CN114068927B - Graphene carbon nanotube composite material and preparation method thereof - Google Patents

Graphene carbon nanotube composite material and preparation method thereof Download PDF

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CN114068927B
CN114068927B CN202010771678.5A CN202010771678A CN114068927B CN 114068927 B CN114068927 B CN 114068927B CN 202010771678 A CN202010771678 A CN 202010771678A CN 114068927 B CN114068927 B CN 114068927B
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graphene
graphene oxide
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CN114068927A (en
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张锦
孙丹萍
林德武
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Peking University
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Abstract

The invention provides a grapheme carbon nano tube composite material and a preparation method thereof, wherein the preparation method comprises the following steps: granulating the graphene oxide dispersion liquid to remove the solvent to obtain a carrier; the carrier is arranged in the reaction chamber; adjusting the temperature of the reaction chamber to a first temperature, and introducing a metal precursor, wherein the metal precursor is cracked to form metal nano particles on the surface of the carrier, so as to obtain microspheres; and regulating the temperature of the reaction chamber to a second temperature, introducing a carbon source, and performing chemical vapor deposition reaction on the surfaces of the microspheres to grow the carbon nanotubes to obtain the grapheme carbon nanotube composite material. The composite material has a sea urchin-like structure, can be well dispersed in solvents and polymers, can better exert the synergistic effect of graphene and carbon nanotubes, has excellent comprehensive performance, and has good application prospects in the fields of electrochemical energy storage, biological medicine, composite reinforcement and the like.

Description

Graphene carbon nanotube composite material and preparation method thereof
Technical Field
The invention relates to the technical field of carbon material preparation, in particular to a grapheme carbon nano tube composite material and a preparation method thereof.
Background
Ideal Carbon Nanotubes (CNTs) and Graphene (Gr) with the basic structural units consisting of sp 2 The hybridized carbon atoms form a honeycomb six-membered ring structure, and the honeycomb six-membered ring structure has excellent performances in the aspects of electric conduction, heat conduction, mechanical enhancement and the like. Meanwhile, the two materials have great difference in microscopic scale, the carbon nano tube is a one-dimensional quantum material with ultrahigh length-diameter ratio, and the graphene is a two-dimensional plane nano material with ultrahigh diameter-thickness ratio, so that the significant difference exists in performance exertion of electric conduction, heat conduction and mechanical enhancement.
Because of the similarity of the graphene and the carbon nanotube in various performances, the graphene and the carbon nanotube are combined to play a synergistic effect based on the performance difference of the graphene and the carbon nanotube, and the graphene and the carbon nanotube become an effective thought for solving the defects of a single material. For example, as a conductive additive of a lithium ion battery, no matter in the production enterprises of graphene or carbon nanotubes, graphene carbon nanotube composite conductive slurry is developed, and by constructing a multi-dimensional conductive network, the internal resistance is reduced, and the cycle performance and the charge and discharge rate are improved. In the field of polymer compounding, the graphene oxide combination of the carbon nanotube and a graphene derivative material is common, and the functional group on the surface of the graphene oxide is modified to improve the combination force of the carbon material and a polymer matrix, improve the dispersion of the carbon nanotube and better exert the earth force, the electricity and the heat property of the carbon nanotube. Therefore, the graphene and carbon nano tube composite play a synergistic effect, and are widely focused on the application fields of nano carbon material preparation, electrochemical energy storage, biological medicine, composite enhancement and the like.
The graphene and carbon nanotube composites can be respectively divided into two main categories according to a composite mode: the graphene and the carbon nano tube are combined together mainly through conjugation under non-covalent action such as physical mixing, and are mutually crossed and fixed to form a disordered and intricate interpenetrating network; the other is covalent interaction, i.e. graphene and carbon nanotubes share common atoms, such as chemical vapor deposition in situ synthesis.
Physical mixing generally opens the respective agglomeration structures of graphene and carbon nanotubes in a liquid phase through extremely strong mechanical action, so that not only is the process energy consumed, but also a large amount of solvent directly increases the raw material cost and the environmental cost, and the addition of the surfactant influences the product purity and simultaneously reduces the performance (CN 110808375A). In addition, the simple and extensive treatment process inevitably damages the original structure of graphene or carbon nano tubes, reduces the sheet diameter, shortens the tube length and the like.
The chemical vapor deposition direct synthesis can effectively avoid or reduce the problems by a bottom-up assembly mode, but the precise control of the structure control and the compound proportion of the two is always a technical problem which needs to be overcome in the method (such as Chinese patent applications CN110228805A, CN108069420A, CN106629672A and CN 110371956A).
Therefore, a new graphene carbon nanotube composite material and a preparation method thereof are needed to solve various problems in the prior art.
