Preparation And Properties Studies Of Silicon Carbide Fibers With Multi-shaped Cross Filament Inerratic Arrangement

The profiled silicon carbide (SiC) fibers which have good radar wave absorbing ability in X-band had been fabricated from the polycarbosilane (PCS) by the process of melt spinning, curing and pyrolysis. In the paper, with the direction of impedance matching rule, two kinds of spinnerets with multi-shaped orifices were designed, namely, O-Y and O-C-Y spinnerets, the fibers fabricated with them were named O-Y and O-C-Y fibers. O-Y and O-C-Y PCS fibers' preparation techniques were studied respectively, moreover, the curing techniques for them were investigated by means of FT-IR. The electromagnetic parameters of O-Y fibers were also measured; what more, the electromagnetic performance of O-Y SiC fibers and intermixed SiC fibers with the same shapes and ratios of different fibers were compared.The results showed that when the flux ratio of different orifices is 3 around, the spinning process is stable.There is a gradual decrease in effective filament diameters (ED) of different cross section fibers with the rise of taking-up rate or the decrease of pump flux. There is a rise in the degree of profile (DP) of trilobal PCS fibers with the decrease of take-up rate or pump flux, In the same condition, The degree of profile (DP) of C-shaped fiber is almost unchanged. When the pump flux is 14~20ml/min or the taking-up rate is 400~600m/min, the O-Y PCS fibers with high DP and small ED can be fabricated. When the pump flux is 15~22ml/min or the taking-up rate is 400~500m/min, the O-C-Y PCS fibers with high Dp and small comparatively Ed can also be obtained.In appropriate spinning condition, for O-Y SiC fibers, the curing effective diameter (CED) of trilobal SiC filament can be consistent with the diameter of circular SiC filament, for this reason, the curing reaction degree is almost uniform. For O-C-Y SiC fibers, the curing reaction degree of circular and C-shaped SiC fibers is almost uniform, while the curing reaction degree of trilobal filament is a little higher than them.For O-Y SiC fibers, when the diameters of circular and trilobal filament are 10~11.5μm and 16~19um respectively, the tensile strengthes are all 1.8~2.2GPa, moreover, the strength distribution of trilobal SiC filament is narrow. For O-C-Y SiC fibers, C-shaped filament has a narrowest strength distribution; the strength distribution of the trilobal filament is narrower than the circular filament. The average tensile strength of circular and C-shaped fibers is about 1.6GPa, the average tensile strength of trilobal filament is around 1.8GPa.In X band, for O-Y SiC fibers, the dielectric loss (tan8) lies in 0.3~1.3, there is gradualfall for e\ s", electromagnetic parameter's change can be induced by the change of degree of profile, It is showed that the loss can be highest when the degree of profile is 0.9 around, The wave absorbing ability of the O-Y SiC fibers is better than pure trilobal fibers and intermixed fibers with the same shapes and ratios of different fibers.