Modulating Hardness in Molybdenum Monoborides by Adjusting an Array of Boron Zigzag Chains

Tang, Qiang; Chen, Yanli; Lian, Min; Xu, Chao; Li, Li; Feng, Xiaokang; Wang, Xin; Cui, Tian; Zheng, Weitao; Zhu, Pinwen

doi:10.1021/acs.chemmater.8b04154

Cited by 24 publications

(15 citation statements)

References 36 publications

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“…Diborides (TMB 2 ) and transition metal tetraborides (TMB 4 ) have been widely investigated over the last years . However, the reported Vickers hardness of TMB 2 or TMB 4 is difficult to meet the requirement of superhard material . Naturally, the Vickers hardness of TMBs mainly relies on the shorter and network covalent bonds.…”

Section: Introductionmentioning

confidence: 99%

Influence of alloying elements on the mechanical and thermodynamic properties of ZrB₁₂ceramics from first‐principles calculations

Pan

Lin

2020

Int J of Quantum Chemistry

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Although ZrB 12 is a promising advanced material because of the boron cuboctahedron cages, the hardness of ZrB 12 remains controversy. Here, we apply first-principles calculations to study the influence of transition metals (4d-and 5d-) on the hardness and thermodynamic properties of ZrB 12 . The calculated hardness of ZrB 12 is 32.9 GPa, which is in good agreement with the previous theoretical result. Importantly, the calculated hardness of Re-doped ZrB 12 is up to 40.0 GPa, which is a potential superhard material. The essential reason is that the alloying element of Re enhances the localized hybridization of B B and Zr B atoms, and then forms the strong B B covalent bond and Zr B bond. The result is well demonstrated by the chemical bonding and lattice parameter. Here, our work shows that the alloying elements of Nb, Mo, and Re enhance the thermodynamic properties of ZrB 12 . The Debye temperature of Re-doped ZrB 12 is 1225.2 K, which is larger than that of the parent ZrB 12 (1213.5 K). K E Y W O R D S borides, elastic modulus, first-principles calculations, hardness, thermodynamic properties, ZrB 12 1 | INTRODUCTION Hard and superhard materials (≥40 GPa) are very important industrial materials, which are widely used in various industrial applications because of their high hardness, ultracompressibility, high melting point, and excellent thermal stability etc. [1-10] In comparison to diamond and boron nitride (c-BN), the transition metal borides (TMBs) are attractive potential superhard materials because of the network and shorter covalent bonding such as B B covalent bond and TM B bond. [11][12][13][14][15][16][17][18][19] Diborides (TMB 2 ) and transition metal tetraborides (TMB 4 ) have been widely investigated over the last years. [20][21][22][23][24] However, the reported Vickers hardness of TMB 2 or TMB 4 is difficult to meet the requirement of superhard material. [25][26][27][28][29] Naturally, the Vickers hardness of TMBs mainly relies on the shorter and network covalent bonds. In other words, the high concentration of boron plays a crucial role in Vickers hardness of TMBs. Among these TMBs, it is obvious that the transition metal dodecaborides (TMB 12 ) are potential superhard materials in comparison to TMB 2 and TMB 4 .Recently, ZrB 12 has evoked great interest because of the high concentration of boron and the network B B covalent bonds. [30] This dodecaboride is composed of the boron cuboctahedron cage (24 atoms) and 12-coordinate transition metals at the center of cubic structure. This structural feature is possible to enhance the Vickers hardness of TMBs. However, the Vickers hardness of ZrB 12 remains controversy. Korozlu et al. have found that the calculated Vickers hardness of ZrB 12 is 40.1 GPa, which is believed to a potential superhard material. [31] However, the recent works have shown that the Vickers hardness of ZrB 12 is 35.4 GPa by Chen et al. [32] and 29.3 GPa by Li et al., [33] which are different from Korozlu's result. On the other hand, even if the Vickers hardness of ZrB 12 remains...

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Section: Introductionmentioning

confidence: 99%

Influence of alloying elements on the mechanical and thermodynamic properties of ZrB₁₂ceramics from first‐principles calculations

Pan

Lin

2020

Int J of Quantum Chemistry

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“…The hardness is increased by 35% compared to that of orthorhombic molybdenum monoboride and 9% compared to that of hexagonal molybdenum diboride. This hardness is equivalent to that of tetragonal molybdenum monoboride with a similar structure . Its hardness is 32% higher than that of no-pinning-layered MnB 2 .…”

Section: Resultsmentioning

confidence: 82%

“…This hardness is equivalent to that of tetragonal molybdenum monoboride with a similar structure. 18 Its hardness is 32% higher than that of no-pinning-layered MnB 2 . 35 The results show that materials with a low boron concentration have higher hardness.…”