It is noted that the information disclosed in the foregoing background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.
Disclosure of Invention
The invention aims to overcome at least one defect of the prior art, and provides a grapheme carbon nano tube composite material and a preparation method thereof, so as to solve the problems of complex preparation process, high cost and low product quality of the grapheme carbon nano tube composite material.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the invention provides a preparation method of a grapheme carbon nano tube composite material, which comprises the following steps: granulating the graphene oxide dispersion liquid to remove the solvent to obtain a carrier; the carrier is arranged in the reaction chamber; adjusting the temperature of the reaction chamber to a first temperature, and introducing a metal precursor, wherein the metal precursor is cracked to form metal nano particles on the surface of the carrier, so as to obtain microspheres; and regulating the temperature of the reaction chamber to a second temperature, introducing a carbon source, and performing chemical vapor deposition reaction on the surfaces of the microspheres to grow the carbon nanotubes to obtain the grapheme carbon nanotube composite material.
According to one embodiment of the invention, the graphene oxide dispersion liquid is a graphene oxide dispersion liquid with conductive particles intercalated, the conductive particles account for 1% -30% of the total mass of the graphene oxide and the conductive particles, and the conductive particles are selected from one or more of carbon black, ketjen black, onion carbon and fullerene.
According to one embodiment of the invention, the first temperature is 100 ℃ to 700 ℃ and the second temperature is 600 ℃ to 700 ℃.
According to one embodiment of the invention, the metal precursor is selected from one or more of metal carbonyls, metallocene compounds selected from one or more of iron pentacarbonyl, iron dicarbonyl, iron tricyclocarbonyl, nickel tetracarbonyl, chromium hexacarbonyl, cobalt octacarbonyl and ferrocene.
According to one embodiment of the invention, after the carrier is placed in the reaction chamber, an inert carrier gas is introduced to suspend the carrier in the reaction chamber; wherein the inert carrier gas is selected from one or more of nitrogen, argon, krypton and xenon, and the flow rate of the inert carrier gas is 300-1000 sccm.
According to one embodiment of the invention, the carbon source is selected from one or more of hydrocarbons, alcohols, ethers, ketones, phenols and carbon monoxide; the time for introducing the carbon source is 1 min-60 min.
The invention also provides a graphene carbon nanotube composite material, which has a sea-urchin-like structure and comprises graphene microspheres and a plurality of carbon nanotubes formed on the surfaces of the graphene microspheres, wherein the graphene microspheres are formed by aggregating carbon sheets formed by reducing graphene oxide in multiple layers.
According to one embodiment of the invention, the graphene microsphere is internally provided with a nano pore canal, the particle size of the graphene microsphere is 0.1-100 μm, and the carbon sheet comprises 1-10 layers of reduced graphene oxide.
According to one embodiment of the invention, the reduced graphene oxide is a reduced graphene oxide with conductive particles intercalated.
According to one embodiment of the present invention, the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes, the diameter of the carbon nanotubes is 0.1nm to 15nm, and the length of the carbon nanotubes is 10nm to 30 μm.
According to the technical scheme, the beneficial effects of the invention are as follows:
the invention provides a graphene carbon nanotube composite material and a preparation method thereof, wherein graphene microspheres are constructed to serve as a growth template of carbon nanotubes, so that the graphene carbon nanotube composite material with a sea urchin-like structure is obtained, and the graphene microspheres serve as fulcrums for the growth of the carbon nanotubes, so that the entanglement of the carbon nanotubes can be prevented, and a stable mechanical supporting effect can be provided. The composite material can be well dispersed in a solvent and a polymer under the condition of no need of adding a surfactant, forms long-range and short-range carbon staggered structures with different dimensions, and better plays the synergistic effect of the two. The graphene carbon nanotube composite material prepared by the method has excellent comprehensive performance and has good application prospects in the fields of electrochemical energy storage, biological medicine, composite reinforcement and the like.
Drawings
The following drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the description serve to explain the invention, without limitation to the invention.
