CN109957674B - Preparation of CNTs-GR/Cu matrix composites based on directional cracking of CNTs under particle protection - Google Patents

Abstract

The invention relates to a method for preparing a CNTs-GR/Cu-based composite material based on directional cracking of CNTs under the protection of particles, and belongs to the technical field of nanocomposite materials. The method of the invention is mainly based on the protection of the solid particles nested on the surface of CNTs, the CNTs exposed at both ends are cleaved in a special cleavage solution, and the GR formed by the cleavage at both ends and the uncleaved CNTs in the middle pass through C- The C bonds are connected to each other to realize the effective combination of CNTs and GR, and the unique two-dimensional wrinkled surface of GR is used to increase the contact area with the copper matrix, improve the bonding strength of the interface, and effectively transmit the load. Cu-based composites exhibit more excellent properties.

Description

Preparation of CNTs-GR/Cu Matrix Composites Based on Directional Cracking of CNTs under Particle Protection method of feeding

technical field

The invention relates to a method for preparing a CNTs-GR/Cu matrix composite material based on the directional cracking of CNTs under the protection of particles, and belongs to the technical field of nanocomposite materials.

Background technique

The matrix properties of discontinuous reinforced metal matrix composites (DRMMCs) are improved under the action of a single reinforcement (ceramic particles, short fibers). In recent years, the adjustment of the microstructure of DRMMCs to optimize their comprehensive properties has become the focus of research, and the synergistic effect of multi-hybrid enhancers is one of the ways to break through this problem. It has been reported that hybrid reinforcements composed of carbon nanotubes (CNTs) and graphene (GR) can significantly improve the mechanical and electrical properties of epoxy resin composites. However, due to the poor wettability between the reinforcement and the matrix, and the simple solution mixing method cannot achieve the combination of GR and CNTs, the metal matrix composite cannot obtain a significant synergistic effect, resulting in the GR-CNTs hybrid reinforcement on the metal matrix. The enhancement effect is not good. Therefore, rational spatial design to realize the effective combination between the two enhancers is the key to exert the synergistic effect.

Kosynkin's research group reported that CNTs can be cracked layer by layer along the CNTs axial vector direction under the action of the lysis solution. By controlling the concentration of the lysis solution and the reaction time, the CNTs can be cracked to different degrees, and the binary hybrid GR can be obtained. +CNTs or all cleaved to GR. If the GR+CNTs obtained by this cracking method are dispersed into the metal matrix, it may be able to strengthen the matrix. However, due to the inherent properties of CNTs, the layers of the multi-walled structure are only bonded by small van der Waals forces, and the shear slip resistance between the layers is weak. When the load further increases, the outer layer will also be reduced The formed GR and the CNTs in the inner layer are detached. Therefore, the binary hybrid reinforcement obtained by this cleavage method still lacks the effective binding between GR and CNTs.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the present invention provides a method for preparing CNTs-GR/Cu based composite materials based on the directional cracking of CNTs under the protective effect of particles. The method mainly realizes the directional cracking of CNTs based on the protective effect of solid particles The GR-CNTs hybrid continuous reinforcement connected by C-C bonds, and the unique two-dimensional wrinkled surface of GR is used to increase the contact area with the copper matrix, improve the interfacial bonding strength, and effectively play the role of load transfer, so that the CNTs-GR/ Cu-based composites exhibit more excellent properties.

The object of the present invention is achieved through the following technical solutions.

