Method for preparing laminated directional cnts / cu composite material by lost foam assisted sintering

Abstract

The application discloses a kind of methods for preparing directional CNTs / Cu composite material by lost foam auxiliary sintering, and belongs to copper-based composite material technical field.It is first to sequentially oxidize, sensitize, activate and nature load and hydrophilic polymer treatment to original CNTs, so that CNTs functional group is attached with hydrophilic, magnetic nano microparticle on surface;Then the modified CNTs obtained are dispersed in polystyrene mother liquor, and are made into film, and are encapsulated in graphite mold after layer-by-layer stacking to carry out hot-pressing sintering, and the CNTs / Cu composite material is obtained.The application solves the problem that carbon nanotube is unevenly distributed in copper matrix, and is disordered, can further improve the electrical, thermal, mechanical properties etc.of CNTs / Cu composite material, and highlights the anisotropy and directionality of the material.

Description

Technical Field

[0001] This invention belongs to the field of copper-based composite materials technology, specifically relating to a method for preparing oriented CNTs / Cu composite materials by lost foam assisted sintering. Background Technology

[0002] The rapid development of science and technology and the socio-economic landscape has placed increasingly higher demands on copper materials with excellent comprehensive properties, thus promoting the development of copper-based composite materials. Copper and its alloys possess high electrical and thermal conductivity, making them widely used in aerospace, integrated circuits, and electronic information industries. However, their low strength and poor high-temperature resistance make it difficult to meet the demands of today's rapidly developing manufacturing sector, significantly limiting their application range. For example, applications of copper and its alloys in wires and cables, power busbars, contact wires for rail transit, printed circuit boards, lead frames, and photovoltaic copper strips for solar cells all require high tensile strength while maintaining high electrical and thermal conductivity. Traditional copper alloys improve their tensile strength by introducing high-hardness, high-melting-point metals such as Cr and W, or metal oxides / carbides, but their electrical conductivity is usually significantly affected.

[0003] Carbon nanotubes are cylindrical carbon tubes formed by rolling up layers of graphite carbon atoms, with each C atom interacting with three surrounding C atoms at splines. 2 Hybridization forms C=C bonds, and these strong covalent bonds stabilize the carbon nanotube structure, resulting in extremely high strength and toughness. CNTs have demonstrated excellent strengthening effects in metal-based composites such as aluminum and copper. Currently, the preparation of CNTs is becoming increasingly sophisticated, and they are considered ideal reinforcing phases for preparing high-performance composites. This is not only due to the superior mechanical properties of carbon nanotubes and graphene, but also because carbon nanomaterials have good chemical compatibility with Cu, which helps maintain the unique one-dimensional and two-dimensional structures of carbon nanomaterials. Therefore, adding even a small amount of carbon nanomaterials exhibits extremely high reinforcing effects, effectively improving not only the strength of the matrix alloy but also demonstrating good plasticity.

[0004] Typically, CNTs are directly mixed with a copper matrix during composite material preparation, using methods such as powder metallurgy, electrophoretic deposition, and template methods. However, with these methods, the incorporated CNTs usually exist in a disordered state within the matrix, making it difficult to guarantee their dispersion. If carbon nanotubes are uniformly and orderly dispersed within the copper matrix, their performance enhancement effect in a specific direction can be significantly enhanced, potentially leading to high-performance composite materials. Based on this, methods for assisting in the orientation of CNTs have emerged, such as: first preparing a mixed and dispersed CNTs / Cu composite material, then continuously deforming it along the same direction through stretching or rolling to promote the alignment of carbon nanotubes along the deformation direction; or adding a magnetic field during powder metallurgy to achieve a tendency for CNTs to align along their axial direction within the copper matrix; or adding an electromagnetic field during electrophoretic deposition to ensure consistent orientation of carbon nanotubes within the copper matrix. These methods are complex to implement, require expensive equipment, and due to interfacial compatibility issues between CNTs and the metal matrix, their alignment and dispersion effects are not significant. Taking electrophoretic deposition as an example, carbon nanotubes undergo Brownian motion in the electrophoretic solution at all times. Even with strong magnetic field for directional control, it is difficult to maintain their directional and ordered distribution during the electrophoresis process.

