Method for preparing core-shell structure metal matrix composite powder by electrostatic self-assembly

Abstract

This invention discloses a method for preparing core-shell structured metal-based composite powders through electrostatic self-assembly. The method includes the following steps: (1) modifying the coating powder with a surfactant to give its surface an opposite charge to that of the metal powder, thereby obtaining a dispersed coating powder dispersion; (2) placing the coating powder dispersion in a solid-liquid fluidized bed and fluidizing the liquid, adding the metal powder to the fluidized bed, and using electrostatic self-assembly to uniformly coat the surface of the metal powder with the coating material. The fluidization time is 5–240 min. After fluidization, the core-shell structured metal-based composite powder is cleaned, dried, and packaged for later use. This invention synthesizes composite powders with uniform coating distribution and controllable content by changing the surface charge distribution of different powders to give them an opposite charge to the metal powder and combining the special flow distribution characteristics of the solid-liquid fluidized bed. It also has the advantages of simple process, low cost, short process and easy large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite material preparation technology, specifically relating to a powder raw material preparation technology for high-performance metal matrix composites for powder metallurgy or 3D printing, and more specifically relating to a method for preparing core-shell structured metal matrix composite powders by electrostatic self-assembly. Background Technology

[0002] Metal matrix composites use metal as a matrix and add one or more reinforcing phases with high strength and high modulus, such as zero-dimensional particles, one-dimensional linear materials, or two-dimensional sheet materials. This allows the metal matrix to not only retain the original physicochemical properties of the metal, but also to correlate the performance of the reinforcing phase with the metal matrix, thereby obtaining better performance than the original metal matrix. This results in better composite materials that can meet more stringent service requirements.

[0003] Currently, in powder metallurgy or 3D printing powders, alloying element powders and reinforcing phases suffer from uneven distribution, easy agglomeration, and susceptibility to structural damage. The key lies in powder preparation. Currently, composite powders prepared by powder metallurgy or 3D printing are generally obtained through mechanical mixing. Due to differences in particle size and density between the reinforcing phase / alloy powder and the metal matrix, and more importantly, the agglomeration of nanoscale coating materials caused by van der Waals forces, it is impossible to achieve a uniform distribution of the coating layer reinforcing phase on the metal powder surface. Composite powders prepared by traditional mechanical mixing methods are mixed composite powders. Mixed composite powders generally rely on external forces, such as centrifugation, stirring, and impact, to distribute one type of particle among another. This results in problems such as localized inhomogeneity and weak bonding forces between different particles. Coated composite powders have attracted widespread attention due to their superior properties. Coated composite powders are classified into particle-embedded coatings, layer coatings, and particle-deposition coatings based on the coating morphology. Early powder coating, as a surface modification technology, was mainly used to solve the problems of dispersion and agglomeration of nanoparticles. As research has continued, it has been discovered that coated composite powders also have technical limitations in the material preparation process. Traditional gas-phase or liquid-phase coating methods cannot directly coat rare earth compounds, metallic elements, and non-metallic elements.

[0004] Electrostatic self-assembly is an emerging method for synthesizing core-shell functional materials and biomolecules using cation-anion or zwitterionic interactions. Typically, the synthesis reaction occurs in polar solvents or aqueous solutions, where the strong van der Waals forces of nanoparticles can be overcome to achieve uniform dispersion. Therefore, electrostatic self-assembly provides a promising approach for preparing core-shell structured composite powders. Furthermore, solid-liquid fluidized bed technology, utilizing the unique flow characteristics of fluidized powders, improves the problem of uneven dispersion between the coating and the coated powder. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing core-shell structured metal-based composite powders through electrostatic self-assembly. Addressing the problems of poor dispersion uniformity and uneven coating in traditional coating powder materials, this invention employs electrostatic self-assembly technology combined with a solid-liquid fluidized bed for powder coating, preparing a novel core-shell structured metal-based composite powder. This composite powder possesses advantages such as high integrity of the metal powder structure, uniform distribution of the coating powder, and low impurity content. The preparation method overcomes the technical bottlenecks in preparing high-quality core-shell structured metal-based composite powders, solving problems such as low powder integrity, easy destruction of the coating powder structure, and impurity contamination. This powder can be directly used as a raw material for sintering and coating powder reinforcement of different alloys, but its applications are not limited to this.

[0006] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0007] A method for preparing core-shell structured metal-based composite powders by electrostatic self-assembly includes the following steps:

[0008] (1) The coated powder is modified with a surfactant to give its surface an opposite charge to that of the metal powder, thereby obtaining a dispersed coated powder dispersion.

