Tech Insights

Copper Conundrum: Can Research Improve Strength, Conductivity?

June 04, 2024 by Liam Critchley

Researchers are innovating ways to increase copper’s conductivity and make it stronger, lighter, and more cost-effective.

Copper has been a key material in electric wiring for over a century due to its high electrical conductivity. However, even in the purest copper materials, conductivity has not increased. As technologies advance, engineers are researching how to improve copper materials to make devices more efficient.

Most research has focused on additives such as graphene or innovative manufacturing processes to improve copper’s strength, conductivity, or cost.

 

Copper cables

Copper cables. Image used courtesy of Adobe Stock

 

Using Graphene Composites

Graphene has excellent electrical and mechanical properties, with electrical conductivity properties better than copper—up to 100 MS/M compared to 55 MS/M for copper. Graphene also boasts a huge density of charge carriers of up to 1011 – 1012 cm2 and an incredibly high charge carrier mobility of 15,000 cm2 v-1 s-1.

However, these are the properties of chemical vapor deposition (CVD) graphene, a single graphene layer created from a bottom-up deposition process. In many applications, especially composite applications, graphene materials commonly range from two to ten layers and are made from graphite exfoliation.

Adding a small amount of graphene to composite materials makes them more conductive and mechanically robust, thanks to graphene’s tensile strength, which is 200 times that of steel. Graphene is also super-lightweight, and because only a small amount of graphene is needed (often 1 wt% or lower), it can help reduce copper wires’ weight.

Despite the calls for graphene in computing and electronics, its true value in today’s market is enhancing different composite materials. The energy and electrification sectors are also looking to utilize graphene.

 

Flash Graphene Process

Flash graphene has become a relatively new way to produce large volumes of graphene. This process originated from the Tour Lab at Rice University in 2020 and has since been commercialized by Universal Matter. This process takes any carbon-rich material (including organic waste) and applies a high current and high voltage pulse for a hundred milliseconds. This elevates the temperature to around 5,000°F, sublimating any other elements from the starting material and leaving only carbon to form graphene.

 

Video used courtesy of Rice University

 

University of Colorado Boulder researchers have made graphene-infused copper materials using a flash graphene manufacturing process. The method can make the materials in about 30 seconds without needing a furnace. It creates graphene-infused copper, starting with carbon black and copper powders. This flash process operates at around 1500°F and is a way to forge new materials, not manufacture graphene.

The infusion process can also use a copper wire. In this case, a carbon black emulsion is deposited on the wire and flashed, infusing the copper wire with graphene. In both cases, the copper’s conductivity has been increased. 

The University of Colorado’s project aims to create graphene-infused copper materials with a 125% International Annealed Copper Standard (IACS). At this stage in their research, the material has an electrical conductivity of 104.3% IACS (around 60 MS/M).

 

‘SHAPE’-ing Copper-Graphene Conductivity

NAECO, a Georgia-based materials company, has used existing additive materials to boost copper's electrical performance. NAECO creates the copper-graphene composites using Shear-Assisted Processing and Extrusion (SHAPE) technology, which combines small amounts of additive materials with copper and graphene in the solid phase. SHAPE technology spins metal alloy pieces and creates friction heat. The process softens the material to extrude through a die to make the wire. SHAPE is more energy efficient than other manufacturing technologies.  

NAECO’s composite materials have already achieved 105% IACS, but the company believes that 112% IACS can be achieved. This translates to an electrical conductivity of around 65 MS/M. NAECO is specifically targeting the transportation and aerospace sectors with its copper materials.

 

Targeting Motors

MetalKraft Technologies from Ohio has developed a copper-graphene composite ultra wire intended to make electric motors more efficient and reduce large-scale energy consumption and carbon emissions.

 

MetalKraft’s extruded tubes.

MetalKraft’s extruded tubes. Image used courtesy of MetalKraft

 

MetalKraft has used solid-phase processing techniques and SHAPE approaches to integrate graphene into copper. So far, the team has improved copper’s electrical conductivity by 3% (103% IACS), but the goal is to improve the conductivity by 10% to achieve 110% IACS, around 64 MS/M.

 

Superconducting Copper Cables

Selva Research Group from the University of Houston has created superconducting copper wires instead of graphene-enhanced ones. Superconductors are materials with zero electrical resistance below a certain temperature. The search continues for room-temperature superconductors, as many need to be cooled to ultra-low temperatures. However, there are still many avenues for superconducting wires, as there is the potential for infinite conductivity because electrons are being impeded.

The Selva team has created a superconducting wire called REBCO, which stands for Rare Earth Ba-Cu-O. The superconducting wire is a ceramic material, but beyond its conductivity properties, it also costs less. Selva’s superconducting wire costs eight times less than other superconductors and is around half the cost of traditional copper wire. This decreases the price to more affordable ranges, even for applications such as transmission lines. Selva claims the wires have five times the current carrying capacity of state-of-the-art superconductors. 

The team is targeting numerous areas with its superconducting wires, including wind turbines, motors, vehicle cables, and generators. The superconductor's magnetic properties could also make it suitable for compact fusion power plants.

 

Copper for Transmission Lines?

For transmission lines, copper wins over aluminum hands down in conductivity, but aluminum is much lighter and cheaper than copper. Aluminum cables have become the main choice for high-voltage transmission lines because they are much more suitable for wide-scale use. This leaves copper as the main choice in underground cabling applications where weight is not an issue.

As demand grows for more efficient energy distribution, could switching to copper eventually be the answer? Potentially, but not in its current state. Researchers are working on improving copper cabling’s properties and making it lighter weight. 

Pure copper doesn’t have great tensile strength, but adding graphene improves it. Strength is an issue in transmission lines because they are exposed to harsh elements like wind and storms.

Offsetting the extra cost of copper on a wider scale remains a problem. Still, if efficiency and electrical conductivity are key, engineers might need to develop advanced, lighter copper-based materials. Alternatively, they could seek out more advanced and electrically conductive aluminum materials. Having options on both sides—and the ability to make underground cables more efficient—gives engineers more choices in improving the grid’s reliability and performance in the coming years to meet society's increasing energy demands.

 

Copper Innovations for More Efficient Systems

While copper has potential in transmission and distribution applications if the right material comes along, the main research focus for copper-based materials has been improving small copper wires’ conductivity in motors, electric vehicles, and other technologies. Given copper’s static nature over the last century, any improvements in conductivity—even 5 to 10%—could mean a big efficiency increase when rolled out on a large scale, translating to lower emissions and energy usage.