USE OF GRAPHENE-REINFORCED ULTRA-CONDUCTIVE COPPER IN FIELD OF HIGH-CURRENT DEVICES

A use of graphene-reinforced ultra-conductive copper in a field of high-current devices is provided. In the graphene-reinforced ultra-conductive copper, carbon atoms of graphene are distributed in gaps among copper atoms. This structure can lead to an exceptionally robust internal structure for the copper material, and thus makes the copper material have properties such as low temperature coefficient of resistance (TCR), small coefficient of thermal expansion (CTE), and high current density. Therefore, the graphene-reinforced ultra-conductive copper is suitable for devices requiring a high current and a low temperature, including electric vehicles (charging/motors/signals), drones, semiconductor electronics, and defense/military-grade wires. The graphene-reinforced ultra-conductive copper is a novel conductor material that integrates energy conservation, heat reduction, pressure resistance, and cost effectiveness.

TECHNICAL FIELD

The present disclosure relates to the technical field of conductor materials, and in particular relates to a use of graphene-reinforced ultra-conductive copper in a field of high-current devices.

BACKGROUND

Since the discovery of electricity by humans, countless scientists have investigated and developed a theory and application of electricity. After centuries of effort, electricity has become an indispensable part of people's lives. In recent years, electric vehicles and 5G communication have emerged as highly significant industry trends. The efficiencies of high-frequency electric signal transmission, electric power transmission, electromagnetic conversion, etc. are critically important. Conductor materials for transmitting electric energy and signals are the most pivotal materials.

To determine whether a material is a prominent conductor, the corresponding measurement criteria have been established in the International Annealed Copper Standard (IACS). The electrical conductivity of annealed pure copper with resistivity of 1.724×10−8 (Ω·m) at 20° C. is set at 100% IACS. Compared with pure copper, the pure silver with resistivity of 1.626×10−8 (Ω·m) has electrical conductivity calculated to be 106% IACS. Pure silver demonstrates the highest electrical conductivity among natural materials.

Although pure copper has electrical conductivity of 100% and resistivity of 1.724×10−8 (Ω·m), the resistivity of a round wire conductor that is made of pure copper and has a length of 1 m and a diameter of 2 mm is calculated to be 5.48 mΩ. When a current flows through this round wire conductor, the power dissipation occurs as follows: P=I2R. If a current of 100 A flows through the copper conductor, the electric energy of 10,000×0.00548=54.8 (W) will be consumed. The electric energy consumed will be converted into thermal energy, which causes a temperature of the copper conductor to arise. The temperature rise of the copper conductor will increase the impedance of the copper conductor, making the power consumption and temperature increase. This vicious circle ultimately results in the breakdown of a system, which is known as thermal breakdown.

Therefore, reducing the thermal breakdown of copper conductors and the consumption of copper materials is an urgent problem to be solved in the art.

SUMMARY

An objective of the present disclosure is to provide a use of graphene-reinforced ultra-conductive copper in a field of high-current devices. The graphene-reinforced ultra-conductive copper has characteristics such as low temperature coefficient of resistance (TCR), small coefficient of thermal expansion (CTE), and high current density, and can be used for high-current devices. The graphene-reinforced ultra-conductive copper can reduce the thermal breakdown of copper conductors and the consumption of copper materials.

To achieve the above objective of the present disclosure, the present disclosure provides the following technical solutions:

The present disclosure provides a use of graphene-reinforced ultra-conductive copper in a field of high-current devices, where in the graphene-reinforced ultra-conductive copper, carbon atoms of graphene are distributed in gaps among copper atoms.

Preferably, the copper atoms are bonded with the carbon atoms of the graphene to form metallic covalent bonds.

Preferably, the graphene-reinforced ultra-conductive copper has CTE of less than 15.7 (μm/m·° C.) at a temperature of 200° C. or less.

Preferably, the high-current devices include electric vehicles or artificial intelligence (AI) servers.

Preferably, the graphene-reinforced ultra-conductive copper is used in a form including a wire, a target, a sheet foil, or a powder.

Preferably, before use, the graphene-reinforced ultra-conductive copper is subjected to a vacuum melting treatment at 1,100° C. to 1,500° C.

The present disclosure provides a use of graphene-reinforced ultra-conductive copper in a field of high-current devices. In the graphene-reinforced ultra-conductive copper, carbon atoms of graphene are distributed in gaps among copper atoms. This structure can lead to an exceptionally robust internal structure for the copper material, and thus makes the copper material have properties such as low temperature coefficient of resistance, small CTE, and high current density. The graphene-reinforced ultra-conductive copper has a 10% to 30% higher current density than oxygen-free copper and a 10% to 30% lower TCR than oxygen-free copper. Therefore, the graphene-reinforced ultra-conductive copper is suitable for devices requiring a high current and a low temperature, including electric vehicles (charging/motors/signals), drones, semiconductor electronics, and defense/military-grade wires. The graphene-reinforced ultra-conductive copper is a novel conductor material that integrates energy conservation, heat reduction, pressure resistance, and cost effectiveness.

