CN100386258C - Airgel carbon nanotubes, preparation method and application thereof - Google Patents

Abstract

The present invention relates to an aerogel carbon nanometer tube, and also relates to a preparation method and an application of the aerogel carbon nanometer tube, which belongs to the technical field of nanometer material preparation. The aerogel carbon nanometer tube comprises a dispersed carbon nanometer tube or a carbon nanometer tube bundle, wherein the diameter of the carbon nanometer tube or the carbon nanometer tube bundle is from 1 nanometer to 100 microns, and the length-diameter ratio is from 10<1> to 10<6>. The bulk density of the aerogel carbon nanometer tube is from 0.1 to 100 g/L. The aerogel carbon nanometer tube is obtained through the following method which comprises the steps: the carbon nanometer tube bundle or a carbon nanometer array sample to be treated is crushed by outer force; then, the aerogel carbon nanometer tube is obtained through dispersion, deposition and grading collection in a gas phase. The aerogel carbon nanometer tube is shaped and processed as a heat conduction conductive material, or is compounded with an organic macromolecule, an inorganic material, a metal basal body and the like to form a transparent conductive membrane, a super conductive additive, a membrane material, a mechanical reinforcing and toughening composite material, a heat insulation composite material, a composite material for strengthening the heat conductivity of materials, a composite material for shielding electromagnetic radiation, etc.

Description

Airgel carbon nanotubes, preparation method and application thereof

technical field

The invention relates to a carbon nanotube, a preparation method and an application thereof, in particular to an airgel carbon nanotube, a preparation method and an application thereof, and belongs to the technical field of preparation of new nanomaterials.

Background technique

Carbon Nanotubes (CNTs for short) is a new type of nanomaterial composed of carbon atoms. Due to its ideal one-dimensional structure, it has a wide range of applications in reinforcement, thermal conductivity, electrical conductivity, electromagnetic shielding, microwave-absorbing composite materials, molecular devices, catalyst carriers, and nanoelectronic devices.

At present, carbon nanotubes with various shapes have been obtained. A large number of carbon nanotubes can be obtained by using the "nano-agglomerated bed catalytic cracking method" (patent application number: 01118349.7; PCT/CN02/00044), and a certain amount of ultra-long carbon nanotube arrays can be obtained by using the floating method (Patent Publication No. : CN 1724343A). As a composite material, carbon nanotubes with better dispersion are often required to exert the excellent performance of carbon nanotubes. Therefore, for the practical application of carbon nanotubes, obtaining well-dispersed carbon nanotubes is the primary problem.

At present, most of the well-dispersed carbon nanotubes are carried out in liquid media. For example, "A Method for Washing and Purifying Elongated Carbon Nanotubes Using External Force Breaking Liquid" (Patent No.: ZL02117419.9) is generally carried out in water. The large-scale application of carbon nanotubes is to combine with other matrices to prepare composite materials, which means that in many cases, it is necessary to separate the dispersed carbon nanotubes from the liquid phase. If the dispersion is directly achieved in the gas phase, the solvent removal process is avoided, so gas-phase dispersed carbon nanotubes are a material with important potential applications.

Contents of the invention

The purpose of the present invention is to provide a kind of dispersed airgel carbon nanotubes and its preparation method and application. Liquid phase dispersion is a required desolvation step during compounding.

Technical scheme of the present invention is as follows:

A kind of airgel carbon nanotube, it is characterized in that: described airgel carbon nanotube is made up of dispersed carbon nanotube or carbon nanotube bundle, and the diameter of described carbon nanotube or carbon nanotube bundle is in Between 1 nanometer and 100 micrometers, the aspect ratio is between 10 ¹ and 10 ⁶ , and the bulk density of the airgel carbon nanotube is 0.1 to 100 g/L.

