CN114540987B - Thin-diameter carbon nanotube fiber, reaction furnace tube thereof, preparation equipment and preparation method - Google Patents

Thin-diameter carbon nanotube fiber, reaction furnace tube thereof, preparation equipment and preparation method Download PDF

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CN114540987B
CN114540987B CN202210328280.3A CN202210328280A CN114540987B CN 114540987 B CN114540987 B CN 114540987B CN 202210328280 A CN202210328280 A CN 202210328280A CN 114540987 B CN114540987 B CN 114540987B
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carbon nanotube
tube
section
diameter
fiber
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CN114540987A (en
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勇振中
周涛
吴昆杰
张永毅
张亦弛
詹祥和
万子尧
李清文
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Jiangxi Nanotechnology Research Institute
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    • DTEXTILES; PAPER
    • D01NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01FCHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/15Nano-sized carbon materials
    • C01B32/158Carbon nanotubes
    • C01B32/168After-treatment

Abstract

The invention discloses a small-diameter carbon nanotube fiber, a reaction furnace tube, preparation equipment and a method thereof. The reaction furnace tube comprises a first tube body, a second tube body and a third tube body, wherein the first tube body forms a first tube cavity and comprises an injection section, a growth section and an output section; the second tube body forms a second tube cavity and comprises a first end and a second end which are opposite; the first end is arranged in the injection section, the second end is arranged in the growth section, and the second tube cavity is communicated with the first tube cavity through a lower tube opening of the second end; at least the inner diameter of a portion of the second pipe body which meets the lower pipe opening is reduced in a prescribed direction. The invention greatly improves the continuity of the carbon nanotube fiber, and simultaneously, the prepared carbon nanotube fiber has small diameter, good orientation, no damage to the fiber structure and excellent mechanical strength; the carbon nano tube fiber with small diameter and high strength can be prepared by direct growth in one step, the preparation process is simplified, the preparation cost is reduced, and dangerous and polluting chemicals are avoided.

Description

Thin-diameter carbon nanotube fiber, reaction furnace tube thereof, preparation equipment and preparation method
Technical Field
The invention relates to the technical field of inorganic carbon material preparation, in particular to a small-diameter carbon nanotube fiber, a reaction furnace tube, preparation equipment and a preparation method thereof.
Background
The high-performance fiber generally has the characteristics of high strength, high modulus, high temperature resistance, outstanding chemical stability and the like, and is mainly applied to various fields of military industry and high-tech industry. Among the high-performance fibers, carbon fibers and aramid fibers are most representative, the strength of the carbon fibers and the aramid fibers is 4-6.8GPa, the diameter of a monofilament fiber is 7-12 mu m, and the smaller the diameter of the fiber is, the fewer surface or internal defects are, so that the improvement of the mechanical strength is facilitated, and therefore, the smaller the diameter of the fiber is, the more effective the method for improving the strength of the fiber is.
The carbon nanotube fiber is a macroscopic fiber material assembled by single carbon nanotubes and carbon nanotube bundles, and has excellent electrical, mechanical and thermal properties. Has wide application prospect in the fields of composite materials, electronic devices and the like. The theoretical strength of a single carbon nanotube is as high as 100GPa, which is the highest strength in the currently known materials, the strength of a carbon nanotube bundle reported in a laboratory is also as high as 80Cpa, but the single carbon nanotube bundle is limited to be only in the centimeter grade in length, still belongs to the laboratory stage and cannot be applied in the macroscopic stage, and the single carbon nanotube bundle cannot be directly used due to the fact that the single carbon nanotube is in the nanometer grade in size, and must be assembled into a macroscopic carbon nanotube fiber, but the mechanical property transfer from the microscopic carbon nanotube to the macroscopic carbon nanotube fiber is poor, so that the final use is influenced.
The floating catalytic vapor deposition method is the most stable method for preparing carbon nanotube fibers at present. The diameter of the carbon nano tube fiber prepared by the floating catalysis method is 30-100 mu m, and a large number of researches show that the smaller the diameter of the fiber is, the higher the strength is, so that the size of the fiber diameter greatly influences the mechanical property, and the improvement of the fiber strength mainly depends on the reduction of the sectional area of the fiber. The reduction of the diameter of the carbon nano tube fiber can effectively reduce the defects of the fiber structure and increase the van der Waals acting force between tubes, thereby improving the mechanical strength of the carbon nano tube fiber.
