Abstract
Hexagonal boron nitride (h-BN) is nowadays an increasingly attractive material, especially for two-dimensional material applications, due to its intrisic properties. However, its properties are highly dependent on the used synthesis approach. The polymer derived ceramics (PDCs) route allows elaboration of h-BN with tailored textural and structural properties. Here, we demonstrate the interest of the PDCs pathway for the synthesis of h-BN. Growth of h-BN single crystals with crystal sizes of a few microns at relatively low temperature and atmospheric pressure is successfully achieved from borazine precursor using PDCs. The crystallization is improved by additivation of 5 wt% of Li3N to the pre-ceramic polymer. Furthermore, by coupling PDCs with gas pressure sintering, starting from the same pre-ceramic polymer and 25 wt% of Li3N, the crystal size is enlarged up to hundreds of microns. The fabricated single crystals of pure h-BN can then be exfoliated into h-BN nanosheets. Finally, by combining PDCs with atomic layer deposition, functional BN nano-/hetero-structures are successfully synthesized from highly structured sensitive templates, making this ALD process a promising alternative for fabricating functional BN nanostructures.
Highlights
1.1 Hexagonal Boron Nitride (h-BN)Until its discovery as natural state in 2014,(1) boron nitride (BN) has only been known as a synthetic ceramic
The Poymer Derived Ceramics (PDCs) route has been used for the synthesis of different kinds of boron nitride materials, from bulk to nanostructures.[28,29,30,31] Recently, it has demonstrated a high potential for the fabrication of bulk h-BN crystals that can be further exfoliated into Boron Nitride NanoSheets (BNNSs).[32,33,34,35,36]
These characteristics are close to the ones previously observed for synthesis of h-BN combining Polymer Derived Ceramics (PDCs) route with spark plasma sintering process.[34]. In that case, we can assume that the growth occurs in the liquid phase and the proposed crystallization mechanism would be similar to one of the previous studies reported by Bezrukov [48] and other groups.[47,49,50] At around 600–700 °C, Li3BN2 formed by reaction between Li3N and preceramic BN, melts and infiltrates amorphous BN and dissolves it, leading to highly crystallized hexagonal boron nitride
Summary
Until its discovery as natural state in 2014,(1) boron nitride (BN) has only been known as a synthetic ceramic. Our lab works on synthesis of h-BN by the PDCs route giving rise to different shapes (fibers, coatings, foams, nanocages...).(38–43) More recently, our research efforts have been focused on the improvement of the PDCs route for h-BN nanomaterials fabrication. In this contribution, we will present results obtained with PDCs alone, PDCs combined with Gas Pressure Sintering (GPS) and with Atomic Layer Deposition (ALD)
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