Silicon nitride, as a high-performance non-oxide ceramic material, occupies an important position in high-end manufacturing due to its excellent high-temperature resistance, high hardness, corrosion resistance, and good mechanical properties. Its slurry form is widely used in the preparation of key products such as engine core components, electronic packaging substrates, and precision cutting tools, becoming one of the core materials driving the upgrading of high-end equipment.
In practical production applications, the dispersion stability of silicon nitride slurry directly determines the performance and quality of the end product. However, the surface of silicon nitride particles contains complex chemical groups, mainly including Si-OH and Si-NH₂. The presence of these groups leads to uneven charge distribution on the particle surface. In water-based or organic solvent systems, the zeta potential fluctuates easily, making it impossible to form a stable electrostatic equilibrium, thus causing particle flocculation and sedimentation. This dispersion problem not only leads to poor slurry fluidity but also causes defects such as porosity, cracks, and uneven thickness in the product during subsequent molding and sintering processes, seriously affecting the density and mechanical properties of the product and restricting the industrial application of silicon nitride materials.
Regarding particle surface charge optimization, an ultrasonic-assisted control strategy is employed to adjust the slurry pH to the 9-10 range, moving the silicon nitride particles away from their isoelectric point. Simultaneously, the adsorption effect of dispersants (such as ammonium polyacrylate PAA-NH₄) effectively adjusts the particle surface charge distribution. The cavitation effect of ultrasound promotes the uniform adsorption of dispersants on the particle surface, enhances the electrostatic repulsion between particles, and significantly improves slurry stability. Testing shows that the optimized slurry, after standing for 24 hours, can maintain a stratification rate below 5%, effectively preventing particle flocculation and sedimentation.
Regarding agglomerate refinement, for submicron-sized (D50 < 1 μm) silicon nitride agglomerates, the high-frequency shear force generated by ultrasound can forcibly peel away the adhesion between particles, breaking the agglomerate structure and allowing the particles to be uniformly dispersed in the system. This process not only significantly improves the fluidity of the slurry, reducing its viscosity to below 500 mPa·s, but also enhances the thickness uniformity of the cast substrate, laying a solid foundation for subsequent sintering processes. After optimization, the density of the sintered silicon nitride product can approach the theoretical value (>98%), with significantly improved mechanical properties and operational stability.
With the continuous upgrading of high-end manufacturing industries, higher requirements are being placed on the dispersion precision and stability of silicon nitride slurries. The application of ultrasonic dispersion technology has effectively solved the dispersion problem of silicon nitride slurries, promoting its widespread application in fields such as engine bearings, sealing rings, and electronic packaging substrates. It provides crucial technical support for the industrialization of high-performance silicon nitride products, contributing to the high-quality upgrading of high-end manufacturing industries.