The present invention provides a kind of preparation method of described airgel carbon nanotube, it is characterized in that this method comprises the steps:

1) Using external force to crush the carbon nanotube bundle or carbon nanotube array sample to be processed once or more times to form carbon nanotube aggregates with a bulk density of 0.1-100g/L;

2) Utilize air flow to disperse and settle the sample processed in step 1) in the gas phase;

3) Collecting sediments conforming to the characteristics of the airgel carbon nanotubes in stages to obtain the airgel carbon nanotubes.

In the above steps, the carbon nanotube bundle or carbon nanotube array sample to be processed is a single-walled carbon nanotube bundle, a multi-walled carbon nanotube bundle, a single-walled carbon nanotube array or a multi-walled carbon nanotube array. one or several. The external force method adopts high-speed airflow shearing, mechanical high-speed shearing, sand grinding or explosion methods.

The present invention also provides an application of the airgel carbon nanotubes, that is, the airgel carbon nanotubes can be used as heat-conducting and electrically-conducting materials through shaping and processing, or through compounding with organic polymers, inorganic materials or metal matrices As structural composite materials with enhanced mechanical properties, functional materials with enhanced electrical conductivity, functional materials with increased specific surface area of electrodes and capacitors, functional materials with shielding electromagnetic radiation, composite materials with transparent conductive properties, functional materials with enhanced thermal conductivity, heat insulation Application of functional materials with good performance and catalyst support materials.

Compared with the prior art, the present invention has the following advantages and beneficial effects: the airgel carbon nanotubes provided by the present invention can be directly dispersed in the gas phase, without the required dispersion medium such as liquid phase method; The product can be graded again; there is no damage to the ultra-long carbon nanotube; the process method is simple to operate, low in cost, and easy to scale up in engineering. The airgel carbon nanotubes can form composite structural or functional materials with organic macromolecules, inorganic macromolecules, metals, and the like. Since there is no participation of the liquid phase, the composite material obtained by this method will not include dispersants like blending or other methods to introduce carbon nanotubes. This airgel carbon nanotube can be used as a thermally conductive and electrically conductive material through molding, or as a structural composite material that enhances mechanical properties, a functional material that enhances electrical conductivity, and increases Application of functional materials with specific surface area of electrodes and capacitors, functional materials for shielding electromagnetic radiation, composite materials with transparent conductive properties, functional materials with enhanced thermal conductivity, functional materials with good thermal insulation properties and catalyst carrier materials.

Description of drawings

Figure 1 is a flow chart of the preparation process of airgel carbon nanotubes.

Fig. 2a is a scanning electron micrograph of the carbon nanotube array sample used in the present invention before mechanical crushing.

Fig. 2b is a scanning electron micrograph of a carbon nanotube sample after the carbon nanotube array shown in Fig. 2a is broken by mechanical high-speed shearing according to the present invention.

Figure 2c is a scanning electron micrograph of the airgel carbon nanotubes after the crushed sample was dispersed in the gas phase and settled for 30 seconds.

Figure 2d is a photo of the airgel carbon nanometer scanning electron microscope tube after dispersing and settling the crushed sample in the gas phase for 4 minutes.

Fig. 3 is a scanning electron micrograph of the airgel carbon nanotubes dispersed and settled in the gas phase for 1 min after the carbon nanotube array is sheared by air flow.

Fig. 4a is a scanning electron micrograph of airgel carbon nanotubes after the carbon nanotube bundles are mechanically sheared and crushed at high speed, dispersed and settled in the gas phase for 30 seconds.

Fig. 4b is a scanning electron micrograph of airgel carbon nanotubes after the carbon nanotube bundles are mechanically sheared and crushed at high speed, dispersed and settled in the gas phase for 3 minutes.

Fig. 5 is a scanning electron micrograph of airgel carbon nanotubes dispersed and settled in the gas phase for 15 minutes after the carbon nanotube array is broken by mechanical high-speed shearing.

Fig. 6 is a scanning electron micrograph of paper obtained by forming airgel carbon nanotubes in the gas phase.

Fig. 7 is a scanning electron micrograph of a transparent conductive film formed by laying airgel carbon nanotubes on a transparent polymer film.

