Polymer-derived SiC fibers are critical structural and functional materials for high-temperature applications, whose service performance can be further improved by introduction of certain heterogeneous elements. Herein, flexible and thermal stable SiC fiber mats were prepared from boron-doped polyaluminocarbosilane (PACS) precursor by electro-spinning, curing and pyrolysis. Two boron-containing compounds o-carborane (oCB) and phenylboronic acid (PBA) were used as the boron sources and their effects on the properties and structure of the SiC fiber mats were investigated. The introduced oCB and PBA had obviously improved the ceramic yield of the cured fiber mats and the flexibility of the SiC fiber mats. However, PBA introduced more boron, but also more oxygen, which leaded to formation of more amorphous SiC x O y phases. Although only a small amount of boron was introduced by oCB, a more significant improvement in the thermal stability of the SiC fiber mat was obtained. This work provided a practical approach for fabrication of flexible and thermally stable SiC fiber mats.
Oxygen/nitrogen (O 2 /N 2 ) separation is of great importance but faces huge challenges owing to their similar molecular size and close polarity. In this work, we construct a polymer of intrinsic microporosity (PIM-1) based mixed matrix membrane (MMM) for efficient O 2 /N 2 separation by using ZIF-8 as the sieving filler along with surface modification of o-carborane (o-CB) to strengthen selective N 2 adsorption fixation as well as polymer-filler interfaces. Markedly, the o-CB on the outer surface of ZIF-8 not only affords the requisite interfacial compatibility in molecular sieving MMMs, but also increases the diffusion difference between O 2 and N 2 by the preferential adsorption with N 2 molecules. This synergistic effect of molecular sieving and adsorption inhibition achieves efficient O 2 /N 2 diffusion differential separation. As expected, the optimal membrane with o-CB-ZIF-8 loading of 35 wt% exhibits an O 2 permeability of 796.5 Barrer and a mixed O 2 /N 2 selectivity of 8.9 with O 2 /N 2 (20:80, vol.) mixtures, exceeding the latest 2015 upper bound limits. Moreover, the according membrane module with o-CB-ZIF-8 loading of 20 wt% also displays moderate O 2 permeability of 391.7 Barrer and O 2 /N 2 selectivity of 5.5 under pressure of 1 bar. This work may provide a feasible platform for designing high-performance MOF-based membranes in air separations.
危险品化学品经营许可证（带存储）