Simple, Green, and High‐Yield Production of Boron‐Based Nanostructures with Diverse Morphologies by Dissolution and Recrystallization of Layered Magnesium Diboride Crystals in Water

Gunda, Harini; Das, Saroj Kumar

doi:10.1002/cphc.201701033

Cited by 41 publications

(77 citation statements)

References 90 publications

(195 reference statements)

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“…In recent years, the metal diborides along with other boron-based compounds, have been gaining renewed attention from chemists who have been studying their electrochemical properties and potential for alternative low-temperature and solution-based processing routes. [26][27][28][29][30][31][32][33][34] The layered structure of the metal diborides with their graphene-like boron sheets suggests the possibility of exfoliation into thin 2D nanosheets. The ability to produce metal diborides as 2D nanosheets using mild processing conditions could provide an attractive new route to applying these materials and extending their use to new contexts.…”

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confidence: 99%

Exfoliation of Quasi-Two-Dimensional Nanosheets of Metal Diborides

et al. 2021

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The metal diborides are a class of ceramic materials with crystal structures consisting of hexagonal sheets of boron atoms alternating with planes of metal atoms held together with mixed character ionic/covalent bonds. Many of the metal diborides are ultrahigh temperature ceramics like HfB2, TaB2, and ZrB2, which have melting points above 3000ºC, high mechanical hardness and strength at high temperatures, and high chemical resistance, while MgB2 is a superconductor with a transition temperature of 39 K. Here we demonstrate that this diverse family of non-van der Waals materials can be processed into stable dispersions of two-dimensional (2D) nanosheets using ultrasonication-assisted exfoliation. We generate 2D nanosheets of the metal diborides AlB2, CrB2, HfB2, MgB2, NbB2, TaB2, TiB2, and ZrB2, and use electron and scanning probe microscopies to characterize their structures, morphologies, and compositions. The exfoliated layers span up to micrometers in lateral dimension and reach thicknesses down to 2-3 nm, while retaining their hexagonal atomic structure and chemical composition. We exploit the convenient solution-phase dispersions of exfoliated CrB2 nanosheets to incorporate them directly into polymer composites. In contrast to the hard and brittle bulk CrB2, we find that CrB2 nanocomposites remain very flexible and simultaneously provide increases in the elastic modulus and the ultimate tensile strength of the polymer. The successful liquid-phase production of 2D metal diborides enables their processing using scalable low-temperature solution-phase methods, extending their use to previously unexplored applications, and reveals a new family of non-van der Waals materials that can be efficiently exfoliated into 2D forms.The metal diborides are a family of ceramic compounds with the general formula MB2, where M can be a variety of metals from Groups II, IVB and VB such as Hf, Cr, Ti, Zr, Mg, etc.The most common crystal structure for these materials is the AlB2 type, belonging to the P6/mmm space group symmetry, which has the boron atoms in covalently bound hexagonal sheets separated by layers of close-packed metal atoms, 1 as shown in Figure 1a. The interactions between the

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Exfoliation of Quasi-Two-Dimensional Nanosheets of Metal Diborides

et al. 2021

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“…To validate the predicted disordering of B surface atoms, we synthesized MgB 2 nanosheets (NSs) with predominant boron surface termination through mechanical exfoliation using high-energy ball milling, followed by dispersion in acetonitrile and subsequent centrifugation (see “Methods”) 30 . Using transmission electron microscopy (TEM) and atomic force microscopy (AFM), we determined that the exfoliated MgB 2 NSs were flat with lateral dimensions ranging from 100 to 500 nm and thicknesses of ~4 nm (Fig.…”

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confidence: 99%

Spontaneous dynamical disordering of borophenes in MgB2 and related metal borides

Gunda

Ray

et al. 2021

Nat Commun

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Layered boron compounds have attracted significant interest in applications from energy storage to electronic materials to device applications, owing in part to a diversity of surface properties tied to specific arrangements of boron atoms. Here we report the energy landscape for surface atomic configurations of MgB2 by combining first-principles calculations, global optimization, material synthesis and characterization. We demonstrate that contrary to previous assumptions, multiple disordered reconstructions are thermodynamically preferred and kinetically accessible within exposed B surfaces in MgB2 and other layered metal diborides at low boron chemical potentials. Such a dynamic environment and intrinsic disordering of the B surface atoms present new opportunities to realize a diverse set of 2D boron structures. We validated the predicted surface disorder by characterizing exfoliated boron-terminated MgB2 nanosheets. We further discuss application-relevant implications, with a particular view towards understanding the impact of boron surface heterogeneity on hydrogen storage performance.

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“…Generally, there are three effective routes to introduce functionalization: (i) topdown synthesis of boron nanosheets using a liquid/gas phase exfoliation method; (ii) bottom-up chemical vapor deposition or molecular beam epitaxy in a certain atmosphere; (iii) ligand exchange aer obtaining boron nanosheets. 15,[43][44][45][46]…”

Section: Chemical Functional Groupsmentioning

confidence: 99%

“…76 OH functionalization can be simply achieved by immersing or fabricating boron nanosheets within aqueous solutions. 43,[77][78][79][80] In 2017, Kondo et al prepared hydroxyl-functionalized boron nanosheets (B-OH) by an ion exchange reaction in water. 79 The ion-exchange reaction between protons in water and some of the Mg cations was followed by a hydrolysis reaction between the HB and water, producing H 2 and Mg-decient hydroxylfunctionalized boron sheets.…”

Section: Hydroxylated Boron Nanosheetsmentioning

confidence: 99%