Prof. Mehmet Ertugrul
Prof. Mehmet Ertugrul
Title : Graphene/CNT-Metal Composites and Energy Efficient Ultraconductive-Covetic Materials
Nowadays, energy-saving and increasing the efficiency of power transmission lines, electrical machines and transformers are important as much as diversity and renewability of energy resources. The existing worldwide power transmission lines are sufficient for 1GW power transmission which meets the current need of the World. However, considering the increasing power need it would be impossible to transmit dozens of GW power using the existing transmission lines due to the current carrying limitation of the metals used in transmission lines. Hence, it is a must to develop new materials for power transmission lines. Although superconductors are a superior choice in terms of energy efficiency, it has disadvantages such as high production and operation costs in addition to critical temperature, current and field limitations. The production stages of superconductor wires are performed by using special devices and expensive techniques. Moreover, cooling them down to cryogenic temperatures increases the operating costs. Thus, superconductors are not used in power transmission except a few test-based applications in the World. The studies on energy- efficient materials, which can be alternative to superconductors and normal conductors, especially for applications of daily life are continued due to these disadvantages. It is known that new generation electrical materials on which the studies heavily performed in recent years have demonstrated close or better performances than superconductors in certain aspects even though they are not superconductors. One potential approach for decreasing copper’s electrical resistivity is the incorporation of carbon nanotubes into copper. This process has been shown to increase the ambient-temperature electrical conductivity of copper to more than 140% of that of pure copper. This nano-composite material is called UltraConductive copper. Carbon nanotubes conduct electricity differently than metals: optimizing the electrical conductivity of a copper/nanocarbon composite requires careful engineering on a nano-scale. Research done by James Maxwell et all in USA Los Alamos National Laboratory (LANL) for this purpose shown that, because carbon nanotubes (CNT) are ballistic conductors, wires produced from CNT-Cu composite structures have higher conductivity and much better current carrying capacities than copper. (http://www.lanl.gov/science/NSS/issue2_2011/ story5full.shtml). After James Maxwell et all’s studies, interest in this subject have grown significantly. For example, there is an ongoing project supported by many universities and companies in European Commission under the 7th Framework Programme (http://ultrawire.eu/).
The latest ones of these materials are metal-nanocarbon composites also called “covetic”. Electrical and thermal conductance, mechanical strength, oxidation and corrosion resistances, current carrying capacities of these new materials are enhanced considerably compared to conventional pure materials such as Cu, Al which are commonly used in the electronics industry. They also have potential energy-efficient usage. Covetic wires have close or superior performances than superconductors in almost every aspects excluding the zero-resistance property of superconductors for DC currents. Covetic materials, which show performances close (i.e. current carrying capacity greater than109 A/cm2 ) to superconductors such as YBCO, MgB2 with high production and operating costs and limitations in addition to their inability to work at room temperature, have easy production processes and they can work at room temperatures unlike superconductors. Another property of covetic materials superior to superconductors is that there is no AC loss in covetic wires and they can work in high frequencies with high performances. While the properties of type II superconductors get weakened under magnetic field there is no such situation in covetic structures.