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What are Silicon Nitride Properties?

Views : 67
Author : Trunnano
Update time : 2022-06-01 11:59:27
Silicon nitride is considered a very important engineering ceramic. At high temperatures, silicon nitride exhibits excellent mechanical properties, including low density, high bending strength, high elastic modulus, fracture toughness, high wear, and resistance to solid particle erosion. The material also shows excellent thermal properties, minimizes expansion and contraction due to temperature, and can withstand thermal shock (rapid, significant temperature changes). Finally, silicon nitride has excellent chemical properties, including stability to most acids and bases, corrosive gases, and liquid metals. 
 
Rolling contact fatigue (RCF) tests on several ceramic-based materials subjected to high-performance bearing loads show that only completely dense silicon nitride can outperform bearing steel. The all-compact Si3N4 bearing material shows that the service life of RCF is ten times longer than that of high-performance bearing steel. A high-speed rotating body may cause significant centrifugal stresses. As a low-density material, silicon nitride is as light as aluminum. However, this property also brings another benefit to the material. The low density of Si3N4 reduces the centrifugal stress on the outer ring of the high-speed rotating body. The high tensile strength of silicon nitride ceramics resists elongation and provides excellent flexural strength to withstand yield or rupture under elevated lateral stresses. The full density Si3N4 also exhibits high fracture toughness and high modulus, which makes the material have excellent resistance to various wear phenomena. This allows it to withstand harsh operating conditions that can cause other ceramic materials to crack, deform or collapse.
 
In addition to its superior mechanical properties, silicon nitride exhibits a range of superior thermal properties, making it suitable for demanding industrial applications. Thermal conductivity is the inherent ability of a material to transfer or conduct heat. The heat transfer coefficient is a key factor in characterizing the suitability of engineered materials to extreme temperature requirements for any industrial application. Due to its unique chemical composition and microstructure, silicon nitride has the same low thermal conductivity as metals.
 
These properties enable silicon nitride to significantly reduce thermal conductivity in extreme temperature applications. Thermal expansion is another problem that occurs when materials are heated and their size and volume increase in small increments. This expansion depends on the material being heated. The degree of expansion of a material per 1°C increase is indicated by its ratio of thermal expansion coefficients. The strong atomic bond of Si3N4 gives the material a low coefficient of thermal expansion, resulting in a very low deformation with temperature.
 
Due to its superior thermal quality, silicon nitride radio frequency (RF) characteristics are less affected in high-speed applications than other ceramics. Silicon nitride is the preferred material for a variety of RF applications because of its moderate dielectric constant (the ability of a substance to store electrical energy in an electric field) and low RF losses, as well as excellent strength and heat resistance.
 
It is the unique combination of properties of silicon nitride that has led to further research into its use as structural ceramics in biomedical applications. The biocompatibility of silicon nitride was established as early as the late 1980s, confirmed by initial in vitro studies and subsequent studies involving the implantation of silicon nitride into animals. A 1999 study further supported the claim of biocompatibility of Si3N4 for the proliferation of functional human bone cells in vitro (in vitro). These findings further promote silicon nitride as an emerging biomedical material. In addition to its biocompatibility, silicon nitride is known to have surface chemical properties that favor bone formation (osteogenesis) and increase bone contact with implants.
 
Silicon nitride has excellent stability due to its strong atomic bonds, which makes the material highly resistant to corrosion from acidic and alkaline solutions at room temperature.  This is critical when considering long-term implantation in a watery and salty human environment. Corrosion resistance is mainly due to the formation of an oxide layer on the surface of the material. The same resistance was observed when silicon nitride was exposed to hot gases, molten salts, and metals, and when corrosion tests were performed in complex environments. This formation of the oxide layer plays a central and complex role in the corrosion resistance of materials.
 
Because of its self-reinforcing microstructure, extremely high strength and toughness, and many excellent properties, silicon nitride is an attractive structural component for a wide range of applications in a variety of industries, including biomedical applications. 
 
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