Effect of different preparation methods on the microstructure and mechanical properties of Si3N4 ceramic composites

In this study, Si₃N₄ ceramic composites were fabricated by using ball-milling, titration preparation and urea preparation methods, respectively. The effect of different preparation methods on microstructure and mechanical properties of the Si₃N₄ ceramic composites was investigated. Obviously, the Si₃N₄ ceramic composite prepared by the urea preparation method (U-SN sample) showed better sintering behavior and higher mechanical properties than that prepared by the other two methods. Compared with the Si₃N₄ ceramic composite by the titration preparation method (T-SN sample), we could avoid the complex titration process or uncontrollable pH value during the preparation process of the U-SN sample. Meanwhile, the coated Y-Al precursor layer in thickness of nanometers was more homogeneous than that prepared by the traditional titration method. B-SN represented the Si₃N₄ ceramic composite prepared by the ball-milling method. These samples were all sintered from room temperature to 1750 °C via hot-pressing sintering. The U-SN specimen showed the optimal flexural strength and fracture toughness of being 817 MPa and 6.90 MPa/m², respectively, which could be attributed to its smallest grain size (0.46 µm) among these three samples.