A method for preparing CNTs-GR/Cu matrix composite material based on directional cracking of CNTs under the action of particle protection, the method steps are as follows:

(1) Acidification of CNTs

Prepare a mixed acid solution I of concentrated nitric acid (65%-68% by mass) and concentrated sulfuric acid (95%-98% by mass) with a volume ratio of 1:3 to 1:5; add CNTs to the mixed acid solution I , and stand at 60℃～80℃ for 2h～12h, washed and dried to obtain acidified CNTs;

(2) Solid particle nested CNTs

The acidified CNTs aqueous solution with the mass fraction of 0.01% to 0.1%, the metal salt solution with the concentration of 0.01 mol/L to 1 mol/L, and the solution M with the concentration of 0.5 mol/L to 3 mol/L were prepared respectively. According to the volume ratio of V _CNTs : V _{metal salt solution} : V _{solution M} = (0.1-0.5): 1: (1-3), the metal salt solution reacts with solution M to produce precipitation;

a) If the precipitates produced by the reaction are the same as the solid particles, the solids are directly collected to obtain CNTs/solid particle composites;

b) If the precipitate produced by the reaction is hydroxide and the solid particles are oxides, first collect the solids, and then heat and decompose to generate corresponding oxides to obtain CNTs/solid particle composites;

c) If the precipitate produced by the reaction is hydroxide and the solid particles are suboxide, after the precipitation reaction is completed, add glucose solution to reduce the corresponding suboxide, and then collect the solid to obtain the CNTs/solid particle composite;

(3) Directional cracking of CNTs

First, the CNTs/solid particle composite was added to the mixed acid solution II of concentrated phosphoric acid (83%-98% by mass) and concentrated sulfuric acid (95%-98% by mass) with a volume ratio of 1:5-1:10, Then add KMnO ₄ powder under ice bath condition, then heat to 60℃～80℃ and keep for 1h～3h, cool to room temperature, add excess hydrogen peroxide to remove KMnO ₄ reduction product MnO ₂ , filter, use the mass fraction not more than 5% The diluted hydrochloric acid solution was washed and dried to obtain GR-CNTs/solid particle composites;

Among them, the mass fraction of KMnO ₄ in the unit volume of concentrated H ₂ SO ₄ is 0.5% to 7%, and the mass ratio of CNTs to KMnO ₄ is 1:5 to 1:10;

(4) Removal of solid particles

Adding the GR-CNTs/solid particle complex into hydrofluoric acid for no less than 5 min, removing the solid particles remaining on the surface of the uncleaved CNTs, filtering, washing, and freeze-drying to obtain a GR-CNTs hybrid continuous reinforcement;

(5) Preparation of GR-CNTs/Cu matrix composites by powder metallurgy technology

The GR-CNTs hybrid continuous reinforcement and the copper-based powder were mixed uniformly by ball milling, and then placed under the conditions of 500℃～900℃ and 30MPa～300MPa for 0.5h～1h, and the GR-CNTs/Cu matrix composite material was obtained.

In step (1), the CNTs are double-walled CNTs or/and multi-walled CNTs.

In step (2), the metal salt solution is a water-soluble salt solution of Ba, Ag, Al or Cu, which can be BaCl ₂ , Ba(NO ₃ ) ₂ , AgNO ₃ , AlCl ₃ , Al(NO ₃ ) ₃ , Al ₂ (SO ₄ ) ₃ , CuCl ₂ , Cu(NO ₃ ) ₃ or CuSO ₄ , solution M is a water-soluble salt solution containing Cl-, SO ₄ ² - or OH- or NH ₃ ·H ₂ O, CNTs/ The solid particles in the solid particle composite may be AgCl, BaSO ₄ , Al ₂ O ₃ , CuO or Cu ₂ O.

In step (3), the CNTs/solid particle complex is stirred in the mixed acid solution II for 0.5 h to 1 h, and then KMnO ₄ powder is added.

In step (5), the particle size of the copper-based powder is 100 meshes to 500 meshes, and the copper-based powder is pure copper powder, mixed powder of copper powder and other metal powders, or copper alloy powder; GR-CNTs are mixed The mass fraction of the continuous reinforcement in the copper-based powder is 0.1wt%~2wt%; in the ball milling mixing process, the ball to material ratio is 5:1~20:1, the ball milling speed is 100r/min~250r/min, and the ball milling time is 0.5 h～12h.

