阅读说明：本技术 一种层状碳纳米管增强镁基复合板材及其制备方法 (Layered carbon nanotube reinforced magnesium-based composite board and preparation method thereof ) 是由 沈明杰 朱小倩 李云帅 于 2019-11-19 设计创作，主要内容包括：本发明公开了一种层状碳纳米管增强镁基复合板材及其制备方法,如下：步骤一、将预处理的镁板作为阴极,负电极选为铂丝,电泳沉积所用的碳纳米管悬浮液是碳纳米管、无水硝酸铝以及蒸馏水组成的混合溶体,将阴极和阳极浸入至配置好的碳纳米管悬浮液中,接通电泳电源后放电沉积,得到碳纳米管均匀分散在镁片表面的单层材料；步骤二、通过搅拌摩擦焊技术,将步骤一所获得的两片单层材料实施对焊,单道次搅拌摩擦焊合完成后在近焊缝1-3mm处利用线切割实施板材切割,将保留下的对焊材料再与步骤一所获得的单层材料进行对焊处理,依次进行多道次搅拌摩擦焊加工处理,得到层状结构碳纳米管增强镁基复合板材,制备方法操作简便,易加工成型。(The invention discloses a laminated carbon nanotube reinforced magnesium-based composite board and a preparation method thereof, wherein the preparation method comprises the following steps: step one, taking a pretreated magnesium plate as a cathode, selecting a platinum wire as a negative electrode, immersing the cathode and an anode into a prepared carbon nanotube suspension liquid which is a mixed solution consisting of a carbon nanotube, anhydrous aluminum nitrate and distilled water, and performing discharge deposition after switching on an electrophoresis power supply to obtain a single-layer material in which the carbon nanotube is uniformly dispersed on the surface of a magnesium sheet, wherein the carbon nanotube suspension liquid used for electrophoretic deposition is a mixed solution consisting of the carbon nanotube, anhydrous aluminum nitrate and distilled water; and step two, carrying out butt welding on the two single-layer materials obtained in the step one by a friction stir welding technology, carrying out plate cutting at a position 1-3mm close to a welding line by linear cutting after single-pass friction stir welding is finished, carrying out butt welding treatment on the retained butt welding materials and the single-layer materials obtained in the step one, and carrying out multi-pass friction stir welding processing in sequence to obtain the carbon nano tube reinforced magnesium-based composite plate with the laminated structure.)

1. The preparation method of the layered carbon nanotube reinforced magnesium-based composite board is characterized by comprising the following steps of:

s101, cleaning the surface of the magnesium plate to be processed,

s102, uniformly dispersing the carbon nano tube in an acid solution, sufficiently pickling, cleaning, carrying out suction filtration to obtain filter residue, cleaning and drying the filter residue to obtain a neutral carbon nano tube;

s103, adding the neutral carbon nano tube obtained in the S102 into an electrophoretic deposition solution, taking the magnesium plate cleaned in the S101 as a cathode, and taking a platinum electrode as an anode to perform electrophoretic deposition, so that the carbon nano tube is uniformly distributed on the surface of the magnesium plate, and a primary product of the magnesium plate is obtained;

s200, two magnesium plate primary products prepared in the step 103 are butted, and a friction stir welding process is adopted to weld the butted positions to form a whole magnesium plate with a welding line;

s201, cutting the welded magnesium plates at the position close to the welding seam along the direction of the welding seam in the S200 to form two magnesium plates;

and S202, welding the two magnesium plates obtained in the S201 by adopting the same friction stir welding process, forming a new welding line close to the welding line in the S200, cutting the welded magnesium plates close to the welding line along the direction of the new welding line again, forming the two magnesium plates again, and thus circularly forming the layered carbon nanotube reinforced magnesium-based composite plate with a plurality of welding lines.

2. The method for preparing the layered carbon nanotube reinforced magnesium-based composite board as claimed in claim 1, wherein the step of S101 cleaning the surface of the magnesium board comprises the following steps:

firstly, sand paper with different specifications and sizes is used for removing marks, the surface of the magnesium plate subjected to mark removing treatment is cleaned, then a sulfuric acid solution is used for soaking and cleaning the surface of the cleaned magnesium plate, and then an alkali solution is used for corroding the surface of the pickled magnesium plate for 5 hours.

3. The method of claim 1, wherein in step S102, the mixed acid solution used for pickling the carbon nanotubes is concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 3: 1.

4. The method for preparing the layered carbon nanotube reinforced magnesium-based composite board as claimed in claim 1, wherein in S102, the carbon nanotubes are added into the mixed acid solution, and then subjected to ultrasonic treatment and magnetic stirring to sufficiently acid-wash the carbon nanotubes, and then washed and diluted with deionized water, and then subjected to suction filtration, and the filter residue after suction filtration is repeatedly washed, and finally dried.