[0005] The lost foam method for preparing composite materials involves pre-fabricating CNTs with polystyrene foam material, thereby fixing the oriented CNTs in the polystyrene matrix in real time. Therefore, it is a simple and effective way to prepare CNTs / Cu composite materials with oriented carbon nanotubes. Summary of the Invention

[0006] To address the problem of uneven and disordered distribution of carbon nanotubes in a copper matrix, this invention provides a method for preparing oriented CNTs / Cu composite materials by lost foam assisted sintering. The method involves first dispersing CNTs in polystyrene to prepare an oriented thin film, and then utilizing the properties of lost foam material to transfer the oriented distribution pattern of carbon nanotubes from the polystyrene film to the copper matrix, thereby preparing an oriented CNTs / Cu composite material with excellent strengthening effect.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing layered oriented CNTs / Cu composite materials by lost foam sintering includes the following steps:

[0009] 1) After carbon nanotubes (CNTs) were successively oxidized, sensitized and activated, their surfaces were magnetically loaded and treated with hydrophilic polymers by coprecipitation, and then repeatedly centrifuged, filtered and dried to obtain modified CNTs.

[0010] 2) Dissolve a certain amount of polystyrene (PS) masterbatch in tetrahydrofuran, then add the modified CNTs to the solution, disperse by ultrasonication, filter and let stand to obtain a uniformly dispersed CNTs-foaming mold suspension.

[0011] 3) Place the copper foil into the CNTs-foaming mold suspension obtained in step 2), and then place it in a magnetic field. Use a high magnetic flux magnetic field-assisted lifting method to coat the copper foil along the direction of the magnetic field to obtain copper foil-foaming mold film unit.

[0012] 4) Stack the copper foil-foamed film units obtained in step 3) layer by layer, cut them and encapsulate them in a graphite mold for hot pressing and sintering to obtain the layered oriented CNTs / Cu composite material.

[0013] Further, in step 1), the oxidation treatment involves soaking CNTs in a mixture of H2SO4 and HNO3 at a volume ratio of 3:1 for 4 hours.

[0014] Further, in step 1), the sensitization treatment involves placing the oxidized CNTs in a 10 ml / L HCl solution containing 0.1 mol / L SnCl2 and sonicating for 30 min.

[0015] Further, in step 1), the activation treatment involves placing the sensitized CNTs in a 5 ml / L HCl solution containing 0.25 g / L PdCl2 and sonicating for 30 min.

[0016] Further, the magnetic loading and hydrophilic polymer treatment described in step 1) involves dissolving 1g of ferrous chloride tetrahydrate and 1.5g of ferric chloride hexahydrate in 100ml of deionized water, adding 0.25g of activated and dried CNTs and ultrasonically dispersing them, then adding a 5% (w / w) ammonia solution until no more precipitate forms, and then bathing in a water bath at 60°C for 30min. After that, adding a 0.02g / mL sodium polystyrene sulfonate (PSS) aqueous solution at a mass ratio of 1:4 with the CNTs used, ultrasonically treating for 30min, and then magnetically stirring for 24h.

[0017] Furthermore, the volume ratio of PS masterbatch to CNTs used in step 2) is 8:1.

[0018] Furthermore, the total concentration of the CNTs-foaming mold suspension obtained in step 2) is 0.03 g / L.

[0019] Furthermore, the magnetic induction intensity of the magnetic field in step 3) is 1~2T.

[0020] Further, in step 4), the hot pressing sintering temperature is 900-1000℃, the time is 1 hour, and the vacuum degree is maintained at 2×10⁻⁶. -3 Pa, pressure maintained at 50 MPa.

