A rare earth material used in the new generation of small antennas is in danger of overheating and melting at room temperature.

The problem is due to the new antennas, which are smaller than standard ones, being made from highly-resistant carbon nanotubes.

It has been a problem since 2006, when the US Air Force began using the material in small radar-sensing antennas.

A company in Japan has now identified a few problems with the carbon nanosheets that have been detected in one particular batch of about 20,000.

“The manufacturing process is not as clean as it should be and the carbon material is very brittle and does not perform as well as it used to,” said Tetsuo Yoshimura, who heads the company’s research and development arm.

Yoshimura said the company is working with the US government to investigate.

There are no known causes for the problem.

Japan’s National Institute of Radiological Protection and Nuclear Safety has been monitoring the problem, according to the Reuters news agency.

But it is too early to determine whether the problem is limited to one batch, Yoshimura said.

Japanese scientists have also found that the carbon in the samples used in new antennas has been degraded, so that they are more susceptible to overheating.

They have also noticed that the new material is harder to work with, he added.

Other problems with older semiconductors used in small antennas include melting or cracking at room temperatures, a defect known as “sink temperature”.

The material is known to be very brittle at room pressure.

However, Yoshimi said, the materials in the older semiconductor were manufactured at a much lower temperature, so the problem would be unlikely to affect the newer material.

At least three manufacturers of small radar antennas have already confirmed the problems with their new materials.

In Japan, the National Institute for Radiological Safety has said the problem could be “caused by an excessive exposure to air” at high temperatures.

(Reporting by Kiyoshi Matsumoto; Editing by Stephen Powell)