Silicon Aluminum Oxynitride is in fact a fine-grained nonporous advanced ceramic material with less than
1 vol.% open porosities. Silicon Aluminum Oxynitride is made of a silicon nitride ceramic with a small percentage
of aluminum oxide. Its generally adopted chemical formula is Si6-xAlxOxN8-x. This superior
refractory material has the combined properties of silicon nitride, i.e., high-temperature
strength, hardness, fracture toughness, and low thermal expansion, and that of aluminum
oxide, i.e., corrosion resistance, chemical inertness, high temperature capabilities, and oxidation resistance.
Silicon Aluminum Oxynitride exhibits a medium density of 3400 kg.m–3, a low Young's modulus
of 288 MPa, a bulk modulus of 220 GPa, and a shear modulus of 120 GPa with a Poisson
ratio of 0.25. Moreover, it has a flexural strength of 760 MPa, an elevated Vickers hardness
(1430 to 1850 HV), and a good fracture toughness (6.0 to 7.5 MPa.m–1/2). In addition, like
pure silicon nitride, the combination of a low Young's modulus of 288 GPa with a low coefficient of linear thermal expansion (3 μm/m.K) ensures an excellent thermal shock resistance together with a low thermal conductivity of 15 to 20 W.m–1K–1. Moreover, silicon aluminum oxynitride exhibits a good oxidation resistance in air up to 1500°C imparted by its alumina
content, and it has an outstanding corrosion resistance to molten nonferrous metals. Moreover, it is neither wetted nor corroded by molten aluminum, brass, bronze, and other common industrial metals.
Typical uses of Silicon Aluminum Oxynitride are as protection sheath for immersion thermocouples used in nonferrous metal melting, immersion heater and burner tubes, degassing and
injector tubes in nonferrous metallurgy, metal feed tubes in aluminum die casting, welding,
and brazing fixtures and pins.