Detailed ways

The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The purpose of providing these embodiments is to fully disclose the present invention, and fully convey the idea and implementation effect of the present invention to those skilled in the art. However, the invention can be implemented in many different ways.

Example 1

This example examines the effect of mechanical shear on the gas-phase dispersion of carbon nanotube arrays and the actual effect of airflow dispersion and sedimentation to obtain airgel carbon nanotubes. The sample used was prepared by a planktonic catalysis method to prepare a carbon nanotube array, wherein the length of the carbon nanotube array was 1.4 mm, and the area of the carbon nanotube was about tens of square millimeters. Take 100 mg of the array and place it in a high-speed shearing machine, adjust the mechanical shearing speed to 10,000 rpm, crush it for 2 minutes, and take it out. In the carbon nanotube array, relative to the axial direction of the tubes, the force between the tubes arranged in parallel is very weak, so when mechanical shear occurs, the shear force is more likely to act on the diameter direction of the carbon nanotubes, thus realizing Carbon nanotube arrays become thin tube bundles. Since the carbon nanotubes and the carbon nanotube bundles themselves are flexible, it is ensured that they are not easy to break during the shearing process and keep the original length. See Figure 2b for the SEM photo after pulverization. It can be seen that the extracted carbon nanotube clusters have become carbon nanotube bundles with a diameter of 1-25 μm and a length of 100-1400 μm, with a bulk density of 2 g/cm ³ . It can be seen that the regular carbon nanotube arrays are broken up to form a large group of airgel carbon nanotubes.

Put the above-mentioned airgel carbon nanotubes in a quartz tube with a diameter of 75mm, and pass air with a superficial gas velocity of 0.2m/s. At this time, the volume of the carbon nanotubes further expands, and they are suspended and dispersed in the gas phase. After the air was stopped, the dispersed aerogels began to fall. Collect fallout that falls at different times. The scanning electron micrograph of the product after settling for 0.5 min is shown in Figure 2c. The carbon nanotube bundles with a diameter of 1-25 μm and a length of 100-1400 μm can be used to form airgel agglomerated carbon nanotubes of hundreds of microns, with a bulk density of 1.3 g/L.

See Figure 2d for the scanning electron micrograph of the product after settling for 4 minutes. The carbon nanotube bundles with a diameter of 1-25 μm and a length of 100-1000 μm may be airgel agglomerated carbon nanotubes forming monodisperse bundles, with a bulk density of 0.5 g/L.

Embodiment 2 airflow shearing carbon nanotube array

This embodiment investigates the effect of gas flow shear on the gas phase dispersion of carbon nanotube arrays. The samples used are prepared by the planktonic catalysis method, and are mainly oriented carbon nanotube arrays, wherein the length of the carbon nanotube array is 1.0 mm, and the area of the carbon nanotubes is about tens of square millimeters. Take 1.0 g of the array and place it in an air shearer, adjust the linear velocity of the high-speed shearing air flow to 5 m/s, crush and shear for 2 min, and then take it out. See Figure 3 for the SEM photo after pulverization. It can be seen that the obtained airgel carbon nanotubes have a diameter of 15-30 μm, a length of several hundred to several thousand microns, and a bulk density of 4 g/L.

Put the above-mentioned airgel carbon nanotubes in a quartz tube with a diameter of 75mm, and pass air with a superficial gas velocity of 0.2m/s. At this time, the volume of the carbon nanotubes further expands, and they are suspended and dispersed in the gas phase. After the air was stopped, the dispersed aerogels began to fall. Collect fallout that falls at different times. The product after settling for 1 min is also an airgel carbon nanotube, and its bulk density is 1.4 g/L. The bulk density of airgel carbon nanotubes after settling for 5 minutes was 0.2g/L.

