Research Of Silicon Zirconium Oxycarbide And Silicon Boron Oxycarbide Ultrafine Fibers

Fiber reinforced aerogels possess high mechanical property and excellent high temperature thermal insulating performance.It is of importance for the development of aerospace technology and military field.Therefore,the following two parts are the researches of ceramic ultrafine fiber this thesis mainly focused on.?A?The ultrafine PZSO fiber was electrospun using VTMS as a silicon source,Zr?OC₄H₉?₄ as zirconium source,PVP as the polymer for the fibers formation,EtOH as solution HNO₃ as a catalyst,HAc as a complexing agent,separately.After high temperature pyrolysis,the SiZrOC ultrafine fiber was obtained.Combining the low thermal conductance of ZrO₂ with anti-infrared heat radiation property of SiC fibers at high temperature,the SiZrOC ultrafine fiber was prepared.The ultrafine fiber shows better insulating performance than general fiber.With addition of 12.00-20.00 wt%HAc in electrospinning solution,the obtained PZSO fibers show high length-diameter ratio,well-distributed diameter and good fiber morphology.The best electrospinning processing conditions are as following:voltage is10-15 kV,distance between tip and collecter is 20-30 cm,federate is 0.9 mL·h^-1.The SiOC phase in the SiZrOC fiber displays amorphous structure,and the t-ZrO₂phase is crystal.The diameter of SiZrOC fiber is about 600-900 nm,the suface of SiZrOC fiber is smooth and dense,without pores and crack.The SiZrOC ultrafine fiber shows good high temperature stability,thermal insulating performance and flexibility.The residue weight at 1200°C was 97.5 wt%for SiZrOC fiber and 90.9 wt%for corresponding SiOC fiber.The thermal conductivity of SiZrOC fiber is as low as0.03749 W·m^-1·K^-1.?B?The ultrafine PBSO fiber was electrospun using TEOS and VTMS as a silicon source,H₃BO₃ as boron source,PVP as the polymer for the fibers formation,EtOH as solution and HNO₃ as a catalyst,separately.After high temperature pyrolysis,the SiBOC ultrafine fiber was obtained.Well distributed Boron atoms were incorporated into the SiO₄ units via Si-O-B bonds.The obtained SiBOC fiber was composed of SiO₄,SiCO₃,BO₂C,B?OSi?₃ and free carbon.The diameter of SiBOC fiber is about 1.2±0.2?m,the suface of SiBOC fiber is smooth and dense,without pore and crack.The SiBOC ultrafine fiber show good high temperature stability,oxidation resistance,erosion resistance and flexibility.The residue weight at 1200°C was 89.2wt%for SiBOC fiber and 81.5 wt%for corresponding SiOC fiber.After to 800°C in air with a holding time of 1 h,the surface of treated SiBOC fibers had no obvious change.After immersing Si?B?OC fiber mats in 2 M NaOH and 1 M H₂SO₄ solutions for 24 h,SiBOC fibers were not damaged in both solutions.