realized by taking the molten metal 6 as a heating carrier and a catalyst, and part of the carbon source gas which is introduced is controlled to be reserved and lifted to the surface of liquid metal after catalytic decomposition, so that hydrocarbon components reserved in the cavity 23 above are grown into nanoscale spherical pyrolytic carbon on the surface of the graphene powder under the catalytic action of the graphene powder rising along with the gas flow, and are firmly attached to the high-quality graphene powder.
It will be appreciated that when the carbon source air inlet pipe 13 is inserted into the molten metal 6, the valve of the pipeline connected with the carbon source air inlet pipe 13 is closed, and the gas introduced into the furnace chamber from the third air inlet 16 is discharged from the clearance between the carbon source air inlet pipe 13 and the hole on the outer wall of the furnace chamber, so that the inert atmosphere environment inside the furnace chamber is ensured in the process, the pressure is micro-positive pressure, and air leakage is avoided. Even if part of the molten metal 6 enters the carbon source air inlet pipe 13, after the valve of the external pipeline is closed, the gas reserved in the pipeline has a certain pressure, the molten metal 6 cannot form back suction, and after the valve of the external pipeline connected with the carbon source air inlet pipe 13 is opened, the molten metal 6 in the pipeline can be blown out by the introduced mixed gas.
In some embodiments, the preset reaction temperature is 1090-1400 ℃, the growth temperature is low, the catalytic cracking reaction of the carbon source gas in the liquid metal can be slowed down, one part of the carbon source gas is completely dehydrogenated to form graphene, and the other part of the uncleaved carbon source gas and the hydrocarbon which is not completely dehydrogenated by pyrolysis react on the surface of the graphene powder to form nano spherical pyrolytic carbon under the catalytic action of the graphene powder rising along with the airflow at the upper part of the liquid surface. Preferably, the preset reaction temperature is 1120-1220 ℃, and experiments prove that the optimal temperature range can ensure the growth quality of graphene and optimize the growth quality of nano-scale spherical pyrolytic carbon.
In some embodiments, the temperature within the upper cavity 23 of the molten metal 6 is 1050-1150 ℃; by controlling the temperature in the cavity 23 to the above range, the carbon source which is not catalytically cracked and the hydrocarbon component of the intermediate product of the carbon source cracking can be made to be on the surface of the graphene powder, and the structural defect can be repaired by rearrangement of carbon atoms, so that the nano-scale spherical pyrolytic carbon with a certain crystallinity can be obtained.
In the embodiment of the application, the distance between the air outlet of the carbon source air inlet pipe 13 and the liquid surface of the molten metal 6 is a distance that can enable part of the uncleaved carbon source in the bubbles and part of the carbon source pyrolysis intermediate product to remain and rise into the cavity 23, so that the carbon source gas is heated in the molten metal 6 to be partially cracked to form graphene, and part of the carbon source gas rises into the cavity 23 along with the bubbles, and the carbon source gas continuously reacts in the cavity to generate nanoscale carbon spheres and is attached to the graphene.
In some embodiments, the distance between the gas outlet of the carbon source gas inlet pipe 13 and the liquid surface of the molten metal 6 is 10-15cm, namely the depth from the liquid surface to the gas outlet is 10-15cm; compared with the preparation process for carrying out complete graphene growth based on liquid metal, the depth is reduced by about 1/2-2/3 height, namely about 1/3-1/2 of the liquid level depth for carrying out complete graphene growth based on liquid metal, and is preferably 1/3. It can be understood that in the rising process of the bubbles formed by introducing the carbon source gas into the molten metal 6, as the pressure is reduced and the heating is continuously carried out, the surface area of the bubbles is increased, namely the growth substrate is gradually enlarged, and the cracking reaction is continuously carried out, the liquid level depth of the application is lower than that of normal graphene growth (only graphene is produced), and the graphene growth in the bubbles in the molten metal 6 is stopped in the middle of the liquid level depth reduction, so as to control the graphene conversion rate of the carbon source gas in the liquid metal, further ensure and regulate the quality of residual hydrocarbon, and regulate the growth amount of nano spherical pyrolytic carbon on the surface of the graphene powder in the cavity.
