CN116240421B - Method for preparing carbon polymer dot reinforced copper-based composite material based on space confinement - Google Patents

Abstract

The invention relates to a method for preparing a carbon polymer dot reinforced copper-based composite material based on space limitation, which comprises the steps of cracking a carbon nano tube by a nitric acid condensation reflux method to obtain CPDs (chlorinated polyethylene) as a reinforcement, adopting a molecular-level blending method to prepare copper particles with a porous skeleton structure as a matrix, dispersing the CPDs in holes of the copper particles of the porous skeleton by an electrostatic adsorption method, then carrying out encapsulation closed-pore treatment in a ball milling mode, further improving the dispersibility and interface bonding strength of the CPDs, and finally preparing the CPDs/Cu block composite material with excellent mechanical strength and plasticity by spark plasma sintering; the ultimate tensile strength of the CPDs/Cu block composite material finally prepared by the invention reaches 344MPa, the elongation reaches 35%, the ductility and the strength of the composite material are improved, and the excellent matching effect of the strength and the plasticity is achieved.

Description

A method for preparing carbon polymer dot reinforced copper-based composite materials based on spatial confinement

Technical Field

The invention belongs to the technical field of copper-based composite material preparation and powder metallurgy, and specifically relates to a method for preparing carbon polymer dot-reinforced copper-based composite material based on spatial confinement.

Background technique

Carbon polymer dots (CPDs) are a new type of zero-dimensional carbon nanomaterial that has emerged in recent years. They are composed of surface-rich functional groups/polymer chains and a core carbon core. Compared with one-dimensional carbon nanotubes and two-dimensional graphene, CPDs have good water solubility, are evenly dispersed in polar solutions, and have outstanding mechanical and electrical properties. They are considered to be excellent reinforcements for copper-based composites. From the perspective of composite material preparation technology, CPDs-reinforced copper (CPDs/Cu) composites are currently generally prepared by high-energy ball milling. This method is simple and has a short process, and is considered to be the most efficient method. However, according to existing research reports, CPDs/Cu composites prepared by high-energy ball milling generally have the disadvantages of not having a prominent reinforcement effect and not matching the strength and plasticity of the composites. With the deepening of research, it is found that CPDs are easily segregated in the grain boundary area of the matrix and form submicron-scale CPDs clusters. These cluster defects will cause a large number of hole defects in the matrix, reduce the interfacial bonding strength between CPDs and the matrix, and become a stress concentration area during loading, thereby forming microcracks and causing premature failure of the material. Although hydrothermal synthesis and nanoscale dispersion methods can improve the dispersibility and interface bonding properties of CPDs to a certain extent, these preparation methods are complex, have a long preparation process, and are prone to introducing other inclusions. So far, research on the preparation of high-performance CPDs/Cu composites still lacks an effective method to solve the CPDs agglomeration defects and obtain good interface bonding.

Summary of the invention

In response to the current problems, the present invention provides a method for preparing carbon polymer dot reinforced copper-based composite materials based on spatial confinement, wherein carbon nanotubes are cracked by concentrated nitric acid condensation reflux method to obtain CPDs as a reinforcement, and copper particles with a "porous skeleton" structure are prepared as a matrix by molecular blending method and specific reduction process, and CPDs are dispersed in the pores of the "porous skeleton" copper particles by electrostatic adsorption, and then "encapsulated" closed-pore treatment is performed by ball milling to "encapsulate" CPDs in copper particles, thereby further improving the dispersibility and interface bonding strength of CPDs, and finally, a bulk composite material with CPDs uniformly distributed in copper grains and excellent mechanical strength and plasticity is prepared by spark plasma sintering.