[0009] (2) Place the coating layer powder dispersion in a solid-liquid fluidized bed and make the liquid fluidized. Add the metal powder to the fluidized bed and use electrostatic self-assembly technology to make the coating material uniformly coat the surface of the metal powder. The fluidization time is 5 to 240 min. After fluidization, clean, dry and package the core-shell structure metal-based composite powder for later use.

[0010] Specifically, a method for preparing core-shell structured metal-based composite powders through electrostatic self-assembly includes the following steps:

[0011] 1) Preparation of surfactant-modified solution

[0012] A certain mass of surfactant is weighed into a beaker, and deionized water is added. A heating device can be used to accelerate the dissolution rate of the surfactant in the water. After complete dissolution, a modified solution is obtained.

[0013] 2) Coating layer powder dispersion and surface modification

[0014] A certain mass of coating powder is added to the modified solution in step 1), and after ultrasonication and stirring, a well-dispersed modified coating powder dispersion is obtained.

[0015] 3) Construction of solid-liquid fluidized bed and electrostatic self-assembly adsorption experiment

[0016] The solid-liquid fluidized bed device consists of a fluidized bed body, a perforated plate, an inlet-outlet system, connecting hoses, and a power mixing device with a speed-regulating peristaltic pump. The modified coating powder dispersion is loaded into the fluidized bed body. By controlling the speed of the peristaltic pump, the modified coating powder is made to move within the fluidized bed. After a period of time, metal powder is poured into the fluidized bed, initiating contact and bonding with the coating powder. Core-shell structured metal-based composite powder is obtained through electrostatic self-assembly technology. After assembly, the powder is removed, washed, and dried for later use.

[0017] Preferably, the main function of the surfactant used in step (1) is to disperse the coating powder and change the surface charge of the coating powder. The standard for using surfactant is to select a suitable surfactant based on the characteristics of the surface charge distribution of the metal powder so that the surface of the coating powder carries opposite charges and is uniformly dispersed in the solution.

[0018] The composite powder of the present invention uses a metal-based or metal-based alloy as the matrix, and the coating layer powder material accounts for more than 0.05 wt.% of the total weight of the composite powder. The coating layer powder uniformly coated on the surface of the metal powder includes, but is not limited to, one or more of the following materials: carbides, rare earth compounds, metal oxides, non-metallic elements, and metallic elements. At the same time, the coating layer content can be precisely controlled to be no less than 0.05 wt.%.

[0019] Preferably, the coating powder is composed of one or more of the following materials as its main components: carbides, rare earth compounds, metal oxides, non-metallic elements, and metallic elements.

[0020] More preferably, the metal powder is one or at least two of the following: titanium powder, Ti-Fe alloy powder, Ti-Al alloy powder, Ti-Ni alloy powder, aluminum powder, copper powder, aluminum alloy powder, and copper alloy powder.

[0021] Preferably, the metal powder includes, but is not limited to, one of titanium alloy powder, aluminum alloy powder, and copper alloy powder prepared by hydrogenation-dehydrogenation or atomization, with a particle size distribution of 5-150 μm and a powder addition amount of 5-200 g.

[0022] Preferably, the surfactant includes, but is not limited to, one or at least two of cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate, polyvinyl alcohol (PVA), and polyvinylpyrrolidone (PVP).

[0023] Preferably, the surfactant has a mass concentration of 0.1% to 10%. That is, the surfactant-modified solution has a mass concentration of 0.1% to 10%. Preferably, the solid-liquid fluidized bed device consists of a fluidized bed body, a perforated plate, an inlet-outlet, and a mixing device including a connecting hose and a peristaltic pump for speed control, which is a conventional device in the art.

[0024] More preferably, the solid-liquid fluidized bed has a cone-shaped overall distribution and a volume of 500-1500 mL. The inlet and outlet are located at the lower and upper ends of the bed, respectively, and are about 3-5 cm away from both ends.

[0025] Preferably, the sieve plate in the solid-liquid fluidized bed has a pore size distribution of 10–200 μm, and the peristaltic pump has a rotation speed of 20–150 rpm.

[0026] Preferably, the reaction time in the solid-liquid fluidized bed is related to the amount of adsorbed coating powder material, and the fluidization time is generally 5 to 240 min.

[0027] Preferably, ethanol is added during the washing of composite powders to remove excess surfactants and prevent them from affecting the subsequent sintering structure.

[0028] Preferably, the composite powder is dried by vacuum drying, with a vacuum drying temperature of 40-80℃ and a drying time of more than 2 hours.

