Preparation method of graphene droplet printing three-dimensional preform reinforced magnesium matrix composite

Abstract

The present invention relates to a method for preparing a three-dimensional preform reinforced magnesium matrix composite by graphene droplet printing. Aiming at the problem that it is difficult to achieve the continuity of mechanics, heat conduction and electricity with graphene as the reinforcing body distributed dispersedly in current research, according to the anisotropic characteristics of graphene sheets, methods such as uniform droplet jetting 3D printing, freeze-casting forming and vacuum freeze-drying are proposed to realize the flexible printing preparation of a three-dimensional connected structure low-defect graphene preform with a designable configuration, and a three-dimensional connected graphene-reinforced magnesium matrix composite is prepared by vacuum infiltration liquid-solid extrusion method. The present invention can achieve the three-dimensional connection and overlap between graphene sheets, and can prepare a three-dimensional graphene-reinforced magnesium matrix composite with a designable configuration, laying a foundation for broadening the force-heat-electricity and other functional applications of graphene-reinforced magnesium matrix composites.

Description

Technical Field

[0001] The present invention belongs to a preparation method of graphene-reinforced magnesium matrix composites, and relates to a preparation method of three-dimensional preform-reinforced magnesium matrix composites by graphene droplet printing. Specifically, it relates to a method for preparing a three-dimensional graphene preform with a designable configuration by combining a freeze-casting forming method and a uniform droplet 3D printing technology, and preparing magnesium matrix composites by a vacuum infiltration liquid-solid extrusion process. Background Art

[0002] As a new two-dimensional material, graphene has excellent mechanical, thermal and electrical conductivity, and is widely used as a reinforcing phase in composites. Using graphene as a reinforcement and magnesium alloy as a matrix can obtain magnesium matrix composites with excellent comprehensive properties. However, in the magnesium matrix, graphene sheets are usually discontinuously arranged and prone to defects such as agglomeration, which is not conducive to the load, heat flow and current transfer at the composite interface. Preparing three-dimensional porous graphene can achieve its dispersion and three-dimensional connectivity in the magnesium matrix. Using a vacuum infiltration liquid-solid extrusion process to composite three-dimensional graphene with magnesium alloy can prepare graphene-reinforced magnesium matrix composites with excellent properties. At present, the design of three-dimensional graphene is difficult and the preparation methods are few. If it is used as a preform and combined with the vacuum infiltration liquid-solid extrusion method to prepare three-dimensional graphene-reinforced magnesium matrix composites, new technologies are needed for support.

[0003] The literature (Zhang Q, Zhang F, Medarametla S P, et al. Small, 2016, 12(13): 1702-1708.) proposed to prepare a three-dimensional graphene oxide structure by 3D printing and freeze casting, and then reduce the graphene oxide by heat treatment to obtain a three-dimensional graphene structure, which can be applied to energy storage, catalysis and shock absorption and other projects. After the thermal reduction treatment of graphene oxide in the literature, defects will be generated, and its electrical and thermal conductivity is significantly lower than that of intrinsic graphene; at the same time, the thermal reduction process will also cause deformation and collapse of the designed three-dimensional structure, and it cannot be used as a preform to prepare magnesium matrix composites. Therefore, it is necessary to design a new method to realize the low-defect designable printing of three-dimensional graphene preforms and the preparation of magnesium matrix composites.

[0004] The present invention proposes to combine uniform droplet jet 3D printing with graphene droplet freeze-drying technology to achieve the macro-micro connectivity and configuration designable printing of three-dimensional graphene structures, form three-dimensional graphene structures with specific configurations, and then use a vacuum infiltration liquid-solid extrusion process to infiltrate magnesium alloy into the preform to realize the preparation of three-dimensional graphene-reinforced magnesium matrix composites. Summary of the Invention

[0005] Technical Problems to be Solved

[0006] To avoid the deficiencies of the prior art, the present invention proposes a method for preparing a three-dimensional preform-reinforced magnesium matrix composite by graphene droplet printing, which solves the problems of difficult preparation and poor comprehensive performance of the currently used graphene-reinforced magnesium matrix composites, and proposes a method for preparing a three-dimensional graphene-reinforced magnesium matrix composite with a designable configuration by combining uniform droplet jet 3D printing, rapid low-temperature solidification forming, and vacuum infiltration liquid-solid extrusion process.

