Research On Preparing Ultrafine ZrO₂/SiC Fibers By Electrospinning

The ultrafine ZrO₂/SiC complex fibers and the ultrafine ZrO₂/SiC radial gradient fibers are prepared, which combine the low thermal conductance of ZrO₂ with interferering the infrared heat radiation ability of SiC fibers. It's significant to the research on heat insulation meterials at high temperature such as silica aero-gel. Polycarbosilane (PCS) blended with zirconium butoxide (Zr(OC₄H₉)₄) were dissolved in the organic solvent together and the related PCSZ green fibers were obtained by electrospinning. After air curing and high temperature pyrolysis, the ultrafine ZrO₂/SiC fibers containing zirconium were finally achieved. Besides, the ultrafine ZrO₂/SiC radial gradient fibers could be prepared by adding a maturing process before curing.The results show that PCS and Zr(OC₄H₉)₄ in the solution are mixed physically, and have good solubility. The concentration of Zr(OC₄H₉)₄ could be changed from 0 to 50wt%. PCS is the major materisl in electrospinning. As increasing the content of Zr(OC₄H₉)₄, the concentration range of the PCSZ solution decreases. The electrospinning process on the PCSZ solution are the Zr(OC₄H₉)₄ concentration around 20⁴0wt%, the PCS concentration around 1.10¹.40g/ml, feed rate from 20 to 40μl/min, the voltage from 12 to 20kV and the collect distance from 15 to 20cm.The radial gradient can be made by the pervasion of Zr(OC₄H₉)₄ molecule through maturing process. The adding of Zr(OC₄H₉)₄ has an effect on baffling the oxidation of the PCSZ fibers. It was found that the PCSZ fibers should have a moderate heating rate, which was shorter than the heating rate of commonly PCS fibers but longer than PCS fibers that made by electrospinning. The maturing process is the temperature from 80 to 120℃and the maturing time from 80 to 120 hours. The curing process is that heat from room temperature to 150℃by 1 to 1.5℃/min heating rate, after holding 1 to 2 hours at 150℃, then heat to210 to 220℃by 1 to 3℃/min heating rate.The ZrO₂/SiC fibers felt were finally generated with the diameter of 1⁷μm with average of 5μm, and the smallest diameter can reach 0.5μm. ZrO₂ and SiC crystals were well formed. SEM, XRD,TEM and XPS were used to characterize the configuration, composing and structure. EDS and AES spectrum showed that the content of zirconium decreased from the surface to the inside of the ZrO₂/SiC fibers felt. It proved that radial gradient structure may exist in the ZrO₂/SiC fibers felt.The high temperature and alkali resistance of fibers were studied in this paper. It was found that the ZrO₂/SiC fibers have a much better high temperature resistance than SiC fibers in argon; ultrafine ZrO₂/SiC fibers with radial gradient have a much better eroding resistance than the ones without radial gradient.