The purpose of the present invention is achieved through the following technical solutions:

A method for preparing a carbon polymer dot reinforced copper-based composite material based on spatial confinement, the specific steps are as follows:

(1) Preparation of carbon polymer dots

CNTs were mixed with concentrated nitric acid and condensed and refluxed at 100°C to 140°C for 36h to 72h. After the reaction of the mixed solution was completed, 0.2mol/L to 1.0mol/L NaOH solution was added dropwise to neutralize the mixture, and the mixture was filtered. The filtrate at the bottom of the bottle was dialyzed using a 1kDa dialysis bag and freeze-dried to obtain CPDs.

(2) Preparation of “porous skeleton” copper matrix particles

The cuprous oxide micron particles are prepared by molecular blending method, and the "porous skeleton" copper particle powder is generated after heating and reduction;

(3) Adsorption and "encapsulation" treatment

The CPDs prepared in step (1) are added to deionized water for ultrasonic dispersion treatment, and then the above-mentioned "porous skeleton" copper particle powder is added, the pH value of the solution is adjusted to 3.0-4.0, stirred and allowed to settle, and then filtered and dried to obtain CPDs/Cu particles, and the CPDs/Cu powder is subjected to "encapsulation" closed-cell treatment by high-energy ball milling to obtain flaky CPDs/Cu composite powder;

(4) Consolidation treatment of CPDs/Cu composite powder

The CPDs/Cu composite powder was consolidated by spark plasma sintering (SPS), and a CPDs/Cu bulk composite material was obtained after furnace cooling.

The CNTs in step (1) are -COOH-treated CNTs, which have a length of 10 μm to 20 μm and a width of 10 nm to 20 nm and are commercially available; the mass fraction of concentrated nitric acid is 65% to 68%, and the mass ratio of CNTs to concentrated nitric acid is 1:500 to 1:1000.

The specific steps of preparing cuprous oxide micron particles by the molecular blending method in step (2) are as follows: 15.6 g of cupric acetate is dissolved in 200-2000 mL of pure water, and then 100 mL of a sodium hydroxide solution with a concentration of 0.2 mol/L-2 mol/L is added. After the solution turns dark blue and becomes viscous, 10-50 mL of a glucose solution with a concentration of 0.8 mol/L is added, and the beaker is placed in a water bath at 80° C. After the solution turns dark red, it is taken out and allowed to stand, and the water is changed 2-3 times, and then filtered and dried to obtain cuprous oxide micron particles.

In step (2), the heating reduction is carried out in a N ₂ /H ₂ mixed atmosphere, the temperature is raised to 300° C. to 500° C. and then kept at this temperature for 180 min to 300 min; wherein the volume fraction of hydrogen is 10% and the rest is nitrogen.

In step (3), the ultrasonic treatment power is 400W to 500W, the time is 30min to 60min, and hydrochloric acid with a concentration of 0.5mol/L to 2mol/L is added dropwise to adjust the pH value.

In step (3), the mass ratio of CPDs to "porous skeleton" copper particles is 1:50 to 1000.

The rotation speed of the high-energy ball milling process in step (3) is 200 r/min to 450 r/min, and the ball milling time is 3 h to 8 h.

Step (4) uses spark plasma sintering (SPS) to heat the temperature to 500°C to 700°C at a heating rate of 100°C/min, with a holding time of 5 to 8 minutes and a sintering pressure of 50 MPa.

Beneficial effects of the present invention:

(1) The CPDs and the "porous skeleton" copper particles of the present invention are initially dispersed and confined in the pores of the copper particles through electrostatic adsorption. The ball milling "encapsulation" closed-pore treatment enables the CPDs to obtain a secondary dispersion effect. The CPDs are enclosed inside the grains and the CPDs-Cu interface bonding strength is improved at the same time, so that the strengthening effect of CPDs is better exerted, and the defect of mismatch between strength and plasticity of the CPDs/Cu composite material is effectively solved.