5. The method of claim 1, wherein the electrophoretic deposition solution comprises acid-treated carbon nanotube powder, absolute ethanol, acetone, and anhydrous aluminum nitrate in S103.

6. The method for preparing the layered carbon nanotube reinforced magnesium-based composite board as claimed in claim 5, wherein in S103, a mixed solution of alcohol and acetone in a volume ratio of 1:1 is taken, and then the neutral carbon nanotubes are sequentially added into the mixed solution for ultrasonic treatment; and (3) enabling the concentration of the carbon nano tubes in the mixed solution to be 0.05mg/mL-0.2mg/mL, then adding anhydrous aluminum nitrate to enable the concentration of the anhydrous aluminum nitrate to be 0.01mg/mL-0.4mg/mL, and carrying out ultrasonic treatment again to obtain the electrophoretic deposition solution.

7. The method for preparing the layered carbon nanotube reinforced magnesium-based composite plate as claimed in claim 6, wherein the deposition time is 30S-60S at a constant voltage of 20V-50V in S103.

8. The method of claim 1, wherein the cutting of the magnesium plate in S200 and S202 is performed by a wire cutting process, and the distance between the cutting line and the edge of the weld is 1mm to 3 mm.

9. The method of claim 1, wherein in S201 and S202, the friction stir welding is performed at a speed of 90mm/min, the stirring head is rotated at a speed of 1200r/min, and the pressing amount of the stirring head is 3.8 mm.

10. A layered carbon nanotube reinforced magnesium-based composite sheet prepared by the method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of magnesium-based composite material preparation, and particularly relates to a layered carbon nanotube reinforced magnesium-based composite plate and a preparation method thereof.

Background

The magnesium alloy has huge development potential and wide application prospect in the engineering application field as the most competitive light structural material, and is called as a modern ultra-light green metal material. However, the magnesium alloy has low strength and rigidity of about 40GPa, which is not as high as 2/3 of the rigidity of the aluminum alloy (about 70 GPa), and the defects seriously restrict the application of the magnesium alloy as a light structural material in various light engineering fields. In particular, components applied in high-tech fields such as aerospace, transportation, and electronic devices are gradually developing towards light weight, multiple functions and high precision, which puts more severe requirements on the design and research and development of light high-performance structural materials. At present, alloying and compounding are the main means and the most effective way for improving the strength and toughness of metal materials, but alloying is difficult to meet the requirements of high strength and high rigidity at the same time, and the strength and rigidity of the metal materials can be effectively improved at the same time only through compounding. Therefore, the composite method is the only technical approach capable of simultaneously improving the strength and the rigidity. At present, many researchers have conducted extensive and intensive discussion and research on the conventional mg-based composite materials, and although some significant research results have been obtained, the advantages and disadvantages of the mg-based composite materials are also prominent. In the traditional magnesium-based composite material, the strength of the material is improved at the cost of huge loss of the shaping, toughness and damage tolerance of the material, and the application and development of the magnesium-based composite material as a light structural material in the engineering field are greatly limited. Therefore, poor toughness is a major bottleneck problem that restricts the application and development of the traditional magnesium-based composite material. For the above reasons, it is an urgent need to develop a new metal matrix composite material design concept and a new technical approach to improve the mechanical properties (strength, rigidity and toughness) of a magnesium matrix composite material without affecting the toughness.

Currently, Carbon Nanotubes (CNTs) are the most ideal choice for the reinforcing phase of composite materials, and are expected to have a very broad application prospect in composite materials. Since its discovery by japanese scientist Iijima in 1991, CNTs have attracted considerable attention for their unique structure and performance. The modulus of the carbon nano tube is the same as that of diamond, and the theoretical strength reaches 10⁶The theoretical calculated values of MPa and Young modulus can reach 5TPa, the strain can reach 18 percent, and CNTs is taken as the one-dimensional nano material with the highest mechanical property at present and is also considered as the final form of the strengthening phase. At present, although research on CNTs reinforced Mg-based composite materials is in the beginning stage, the research results show that the addition of CNTs can obtain Mg-based composite materials with good comprehensive properties. However, due to the large specific surface area, high specific surface energy, serious entanglement, poor wettability with most metals, etc., CNTs reinforced mg-based composite materials are limited from further development and application.

Disclosure of Invention

The invention aims to provide a layered carbon nanotube reinforced magnesium-based composite plate and a preparation method thereof, which aim to solve the problem of inversion of the toughness of a magnesium-based composite material, and utilize the special size effect and shape effect of CNTs (carbon nanotubes) to ensure that the plasticity of the composite material is not obviously damaged and the composite material has good strength and toughness.