Currently, some researchers report that the mechanical strength of the fiber is enhanced by reducing the cross-sectional area of the fiber. For example, in korea, jaegeun Lee et al (Nature Communications 10, 2962, (2019)) of the korean scientific and technical research institute (KIST) immerses carbon nanotube fibers in chlorosulfonic acid and drafts them, thereby reducing the gaps inside the fibers and reducing the fiber diameter, achieving strength improvement of the carbon nanotube fibers to a maximum strength of 4.08N/tex, but the process is complicated, and requires the steps of expansion, secondary densification, etc. of the fibers, and the chlorosulfonic acid used is superacid, thus increasing the process difficulty and risk.
J.N.Wang (J.N.Wang, et al. Nature Communications,2014,5, 3845) greatly reduces the cross-sectional area of the fiber by a rolling densification method, improves the strength of the carbon nanotube fiber, and enables the highest strength of the fiber to reach 8-9GPa, but the fiber structure is damaged after treatment, and the load is reduced.
The preparation methods in the prior art are all two-step preparation, namely: the carbon nanotube fiber with relatively low mechanical property is prepared firstly, and then the fiber is post-treated by post-treatment methods such as drawing or rolling, the preparation method is complex and high in cost, some dangerous and polluting chemicals can be utilized, and the method is very difficult to prepare the carbon nanotube fiber with long continuous length, so that the practical application and the continuous research of the carbon nanotube fiber are greatly limited.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a small-diameter carbon nanotube fiber, a reaction furnace tube, preparation equipment and a preparation method thereof.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
in a first aspect, the invention provides a reaction furnace tube for preparing a thin-diameter carbon nanotube fiber, which comprises a first tube body, a second tube body and a third tube body, wherein the first tube body is used for providing a synthetic environment for a carbon nanotube fiber precursor, the first tube body forms a first tube cavity, and the first tube body comprises an injection section, a growth section and an output section which are sequentially connected along a specified direction;
the carbon nanotube aerogel collector further comprises a second tube body, wherein the second tube body forms a second tube cavity for the carbon nanotube aerogel to pass through, and comprises a first end and a second end which are opposite;
the first end is arranged in the injection section, the second end is arranged in the growth section, and the second tube cavity is communicated with the first tube cavity through a lower tube opening arranged at the second end;
at least the inner diameter of the part of the second pipe body connected with the lower pipe opening is reduced along a designated direction.
In a second aspect, the present invention also provides an apparatus for preparing a thin-diameter carbon nanotube fiber, comprising:
an injection device for injecting carrier gas and reaction raw materials required by the growth of the carbon nano tube;
in the reaction furnace tube, the injection section of the reaction furnace tube is hermetically connected with the injection device, and the carrier gas and the reaction raw material react in the second tube cavity and the growth section of the reaction furnace tube to generate the carbon nanotube precursor;
a heating device for controlling at least the temperature of the growth section of the reaction furnace tube;
and the collecting device is used for compactly converting the carbon nanotube precursor output by the output section of the reaction furnace tube into carbon nanotube fibers and collecting the carbon nanotube fibers.
In a third aspect, the present invention further provides a method for preparing a carbon nanotube fiber with a small diameter, wherein the method for preparing a carbon nanotube fiber with the above-mentioned preparation apparatus comprises:
the carrier gas and the reaction raw material enter a second tube cavity of the reaction furnace tube through the injection device;
the carrier gas and part of the reaction raw materials react in a part of space of the second tube cavity to generate the carbon nano tube aerogel;
enabling the carbon nanotube aerogel to enter the first cavity through the lower pipe orifice of the second cavity and continuously react with part of reaction raw materials to generate a carbon nanotube precursor;
and enabling the carbon nanotube precursor to be compactly converted into the thin-diameter carbon nanotube fiber through a collecting device, and collecting the thin-diameter carbon nanotube fiber.
In a fourth aspect, the invention also provides the small-diameter carbon nanotube fiber prepared by the preparation method, wherein the diameter of the small-diameter carbon nanotube fiber is 8-15 μm, and the mechanical strength is more than 3 GPa.
Based on the technical scheme, compared with the prior art, the invention has the beneficial effects that at least:
according to the preparation device and the preparation method of the small-diameter carbon nanotube fiber, the second tube body with the gradually contracted inner diameter is arranged in the first tube body, so that the flow speed and the orientation of the carbon nanotube aerogel and the carbon nanotube precursor in the preparation process are changed, the carbon nanotube precursor is not in contact with the inner wall of the first tube body, the continuity of the carbon nanotube fiber is greatly improved, and meanwhile, the prepared carbon nanotube fiber is small in diameter, good in orientation and free of damage to a fiber structure, so that the mechanical strength is excellent; and the carbon nano tube fiber with small diameter and high strength can be prepared by direct growth in a one-step method, the preparation process is simplified, the preparation cost is reduced, and the use of dangerous and polluting chemicals is avoided.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to enable those skilled in the art to more clearly understand the technical solutions of the present invention and to implement them according to the content of the description, the following description is made with reference to the preferred embodiments of the present invention and the detailed drawings.
