Preparation Method of Carbon Nanotube Reinforced Aluminum Matrix Composite

Abstract

The present invention discloses a preparation method of a carbon nanotube reinforced aluminum matrix composite material, which comprises the following steps: Step 1: Ball-mill carbon nanotubes and aluminum powder to form a first composite powder; Step 2: Place the first composite powder in a deionized aqueous solution containing a cationic surfactant and stir. After filtration and drying, a second composite powder is obtained; Step 3: Dissolve the second composite powder and carbon nanotubes in deionized water for electrostatic adsorption for a certain time. After filtration and drying, a third composite powder is formed; Step 4: Hot-press and sinter the third composite powder at a certain temperature and holding pressure time to obtain a carbon nanotube reinforced aluminum matrix composite material. The preparation method of the present invention can effectively increase the addition ratio of carbon nanotubes in the aluminum matrix composite material, thereby greatly improving the mechanical properties of this composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of pure aluminum and aluminum alloys, and specifically refers to a method for preparing a carbon nanotube-reinforced aluminum matrix composite material. Background Art

[0002] Aluminum alloy is a light metal with excellent properties such as good corrosion resistance, high ductility, and low melting point, and is widely used in the fields of aerospace, automotive industry, electronic industry, etc. Although lightweight alloys such as aluminum alloys have a very large industrial consumption, their mechanical properties are poor, which limits their application in other fields. To overcome this limitation, extensive research has been carried out on aluminum matrix composites, and the mechanical properties are improved by adding reinforcements to the composites. At present, carbon nanotubes are considered to be the most ideal composite reinforcement due to their super-strong mechanical properties, extremely low coefficient of expansion, and excellent thermal and electrical conductivity.

[0003] In response to the problem of poor mechanical properties of aluminum alloys, one existing method is to add pretreated carbon nanotubes and sodium dodecyl sulfate to deionized water to prepare a carbon nanotube dispersion, add aluminum nitrate to prepare a carbon nanotube / aluminum salt solution, generate a carbon nanotube / aluminum hydroxide sol by adding ammonia water, atomize the carbon nanotube / aluminum hydroxide sol into small droplets, and evaporate the water of the droplets in a short time through a pyrolysis furnace, and decompose aluminum hydroxide into amorphous alumina, while coating the carbon nanotubes uniformly dispersed in the droplets to obtain spherical particles of amorphous alumina-coated carbon nanotubes with relatively uniform particle sizes, and sinter the spherical powder by hot pressing to generate a carbon nanotube-reinforced alumina matrix composite material. This process is difficult and there is no possibility of industrialization for the time being.

[0004] Another method is to apply a parallel magnetic field along the growth direction of carbon nanotubes in the carbon nanotube growth region during the preparation of carbon nanotubes, so that the magnetic field interacts with magnetic nanoparticles, and then the magnetic nanoparticles are subjected to a magnetic field force in the growth direction, and the magnetic nanocatalyst particles drive the directional growth of carbon nanotubes under the action of the magnetic field force. This method does not involve the related technology for preparing aluminum alloys with high content of carbon nanotubes.

[0005] Carbon nanotubes are an ideal composite reinforcement. At present, there is still a lack of a simple and efficient method for preparing a carbon nanotube-reinforced aluminum matrix composite material with a high content of carbon nanotubes. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing a carbon nanotube-reinforced aluminum matrix composite material. The present invention can effectively increase the addition ratio of carbon nanotubes in the aluminum matrix composite material, thereby greatly improving the mechanical properties of this composite material.

[0007] To achieve this purpose, the preparation method of the carbon nanotube-reinforced aluminum matrix composite material designed by the present invention is characterized in that it comprises the following steps:

[0008] Step 1: High-speed mechanical ball milling of carbon nanotubes and aluminum powder to form a first composite powder;

[0009] Step 2: Placing the first composite powder in a deionized aqueous solution containing a cationic surfactant and stirring at high speed. After filtration and drying, a second composite powder is obtained;

[0010] Step 3: Dissolving the second composite powder and carbon nanotubes in deionized water for electrostatic adsorption for a preset time (electrostatic adsorption is carried out in pure deionized water). After filtration (the filtered deionized water is removed, and the remaining is the third composite powder with carbon nanotubes wrapped on the surface of the second composite powder) and drying, a third composite powder is formed;

[0011] Step 4: Hot pressing and sintering the third composite powder at a certain temperature and holding pressure time to obtain a high-content carbon nanotube-reinforced aluminum matrix composite material.