Example 3

This example investigates the effect of mechanical shear on gas-phase dispersion of carbon nanotube bundles. The samples used were prepared by catalytic chemical vapor deposition method, mainly aligned carbon nanotube bundles, and the length of the carbon nanotube arrays was hundreds of microns. Put 1000 mg of the carbon nanotube bundle array in a high-speed shearing machine, adjust the mechanical shearing speed to 10,000 rpm, pulverize for 2 minutes, and then take it out. See Figure 4a for the SEM photo after pulverization. It can be seen that the extracted carbon nanotubes have been in the form of carbon nanotube bundles with a diameter of 50-250 nm and a length of 10-100 μm. Carbon nanotubes form micron-sized clusters. At this time, the bulk density was 42g/L. It can be seen that the regular carbon nanotube arrays are broken up to form large groups of airgel carbon nanotubes.

Put the above-mentioned airgel carbon nanotubes in a quartz tube with a diameter of 75mm, and pass air with a superficial gas velocity of 0.2m/s. At this time, the volume of the carbon nanotubes further expands, and they are suspended and dispersed in the gas phase. After the air was stopped, the dispersed aerogels began to fall. Collect fallout that falls at different times. The scanning electron micrograph of the product after settling for 3 minutes is shown in Figure 4b. The diameter of the carbon nanotube bundle collected at this time may be smaller, the diameter of the carbon nanotube bundle is 50-200 nm, the length is 1-10 μm, and the bulk density is 2.2 g/L.

Example 4

This example investigates the effects of mechanical shearing and sedimentation on gas-phase dispersion of carbon nanotube bundles. The samples used are carbon nanotube bundles. Put 500 mg of the carbon nanotube bundle array in a high-speed shearing machine, adjust the mechanical shearing speed to 30,000 rpm, pulverize it for 20 minutes, and take it out. Then the crushed carbon nanotubes were placed in a quartz tube with a diameter of 75mm, and air with a superficial gas velocity of 0.05m/s was introduced. At this time, the volume of the carbon nanotubes further expanded, and they were suspended and dispersed in the gas phase. After the air was stopped, the dispersed aerogels began to fall. Collect fallout that falls at different times. See Figure 5 for the scanning electron micrograph of the product after settling for 15 minutes. At this time, the carbon nanotubes collected are 10-100 nm, 10-500 μm in length, and have a bulk density of 0.1 g/L.

Example 5

The airgel carbon nanotubes obtained in Example 2 are used as the dispersion medium by using air as the dispersion medium, and the airgel carbon nanotube raw materials are dispersed into the state of carbon nanotube bundles by using a high-speed rotating roller, so that they are suspended in the air, and then the vacuum is adjusted The carbon nanotube bundles fall onto the running copper grid at high speed; the carbon nanotube bundles are staggered and overlapped by the vacuum suction under the copper grid to form a sheet of uniform thickness, which is then bonded, dried, and coiled by epoxy resin. And so on, that is, get the formed paper. See Figure 6 for the microscopic image of the formed paper. The thickness of the paper is 0.1mm, with very low resistivity, its volume resistivity can reach 10 ^-2 Ωcm, thermal conductivity is 1000W/mK, breaking strength is 20.2MPa, elongation at break is 9.4%, and elastic modulus is 436.3 MPa.

Example 6

The above paper is fixed in the suction filtration equipment, and 1% polyvinyl alcohol (PVA) solution is suction filtered through the airgel carbon nanotube paper, at this time, the PVA will be adsorbed to the surface of the carbon nanotube to form a PVA-CNT composite material. The composite material was further hot-pressed, and its thickness was measured to be 0.1mm. It had a very low resistivity, its volume resistivity could reach 1Ωcm, its thermal conductivity was 300W/mK, its breaking strength was 27.42MPa, and its breaking elongation was 4.22%. The elastic modulus is 1956.3MPa, which is much higher than the resistivity and thermal conductivity of the PVA film of equal thickness prepared by the same method. Therefore, the composite material can be used as a structural material for mechanical enhancement, a functional material for enhancing electrical conductivity, and a functional material for enhancing thermal conductivity.