Drawings
FIG. 1 is a schematic structural diagram of an apparatus for manufacturing a carbon nanotube fiber with a small diameter according to an exemplary embodiment of the present invention;
FIG. 2 is a surface low-magnification electron micrograph of a thin-diameter carbon nanotube fiber according to an exemplary embodiment of the present invention;
FIG. 3 is a surface high magnification electron micrograph of a thin diameter carbon nanotube fiber provided in accordance with an exemplary embodiment of the present invention;
fig. 4 is a graph showing the comparison of mechanical strength of carbon nanotube fibers according to an exemplary embodiment of the present invention and a comparison example.
Description of reference numerals: 1. a reaction raw material channel; 2. a carrier gas channel; 3. a first pipe body; 4. a heating device; 5. a second tube body; 6. a sealing box; 7. an exhaust port; 8. a carbon nanotube precursor; 9. carbon nanotube fibers; 10. liquid sealing the box; 11. a collector; 12. carbon nanotube aerogels.
Detailed Description
The chlorosulfonic acid-assisted drawing technique mentioned in the background art expands the carbon nanotube fibers by the protonation of chlorosulfonic acid and draws the carbon nanotube fibers, so that the arrangement and recombination inside the carbon nanotube fibers are realized, the orientation is improved, the fiber diameter is reduced, the acting force between the tubes is increased, and the fiber strength is improved. However, on one hand, the method is dangerous in the treatment process, chlorosulfonic acid reacts violently when meeting water and is decomposed into sulfuric acid and hydrogen chloride gas, which is harmful to human bodies, and on the other hand, the fiber amount treated by the chlorosulfonic acid drawing is small and is only in the centimeter grade, which is difficult to compare with the method for preparing kilometer grade fibers by floating catalysis.
The carbon nanotube fiber rolling compaction technology mainly reduces the gap between tubes in the fiber by rolling the carbon nanotube fiber, thereby reducing the cross-sectional area to realize fiber reinforcement. However, during the rolling process, the internal structure of the fiber is easily damaged, forming defects, resulting in a reduction in fiber load. And the fiber is rolled into a narrow band shape, so that the fiber is difficult to further process, the application direction is reduced, the rolling cost is high, and the continuous rolling is difficult.
Some researchers have tried to obtain carbon nanotube fiber with small diameter directly by one-step method, for example, a reaction furnace tube with small diameter can be used, or the injection of reaction raw material is reduced, or the rate of extracting carbon nanotube fiber from the reaction furnace tube is greatly increased.
In view of the deficiencies in the prior art, the inventors of the present invention have made extensive studies and extensive practices to provide technical solutions of the present invention. The technical solution, its implementation and principles, etc. will be further explained as follows.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced otherwise than as specifically described herein, and thus the scope of the present invention is not limited by the specific embodiments disclosed below.
Moreover, relational terms such as "first" and "second," and the like, may be used solely to distinguish one element or method step from another element or method step having the same name, without necessarily requiring or implying any actual such relationship or order between such elements or method steps.
Referring to fig. 1, an embodiment of the present invention provides a reaction furnace tube for preparing a thin-diameter carbon nanotube fiber, including a first tube body for providing a synthesis environment for a carbon nanotube fiber precursor, where the first tube body forms a first tube cavity, and the first tube body includes an injection section, a growth section, and an output section, which are sequentially connected along a designated direction; the carbon nanotube aerogel conveying pipe comprises a first pipe body, a second pipe body and a third pipe body, wherein the first pipe body is used for forming a first pipe cavity for the carbon nanotube aerogel to pass through, and the second pipe body comprises a first end and a second end which are opposite; the first end is arranged in the injection section, the second end is arranged in the growth section, and the second tube cavity is communicated with the first tube cavity through a lower tube opening arranged at the second end; at least the inner diameter of the part of the second pipe body connected with the lower pipe opening is reduced along a designated direction.
The invention develops continuous preparation equipment and method of superfine carbon nanotube fiber, and particularly provides a reaction furnace tube used by the equipment. The whole device and the process are simple and easy to implement, and the high-strength carbon nanotube fiber can be obtained without further treatment.
The part of the second pipe body 5 with the gradually decreasing inner diameter may be the whole second pipe body 5, or may be a lower half section connected to the lower pipe opening as shown in fig. 1, in this case, an upper half section connected to the lower half section may be of the same diameter, or may be of a variable diameter, and it can be understood that, no matter what shape the upper half section is, any technical scheme for optimizing the orientation and flow rate of the carbon nanotube aerogel 12 or aerogel based on the technical concept of the present invention and by using the gradually shrinking necking structure provided by the present invention falls within the protection scope of the present invention.
