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

Abstract

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.

Y5Si2B8: A theoretically predicted new damage‐tolerant MAB phase with layered crystal structure

“…Figure A shows the band structure of Y 5 Si 2 B 8 . Similar to other transition metal borides, other MAB phases and MAX phases, valence and conduction bands overlap across the Fermi level, implying the presence of metallic bonding and metallic conductivity in Y 5 Si 2 B 8 . The finite states at Fermi level in the total density of states curve (Figure B) also indicate the presence of metallic bond in Y 5 Si 2 B 8 .…”

“…Ultrahigh‐temperature ceramics (UHTCs) based on transition metal borides are regarded as the materials of choice for the nose tip and sharp leading edges of hypersonic vehicles, hot structure components for scramjet engines, matrix and/or surface coatings for ultrahigh‐temperature ceramic matrix composites (carbon fiber reinforced ultrahigh‐temperature ceramic matrix (C f /UHTC) composites and ultrahigh‐temperature ceramic fiber reinforced ultrahigh‐temperature ceramic matrix UHTC f /UHTC composites) . However, the intrinsic brittleness and poor thermal shock resistance have blocked their near‐term applications in hypersonic vehicles.…”

Mechanical Properties, Electronic Structures, and Debye Temperature of NixBy Compounds Obtained by the First Principles Calculations

“…Zhou et al [16] researched the stability, electronic, and structural properties of X 2 B (X = Cr, Mn, Fe, Co, Ni, Mo, and W) compounds. Zhou et al [17] investigated the electronic structure and mechanical properties of NiB, which is predicted to be a promising interphase material for future ultrahigh-temperature ceramic fiber reinforced ceramic matrix (UHTCF/UHTC) composites. However, there is no literature that studied the effects of different ratios of Ni to B on the mechanical properties, electronic properties, and Debye temperature of Ni x B y compounds.…”

Electrical conductive and damage-tolerant nanolaminated MAB phases Cr2AlB2, Cr3AlB4 and Cr4AlB6

“…In addition, the shear modulus associated to (010) [001] and (001)[010] is as low as 132 GPa, indicating that these systems might also be possible slip systems of Cr 2 AlB 2 . For Cr 3 (Figure 2(d)) and G min = 148 GPa for Cr 4 As shown in Table 2, bulk modulus of polycrystalline (CrB 2 ) n CrAl (n = 1-3) increases from 220 GPa for Cr 2 AlB 2 and 237 GPa for Cr 3 AlB 4 to 254 GPa for Cr 4 AlB 6 , which are close to those of UHTCs like TMB 2 (TM = Ti, Zr, Hf, Nb and Ta) [10] and NiB [24], but much higher than those of MAX phases. The shear moduli, however, are in a same level, being 163, 182 and 179 GPa for Cr 2 AlB 2 , Cr 3 AlB 4 and Cr 4 AlB 6 , respectively.…”

“…Figure 4 shows the electron density difference maps, which illustrate the charge redistribution due to chemical bonding, on (002) and (100) planes of Cr 2 AlB 2 , (010) and (100) planes of Cr 3 AlB 4 and (002) and (100) planes of Cr 4 AlB 6 . Similar to NiB [24], the bonding in the zigzag B-B chains of Cr 2 AlB 2 is strong covalent bond formed by overlapping of B sp 2 -B sp 2 orbitals. Since the B-B bond chains are parallel to [100] direction (Figure 4(a)), the stiffness is the highest in [100] (high c 11 and E x ).…”