What question did this study set out to answer?

This research aims to synthesize Si3N4@MgSiN2 composite powders with a core-shell structure and investigate the influencing factors on their properties.

April 10, 2026Open Access

Controllable Preparation of Si3N4@MgSiN2 Core–Shell Powders via a “Template Growth” Mechanism in NaCl-KCl Mixed Molten Salt

Key Points

This research aims to synthesize Si3N4@MgSiN2 composite powders with a core-shell structure and investigate the influencing factors on their properties.
Synthesis of Si3N4@MgSiN2 via in situ reaction between Mg and α-Si3N4
Use of NaCl-KCl mixed molten salt for the reaction
Testing variations in process parameters like reaction temperature and Mg/Si3N4 mass ratio
Observation of morphology and phase composition of the resulting powders
Si3N4@MgSiN2 powders exhibit a core-shell structure with a uniform MgSiN2 layer
Reaction temperature set at 1300 °C leads to effective layer formation
Yield of MgSiN2 layer shows a linear correlation with Mg/Si3N4 mass ratio
Low-temperature liquid phase formation around 1350 °C indicates high sintering activity

Abstract

Si3N4@MgSiN2 composite powder with a core–shell structure was successfully synthesized via the in situ reaction between Mg and α-Si3N4 using a NaCl–KCl mixed molten salt in this study. The effects of process parameters, including the molten salt system, reaction temperature, and Mg/Si3N4 mass ratio, on the morphology, phase composition, and microstructure of the coating layer were investigated. The results indicate that the reaction follows a “template growth” mechanism. Mg-containing species dissolve in the molten salt, diffuse to the surface of Si3N4 particles, and react with α-Si3N4, resulting in a relatively uniform MgSiN2 layer at 1300 °C. The yield of MgSiN2 layer exhibits a linear positive correlation with the Mg/Si3N4 mass ratio, enabling controllable microstructural regulation through adjustment of the starting materials composition. The core–shell powder forms a liquid phase at a relatively low temperature (approximately 1350 °C), demonstrating excellent sintering activity. This work provides a new material foundation for the fabrication of silicon nitride ceramics with high thermal conductivity.

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