Synthesis and characterization of soluble and meltable Zr-containing polymers as the single-source precursor for Zr(C, N) multinary ceramics

Soluble and meltable Zr-containing preceramic polymers were synthesized in this work by the polymerization of ZrCl4 and different diamines, followed by preparation of Zr(C, N) multinary ceramics via pyrolysis. The composition, structure and morphology were investigated by Fourier transform infrared spectroscopy, nuclear magnetic resonance, as well as thermogravimetric-mass spectrometry, X-ray diffraction, elemental analysis, scanning electron microscopy (SEM) and transmission electron microscopy. Results showed that although the precursor could be formed by the reaction between Zr–Cl and N–H bonds, the ceramic yield was low due to the release of NH3 and CH4 gases during the ceramization process. To improve the ceramic yield, allyl amine was applied to tailor the polymer structure. With allyl groups acting as the “bridge” during crosslinking process, the precursor had a higher ceramic yield of 62.5% and melting point of 280–300 °C with Zr content of 49.7 wt% in the derived Zr(C, N) ceramics. Annealing experiments in an inert atmosphere at temperatures in the range of 1200–1400 °C showed the transformation of the amorphous state to dense polycrystalline ceramics. When temperature was increased to 2000 °C, the ceramics got quite dense without obvious phase separation. The precursors could be applied as promising candidates for non-oxide ceramic matrix composites and fibers at ultra-high temperatures and even in harsh environments.