(2) The method of the present invention is simple, has a short preparation process, is highly universal, is applicable to a variety of copper-based materials, and has good application prospects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a TEM image of carbon polymer dots CPDs prepared in Example 1;

FIG2 is a SEM image of cuprous oxide particles prepared by the molecular-level blending method in step (2) of Example 1;

FIG3 is a SEM image of the “porous skeleton” copper particle powder prepared in step (2) of Example 1;

FIG4 is a SEM image of the CPDs/Cu composite powder after the “encapsulation” treatment in step (3) of Example 1;

FIG5 is a SEM image of the CPDs/Cu bulk composite material prepared in step (4) of Example 1 after corrosion;

FIG6 is a SEM image of the fracture surface of the CPDs/Cu bulk composite material prepared in step (4) of Example 1 after stretching;

FIG7 is a TEM image of the CPDs/Cu bulk composite material prepared in step (4) of Example 1;

FIG8 is an enlarged TEM image of carbon polymer dots in the CPDs/Cu bulk composite material prepared in step (4) of Example 1;

FIG9 is a SEM image of the “porous skeleton” copper particles prepared in step (2) of Example 2;

Figure 10 is the stress-strain diagram of CPDs/Cu bulk composite material.

Detailed ways

The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The specific methods in the invention are conventional methods unless otherwise specified, and the raw materials involved can be purchased from commercial channels unless otherwise specified.

The raw materials used in the examples are as follows:

Carbon nanotubes (CNTs): purity 98%, length 2μm-20μm, width 10nm-20nm, Chengdu Organic Chemistry Co., Ltd.; Sodium hydroxide (NaOH): purity 96%, Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.;

Concentrated nitric acid (HNO3): analytical grade (65%-68%), Sichuan Xilong Science Co., Ltd.;

Concentrated hydrochloric acid (HCl): analytical grade, Sichuan Xilong Science Co., Ltd.;

Copper acetate (Cu ₂ (CH ₃ COO) ₄ ): purity 99%, Shanghai MacLean Biochemical Technology Co., Ltd.;

Anhydrous glucose: analytical grade, Shanghai MacLean Biochemical Technology Co., Ltd.;

Anhydrous ethanol: analytical grade, Tianjin Fengchuan Reagent Co., Ltd.;

Constant temperature water bath: HH-2J, Changzhou Langyue Instrument Manufacturing Co., Ltd.

Oil bath pot: DF-101SH, Shanghai Lichen Bangxi Instrument Co., Ltd.;

High energy ball mill: PM 400, Lech, Germany;

Scanning electron microscope: JEOL JSM 7200F, OR, JAPAN;

Transmission electron microscope: Tecnai G2 F20, FEI, Hillsboro, OR, USA;

Characterization of mechanical properties of CPDs/Cu composites: The mechanical properties were tested using a universal tensile tester (AG-IS10KN) at a tensile rate of 0.2 mm/min at room temperature.

Example 1

A method for preparing a carbon polymer dot reinforced copper-based composite material based on spatial confinement, the specific steps are as follows:

(1) Preparation of carbon polymer dots

CNTs and a concentrated nitric acid solution with a mass fraction of 65% were accurately weighed at a mass ratio of 1:1000 and poured into a round-bottom flask. The mixture was condensed and refluxed at 100°C for 72 hours. After the reaction was completed, a 0.2 mol/L NaOH solution was added dropwise to neutralize the mixture and filtered. The filtrate at the bottom of the flask was dialyzed against water using a 1 kDa dialysis bag to remove NO ₃ ^- ions. The remaining liquid in the bag was freeze-dried to obtain CPDs.

