The ampacity is boosted to 10,000 per cent

New research has emerged from the National Institute of Advanced Industrial Science and Technology (AIST), Japan, which makes possible lighter conductors that can carry larger currents.

Led by an Indian chemist, researchers have found that when carbon nanotubes are embedded in copper, the resulting new material’s ampacity gets boosted to a massive 10,000 per cent, with an electrical conductivity comparable to copper’s.

Maximum current

Ampacity is the maximum amount of current a conductor can carry before losing its electrical properties. A large ampacity is vital to good performance. However, of late, researchers worldwide have focused more on boosting conductivity than ampacity.

In an email to this Correspondent, Dr. Subramaniam Chandramouli of AIST explained: “A material with higher ampacity and which is simultaneously conductive is required to withstand, handle and transport the increasing current densities of modern electronics.” He is the lead author of a paper published in Nature Communications on July 23.

Less dense

The new material, dubbed CNT-Cu (for carbon nanotubes–copper), consists of 45 per cent CNTs by volume, and is less dense than a pure copper conductor by 42 per cent. To produce it, the researchers electrodeposited copper into the pores of macroscopic CNT solids such as buckypaper.

This method is more prolonged and costlier than conventional methods like ion dispersion. Dr. Chandramouli thinks this is the only hurdle for commercially deploying CNT-Cu.

“There is a dominant processing cost. We are now trying to reduce it and make it more appealing to industries.

An advantage of the material is that it reduces the amount of copper required and provides 100 times higher performance. So we expect that the cost-by-performance of this material will be acceptable to industries,” he said.

Copper conductors are assailed by a mechanism called electromigration that suppresses its ampacity.

As electrons move inside the conductor, they are often scattered by atoms in their path. As the current density increases, scattering also increases until, at a threshold called the conductor’s rating, the material can no longer conduct the electrons, resulting in electromigration.

Higher ampacity

CNT-Cu achieves higher ampacity by suppressing electromigration that occurs in copper wires, where electrons are scattered off their path by copper atoms. This imposes a limit on the amount of charge the wire can carry without most electrons getting scattered, called its rating.

In case of CNT-Cu, the negatively charged particles are channeled to move through a continuous mesh-like network formed by the nanotubes, averting scattering.

In this circumstance, the rating accommodates an ampacity of 600 MA/cm. The paper notes that ampacity of up to 1,200 MA/cm is theoretically possible.

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