In order to achieve the purpose, the invention adopts the technical scheme that the preparation method of the layered carbon nanotube reinforced magnesium-based composite board comprises the following steps:

s101, cleaning the surface of the magnesium plate to be processed,

s102, uniformly dispersing the carbon nano tube in an acid solution, sufficiently pickling, cleaning, carrying out suction filtration to obtain filter residue, cleaning and drying the filter residue to obtain a neutral carbon nano tube;

s103, adding the neutral carbon nano tube obtained in the S102 into an electrophoretic deposition solution, taking the magnesium plate cleaned in the S101 as a cathode, and taking a platinum electrode as an anode to perform electrophoretic deposition, so that the carbon nano tube is uniformly distributed on the surface of the magnesium plate, and a primary product of the magnesium plate is obtained;

s200, two magnesium plate primary products prepared in the step 103 are butted, and a friction stir welding process is adopted to weld the butted positions to form a whole magnesium plate with a welding line;

s201, cutting the welded magnesium plates at the position close to the welding seam along the direction of the welding seam in the S200 to form two magnesium plates;

and S202, welding the two magnesium plates obtained in the S201 by adopting the same friction stir welding process, forming a new welding line close to the welding line in the S200, cutting the welded magnesium plates close to the welding line along the direction of the new welding line again, forming the two magnesium plates again, and thus circularly forming the layered carbon nanotube reinforced magnesium-based composite plate with a plurality of welding lines.

S101, cleaning the surface of the magnesium plate specifically as follows:

firstly, sand paper with different specifications and sizes is used for removing marks, the surface of the magnesium plate subjected to mark removing treatment is cleaned, then a sulfuric acid solution is used for soaking and cleaning the surface of the cleaned magnesium plate, and then an alkali solution is used for corroding the surface of the pickled magnesium plate for 5 hours.

In S102, concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1 are adopted as a mixed acid solution for pickling the carbon nanotubes.

And S102, adding the carbon nano tube into the mixed acid solution, performing ultrasonic treatment, performing magnetic stirring to fully pickle the carbon nano tube, cleaning and diluting the carbon nano tube with deionized water, performing suction filtration, repeatedly cleaning filter residue after suction filtration, and finally drying the cleaned filter residue.

In S103, the electrophoretic deposition solution comprises carbon nanotube powder subjected to acid treatment, absolute ethyl alcohol, acetone and anhydrous aluminum nitrate.

S103, firstly, taking a mixed solution of alcohol and acetone in a volume ratio of 1:1, and then sequentially adding neutral carbon nanotubes into the mixed solution for ultrasonic treatment; and (3) enabling the concentration of the carbon nano tubes in the mixed solution to be 0.05mg/mL-0.2mg/mL, then adding anhydrous aluminum nitrate to enable the concentration of the anhydrous aluminum nitrate to be 0.01mg/mL-0.4mg/mL, and carrying out ultrasonic treatment again to obtain the electrophoretic deposition solution.

In S103, the deposition time is 30S-60S under the constant voltage of 20V-50V.

And in the S200 and the S202, a linear cutting process is adopted for cutting the magnesium plate, and the distance between a cutting line and the edge of the welding line is 1-3 mm.

In S201 and S202, the advancing speed of the friction stir welding is 90mm/min, the rotating speed of the stirring head is 1200r/min, and the press-in amount of the stirring head is 3.8 mm.

The layered carbon nanotube reinforced magnesium-based composite board prepared by the method is adopted.

The invention relates to a layered carbon nanotube reinforced magnesium-based composite board prepared by the method.

Compared with the prior art, the invention has at least the following beneficial effects:

the preparation method of the invention has simple and convenient operation and easy processing and forming, takes the magnesium alloy plate as the parent material, takes the carbon nano tube as the reinforcement, prepares the primary plate with the carbon nano tube uniformly distributed on the surface of the magnesium plate by the electrophoretic deposition process, the carbon nano tube is uniformly attached to the surface of the magnesium plate after the electrophoretic deposition, no agglomeration phenomenon occurs, the combination between the carbon nano tube and the magnesium plate is good, prepares the layered carbon nano tube reinforced magnesium-based composite plate by the stirring friction welding process, the yield strength of the obtained composite material can reach 220MPa, the tensile strength can reach 325MPa, the elongation can be kept at 6 percent, the carbon nano tube reinforced magnesium alloy does not obviously damage the plasticity of the composite material by utilizing the special size effect and shape effect of CNTs, and simultaneously has good strength and rigidity, without significantly impairing the plasticity of the composite.

