Thermal behaviour of a series of poly[B-(methylamino)borazine] for the preparation of boron nitride fibers

Miele

2014

Materials

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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.

Section: B-trichloro-/b-tri(methylamino)-borazine and Poly[b-tri(mmentioning

confidence: 99%

Section: B-trichloro-/b-tri(methylamino)-borazine and Poly[b-tri(mmentioning

confidence: 99%

Section: B-trichloro-/b-tri(methylamino)-borazine and Poly[b-tri(mmentioning

confidence: 99%

Section: B-trichloro-/b-tri(methylamino)-borazine and Poly[b-tri(mmentioning

confidence: 99%

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

Miele

2014

Materials

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“…no solvent is required. 50), 80) In this way, fibers with diameters ranging from a few micrometers to tens of micrometers can be obtained. The typical device (Fig.…”

Section: The Pdc Route Applied To Ceramic Fibersmentioning

confidence: 99%

Polymer-derived ceramics route toward SiCN and SiBCN fibers: from chemistry of polycarbosilazanes to the design and characterization of ceramic fibers

Viard

Miele

2016

J. Ceram. Soc. Japan

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High-temperature ceramic materials gain a continuous growing interest due to the various properties they can offer. Among all their specific features, their outstanding thermal and mechanical stability attract much attention to save energy. In the category of ceramics, silicon-based non-oxide compositions display a great potential for many applications involving high temperatures, high stresses or harsh environments. Since the major binary silicon carbide and silicon nitride, which are currently used as highperformance ceramics, were discovered, the role of chemistry in the design of materials has become major. Its potential lies in the exploitation of new chemical systems and the development of new preparative routes. As a consequence, new ceramic properties can be envisioned. The polymer derived ceramic (PDC) route is a "ceramic through chemistry" concept which allows synthesizing new materials in terms of compositions and shapes difficult to tailor using more conventional approaches. This review highlights the works made in the last decades concerning the preparation of PDC fibers with a particular focus on amorphous SiCN and SiBCN networks using melt-spinning and electrospinning processes of preceramic polymers. One main emphasis of this review is set on addressing the intimate relationship between molecular structure/architecture of preceramic polymers, their spinning/ curing/pyrolysis behavior and the properties of the final fibers.

Evaluation of the processability of boron‐containing organosilazane polymers based on shear rheology

Ouyang

Gottardo

J of Applied Polymer Sci

et al. 2012

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The shear rheology of boron-containing organosilazane polymers has been investigated in detail with a double objective. The first objective was to evaluate their processability to form fibers by melt-spinning, and the second objective was to predict their molecular structure. We focused on a representative type of boron-containing organosilazane polymers called boron-modified polysilazanes (BmPSs) with the ideal structure [B(C 2 H 4 SiCH 3 NCH 3 ) 3 ] n (C 2 H 4 ¼ CHCH 3 , CH 2 CH 2 ). Characterization tools showed that their viscous and elastic properties are strongly affected by molecular parameters fixed during synthesis and in particular by the methylamine (MA) : tris(dichlorosilylethyl)borane (TDSB) molar ratio imposed during their synthesis. In the spinning domain, the frequency dependences of the storage and loss moduli showed that the prerequisite conditions for obtaining polymer fibers are fulfilled with samples having 9.0 MA : TDSB molar ratios 9.7. However, the presence of thickening in the computed extensional viscosity function and the loss of cohesion of filament derived from samples with MA : TDSB ratio > 9.2 during drawing put in evidence the best potential of polymers with 9 MA : TDSB ratio 9.2 to generate fine-diameter solid filaments in a stable process. Based on rheological tests, the molecular structure of BmPSs has been tentatively predicted in relation with the MA : TDSB ratio. The increase of the latter favored the disentanglement of the polymer framework, and we postulated that it lowered the molecular weight.