FIG. 1 is a flow chart of a process for preparing a grapheme carbon nanotube composite according to one embodiment of the present invention;
FIG. 2 is a schematic diagram of a fluidized bed chemical vapor deposition apparatus for preparing grapheme carbon nanotube composites;
FIG. 3 is a scanning electron microscope image of the grapheme carbon nanotube composite of example 1;
FIGS. 4a and 4b are transmission electron microscopy images of the grapheme carbon nanotube composite of example 1, respectively;
FIG. 5 is a transmission electron microscopy image of the catalyst nanoparticle formed in example 1;
FIG. 6 is a statistical distribution plot of the particle size of the catalyst nanoparticles formed in example 1;
FIG. 7 is a transmission electron microscopy image of the catalyst nanoparticle formed in example 2;
FIG. 8 is a statistical distribution plot of the particle size of the catalyst nanoparticles formed in example 2;
FIG. 9 is a transmission electron microscopy image of the catalyst nanoparticle formed in example 3;
FIG. 10 is a statistical distribution plot of the particle size of the catalyst nanoparticles formed in example 3;
FIG. 11 is a transmission electron microscopy image of the grapheme carbon nanotube composite of example 3;
FIG. 12 is a transmission electron microscopy image of the grapheme carbon nanotube composite of example 4;
FIG. 13 is a high resolution transmission electron microscope image of a thin layer region on a carbon support microsphere of preparation example 1;
FIG. 14 is a high resolution transmission electron microscope image of a thin layer region on a microsphere after annealing to simulate the growth conditions of a carbon nanotube according to example 6;
FIG. 15 is an X-ray photoelectron spectrum of the carbon support microsphere of preparation example 1;
FIG. 16 is an X-ray photoelectron spectrum of microspheres of example 6 after annealing to simulate carbon nanotube growth conditions.
Wherein, the reference numerals are as follows:
100: quartz tube
200: bubbling tank
300: porous screen plate
400: carrier body
Detailed Description
The following provides various embodiments or examples to enable those skilled in the art to practice the invention as described herein. These are, of course, merely examples and are not intended to limit the invention from that described. The endpoints of the ranges and any values disclosed in the present invention are not limited to the precise range or value, and the range or value should be understood to include values close to the range or value. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and should be considered as specifically disclosed herein.
Fig. 1 shows a process flow diagram of a preparation process of a grapheme carbon nanotube composite material according to an embodiment of the present invention, and as shown in fig. 1, a preparation method of a grapheme carbon nanotube composite material according to the present invention includes: granulating the graphene oxide dispersion liquid to remove the solvent to obtain a carrier; the carrier is arranged in the reaction chamber; adjusting the temperature of the reaction chamber to a first temperature, and introducing a metal precursor, wherein the metal precursor is cracked to form metal nano particles on the surface of the carrier, so as to obtain microspheres; and regulating the temperature of the reaction chamber to a second temperature, introducing a carbon source, and performing chemical vapor deposition reaction on the surfaces of the microspheres to grow the carbon nanotubes to obtain the grapheme carbon nanotube composite material.
According to the invention, the composite of the carbon nano tube and the graphene can exert synergistic effect, and the defect of a single material is overcome. However, the existing compound mode has the problems of complex preparation process, high cost, difficult control of product quality and the like, so that the application of the compound mode has great limitation. The inventor of the invention discovers that graphene microspheres can be used as a growth template of carbon nanotubes to prepare a graphene carbon nanotube composite material with a special assembly structure, and the composite material can be well dispersed in a solvent and a polymer under the condition of no need of adding a surfactant to form a carbon staggered structure with different dimensions and long and short ranges, so that the synergistic effect of the graphene carbon nanotube composite material and the carbon nanotube composite material can be better exerted.
Specifically, for the preparation of carbon nanotubes, the particle size of the catalyst is a key factor for controlling the diameter of the carbon nanotubes, and the particle size and distribution of the catalyst are determined by the quality of the catalyst carrier. Therefore, the graphene carbon nanotube composite material with the sea urchin-like structure can be obtained by constructing a proper catalyst carbon carrier, namely, a spherical material formed by gathering carbon sheets formed by multiple layers of graphene oxide, depositing catalyst metal nano particles on the surface of the spherical carrier by adopting a specific process, enabling the obtained catalyst to have proper particle size and distribution, and growing carbon nanotubes by chemical vapor deposition on the basis. According to the preparation method disclosed by the invention, the structure of the obtained carbon nano tube can be controlled according to actual needs by adjusting the technological parameters of the growth process, and meanwhile, graphene oxide is reduced in the process of growing the carbon nano tube to generate the reduced graphene oxide microsphere with surface defects, so that the overall conductivity of the composite material can be ensured, and meanwhile, the dispersion of the catalyst metal nano particles is facilitated. In a word, the graphene carbon nano tube composite material with excellent comprehensive performance can be prepared by the method, and the graphene carbon nano tube composite material has good application prospects in the fields of electrochemical energy storage, biological medicine, composite enhancement and the like.
The preparation process of the graphene carbon nanotube composite material of the present invention is specifically described below with reference to fig. 1.
Firstly, providing a graphene oxide dispersion liquid, and granulating the graphene oxide dispersion liquid to remove a solvent to obtain a carrier.
