CN108817388A - A kind of method that discharge plasma sintering prepares graphene reinforced aluminum matrix composites - Google Patents

Abstract

The invention discloses a method for preparing a graphene-reinforced aluminum-based composite material by discharge plasma sintering, which uses Al powder and aluminum-coated graphene as raw materials, mixes them by ball milling, pre-presses them, and then sinters them by discharge plasma. The aluminum-based composite material with excellent mechanical properties and electrical conductivity can be prepared through the method of the invention.

Description

A method for preparing graphene-reinforced aluminum matrix composites by spark plasma sintering

technical field

The invention belongs to the technical field of graphene composite materials, and in particular relates to a preparation method of graphene-reinforced metal matrix block composite materials.

Background technique

With the development of China's economic strength, major changes have taken place in China's wire and cable industry. The most obvious material substitution is to replace copper conductors with aluminum conductors. In order to meet the high-capacity power transmission of existing aluminum cables, aluminum conductors with larger cross-sections must be used, and the subsequent increase in the insulation, sheath and armoring materials of aluminum core cables weakens the use of aluminum conductors. Therefore, the research and development of aluminum cables with small cross-section, high strength and high conductivity is imperative.

Single-layer graphene is a semiconductor with a sheet thickness of about 2nm, no energy gap, and linear energy distribution. In single-layer graphene, each carbon atom contributes an unbonded electron, and the electrons are distributed in a cone shape. These electrons can move freely in the crystal, giving graphene its very good electrical conductivity. Therefore, graphene and aluminum metal are combined to prepare graphene-aluminum matrix composite materials, which have excellent properties such as light weight, high strength and high electrical conductivity, and can meet the needs of the field of elevated high-voltage transmission lines.

Using graphene as a reinforcement to prepare aluminum matrix composites can greatly increase the strength of aluminum materials. In addition, the plastic deformation of composites is mainly manifested as slip along the graphene surface, indicating that the interface mechanical properties of graphene and metal aluminum are very important for composite materials. have a significant impact on the overall performance. However, due to the poor wettability between aluminum and graphene, the interface between aluminum and graphene is prone to defects, which leads to insufficient contact between graphene and aluminum, so that the mechanical properties of the prepared graphene-enhanced aluminum matrix composite and decreased conductivity.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the present invention provides a method for preparing graphene-reinforced aluminum-based composite materials by spark plasma sintering, aiming to obtain composite materials with excellent mechanical properties and electrical conductivity.

The method for preparing a graphene-reinforced aluminum-based composite material by spark plasma sintering of the present invention is characterized in that it comprises the following steps:

Step 1. According to the composition of the required graphene-reinforced aluminum-based composite material, weigh Al powder and aluminum-coated graphene, and mix them by ball milling to obtain a uniform composite powder; according to the required product size, weigh a certain amount of composite powder powder for use;

Step 2. Fill the composite powder weighed in step 1 into the graphite mold covered with graphite paper; use a manual hydraulic press to pre-press the graphite mold filled with the composite powder, and the pressure is 8-12MPa;

Step 3. Wrap a 4-6mm thick carbon felt around the graphite mold with the composite powder, then place it in the furnace of the spark plasma sintering system, evacuate it to below 5Pa, and pass a DC pulse current to the composite powder. For consolidation forming, the process conditions are:

The axial pressure is 10-50MPa;

The heating rate is 20～50℃/min;

The sintering temperature is 550-600°C;

The holding time is 5-10 minutes;

Step 4. After the sintering is completed, the sintered sample is cooled to room temperature with the furnace, and a cylindrical ingot of graphene-reinforced aluminum matrix composite material is obtained.

Further, in step 1, metal Al powder with a particle size of 38 μm and aluminum-coated graphene particles with a particle size between 2 and 4 μm are selected.

Further, in step 1, the weight ratio of the aluminum-coated graphene to the Al powder ranges from 0.5wt% to 3wt%.

Further, in step 1, the ball-to-material ratio of the ball mill is 5:1; the ball mill is carried out in a ball mill with a rotational speed of 350 r/min, and the ball milling time is 12 hours.

