Exploring Hardness and the Distorted sp² Hybridization of B–B Bonds in WB₃

Abstract

In this work, tungsten triboride (WB3) was successfully synthesized at high pressure and high temperature. The structure was reconfirmed to be WB3 (P63 mmc), and some part has a tungsten atomic defect according to the measurement results of X-ray diffraction, high-resolution transmission electron microscopy, and Rietveld refinement. The asymptotic Vickers hardness that had eliminated influence of excess boron is 25.5 GPa for WB3. This value is in good agreement with the previous theoretic results. Proof of novel electron transfer between the tungsten atom and the boron atom was found. A deficient amount of transfer electron induces distorted sp2 hybridization of B–B bonds in WB3. The weakly directional sp2 hybridization of B–B bonds is an essential factor that can influence the hardness of WB3. Our results are helpful to design new hard and superhard materials of transition metal borides.

Ultrastrong Boron Frameworks in ZrB12: A Highway for Electron Conducting

“…It is seen that the shear strengths of ZrB 12 are nearly isotropic within {111} planes with the minimum value of 34.5 GPa appearing along {111} [−1−12] deformation path, which is comparable to that of ReB 2 (34.4 GPa), WB 3 (37.7 GPa), and B 6 O (38 GPa) . Such results are in consistency with our experiments in which the asymptotic Vickers hardness of ZrB 12 (≈27 GPa) is only comparable to, if not lower than, those of ReB 2 (26.6 GPa) reported by Gu et al, WB 3 (25.5 GPa) by Tao et al and of W 1− x Ta x B by Yeung et al The hardness of these transition metal borides are however lower than those of B 6 O (45 GPa) and cBN (48 GPa), which can be attributed to their relatively lower shear strength with unique deformation path. The anisotropy of the shear strength along the selected five slip systems is estimated as τ (110) 〈1−10〉 :τ (1−10)〈−1−12〉 :τ (111)〈11−2〉: τ (111)〈−1−12〉 :τ (111)〈1−10〉 = 37.7:36.9:34.6:34.5:35.2, indicating an isotropic feature.…”

“…In this standard, ZrB 12 should be another boride with super hardness. On the other hand, with the increasing load, the hardness decreases gradually and approaches an asymptotic value of ≈27 GPa at 4.9 N, still higher than that of ReB 2 (26.6 and 20.0 GPa reported by different groups) and WB 4 (25.5 GPa). It should be mentioned that the asymptotic Hv values of all these borides are less than 40 GPa, the traditional threshold for superhard material .…”

Boron‐Induced Electronic‐Structure Reformation of CoP Nanoparticles Drives Enhanced pH‐Universal Hydrogen Evolution

“…Evidently, the withdrawing‐electron capacity of B from the bonded Co atom is weaker than that of P, which brings about fewer electrons of Co atom to participate in Co−B bonding and makes Co oxidation state in B‐CoP lower than that in CoP. In the high‐resolution B 1s XPS spectrum of the B‐CoP/CNT hybrid (Figure b), the peak of Co−B bond at 187.7 eV shifts about 0.2 eV negatively compared to the binding energy of pure B . Such results show the presence of Co−B bonds in B‐CoP, which conform to the calculated electron localization function (Figure S6).…”

Boron‐Induced Electronic‐Structure Reformation of CoP Nanoparticles Drives Enhanced pH‐Universal Hydrogen Evolution

“…[23] Note that B incorporation brings about an egative shift of approximately 0.3 eV in the binding energies of Co 2p 3/2 and Co 2p 1/2 ,which is attributed to the implantation of the low-electronegative B atoms into CoP.Evidently,the withdrawing-electron capacity of Bfrom the bonded Co atom is weaker than that of P, which brings about fewer electrons of Co atom to participate in CoÀ Bbonding and makes Co oxidation state in B-CoP lower than that in CoP.Inthe high-resolution B1sXPS spectrum of the B-CoP/CNT hybrid (Figure 2b), the peak of Co À Bb ond at 187.7 eV shifts about 0.2 eV negatively compared to the binding energy of pure B. [24] Such results show the presence of CoÀBb onds in B-CoP,w hich conform to the calculated electron localization function ( Figure S6). Note that, however,n os ignal belonging to the B À C bond can be observed, illustrating that Ba toms only insert into CoP rather than CNT,w hich is affirmed from the high-resolution C1sX PS spectrum ( Figure S5 b) (Figure 2c), signifying more electrons occupy P2p 3/2 of Pa toms caused by the enhanced electron-donating ability of Co atoms.…”