The graphene oxide may be a graphene oxide powder or a filter cake, or a graphene oxide pre-dispersion liquid that has been dispersed to some extent in advance. Dispersing the graphene oxide in a solvent such as water, aromatic solvent, or a solvent having no more than 3 (n) C And.ltoreq.3) low molecular alcohol solvents, such as ethanol, propanol, etc. The concentration of the graphene oxide dispersion liquid is 0.05 mg/mL-40 mg/mL, for example, 0.05mg/mL, 0.1mg/mL, 1mg/mL, 10mg/mL, 15mg/mL, 20mg/mL, 30mg/mL, and the like. To better disperse the graphene oxide, the solvent may also include an appropriate amount of a surfactant, including, but not limited to, one or more of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone, sodium lignin sulfonate, polyvinyl alcohol, polydimethylsiloxane, gamma- (2, 3-glycidoxy) propyltrimethoxysilane (KH-560) and gamma-aminopropyl triethoxysilane (KH-550).
In some embodiments, the graphene oxide dispersion of the present invention may also be a graphene oxide dispersion in which conductive particles are intercalated. The intercalation technology of the conductive particles can ensure that the dispersion liquid can still maintain a higher specific surface after the solvent is removed, and the collapse and the damage of the structure caused by agglomeration are avoided. On the basis, the solvent is continuously removed by granulation, so that the dried material forms a similar ball structure with folds on the macro scale while the micro scale is not agglomerated, the active surface which can be loaded by the catalyst is further exposed and fixed, and the efficiency and the quality of the catalyst loading are improved.
Specifically, the preparation method of the graphene oxide dispersion liquid with the conductive particle intercalated comprises the following steps: and adding the conductive particle dispersion liquid into the graphene oxide dispersion liquid, and then fully mixing to obtain the graphene oxide dispersion liquid with the conductive particle intercalation.
The conductive particles are selected from one or more of carbon black, ketjen black, onion carbon, and fullerenes. The aforementioned conductive particle dispersion liquid can be obtained by mixing and dispersing it in a solvent which is soluble in a certain proportion. Wherein the solvent is selected from water, aromatic solvents, and solvents having no more than 3 (n) C And.ltoreq.3) low molecular alcohol solvents, such as ethanol, propanol, etc. The conductive particles account for the total of the graphene oxide and the conductive particles1% -30% by mass, for example, 1%, 5%, 10%, 15%, 20%, 30% by mass, etc. Likewise, suitable amounts of surfactants may also be added to the conductive particle dispersion, including, but not limited to, one or more of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone, sodium lignosulfonate, polyvinyl alcohol, polydimethylsiloxane, gamma- (2, 3-glycidoxy) propyltrimethoxysilane (KH-560) and gamma-aminopropyl triethoxysilane (KH-550).
In some embodiments, the foregoing dispersion of graphene oxide and dispersion of conductive particles may be performed by a dispersing device such as ultrasonic dispersion, a high-speed dispersing disc, or an emulsifying machine. Further, the manner in which the graphene oxide dispersion liquid and the conductive particle dispersion liquid are sufficiently mixed includes using a homogenizing treatment and/or a grinding treatment, and the mixing apparatus may be a homogenizer, a centrifugal mill, or a combination thereof, to which the present invention is not limited. During the homogenization treatment, the pressure of the homogenization treatment is generally 1000bar to 1200bar, for example, 1000bar, 1100bar, 1150bar, 1180bar, 1200bar, etc., and the flow rate is 0.1mL/s to 5mL/s, for example, 0.1mL/s, 0.8mL/s, 1mL/s, 2mL/s, 2.5mL/s, 3mL/s, etc., and the treatment time is 20min to 60min, for example, 20min, 30min, 50min, 55min, 60min, etc. And mixing to obtain graphene oxide dispersion liquid with conducting particles intercalated, and granulating to remove the solvent to obtain the carrier.
Preferably, the desolventizing is performed by a spray drying technique, which can macroscopically make the material take on a spheroid or sphere-like structure with folds while ensuring that the material is microscopically not agglomerated, and further exposes and fixes the active surface that the catalyst can support. In some embodiments, the aforementioned spray drying process pressure is 0.1MPa to 0.5MPa, e.g., 0.1MPa, 0.3MPa, 0.4MPa, 0.5MPa, etc., the process flow rate is 800mL/h to 1500mL/h, e.g., 800mL/h, 900mL/h, 1000mL/h, 1200mL/h, 1500mL/h, etc., and the process temperature is 120 ℃ to 200 ℃, e.g., 120 ℃, 130 ℃, 150 ℃, 180 ℃, etc. Because the drying temperature is low, most oxygen-containing groups of the material are reserved, a large number of active sites are provided for capturing the catalyst, and the efficiency and the quality of the catalyst loading are further improved.
