Enhanced Aqueous Tape Casting Slurries via Coating and Modification for Silicon Nitride Ceramic Substrates

This study addresses key challenges in aqueous tape casting of Si 3 N 4 ceramic substrates, including poor slurry dispersibility, limited solid loading, high viscosity, and the risk of additional oxygen introduction during surface modification. A dual‐modification strategy combining urea precipitation coating and APTES surface amination was developed to functionalize Si 3 N 4 powders. These modified powders were incorporated with Isobam‐104 binder to formulate water‐based slurries. The optimized slurry exhibited exceptional colloidal stability and achieved a solid loading of 46 vol% with a practical viscosity of 0.18 Pa·s at 40 s −1 shear rate, enabling fabrication of green tapes with homogeneous microstructures. Pressure‐assisted sintering yielded dense Si 3 N 4 substrates demonstrating > 99% relative density, 726 MPa flexural strength, and 65 W·m −1 ·K −1 thermal conductivity. This work establishes an effective environmentally friendly aqueous processing route for a high‐performance Si 3 N 4 thermal management substrate.