Beneficial effects:

The method of the invention is mainly based on the protection of the solid particles nested on the surface of the CNTs, the CNTs exposed at both ends are cleaved in a special cleavage solution, and the GR formed by the cleavage at both ends and the uncleaved CNTs in the middle pass through C-C bonds. Connected to each other to realize the effective combination of CNTs and GR, and use the unique two-dimensional wrinkled surface of GR to increase the contact area with the copper-based matrix, improve the interface bonding strength, and effectively play the role of transferring loads, so that the CNTs-GR/Cu-based Composite materials exhibit better performance.

Description of drawings

FIG. 1 is an HRTEM (high-resolution transmission electron microscope) image of the acidified CNTs in Example 1. FIG.

FIG. 2 is a SEM (scanning electron microscope) image of the CNTs-GR/Al ₂ O ₃ composite in Example 1. FIG.

FIG. 3 is an HRTEM image of the CNTs-GR hybrid continuous reinforcement in Example 1. FIG.

FIG. 4 is a SEM image of the CNTs-GR/Cu ₂ O composite in Example 2. FIG.

FIG. 5 is a TEM image of the CNTs-GR hybrid continuous reinforcement in Example 2. FIG.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, wherein, the methods are conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified.

In the following examples:

Concentrated nitric acid: 65wt%;

Concentrated sulfuric acid: 98wt%;

Concentrated phosphoric acid: 98wt%;

Multi-walled carbon nanotubes: 99.9% purity, O.D.×L: (20nm±5nm)×(2μm±0.5μm), Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences;

Scanning electron microscope: Nova Nano-450, FEI, USA;

Transmission electron microscope: Tecnai G2-TF30, FEI, USA;

Performance characterization of the CNTs-GR/Cu matrix composites prepared in the examples: Vickers hardness test was carried out using the MC010 hardness tester of Shanghai Runyan Technology Company, wherein the loading load was 9.8N and the loading time was 15s; The Sigma-2008 conductivity meter of the company conducts the conductivity test, in which the test sample is a cylinder of Φ4mm×2mm; the tensile test is carried out at room temperature with a universal testing machine (AUTO-STC8800), wherein the strain rate is 2.0× 10-3s ^{-1 .}

Example 1

The specific steps for the preparation of CNTs-GR/Cu composites based on the directed cracking of CNTs under the protection of Al ₂ O ₃ particles are as follows:

(1) Acidification of CNTs

A mixed acid solution I of concentrated nitric acid and concentrated sulfuric acid with a volume ratio of 1:3 was prepared; 1 g of multi-walled CNTs was added to 240 mL of mixed acid solution I, and kept at 60 °C for 12 h, washed and dried to obtain acidified CNTs ,As shown in Figure 1;

(2) Al ₂ O ₃ particle-nested CNTs

Disperse 0.01 g of acidified CNTs into 50 mL of deionized water uniformly, then mix with 500 mL of Al(NO ₃ ) ₃ solution with a concentration of 0.01 mol/L and 500 mL of NaOH solution with a concentration of 0.5 mol/L, and collect the solid after reacting for 30 min. , and the solid was calcined at 250 °C for 1 h to obtain CNTs/Al ₂ O ₃ composite;

(3) Directional cracking of CNTs

First, 3g CNTs/Al ₂ O ₃ composite was added to the mixed acid solution II of concentrated phosphoric acid and concentrated sulfuric acid with a volume ratio of 1:5, stirred and mixed for 40 min, and then 3 g of KMnO ₄ powder was added under ice bath conditions, and then heated to 60°C and kept for 3 h, cooled to room temperature, poured the above reaction solution into 500 mL of 30% hydrogen peroxide, stirred for 0.5 h, filtered, washed with 5 wt% dilute hydrochloric acid solution, and dried to obtain GR-CNTs/Al ₂ O ₃ complex, as shown in Figure 2;

(4) Removal of Al ₂ O ₃ particles

The GR-CNTs/Al ₂ O ₃ composite was added into HF with a mass fraction of 3% and etched for 30 min to remove the remaining Al ₂ O ₃ particles on the surface of the uncleaved CNTs, filtered, washed, and freeze-dried to obtain a mixed GR-CNTs Continuous reinforcement, as shown in Figure 3;