Further, in step 3, the optimum technological condition of described consolidation forming is:

Axial pressure: 10MPa (≤400°C) and 50MPa (>400°C);

Heating rate: 50°C/min (≤400°C) and 20°C/min (>400°C);

Sintering temperature: 600°C;

Holding time: 3 minutes at 400°C, 5 minutes at 600°C;

The specific steps are: apply an initial pressure of 10MPa to both ends of the compacted powder material, heat the graphite mold from room temperature to 400°C at a heating rate of 50°C/min; During the heating process, keep it warm for 3 minutes; then heat the graphite mold to 600°C at a heating rate of 20°C/min, and pressurize both ends of the compacted powder material to a pressure of 50MPa during the heating process; at a sintering temperature of 600°C , In an environment with a sintering pressure of 50MPa, keep the heat for 10 minutes.

The beneficial effects of the present invention are reflected in:

1. As an active metal, aluminum has a strong oxygen absorption capacity, and a dense oxide film will be formed on its surface. The sintering method adopted in the present invention is discharge plasma sintering technology, which integrates plasma activation and hot pressing. Under the action of its pulse current, a discharge phenomenon occurs between the powder particles, and the generated high-temperature plasma and discharge shock pressure can not only effectively remove the gas and impurities adsorbed on the surface of the powder particles, but also purify the powder surface to a certain extent The effect is to reduce the nitrogen and oxygen content of the graphene-reinforced aluminum matrix composite, thereby improving its mechanical properties and electrical conductivity, and the rapid diffusion caused by the discharge promotes the particle densification process.

2. The present invention optimizes the manufacturing process of graphene-reinforced aluminum-based composite materials. When the above-mentioned optimal process conditions are adopted for consolidation forming, the advantages of the manufacturing process can be fully utilized, and graphene with high density and uniform composition can be obtained. Reinforced aluminum matrix composite products.

3. The present invention uses aluminum-coated graphene particles as raw materials, which solves the problems that aluminum is difficult to wet on the surface of graphene in the existing graphene-reinforced aluminum-based composite materials, and holes and defects are easily formed at the interface, thereby preparing an excellent Mechanical properties and electrical conductivity of graphene-reinforced aluminum matrix composites.

Description of drawings

Fig. 1 is the SEM figure of the graphene-reinforced aluminum-based composite material product obtained in Example 1 of the present invention;

Detailed ways

The present invention is further described through the following examples, but the embodiments of the present invention are not limited thereto.

In the following examples, metal Al powder with a particle size of 38 μm (purchased from Sichuan Kehui Industrial Co., Ltd.) and aluminum-coated graphene particles with a particle size between 2 and 4 μm (purchased from Zhiyang Technology (China) Co., Ltd. company);

In the following examples, the shape of the graphite mold used is cylindrical, and the diameter of the inner space of the cylindrical graphite mold is 20 mm.

In the following examples, the spark plasma sintering furnace used is the LABOX-350 spark plasma sintering system produced by Japan Sinter Land Inc., the current type is DC pulse current, and the pulse sequence is 40:7.

Comparative example 1

The pure aluminum sintered sample of the present embodiment is carried out as follows:

Step 1. Weigh a certain amount of Al powder and mix it by ball milling for 12 hours (the ball-to-material ratio of the ball mill is 5:1; the ball mill is carried out in a ball mill with a speed of 350r/min, and the ball milling method is 10min and 20min stop ), obtain the powder after ball milling; according to the required product size, take a certain amount of Al powder for subsequent use;

Step 2. Fill the weighed Al powder into the graphite mold; use a manual hydraulic press to pre-press the graphite mold filled with Al powder, and the pressure is ~10MPa;

Step 3. Wrap ~5mm thick carbon felt around the graphite mold filled with Al powder, then place it in the hearth of the spark plasma sintering system, evacuate it to below 5Pa, and pass a DC pulse current to the Al powder. Consolidation forming, the process conditions are:

Axial pressure: 10MPa (≤400°C) and 50MPa (>400°C);

Heating rate: 50°C/min (≤400°C) and 20°C/min (>400°C);

Sintering temperature: 600°C;

Holding time: 3 minutes at 400°C, 5 minutes at 600°C;

Step 4. After the sintering is completed, the sintered sample is cooled to room temperature with the furnace, and a cylindrical ingot of pure aluminum material is obtained.

