户外睡袋用面料防水透湿性能的评价

户外睡袋用面料对防水性能和透湿性能的要求很高。文章针对市场上已有的高密面料、涂层面料和覆膜面料3类共20种户外睡袋面料进行调研,并对面料的表面抗湿性能、抗渗水性能和透湿性能进行评价。结果表明:覆膜面料和高密压光面料的表面抗湿性最好,沾水度评级在4~5级;覆膜面料的抗渗水性最好,静水压值大于等于30 kPa,其中PU覆膜面料和PTFE两层覆膜面料静水压值大于50 kPa;高密面料的透湿性能最好,透湿量最高超过6000 g/(m^2·d),PTFE覆膜面料的透湿性能也较好,透湿量接近4000 g/(m^2·d)。

Effects of dip-coated BN interphase on mechanical properties of SiC_f/SiC composites prepared by CVI process

BN interphase was successfully synthesized on SiC fiber fabrics by dip-coating process using boric acid and urea as precursors under N2 atmosphere. The morphology of BN interphase was observed by SEM, and the structure was characterized by XRD and FT-IR spectra. The SiCf/SiC composites with dip-coated BN interphase were fabricated by chemical vapor infiltration （CVI） process, and the effects ofBN interphase on the mechanical properties of composites were investigated. The results show that the SiC fibers are fully covered by BN interphase with smooth surface and turbostratic structure （t-BN）, and the thickness is about 0.4 μm. The flexural strengths of SiCf/SiC composites with and without BN interphase are about 180 and 95 MPa, respectively. Compared with the as-received SiCf/SiC composites, the composites with BN interphase exhibit an obvious toughened fracture behavior. From the microstructural analysis, it can be confirmed that the BN interphase plays a key part in protecting the fibers from chemical attack during matrix infiltration and weakening interfacial bonding, which can improve the mechanical properties of SiCf/SiC composites remarkably.