Marc Ewenz Rocher, tells us about an exciting collaboration between the University of Oxford, Imperial College London and the University of Stuttgart.

In this experiment, a porous ZrB2 sample was sealed into a copper dome and placed inside a plasma wind tunnel as shown in Figure 1. The wind tunnel generates a very hot flow, which heats up the sample to 2000 °C. You can see a picture of this in Figure 2.

Figure 1

Figure 2

The sample discolours to white, because its surface undergoes oxidation as shown in Figure 3. Essentially what happens is that Oxygen damages the material at temperatures higher than 700°C and you see this in the form of discolouration.

The team repeated the experiment, but this time they fed a gas through the porous sample – a method called transpiration cooling. The results show that oxidation of the sample is prevented with this exciting new approach to cooling (Figure 4).

Figure 3 Uncooled Sample with Oxidised Surface

Figure 4 Transpiration Cooled Sample with Undamaged Surface

Marc tells us that the experiment was a great success. By avoiding oxidation, the team are able to heat the ZrB2 ceramic right upto its melting point of 3200 °C (a whopping 2500 °C higher than before!).

Transpiration cooling is a key technology for the design of extremely fast planes that could fly from London to Sydney in less than four hours.