纳米SiC纤维改性短切碳纤维增强Si_3N_4陶瓷介电响应及吸波性能

以甲基三氯硅烷为原料,采用催化化学气相沉积(CCVD)工艺在短切碳纤维(C_(fd))表面制备了纳米SiC纤维(nano SiC_f)改性层,并采用凝胶注模-无压烧结工艺制备了nano SiC_f-C_(fd)/Si_3N_4和C_(fd)/Si_3N_4复合材料。使用矢量网络分析仪研究了nano SiC_f-C_(fd)和C_(fd)对Si_3N_4陶瓷在X波段(8.2~12.4GHz)的介电响应和吸波性能的影响。结果表明:nano SiC_f-C_(fd)/Si_3N_4和C_(fd)/Si_3N_4复合材料的复介电常数和介电损耗角正切值(tanδ)均随纤维添加量增加而增大;相同纤维含量时,nano SiC_f-C_(fd)/Si_3N_4复合材料的介电常数实部比C_(fd)/Si_3N_4复合材料有所降低,但损耗角正切升高。反射损耗结果表明:nano SiC_f-C_(fd)/Si_3N_4复合材料拥有更优的电磁波吸收效果。nano SiC_f-C_(fd)含量为2wt%、d=2.5mm时,出现最大吸收峰-14.95dB,反射损耗优于-5dB,波段频宽达3.5GHz。nano SiC_f界面改性能有效提高C_(fd)/Si_3N_4复合材料的吸波性能。

Dielectric response and microwave absorbing properties for nano SiC fiber modified chopped carbon fiber reinforced Si3N4 composites

nano SiC fiber modified chopped carbon fiber (nano SiCf-Cfd )was prepred by catalytic chemical vapor deposition using Methyltrichlorosilane (MTS)as the precursor.Afterwards,nano SiCf-Cfd/Si3 N4 and Cfd/Si3 N4 composites were manufactured by two-steps process,gelcasting and atmospheric sintering.The influence of nano SiCf-Cfd and Cfd on dielectric response and microwave absorption properties within X-band(8.2-12.4 GHz)was stud-ied by using network analyzer.The results show that the complex dielectric constant and dielectric loss tangent (tanδ)of two composites increase with the added amount of fiber.At the same fiber content,the real part of the dielectric constant of nano SiCf-Cfd/Si3 N4 composite is lower than that of Cfd/Si3 N4 composites,but tanδincreases.Additionally,the results of calculated reflectivity show that nano SiCf-Cfd/Si3 N4 composites have strong microwave absorption.When the content of nano SiCf-Cfd is 2wt% and the thickness is 2.5 mm,the maximum absorption peak can reach -14.95 dB. Moreover,the bandwidth of reflectivity (less than -5 dB)is up to 3.5 GHz.Therefore,nano SiCf modification can effectively improve the microwave absorption property of Cfd/Si3 N4 composites.