A ceramic ceramic is an inorganic ceramic material. It does not shrink while sintering. Silicon nitride has a strong structure, particularly hot-pressed silicon, and is among the most hard materials on the planet. This material has high strength, low densities, and high resistance to high temperatures, among other characteristics.
Silicon Nitride Ceramic Preparation
Si3N4 ceramics can be prepared using a variety of methods, including hot pressing sintering, atmosphere sintering, pressure sintering, and others.
Reaction sintering method (RS)
This is the standard forming process. It begins by pressing the silicon powder into a desired form. Then, it goes into a furnace to undergo pre-nitriding, or partial nitriding, before being sintered. Already pre-nitrided, the green body has some strength. There are many mechanical operations that can be done to the green body, including turning, planning and milling. Finaly, the silicon melting point is reached. The green body is then fully nitrided to create a product that has little dimension change.
Hot Press Sintering
This uses Si3N4 Powder and small amounts of other additives, such as MgO or Al2O3, FeF2, MgF2, etc. It is pressed at above 1916 MPa, and heated to 1600 degrees for hot pressing molding and sintering. Si3N4 ceramics made using hot pressing sintering are superior to those produced from reaction sintered Si3N4. They have high strength, density and mechanical properties.
The atmospheric pressure sintering technique (PLS).
To increase the atmospheric pressure, the system uses Si3N4’s properties to boost the temperature of decomposition (usually N2 = 1atm and starting at 1800degC). The temperature range for air pressure sintering starts at 1800 to 2000degC after atmospheric sintering.
The air pressure sintering technique (GPS).
At a pressure range of 1-10 MPa, and at temperatures of approximately 2000°C, silicon nitride can be air pressure sintered. This high nitrogen pressure prevents silicon nitride from being decomposed at high temperatures. It is possible to produce a high-toughness ceramic by using high temperatures sintering with less sintering tools. The result is a long-columnar grain structure with an in situ growth rate of > 99.
Silicon Nitride Ceramic Application
It has excellent mechanical properties and corrosion resistance. This makes it a very popular material in many fields, including metallurgy and machinery.
Silicium nitride ceramics in mechanical engineering can be used for making bearings. Cutting tools. High-temperature bolts. Drawing Dies.
Hot-pressed sintered silica nitride ceramic tool have a 5-15x higher cut speed and durability than the cemented carbide ones. Dispersion strengthening is possible by compounding TiC or ZrC. This can improve performance and longevity of silicon-nitride tools.
It has both wear resistance as well as self-lubricating properties. It’s a good bearing material, and lasts longer than ceramic bearings. It’s resistant to corrosion and high temperatures, so it can be used in extreme environments.
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