Study On Synthesis And Pyrolysis Of New Zr-Based （ZrC And ZrB₂） Ceramic Precursor And Precursor Fibers

With the characteristics of good polymer manufacturability, programmable molecular structure, low ceramic tempreture and molecular level of uniform dispersion, the precursor can be spun, molded and used for the preparation of ceramic matrix composites. In this thesis, synthesis and pyrolysis of new Zr-based(Zr C and Zr B2) ceramic precursor and precursor fibers were studied.(1) The zirconium oxychloride, salicylic alcohol and triethylamine was used as raw materials to prepare the ceramic precursor of Zr C. The effect of different molar ratio of zirconium oxychloride to trimethylamine(1:2、1:1.86、1:1.84、1:1.82、1:1.8、1:1.78、1:1.74) and different molar ratio of zirconium oxychloride to salicylic alcohol(1:0.5、1:1、1:1.5、1:2、1:2.5、1:3、1:3.5) on the precursor was studied. The solubility of the precursors in methanol and acetone solvents was discussed. The crosslinking and pyrolysis process of precursor at 1000°C to 1400°C was explored by using TG-DSC and tubular furnace. The pyrplysis products were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM), Raman spectrum, transmission electron microscopy(TEM) and EDS. The results show that pyralysis products contain Zr C crystal, which present the multitude of irregular polyhedron structure and the average size of grain is around 100 nm.(2) The ceramic precursor of Zr C and boric were used as raw materials to prepared ceramic precursor of Zr B2, during which the effect of different molar ratio of Zr to B(1:2.5、1:3、1:3.5、1:4、1:4.5) was explored. The solubility of the precursor in ethanol and tetrahydrofuran was studied. The crosslinking and pyrolysis process of precursor at 1000°C to 1400°C was explored by using TG-DSC and tubular furnace. The pyrplysis products were investigated by XRD, SEM and Raman spectrum. The resules show that the pyrolysis temperature has a significant effect on the composition, structure and phase of the products, the pyralysis products mainly contain Zr B2 crystal, which present the spherical or rod structure and the average size of grain is around 150 nm.(3) With the poly zirconium acetylacetonate(PZO), salicyl alcohol and polyvinylpyrrolidone(PVP) as raw materials, the Zr C precursor fibers were prepared by electrospinning. The conditions of electrospinning were discussed. The pyrolysis process of precursor fibers was studied at 1000°C to 1400°C by using TG-DSC and tubular furnace. The precursor fibers and pyrplysis precursor fibers were investigated by XRD, SEM, Raman and TEM. The results show that the pyrolysis products keep the structure of fibers, the surface is smooth and the diameter distribution is uniform at 1400 °C.(4) With the PZO, salicyl alcohol and PVP as raw materials, the Zr B2 precursor fibers were prepared by electrospinning. The conditions of spinning were studied. The pyrolysis process of precursor fibers was studied at 1000°C to 1400°C by using TG-DSC and tubular furnace. The precursor fibers and pyrplysis precursor fibers were investigated by XRD, SEM, Raman spectrum, TEM/HRTEM and BET. The results show that the pyrolysis products keep the structure of fibers and the surface is smooth.