In some embodiments, the distance between the level of the molten metal 6 and the discharge opening is 30cm or more. Preferably, the distance between the level of the molten metal 6 and the discharge opening is 30-50cm; in this way, the upper cavity 23 is ensured to have enough height so as to be used in the reaction process of growing the nanoscale spherical pyrolytic carbon on the surface of the graphene powder, so that residual hydrocarbon substances have enough nanoscale spherical pyrolytic carbon forming and carbonization time on the surface of the graphene powder under the catalysis of the graphene powder, and the growth of the high-quality graphene powder loaded with the nanoscale spherical pyrolytic carbon is realized.
In some embodiments, the gas pressure in the reaction vessel 5 outside space in the reaction furnace 1 is normal pressure. Thus, the inert environment of the outside and the inner cavity of the reaction vessel 5 is maintained, and the control difficulty of the inert environment maintenance is reduced.
In some embodiments, in the reaction vessel 5, the air pressure in the cavity 23 above the molten metal 6 is slightly positive, so that the pressure above the liquid level is increased, and the catalysis of graphene is weak, so that the pressure above the liquid level is increased, the concentration of hydrocarbon components in the cavity is increased, and the graphene can grow into nano spherical pyrolytic carbon on the surface of graphene powder under the catalysis of graphene powder rising along with the air flow, and is attached to the surface of the graphene powder. It can be understood that after the bubbles are broken, due to the fact that the pressure on the metal liquid surface is higher, the concentration of uncleaved carbon sources and hydrocarbon components which are not completely cracked and dehydrogenated is increased, meanwhile, graphene powder rising along with the air flow exists in the cavity, when the hydrocarbon components in the cavity contact the graphene powder, under the catalysis of the graphene powder, the hydrocarbon components undergo a pyrolysis reaction to form nano spherical pyrolytic carbon loaded on the surface of the graphene powder and firmly adhere to the high-quality graphene powder, and meanwhile, the nano spherical pyrolytic carbon structural defects on the surface of the graphene powder are repaired to a certain extent along with the air flow in the process of rising at the higher liquid surface upper space and temperature, so that the graphene powder loaded with the nano spherical pyrolytic carbon and having good conductivity is formed.
In some embodiments, the air pressure in the cavity 23 above the molten metal 6 is 106-115 kpa, and the pressure at the upper part of the cavity is controlled in this range, so that on one hand, the growth of the nano-scale spherical pyrolytic carbon loaded on the surface of the graphene powder in the cavity 23 can be satisfied, and on the other hand, the influence of the over-high pressure on the stability of the system structural member is avoided.
In some embodiments, the ratio of the flow rates between the assist gas and the carbon source gas forming the mixture is 1:0.5 to 1:1.5. Through setting up higher carbon source gas concentration, can ensure the graphite alkene powder output of unit time under lower growth temperature, to the growth of the spherical pyrolytic carbon of loading on graphite alkene powder surface simultaneously, can ensure that the bubble rises to the liquid surface upper portion and breaks the back, and remaining hydrocarbon component has sufficient concentration.
In some embodiments, the flow rate of the mixture gas introduced into the carbon source gas inlet pipe 13 is 120L/min-180L/min. In this way, the bubbles are allowed to have a suitable rate of rise in the liquid metal to achieve controlled growth of graphene in the molten metal and to be able to maintain pressure control above the metal level to achieve a micro positive pressure environment of the cavity 23.
In some embodiments, the intake pressure of the mixture in the carbon source intake pipe 13 is 0.12-0.18MPa.
Experiments prove that the size of the nano-scale spherical pyrolytic carbon loaded graphene powder prepared by the method is related to the temperature of the cavity 23 above the liquid level, the temperature is too high, and the size of the nano-scale spherical pyrolytic carbon is larger, and conversely, the size of the nano-scale spherical pyrolytic carbon is smaller.
