Russian scientists have described the structure of super-hard boride of tungsten

scientists have synthesized and investigated crystal structure and properties of boride tungsten WB5-x. Mechanical properties of the material were not significantly worse than the calculated values, which makes these materials promising for use in technical fields where need the solid and heat-resistant materials. The results of a study published in the journal Advanced Science.

For some tasks — for example, for continuous drilling — the hardness of a diamond is not enough. More durable and heat-resistant material may be a boride of tungsten. In the middle of the last century, scientists have reported the synthesis of tetraboride tungsten WB4, which contained a variety of phases with different stoichiometric ratios of atoms and crystal structures. Many subsequent studies of these compounds gave very different theoretical and practical results. Recent theoretical calculations using the algorithm USPEX, which has successfully proved in the description of the properties and the crystal structures of compounds difficult to synthesize, predicted the possibility of existence of stable pentaborane WB5.

To synthesize a crystal of tungsten boride single phase with the specified stoichiometry (the ratio of atoms in a crystal lattice) is very difficult because of the existence of this material polysomatism — the tendency to the formation of structures with multiple phases. Moreover, the definition of the exact position of boron atoms in the crystal lattice by x-ray diffraction analysis is difficult due to the large difference in the atomic masses of boron and tungsten. Therefore, still studying the crystal structure of the higher borides of tungsten remained challenging.

Alexander Kvashnin, (Alexander G. Kvashnin) with colleagues from SKOLKOVO Institute of science and technology synthesized boride of tungsten and investigated its crystal structure and mechanical properties. An example of the highest boride of tungsten were obtained by sintering tungsten and boron in the ratio of one to seven, with temperatures up to 1500 degrees Celsius and a pressure of up to seven GPA. For information about the crystal structure of the material, it was pulverized and analyzed by x-ray diffraction and compared these data with theoretical calculations of the structure of pentaborane.

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