Synthesis and ceramization of a soluble single-source precursor for SiZrBCN multinary ceramics with enhanced oxidation resistance
This study proposed a new zirconium-contained polyborosilazane (PSNB-Zr) precursor in steps with methyldichlorosilane (MDCS), methylvinyldichlorosilane (MVDCS), hexamethyldisilazane (HMDZ), pyridine borane and zirconocene dichloride (Cp 2 ZrCl 2 ) as raw materials. After pyrolysis of the PSNB-Zr, the corresponding silicoboron carbonitride containing zirconium (SiZrBCN) ceramics were obtained. This precursor structure was analyzed through Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS) and 1 H nuclear magnetic resonance spectrometer ( 1 H NMR). In addition, X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were carried out to analyze the ceramic microstructure and phase composition. Conversion from the precursor into the ceramic phase was investigated by TG-MS. The results suggest that the precursor has a less branched structure and is highly soluble in benzene, toluene, xylene and n-hexane. The precursor derived SiZrBCN ceramics are amorphous up to 1400 °C. When the precursor is heated to 1600 °C, SiC, Si 3 N 4 and Zr 2 CN are formed, and SiC, ZrB 2 , Si 3 N 4 , BN multiphase ceramics are obtained upon heat-treatment at 1800 °C with the phase transformation of Zr 2 CN. During the heat treatment, the ceramics change from amorphous to crystalloid with the release of small molecule like CH 4 , NH 3 , etc. The antioxidant properties of the SiZrBCN ceramics were tested at 1100-1600 °C in static air atmosphere. A compact oxidation layer is prepared on the surface of SiZrBCN ceramics, which was mainly composed of SiO 2 , ZrO 2 and ZrSiO 4 . The formation of ZrSiO 4 inhibits the evaporation of SiO 2 , thus improving the oxidation performance of SiZrBCN ceramics.
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