(5) Preparation of GR-CNTs/Cu composites by powder metallurgy technology

Mix the GR-CNTs hybrid continuous reinforcement and pure copper powder with a particle size of 300 mesh to 500 mesh according to the mass ratio of 0.4:100, and add ball milling beads according to the ball-to-material ratio of 10:1, and then ball-mill at 250r/min 0.5h; then the ball-milled mixed powder was placed in a graphite mold, and hot-pressed and sintered at 700°C and 50MPa for 1h to obtain a GR-CNTs/Cu composite material.

It can be seen from Figure 1 that the acidification of CNTs can remove the impure substances of the raw CNTs and the amorphous carbon layer on its outer wall, and form high-energy active sites under the oxidation of strong acid, which is the subsequent nesting of solid particles on the surface of CNTs. Provides nucleation sites. Figure 2 shows that under the action of the special lysing solution, the CNTs exposed at both ends of the solid particles are decomposed layer by layer along the axis of the tube wall from the outside to the inside due to the lack of particle protection, as indicated by the arrows in the figure. Under the etching effect of 3% HF solution, the solid particles were completely removed, and the two ends of the CNTs were cracked to form a multi-layered GR with obvious wrinkles, which effectively increased the contact area between the CNTs and the pure copper powder matrix. In the region, the CNTs were not cleaved and maintained their original one-dimensional tubular structure (as shown by the arrow in Figure 3), so that the GR formed by the cleavage at both ends and the uncleaved CNTs in the middle were connected to each other through C-C bonds.

Example 2

The specific steps to prepare CNTs-GR/Cu-Ti composites based on the directional cracking of CNTs under the protection of Cu ₂ O particles are as follows:

(1) Acidification of CNTs

A mixed acid solution I of concentrated nitric acid and concentrated sulfuric acid with a volume ratio of 1:5 was prepared; 1 g of multi-walled CNTs was added to 200 mL of mixed acid solution I, and kept at 80 °C for 2 h, washed and dried to obtain acidified CNTs ;

(2) Cu ₂ O particles nested CNTs

Disperse 0.05g of acidified CNTs into 50mL of deionized water uniformly, and then mix with 100mL of Cu(NO ₃ ) ₂ solution with a concentration of 0.5mol/L and 300mL of NaOH solution with a concentration of 3mol/L, and then add 10mL after the reaction for 5min. A glucose solution with a concentration of 0.45 mol/L was continued to react for 45 min, and the solid was collected to obtain CNTs/Cu ₂ O composite powder;

(3) Directional cracking of CNTs

First, 4g CNTs/Cu ₂ O composite was added to the mixed acid solution II of concentrated phosphoric acid and concentrated sulfuric acid with a volume ratio of 1:10, then 5g KMnO ₄ powder was added under ice bath conditions, and then heated to 80 °C and kept for 1 h , cooled to room temperature, poured the above reaction solution into 1000 mL of 30% hydrogen peroxide, stirred for 0.5 h, filtered, washed with 5 wt% dilute hydrochloric acid solution, and dried to obtain GR-CNTs/Cu ₂ O composite, as shown in Figure 4 shown;

(4) Removal of Cu ₂ O particles

The GR-CNTs/Cu ₂ O composite was added to hydrofluoric acid with a mass fraction of 3% and etched for 30 min to remove the remaining Cu ₂ O particles on the surface of the uncleaved CNTs, filtered, washed, and freeze-dried to obtain a hybrid GR-CNTs. Continuous reinforcement, as shown in Figure 5;

(5) Preparation of GR-CNTs/Cu-Ti composites by powder metallurgy technology

The GR-CNTs hybrid continuous reinforcement and the Cu-1.0wt% Ti alloy powder with a particle size of 100 meshes to 300 meshes were mixed in a mass ratio of 0.3:100, and ball milling beads were added in a ball-to-material ratio of 20:1, and then Ball-milled at 100 r/min for 12 h; then put the ball-milled mixed powder in a graphite mold, and hot-pressed and sintered at 700 °C and 50 MPa for 0.5 h to obtain a GR-CNTs/Cu-Ti composite material.