[0029] This invention utilizes electrostatic self-assembly technology in a solid-liquid fluidized bed to synthesize a core-shell structured, uniformly coated composite powder. While maintaining the original powder structure, it uniformly introduces a coating powder material with high structural integrity. Specifically, surface charge modification is achieved by introducing hydrophilic groups onto the surface of the coating powder material using surfactants, enhancing its hydrophilicity and ensuring surface adhesion to the powder. Simultaneously, the high dynamic flow characteristics of the solid-liquid fluidized bed ensure uniform coating of the powder surface. The high thermal conductivity of the fluidized bed allows for the removal of surface groups at high temperatures, preventing component contamination. Furthermore, the dynamic flow characteristics of the fluidized bed ensure the uniform reduction of surface groups in the coating powder material, avoiding the influence of impurities on alloy properties. This process yields a metal-based composite powder with a uniformly coated layer, providing technical support for the development of powder metallurgy or 3D printing for manufacturing high-performance metal-based composite materials.

[0030] Compared with traditional mechanical mixing techniques for preparing core-shell structured metal-based composite powders, the advantages of this invention are:

[0031] The coated powder material prepared by this invention, which coats a metal-based composite powder, exhibits strong coating properties, high integrity, and low impurity content. The coated powder material is uniformly distributed on the surface of the metal-based powder, has strong adhesion to the matrix, is not easily detached, and possesses a complete and durable structure. This invention primarily achieves this through a combination of surface treatment of the coated powder material and liquid-phase mixing, supplemented by gas-phase heating for impurity removal. Compared to traditional mechanical mixing techniques, this technology is simpler, requires less coated powder material, has lower costs, and is easily scalable, showing promising industrialization prospects. Attached Figure Description

[0032] Figure 1 This is a SEM image of the LaB6-coated Ti hydrogenation-dehydrogenation composite powder in Example 1 of the present invention;

[0033] Figure 2 This is a SEM image of the graphene oxide-coated Al composite powder in Example 2 of the present invention;

[0034] Figure 3 This is a high-magnification SEM image of the graphene oxide-coated Al composite powder in Example 2 of the present invention;

[0035] Figure 4 This is a SEM image of the graphene oxide-coated Ti composite powder in Example 2 of the present invention;

[0036] Figure 5 This is a high-magnification SEM image of the graphene oxide on the surface of the Ti composite powder coated with graphene oxide in Example 2 of the present invention;

[0037] Figure 6 This is a SEM image of the graphene-coated Cu composite powder in Example 3;

[0038] Figure 7 This is a SEM image of the Si powder-coated Ti-Fe composite powder in Example 4;

[0039] Figure 8 This is a SEM image of the boron powder-coated Ti-6Al-4V composite powder in Example 5. Detailed Implementation

[0040] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0041] Example 1

[0042] 1) To prepare a CTAB solution, weigh 0.5–5 g of CTAB and add it to 500 mL of deionized water. Heat at 60–80 °C until it is completely dissolved.

[0043] 2) Weigh 5-10g of LaB6 particles and add them to the solution in 1), sonicate for 10-30 minutes, and then stir for 2-4 hours to obtain a positively charged LaB6 dispersion.

[0044] 3) Place the positively charged LaB6 dispersion from 2) into a solid-liquid fluidized bed, connect the outlet-peristaltic pump control system-inlet device through a silicone tube, then weigh 5-200g of Ti powder into the solid-liquid fluidized bed and make the liquid fluidized. The peristaltic pump speed is 20-150rpm and the mixing time is 5-240min.

[0045] 4) After mixing, the composite powder coated in the solid-liquid fluidized bed in step 3) is taken out and placed in a vacuum oven at 30-80℃ for 2-6 hours to dry, thus obtaining Ti powder coated with LaB6.

[0046] Figure 1 The image shows a SEM image of the LaB6-coated Ti hydrogenation dehydrogenation composite powder in Example 1. The main component of the coating layer on the powder surface is LaB6, which is evenly distributed.

[0047] Example 2

[0048] The difference between Example 2 and Example 1 is that the metal powder is aluminum powder or titanium powder, the coating layer powder material is graphene oxide, and the surfactant is sodium dodecylbenzenesulfonate or polyvinyl alcohol.

[0049] Figure 2 This is a SEM image of the graphene oxide-coated Al composite powder in Example 2;

[0050] Figure 3 This is a high-magnification SEM image of the Al composite powder coated with graphene oxide in Example 2. The graphene oxide is relatively uniformly distributed on the surface of the metal powder.