In some embodiments, the material of the first tube 3 may include one or a combination of two or more of corundum, quartz, mullite, and graphite.
In some embodiments, the material of the second tube 5 may include corundum, mullite, graphite, or a combination thereof, but is not limited thereto.
In some embodiments, the first tube 3 and the second tube 5 can be connected in a split manner, for example, by a relatively fixed connection via a connecting flange as shown in fig. 1, or in an integral manner, for example, the first tube 3 and the second tube 5 are integrally formed.
In some embodiments, the first tube 3 and the second tube 5 are preferably coaxially arranged. The coaxial arrangement can make first body 3 just to the axis of second body 5 to improve the air current homogenization degree.
In some embodiments, the length of the first pipe 3 may be 800-1600mm, the diameter is 30-150mm, the injection section may account for 5-15% of the total length of the first pipe 3, the growth section may account for 70-90% of the total length of the first pipe 3, and the output section may account for 5-15% of the total length of the first pipe 3.
In some embodiments, the second tube 5 preferably extends 100-300mm into the growth section. The second tube 5 extends into the growth section for a certain distance, so that the carbon nanotubes in the carbon nanotube aerogel 12 generated in the second tube 5 have enough length to form a stable orientation structure at the lower tube opening, and the continuity reduction caused by the adhesion of the carbon nanotubes to the lower tube opening or the inner wall of the second tube 5 due to the overlong carbon nanotubes is avoided; the carbon nanotube aerogel 12 is a mixture of a reaction raw material and a carrier gas to generate a part of primary carbon nanotubes, and the primary carbon nanotubes and the carrier gas and unreacted reaction raw material and any gas generated by the reaction, and the carbon nanotube aerogel 12 can be regarded as a primary carbon nanotube precursor 8 described below.
In some embodiments, the lower nozzle may have an inner diameter of 2 to 40mm, the second pipe body 5 includes an equal diameter section connected to the first end and a variable diameter section connected to the second end, and the equal diameter section is connected to the variable diameter section.
In some embodiments, the inner diameter of the constant diameter section may be 30-150mm.
In some embodiments, the constant diameter section may have a length of 20 to 50mm, and the variable diameter section may have a length of 200 to 480mm.
In some embodiments, the tapered section has a truncated cone shape. The truncated cone shape means that the inner diameter of the second pipe body 5 linearly decreases with increasing distance from the first end, that is, the axial cross section of the reducer section is trapezoidal. Of course, the above-mentioned truncated cone shape is the preferred mode of the present invention for taking care of the processing difficulty of the second tube 5, and those skilled in the art can completely replace the curved cone structure with concave or convex or combination of concave and convex, and these structures all use the orientation and contraction of the gradually narrowing structure, and therefore all fall within the protection scope of the present invention.
With continued reference to fig. 1, an embodiment of the present invention further provides a device for preparing a thin-diameter carbon nanotube fiber, including:
and the injection device is used for injecting carrier gas and reaction raw materials required by the growth of the carbon nano tube.
In the reaction furnace tube provided in the above embodiment, the injection section of the reaction furnace tube is hermetically connected to the injection device, and the carrier gas and the reaction raw material react in the second tube cavity and the growth section of the reaction furnace tube to generate the carbon nanotube precursor 8.
A heating device 4 for controlling the temperature of at least the growth section of the reaction furnace tube.
And the collecting device is used for compactly converting the carbon nanotube precursor 8 output by the output section of the reaction furnace tube into carbon nanotube fibers 9 and collecting the carbon nanotube fibers 9.
In some embodiments, the injection device includes a reaction material channel 1, a carrier gas channel 2, and a connecting flange, the connecting flange is hermetically fixed at the port of the injection section, a second tube 5 in the reaction furnace tube is fixedly arranged at the middle part of the connecting flange, and the reaction material channel 1 and the carrier gas channel 2 are in sealed communication with a second lumen of the second tube 5.
In some embodiments, the collecting device comprises a seal box 6, a liquid seal box 10 and a collector 12, the output section is in sealed communication with the inside of the seal box 6, an end of the seal box 6 away from the output section is provided with an opening, the liquid seal box 10 is arranged near the opening and can contain densification liquid, so that the densification liquid can seal the opening; the carbon nanotube precursor 8 is converted into the carbon nanotube fiber 9 by the densification liquid, and the collector 12 is disposed inside or outside the liquid-tight box 10 and is used for collecting the carbon nanotube fiber 9.