[0012] In the above-mentioned step 1, the mass percentage of carbon nanotubes in the first composite powder is 10-20 wt.%. Step 1 can make a certain content of carbon nanotubes be wrapped inside the aluminum particles. If the content is less than 10 wt.%, the strengthening effect of the carbon nanotubes is not obvious, which is no different from the traditional preparation method; if the content is higher than 20 wt.%, it is difficult for the carbon nanotubes with too large a volume to be coated by the aluminum powder.

[0013] The above-mentioned step 1 can make a certain physical combination between the carbon nanotubes and the aluminum powder, so that a certain amount of carbon nanotubes are wrapped inside the aluminum particles. Ball milling can make a certain physical combination between the carbon nanotubes and the aluminum powder, so that a certain amount of carbon nanotubes are wrapped inside the aluminum particles; the first composite powder is a mixture of carbon nanotubes and aluminum powder, which is equivalent to embedding carbon nanotubes inside the aluminum powder, and its characteristic is to accommodate the carbon nanotubes to the greatest extent inside the aluminum powder particles.

[0014] The above-mentioned step 2 can coat a layer of cationic surfactant on the surface of the first composite powder obtained in step 1, making its surface positively charged, and preparing for the electrostatic adsorption in step 3. In step 2, the excess cationic surfactant aqueous solution is filtered out, and the remaining is the second composite powder with the cationic surfactant wrapped on the surface of the first composite powder; the second composite powder is the first composite powder wrapped with the cationic surfactant, and its surface is positively charged.

[0015] The above-mentioned step 3 forms a certain combination between the positively charged second composite powder and the negatively charged carbon nanotubes by using the charge force, aiming to carry the largest amount of carbon nanotubes on the surface of the second composite powder as much as possible.

[0016] Step 4 makes the third composite powder form a dense combination, obtaining a high-content carbon nanotube-reinforced aluminum matrix composite material.

[0017] The cationic surfactant is one of cetyltrimethylammonium bromide, polyvinylpyrrolidone, dodecyldimethylbenzylammonium chloride, and octadecyltrimethylammonium chloride. Adding a cationic surfactant can make the surface of the first composite powder positively charged, so that it can adsorb carbon nanotubes with negatively charged surfaces. The above cationic surfactants are selected for their good water solubility.

[0018] In step 3, the time for electrostatic adsorption is 0.5 - 5 h. Electrostatic adsorption is used to combine the second composite powder and carbon nanotubes. If the electrostatic adsorption time is less than 0.5 h, the combination of the two is not firm; if the electrostatic adsorption time is greater than 5 h, the preparation efficiency is low.

[0019] In step 4, the temperature for hot pressing and sintering is 400 - 700 °C.

[0020] In step 4, the time for hot pressing and sintering is 2 - 10 h. If the sintering time is less than 2 h, the aluminum particles cannot be connected to form a whole; if the sintering time exceeds 10 h, excessive Al 4 C 3 is generated, affecting the material properties.

[0021] In step 4, the pressure holding pressure range during hot pressing and sintering of the third composite powder is 100 - 500 MPa. If the pressure holding pressure is lower than 100 MPa, the third composite powder cannot be compacted; if the pressure holding pressure is higher than 500 MPa, the pressed block will crack due to excessive external stress. Through the above hot pressing and sintering, the aluminum powder in the third composite powder is connected in a semi-molten state, thus forming a dense combination, obtaining a high-content carbon nanotube-reinforced aluminum matrix composite material.

[0022] In step 1, a planetary ball mill is used to ball mill carbon nanotubes and aluminum powder. The motor rotation speed range of the planetary ball mill is 100 - 2000 r / min. If the ball milling speed is lower than 100 r / min, carbon nanotubes and aluminum powder cannot form a tight combination; if it is higher than 2000 r / min, the high-speed rotating ball milling steel balls will damage the carbon nanotube structure, affecting the performance of carbon nanotubes. The ball milling process needs to ball mill until the surface of the first composite powder has an obvious metallic luster and there are no residual carbon nanotubes.

[0023] In step 2, the first composite powder is placed in a deionized aqueous solution containing a cationic surfactant and stirred using a constant-temperature magnetic stirrer. The stirring speed ranges from 50 to 500 r / min. If the stirring speed is lower than 50 r / min, the second composite powder cannot form a uniform dispersion in the solution. If the stirring speed is higher than 500 r / min, electrostatic adsorption cannot be achieved due to excessive centrifugal force. The stirring temperature ranges from 50 to 150 °C. If the temperature is lower than 50 °C, it is lower than the initial temperature required for electrostatic adsorption. If the temperature is higher than 150 °C, the molecular structure of the cationic surfactant on the surface of the second composite powder will be damaged.

