With the development of science and technology, people’s demand for electricity is also increasing, making it important to increase power generation and optimize the power grid system. The U.S. National Laboratory has newly developed a highly conductive composite copper wire that not only reduces the problem of heat generation when electricity is turned on, but also subverts people’s previous understanding of the conductive properties of metals.
Usually metal wires will heat up after being energized, and the resistance will increase and the conductivity will decrease in the process. When the wire heats up to a certain level, it will burn out.
For this reason, researchers are looking for other materials to enhance the conductivity of metals and reduce or solve the problem of heat generation when metals are energized. In the past, there were manganese copper and constantan, which can reduce the temperature coefficient of resistance (TCR) of metals to close to zero. However, these alloys are usually used in resistors and are not suitable for large-scale energy transmission applications such as motors and power grids. , because their room temperature conductivity is much lower than that of pure copper.
Scientists at the Pacific Northwest National Laboratory in the United States have discovered that a new composite material made from a common carbon compound mixed with copper in an appropriate proportion not only significantly improves the conductive properties of wires, but also overturns the It breaks the traditional concept of metal conductivity. This result was published in the scientific magazine “Materials and Design” in December 2023.
This common carbon compound is now the popular material “graphene (single-layer graphite)”. Because graphene is a transparent nanomaterial with excellent thermal and electrical conductivity and a lower resistivity than copper or silver, it is used In many places, including aerospace, metals, electronic components and other emerging materials.
The team first coated electrical grade pure copper (Cu) with a thin layer of graphene (Gr), and used the shear-assisted processing and extrusion (ShAPETM) method to make a product with a diameter of about 1.5 mm and a length of more than 0.2 meters. Cu-Gr composite material, the optimal content of graphene in the composite material at this time is 18 parts per million (18ppm).
This graphene content ratio is more stable than 12ppm and 25ppm, and can reduce the TCR value of the material by 11% compared to pure copper, and increase the conductivity by about 1%. In addition, its conductivity does not decrease at room temperature (20°C), but its conductivity increases at temperatures from 200°C to 400°C.
Researchers used tools such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT) to analyze the grain size and crystal orientation of copper and graphene in pure copper and Cu-Gr composite materials. , structure and composition differences, hoping to explain how Cu-Gr enhances its metal conductivity.
They found that composite wires made with ShAPE produced a uniform and nearly non-porous microstructure. The material is dotted with tiny graphene flakes and clusters and reduces crystal defects (differences in the size of crystal particles in the material), which may be one of the reasons for the composite’s reduced resistivity.
They also proved that the Cu-Gr composite material can be mass-produced and used in industry because the material has lower TCR and higher conductive properties. This new discovery may in the future improve the efficiency of power distribution from the grid to homes and businesses, and also enhance the efficiency of motors, which is a good thing for the electric vehicle and industrial equipment industries.
Current motors and grids are designed to operate within temperatures of 20°C to 300°C to ensure their performance and stability. If they get too hot while running, the conductivity of the internal wires will drop dramatically and they will most likely burn out, so using more conductive composite wire may help solve this problem and increase efficiency.
Keerti Kappagantula, a materials scientist at the U.S. Department of Energy’s Pacific Northwest National Laboratory, told the lab’s newsroom, “This finding goes against common knowledge about metallic conductors. Often adding things to metals increases their temperature coefficient of resistance, causing them to heat up faster than pure metals at the same current levels.”
“We observed that this new copper composite has an exciting new property, which is enhanced electrical conductivity,” Kapagantura said. She also said, “Single-layer graphene sheets and graphene clusters Both have to be present to be a better conductor for high-temperature operations.”
The research team stated that the new copper-graphene composite wire will provide great design flexibility when applied to any industrial application. The research team continues to work on customizing the new copper-graphene material, hoping to use this wire in industry and daily life. They will also measure its strength, fatigue, corrosion and wear resistance, and these properties Crucial for industrial applications.
The team has patented the technology and is supported by the U.S. Department of Energy’s (DOE) Office of Advanced Materials and Manufacturing Technologies.
