Enthalpies of Formation of Transition Metal Diborides:  A First Principles Study

Colinet, C.; Tedenac, Jean‐Claude

doi:10.3390/cryst5040562

Cited by 11 publications

(4 citation statements)

References 57 publications

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“…This tends to indicate that HfB 2 forms first out of the amorphous structure and its (001) acts as a low energy nucleation site for the HfN phase. Such a sequence of formation is consistent with the lower enthalpy of formation of HfB 2 compared to HfN 40 .…”

Section: Resultssupporting

confidence: 84%

Microstructure evolution in amorphous Hf-B-Si-C-N high temperature resistant coatings after annealing to 1500 °C in air

Shen

Jiang

Zeman

et al. 2019

Sci Rep

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Recently, amorphous Hf-B-Si-C-N coatings found to demonstrate superior high-temperature oxidation resistance. The microstructure evolution of two coatings, Hf 7 B 23 Si 22 C 6 N 40 and Hf 6 B 21 Si 19 C 4 N 47 , annealed to 1500 °C in air is investigated to understand their high oxidation resistance. The annealed coatings develop a two-layered structure comprising of the original as-deposited film followed by an oxidized layer. In both films, the oxidized layer possesses the same microstructure with HfO 2 nanoparticles dispersed in an amorphous SiO x -based matrix. The bottom layer in the Hf 6 B 21 Si 19 C 4 N 47 coating remains amorphous after annealing while Hf 7 B 23 Si 22 C 6 N 40 recrystallized partially showing a nanocrystalline structure of HfB 2 and HfN nanoparticles separated by h-Si 3 N 4 and h-BN boundaries. The HfB 2 and HfN nanostructures form a sandwich structure with a HfB 2 strip being atomically coherent to HfN skins via (111)-Hf monolayers. In spite of the different bottom layer structure, the oxidized/bottom layer interface of both films was found to exhibit a similar microstructure with a fine distribution of HfO 2 nanoparticles surrounded by SiO 2 quartz boundaries. The high-temperature oxidation resistance of both films is attributed to the particular evolving microstructure consisting of HfO 2 nanoparticles within a dense SiO x -based matrix and quartz SiO 2 in front of the oxidized/bottom layer interface acting as a barrier for oxygen and thermal diffusion.

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Section: Resultssupporting

confidence: 84%

Microstructure evolution in amorphous Hf-B-Si-C-N high temperature resistant coatings after annealing to 1500 °C in air

Shen

Jiang

Zeman

et al. 2019

Sci Rep

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“…Using the information obtained in sections , , and , four equations were proposed to explain ReB 2 degradation at oxygen and moisture ambient environmental conditions. Thermodynamic values for each compound were obtained from the literature . Thermodynamic analysis indicates that the Equations and are favored at environmental temperature, whereas the Equation is not favored at these conditions.…”

Section: Discussionmentioning

confidence: 99%

“…Thermodynamic values for each compound were obtained from the literature. [30][31][32][33][34] Thermodynamic analysis indicates that the Equations (1,2) and (4) are favored at environmental temperature, whereas the Equation (3) is not favored at these conditions. These results are consistent with the stability analysis in sections 3.2 and 3.3 and revealed why the Re from ReB 2 is converted into ReO 3 and HReO 4 (liquid), whereas B is converted into H 3 BO 3 and HBO 2 at oxygen and moisture ambient environmental conditions.…”

Section: Discussionmentioning

confidence: 99%

Chemical stability of superhard rhenium diboride at oxygen and moisture ambient environmental conditions prepared by mechanical milling

et al. 2018

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In this study, rhenium diboride (ReB2) was obtained by mechanosynthesis at 640 minutes of milling. The obtained ReB2 was stored at oxygen and moisture ambient environmental conditions to know the chemical stability. The results indicate that ReB2 is totally decomposed at oxygen and moisture ambient environmental conditions. Furthermore, the X‐ray diffraction (XRD) analysis of ReB2 samples after 26 months of storage shows that the final products of degradation are HReO4 (liquid), H3BO3, HBO2, and ReO3. Finally, a schematic diagram of the degradation sequence of ReB2 at oxygen and moisture ambient environmental conditions is proposed and validated with a thermodynamic analysis.

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“…The two dimensions (2Ds) material of MoB 4 (three layers of MoB 2 ) is a Dirac material, and layered stacking dominated by the borophene subunit also makes AlB 2 -type TMdBs the potential Mbene [44]. So, the AlB 2 -type structure is important to multifunction in TMdBs [12,13,[45][46][47][48][49][50][51].…”

Section: Introductionmentioning

confidence: 99%

Mechanical properties and multifunctionality of AlB₂-type transition metal diborides ^*

Li¹,

Zhao²,

Wang³

et al. 2022

J. Phys.: Condens. Matter

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Transition metal diborides (TMdBs, P6/mmm, AlB2-type) have attracted much attention for decades, due to TMdBs can be conductors, superconductors, magnetism materials, and catalysts. The layered structure caused by borophene subunit is the source of functions, and also make TMdBs be a potential bank of Mbene. However, TMdBs also exhibit high hardness which is not supposed to have in layered structure. The high hardness of TMdBs arise from covalent bonds of Boron-boron (B-B) and strong p-d orbit hybridization of B and TM. While, strong B-TM bonds will eliminate the layered structure which may damage the functional properties. Understanding the basic mechanism of hardness and functional is significant to achieve optimal TMdBs. In this work, the basic properties of TMdBs include hardness, superconductor, and catalytic property are summarized. It can be found that Youngs modulus (E) and Shear modulus (G) are beneficial for the hardness of TMdBs and Poisson ratio is the opposite. The increasing of atomic radius of TM brings the improvement for the hardness of TMdBs before it reaches the highest value 1.47 Å, beyond which hardness decreases. Besides, TMdBs also have excellent activity comparable with some noble metal for hydrogen evolution reaction, which is closely related with d-band center. More importantly, higher valence electron concentrations were found to be adverse for hardness and superconductivity of TMdBs and greatly affect their catalytic properties. This review is of guiding significance for the further explore the relation between structures and properties of TMdBs.

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Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

Cited by 11 publications

References 57 publications

Microstructure evolution in amorphous Hf-B-Si-C-N high temperature resistant coatings after annealing to 1500 °C in air

Microstructure evolution in amorphous Hf-B-Si-C-N high temperature resistant coatings after annealing to 1500 °C in air

Chemical stability of superhard rhenium diboride at oxygen and moisture ambient environmental conditions prepared by mechanical milling

Mechanical properties and multifunctionality of AlB₂-type transition metal diborides ^*

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Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

Cited by 11 publications

References 57 publications

Microstructure evolution in amorphous Hf-B-Si-C-N high temperature resistant coatings after annealing to 1500 °C in air

Microstructure evolution in amorphous Hf-B-Si-C-N high temperature resistant coatings after annealing to 1500 °C in air

Chemical stability of superhard rhenium diboride at oxygen and moisture ambient environmental conditions prepared by mechanical milling

Mechanical properties and multifunctionality of AlB2-type transition metal diborides *

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Mechanical properties and multifunctionality of AlB₂-type transition metal diborides ^*