[0007] Technical solution

[0008] A method for preparing a three-dimensional preform-reinforced magnesium matrix composite by graphene droplet printing, characterized by the following steps:

[0009] Step 1: Connect the uniformly dispersed low-defect graphene solution to a uniform micro-droplet jetting device, eject a uniform graphene micro-droplet jet through a piezoelectric nozzle, regulate the jetting parameters to ensure that the graphene micro-droplets are jetted onto the surface of a low-temperature substrate and freeze and solidify, and form a graphene ice pattern according to the set printing path; the surface temperature of the low-temperature substrate is -50°C to -120°C; the process of layer-by-layer forming the three-dimensional graphene structure ice pattern is carried out in a closed and dry space;

[0010] Step 2: Place the graphene ice pattern in a vacuum freeze dryer, freeze-dry at -50°C to -70°C for 24h to 72h to obtain a three-dimensional structure graphene preform with a designable configuration according to the design drawing;

[0011] Step 3: Place the three-dimensional structure graphene preform in the die cavity of a vacuum infiltration liquid-solid extrusion process, first evacuate and introduce an Ar atmosphere for preheating, melt and hold the magnesium alloy at a high temperature for 5 to 20 minutes under the protection of an Ar gas environment, evacuate the die cavity to suck the molten magnesium alloy into the extrusion die; the molten metal is infiltrated into the graphene preform under the action of vacuum negative pressure, and after the vacuum infiltration is completed, mechanical pressure is used for shrinkage compensation and pressure holding at semi-solid state through an extrusion punch; then the die is cooled to below 300°C and the die casting is ejected to obtain a three-dimensional structure graphene-reinforced magnesium matrix composite.

[0012] The set printing path is: according to the shape and size requirements of the three-dimensional structure, modeling, model export slicing processing and file input are carried out using computer software and a numerical control system to obtain a low-temperature solidification printing path for the design configuration graphene ice pattern.

[0013] The jetting parameters of the piezoelectric jet valve in the micro-droplet jetting device include: nozzle diameter 50 to 500μm, nozzle height 1 to 10mm, jetting period 0.1 to 2s, and jetting pulse width 10 to 50μs.

[0014] The material of the low-temperature substrate is pure copper material.

[0015] The concentration of the graphene solution is 10 mg / ml to 50 mg / ml.

[0016] The magnesium alloy includes pure magnesium and its alloys.

[0017] The melt temperature for high-temperature melting of the magnesium alloy is 660 °C to 850 °C.

[0018] The preheating temperature range of the extrusion die in Step 3 is 400 °C to 700 °C.

[0019] The vacuum infiltration pressure range in Step 3 is -0.05 to 0.09 MPa.

[0020] The mechanical pressure range in Step 3 is 5 to 40 MPa.

[0021] Beneficial effects

[0022] A method for preparing a three-dimensional preform-reinforced magnesium matrix composite by graphene droplet printing proposed by the present invention aims at the problem that it is difficult to achieve the continuity of mechanics, heat conduction, and electricity with graphene as the dispersed reinforcement in current research. According to the anisotropic characteristics of graphene sheets, methods such as uniform droplet jet 3D printing, freeze-casting forming, and vacuum freeze-drying are combined to achieve the flexible printing preparation of a three-dimensional connected structure low-defect graphene preform with a designable configuration, and a three-dimensional connected graphene-reinforced magnesium matrix composite is prepared by vacuum infiltration liquid-solid extrusion. The present invention can achieve the three-dimensional connection and overlap between graphene sheets, and can prepare a three-dimensional graphene-reinforced magnesium matrix composite with a designable configuration, laying a foundation for broadening the force-thermal-electric and other functional applications of graphene-reinforced magnesium matrix composites.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. The present invention prepares a three-dimensional structure graphene preform by uniform droplet jet 3D printing method and low-temperature rapid solidification forming. The uniform droplet jet method effectively improves the printing resolution, and combined with the freeze-casting forming method, it can print a three-dimensional structure graphene porous material, which can be used for liquid metal infiltration of magnesium matrix composites.