(2) Preparation of “porous skeleton” copper particles

Cuprous oxide particles prepared by a molecular-level blending method: 15.6 g of cupric acetate was mixed into a beaker containing 200 mL of pure water and stirred evenly, and then 100 mL of a 2 mol/L sodium hydroxide solution was added. After the solution turned dark blue and viscous, 50 mL of a 0.8 mol/L glucose solution was added, and the beaker was placed in a water bath at 80° C., and after the solution turned dark red, it was taken out and allowed to stand, and the water was changed twice. After filtering, it was dried at 60° C. under vacuum conditions for 8 hours to obtain cuprous oxide particles;

The cuprous oxide particles were reduced at 300°C for 4 h in a N ₂ -10% H ₂ atmosphere to obtain a "porous skeleton" copper particle powder;

(3) Adsorption and "encapsulation" treatment

0.2 g of the CPDs prepared in step (1) was added to 100 mL of deionized water for ultrasonic treatment at a power of 450 W for 45 min. Then, 10 g of the "porous skeleton" copper particle powder was added to the above liquid, and 0.5 mol/L of hydrochloric acid was added dropwise to adjust the solution pH to 3.0. The CPDs and the "porous skeleton" copper particles were subjected to electrostatic adsorption treatment. After stirring for 45 min, the mixture was allowed to stand for 2 h for precipitation, filtration and drying to obtain CPDs/Cu particles. Subsequently, the CPDs/Cu particles were mixed at a ball-to-material ratio of 1:10, and dispersed in a ball mill containing 60 mL of anhydrous ethanol for high-energy ball milling. The above particles were subjected to "encapsulation" closed-pore treatment by ball milling at a speed of 200 r/min for 8 h to obtain flaky CPDs/Cu composite powders.

(4) Consolidation treatment of CPDs/Cu composite powder

The "encapsulated" CPDs/Cu composite powder was placed in a graphite mold with an inner diameter of 20 mm and sintered using an SPS device with a heating rate of 100°C/min, a sintering temperature of 500°C, a sintering pressure of 50 MPa, and a holding time of 5 min. After the holding period, it was cooled to room temperature and taken out to obtain a CPDs/Cu bulk composite material.

FIG1 is a TEM image of carbon polymer dots prepared in Example 1. It can be seen from the figure that the CPDs are nearly spherical in shape, clear lattice fringes can be observed, and the interplanar spacing is 0.21 nm.

FIG2 is a SEM image of cuprous oxide particles prepared by the molecular blending method in step (2) of Example 1. It can be seen from the figure that the Cu ₂ O particles prepared by the molecular blending method are nearly square, with an almost flat surface and no holes, and the particle size is 1 μm-3 μm.

Figure 3 is a SEM image of the "porous skeleton" copper particle powder prepared in step (2) of Example 1. It can be seen from the figure that after reduction, the surface of the Cu particles becomes uneven and has many holes. The formation of these holes can make CPDs more distributed in the holes during adsorption, thereby enhancing the bonding between CPDs and the Cu matrix.

FIG4 is a SEM image of the CPDs/Cu composite powder after the “encapsulation” treatment in step (3) of Example 1. It can be seen from the figure that after “ball milling encapsulation”, the Cu particles become completely flaky, and the average particle size is about 2.8 μm.

FIG5 is a SEM image of the CPDs/Cu bulk composite material prepared in step (4) of Example 1 after corrosion. It can be seen from the image that the grain boundaries of the composite bulk are clearly visible after corrosion.

Figure 6 is an SEM image of the fracture of the CPDs/Cu bulk composite material prepared in step (4) of Example 1 after stretching. From the figure, it can be observed that the dimples in the fracture of the CPDs/Cu bulk composite material are clearly visible and relatively evenly distributed. In particular, the dimple "tear ridge" can be observed at the position indicated by the arrow, indicating that the composite material has good plasticity.

FIG. 7 is a TEM image of the CPDs/Cu bulk composite material prepared in step (4) of Example 1. From the image, it can be observed that a large number of CPDs are evenly distributed inside the Cu matrix grains.

Figure 8 is a high-resolution TEM image of the CPDs-Cu interface microstructure in the CPDs/Cu bulk composite material prepared in step (4) of Example 1. It can be observed from the image that the CPDs and Cu interfaces are tightly bonded without obvious defects.