The support obtained in the foregoing is then placed in a reaction chamber, i.e. a tube furnace in a chemical vapor deposition apparatus. Generally, in order to stably suspend the carrier material in the reaction chamber, an inert carrier gas is also required to be introduced; wherein the inert carrier gas is selected from one or more of nitrogen, argon, krypton and xenon, and the flow rate of the inert carrier gas is 300 sccm-1000 sccm, for example, 300sccm, 350sccm, 400sccm, 500sccm, 600sccm, 780sccm, 900sccm, etc.
Further, the temperature of the reaction chamber is regulated to a first temperature, a metal precursor is introduced, and the metal precursor is cracked to form metal nano particles on the surface of the carrier, so that the microsphere is obtained.
Wherein the first temperature is 100 ℃ to 700 ℃, for example, 100 ℃, 200 ℃, 250 ℃,300 ℃, 400 ℃, 450 ℃, 470 ℃, 500 ℃, 560 ℃ and the like, and the cracking temperature of the metal precursor affects the particle size of the obtained metal nanoparticles. Wherein, the higher the cracking temperature is, the larger the particle diameter is, and the larger the diameter of the catalyzed carbon nano tube is. Therefore, the pipe diameter of the carbon nano-tube can be regulated and controlled by regulating and controlling the cracking temperature of the metal precursor, so that the proper and required pipe diameter is obtained.
In some embodiments, the foregoing metal precursor may be one or more of a metal carbonyl compound, a metallocene compound selected from one or more of iron pentacarbonyl, iron nonacarbonyl, iron dodecacarbonyl, nickel tetracarbonyl, chromium hexacarbonyl, cobalt octacarbonyl, and ferrocene. The metal catalyst precursor can be a gaseous compound, a liquid compound or a solid compound, wherein when the metal catalyst precursor is a liquid compound, the metal catalyst precursor can be introduced into the reaction chamber after bubbling or volatilizing by inert gas. When the metal catalyst precursor is a solid compound, the metal catalyst precursor can be directly placed into the reaction chamber or volatilized and then introduced into the reaction chamber. The formed metal nano particles are composed of corresponding metal after the metal catalyst precursor is cracked.
Finally, regulating the temperature of the reaction chamber to a second temperature, introducing a carbon source, and performing chemical vapor deposition reaction on the surface of the microsphere to grow the carbon nanotube, thereby obtaining the graphene carbon nanotube composite material.
Wherein the second temperature is 600 ℃ to 700 ℃, for example 600 ℃, 620 ℃, 650 ℃, 680 ℃, 690 ℃, and the like. The carbon source may be one or more of hydrocarbons, alcohols, ethers, ketones, phenols, and carbon monoxide. The carbon source may be a gaseous carbon source, a liquid carbon source, or a solid carbon source. When the carbon source is a liquid carbon source, bubbling or volatilizing the carbon source by inert gas and then introducing the carbon source into the reaction chamber; when the carbon source is a solid carbon source, the carbon source can be directly placed into the reaction chamber or volatilized and then introduced into the reaction chamber.
In some embodiments, the carbon source is introduced for a period of time ranging from 1min to 60min, such as 1min, 10min, 15min, 20min, 23min, 30min, 35min, 40min, 42min, 50min, and the like. The longer the carbon source is introduced, i.e. the longer the chemical vapor deposition reaction is, the longer the multi-wall carbon nanotube with longer tube diameter is generally obtained, whereas the shorter the carbon source is introduced, the shorter the tube diameter is, and the single-wall carbon nanotube with shorter tube diameter is obtained. Therefore, the length and shape of the carbon nanotube can be controlled by controlling the carbon source inlet time.
In the chemical vapor deposition reaction process, due to the reaction condition of high-temperature reduction, the graphene oxide in the microsphere can be converted into reduced graphene oxide with excellent conductivity, and meanwhile, the integrity of a spherical structure is maintained. In addition, the reduced graphene oxide has defects on the surface compared with pure graphene, and the defects are more beneficial to the dispersion of the catalyst nano particles on the surface of the reduced graphene oxide, so that the overall catalytic effect is improved.
The invention also provides the graphene carbon nanotube composite material obtained by the method, which has a sea-urchin-like structure and comprises graphene microspheres and a plurality of carbon nanotubes formed on the surfaces of the graphene microspheres, wherein the graphene microspheres are formed by gathering a plurality of thin and flexible carbon sheets, the carbon sheets are formed by 1-10 layers of few layers of reduced graphene oxide, nano-pore channels are formed in the graphene microspheres, and the particle size of the nano-pore channels is 0.1-100 mu m, for example, 0.1 mu m, 1 mu m, 10 mu m, 50 mu m, 70 mu m, 90 mu m, 100 mu m and the like.