Figure 4 shows that the CNTs exposed at both ends of the Cu ₂ O particles are cracked layer by layer from the outside to the inside along the axis of the tube wall due to the lack of protection by solid particles, and are completely opened, as indicated by the arrows in the figure. Under the etching effect of HF, the Cu ₂ O particles were completely removed, and the two ends of the CNTs were cracked to form a multi-layered GR with obvious wrinkles, which effectively increased the contact area between the CNTs and the Cu-1.0wt% Ti alloy powder. In the protected area of the solid particles, the CNTs did not cleave and maintained their original one-dimensional tubular structure (as shown by the arrows in Figure 5), so that the GR formed by cleavage at both ends and the uncleaved CNTs in the middle were connected to each other through CC bonds.

Comparative Example 1

Mix 0.05g GR, 0.05g CNTs and 25g pure copper powder with a particle size of 300 mesh to 500 mesh, add ball milling beads according to the ball-to-material ratio of 10:1, and then ball-mill at 250r/min for 0.5h; The mixed powder was placed in a graphite mold, and hot-pressed and sintered at 700 °C and 50 MPa for 1 h to obtain a discontinuous hybrid reinforced GR-CNTs/Cu composite.

Comparative Example 2

Mix 0.04g GR, 0.04g CNTs and 24g Cu-1.0wt% Ti alloy powder with a particle size of 100 mesh to 300 mesh, add ball milling beads at a ratio of 20:1, and then ball mill at 100r/min for 12h Then, the ball-milled mixed powder was placed in a graphite mold, and hot-pressed and sintered at 700 °C and 50 MPa for 0.5 h to obtain a discontinuous hybrid reinforced GR-CNTs/Cu-Ti composite.

Performance tests were performed on the composite materials prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2, respectively, and the results are shown in Table 1. According to the test results in Table 1, the GR-CNTs hybrid continuous reinforcement prepared by the present invention can more effectively enhance the strength and hardness of the copper-based matrix than the discontinuous hybrid reinforcement. It can be seen from the TEM detection results that the GR formed by cleavage at both ends of CNTs is effectively combined with the uncleaved CNTs in the middle through C-C bonds, and the unique two-dimensional plane of GR is used to increase the contact area with the copper matrix and improve the interface bonding. The strength of the hybrid continuous CNTs-GR/Cu matrix composite shows more excellent performance. The slight decrease in the electrical conductivity of the hybrid continuous CNTs-GR/Cu matrix composites is due to the fact that the GR formed at the cleaved end increases the interfacial contact area with the matrix, thereby causing scattering and hindering the electrons in the directional migration process.

