Background
Copper, because of its superior conductivity, has been used as the most common interconnect in electronic devices and winding in electrical machines. Typically, its maximum service temperature is below 200 °C due to thermal oxidation of Cu that impairs its electrical properties. Although Cu wires coated by oxidation resistant metals (e.g., Ni and Ag) have been developed and utilized to benefit from the high electrical conductivity of Cu and oxidation resistance of Ni and Ag for high temperature applications, this approach is still limited to below 350 ℃ mainly due to the alloying process between different metals. However, the temperature of Cu cables and coil windings in an electrical machine can be higher than 400 °C due to the combined thermal effects of high temperature operations and Joule heating of the conductors from applied electrical current.
Today, there is a strong demand for more sophisticated conductor materials that can effectively and safely operate at high temperatures.
Invention Description
Researchers at Arizona State University have developed a new conducting material in high temperatures and harsh environments through the use of nickel (Ni)-coated copper (Cu) wires with a thermally stable interface. This invention offers high oxidation resistance, superb retention of low resistivity and high current carrying capability. The multilayered core–shell wire consists of a Cu wire as a core, continuous multilayers graphene tubes as an intermediate layer, and a Ni shell as an outer layer (namely the NiGCu wire). The intermediate graphene tubes prevent the Ni-Cu interdiffusion at high temperatures, while Ni protects the Cu core and graphene tubes from oxidation. As a result, the NiGCu wire exhibits much improved electrical performances compared to both a Cu wire and Ni-coated Cu wire at high temperatures.
Potential Applications
Benefits and Advantages