[0024] In step 3, the mass ratio of the second composite powder to the carbon nanotubes ranges from 10 to 20 wt.%. If the content of the carbon nanotubes is lower than 10%, it is no different from the ordinary preparation method, and the technical advantages of the present invention cannot be reflected. If the content is higher than 20 wt.%, effective electrostatic adsorption of the high-volume-ratio carbon nanotubes on the surface of the second composite powder cannot be achieved.

[0025] Advantages of the present invention:

[0026] In the present invention, aluminum powder is used as an intermediate medium, and carbon nanotubes are embedded inside the aluminum powder by ball milling, and then carbon nanotubes are attached to the outside of the aluminum powder by electrostatic adsorption. This method greatly increases the proportion of carbon nanotubes in the aluminum matrix. The proportion of carbon nanotubes in the aluminum matrix can reach 20 - 40 wt.%. Compared with the highest proportion of carbon nanotubes obtained by the traditional preparation process, which is about 10 - 20 wt.%, the mass ratio of carbon nanotubes in the material obtained by the present invention is doubled, and the mechanical properties of the material can be further improved.

[0027] The raw materials used in the present invention are green and environmentally friendly, the process operation is simple, and it is suitable for large-scale industrial production. Description of the drawings

[0028] Figure 1 is the process flow chart of the present invention; Detailed implementation manners

[0029] The following further describes the present invention in detail with reference to the drawings and specific embodiments:

[0030] Example 1

[0031] A preparation method of a carbon nanotube-reinforced aluminum matrix composite material, as Figure 1 shown, it includes the following steps:

[0032] Step 1: Carbon nanotubes and aluminum powder are subjected to high-speed mechanical ball milling (1000 r / min) using a planetary ball mill to form a first composite powder. The mass percentage of carbon nanotubes in the first composite powder is 15 wt.%.

[0033] Step 2: Place the first composite powder in an aqueous solution of cetyltrimethylammonium bromide in deionized water and stir at a high speed of 300 r / min at a stirring temperature of 80 °C for 30 minutes. After filtration and drying, a second composite powder is obtained.

[0034] Step 3: Dissolve the second composite powder and carbon nanotubes in deionized water for electrostatic adsorption for 3 h. After filtration and drying, a third composite powder is formed. The range of the mass ratio of the second composite powder to the carbon nanotubes is 16 wt.%.

[0035] Step 4: Hot press and sinter the third composite powder at a temperature of 550 °C and a pressure of 300 MPa for 5 h to obtain a high-content carbon nanotube-reinforced aluminum matrix composite.

[0036] Example 2

[0037] Example 2 is prepared according to the steps of Example 1. The difference from Example 1 is that the mass percentage of carbon nanotubes in the first composite powder in Step 1 is 10 wt.%.

[0038] Example 3

[0039] Example 3 is prepared according to the steps of Example 1. The difference from Example 1 is that the mass percentage of carbon nanotubes in the first composite powder in Step 1 is 13 wt.%.

[0040] Example 4

[0041] Example 4 is prepared according to the steps of Example 1. The difference from Example 1 is that the mass percentage of carbon nanotubes in the first composite powder in Step 1 is 17 wt.%.

[0042] Example 5

[0043] Example 5 is prepared according to the steps of Example 1. The difference from Example 1 is that the cationic surfactant in Step 2 is polyvinylpyrrolidone.

[0044] Example 6

[0045] Example 6 is prepared according to the steps of Example 1. The difference from Example 1 is that the cationic surfactant in Step 2 is dodecyldimethylbenzylammonium chloride.

[0046] Example 7

[0047] Example 7 is prepared according to the steps of Example 1. The difference from Example 1 is that the cationic surfactant in Step 2 is octadecyltrimethylammonium chloride.

[0048] Example 8

[0049] Example 8 was prepared according to the steps of Example 1. The difference from Example 1 is that the time of electrostatic adsorption in Step 3 is 0.5 h.

[0050] Example 9

[0051] Example 9 was prepared according to the steps of Example 1. The difference from Example 1 is that the time of electrostatic adsorption in Step 3 is 2 h.

[0052] Example 10

[0053] Example 10 was prepared according to the steps of Example 1. The difference from Example 1 is that the time of electrostatic adsorption in Step 3 is 4 h.

[0054] Example 11

[0055] Example 11 was prepared according to the steps of Example 1. The difference from Example 1 is that the temperature of hot press sintering in Step 4 is 400 °C.

[0056] Example 12

[0057] Example 12 was prepared according to the steps of Example 1. The difference from Example 1 is that the temperature of hot press sintering in Step 4 is 500 °C.