By controlling growth conditions such as the depth of the metal liquid surface from the air outlet, preset reaction temperature, cavity temperature or cavity pressure, the graphene powder conversion rate of carbon source gas in liquid metal, the hydrocarbon substance concentration, reaction efficiency and carbonization degree of nano spherical pyrolytic carbon growth on the surface of the graphene powder can be controlled, and the regulation and control of the size, content and quality of the carbon spheres are further realized.
In some embodiments, the reaction vessel 5 comprises a vessel body and a vessel cover 8 which are in sealing connection, an air inlet pipe inlet 9 is arranged on the vessel cover 8, and a carbon source air inlet pipe 13 is in sealing connection with the air inlet pipe inlet 9; sealing the port between the container cover 8 and the container body, and sealing the connection between the carbon source air inlet pipe 13 and the container cover 8, preferably sealing the connection between the air outlet pipe 10 and the container cover 8. Through the sealing connection, the air pressure control above the liquid level is facilitated.
In some embodiments, the carbon source gas inlet pipe 13 is introduced after the vessel cover 8 is sealingly connected to the vessel body and the metal catalyst in the vessel body forms the molten metal 6. In the embodiment of the application, the carbon source air inlet pipe 13 and the container cover 8 are of a split structure, the container cover 8 is buckled to be in sealing connection with the container body before heating, then when the air in the reaction chamber is replaced, the carbon source air inlet pipe 13 and the container cover 8 are separated so as to facilitate the air discharge and the inert gas inflow in the reaction chamber 5, after the air replacement is completed, the inert gas is introduced from the third air inlet 16, after the metal is heated to be molten, the carbon source air inlet pipe 13 is inserted from the air inlet pipe inlet 9, so that the extending position and depth of the air inlet pipe can be accurately controlled, the air inlet pipe can be accurately positioned at a preset position, and the sealing performance of the inner cavity of the reaction vessel can be ensured.
In some cases, the pressure of the cavity 23 above the liquid level is controlled to be normal pressure, if the carbon source air inlet pipe 13 in the device needs to extend into the inner cavity of the reaction container and then the reaction container 5 and the container cover 8 are buckled, or the carbon source air inlet pipe 13 and the container cover 8 move cooperatively until the molten metal 6 is inserted, the container cover 8 is in unsealed connection with the container body, so that the pressure of the cavity above the liquid level is lower, the concentration of residual hydrocarbon components is lower, and the catalytic activity of graphene powder in the cavity is very weak, so that the residual hydrocarbon components are subjected to pyrolysis reaction in the cavity above the liquid level, therefore, when the pressure of the cavity is normal pressure, the growth or the production efficiency of the nano spherical pyrolytic carbon loaded on the surface of the graphene in the reaction container with the molten metal as a catalyst can not be realized (can be ignored), and finally the performance of the nano spherical pyrolytic carbon loaded on the surface of the graphene as a conductive additive in the conductive slurry is influenced.
In some embodiments, the carbon source gas inlet pipe 13 has an inner diameter of 7-10mm. In some embodiments, the internal diameter of the vent tube 10 through which the discharge port communicates is 15-18mm. By combining the air inlet flow setting, the positive pressure setting of the cavity 23 can be ensured by setting the inner diameter size, so that the cavity 23 at the upper part of the liquid level can obtain higher pressure, the concentration of residual hydrocarbon substances after the bubble is broken is improved, the growth of nano-scale spherical pyrolytic carbon on the surface of graphene powder is facilitated, and meanwhile, the grown graphene powder loaded with nano-scale spherical pyrolytic carbon is smoothly discharged from an exhaust pipeline.
It can be appreciated that the pipe diameter of the exhaust pipe 10 affects the internal pressure of the cavity, and further affects the concentration of hydrocarbon components in the cavity and the growth efficiency and quality of the nano spherical pyrolytic carbon loaded on the surface of the graphene powder. In addition, the pipeline of the exhaust pipe 10 is designed into a double-layer water-cooling structure, so that carbon deposition and blockage of an exhaust pipe orifice during cracking and growing of hydrocarbon substances under higher pressure can be avoided.