The performance indexes of the materials obtained in this comparative example are shown in Table 1.

Example 1

Graphene (0.5wt%) of the present embodiment strengthens the aluminum-based composite material to carry out as follows:

Step 1, be 0.5wt% by the weight ratio of aluminum-coated graphene and Al powder, take Al powder and aluminum-coated graphene, adopt ball mill mixing method to mix 12h (the ball material ratio of ball mill is 5:1; Ball mill in ball mill Carry out, the rotating speed of ball mill is 350r/min, adopt the ball mill mode of turning 10min, stopping 20min), obtain uniform composite powder; According to the required product size, weigh a certain amount of composite powder for standby;

Step 2. Fill the composite powder weighed in step 1 into the graphite mold covered with graphite paper; use a manual hydraulic press to pre-press the graphite mold filled with the composite powder, and the pressure is ~ 10MPa;

Step 3. Wrap ~5mm thick carbon felt around the graphite mold with composite powder, then place it in the hearth of the spark plasma sintering system, evacuate it to below 5Pa, and pass a DC pulse current to the composite powder. Consolidation forming, the process conditions are:

Axial pressure: 10MPa (≤400°C) and 50MPa (>400°C);

Heating rate: 50°C/min (≤400°C) and 20°C/min (>400°C);

Sintering temperature: 600°C;

Holding time: 3 minutes at 400°C, 5 minutes at 600°C;

Step 4. After the sintering is completed, the sintered sample is cooled to room temperature with the furnace, and a cylindrical ingot of a graphene-reinforced aluminum matrix composite material with high density and high uniformity is obtained. Its SEM image is shown in Figure 1, and it can be seen that the product structure is uniform.

The performance index of the material obtained in this embodiment is shown in Table 1.

Example 2

Graphene (1.0wt%) of the present embodiment strengthens the aluminum-based composite material to carry out as follows:

Step 1, be 1.0wt% by the weight ratio of aluminum-coated graphene and Al powder, take Al powder and aluminum-coated graphene, adopt ball mill mixing method to mix 12h (the ball material ratio of ball mill is 5:1; Ball mill in ball mill Carry out, the rotating speed of ball mill is 350r/min, adopt the ball mill mode of turning 10min, stopping 20min), obtain uniform composite powder; According to the required product size, weigh a certain amount of composite powder for standby;

Step 2. Fill the composite powder weighed in step 1 into the graphite mold covered with graphite paper; use a manual hydraulic press to pre-press the graphite mold filled with the composite powder, and the pressure is ~ 10MPa;

Step 3. Wrap ~5mm thick carbon felt around the graphite mold with composite powder, then place it in the hearth of the spark plasma sintering system, evacuate it to below 5Pa, and pass a DC pulse current to the composite powder. Consolidation forming, the process conditions are:

Axial pressure: 10MPa (≤400°C) and 50MPa (>400°C);

Heating rate: 50°C/min (≤400°C) and 20°C/min (>400°C);

Sintering temperature: 600°C;

Holding time: 3 minutes at 400°C, 5 minutes at 600°C;

Step 4. After the sintering is completed, the sintered sample is cooled to room temperature with the furnace, and a cylindrical ingot of a graphene-reinforced aluminum matrix composite material with high density and high uniformity is obtained.

The performance index of the material obtained in this embodiment is shown in Table 1.

Example 3

Graphene (1.5wt%) of the present embodiment strengthens the aluminum-based composite material to carry out as follows:

Step 1, be 1.5wt% by the weight ratio of aluminum-coated graphene and Al powder, take Al powder and aluminum-coated graphene, adopt ball mill mixing method to mix 12h (the ball material ratio of ball mill is 5:1; Ball mill in ball mill Carry out, the rotating speed of ball mill is 350r/min, adopt the ball mill mode of turning 10min, stopping 20min), obtain uniform composite powder; According to the required product size, weigh a certain amount of composite powder for standby;

Step 2. Fill the composite powder weighed in step 1 into the graphite mold covered with graphite paper; use a manual hydraulic press to pre-press the graphite mold filled with the composite powder, and the pressure is ~ 10MPa;

