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German researchers are working on a super-efficient heat-absorbing material that could be used in fusion reactors and rocket nozzles.

The heat-sink composite of copper reinforced with silicon carbide fibres could also be used to remove excess heat in electronic circuits. This would enable chips to be stacked on top of each other for increased processing power.

Dr. Harald Bolt of the Max-Planck Institute for Plasma Physics in Munich said researchers have been aiming for some time to create a heat- conductive material that can withstand the tough environment of a fusion reactor.

‘For fusion you need high strength, high conductivity and high temperature resistance. Titanium is not a good conductor so we need to use copper. But copper is not strong and we need it to operate at 500 degrees C. So we use fibre reinforcement. And those are silicon carbide fibres.’

The copper silicon carbide would efficiently conduct heat and stay strong at high temperatures. However, the problem Bolt’s team must overcome is that copper does not bond with carbon.

To solve this a nano-scale film will be used to act as an interface and join them together. The film will enable the materials to be meshed in a matrix.

Although Bolt would not reveal what the film would be made of he said the copper would be placed on the film using a vapour deposition process and the whole ‘sandwich’ would then be pressed.

In a fusion reactor the composite would sit behind a 1mm-thick tungsten interior reactor wall absorbing up to 20 per cent of the fusion plasma’s heat.

This would then be transferred to the helium or water pipes embedded in the reactor wall. The heat would turn the water or helium in the wall into super-heated gases to drive a power turbine.

The possible applications for a material that is both heat resistant and capable of rapidly absorbing heat energy are wide and varied.

Rocket thruster exhaust nozzles like those on the Space Shuttle have to be replaced after each flight. Bolt claims the copper silicon carbide composite would allow them to be reused up to 20 times as they would remain cooler for longer.

Heat stress from the engine’s hot gases would normally degrade the nozzle. But with the new material heat from the combustion process can pass much more quickly through the nozzle to the fuel that circulates around it. This is done to keep the engine cool and preheat the fuel for combustion.

The research will be funded by the EU’s Materials for Extreme Environments programme. Other member states will contribute to Bolt’s project.

With the help of new computer modelling techniques he expects the composite to be ready within five years. Normally it could take more than ten.