[0051] Figure 4 This is a SEM image of the graphene oxide-coated Ti composite powder in Example 2;

[0052] Figure 5 This is a high-magnification SEM image of the graphene oxide on the surface of the Ti composite powder coated with graphene oxide in Example 2. The graphene oxide is relatively uniformly distributed on the surface of the metal powder.

[0053] Example 3

[0054] The difference between Example 3 and Example 1 is that the metal powder is replaced with copper powder, and the coating layer powder material is graphene.

[0055] Figure 6 The image shows a SEM image of the graphene-coated Cu composite powder in Example 3. The graphene sheets are uniformly coated on the surface of the Cu composite powder, and the sheet-like graphene can be clearly distinguished.

[0056] Example 4

[0057] The difference between Example 4 and Example 1 is that the metal powder is replaced with Ti-Fe composite powder, and the coating layer powder material is Si powder.

[0058] Figure 7 The image shows a SEM image of the Si-coated Ti-Fe composite powder in Example 4. The Si nanoparticles are coated on the surface of the Ti-Fe composite powder, achieving uniform coating in the fluidized bed after modification.

[0059] Example 5

[0060] The difference between Example 5 and Example 1 is that the metal powder is replaced with Ti-6Al-4V powder, and the coating layer powder material is boron powder. The specific steps are as follows:

[0061] Weigh 45-80g of NaOH and add it to 800mL of deionized water. Then add 3-5g of boron powder and heat and stir at 60-80℃ for 4 hours. After cooling, centrifuge and wash with deionized water until neutral. Then disperse in 500mL of deionized water to obtain a negatively charged boron powder dispersion.

[0062] Subsequently, following the steps in Example 1, the coated composite powder was obtained in a solid-liquid fluidized bed using electrostatic self-assembly technology.

[0063] Figure 8 The image shows a SEM image of the boron powder-coated Ti-6Al-4V composite powder in Example 5. B nanoparticles are uniformly coated on the surface of the Ti-6Al-4V composite powder.

[0064] The upper and lower limits of the process parameters (such as temperature, time, etc.) and the range values ​​of the present invention can all achieve the method, and examples are not listed here.

[0065] All aspects not described in detail in this invention can be covered using conventional technical knowledge in the field.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing core-shell structure metal matrix composite powder by electrostatic self-assembly, the method comprising the following steps: (1) modifying the coating layer powder with a surfactant to make the surface of the coating layer powder have an opposite charge to the metal powder, thereby obtaining a dispersed coating layer powder dispersion liquid; (2) placing the coating layer powder dispersion liquid in a solid-liquid fluidized bed, and making the liquid in a fluidized state, and adding the metal powder into the fluidized bed to make the coating material uniformly coat the surface of the metal powder by electrostatic self-assembly, the fluidization time being 5-240 min, and after fluidization, cleaning, drying and packaging the core-shell structure metal matrix composite powder for use.

2. The method of claim 1, wherein, In step (1), the surfactant includes but is not limited to one or at least two of cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, polyvinyl alcohol and polyvinylpyrrolidone.

3. The method of claim 1, wherein, The mass concentration of the surfactant is 0.1%-10%.

4. The method of claim 1, wherein, The coating layer powder is one or at least two of LaB6, graphene oxide, graphene, Si powder and boron powder.

5. The method of claim 1, wherein, The metal powder is one or at least two of titanium powder, Ti-Fe alloy powder, Ti-Al alloy powder, Ti-Ni alloy powder, aluminum powder, copper powder, aluminum alloy powder and copper alloy powder, and the particle size distribution is 5-150 μm.

6. The method of claim 1, wherein, The mass ratio of the coating layer powder to the metal powder is 1:(1-40).

7. The method of claim 1, wherein, In step (2), the drying temperature is 40-80 ℃, and the drying time is ≥2 h.

8. The method of claim 1, wherein, The solid-liquid fluidized bed comprises a solid-liquid fluidized bed body, a sieve plate, a liquid inlet, a liquid outlet, a connecting hose and a peristaltic pump for speed regulation and control; the solid-liquid fluidized bed body has a whole conical distribution, and has a volume of 500-1500 mL; the liquid inlet and the liquid outlet are respectively arranged at the lower end and the upper end of the solid-liquid fluidized bed body and are located at a distance of 3-5 cm from the two ends; the sieve plate in the solid-liquid fluidized bed has a pore size distribution of 10-200 μm; and the speed of the peristaltic pump is regulated and controlled to be 20-150 rpm.

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