As some specific embodiments, the component composition and the function of the preparation device based on the above embodiment are as follows:
reaction raw material passage 1: the liquid-phase carbon source (i.e., reaction raw material) required for the synthesis of the precursor of the floating carbon nanotube fiber 9 is mainly provided, and in some examples, the gas-phase or gas-liquid double-path carbon source may be used.
Carrier gas passage 2: the carrier gas required in the synthesis process of the carbon nanotube fiber 9 may be nitrogen, argon, helium, or the like.
First pipe body 3: the environment for synthesizing the precursor of the floating carbon nanotube fiber 9 can be corundum tube, mullite tube, graphite tube, etc.
The heating device 4: the first tubular body 3 is heated to provide the necessary temperature for the synthesis of the fibres.
Second pipe 5: the carbon nanotube precursor shrinkage and aggregation device is used for shrinking and aggregating a carbon nanotube precursor 8 into a bundle of carbon nanotube precursors so as to obtain finer carbon nanotube fibers 9, has a certain auxiliary effect on the orientation of the carbon nanotube fibers 9, and has a pipe opening diameter of 2-40mm.
And (6) sealing box: the method is used for collecting the carbon nano tube precursor, and the carbon nano tube precursor is drawn to the densification liquid for densification.
Exhaust port 7: the tail gas in the whole reaction chamber is discharged, and the diameter range of the air hole is 2-10mm.
Carbon nanotube precursor 8: and (3) obtaining the precursor of the superfine carbon nano tube after passing through the reducing liner tube.
Carbon nanotube fibers 9: and (3) shrinking and compacting the carbon nano tube precursor to obtain the fiber.
Liquid seal box 10: and sealing the sealing box 6 by adopting densification liquid, and densifying the carbon nanotube precursor by the surface tension of the densification liquid to obtain the carbon nanotube fiber 9.
Collector 12: and winding and collecting the grown carbon nanotube fiber 9 at a winding speed of 3-30m/min.
The above is a detailed example of the apparatus and the equipment of the present invention, and the above-mentioned equipment can be used to prepare the carbon nanotube fiber 9 with a small diameter, so the embodiment of the present invention further provides a method for preparing the carbon nanotube fiber 9 with a small diameter, and the preparation method of the carbon nanotube fiber 9 by using the preparation equipment provided by the above-mentioned embodiment includes the following steps:
and the carrier gas and the reaction raw material enter the second cavity of the reaction furnace tube through the injection device.
The carrier gas and part of the reaction raw material react in a part of the space of the second tube cavity to generate the carbon nanotube aerogel 12.
And enabling the carbon nanotube aerogel 12 to enter the first cavity through the lower pipe orifice of the second cavity, and continuously reacting with part of reaction raw materials to generate a carbon nanotube precursor 8.
The carbon nanotube precursor 8 is densely transformed into the thin-diameter carbon nanotube fiber 9 by a collecting device and the thin-diameter carbon nanotube fiber 9 is collected.
In some embodiments, the flow rate of the reaction gas formed by the carrier gas and the vaporized reaction raw material at the lower nozzle is 30 to 80 times that at the first end of the second tube 5.
In the preparation method, the reaction raw materials are firstly gasified and cracked in the second tube cavity and subjected to floating gas phase catalytic reaction to generate a part of carbon nanotubes to form the carbon nanotube aerogel 12, then the carbon nanotube aerogel 12 enters the first tube cavity after the contraction and orientation of the lower tube opening of the second tube body 5 and continues to grow, and at the moment, part of the reaction raw materials which are not completely reacted in the second tube cavity can also generate new carbon nanotubes and are wound and combined with the original carbon nanotubes to finally form the shaped carbon nanotube precursor 8; because of the shrinkage effect of the lower pipe orifice, no matter the carbon nanotube aerogel 12 or the carbon nanotube precursor 8 is in contact with the inner wall of the first pipe body 3, the adhesion phenomenon on the inner wall of the first pipe body 3 is avoided, and the continuity and uniformity of the prepared carbon nanotube fiber 9 are greatly improved.
Based on the technical concept of the above embodiments, some specific preparation application examples can be carried out by adopting the following preparation steps:
(1) Heating the reaction furnace tube, especially the growth section thereof, to 1100-1500 ℃, and then introducing gas into the reaction furnace tube, wherein the gas can be a mixed gas of hydrogen and inert gas, the proportion of the hydrogen is 10% -100%, and the flow rate of the carrier gas is 2-10L/min.
(2) Preparing liquid phase carbon source, for example, containing 80-95wt% of carbon-containing organic matter such as ethanol, acetone or isopropanol, 0.3-2wt% of ferrocene, 0.3-2wt% of thiophene and 5-10wt% of water.