Section: Resultsmentioning

confidence: 93%

“…In addition, excellent electrical conductivity and superconductivity characteristics exist in the abundant molybdenum boride system. Therefore, molybdenum borides, such as MoB, MoB 2 , and MoB 4 , have received considerable attention. ,− Transition metal semiborides (TM 2 B) usually employ a tetragonal CuAl 2 type structure ( I 4/ mcm ), which are considered to be materials with different magnetic states . This indicates that metal-rich borides also have versatility.…”

Section: Introductionmentioning

confidence: 99%

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Revealing the Unusual Boron-Pinned Layered Substructure in Superconducting Hard Molybdenum Semiboride

Bao

et al. 2021

ACS Omega

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Improving the poor electrical conductivity of hard materials is important, as it will benefit their application. High-hardness metallic Mo 2 B was synthesized by high-pressure and high-temperature methods. Temperature-dependent resistivity measurements suggested that Mo 2 B has excellent metallic conductivity properties and is a weakly coupled superconductor with a T c of 6.0 K. The Vickers hardness of the metal-rich molybdenum semiboride reaches 16.5 GPa, exceeding the hardness of MoB and MoB 2 . The results showed that a proper boron concentration can improve the mechanical properties, not necessarily a high boron concentration. First-principles calculations revealed that the pinning effect of light elements is related to hardness. The high hardness of boron-pinned layered Mo 2 B demonstrated that the design of high-hardness conductive materials should be based on the structure formed by light elements rather than high-concentration light elements.

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“…Boron-rich compounds make up an important class of functional materials with intriguing physicochemical properties such as chemical inertness, high thermal stability, high hardness, superconductivity, and the ability to be semiconducting, thermoelectric, and catalytic. − In these compounds, the electron-deficient boron is readily bonded with the guest atoms to form diverse complex structures. Fundamentally, understanding the precise structures and compositions of boron-rich compounds is quite important, because the structural parameters provide the direct basis for understanding the synthesis and growth mechanism, phase evolution and development, chemical bonding, and functionalities.…”

Section: Introductionmentioning

confidence: 99%

Boron-Rich Molybdenum Boride with Unusual Short-Range Vacancy Ordering, Anisotropic Hardness, and Superconductivity

et al. 2019

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Determination of the structures of materials involving more light elements such as boron-rich compounds is challenging and technically important in understanding their varied compositions and superior functionalities. Here we resolve the long-standing uncertainties in structure and composition about the highest boride (termed MoB4, Mo1–x B3, or MoB3) through the rapid formation of large-sized boron-rich molybdenum boride under pressure. Using high-quality single-crystal X-ray diffraction analysis and aberration-corrected scanning transmission electron microscopy, we reveal that boron-rich molybdenum boride with a composition of Mo0.757B3 exhibits P63/mmc symmetry with a partial occupancy of 0.514 in 2b Mo sites (Mo1), and direct observations reveal the short-range ordering of cation vacancies in (010) crystal planes. Large anisotropic Young’s moduli and Vickers hardness are seen for Mo0.757B3, which may be attributed by its two-dimensional boron distributions. Mo0.757B3 is also found to be superconducting with a transition temperature (T c) of ∼2.4 K, which was confirmed by measurements of resistivity and magnetic susceptibility. Theoretical calculations suggest that the partial occupancy of Mo atoms plays a crucial role in the emergence of superconductivity.

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Modulating Hardness in Molybdenum Monoborides by Adjusting an Array of Boron Zigzag Chains

Cited by 24 publications

References 36 publications

Influence of alloying elements on the mechanical and thermodynamic properties of ZrB₁₂ceramics from first‐principles calculations

Influence of alloying elements on the mechanical and thermodynamic properties of ZrB₁₂ceramics from first‐principles calculations

Revealing the Unusual Boron-Pinned Layered Substructure in Superconducting Hard Molybdenum Semiboride

Boron-Rich Molybdenum Boride with Unusual Short-Range Vacancy Ordering, Anisotropic Hardness, and Superconductivity

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Modulating Hardness in Molybdenum Monoborides by Adjusting an Array of Boron Zigzag Chains

Cited by 24 publications

References 36 publications

Influence of alloying elements on the mechanical and thermodynamic properties of ZrB12ceramics from first‐principles calculations

Influence of alloying elements on the mechanical and thermodynamic properties of ZrB12ceramics from first‐principles calculations

Revealing the Unusual Boron-Pinned Layered Substructure in Superconducting Hard Molybdenum Semiboride

Boron-Rich Molybdenum Boride with Unusual Short-Range Vacancy Ordering, Anisotropic Hardness, and Superconductivity

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Influence of alloying elements on the mechanical and thermodynamic properties of ZrB₁₂ceramics from first‐principles calculations

Influence of alloying elements on the mechanical and thermodynamic properties of ZrB₁₂ceramics from first‐principles calculations