The following describes the embodiments of the present application and comparative examples in conjunction with the above-described technical schemes.
Example 1
The embodiment provides a growth method of graphene powder loaded with nanoscale spherical pyrolytic carbon, which specifically comprises the following steps:
1. Adding copper into a crucible, covering a crucible cover and a composite ceramic heat shield 12 in sequence, connecting the crucible cover with a crucible opening in a threaded manner, and arranging a sealing gasket at the contact position of the crucible and the top surface of the crucible opening; the crucible cover and the exhaust pipe 10 are connected into an integrated structure, and a sealing gasket is arranged between the boss 11 of the exhaust pipe and the top surface of the crucible cover; the upper part of the exhaust pipe 10 is connected to a powder collecting device 21 through a metal hose;
2. Under the protection of inert atmosphere, heating metal in a crucible to a melting state and reaching 1200 ℃, wherein the temperature of the upper part of a liquid level is 1100 ℃, the distance between the liquid level and an air outlet is 15cm after melting, then loading a carbon source air inlet pipe 13 from an air inlet pipe inlet 9 on a crucible cover, connecting the carbon source air inlet pipe 13 with the crucible cover in a threaded manner, arranging a sealing gasket between an air inlet pipe boss 14 and the top surface of the crucible cover, and connecting the upper part of the air inlet pipe with an external air passage pipeline; wherein the inner diameter of the vent pipe opening of the carbon source air inlet pipe 13 is 7mm, and the inner diameter of the air outlet pipe 10 is 15mm; the air intake pressure is 0.12MPa (note: a digital display pressure gauge which shows a value of 0 at atmospheric pressure can be used for the test), the digital display pressure gauge shows a negative value when the pressure is lower than the atmospheric pressure, and shows a positive value when the pressure is higher than the atmospheric pressure), and the space pressure in the cavity 23 above the liquid level is 106KPa (note: a digital display pressure gauge which shows a value of 101KPa at the atmospheric pressure can be used);
3. The carbon source gas inlet pipe 13 is used for introducing a mixed gas containing carbon source gas into the crucible, wherein the flow ratio of nitrogen to methane is 1:0.5, the total flow of the mixed gas is 120L/min, the grown graphene powder loaded with the nano-scale spherical pyrolytic carbon enters the powder collecting device 21 through the gas outlet pipe 10, and the graphene powder product loaded with the nano-scale spherical pyrolytic carbon is obtained in the powder collecting device 21.
Fig. 4 is an SEM image of graphene powder loaded with nano-sized spherical pyrolytic carbon, and it can be seen that nano-sized spherical pyrolytic carbon is attached to the surface of the graphene powder; fig. 5 is a raman diagram of graphene positions on the surface of graphene powder loaded with nano-scale spherical pyrolytic carbon, I D/IG is about 0.162, which illustrates that the quality of graphene powder grown in liquid metal is better. Fig. 6 is a raman spectrum of a nano-scale spherical pyrolytic carbon position, I D/IG is approximately equal to 0.714, and meanwhile, a significant 2D peak graphene characteristic signal can be seen, which indicates that structural defects of nano-scale spherical pyrolytic carbon on the surface of graphene powder grown on a metal liquid surface are repaired to a certain extent, so that the graphene powder has a certain crystallinity.
And corroding the grown graphene powder by using an H 2O2/HCl solution (the molar concentration ratio is 2:1) to remove metal impurities, then washing with high-purity water, centrifugally filtering and drying to obtain pure graphene powder loaded with nano-scale spherical pyrolytic carbon, weighing the mass of the graphene powder, calculating the ratio of the graphene powder to carbon atoms in carbon source gas introduced in corresponding time, and calculating to obtain the carbon conversion rate of 92.8%.