(3) Injecting a liquid-phase carbon source into the second tube 5 at an injection rate of 5-60ml/h to react and synthesize the carbon nanotube aerogel 12;
(4) The carbon nano tube aerogel 12 is quickly brought to the lower orifice of the second tube body 5 under the action of carrier gas, because the diameter of the orifice is reduced, at a certain carrier gas flow rate, the outflow speed of the lower orifice is 30-80 times higher than that of the upper orifice, the aerogel is quickly blown out, and meanwhile, the aerogel shrinks and gathers due to the small diameter of the orifice, and finally a bundle of fine carbon nano tube precursor is formed;
(5) The carbon nanotube precursor after thinning passes through water seal liquid in a liquid seal box 10, and the carbon nanotube precursor is further shrunk and densified and fiberized due to the surface tension of water to obtain carbon nanotube fibers 9;
(6) Collecting the carbon nanotube fibers 9 by using a fiber collecting device to finally obtain carbon nanotube fiber 9 materials;
the carbon nanotube fiber 9 collected in the above steps is subjected to structural and mechanical property characterization by a scanning electron microscope, and the result shows that the carbon nanotube fiber 9 has small and uniform diameter, the inner carbon nanotube is well oriented, and the mechanical strength of the carbon nanotube fiber 9 is high.
By adopting the preparation method, the carbon nanotube fiber 9 with small diameter, continuity, uniformity and high strength can be conveniently obtained, therefore, the embodiment of the invention also provides the carbon nanotube fiber 9 with small diameter prepared by the preparation method, the diameter of the carbon nanotube fiber 9 with small diameter is 8-15 μm, the mechanical strength is more than 3GPa, the continuity is generally and easily more than 500m, and the uniformity is more than 90%.
The technical scheme of the invention is further explained in detail by a plurality of embodiments and the accompanying drawings. However, the examples are chosen only for the purpose of illustrating the invention and are not to be construed as limiting the scope of the invention.
Example 1
This example provides a process for preparing a thin-diameter carbon nanotube fiber, which is specifically as follows:
a production apparatus having a structure shown in fig. 1 was employed, in which:
the reaction furnace tube comprises a first tube body 3 and a second tube body 5, wherein the first tube body 3 is a corundum tube with the length of 1200mm and the inner diameter of 100mm, the second tube body 5 is a corundum tube with the constant diameter section of 50mm in inner diameter and 30mm in length, the variable diameter section of 300mm in length, and the lower tube opening of 5mm in diameter.
The connecting flange is fixed at one end of the injection section of the first pipe body 3 in a sealing mode, the equal-diameter section of the second pipe body 5 is fixed at the middle of the connecting flange, and the carrier gas channel 2 and the reaction raw material channel 1 penetrating through the connecting flange are communicated with the inner cavity of the second pipe body 5.
The collector device uses water as the densification liquid, and the collector 11 is arranged outside the liquid seal box 10 and is provided with a winding roller shaft capable of rotating at a rated speed.
The technological process and parameters for preparing the carbon nanotube fiber 9 are as follows:
the temperature of a heating device 4 surrounding the periphery of the first pipe body 3 is controlled to be increased to 1300 ℃, the carrier gas is a mixed gas of 2.5slm of argon and 2.5slm of hydrogen, the reaction raw materials are 1wt% of ferrocene, 2wt% of thiophene, 10wt% of water and the balance of liquid carbon source of acetone, and the injection rate of the liquid carbon source is 30ml/h.
The collector 11 was adjusted to a speed of 20m/min, and the carbon nanotube precursor 8 was drawn from the output end of the first tube 3, passed through water in the seal box 6, and wound around the collector 11 to collect the carbon nanotube fibers 9.
The continuity of the collected fibers reaches 500m, the surface morphology of the fibers is observed by using SEM (scanning Electron microscope), as shown in figures 2-3, the diameter of the fibers is smaller and 12.6 mu m, the diameters of the fibers are close to the sizes of carbon fibers and aramid fibers, the fiber structure is complete, the orientation is good, the density is high, the mechanical property of the fibers is tested as shown in figure 4, the mechanical property is improved by nearly one time compared with that of the fibers without the tapered liner, the average strength reaches 3.5GPa, and the strength uniformity of a multipoint test reaches 90%.
Example 2
This example provides a process for preparing a thin-diameter carbon nanotube fiber, which is substantially the same as that of example 1, except that:
the first tube body 3 is a quartz tube with the length of 1200mm and the inner diameter of 100mm, the second tube body 5 is made of quartz with the equal-diameter section of 50mm and 30mm in inner diameter and the variable-diameter section of 300mm in length, and the lower pipe orifice of 5mm in diameter.