Step 3. Wrap ~5mm thick carbon felt around the graphite mold with composite powder, then place it in the hearth of the spark plasma sintering system, evacuate it to below 5Pa, and pass a DC pulse current to the composite powder. Consolidation forming, the process conditions are:

Axial pressure: 10MPa (≤400°C) and 50MPa (>400°C);

Heating rate: 50°C/min (≤400°C) and 20°C/min (>400°C);

Sintering temperature: 600°C;

Holding time: 3 minutes at 400°C, 5 minutes at 600°C;

Step 4. After the sintering is completed, the sintered sample is cooled to room temperature with the furnace, and a cylindrical ingot of a graphene-reinforced aluminum matrix composite material with high density and high uniformity is obtained.

The performance index of the material obtained in this embodiment is shown in Table 1.

Example 4

Graphene (2.0wt%) of the present embodiment strengthens the aluminum-based composite material to carry out as follows:

Step 1, be 2.0wt% by the weight ratio of aluminum-coated graphene and Al powder, take Al powder and aluminum-coated graphene, adopt ball mill mixing method to mix 12h (the ball material ratio of ball mill is 5:1; Ball mill in ball mill Carry out, the rotating speed of ball mill is 350r/min, adopt the ball mill mode of turning 10min, stopping 20min), obtain uniform composite powder; According to the required product size, weigh a certain amount of composite powder for standby;

Step 2. Fill the composite powder weighed in step 1 into the graphite mold covered with graphite paper; use a manual hydraulic press to pre-press the graphite mold filled with the composite powder, and the pressure is ~ 10MPa;

Step 3. Wrap ~5mm thick carbon felt around the graphite mold with composite powder, then place it in the hearth of the spark plasma sintering system, evacuate it to below 5Pa, and pass a DC pulse current to the composite powder. Consolidation forming, the process conditions are:

Axial pressure: 10MPa (≤400°C) and 50MPa (>400°C);

Heating rate: 50°C/min (≤400°C) and 20°C/min (>400°C);

Sintering temperature: 600°C;

Holding time: 3 minutes at 400°C, 5 minutes at 600°C;

Step 4. After the sintering is completed, the sintered sample is cooled to room temperature with the furnace, and a cylindrical ingot of a graphene-reinforced aluminum matrix composite material with high density and high uniformity is obtained.

The performance index of the material obtained in this embodiment is shown in Table 1.

Example 5

Graphene (2.5wt%) of the present embodiment strengthens the aluminum-based composite material to carry out as follows:

Step 1, be 2.5wt% by the weight ratio of aluminum-coated graphene and Al powder, take Al powder and aluminum-coated graphene, adopt ball mill mixing method to mix 12h (the ball material ratio of ball mill is 5:1; Ball mill in ball mill Carry out, the rotating speed of ball mill is 350r/min, adopt the ball mill mode of turning 10min, stopping 20min), obtain uniform composite powder; According to the required product size, weigh a certain amount of composite powder for standby;

Step 2. Fill the composite powder weighed in step 1 into the graphite mold covered with graphite paper; use a manual hydraulic press to pre-press the graphite mold filled with the composite powder, and the pressure is ~ 10MPa;

Step 3. Wrap ~5mm thick carbon felt around the graphite mold with composite powder, then place it in the hearth of the spark plasma sintering system, evacuate it to below 5Pa, and pass a DC pulse current to the composite powder. Consolidation forming, the process conditions are:

Axial pressure: 10MPa (≤400°C) and 50MPa (>400°C);

Heating rate: 50°C/min (≤400°C) and 20°C/min (>400°C);

Sintering temperature: 600°C;

Holding time: 3 minutes at 400°C, 5 minutes at 600°C;

Step 4. After the sintering is completed, the sintered sample is cooled to room temperature with the furnace, and a cylindrical ingot of a graphene-reinforced aluminum matrix composite material with high density and high uniformity is obtained.

The performance index of the material obtained in this embodiment is shown in Table 1.