[0025] 2. By regulating process parameters such as micro-droplet jet deposition and solidification lap during the uniform droplet jet process, precise designable printing of different three-dimensional configurations can be achieved, providing a process basis for preparing graphene-reinforced magnesium matrix composites with designable functions such as heat conduction / electricity conduction.

[0026] 3. The present invention realizes the well-controlled preparation of a three-dimensional graphene-reinforced magnesium matrix composite with adjustable comprehensive properties by vacuum infiltration liquid-solid extrusion, laying a technical foundation for its applications in the fields of mechanics, heat conduction, and electricity. Brief description of the drawings

[0027] Figure 1 : Preparation steps of graphene-reinforced magnesium matrix composites

[0028] Figure 2 : Micrographs of graphene-reinforced magnesium matrix composites Specific implementation manners

[0029] The present invention will be further described in conjunction with embodiments and the accompanying drawings:

[0030] Embodiment 1

[0031] A preparation method of a graphene-reinforced magnesium matrix composite with a designable configuration, comprising the following steps:

[0032] 1) Spray a uniformly dispersed graphene solution (15 mg / ml) onto a low-temperature substrate (-70 °C) through uniform microdroplet jet 3D printing for solidification and deposition. The diameter of the spray nozzle is 200 μm, and the designed block configuration morphology is formed through the printing and overlapping solidification of graphene microdroplets.

[0033] 2) Place the ice mold in step 1) in a vacuum freeze dryer for freeze-drying treatment, and dry it in a -70 °C vacuum environment for 48 h to obtain a three-dimensional graphene structure preform with a porous configuration.

[0034] 3) Place the three-dimensional graphene interconnected preform in step 2) in a vacuum infiltration liquid-solid extrusion mold, preheat it at 450 °C for 2 h in an Ar gas environment, heat the AZ91D magnesium alloy to melting at 700 °C, and infiltrate the melt into the preform under a negative pressure of 0.07 MPa. After the temperature drops to the semi-solid state, perform forced feeding to obtain a three-dimensional graphene-reinforced magnesium matrix composite part after cooling.

[0035] Embodiment 2

[0036] A preparation method of a graphene-reinforced magnesium matrix composite with a designable configuration, comprising the following steps:

[0037] 1) Spray a uniformly dispersed graphene solution (20 mg / ml) onto a low-temperature substrate (-120 °C) through uniform microdroplet jet 3D printing for solidification and deposition. The diameter of the spray nozzle is 300 μm, and the designed three-dimensional lattice configuration morphology is formed through the printing and overlapping solidification of graphene microdroplets.

[0038] 2) Place the ice mold in step 1) in a vacuum freeze dryer for freeze-drying treatment, and dry it in a -70 °C vacuum environment for 48 h to obtain a three-dimensional graphene structure preform with a porous configuration.

[0039] 3) Place the three-dimensional graphene preform in step 2) into a vacuum infiltration liquid-solid extrusion mold, preheat it at 500 °C for 2 h in an Ar gas environment, heat the ZK60 magnesium alloy to melting at 750 °C, infiltrate the melt into the preform under a negative pressure of 0.08 MPa, and perform forced feeding when the temperature drops to the semi-solid state, and cool to obtain a three-dimensional graphene-reinforced magnesium matrix composite part.

[0040] Example 3

[0041] A method for preparing a graphene-reinforced magnesium matrix composite with a designable configuration, comprising the following steps:

[0042] 1) Spray the uniformly dispersed graphene solution (35 mg / ml) onto a low-temperature substrate (-100 °C) for solidification and deposition by the uniform micro-droplet jet 3D printing method. The diameter of the spray nozzle is 500 μm, and the designed three-dimensional lattice configuration is formed through the printing and overlapping solidification of graphene micro-droplets.

[0043] 2) Place the ice mold in step 1) into a vacuum freeze dryer for freeze-drying treatment, and dry it in a vacuum environment at -70 °C for 72 h to obtain a three-dimensional graphene structure preform with a porous configuration.

