Advanced fibers enable the fabrication of structures and composites for applications reliant on lightweight, oxidation resistant, mechanically strong, and electrically insulating materials, e.g. in all forms of land, air, and space transportation and in applications within extreme environments. Hexagonal boron nitride (h-BN) fibers harness these advantages, and in addition, offer ultra-high-strength-to-weight ratio and low density. Yet, existing precursors for polymer-derived BN fibers are limited to insoluble and air/moisture sensitive polyborazylenes, hindering fiber production at scale. In this contribution, we report a reliable, controllable, and scalable synthesis methodology for producing pure micro- and nano-h-BN fibers, offering a competitive alternative to NASA’s energy-intensive h-BN nanotubes production. The single-source precursor, N-methyl polyaminoborane (PMeAB), plays a pivotal role in this process. The catalytic, and scalable, synthesis of PMeAB with controlled molecular weights (Mw = 110,500–290,500 g·mol−1) enables the production of h-BN fibers by electrospinning method and thermolysis under ammonia. PMeAB molecular weight and concentration were identified as key factors dictating the viscosity and surface tension, and thus influencing the overall spinnability of the PMeAB solution. We reveal that the subsequent formation of a cross-linked intermediate during PMeAB thermolysis is essential to retain the fibrous morphology during the conversion to h-BN fibers. Comprehensive characterization demonstrated the purity and homogeneity of the h-BN fibers, with ~ 97 at.% of B and N contents combined throughout the fiber body. This newly disclosed route to h-BN fibers offers a route to potentially valuable multifunctional filler material for advanced lightweight composites suitable for applications in extreme environments.

The perfluoropinacol borate-based anion [B(O2C2(CF3)4)2]−, [FPB]–, is developed as a weakly coordinating anion for single-crystal to single-crystal organometallic solid/gas reactivity, resulting in the isolation and characterization (including periodic DFT and IGMH analysis) of the σ-alkane complex [Rh(Cy2PCH2CH2PCy2)(exo-η2η2-norbornane)][FPB]. The synthetically useful solvent-free Na+ salt, Na[FPB], and oxonium acid [H(OEt2)2][FPB] are also reported.

In Atlanta and Washington DC Grayson explores race and 'White privilege'

Man who says he had previously left and re-entered the country multiple times alleges border officials called him ‘retarded’ and boasted ‘Trump is back in town’

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Project opportunity - Digital and Flow Materials Chemistry for Metal-Organic Frameworks Production at the University of Leeds