Synthesis and pyrolysis behavior of a soluble polymer precursor for ultra-fine zirconium carbide powders

Abstract

A soluble polymer precursor for ultra-fine zirconium carbide (ZrC) was successfully synthesized using phenol and zirconium tetrachloride as carbon and zirconium sources, respectively. The pyrolysis behavior and structural evolution of the precursor were studied by Fourier transform infrared spectra (FTIR), differential scanning calorimetry, and thermal gravimetric analysis (DSC–TG). The microstructure and composition of the pyrolysis products were characterized by X-ray diffraction (XRD), laser Raman spectroscopy, scanning electron microscope (SEM) and element analysis. The results indicate that the obtained precursor for the ultra-fine ZrC could be a Zr–O–C chain polymer with phenol and acetylacetone as ligands. The pyrolysis products of the precursor mainly consist of intimately mixed amorphous carbon and tetragonal ZrO2 (t-ZrO2) in the temperature range of 300–1200°C. When the pyrolysis temperature rises up to 1300°C, the precursor starts to transform gradually into ZrC, accompanied by the formation of monoclinic ZrO2 (m-ZrO2). The carbothermal reduction reaction between ZrO2 and carbon has been substantially completed at a relatively low temperature (1500°C). The obtained ultra-fine ZrC powders exhibit as well-distributed near-spherical grains with sizes ranging from 50 to 100nm. The amount of oxygen in the ZrC powders could be further reduced by increasing the pyrolysis temperature from 1500 to 1600°C but unfortunately the obvious agglomeration of the ZrC grains will be induced.