[0021] The present invention has the following advantages:

[0022] (1) The equipment involved in this invention is simple to operate;

[0023] (2) The method used in this invention can effectively ensure that carbon nanotubes are oriented in a specified direction on the copper substrate;

[0024] (3) In this invention, the distribution of CNTs in the copper matrix is ​​controllable and can be adjusted by changing the pulling speed as needed to prepare composite materials with gradient distribution of CNTs. Attached Figure Description

[0025] Figure 1 The image shows a SEM image of the oriented CNTs / Cu composite material obtained in the example. As can be seen from the image, the CNTs are separated from each other with minimal entanglement and exhibit a certain orientation distribution under the influence of a magnetic field.

[0026] Figure 2 The image shows a SEM image of the non-oriented CNTs / Cu composite material obtained in the comparative example. As can be seen from the image, the CNTs are entangled with each other, with a large number of knots, and the overall structure exhibits a disordered state.

[0027] Figure 3 The images show the microstructures of the oriented CNTs / Cu composite material (A) obtained in the example and the non-oriented CNTs / Cu composite material (B) obtained in the comparative example. As can be seen from the comparison, the microstructure of the oriented composite material is mainly composed of smaller, more distributed annealed twins, while the microstructure of the non-oriented composite material has larger grains extending beyond the copper foil layer.

[0028] Figure 4 The figure shows a comparison of the tensile curves of the oriented CNTs / Cu composite material obtained in the example and the non-oriented CNTs / Cu composite material obtained in the comparative example. As can be seen from the figure, the tensile strength of the oriented composite material is higher than that of the non-oriented composite material, while the elongation is lower. This is because the reinforcing effect of CNTs in the oriented composite material is stronger during the tensile process than that in the non-oriented composite material. Detailed Implementation

[0029] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto. Example

[0030] The magnetic field used is generated in the form of an energized coil (air gap 20mm). When the switch is closed, a stable magnetic induction intensity of 1~2T is generated in the air gap of the energized coil.

[0031] A method for lost foam assisted sintering of oriented CNTs / Cu composite materials, comprising the following steps:

[0032] Step 1: Oxidation process: Disperse 1g of CNTs in a mixed acid solution with V(H2SO4):V(HNO3)=3:1 and oxidize for 4h. Filter, wash until neutral and dry.

[0033] Step 2: Sensitization process: The oxidized CNTs were placed in a mixed solution of SnCl2 (0.1 mol / L) and HCl (10 ml / L) and sonicated for 30 min, then filtered, washed and dried.

[0034] Step 3: Activation process: The sensitized CNTs were placed in a mixed solution of PdCl2 (0.25 g / L) and HCl (5 ml / L) and sonicated for 30 min, then filtered, washed and dried.

[0035] Step 4: Magnetization process: Dissolve 1g of ferrous chloride tetrahydrate and 1.5g of ferric chloride hexahydrate in 100ml of deionized water, add 0.25g of activated CNTs and disperse by ultrasonication, then slowly add 5% ammonia solution until no more precipitate forms, ultrasonically bathe at 60℃ for 30min, filter, wash and dry to obtain magnetized CNTs; then add PSS to 50ml of deionized water and ultrasonically treat for 30min to obtain a 0.02g / mL PSS aqueous solution; add the above magnetized CNTs to 10ml of PSS aqueous solution at a mass ratio of 1:4, ultrasonically treat for 30min and then magnetically stir for 24h, then centrifuge at 15000r / min for 15min each time, for a total of 5 centrifugations to remove upper impurities and unreacted substances, quench with liquid nitrogen after washing and freeze-dry to obtain magnetic PSS@CNT powder.

[0036] Step 5: Dissolve a certain amount of PS masterbatch in tetrahydrofuran, add magnetic PSS@CNT powder at a volume ratio of 1:8 with PS masterbatch, sonicate for 30 min, and let stand for 20 h to obtain a uniformly dispersed CNTs-foaming mold suspension with a total concentration of 0.03 g / L.

[0037] Step 6: Place the CNTs-foaming mold suspension into a container covered by a magnetic field, immerse the copper foil in the suspension for 30 minutes, then pull it up in the direction of the magnetic field to cover the copper foil with a thin film, and let it stand in the magnetic field for 15 minutes, then put it in a drying oven to dry, and obtain the copper foil-foaming mold film unit.

