Due to corrosion and oxidation resistance properties, SiOC ceramics have found wide application in environment and energy.Compared with SiOC, Boron-doped SiOC glasses (SiBOC) exhibit superior thermal and mechanical properties.[1] It is meaningful to develop uniform and flexible SiBOC ultrafine fiber mat to satisfy the demands in catalyst materials.To achieve this goal, sponge-like SiBOC ultrafine fiber mat was prepared via sol-gel electrospinning.The main research results are as follows:Spinning solution was synthesized by reacting silicon alkoxides: tetraethoxide (TEOS) and methyltriethoxysilane (MTES) in ethanol-water with H3BO3 using HNO3 as a catalyst, PEO as the polymer for the fibers formation, separately.The solution was electrospun to form the green fiber.Subsequent pyrolysis in argon, SiBOC ceramic fibers were prepared.The investigation on how the solution rheology and the amount of silicon alkoxides influence the fiber morphology are under-taken and reveals how defect-free fibers in the diameter of 1~5 μm are obtained.Both the green fibers and the ceramic fibers were investigated by Fourier-transformed infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscope (SEM).The FT-IR of the PBSO and SiBOC fiber shows the formation of Si-O-B bond (Fig.1a).The SiBOC ultrafine fibers are approximately 2.5 μm in diameter (Fig.1c), without any noticeable flaws in the surface.Both the PBSO and SiBOC fiber mat are sponge-like, and the SiBOC fiber mat would recover after loading.