In some embodiments, the reduced graphene oxide is a reduced graphene oxide with conductive particles intercalated, that is, carbon sheets are formed by graphene oxide with fewer layers of conductive particles intercalated, each carbon sheet approximately comprises 1-10 layers of reduced graphene oxide with a thickness, wherein the higher the oxidation degree is, the thinner the number of layers of graphene oxide is, and oxygen-containing groups on the surface provide more active sites to adsorb the conductive particles, so that stacking of the reduced graphene oxide sheets in the reduction process is inhibited, and on the other hand, more load sites can be provided for the catalyst, and the carrier utilization efficiency is improved.
The carbon nanotubes may be single-walled carbon nanotubes or multi-walled carbon nanotubes, the diameter of the carbon nanotubes is 1nm to 15nm, for example, 1nm, 5nm, 6nm, 8nm, 10nm, etc., and the tube length is 10nm to 30 μm, for example, 10nm, 20nm, 30nm, 100nm, 1.5 μm, 2 μm, 10 μm, 25 μm, 28 μm, etc.
In conclusion, the graphene carbon nano tube composite powder material with a unique sea urchin-shaped structure is obtained through a specific process, and the graphene microsphere is used as a fulcrum for the growth of the carbon nano tube, so that the entanglement of the carbon nano tube can be prevented, and a stable mechanical supporting effect can be provided. The material can be well dispersed in a solvent and a polymer under the condition of no need of adding a surfactant, forms a long-range and short-range carbon staggered structure with different dimensions, better plays the synergistic effect of the two, and has good application prospect.
The invention will be further illustrated by the following examples, but the invention is not limited thereby. The reagents, materials, etc. used in the present invention are commercially available unless otherwise specified.
Preparation example 1
This preparation example is for explaining a preparation method of a carrier according to an embodiment of the present invention.
1) And taking 4g of graphene oxide and 500mL of deionized water, and uniformly blending the graphene oxide and the deionized water by a mechanical stirrer, wherein the rotating speed is 3000rpm, and the treatment time is 30min, so as to prepare 8mg/mL of graphene oxide coarse dispersion.
2) Taking 0.05g of Keqin black and 20ml of deionized water, and uniformly blending the Keqin black and the deionized water through magnetic stirring, wherein the rotating speed is 200rpm, and the treatment time is 30min, so as to prepare the coarse dispersion liquid of the conductive particles.
3) And adding the coarse dispersion liquid of the conductive particles into the coarse dispersion liquid of the graphene oxide, and treating the coarse dispersion liquid of the conductive particles by an ultracentrifuge grinder, wherein the rotating speed of the ultracentrifuge grinder is 15000rpm, and the treatment time is 20min, so as to prepare the graphene oxide mixed dispersion liquid with the conductive particles intercalated.
4) Granulating and desolventizing the graphene oxide mixed dispersion liquid with the conductive particle intercalation through spray drying equipment, wherein the treatment pressure of the spray drying equipment is 0.2MPa, the treatment flow rate is 1500ml/h, the treatment temperature is 140 ℃, and finally the carbon carrier is prepared.
Preparation example 2
This preparation example is for explaining a preparation method of a carrier according to another embodiment of the present invention.
1) And taking 4g of graphene oxide and 500mL of deionized water, and uniformly blending the graphene oxide and the deionized water by a mechanical stirrer, wherein the rotating speed is 3000rpm, and the treatment time is 30min, so as to prepare 8mg/mL of graphene oxide coarse dispersion.
2) Granulating and desolventizing the graphene oxide mixed dispersion liquid through spray drying equipment, wherein the treatment pressure of the spray drying equipment is 0.2MPa, the treatment flow rate is 1500ml/h, and the treatment temperature is 140 ℃ to obtain the carbon carrier.
Example 1
This example is for illustrating a method for preparing a grapheme carbon nanotube composite material according to the present invention
Fig. 2 is a fluidized bed chemical vapor deposition device for preparing the grapheme carbon nanotube composite material, and as shown in fig. 2, the device body is a single-temperature-zone thermal resistance type vertical tube furnace, the highest experimental temperature can reach 1050 ℃, and the actual temperature floats within +/-1 ℃ of the set temperature in a constant temperature state. The heating chamber of the tube furnace can accommodate a quartz tube 100 with an outer diameter of 2 inches at maximum, and the whole volume of the reaction chamber reaches 600mL. In addition, each path of gas connected with the tube furnace is controlled by a mass flowmeter (MT 51, horiba Scientific), the maximum measuring range is 0 sccm-1000 sccm, and the maximum stable working pressure is 0.2Mpa. While a liquid bubbling tank 200 containing supersaturated ferrocene ethanol solution was provided in the line. The specific structure is shown in figure 1.
