Years ago, I was taking a tour of Edwards Air Force base, which is situated on a vast dry lake bed in Southern California, which gives ample leeway for testing of new aircraft.
Aside from a storied history of flight testing, the base is home to a lot of different “birds,” and you never quite know what you are going to see — everything from B-2 bombers, to the latest fighter jets.
(Astronaut Gordon Cooper admits to seeing a UFO land on the dry lake bed, where it sat briefly, and took off again!)
But on this particular tour, we were standing in front of a deep-black SR-71 Blackbird spy plane on the tarmac, the first time I had ever seen such a beast in person.
As I hurriedly snapped photos, what I recall is the guide telling us, that the refuelling crews hate working with the SR-71, for the very scary reason, that it constantly leaks fuel.
This is because the tanks don’t expand and seal, until the SR-71 takes flight and heats up at at its Mach 3.4 top speed — a terrifying sight for any tanker crew in the SoCal heat.
Well, leave it to our Aussie friends, to come up with a startling solution to the SR-71s expanding fuel tank issue, and many other potential applications as well.
This new zero thermal expansion (ZTE) material made of scandium, aluminum, tungsten and oxygen did not change in volume at temperatures ranging from 4 to 1,400 Kelvin (-269 to 1126 °C, -452 to 2059 °F), the report said.
That’s a wider range of temperatures than any other material demonstrated to date, and it could make orthorhombic Sc1.5Al0.5W3O12 (hopefully, they come up with a better name) a very handy tool for anyone engineering something that needs to work in extremely varied thermal environments.
Examples of where this might come in handy include things like aerospace design, where components are exposed to extreme cold in space and extreme heat at launch or on re-entry.
This new material stays exactly the same volume from close to absolute zero all the way up to comfortably over the heat you’d expect to get on the wing of a hypersonic aircraft traveling at Mach 5.
Or there’s things like medical implants, where the range of expected temperatures isn’t so varied but even a small amount of thermal expansion can cause critical issues, the report said.
Perhaps the greatest part about this discovery is that it was made completely by accident.
“We were conducting experiments with these materials in association with our batteries-based research, for unrelated purposes, and fortuitously came across this singular property of this particular composition,” says Associate Professor Neeraj Sharma.
After measuring the material using the Echidna high-resolution powder diffractometer at ANSTO’s Australian Synchrotron and the Australian Centre for Neutron Scattering, the team found an incredible degree of thermal stability, the report said.
At the molecular level, materials usually expand because an increase in temperature leads directly to an increase in the length of the atomic bonds between elements. Sometimes it also causes atoms to rotate, resulting in more spacious structures that affect the overall volume.
Not with this stuff, which the team observed across that huge temperature spectrum demonstrating “only minute changes to the bonds, position of oxygen atoms and rotations of the atom arrangements,” the report said.
The team says the exact mechanism behind this extreme thermal stability isn’t totally clear, but that perhaps bond lengths, angles and oxygen atom positions are changing in concert with one another to preserve the overall volume.
“Which part’s acting at which temperature, well, that’s the next question,” says Sharma, who adds, “the scandium is rarer and more costly, but we are experimenting with other elements that might be substituted, and the stability retained.”
The other ingredients, however, are widely available, and bond together using a “relatively simple synthesis,” so the team believes this material should present no impediments to large-scale manufacturing.
Sources: NewAtlas.com, Interesting Engineering, Lockheed Martin, Chemistry of Materials