Physicists have calculated the formula of the refractory material in the world

Physics computer simulated material whose melting point is higher than that of all known substances. About his study they told the journal Physical Review B.

A material which in certain proportions are mixed hafnium, nitrogen and carbon, will melt only at a temperature above 4400 Kelvin (4,127 degrees Fahrenheit). This is about two thirds of the surface temperature of the Sun and 200 degrees higher than the actual experiments demonstrated with other materials.

Previous record is an alloy of hafnium, tantalum and carbon (Hf-Ta-C). The new substance is to be synthesized only - to make sure the truth of a computer model.

The researchers made their discovery by simulating physical processes at the level of individual atoms. Under this approach, the dynamics of melting is studied in nanoscale scale - a group of about a hundred atoms.

Axel van der Walle (Axel van de Walle) from Brown University and his colleagues began by analyzing the alloy Hf-Ta-C, whose properties were already known. Computer modeling has helped to clarify the specific factors that give the material a record heat resistance.

It was found that Hf-Ta-C high heat of fusion (energy that is absorbed during the transition from solid to liquid state) is combined with a slight difference between the values ​​of entropy in these two phases. “Melt materials makes entropy, accumulated during the phase transition. If the level of entropy in the solid state has great substance thus stabilized, and its melting point - increases,” - explains van der Walle.

The researchers then began to search for compounds that can maximize the properties of the alloy. It was found that the compound of hafnium, carbon and nitrogen will have almost as high a heat of fusion, and even less the difference between the entropy of the solid and gaseous state. Calculations have shown that the new melting point substance will be 200 degrees higher than that of alloy Hf-Ta-C.

Opening the van der Walle could theoretically form the basis of new materials with improved characteristics - from coatings for gas turbines and ending heat shield high-speed aircraft. However, the value of the alloy is far from obvious. “The melting point - this is not the only property having a value for the practical use of the substance. We must take into account the mechanical properties, corrosion resistance, other features - all of which can reduce the melting point. However, if you just set the bar high in this area, scientists have more freedom to adjust other properties. Approximately so I imagine the course of further work “- explains van der Walle.

29 July 2015

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