Example 2

A method for preparing a carbon polymer dot reinforced copper-based composite material based on spatial confinement, the specific steps are as follows:

(1) Preparation of carbon polymer dots

CNTs and a concentrated nitric acid solution with a mass fraction of 66% were accurately weighed in a mass ratio of 1:500 and poured into a round-bottom flask. The mixture was condensed and refluxed at 140°C for 36 hours. After the reaction was completed, a 1 mol/L NaOH solution was added dropwise for neutralization and filtration. The filtrate at the bottom of the flask was dialyzed against water using a 1 kDa dialysis bag to remove NO ₃ ^- ions. The remaining liquid in the bag was freeze-dried to obtain CPDs.

(2) Preparation of “porous skeleton” copper particles

Cuprous oxide particles prepared by a molecular-level blending method: 15.6 g of cupric acetate was mixed into a beaker containing 500 mL of pure water and stirred evenly, and then 100 mL of a 1 mol/L sodium hydroxide solution was added. After the solution turned dark blue and viscous, 10 mL of a 0.8 mol/L glucose solution was added, and the beaker was placed in a water bath at 80° C. After the solution turned dark red, it was taken out and allowed to stand, and the water was changed 3 times. After filtering, it was dried at 60° C. under vacuum conditions for 8 hours to obtain cuprous oxide particles;

The cuprous oxide particles were reduced at 500°C for 3 h in a N ₂ -10% H ₂ atmosphere to obtain a "porous skeleton" copper particle powder;

(3) Adsorption and "encapsulation" treatment

0.2 g of the CPDs prepared in step (1) was added to 300 mL of deionized water for ultrasonic treatment at a power of 500 W for 30 min. Then, 20 g of the "porous skeleton" copper particles were added to the above liquid, and 2 mol/L of hydrochloric acid was added dropwise to adjust the solution pH to 3.5. The CPDs and the "porous skeleton" copper particles were subjected to electrostatic adsorption treatment. After stirring for 45 min, the mixture was allowed to stand for 2 h for precipitation, filtration and drying to obtain CPDs/Cu particles. Subsequently, the CPDs/Cu particles were mixed at a ball-to-material ratio of 1:10, and dispersed in a ball mill containing 60 mL of anhydrous ethanol for high-energy ball milling. The above particles were subjected to "encapsulation" closed-pore treatment by ball milling at a speed of 450 r/min for 3 h to obtain flaky CPDs/Cu composite powders.

(4) Consolidation treatment of CPDs/Cu composite powder

The "encapsulated" CPDs/Cu composite powder was placed in a graphite mold with an inner diameter of 20 mm and sintered using an SPS device with a heating rate of 100°C/min, a sintering temperature of 600°C, a sintering pressure of 50 MPa, and a holding time of 8 min. After the holding period, it was cooled to room temperature and taken out to obtain a CPDs/Cu bulk composite material.

FIG9 is a SEM image of the “porous skeleton” copper particle powder prepared in step (2) of Example 2. After reduction, the pores on the surface of the Cu particles are significantly reduced or even disappear.

Example 3

A method for preparing a carbon polymer dot reinforced copper-based composite material based on spatial confinement, the specific steps are as follows:

(1) Preparation of carbon polymer dots

CNTs and a concentrated nitric acid solution with a mass fraction of 68% were accurately weighed at a mass ratio of 1:600 and poured into a round-bottom flask. The mixture was condensed and refluxed at 120°C for 48 hours. After the reaction was completed, a 0.5 mol/L NaOH solution was added dropwise for neutralization and filtration. The filtrate at the bottom of the flask was dialyzed against water using a 1 kDa dialysis bag to remove NO ₃ ^- ions. The remaining liquid in the bag was freeze-dried to obtain CPDs.

