Researchers at the Department of Energy’s Pacific Northwest National Laboratory discovered that adding 19 parts per million of graphene to electrical-grade copper decreases the temperature coefficient of resistance by 11% without decreasing electrical conductivity at room temperature.
This discovery, reported in the January 2024 issue of the journal “Materials & Design,” runs counter to established observations, in which the introduction of additives into a metal typically increases its temperature coefficient of resistance—meaning it heats up faster than pure metal.
“This discovery runs counter to what’s generally known about the behavior of metals as conductors,” said materials scientist Keerti Kappagantula, one of the DOE researchers on the project. “We are describing a new and exciting property of this metal composite where we observe enhanced conductivity in a manufactured copper wire.”
Used in electrical wiring since 1820, copper has long been considered the best electricity conductor, capable of bearing heavy overloads and current surges. Its malleability enables it to be deformed without breakage. Additional beneficial qualities include corrosion resistance, heat transfer strength and high tensile resistance. It is also highly durable, requiring minimal maintenance.
This new copper-graphene composite wire is expected to provide further design flexibility, meaning application possibilities abound. “Anywhere there’s electricity, we have a use case,” Kappagantula said.
Coiled copper wire forms used in the core of electric motors and generators could allow them to operate at higher temperatures without losing conductivity. An 11% increase in electrical conductivity produces a 1% gain in motor efficiency.
Additionally, the composite could be used in the wiring that carries electricity from transmission lines into buildings. Because it’s more conductive, it may help meet increasing demand with efficiency savings. Kappagantula called it “a beautiful solution for copper wiring in high-density urban settings.”
As the research team continues to explore applications for the copper-graphene material and measure its essential properties, including strength, fatigue, corrosion and wear resistance, copper prices are expected to increase 75% over the next two years, driven by demand from the renewable energy sector, according to a January 2024 CNBC report. Copper is commonly used in electrical equipment, industrial machines and the automotive industry.
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