Carbon nanotube fibers 9 having properties similar to those of example 1 can still be prepared.
Example 3
This example provides a process for preparing a carbon nanotube fiber with a small diameter, which is substantially the same as that of example 1, except that:
the speed of the collector 11 was adjusted to 30m/min.
Carbon nanotube fibers 9 having properties similar to those of example 1 can still be prepared.
Example 4
This example provides a process for preparing a carbon nanotube fiber with a small diameter, which is substantially the same as that of example 1, except that:
the carrier gas was a mixture of 2slm of argon and 3slm of hydrogen.
Carbon nanotube fibers 9 having properties similar to those of example 1 can still be prepared.
Example 5
This example provides a process for preparing a carbon nanotube fiber with a small diameter, which is substantially the same as that of example 1, except that:
the reaction raw materials are 1wt% of ferrocene, 1.5wt% of thiophene, 7wt% of water and the balance of liquid carbon source of acetone.
Carbon nanotube fibers 9 having properties similar to those of example 1 can still be prepared.
Example 6
This example provides a process for preparing a thin-diameter carbon nanotube fiber, which is substantially the same as that of example 1, except that:
the rate of carbon source injection was 25ml/h.
Carbon nanotube fibers 9 having properties similar to those of example 1 can still be prepared.
Comparative example 1
This comparative example 1 provides a process for preparing a carbon nanotube fiber, which is substantially the same as in example 1 except that:
the second pipe 5 is a furnace tube of the same material as the second pipe 5 in example 1, which has the same inner and outer diameters in the equal-diameter section.
The diameter of the prepared carbon nanotube fiber is 30 μm, the continuity is remarkably reduced to 100m, and the strength of the carbon nanotube fiber prepared by the comparative example is only 1.8GPa and the uniformity of the strength of the multipoint test is only 80% when the carbon nanotube fiber is subjected to a mechanical property test.
Comparative example 2
This comparative example 1 provides a process for preparing a carbon nanotube fiber, which is substantially the same as in example 1 except that:
the second pipe 5 is a furnace tube of the same material with the length of the equal diameter section of 30mm and the length of the variable diameter section of 70 mm.
The diameter of the prepared carbon nanotube fiber is 30 μm, the continuity is remarkably reduced to 100m, and the strength of the carbon nanotube fiber prepared by the comparative example is only 1.8GPa and the uniformity of the strength of the multipoint test is only 80% when the carbon nanotube fiber is subjected to a mechanical property test.
Comparative example 3
This comparative example 1 provides a process for preparing a carbon nanotube fiber, which is substantially the same as in example 1 except that:
the second tube 5 is a furnace tube of the same material with the length of the constant diameter section of 30mm and the length of the variable diameter section of 150mm.
The diameter of the prepared carbon nanotube fiber is 20 μm, the continuity is remarkably reduced to 200m, and the strength of the carbon nanotube fiber prepared by the comparative example is only 2.3GPa and the uniformity of the strength of the multipoint test is only 85%.
Comparative example 4
This comparative example 1 provides a process for preparing a carbon nanotube fiber, which is substantially the same as in example 1 except that:
the second pipe 5 is a furnace tube of the same material having an equal diameter section of 30mm and a variable diameter section of 530 mm.
The diameter of the prepared carbon nanotube fiber is 12 μm, the continuity is remarkably reduced to 50m, and the strength of the carbon nanotube fiber prepared by the comparative example is only 3.2GPa and the uniformity of the strength of the multipoint test is only 85%.
Based on the above embodiments and comparative examples, it can be clearly seen that in the present invention, the second tube 5 with gradually contracted inner diameter is disposed in the first tube 3, so as to change the flow rate and orientation of the carbon nanotube aerogel 12 and the carbon nanotube precursor 8 during the preparation process, so that the carbon nanotube precursor 8 is not in contact with the inner wall of the first tube 3, thereby greatly improving the continuity of the carbon nanotube fiber 9, and meanwhile, the prepared carbon nanotube fiber 9 has a small diameter, good orientation, and no damage to the fiber structure, so that the mechanical strength is excellent; and the carbon nano tube fiber 9 with small diameter and high strength can be prepared by direct growth in a one-step method, the preparation process is simplified, the preparation cost is reduced, and the use of dangerous and polluting chemicals is avoided.
Meanwhile, it is also clear that the length of the second pipe 5, i.e. the distance of the second pipe 5 extending into the growth section, is a critical parameter for achieving the above technical effects.