Example 6

Graphene (3.0wt%) of the present embodiment strengthens the aluminum-based composite material to carry out as follows:

Step 1, be 3.0wt% by the weight ratio of aluminum-coated graphene and Al powder, take Al powder and aluminum-coated graphene, adopt ball mill mixing method to mix 12h (the ball material ratio of ball mill is 5:1; Ball mill in ball mill Carry out, the rotating speed of ball mill is 350r/min, adopt the ball mill mode of turning 10min, stopping 20min), obtain uniform composite powder; According to the required product size, weigh a certain amount of composite powder for standby;

Step 2. Fill the composite powder weighed in step 1 into the graphite mold covered with graphite paper; use a manual hydraulic press to pre-press the graphite mold filled with the composite powder, and the pressure is ~ 10MPa;

Step 3. Wrap ~5mm thick carbon felt around the graphite mold with composite powder, then place it in the hearth of the spark plasma sintering system, evacuate it to below 5Pa, and pass a DC pulse current to the composite powder. Consolidation forming, the process conditions are:

Axial pressure: 10MPa (≤400°C) and 50MPa (>400°C);

Heating rate: 50°C/min (≤400°C) and 20°C/min (>400°C);

Sintering temperature: 600°C;

Holding time: 3 minutes at 400°C, 5 minutes at 600°C;

Step 4. After the sintering is completed, the sintered sample is cooled to room temperature with the furnace, and a cylindrical ingot of a graphene-reinforced aluminum matrix composite material with high density and high uniformity is obtained.

The performance index of the material obtained in this embodiment is shown in Table 1.

Table 1

Comparing the performance parameter values of the examples and the comparative examples in Table 1, it can be seen that: the tensile strength and the hardness of the composite material prepared by the present invention are obviously higher than the comparative example materials, and the electrical conductivity is also close to the comparative example materials, so when the electrical conductivity is satisfied Under the premise that the transmission rate is not greatly reduced, its mechanical properties and hardness can meet the performance requirements of elevated high-voltage transmission lines.

Claims (5)

1. a method for preparing graphene-reinforced aluminum matrix composites by spark plasma sintering, is characterized in that, comprises the steps: Step 1. According to the composition of the required graphene-reinforced aluminum-based composite material, weigh Al powder and aluminum-coated graphene, and mix them by ball milling to obtain a uniform composite powder; according to the required product size, weigh a certain amount of composite powder powder for use; Step 2. Fill the composite powder weighed in step 1 into the graphite mold covered with graphite paper; use a manual hydraulic press to pre-press the graphite mold filled with the composite powder, and the pressure is 8-12MPa; Step 3. Wrap a 4-6mm thick carbon felt around the graphite mold with the composite powder, then place it in the furnace of the spark plasma sintering system, evacuate it to below 5Pa, and pass a DC pulse current to the composite powder. For consolidation forming, the process conditions are: The axial pressure is 10-50MPa; The heating rate is 20～50℃/min; The sintering temperature is 550-600°C; The holding time is 5-10 minutes; Step 4. After the sintering is completed, the sintered sample is cooled to room temperature with the furnace, and a cylindrical ingot of graphene-reinforced aluminum matrix composite material is obtained. 2. The method according to claim 1, characterized in that: in step 1, metal Al powder with a particle size of 38 μm and aluminum-coated graphene particles with a particle size between 2 and 4 μm are selected. 3. The method according to claim 1, characterized in that in step 1, the weight ratio of the aluminum-coated graphene to the Al powder ranges from 0.5wt% to 3wt%. 4. The method according to claim 1, characterized in that: in step 1, the ball-to-material ratio of the ball mill is 5:1; the ball mill is carried out in a ball mill, the speed of the ball mill is 350r/min, the ball milling time is 12h, and the ball milling time is 10min. , Stop 20min ball milling way. 5. The method according to claim 1, characterized in that: in step 3, the specific steps of said consolidation forming are: Apply an initial pressure of 10MPa to both ends of the compacted powder material, and heat the graphite mold from room temperature to 400°C at a heating rate of 50°C/min; in an environment with a sintering temperature of 400°C and a sintering pressure of 10MPa, keep it warm for 3 minutes ; Then heat the graphite mold to 600°C at a heating rate of 20°C/min, and continuously pressurize both ends of the compacted powder material to a pressure of 50MPa during the heating process; at a sintering temperature of 600°C and a sintering pressure of In the environment of 50MPa, keep warm for 10min.