In the present disclosure, the graphene-reinforced ultra-conductive copper combining graphene with a copper material is used in high-current devices. According to test results, the graphene-reinforced ultra-conductive copper experiences a small temperature rise and exhibits low TCR when a current flows through the graphene-reinforced ultra-conductive copper. Therefore, the graphene-reinforced ultra-conductive copper enables a large current to pass through in a specified temperature range, which reduces the loss. The graphene-reinforced ultra-conductive copper can enhance the efficiency and reliability in green energy, electric vehicles, semiconductors, and high-frequency communications while mitigating the thermal breakdown associated with copper conductors. As a result, the graphene-reinforced ultra-conductive copper can diminish the consumption of a copper material when in use.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure provides a use of graphene-reinforced ultra-conductive copper in a field of high-current devices. In the graphene-reinforced ultra-conductive copper, carbon atoms of graphene are distributed in gaps among copper atoms.

In the present disclosure, the copper atoms are bonded with the carbon atoms of the graphene to form metallic covalent bonds.

In the present disclosure, the graphene-reinforced ultra-conductive copper is preferably prepared according to the method described in the Chinese patent (CN113073221B).

In the present disclosure, the graphene-reinforced ultra-conductive copper has CTE of less than 15.7 (μm/m·° C.) at a temperature of 200° C. or less.

In the present disclosure, the high-current devices preferably include electric vehicles or AI servers.

In the present disclosure, the high-current devices preferably include drones, semiconductor electronics, or defense/military-grade wires.

In the present disclosure, the graphene-reinforced ultra-conductive copper is used in a form preferably including a wire, a target, a sheet foil, or a powder.

In the present disclosure, before use, the graphene-reinforced ultra-conductive copper is preferably subjected to a vacuum melting treatment at preferably 1,100° C. to 1,500° C. The present disclosure does not have a special restriction on a time of the vacuum melting treatment, which can be adjusted according to actual needs.

The technical solutions provided by the present disclosure will be described in detail below with reference to embodiments, but these embodiments should not be construed as limiting the claimed scope of the present disclosure.

The graphene-reinforced ultra-conductive copper in this example was prepared according to the method described in the Chinese patent CN113073221B.

Performance Testing

The graphene-reinforced ultra-conductive copper prepared in Example 1 (a mass proportion of graphene in the graphene-reinforced ultra-conductive copper was 2,000 ppm) was subjected to vacuum melting at 1,500° C. and processed into a powder with a particle size of 25 μm. The powder and commercial 4N oxygen-free copper (with an average particle size of 25 μm) each were subjected to micro-DSC analysis, and results were shown in FIG. 2 (4N oxygen-free copper) and FIG. 3 (graphene-reinforced ultra-conductive copper).

According to the DSC results in FIG. 2, the graphene-reinforced ultra-conductive copper requires a large amount of energy for melting, and has two melting points, indicating that the graphene-reinforced ultra-conductive copper has a strong microstructure with high reliability.

When a current passes through a copper wire, the power dissipation occurs as follows: P=I2R. The electric energy is converted into thermal energy to increase the temperature and impedance of the copper conductor, resulting in large power consumption and high temperature. This vicious circle will cause the breakdown of a system, which is known as thermal breakdown. It can be seen from FIG. 6 to FIG. 7 that the graphene-reinforced ultra-conductive copper in the present disclosure has a lower temperature coefficient than the oxygen-free copper, which can increase the efficiency. When a temperature arises, the graphene-reinforced ultra-conductive copper undergoes a smaller resistance increase than the oxygen-free copper, which can reduce the risk of thermal breakdown, enhance the efficiency, and save the electricity.

Positive temperature coefficient (PTC): A resistance value of a material increases with the increase of a temperature. The larger the temperature coefficient, the greater the increase in resistance under a same temperature change.

Negative temperature coefficient (NTC): A resistance value of a material decreases with the increase of a temperature. Resistance values of both semiconductors and insulators decrease with the increase of a temperature. Graphene, semiconductors, and ceramics all exhibit NTC of resistance.

FIG. 8 shows a temperature-resistance curve of graphene. FIG. 8 comes from the prior art (Supplementary Information, November 2011. High Sensitivity Gas Detection Using a Macroscopic Three-Dimensional Graphene Foam Network.). It can be seen that graphene has NTC of resistance. The pure copper has TCR of about 0.0039, and the graphene-reinforced ultra-conductive copper has TCR of about 0.0030 to 0.0033. The graphene-reinforced ultra-conductive copper has smaller TCR than the pure copper.

