A mechanistic study on the synthesis of β-Sialon whiskers from coal fly ash

• β-Sialon whiskers were synthesized using waste fly ash by carbothemal reduction reaction under nitrogen atmosphere.
• Rod-like β-Sialon whiskers with a diameter of 100–500 nm were formed.
• Bead-like whiskers as intermediate morphology of the growing β-Sialon whiskers were found with increasing sintering time.
• The growth mechanism of β-Sialon whiskers was different from the conventional VLS mechanism.
• A chain of droplets were formed and participated in the formation of the whiskers.

β-Sialon whiskers were produced at 1420 °C through carbothemal reduction reaction under nitrogen atmosphere using fly ash from coal-fired power plants. The effects of sintering time on the phase formation and morphology of the products were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) techniques. Rod-like β-Sialon whiskers with the diameter of 100–500 nm were successfully formed. With increasing sintering time, bead-like morphology during the growth process of the whiskers was found, and growth mechanism of β-Sialon whiskers was also discussed in detail. The growth mechanism proposed in this study was different from the conventional vapor–liquid–solid (VLS) mechanism.

The appearance of bead-like whiskers indicated that the growth mechanism of the β-Sialon whiskers was different from the conventional one, in which a chain of droplets were formed and then consumed to participate in the formation of the whiskers.Figure optionsDownload as PowerPoint slide