(2) Preparation of “porous skeleton” copper particles

Cuprous oxide particles prepared by a molecular-level blending method: 15.6 g of cupric acetate was mixed into a beaker filled with 2000 mL of pure water and stirred evenly, followed by adding 100 mL of a 0.2 mol/L sodium hydroxide solution, and after the solution turned dark blue and viscous, 30 mL of a 0.8 mol/L glucose solution was added, and the beaker was placed in a water bath at 80° C., and after the solution turned dark red, it was taken out and allowed to stand, and the water was changed twice, and after filtering, it was dried at 60° C. under vacuum conditions for 8 hours to obtain cuprous oxide particles;

The cuprous oxide particles were reduced at 400°C for 5 h in a N ₂ -10% H ₂ atmosphere to obtain a "porous skeleton" copper particle powder;

(3) Adsorption and "encapsulation" treatment

0.02 g of the CPDs prepared in step (1) was added to 100 mL of deionized water for ultrasonic treatment at a power of 400 W for 60 min. Then, 20 g of the "porous skeleton" copper particles were added to the above liquid, and 1 mol/L hydrochloric acid was added dropwise to adjust the solution pH to 4.0. The CPDs and the "porous skeleton" copper particles were subjected to electrostatic adsorption treatment. After stirring for 45 min, the mixture was allowed to stand for 2 h for precipitation, filtered and dried to obtain CPDs/Cu particles. Subsequently, the CPDs/Cu particles were mixed at a ball-to-material ratio of 1:10, and dispersed in a ball mill containing 60 mL of anhydrous ethanol for high-energy ball milling. The above particles were subjected to "encapsulation" closed-pore treatment by ball milling at a speed of 300 r/min for 5 h to obtain flaky CPDs/Cu composite powders.

(4) Consolidation treatment of CPDs/Cu composite powder

The "encapsulated" CPDs/Cu composite powder was placed in a graphite mold with an inner diameter of 20 mm and sintered using an SPS device with a heating rate of 100°C/min, a sintering temperature of 700°C, a sintering pressure of 50 MPa, and a holding time of 6 min. After the holding period, it was cooled to room temperature and taken out to obtain a CPDs/Cu bulk composite material.

Comparative Example 1

(1) CNTs and a concentrated nitric acid solution with a mass fraction of 65% were accurately weighed in a mass ratio of 1:1000 and poured into a round-bottom flask. The mixture was condensed and refluxed at 100°C for 72 hours. After the reaction was completed, a 0.2 mol/L NaOH solution was added dropwise to neutralize the mixture and filter it. The filtrate at the bottom of the flask was dialyzed against water using a 1 kDa dialysis bag to remove NO ₃ ^- ions. The remaining liquid in the bag was freeze-dried to obtain CPDs;

(2) Weigh 10 g of dendritic copper powder and put it into a ball mill filled with 60 mL of anhydrous ethanol, then weigh 0.2 g of CPDs and pour it into the ball mill, with a ball-to-material ratio of 1:10, and ball mill at a speed of 200 r/min for 8 h. After ball milling, filter and dry, and reduce at 300°C for 4 h in a _N2-10 % _H2 reducing atmosphere to obtain CPDs/Cu composite powder;

(3) The CPDs/Cu composite powder was placed in a graphite mold with an inner diameter of 20 mm and sintered using an SPS device with a heating rate of 100°C/min, a sintering temperature of 500°C, a sintering pressure of 50 MPa, and a holding time of 5 min. After the holding time was completed, the powder was cooled to room temperature and taken out to obtain a CPDs/Cu bulk composite material.

Comparative Example 2

(1) CNTs and a concentrated nitric acid solution with a mass fraction of 65% were accurately weighed in a mass ratio of 1:1000 and poured into a round-bottom flask. The mixture was condensed and refluxed at 100°C for 72 hours. After the reaction was completed, a 0.2 mol/L NaOH solution was added dropwise for neutralization and filtration. The filtrate at the bottom of the flask was dialyzed against water using a 1 kDa dialysis bag to remove NO ₃ ^- ions. The remaining liquid in the bag was freeze-dried to obtain CPDs;