[0044] 3) Place the three-dimensional graphene preform in step 2) into a vacuum infiltration liquid-solid extrusion mold, preheat it at 600 °C for 1 h in an Ar gas environment, heat the ZK60 magnesium alloy to melting at 780 °C, hold for 20 min, infiltrate the melt into the preform under a negative pressure of 0.09 MPa, and perform forced feeding with a mechanical pressure of 15 MPa when the temperature drops to the semi-solid state, and cool to obtain a three-dimensional graphene-reinforced magnesium matrix composite part.

Claims

1. A preparation method of a graphene droplet printing three-dimensional preform reinforced magnesium matrix composite material, characterized in that The steps are as follows: Step 1: Connect the uniformly dispersed low-defect graphene solution to a uniform micro-droplet injection device, eject a uniform graphene micro-droplet jet through a piezoelectric nozzle, regulate the injection parameters to ensure that the graphene micro-droplets are injected onto the surface of a low-temperature substrate and freeze and solidify, and form a graphene ice pattern according to the set printing path; the surface temperature of the low-temperature substrate is -50°C to -120°C; the process of forming the graphene ice pattern layer by layer is carried out in a closed and dry space; Step 2: Place the graphene ice pattern in a vacuum freeze dryer and freeze-dry it at -50°C to -70°C for 24 h to 72 h to obtain a three-dimensional structure graphene preform with a designable configuration of the design drawing; Step 3: Place the three-dimensional structure graphene preform in the die cavity of a vacuum infiltration liquid-solid extrusion process, first evacuate and introduce an Ar atmosphere for preheating, carry out high-temperature melting and insulation of the magnesium alloy for 5 to 20 minutes under the protection of an Ar gas environment, evacuate the die cavity to suck the molten magnesium alloy into the extrusion die; the molten body under the action of vacuum negative pressure infiltrates into the graphene preform, and after the vacuum infiltration ends, mechanical pressure is used for shrinkage compensation and pressure holding through an extrusion punch at semi-solid state; then the die is cooled to below 300°C to eject the die-cast part to obtain a three-dimensional structure graphene-reinforced magnesium matrix composite material.

2. The preparation method of the graphene droplet printing three-dimensional preform reinforced magnesium matrix composite material according to claim 1, characterized in that: The set printing path is: according to the shape and size requirements of the three-dimensional structure, use computer software and a numerical control system for modeling, model export slicing processing and file input to obtain a low-temperature solidification printing path of the design configuration graphene ice pattern.

3. The preparation method of the graphene droplet printing three-dimensional preform reinforced magnesium matrix composite material according to claim 1, characterized in that: The injection parameters of the piezoelectric injection valve in the micro-droplet injection device include: nozzle diameter 50 to 500 μm, nozzle height 1 to 10 mm, injection period 0.1 to 2 s, injection pulse width 10 to 50 μs.

4. The preparation method of the graphene droplet printing three-dimensional preform reinforced magnesium matrix composite material according to claim 1, characterized in that: The material of the low-temperature substrate is pure copper material.

5. The preparation method of the graphene droplet printing three-dimensional preform reinforced magnesium matrix composite material according to claim 1, characterized in that: The concentration of the graphene solution is 10 mg / ml to 50 mg / ml.

6. The preparation method of the graphene droplet printing three-dimensional preform reinforced magnesium matrix composite material according to claim 1, characterized in that: The magnesium alloy includes pure magnesium and its alloys.

7. The preparation method of the graphene droplet printing three-dimensional preform reinforced magnesium matrix composite material according to claim 1, characterized in that: The melt temperature for high-temperature melting of the magnesium alloy is 660°C to 850°C.

8. The preparation method of the graphene droplet printing three-dimensional preform reinforced magnesium matrix composite material according to claim 1, characterized in that: The preheating temperature range of the extrusion die in Step 3 is 400°C to 700°C.

9. The preparation method of the graphene droplet printing three-dimensional preform reinforced magnesium matrix composite material according to claim 1, characterized in that: The vacuum infiltration pressure range in Step 3 is -0.05 to 0.09 MPa.

10. The preparation method of the graphene droplet printing three-dimensional preform reinforced magnesium matrix composite material according to claim 1, characterized in that: The mechanical pressure range in Step 3 is 5 to 40 MPa.

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