1) A porous sieve plate 300 composed of 100-mesh fused quartz particles is additionally arranged in a quartz tube 100, 100mg of the carrier 400 of the preparation example 1 is taken and placed in the quartz tube which is vertically placed, hydrogen and argon are respectively and simultaneously introduced at a flow rate of 300sccm, and the graphene oxide carrier 400 is stably suspended in the quartz tube 100 under the air flow.
2) Heating the fluidized bed reaction chamber to 450 ℃, then introducing Ar gas of 100sccm as carrier gas, introducing supersaturated ferrocene ethanol solution at a constant temperature of 60 ℃ into the reaction chamber by a bubbling method, carrying ferrocene and ethanol, and then thermally cracking to form pre-carbonized iron (Fe) catalyst nanoparticles attached to the surface of the graphene oxide carrier, wherein the bubbling duration is 20 minutes.
3) Then the temperature of the fluidized bed reaction chamber is raised to 700 ℃, hydrogen and argon are respectively and simultaneously introduced at a flow rate of 300sccm, then carbon monoxide is introduced as a carbon source at a flow rate of 100sccm, and after 30 minutes, the carbon monoxide gas is turned off. Stopping the reaction and waiting for the equipment to cool to room temperature, and closing all gases to obtain the graphene carbon nanotube composite material.
Fig. 3 is a scanning electron microscope image of a graphene carbon nanotube composite material of example 1, and it can be seen that the graphene carbon nanotube composite material is sea-urchin-like, and carbon nanotubes with lengths of tens of micrometers are grown on the surface of graphene microspheres in a dispersed manner, and overlap with carbon nanotubes on other graphene microspheres to form a continuous conductive network. Fig. 4a and fig. 4b are respectively transmission electron microscope diagrams of the grapheme carbon nanotube composite material of example 1, and as can be seen from fig. 4a and fig. 4b, the carbon nanotubes prepared under the conditions are single-walled carbon nanotubes, and the tube diameter is 1nm to 3nm.
Fig. 5 is a transmission electron microscope image of the catalyst nanoparticle formed in example 1, and fig. 6 is a statistical distribution diagram of the particle diameter of the catalyst nanoparticle formed in example 1. As can be seen from fig. 5 and 6, the catalyst nanoparticles on the surface of graphene oxide are uniformly distributed, the average particle diameter is 1.78nm, and more than 95% of the particles have a diameter less than 3nm, which is beneficial to preparing single-walled carbon nanotubes with relatively small tube diameters.
Example 2
The preparation method and apparatus were the same as in example 1, except that the temperature of the fluidized bed reaction chamber in step 2) was 400 ℃.
Fig. 7 is a transmission electron microscope image of the catalyst nanoparticle formed in example 2, and fig. 8 is a statistical distribution diagram of the particle diameter of the catalyst nanoparticle formed in example 2. As can be seen from fig. 7 and 8, the catalyst nanoparticles on the graphene oxide surface were uniformly distributed, the average particle diameter was 1.22nm, and 98% or more of the particles were less than 2nm in diameter. It is demonstrated that by lowering the cracking temperature of the catalyst precursor, the particle size of the catalyst can be reduced.
Example 3
The preparation method and apparatus were the same as in example 1, except that the temperature of the fluidized bed reaction chamber in step 2) was 500 ℃.
Fig. 9 is a transmission electron microscope image of the catalyst nanoparticle formed in example 3, and fig. 10 is a statistical distribution diagram of the particle diameter of the catalyst nanoparticle formed in example 3. As can be seen from fig. 9 and 10, the catalyst nanoparticles on the surface of graphene oxide are uniformly distributed, and the average particle diameter is 4.25nm, which indicates that the particle diameter of the catalyst can be obviously increased by increasing the cracking temperature of the catalyst precursor, so that the preparation of carbon nanotubes with larger tube diameter can be regulated.
Fig. 11 is a transmission electron microscope image of the grapheme carbon nanotube composite material of example 3, and it can be seen that the carbon nanotubes prepared under the condition are multi-wall carbon nanotubes, and the tube diameter is 10nm to 15nm.
Example 4
The preparation process and apparatus are the same as in example 1, except that carbon monoxide is fed in step 3) for a period of 5 minutes.
Fig. 12 is a transmission electron microscope image of the graphene carbon nanotube composite material of example 4, and it can be seen from fig. 12 that single-wall carbon nanotubes with a length of only tens of nanometers are grown on the catalyst nanoparticles on the graphene surface, which illustrates that the growth length of the carbon nanotubes can be effectively controlled by controlling the carbon source introduction time during growth.