Electrochemical performance test: the method comprises the steps of crushing purified graphene powder loaded with nano-scale spherical pyrolytic carbon, and mixing the crushed graphene powder with LiFePO 4, a dispersing agent PVP and a binder PVDF, wherein the mass ratio of LiFePO 4 to the graphene powder loaded with nano-scale spherical pyrolytic carbon to PVP to PVDF is 94.3:3:0.2:2.5, and NMP is used as a solvent to prepare positive electrode slurry, and the dispersion of the graphene powder is good without obvious agglomeration; taking a lithium sheet as a counter electrode, taking a Celgard 2500 polyethylene porous membrane as a diaphragm, taking 1 mol/L LiPF 6/EC-EMC-DMC (volume ratio is 1:1:1) solution as electrolyte to prepare a button cell, and then testing the electrochemical performance of the cell by using a cell testing system to obtain the following test result: the battery impedance is 12 omega, the first discharge specific capacity at 0.2C multiplying power is 228 mAh/g, the first discharge efficiency is 97.6%, the 1C charge-discharge cycle is 150 times, the capacity retention rate is 92%, and the positive electrode slurry has good performance.
Comparative example 1
The embodiment provides a growth method of graphene powder loaded with nanoscale spherical pyrolytic carbon, which specifically comprises the following steps:
1. Adding copper into a crucible, heating metal in the crucible to a molten state under the protection of inert atmosphere, reaching 1200 ℃, enabling the temperature of the upper part of a liquid level to be 1100 ℃, enabling the distance between the liquid level and an air outlet to be 15cm after the metal is melted, and then loading a carbon source air inlet pipe 13 from an air inlet pipe inlet 9 on a crucible cover; wherein the inner diameter of a vent pipe orifice of the carbon source air inlet pipe is 7mm, the inner diameter of a pipe orifice of the air outlet pipe 10 is 45mm, the air inlet pressure is 0.12MPa, and the space pressure in a cavity at the upper part of the liquid level is 103KPa;
2. And introducing a methane-containing mixed gas into the crucible through a carbon source gas inlet pipe, wherein the flow ratio of nitrogen to methane is 1:0.5, the total flow of the mixed gas is 120L/min, and the grown graphene powder loaded with the nano spherical pyrolytic carbon enters a powder collecting device 21 through an exhaust pipe 10, so that a graphene powder product loaded with the nano spherical pyrolytic carbon is obtained in the powder collecting device 21.
The raman diagram of the grown graphene powder product is shown in fig. 7,I D/IG about 0.171, which illustrates that the quality is relatively good, fig. 8 is an SEM image of the grown graphene, no carbon spheres are found, which illustrates that the formation of nano-scale spherical pyrolytic carbon supported on the surface of the graphene powder is related to the pressure of the cavity above the liquid surface, and at lower pressure, the concentration of residual hydrocarbon components in the cavity is lower, and meanwhile, the catalytic activity of the graphene powder rising with the airflow in the cavity is weak, so that the residual hydrocarbon components are subjected to pyrolysis reaction in the cavity above the liquid surface, and therefore, the nano-scale spherical pyrolytic carbon is not observed in the SEM image of the graphene powder in the example.
The grown graphene powder is subjected to corrosion to remove metal impurities by utilizing an H 2O2/HCl solution with the molar concentration ratio of 2:1, then high-purity water is used for cleaning, centrifugal filtration and drying are carried out, so that pure graphene powder loaded with nano-scale spherical pyrolytic carbon is obtained, the mass of the graphene powder is called, the ratio of the graphene powder to carbon atoms in carbon source gas introduced in corresponding time is calculated, and the carbon conversion rate is calculated to be 76%;
As a result of calculating the carbon conversion rate by combining example 1 and comparative example 1, the mass ratio of the nano-scale spherical pyrolytic carbon surface-supported by the graphene powder in example 1 was 19.8%.