Furthermore, compared with untreated carbon nanotubes, the dispersion uniformity of the acid-washed carbon nanotubes is obviously improved, the entanglement phenomenon is effectively solved, the structure of the acid-washed carbon nanotubes is not damaged, the disorder degree is basically not changed, and the pretreatment of the carbon nanotubes can be prepared for the construction of the subsequent laminated magnesium-based composite material and the preparation of qualified materials.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) photograph of carbon nanotubes before pickling;

FIG. 2 is a Scanning Electron Microscope (SEM) photograph of the carbon nanotubes after pickling;

FIG. 3 is a Raman spectrum of the carbon nanotube before and after the acid washing;

FIG. 4 is a Scanning Electron Microscope (SEM) photograph of the surface deposition of magnesium after electrophoretic deposition of carbon nanotubes;

FIG. 5 is a comparison of the mechanical properties of the layered composite material and the magnesium alloy starting sheet in a tensile test.

Detailed Description

The invention is further illustrated by, but is not limited to, the following examples in connection with the accompanying drawings and examples.

In the field of structural materials, a metal-based composite material guided by the design principle of uniform dispersion of a reinforcement forms a uniform CNTs layer on the surface of a magnesium plate by an electrophoretic deposition method, and a layered carbon nanotube reinforced magnesium-based composite material with excellent comprehensive mechanical properties can be obtained by multiple times of friction stir welding treatment.

The process for preparing the laminated carbon nanotube reinforced magnesium-based composite board by using the AZ31 magnesium alloy as the base material comprises the following steps:

the method comprises the following steps: sequentially polishing the magnesium plate with 360#, 800#, 1000# and 2000# sandpaper, removing oil stain on the surface of magnesium by using alcohol, and cleaning and drying by using alcohol to obtain 0.5% H₂SO₄Soaking for 60s to remove an oxide layer on the surface, and soaking in NaOH (5mol/L) solution for 5h to remove grease on the solid surface; in the pickling process, a small part of generated hydrogen is attached to the surface of the magnesium plate, and meanwhile, a small amount of inorganic salt residues are also generated, so that the magnesium plate is soaked in an alkali solution and then placed in alcohol for ultrasonic treatment for 1min to remove the attached small amount of hydrogen and inorganic salt.

In the electrophoretic deposition process, a magnesium plate is used as a cathode, a platinum wire is used as an anode, the two electrodes are immersed into electrophoretic deposition liquid together, and electrophoretic deposition is carried out for 30-60 s at a constant voltage of 20-50V(ii) a Because the anhydrous aluminum nitrate electrolyte is added into the voltage deposition liquid, the carbon nano tube can be adsorbed on Al³⁺So as to have positive charges and make directional movement towards the cathode under the action of the electric field, and further deposit on the surface of the magnesium plate; and after the electrophoretic deposition is finished, obtaining a magnesium plate primary product, uniformly distributing carbon nano tubes on the surface of the magnesium plate primary product, taking out the magnesium plate primary product from the electrophoretic deposition solution, and drying.

Step two: taking the two magnesium plate primary products obtained in the step one, and carrying out butt welding by a friction stir welding technology, wherein the welding advancing speed is 90mm/min, the rotating speed of a stirring head is 1200r/min, and the pressing amount of the stirring head is 3.8 mm. And after the single-pass friction stir welding is finished, cutting the plate at a position 1mm-3mm close to the welding line by utilizing linear cutting, carrying out butt welding treatment (two-pass friction stir welding processing) on the retained butt welding material and the single-layer material obtained in the step one, and sequentially carrying out multi-pass friction stir welding processing to obtain the carbon nano tube reinforced magnesium-based composite material with the laminated structure.

The step one of pickling the carbon nano tubes comprises the steps of measuring 60mL of concentrated sulfuric acid and 20mL of concentrated nitric acid by using a measuring cylinder, adding the concentrated sulfuric acid and 20mL of concentrated nitric acid into a beaker, then measuring 0.8g-1.2g of the carbon nano tubes into a mixed acid solution, carrying out ultrasonic treatment for 2 hours to uniformly disperse the carbon nano tubes in the mixed acid solution, carrying out magnetic stirring for 8 hours-12 hours to fully pickle the carbon nano tubes, then cleaning and diluting the mixed solution obtained after the magnetic stirring by using deionized water, carrying out suction filtration by using a vacuum pump, repeatedly cleaning filter residues after the suction filtration so as to enable the carbon nano tubes subjected to acid treatment to be close to neutrality, and finally placing the carbon nano tubes subjected to the suction filtration in a drying box to be dried for 6 hours-12 hours at.

The electrophoretic deposition solution in the first step is prepared according to the following steps: taking 300mL of anhydrous ethanol and acetone respectively by using a measuring cylinder, mixing the anhydrous ethanol and the acetone to serve as a solvent, adding carbon nanotube powder into the solvent to enable the concentration of the carbon nanotube powder to be 0.05mg/mL-0.2mg/mL, then carrying out ultrasonic treatment on the carbon nanotube powder for 30min, and after the ultrasonic treatment is finished, adding 0.06g-0.24g of anhydrous aluminum nitrate for carrying out ultrasonic treatment for 3h to obtain electrophoretic deposition liquid.