(2) 15.6 g of copper acetate was mixed into a beaker containing 600 mL of pure water and stirred evenly. After dissolution, 0.2 g of CPDs was added and stirred for 5 min. Subsequently, 100 mL of 2 mol/L NaOH solution was added. After the solution turned dark blue and viscous, 50 mL of 0.8 mol/L glucose solution was evenly dissolved. The beaker was placed in a water bath at 80°C. After the solution turned dark red, it was taken out and allowed to stand. The water was changed 3 times and then filtered. The mixture was dried at 60°C under vacuum for 8 h. The mixture was heated to 300°C for reduction for 4 h in a _N2-10 % _H2 reducing atmosphere to obtain CPDs/Cu composite powder.

(3) The CPDs/Cu composite powder was placed in a graphite mold with an inner diameter of 20 mm and sintered using an SPS device with a heating rate of 100°C/min, a sintering temperature of 500°C, a sintering pressure of 50 MPa, and a holding time of 5 min. After the holding time was completed, the powder was cooled to room temperature and taken out to obtain a CPDs/Cu bulk composite material.

Comparative Example 3

(1) CNTs and a concentrated nitric acid solution with a mass fraction of 65% were accurately weighed in a mass ratio of 1:1000 and poured into a round-bottom flask. The mixture was condensed and refluxed at 140°C for 72 hours. After the reaction was completed, a 0.2 mol/L NaOH solution was added dropwise for neutralization and filtration. The filtrate at the bottom of the flask was dialyzed against water using a 1 kDa dialysis bag to remove NO ₃ ^- ions. The remaining liquid in the bag was freeze-dried to obtain CPDs;

(2) Weigh 10 g of dendritic copper powder and put it into a ball mill filled with 100 mL of anhydrous ethanol, then weigh 0.01 g of CPDs powder and pour it into the ball mill, with a ball-to-material ratio of 1:10, and ball mill at a speed of 200 r/min for 3 h, and then ball mill at a speed of 300 r/min for 5 h. After ball milling, filter and dry, and heat to 300 °C in a _N2-10 % _H2 reducing atmosphere for 4 h to obtain CPDs/Cu composite powder;

(3) The CPDs/Cu composite powder was placed in a graphite mold with an inner diameter of 20 mm and sintered using an SPS device with a heating rate of 100°C/min, a sintering temperature of 500°C, a sintering pressure of 20 MPa, and a holding time of 30 min. After the holding period was completed, the powder was cooled to room temperature and taken out to obtain a CPDs/Cu bulk composite material.

The mechanical properties of the composite blocks prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were tested respectively, and their stress-strain curves are shown in FIG. 10 , and the test data results are shown in Table 1.

Table 1 Mechanical properties test results of different samples

According to the mechanical test results in Table 1 and Figure 10, the performance of the composite material prepared by the preparation method of carbon polymer dot reinforced copper-based composite material by spatial confinement is more excellent. The tensile strength and elongation of the CPDs/Cu composite materials prepared by Comparative Example 1, Comparative Example 2 and Comparative Example 3, Example 1, Example 2 and Example 3 are improved to varying degrees relative to pure copper, indicating that the composite is beneficial to the improvement of copper performance. In addition, during the condensation and reflux of nitric acid, CNTs are cracked to form CPDs, and rich oxygen-containing functional groups are given on the surface. The presence of functional groups can improve the wetting between CPDs and the matrix to a certain extent, and increase the interface bonding strength between the matrix and the reinforcement phase.

Compared with comparative examples 1, 2 and 3, the performance of embodiments 1, 2 and 3 is better, indicating that the embodiments utilize the method of ultrasonic dispersion combined with electrostatic adsorption to make the CPDs with good dispersibility and solubility better dispersed in water, and the positively charged copper powder and CPDs (with anionic functional groups on the surface) can be tightly adsorbed together to ensure that the CPDs can be well combined with the copper particles with a "porous skeleton" structure, and the ball milling method is combined to further improve the dispersibility of the CPDs, "enclose" the CPDs in the pores of the copper particles with a "porous skeleton" structure, and realize the intracrystalline distribution effect in the subsequent sintering process, thereby improving the interface bonding strength; during the stretching process, the zero-dimensional nano-size effect of CPDs can effectively play the role of Orowan strengthening, significantly increase the storage density of dislocations within the crystal, obtain a good hardening effect, improve the ductility of the composite material while improving its strength, and achieve an excellent matching effect of strength and plasticity.