[0038] Step 7: Stack 100 copper foil-foamed film units obtained in Step 6 layer by layer, cut them, and then place them in a graphite mold. Then, heat them at 950℃, 50MPa pressure, and a vacuum degree of 2×10⁻⁶.-3 Hot pressing and sintering at Pa for 1 hour (including 45 minutes of heating and 15 minutes of holding) yields a block material.

[0039] Experimental tests showed that the axial tensile strength of the obtained oriented CNTs / Cu composite material was 346.4 MPa and the electrical conductivity was 98.561 IACS.

[0040] Comparative Example

[0041] Step 6 does not use a magnetic field; other operations are the same as in the embodiment.

[0042] Experimental tests showed that the axial tensile strength of the obtained non-oriented CNTs / Cu composite material was 295.5 MPa, and the electrical conductivity was 96.61 IACS.

[0043] As can be seen above, the reinforcement efficiency of the reinforcing phase is improved by directional treatment of one-dimensional carbon nanotubes.

[0044] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing layered oriented CNTs / Cu composite materials by lost foam sintering, characterized in that: Includes the following steps: 1) After CNTs were successively oxidized, sensitized and activated, their surfaces were magnetically loaded and treated with hydrophilic polymers by coprecipitation. After repeated centrifugation and filtration, and drying, modified CNTs were obtained. 2) Dissolve a certain amount of PS masterbatch in tetrahydrofuran, then add the modified CNTs to the solution, disperse by ultrasonication, filter and let stand to obtain a uniformly dispersed CNTs-foaming mold suspension. 3) Immerse the copper foil in the CNTs-foaming mold suspension obtained in step 2) and place it in a magnetic field. Then, use a high magnetic flux magnetic field-assisted lifting method to coat the copper foil along the direction of the magnetic field to obtain copper foil-foaming mold film unit. 4) Stack the copper foil-foamed film units obtained in step 3) layer by layer, cut them and encapsulate them in a graphite mold for hot pressing and sintering to obtain the layered oriented CNTs / Cu composite material.

2. The method for preparing layered oriented CNTs / Cu composite materials by lost foam assisted sintering according to claim 1, characterized in that: In step 1), the oxidation treatment involves soaking CNTs in a mixture of H2SO4 and HNO3 at a volume ratio of 3:1 for 4 hours; the sensitization treatment involves sonicating the oxidized CNTs in a 10 ml / L HCl solution containing 0.1 mol / L SnCl2 for 30 minutes; and the activation treatment involves sonicating the sensitized CNTs in a 5 ml / L HCl solution containing 0.25 g / L PdCl2 for 30 minutes.

3. The method for preparing layered oriented CNTs / Cu composite materials by lost foam assisted sintering according to claim 1, characterized in that: The magnetic loading and hydrophilic polymer treatment described in step 1) involves dissolving 1g of ferrous chloride tetrahydrate and 1.5g of ferric chloride hexahydrate in 100ml of deionized water, adding 0.25g of activated and dried CNTs and ultrasonically dispersing them, then adding a 5% ammonia solution until no more precipitate forms, and then bathing in a water bath at 60℃ for 30min. After that, adding a 0.02g / mL PSS aqueous solution at a mass ratio of 1:4 with the CNTs used, ultrasonically treating for 30min, and then magnetically stirring for 24h.

4. The method for preparing layered oriented CNTs / Cu composite materials by lost foam assisted sintering according to claim 1, characterized in that: In step 2), the volume ratio of PS masterbatch to modified CNTs is 8:1; the total concentration of the resulting CNTs-foaming mold suspension is 0.03 g / L.

5. The method for preparing layered oriented CNTs / Cu composite materials by lost foam assisted sintering according to claim 1, characterized in that: Step 3) The magnetic induction intensity of the magnetic field is 1~2T.

6. The method for preparing layered oriented CNTs / Cu composite materials by lost foam assisted sintering according to claim 1, characterized in that: Step 4) The hot pressing sintering temperature is 900-1000℃, the time is 1 hour, and the vacuum degree is maintained at 2×10⁻⁶. -3 Pa, pressure maintained at 50 MPa.

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