6) The graphene-reinforced ultra-conductive copper prepared in Example 1 was subjected to vacuum melting, then processed into a copper ingot, and then calendered into a 0.2 mm ultra-conductive copper sheet. The ultra-conductive copper sheet, an oxygen-free copper sheet (4N copper sheet with a thickness of 0.2 mm), and a normal copper sheet each were subjected to CTE testing, and test results were shown in FIG. 9 and Table 1.

CTE data for different copper sheet samples

sheet

copper sheet

copper sheet

It can be seen from Table 1 and FIG. 9 that, at 100° C. to 150° C., CTE of the graphene-reinforced ultra-conductive copper is 8.3% lower than CTE of the oxygen-free copper sheet, and at 200° C. to 250° C., CTE of the graphene-reinforced ultra-conductive copper is 22.8% lower than CTE of the oxygen-free copper sheet.

Test materials: 1. Pure copper wire, which was a 128-strand twisted wire with a single-strand diameter of 0.2 mm.

Temperature rise data for the pure copper and

Input current
Pure copper
Ultra-conductive
Temperature

and measured
wire with a
copper wire with
fall of ultra-

temperature
cross-sectional
a cross-sectional
conductive

rise of a wire
area: 4.14 mm2
area of 4.14 mm2
copper/%

It can be seen from FIG. 10 and Table 2 that at 55 A, a temperature of the ultra-conductive copper decreases by 14° C., and at 75 A, the temperature of the ultra-conductive copper decreases by 31° C. Under a same cross-sectional area, the graphene-reinforced ultra-conductive copper enables a 10% to 20% higher current to pass through than the pure copper.

Test materials: 1. Oxygen-free copper wire with a single-strand diameter of 0.2 mm. A fast charging cable was produced from a plurality of twisted wires.

Limitations: An internal temperature of a wire must not exceed 125° C. A temperature of the D+ connector must not exceed 90° C. Test results were shown in Table 3.

Fast-charging data for the 4N copper and graphene-

Internal
Temperature

temperature
of a D+

Charging time
of a wire
connector

It can be seen from Table 3 that the graphene-reinforced ultra-conductive copper, as a wire conductor, can significantly reduce a temperature and can increase a current by about 20%.

If the graphene-reinforced ultra-conductive copper is adopted as the D+ connector material, the fast-charging time can be extended. The graphene-reinforced ultra-conductive copper facilitates the development of fast charging at 800 A and 1,000 A.

Current-carrying capacity data for the normal oxygen-free copper and ultra-conductive copper

Ultra-conductive copper (field testing at an

Normal oxygen-free copper (with reference
ambient temperature of 25° C.)

to American wire gauge (AWG) table)

Impedance

or
sectional
of normal
carrying
or
sectional
conductive
carrying

diameter
area
copper
capacity
diameter
area
copper
capacity

It can be seen from Table 4 that the graphene-reinforced ultra-conductive copper has a significantly-higher current-carrying capacity than the normal oxygen-free copper under similar wire diameters. The thinner the wire, the larger the difference. Since a current density is equal to current-carrying capacity/cross-sectional area, it is obvious that a current density of the graphene-reinforced ultra-conductive copper is significantly higher than a current density of the normal oxygen-free copper.

In a same test, a constant current was input simultaneously into the normal copper wire (normal copper) and the ultra-conductive copper wire (ACOOL copper), and test results were shown in FIG. 11. FIG. 11 is a comparison chart of resistance increase rates and input energies of the graphene-reinforced ultra-conductive copper in Example 1 and the normal copper wire. Under a same energy input, the ultra-conductive copper wire has a lower resistance rise rate than the normal copper wire, indicating that the resistance of the ultra-conductive copper is far lower than the resistance of the normal copper.

Due to the slow increase in impedance of a ultra-conductive copper wire when a current is input, there will be a large induced current in a generator adopting the ultra-conductive copper wire.

FIG. 12 is a schematic diagram of a generator and a toroidal transformer that adopt the graphene-reinforced ultra-conductive copper in Example 1. As shown in FIG. 12, the actual measurements of an output power of the generator indicate that a power of electricity generation increases by 15% to 20%. The actual measurements for the toroidal transformer show that an output power of the toroidal transformer increases by 15% to 20%.

FIG. 13 is a schematic diagram of an electric motor adopting the graphene-reinforced ultra-conductive copper in Example 1 and pulse voltages applied to phase coils. As shown in FIG. 13, a pulse voltage of a drive motor adopting a ultra-conductive copper coil can reduce a duty cycle to avoid overcharging, which can reduce the energy consumption by 15% to 20%.