Table 1

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. a method for preparing CNTs-GR/Cu based composite material based on directional cracking of CNTs under particle protection, is characterized in that: the method steps are as follows, (1) Mix concentrated nitric acid and concentrated sulfuric acid according to the volume ratio of 1:3～1:5 to prepare mixed acid solution I, add CNTs to mixed acid solution I, and stand at 60℃～80℃ for 2h～ 12h, washed and dried to obtain acidified CNTs; (2) Prepare an acidified CNTs aqueous solution with a mass fraction of 0.01% to 0.1%, a metal salt solution with a concentration of 0.01 mol/L to 1 mol/L, and a solution M with a concentration of 0.5 mol/L to 3 mol/L, respectively. The three solutions are mixed according to the volume ratio of (0.1-0.5): 1: (1-3), and the metal salt solution reacts with the solution M to produce precipitation; a) If the precipitates produced by the reaction are the same as the solid particles, the solids are directly collected to obtain CNTs/solid particle composites; b) If the precipitate produced by the reaction is hydroxide and the solid particles are oxides, first collect the solids, and then heat and decompose to generate corresponding oxides to obtain CNTs/solid particle composites; c) If the precipitate produced by the reaction is hydroxide and the solid particles are suboxide, after the precipitation reaction is completed, first add glucose solution to reduce the corresponding suboxide, and then collect the solid to obtain the CNTs/solid particle composite; (3) Concentrated phosphoric acid and concentrated sulfuric acid are mixed according to the volume ratio of 1:5 to 1:10 to prepare mixed acid solution II. First, CNTs/solid particle complexes are added to mixed acid solution II, and then KMnO is added under ice bath conditions. ₄ powder, then heated to 60℃～80℃ and kept for 1h～3h, after cooling to room temperature, add excess hydrogen peroxide, then filter in turn, wash with dilute hydrochloric acid solution with a mass fraction of not more than 5%, and dry to obtain GR-CNTs/ Solid particle composite; wherein, the mass fraction of KMnO ₄ in a unit volume of concentrated H ₂ SO ₄ is 0.5% to 7%, and the mass ratio of CNTs to KMnO ₄ is 1:5 to 1:10; (4) adding the GR-CNTs/solid particle composite into hydrofluoric acid for no less than 5 minutes, filtering, washing, and freeze-drying to obtain a GR-CNTs hybrid continuous reinforcement; (5) First mix the GR-CNTs hybrid continuous reinforcement and the copper-based powder uniformly by ball milling, and then place the GR-CNTs/Cu-based powder under the conditions of 500℃～900℃ and 30MPa～300MPa for 0.5h～1h. composite material. 2. the method for preparing CNTs-GR/Cu-based composite material based on the directional cracking of CNTs under particle protection according to claim 1, is characterized in that: in step (1), described CNTs are double-walled CNTs or/and multi-walled CNTs Wall CNTs. 3. the method for preparing CNTs-GR/Cu based composite material based on directional cracking of CNTs under particle protection according to claim 1, is characterized in that: in step (2), described metal salt solution is Ba, Ag, Al Or the water-soluble salt solution of Cu, the solution M is a water-soluble salt solution containing Cl ^- , SO ₄ ^2- or OH ^- or NH ₃ ·H ₂ O. 4. The method for preparing CNTs-GR/Cu-based composite material based on directional cracking of CNTs under particle protection according to claim 1, wherein the solid particles in the CNTs/solid particle composite are AgCl, BaSO ₄ , Al ₂ O ₃ , CuO or Cu ₂ O. 5. The method for preparing CNTs-GR/Cu-based composite material based on directional cracking of CNTs under particle protection according to claim 1, characterized in that: in step (3), the CNTs/solid particle composite is in the mixed acid solution II After stirring for 0.5h～1h, add KMnO ₄ powder. 6. The method for preparing CNTs-GR/Cu-based composite material based on directional cracking of CNTs under particle protection according to claim 1, characterized in that: in step (5), the copper-based powder is pure copper powder, copper Mixed powder with other metal powder or copper alloy powder. 7. The method for preparing CNTs-GR/Cu-based composite material based on directional cracking of CNTs under particle protection according to claim 1, characterized in that: in step (5), the particle size of the copper-based powder is 100 meshes to 100 meshes 500 mesh. 8. The method for preparing CNTs-GR/Cu-based composite material based on directional cracking of CNTs under particle protection according to claim 1, characterized in that: in step (5), the GR-CNTs hybrid continuous reinforcement accounts for the copper-based powder The mass fraction of the body is 0.1 wt % to 2 wt %. 9. The method for preparing CNTs-GR/Cu-based composite material based on directional cracking of CNTs under particle protection according to claim 1, characterized in that: in step (5), GR-CNTs are mixed with continuous reinforcement and copper-based powder During the mixing process of body ball milling, the ratio of ball to material is 5:1~20:1, the ball milling speed is 100r/min~250r/min, and the ball milling time is 0.5h~12h.

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