Electronic Structure and Mechanical Properties of NiB: A Promising Interphase Material for Future UHTCf/UHTC Composites

Weak interphases play a pivotal role by acting as mechanical fuse to deflect matrix cracks in future ultrahigh-temperature ceramic fiber reinforced ceramic matrix ( UHTCf/UHTC) composites. However, the interphase materials are not available yet. In this work, the electronic structure, chemical bonding, and mechanical properties of NiB, which is a promising interphase material for UHTCf/UHTC composites, were investigated. NiB has relatively low shear modulus of 116 GPa, moderate Young's modulus of 307 GPa, but high bulk modulus of 287 GPa. The Pugh's ratio G/B is only 0.404 and the micro hardness is predicted to be 8.2 GPa, indicating that NiB belongs to soft and ductile UHTCs. The possible slip systems are [ 100]( 001), [ 010] ( 001), and [ 001]( 010) due to the presence of metallic Ni-Ni and weak Ni-B bonding. Details on the electronic structure and directional dependence of shear and Young's moduli are disclosed to highlight the mechanisms that underpin the properties.