It should be understood that the above-mentioned embodiments are merely illustrative of the technical concepts and features of the present invention, which are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and therefore, the protection scope of the present invention is not limited thereby. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims (8)

1. A reaction furnace tube for preparing thin-diameter carbon nanotube fibers comprises a first tube body and a second tube body, wherein the first tube body is used for providing a synthesis environment of a carbon nanotube fiber precursor, the first tube body forms a first tube cavity, and the first tube body comprises an injection section, a growth section and an output section which are sequentially connected along a specified direction;
the carbon nanotube aerogel collector is characterized by further comprising a second tube body, wherein the second tube body forms a second tube cavity for the carbon nanotube aerogel to pass through, and comprises a first end and a second end which are opposite;
the first end is arranged in the injection section, the second end is arranged in the growth section, and the second tube cavity is communicated with the first tube cavity through a lower tube opening arranged at the second end;
at least the inner diameter of the part of the second pipe body connected with the lower pipe opening is reduced along the designated direction;
the length of the first pipe body is 800-1600mm, the diameter of the first pipe body is 30-150mm, the injection section accounts for 5-15% of the total length of the first pipe body, the growth section accounts for 70-90% of the total length of the first pipe body, and the output section accounts for 5-15% of the total length of the first pipe body; the second pipe body extends into the growth section by 250-500 mm;
the inner diameter of the lower pipe orifice is 2-40mm, the second pipe body comprises an equal-diameter section connected with the first end and a variable-diameter section connected with the second end, and the equal-diameter section is connected with the variable-diameter section;
the inner diameter of the constant-diameter section is 30-150 mm;
the length of the constant diameter section is 20-50mm, and the length of the variable diameter section is 200-480mm.
2. The reaction furnace tube of claim 1, wherein the first tube body is made of one or a combination of two or more of corundum, quartz, mullite and graphite;
and/or the material of the second pipe body comprises any one or the combination of more than two of corundum, mullite and graphite.
3. The reaction furnace tube of claim 2, wherein the first tube and the second tube are connected separately or integrally; the first pipe body and the second pipe body are coaxially arranged.
4. The reaction furnace tube of claim 1, wherein the tapered section has a truncated cone shape.
5. A preparation equipment of thin-diameter carbon nanotube fiber is characterized by comprising:
the injection device is used for injecting carrier gas and reaction raw materials required by the growth of the carbon nano tube;
the reaction furnace tube of any one of claims 1 to 4, wherein an injection section of the reaction furnace tube is hermetically connected to the injection device, and the carrier gas and the reaction raw material react in the second tube cavity and the growth section of the reaction furnace tube to generate a carbon nanotube precursor;
a heating device for controlling at least the temperature of the growth section of the reaction furnace tube;
and the collecting device is used for compactly converting the carbon nanotube precursor output by the output section of the reaction furnace tube into carbon nanotube fibers and collecting the carbon nanotube fibers.
6. The apparatus according to claim 5, wherein the injector comprises a reaction material channel, a carrier gas channel, and a connecting flange, the connecting flange is fixed to the port of the injection section in a sealing manner, a second tube of the reaction furnace tube is fixed to an intermediate portion of the connecting flange, and the reaction material channel and the carrier gas channel are in sealing communication with a second tube cavity of the second tube.
7. The apparatus according to claim 5, wherein the collecting device comprises a sealed box, a liquid sealed box and a collector, the output section is in sealed communication with the inside of the sealed box, an end of the sealed box far away from the output section is provided with an opening, the liquid sealed box is arranged near the opening and can contain the densification liquid so that the densification liquid can seal the opening;
the carbon nanotube precursor is converted into carbon nanotube fibers through densification of the densification liquid, and the collector is arranged inside or outside the liquid seal box and used for collecting the carbon nanotube fibers.
8. A method for producing a carbon nanotube fiber having a small diameter, characterized in that the production of the carbon nanotube fiber is carried out by using the production apparatus of any one of claims 5 to 7, the method comprising:
the carrier gas and the reaction raw material enter a second tube cavity of the reaction furnace tube through the injection device;
enabling the carrier gas and part of the reaction raw materials to react in a part of space of the second tube cavity to generate carbon nanotube aerogel;
enabling the carbon nanotube aerogel to enter the first cavity through the lower pipe orifice of the second cavity and continuously react with part of reaction raw materials to generate a carbon nanotube precursor;
enabling the carbon nanotube precursor to be compactly converted into the small-diameter carbon nanotube fiber through a collecting device and collecting the small-diameter carbon nanotube fiber;
the flow rate of the reaction gas formed by the carrier gas and the gasified reaction raw material at the lower nozzle is 30-80 times that at the first end of the second pipe body.
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