High‐Yield Synthesis of Rhombohedral Boron Nitride Triangular Nanoplates

Abstract

Synthesis of nanometer-scale materials with controlled size and morphology has attracted prime attention in nanomaterials research owing to the nanostructural morphology-dependent physical properties.[1] In addition to zero-dimensional (0D) quantum dots and 1D nanorods (or nanowires), [2] there have been a few examples of 2D elemental and compound nanostructures, such as Ag, Au, Pd, LnF 3 , Bi 2 Te 3 , Sb 2 Te 3 , In 2 S 3 , CdS, NiS, and ZnO nanoplates. [3,4] Boron nitride has attracted continuous attention over the last three decades. Owing to its good mechanical, thermal, and chemical properties, BN is a widely used material in vacuum technology. It has also been employed in microelectronic devices, for X-ray lithography masks and as a wear-resistant lubricant.[5] Similar to carbon, BN can form sp 2 -bonded hexagonal BN (h-BN) and rhombohedral BN (r-BN) or sp 3 -bonded wurtzite BN (w-BN) and cubic BN (c-BN). In contrast to graphite, which exhibits a semimetallic behavior, all BN forms have a wide bandgap, which makes BN a promising candidate for deep-blue and UV applications.[6] BN nanostructures with a well-defined geometry and highly crystalline nature, such as 1D nanotubes, can be obtained using hightemperature chemical vapor deposition (CVD) (above 1600°C). [7] In the present Communication, we demonstrate a metal-assisted technique for the high-yield synthesis of r-BN triangular nanoplates and present a thorough analysis of their morphological and structural characteristics. The BN nanoplates with a unique triangular shape and wide bandgap will promote their successful integration into modern nanoelectronic and photonic devices.The reaction between NaNH 2 and NH 4 BF 4 in the presence of nickel sponge in a closed autoclave resulted in a white-colored product, which was identified by X-ray diffraction (XRD) as predominantly r-BN (Joint Committee on Powder Diffraction Standards (JCPDS) card 45-1171) (Fig. 1a). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images indicate that the product is composed of triangular nanoplates. The nanoplates are generally 100-300 nm wide and ca. 20 nm thick. The particle-size laser analysis indicated that the size distribution is mainly around 250 nm (see Supporting Information, SI-1d). The larger particles possibly originate from agglomeration of nanoplates in ethanol solution. According to SEM and TEM examination, the yield of triangular plates was over 90 vol %. Some truncated and broken nanoplates were occasionally observed. Figure 1b presents

How to Increase the h-BN Crystallinity of Microfilms and Self-Standing Nanosheets: A Review of the Different Strategies Using the PDCs Route

“…Two supplementary peaks can also be detected at 2θ = 42.6˝and 45.6˝and attributed to rhombohedra BN (r-BN) (JCPDS file 045-1171). Structure of r-BN is similar to that of h-BN with a stacking of alternative atomic layers ABC-ABC instead of AB-AB for h-BN [16,104]. attributed to rhombohedra BN (r-BN) (JCPDS file 045-1171).…”

“…attributed to rhombohedra BN (r-BN) (JCPDS file 045-1171). Structure of r-BN is similar to that of h-BN with a stacking of alternative atomic layers ABC-ABC instead of AB-AB for h-BN [16,104]. In order to confirm the sample microstructure, the raw powder is dispersed in ethanol under ultrasound, for a chemical exfoliation step, then observed by TEM.…”

Review Article: Challenge in determining the crystal structure of epitaxial 0001 oriented sp2-BN films

“…1). [9][10][11][12] h-BN exhibits an ABAB… stacking sequence of the basal planes while an ABCABC… stacking sequence is observed in r-BN. In h-BN, each next basal plane is rotated 180 around the c-axis ([0001]) with respect to the previous basal plane, while in r-BN, each next basal plane is shifted along the [1 100] direction by 1.45 Å .…”

“…For a powder sample of polycrystalline sp 2 -BN, determination of the crystal structure is straightforward from x-ray diffraction (XRD) in h-2h geometry, 12,[19][20][21] whereas for epitaxial sp 2 -BN films, this distinction is more difficult due to the choice of substrates resulting in predominantly 0001 oriented films. Here, we seek to point to the impossibility to apply XRD in h-2h geometry, low magnification transmission electron microscopy (TEM), Raman and Fourier transform IR spectroscopy for structure determination of epitaxial c-axis oriented sp 2 -BN films.…”

Catalyzed synthesis of rhombohedral boron nitride in sodium chloride molten salt

“…Rao [24] synthesized a mixture of h-BN and r-BN (55-84 wt%) from NaBF 4 or LiBF 4 , Li 3 N and NaN 3 . Reducible substances such as NaBH 4 or NaNH 2 were frequently used by researchers to synthesized r-BN in an autoclave [25][26][27][28][29][30]. Yuan [31] found t-BN was thermally transformed into a mixture of h-BN and r-BN in the present of Li 3 N after heating at 1000-1400°C.…”