Electrochemical performance test: the method comprises the steps of crushing purified graphene powder, mixing the crushed purified graphene powder with LiFePO 4, a dispersing agent PVP and a binder PVDF, wherein the mass ratio of LiFePO 4 to graphene powder to PVP to PVDF is 94.3:3:0.2:2.5, and preparing positive electrode slurry by taking NMP as a solvent; taking a lithium sheet as a counter electrode, taking a Celgard 2500 polyethylene porous membrane as a diaphragm, taking 1mol/L LiPF 6/EC-EMC-DMC (volume ratio is 1:1:1) solution as electrolyte to prepare a button cell, and then testing the electrochemical performance of the cell by using a cell testing system to obtain the following test result: the battery impedance is 38Ω, the first discharge specific capacity at 0.2C multiplying power is 158 mAh/g, the first discharge efficiency is 88%, the 1C charge-discharge cycle is 150 times, the capacity retention rate is 82%, and the performance of the positive electrode slurry is obviously reduced.
The foregoing description has fully disclosed specific embodiments of this application. It should be noted that any modifications to the specific embodiments of the application may be made by those skilled in the art without departing from the scope of the application as defined in the appended claims. Accordingly, the scope of the claims of the present application is not limited to the foregoing detailed description.

Claims (17)

1. A method for growing graphene powder loaded with nanoscale spherical pyrolytic carbon, which is characterized by comprising the following steps:
Providing a reaction furnace (1), wherein a reaction container (5) capable of containing molten metal (6) is arranged in the reaction furnace (1), the reaction container (5) is provided with an air inlet pipe inlet (9) and a discharge hole positioned above the molten metal (6), the air inlet pipe inlet (9) is used for passing through a carbon source air inlet pipe (13) capable of extending into the molten metal (6), and the discharge hole is used for communicating with a powder collecting device (21); a cavity (23) is formed between the molten metal (6) and the discharge hole, and the molten metal (6) is heated to a preset reaction temperature; the preset reaction temperature is 1090-1400 ℃;
Introducing a mixed gas comprising a carbon source gas and an auxiliary gas into the molten metal (6) from the carbon source gas inlet pipe (13) to form bubbles in the molten metal (6), wherein the carbon source gas is heated and catalyzed to be cracked in the rising process to be partially grown into graphene, and the graphene is partially raised along with the bubbles to be separated from the molten metal (6) and at least partially grown into nano spherical pyrolytic carbon loaded on graphene powder in the cavity (23), so as to form graphene powder loaded with the nano spherical pyrolytic carbon and be collected in the powder collecting device (21) through the discharge hole;
The distance between the air outlet of the carbon source air inlet pipe (13) and the liquid level of the molten metal (6) is a distance which can enable part of uncleaved carbon sources and part of carbon source pyrolysis intermediate products in the bubbles to remain and rise into the cavity (23), and the distance between the air outlet of the carbon source air inlet pipe (13) and the liquid level of the molten metal (6) is 1/3-1/2 of the distance which can enable the carbon source gases in the bubbles to grow into graphene; in the reaction vessel (5), the air pressure in the cavity (23) above the molten metal (6) is micro positive pressure, and the air pressure in the cavity (23) above is 106-115KPa.
2. A method according to claim 1, characterized in that the temperature in the upper cavity (23) of the molten metal (6) is 1050-1150 ℃.
3. The method according to claim 1, wherein the method satisfies at least one of the following characteristics:
The distance between the air outlet of the carbon source air inlet pipe (13) and the liquid level of the molten metal (6) is 10 cm to 15cm;
the distance between the liquid surface of the molten metal (6) and the discharge hole is more than 30 cm.
4. The method according to claim 1, wherein the method satisfies at least one of the following characteristics:
the preset reaction temperature is 1120-1220 ℃;
the distance between the liquid level of the molten metal (6) and the discharge hole is 30-50cm.
5. The method according to claim 1, wherein the gas pressure of the external space of the reaction vessel (5) in the reaction furnace (1) is normal pressure.