[0058] Example 13

[0059] Example 13 was prepared according to the steps of Example 1. The difference from Example 1 is that the temperature of hot press sintering in Step 4 is 600 °C.

[0060] Example 14

[0061] Example 14 was prepared according to the steps of Example 1. The difference from Example 1 is that the time of hot press sintering in Step 4 is 2 h.

[0062] Example 15

[0063] Example 15 was prepared according to the steps of Example 1. The difference from Example 1 is that the time of hot press sintering in Step 4 is 4 h.

[0064] Example 16

[0065] Example 16 was prepared according to the steps of Example 1. The difference from Example 1 is that the time of magnetic field action in Step 3 is 8 h.

[0066] Comparative Example

[0067] The axial tensile strength and axial elongation of the carbon nanotube-reinforced aluminum matrix composites prepared in Examples 1 to 16 were tested, and the test results are shown in Table 1.

[0068] Table 1 Comparison of mechanical properties of Examples 1 to 16

[0069]

[0070]

[0071] It can be seen from the data in the table that an orthogonal experiment was carried out on five process parameters, namely, the mass percentage of carbon nanotubes in the first composite powder, the type of cationic surfactant, the time of electrostatic adsorption, the temperature of hot pressing and sintering, and the time of hot pressing and sintering. After mechanical property testing, the mass percentage of carbon nanotubes in the first composite powder used in Example 1 was 15 wt.%, cetyltrimethylammonium bromide, electrostatic adsorption for 3 h, and hot pressing and sintering at 550 °C for 5 h were the best process parameters among the above 16 examples. Its axial tensile strength reached 726 MPa, and the axial elongation reached 6.5%.

[0072] Unless otherwise specified, the raw materials and equipment used in the present invention are common raw materials and equipment in the art; unless otherwise specified, the methods used in the present invention are conventional methods in the art.

[0073] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of carbon nanotube reinforced aluminum matrix composite material, characterized in that, it comprises the following steps: Step 1: Ball-mill carbon nanotubes and aluminum powder to form a first composite powder; Step 2: Place the first composite powder in a deionized aqueous solution containing a cationic surfactant and stir. After filtration and drying, a second composite powder is obtained; Step 3: Dissolve the second composite powder and carbon nanotubes in deionized water and perform electrostatic adsorption for a preset time. After filtration and drying, a third composite powder is formed; Step 4: Hot press and sinter the third composite powder at a certain temperature and holding pressure time; In the said Step 1, the mass percentage of carbon nanotubes in the first composite powder is 10 - 20 wt.%; In Step 3, the mass ratio range of the second composite powder to carbon nanotubes is 10 - 20 wt.%; The first composite powder is a mixture of carbon nanotubes and aluminum powder, with carbon nanotubes embedded inside the aluminum powder; The second composite powder is the first composite powder wrapped with a cationic surfactant, and its surface is positively charged; In Step 3, the positively charged second composite powder and the negatively charged carbon nanotubes form a certain combination by means of charge force.

2. The preparation method of carbon nanotube reinforced aluminum matrix composite material according to claim 1, characterized in that: The cationic surfactant is one of cetyltrimethylammonium bromide, polyvinylpyrrolidone, dodecyldimethylbenzylammonium chloride, octadecyltrimethylammonium chloride.

3. The preparation method of carbon nanotube reinforced aluminum matrix composite material according to claim 1, characterized in that: In Step 3, the time of electrostatic adsorption is 0.5 - 5 h.

4. The preparation method of carbon nanotube reinforced aluminum matrix composite material according to claim 1, characterized in that: In Step 4, the temperature of hot press sintering is 400 - 700 °C.

5. The preparation method of carbon nanotube reinforced aluminum matrix composite material according to claim 1, characterized in that: In Step 4, the time of hot press sintering is 2 - 10 h.

6. The preparation method of carbon nanotube reinforced aluminum matrix composite material according to claim 1, characterized in that: In Step 4, the holding pressure range during hot press sintering of the third composite powder is 100 - 500 MPa.

7. The preparation method of carbon nanotube reinforced aluminum matrix composite material according to claim 1, characterized in that: In Step 1, use a ball mill to ball-mill carbon nanotubes and aluminum powder, and the motor speed range of the planetary ball mill is 100 - 2000 r / min.

8. The preparation method of carbon nanotube reinforced aluminum matrix composite material according to claim 1, characterized in that: In Step 2, place the first composite powder in a deionized aqueous solution containing a cationic surfactant and stir it with a constant temperature magnetic stirrer. The stirring speed range is 50 - 500 r / min, and the stirring temperature range is 50 - 150 °C.

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