Polymer-Derived Boron Nitride: A Review on the Chemistry, Shaping and Ceramic Conversion of Borazine Derivatives

Abstract

Boron nitride (BN) is a III-V compound which is the focus of important research since its discovery in the early 19th century. BN is electronic to carbon and thus, in the same way that carbon exists as graphite, BN exists in the hexagonal phase. The latter offers an unusual combination of properties that cannot be found in any other ceramics. However, these properties closely depend on the synthesis processes. This review states the recent developments in the preparation of BN through the chemistry, shaping and ceramic conversion of borazine derivatives. This concept denoted as Polymer-Derived Ceramics (PDCs) route allows tailoring the chemistry of precursors to elaborate complex BN shapes which cannot be obtained by conventional process. The effect of the chemistry of the molecular precursors, i.e., borazine and trichloroborazine, and their polymeric derivatives i.e., polyborazylene and poly[tri(methylamino)borazine], in which the specific functional groups and structural motifs determine the shaping potential by conventional liquid-phase process and plastic-forming techniques is discussed. Nanotubes, nano-fibers, coatings, monoliths and fiber-reinforced matrix composites are especially described. This leads to materials which are of significant engineering interest.

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

“…In that way, as already mentioned in the introduction, the used of PBN as preceramic precursor is particularly relevant [30,50,51,84] since it is prepared through pure borazine that initially displays the expected targeted hexagonal arrangement [85]. Moreover, since the polymer is obtained without any solvent addition, only hydrogen is expected to be lost [25,[86][87][88] and no contaminant is present, whose presence may slow down the crystallization process. Some studies report the addition of calcium carbonate [1,16,77,89] or lithium nitride to increase the final h-BN crystallization.…”

“…The main interest in this additivation is to drastically decrease the crystallization temperature from traditionally, at least 1500 °C [25], to 1000-1200 °C. To our knowledge, we are the first to demonstrate the additive activity of Li3N when adding in a preceramic polymer and the heat treatment of that mixture.…”

Robust 3D Boron Nitride Nanoscaffolds for Remarkable Hydrogen Storage Capacity from Ammonia Borane

“…PB was synthesized at 60 8Cf rom homemade borazinea ccording to ap reviously published procedure. [47,58] It has the nominal structure [B 3.0 N 3.5 H 4.5 O 0.04 ] n .T he presence of NH and BH groups in its structure resultsi naprecursorw ith improvedt hermal cure characteristics,a sw ell as an enhanced ceramic yield. PB exhibits am ulti-step decomposition up to 1450 8Cu nder nitrogen starting from 110 8C, providing BN with aw eight loss of 4.8 %; this corresponds to ac eramic yield of 95.2 wt %( see Figure 1i nt he Supporting Information).…”

“…[45][46][47][48][49][50][51][52][53][54][55][56][57] In particular, we demonstrate the possibility to control the physical state of polyborazylene from the liquid to solid state via control of the temperature of self-condensation in the temperature range4 5-60 8C. [45][46][47] Thep olyborazylene prepared at 60 8Ci sh ighly soluble in polar tetrahydrofuran (THF) and non-polar (toluene) solvents and displays asignificant, high ceramic yield. It is thus used in the present work as ap recursor for mesoporous BN monoliths through ah ighyield methodology that enables the practical development and application of these mesoporous BN monoliths,p articularly as ananoscaffold of AB.…”

A Novel Polymeric Precursor for Boron Nitride Ceramics: Synthesis, Characterization, and Ceramic Conversion

“…By thermal pyrolyzing polymeric precursors to produce ceramics, the PDC technique possesses distinct advantages over the traditional routes in manufacturing ceramic fibers, coatings, nanostructures, and composites . To fabricate BN ceramics with versatile shapes using the PDC route, however, a crucial prerequisite is that a suitable BN polymeric precursor with desirable processability must be developed in advance …”