6. The method according to claim 1, wherein the method satisfies at least one of the following characteristics:
The flow rate of the mixed gas introduced into the carbon source air inlet pipe (13) is 120L/min-180L/min;
The ratio of the flow rates of the auxiliary gas and the carbon source gas forming the mixed gas is 1:0.5-1:1.5;
the air inlet pressure of the mixed gas in the carbon source air inlet pipe (13) is 0.12-0.18MPa;
the inner diameter of the exhaust pipe (10) communicated with the discharge port is n times of the inner diameter of the carbon source air inlet pipe (13), and n is more than 1 and less than or equal to 3.
7. The method according to claim 1, wherein the inner diameter of the exhaust pipe (10) communicated with the discharge port is n times the inner diameter of the carbon source gas inlet pipe (13), and n is more than 1.5 and less than or equal to 2.5.
8. The method according to claim 1, wherein the method satisfies at least one of the following characteristics:
The inner diameter of the carbon source air inlet pipe (13) is 7-10mm;
the inner diameter of the exhaust pipe (10) communicated with the discharge port is 15-18mm.
9. The method according to any one of claims 1 to 8, wherein the reaction vessel (5) comprises a vessel body and a vessel cover (8) which are in sealing connection, the inlet pipe access opening (9) is arranged on the vessel cover (8), and the carbon source inlet pipe (13) is in sealing connection with the inlet pipe access opening (9);
The carbon source air inlet pipe (13) is connected with the container cover (8) in a sealing way, and the metal catalyst in the container body is introduced after forming the molten metal (6).
10. The method according to any one of claims 1-8, characterized in that the molten metal (6) is copper or an alloy of copper with one or more of iron, nickel, cobalt, gallium, tin, chromium, lead, germanium, antimony, bismuth, silver, palladium.
11. A graphene powder growth device loaded with nanoscale spherical pyrolytic carbon, applied to the growth method of any one of claims 1-10, characterized in that the device comprises a reaction furnace (1), a reaction container (5) and a powder collection device (21):
The reaction furnace (1) is internally provided with a reaction container (5) capable of containing molten metal (6), the reaction container (5) is provided with an air inlet pipe through inlet (9) and a discharge hole positioned above the molten metal (6), the air inlet pipe through inlet (9) is used for passing through a carbon source air inlet pipe (13) capable of extending into the molten metal (6), and the discharge hole is used for being communicated with a powder collecting device (21); a cavity (23) is arranged between the molten metal (6) and the discharge hole.
12. The apparatus according to claim 11, characterized in that the distance between the outlet of the carbon source inlet pipe (13) and the level of the molten metal (6) is 10-15cm.
13. The device according to claim 11, wherein the internal diameter of the exhaust pipe (10) communicated with the discharge port is n times the internal diameter of the carbon source air inlet pipe (13), and n is 1 < n.ltoreq.3.
14. The device according to claim 11, wherein the inner diameter of the exhaust pipe (10) communicated with the discharge port is n times the inner diameter of the carbon source air inlet pipe (13), and n is more than 1.5 and less than or equal to 2.5.
15. The apparatus of claim 11, wherein the apparatus satisfies at least one of the following characteristics:
The inner diameter of the carbon source air inlet pipe (13) is 7-10mm;
the inner diameter of the exhaust pipe (10) communicated with the discharge port is 15-18mm.
16. The device according to any one of claims 11-15, wherein the reaction vessel (5) comprises a vessel body and a vessel cover (8) which are in sealing connection, the inlet pipe access opening (9) is arranged on the vessel cover (8), and the carbon source inlet pipe (13) is in sealing connection with the inlet pipe access opening (9);
after the container cover (8) is in sealing connection with the container body, the carbon source air inlet pipe (13) can be led into the inner cavity of the reaction container (5) from the air inlet pipe inlet (9).
17. The device according to claim 16, wherein the container body and the container lid (8) are screw-tightly connected;
the carbon source air inlet pipe (13) is in threaded sealing connection with the air inlet pipe inlet (9).
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