Electron microscopy study of ZrB₂–SiC–AlN composites: Hot-pressing vs. pressureless sintering

The impact of AlN addition on the microstructure and sinterability of ZrB₂-SiC composites was studied. The pressureless sintering and hot-pressing techniques were used as manufacturing methods. The composites produced by hot-pressing method were sintered at 1900 °C, producing fully dense products with 1 and 5 wt% AlN. X-ray diffraction (XRD), and electron microscopy (FESEM and HRTEM) instruments were implemented to characterize the produced composites. The XRD analysis clarified the in-situ formation of graphitized carbon during the sintering. However, no Al-based compounds could be identified in the patterns. Moreover, liquid phase formation was confirmed as one of the sintering mechanisms for the all samples, creating clean interfaces in the composites produced by hot-pressing.