Boron carbide is used in the design of planes, trains, and cars.
University of Seville researchers, led by professor Francisco Luis Cumbrera, together with colleagues from the University of Zaragoza and CSIC, have found a procedure for producing the phase B6C of boron carbide. This phase had been described from a theoretical point of view, but obtaining it and describing its character were a task that remained unfulfilled. This scientific-technological advance will make it possible to provide a cheap, ultra-resistant material for the design of planes, cars, and other means of transport. In addition, B6C is also ultra-resistant to radioactivity.
BxC is a family of ceramic materials known as “boron carbide.” The “official” or canonical member (in scientific language, stoichiometric) is B4C. This is a very hard black solid, which remains stable at very high temperatures. The family is big: from B4C to B14C. Depending on the proportion of B (boron) and C (carbon), its physical properties change. B6C is a member of the family (phase B6C) with 6 boron atoms to each one of carbon and theoretically it had been deemed that it would be ultra-resistant. Until now, a way to produce it systematically had not been found, nor how to distribute the boron and carbon atoms internally.
The material has been made using the technique of laser zone floating, which consists of fusion by means of the application of intense laser radiation and then rapid solidification. Such an idea was proposed by Bibi Malmal Moshtaghion, a researcher trained in Iran and in Seville with a Juan de la Cierva contract to work at the University of Zaragoza. Professor Cumbrera’s team has used X-ray diffraction techniques to characterize the crystallography of the samples obtained and the defects present in them, as well as the possible preferential ordering of the polycrystal grains. Later, its mechanical properties were determined by both teams. The phase B6C obtained in this way possesses a hardness of 52 GPa and a Young modulus of 600 GPa. In comparison, the hardness of diamond is around 45 GPa, although it has a Young modulus of 1050 GPa. “This makes phase B6C the hardest material in nature after diamond and the cubic phase of boron nitride,” the researchers state.
Reference: “Elusive super-hard B6C accessible through the laser-floating zone method” by Bibi Malmal Moshtaghioun, Francisco L. Cumbrera, Diego Gómez-García and Jose I. Peña, 16 September 2019, Scientific Reports.