To sum up, the above embodiments are only preferred implementation modes of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (6)

1. A method for preparing a carbon polymer dot reinforced copper-based composite material based on space confinement is characterized by comprising the following steps:

(1) Mixing CNTs and concentrated nitric acid, condensing and refluxing at 100-140 ℃ for 36-72 h, dripping NaOH solution with the concentration of 0.2-1.0 mol/L for neutralization after the reaction, filtering, dialyzing the filtrate by using a 1kDa dialysis bag, and freeze-drying to obtain CPDs;

(2) Preparing cuprous oxide micron particles by a molecular-level blending method, and heating and reducing to generate 'porous framework' copper particle powder;

(3) Adding the CPDs prepared in the step (1) into deionized water for ultrasonic treatment, then adding 'porous framework' copper particle powder, regulating the pH value to 3.0-4.0, stirring, standing for precipitation, filtering and drying to obtain CPDs/Cu particles, and carrying out 'packaging' closed pore treatment on the CPDs/Cu particles by high-energy ball milling to obtain flaky CPDs/Cu composite powder;

(4) Carrying out consolidation treatment on the CPDs/Cu composite powder by adopting spark plasma sintering, and cooling along with a furnace to obtain a carbon polymer dot reinforced copper-based composite material;

The specific steps of the molecular blending method for preparing the cuprous oxide micron particles in the step (2) are as follows: dissolving 15.6g of copper acetate in 200-2000 mL of pure water, adding 100mL of sodium hydroxide solution with the concentration of 0.2 mol/L-1.0 mol/L, adding 10-50 mL of glucose solution with the concentration of 0.8mol/L after the solution turns into dark blue and is sticky, placing the solution into a water bath kettle at 80 ℃, taking out the solution after the solution turns into dark red, standing the solution, changing water for 2-3 times, and filtering and drying the solution to obtain cuprous oxide microparticles;

And (2) heating and reducing, namely heating to 300-500 ℃ in a mixed nitrogen-hydrogen atmosphere containing 10% of hydrogen, and preserving heat for 180-300 min.

2. The method for preparing the carbon polymer dot reinforced copper-based composite material based on space confinement according to claim 1, wherein CNTs in the step (1) are-COOH-oriented CNTs, the length is 10-20 μm, and the width is 10-20 nm; the mass fraction of the concentrated nitric acid is 65% -68%; the mass ratio of CNTs to concentrated nitric acid is 1:500-1:1000.

3. The method for preparing the carbon polymer dot reinforced copper-based composite material based on space limitation according to claim 1, wherein the ultrasonic treatment power in the step (3) is 400-500W, the time is 30-60 min, and hydrochloric acid of 0.5-2 mol/L is added dropwise to adjust the pH value.

4. The method for preparing the carbon polymer dot reinforced copper-based composite material based on space confinement according to claim 1, wherein the mass ratio of the CPDs in the step (3) to the copper particle powder with the porous framework is 1:50-1000.

5. The method for preparing the carbon polymer dot reinforced copper-based composite material based on the space limitation of claim 1, wherein the rotating speed of the high-energy ball milling process in the step (3) is 200-450 r/min, and the ball milling time is 3-8 h.

6. The method for preparing the carbon polymer dot reinforced copper-based composite material based on space confinement according to claim 1, wherein the spark plasma sintering in the step (4) is performed by heating to 500-700 ℃ at a heating rate of 100 ℃/min, and preserving heat for 5-8 min, wherein the sintering pressure is 50MPa.