Using computer simulations, Brown University researchers identified the material with the highest known melting point. The material, made with just the right amount of hafnium, nitrogen, and carbon would have a melting point of more than 4,400 kelvins (7,460 degrees Fahrenheit). That’s almost as high as the temperature at the surface of the Sun, and more than the highest temperature ever achieved by humans.
Pictured above, hafnium was a key element in the mixture. Picture credits: Images of Elements.
The melting point is pretty much what the name says: the temperature at which a solid becomes liquid at atmospheric pressure; at exactly the melting point, the solid and liquid phases exist in equilibrium.
Mixing different materials together dramatically changes the melting point, but predicting what materials will have the highest melting point is like looking for a needle in a hay stack – this is why researchers didn’t just blindly start mixing substances.
“The advantage of starting with the computational approach is we can try lots of different combinations very cheaply and find ones that might be worth experimenting with in the lab,” said Axel van de Walle, associate professor of engineering and co-author of the study with postdoctoral researcher Qijun Hong. “Otherwise we’d just be shooting in the dark. Now we know we have something that’s worth a try.”
The technique they used analyzes the melting dynamics on a small scale, in blocks of 100 or so atoms. The technique is more efficient than traditional methods, but requires massive computational resources.
Having materials with high melting points is crucial in a number of industries, from plating for gas turbines to heat shields on high-speed aircraft. But researchers won’t know if the material is actually a useful one until they create it – and that’s the next step. There are other properties worth considering.
“Melting point isn’t the only property that’s important [in material applications],” he said. “You would need to consider things like mechanical properties and oxidation resistance and all sorts of other properties. So taking those things into account you may want to mix other things with this that might lower the melting point. But since you’re already starting so high, you have more leeway to adjust other properties. So I think this gives people an idea of what can be done.”
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