Example 5
The preparation method and apparatus are the same as in example 1, except that the support of preparation example 2 is used in step 1).
Example 6
The preparation process and apparatus are the same as in example 1, except that no carbon monoxide is fed in step 3).
FIG. 13 is a high resolution transmission electron microscope image of a thin layer region on a carbon support microsphere of preparation example 1, wherein the upper right corner is a Fourier transform image of a dashed frame portion, and a clear lattice structure is not shown, which can indicate that the surface defect degree of the support is high, and the defect is favorable for dispersing the catalyst nano particles on the surface of the support.
Fig. 14 is a high resolution transmission electron microscope image of a thin layer region on a graphene microsphere after annealing under other atmosphere conditions during the growth of a simulated carbon nanotube in example 6, wherein the upper right corner is a transmission electron microscope image with 5 times of local magnification, and the lower right corner is a fourier transform image of a dashed frame portion, showing clear lattice points, which can illustrate that the carrier is converted into a reduced graphene oxide microsphere with a relatively complete structure after being subjected to the treatment of the growth conditions of the carbon nanotube. Is beneficial to ensuring the overall conductivity of the graphene carbon nano tube composite powder.
FIG. 15 is an X-ray photoelectron spectrum of the carbon support microsphere of preparation example 1, showing that the microsphere has rich oxygen-containing functional groups, consistent with the defect conclusion presented in the TEM characterization of FIG. 13. Fig. 16 is an X-ray photoelectron spectrum of the material obtained in example 6, and it can be seen that most of the oxygen-containing functional groups of the graphene oxide microspheres after the carbon nanotube growth condition treatment are removed, and graphitized carbon occupies a great proportion, which is consistent with the conclusion of the reduced graphene oxide microspheres characterized by TEM.
It will be appreciated by persons skilled in the art that the embodiments described herein are merely exemplary and that various other alternatives, modifications and improvements may be made within the scope of the invention. Thus, the present invention is not limited to the above-described embodiments, but only by the claims.

Claims (7)

1. The preparation method of the grapheme carbon nano tube composite material is characterized by comprising the following steps of:
granulating the graphene oxide dispersion liquid to remove the solvent to obtain a carrier;
the carrier is arranged in the reaction chamber;
adjusting the temperature of the reaction chamber to a first temperature, and introducing a metal precursor, wherein the metal precursor is cracked to form metal nano particles on the surface of the carrier, so as to obtain microspheres; and
Regulating the temperature of the reaction chamber to a second temperature, introducing a carbon source, and performing chemical vapor deposition reaction on the surface of the microsphere to grow carbon nanotubes to obtain the graphene carbon nanotube composite material;
the graphene oxide dispersion liquid is a graphene oxide dispersion liquid with intercalation of conductive particles, wherein the conductive particles account for 1% -30% of the total mass of the graphene oxide and the conductive particles, and the conductive particles are selected from one or more of carbon black, onion carbon and fullerene;
the first temperature is 400-700 ℃, and the second temperature is 600-700 ℃;
the metal precursor is ferrocene;
the graphene carbon nanotube composite material has a sea-urchin-like structure and comprises graphene microspheres and a plurality of carbon nanotubes formed on the surfaces of the graphene microspheres, wherein the graphene microspheres are formed by gathering carbon sheets formed by reducing graphene oxide in multiple layers; the carbon nanotubes are single-wall carbon nanotubes or multi-wall carbon nanotubes, the pipe diameter of the carbon nanotubes is 0.1 nm-15 nm, and the pipe length is 10 nm-30 mu m.
2. The method of claim 1, wherein after the carrier is placed in the reaction chamber, an inert carrier gas is introduced to suspend the carrier in the reaction chamber; the inert carrier gas is selected from one or more of nitrogen, argon, krypton and xenon, and the flow rate of the inert carrier gas is 300-1000 sccm.
3. The method of claim 1, wherein the carbon source is selected from one or more of hydrocarbons, alcohols, ethers, ketones, phenols, and carbon monoxide; the carbon source is introduced for 1 min-60 min.
4. The method of claim 1, wherein the conductive particles are ketjen black.
5. A grapheme carbon nanotube composite material, characterized in that it is prepared by the preparation method of any one of claims 1 to 4.
6. The graphene carbon nanotube composite material according to claim 5, wherein the graphene microspheres have nano-tunnels inside, the particle size of the graphene microspheres is 0.1 μm-100 μm, and the carbon sheet comprises 1-10 layers of reduced graphene oxide.
7. The grapheme carbon nanotube composite of claim 5, wherein the reduced graphene oxide is a reduced graphene oxide intercalated with conductive particles.
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