The Effect of Amorphous Si₃N₄ Nanoparticles and Magnetized Distilled Water on the Mechanical Properties and Infrared Transmittance of α-Al₂O₃

The objective of this study was to enhance the mechanical and optical properties of α-Al ₂ O ₃ ceramics through the incorporation of amorphous Si ₃ N ₄ nanoparticles, in conjunction with MgO and La ₂ O ₃ sintering aids. Samples were fabricated using the shear stress-thin layer (S-T) method with slurry prepared in magnetized distilled water. The effects of dispersant concentration, slurry pH, and annealing treatment were systematically examined. The material's hardness, fracture toughness, Young's modulus, and infrared transmittance were evaluated using a combination of analytical methods, including hardness and toughness tests, X-ray diffraction (XRD), infrared spectroscopy (IR), and field-emission scanning electron microscopy (FESEM). The incorporation of 0.1 wt% Si₃N₄ and 2 wt% dispersant at a pH of 10 resulted in a reduction in hardness from 23.6 GPa to 16 GPa and an enhancement in fracture toughness from 3.4 MPa·m ^1/2 to 6.3 MPa·m ^1/2 . Annealing at 1200°C for 4 hours led to a significant reduction in hardness to 12.6 GPa and an enhancement in toughness to 7.7 MPa·m ^1/2 . The Young's modulus demonstrated a decrease from 403 gigapascals (GPa) to 230 GPa, indicating a reduction in brittleness. Optical analysis demonstrated that under optimal conditions, infrared transmittance reached 85% in the 3–6 µm range.