Example 7

The airgel carbon nanotubes obtained in Example 2 were dissolved in deionized water to form a carbon nanotube solution with a concentration of about 10 ppm. The solution was coated on a transparent substrate at a rotational speed of 3000 rpm to form a transparent conductive film with a light transmittance of 80%. The scanning electron microscope photo is shown in FIG. 7 . It can be measured by a four-probe resistance meter that its surface resistivity can reach 1000Ω/port, forming a transparent conductive film with high light transmittance and good conductivity.

Example 8

The airgel carbon nanotubes obtained in Example 2 were dispersed and blended with epoxy resin, and after uniform mixing, a curing agent was added to form a carbon nanotube-epoxy resin mixture. When the content of carbon nanotubes exceeds 0.003wt%, a conductive network is formed, and its conductivity reaches 10 ^-3 S/m, so as long as a small amount of airgel carbon nanotubes are added to the polymer matrix, this can be achieved. Composite materials as conductive materials.

Example 9

After the airgel carbon nanotubes obtained in Example 2 were dispersed, they were ball-milled with aluminum oxide for 12 hours to achieve uniform mixing. Then dry in an oven at 110° C. for 24 hours to obtain a composite powder of airgel carbon nanotubes and aluminum oxide. Then, the composite powder was hot-pressed at 1500° C. for 60 min under a pressing pressure of 20 MPa to prepare an airgel carbon nanotube-aluminum oxide sample. The density of the alumina carrier is 3.80g/cm ³ , the fracture strength is 362MPa, and the fracture toughness is 2.81MPa m ^0.5 . After adding 1% airgel carbon nanotubes, the density of the Al2O3 carrier is 3.76g/cm ³ , the fracture strength is 420MPa, and the fracture toughness is 5.10MPa m ^0.5 . It can be seen that the addition of airgel carbon nanotubes improves the toughness of the ceramic material and also improves the bending strength of the material. This is mainly due to the fact that dispersed carbon nanotubes can be pinned on the grain boundaries of ceramic grains, which can be made into ceramic toughened and reinforced composite materials.

Claims (5)

1. aerogel carbon nanotube is characterized in that: described aerogel carbon nanotube is made up of dispersed carbon nano tube or carbon nanotube tube bank, and the diameter that described carbon nanotube or carbon nanotube are restrained is between 1 nanometer to 100 micron, and length-to-diameter ratio is 10 ¹-10 ⁶Between, this aerogel carbon nanotube bulk density is 0.1～100g/L.

2. the preparation method of aerogel carbon nanotube according to claim 1 is characterized in that this method comprises the steps:

1) utilize external force with the tube bank of pending carbon nanotube or carbon nano pipe array sample through the one or many fragmentation, forming bulk density is the poly-group of 0.1～100g/L carbon nanotube;

2) utilize air-flow in gas phase, to disperse sedimentation through the sample that step 1) is handled;

3) sediment of the feature that meets aerogel carbon nanotube is collected in classification, obtains described aerogel carbon nanotube.

3. according to the preparation method of the described aerogel carbon nanotube of claim 2, it is characterized in that: described pending carbon nanotube tube bank or carbon nano pipe array sample are one or more in Single Walled Carbon Nanotube tube bank, multi-walled carbon nano-tubes tube bank, single-wall carbon nanotube array or the array of multi-walled carbon nanotubes.

4. according to the preparation method of the described aerogel carbon nanotube of claim 2, it is characterized in that: the external force method described in the step (1) adopts high velocity air shearing, mechanical high-speed shearing, sand milling or explosive method.

5. want as described in 1 aerogel carbon nanotube by the material of forming process as right as heat conduction, conduction, or by with organic polymer, inorganic materials or metallic matrix compound as the structural composite material that strengthens mechanical property, strengthen conductivity functional materials, increase electrode and the functional materials of electrical condenser specific surface area, the functional materials of electromagnetic radiation shielding, matrix material, increased thermal conductivity with electrically conducting transparent performance can functional materials, the application of heat-proof quality excellent function material and catalyst support material.

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