Branching in the fracture of a h-BN sample. (J. Lou/Rice University) ======================================================================= A two-dimensional material with similar physical properties to graphene has now turned out to blow graphene out of the water in terms of toughness. The material is called hexagonal boron nitride (h-BN), and it's so resistant to cracking that scientists are gobsmacked. The finding flies in the face of the fundamental description of fracture mechanics that scientists have been using to predict and define toughness since the 1920s. "What we observed in this material is remarkable," said materials scientist Jun Lou of Rice University. "Nobody expected to see...