What Is Silicon Nitride?
Silicon nitride (Si3N4) is an odorless white to gray powder with a molecular weight of 140.28 and is known for its robustness and thermal stability. It was first reported by Henri Etienne Sainte-Claire Deville and Friedrich Wöhler in 1857.
Uses of Silicon Nitride
Employed as a high-temperature structural material, silicon nitride is ideal for components in harsh environments such as engines, gas turbines, and various welding and combustion parts. Its high wear resistance and mechanical strength also make it suitable for use in semiconductor manufacturing equipment, die and mold parts, and wear-resistant applications.
Properties of Silicon Nitride
1. Physical Properties
Notable for its strength at high temperatures, silicon nitride remains stable up to about 1,900°C in inert atmospheres, featuring high toughness, a low coefficient of thermal expansion, and excellent thermal shock resistance.
2. Other Characteristics
While resistant to most acids, silicon nitride is vulnerable to hydrofluoric, hydrochloric, and nitric acids. It undergoes a phase transition from α-type to β-type between 1,400°C and 1,500°C, affecting its structural properties.
Structure of Silicon Nitride
Silicon nitride exists in three polymorphs: α-phase, β-phase, and γ-phase. The α and β phases, which are the focus of material development, have distinct crystal structures and properties, while the γ-phase, synthesized under extreme conditions, resembles cubic boron nitride in structure.
Other Information on Silicon Nitride
1. Production Process
Industrially, silicon nitride is produced through direct nitridation of silicon powder, reduction of silicon dioxide with carbon in nitrogen or ammonia, or vapor phase synthesis from silicon halide or monosilane with ammonia.
2. Legal Information
Not classified under major hazardous substances laws but is noted in the Industrial Safety and Health Law as a substance requiring notification.
3. Handling and Storage Precautions
- Store in a dry, cool, and dark place, ensuring containers are tightly closed.
- Operate in well-ventilated areas or outdoors to avoid contact with water, which can generate alkaline substances.
- Protective gloves and glasses are recommended during use, with thorough washing post-handling.