About Silicon Nitride Ceramics
Silicon nitride (Si3N4) is a high melting point ceramic material with extremely high hardness and chemical inertness. Especially hot-pressed silicon nitride is one of the hardest materials in the world.
Silicon Nitride has the most versatile combination of mechanical, thermal, and electrical properties of any technical ceramic material. It is a high performance technical ceramic that is extremely hard and has exceptional thermal shock and impact resistance. It surpasses most metals high temperature capabilities and has a superior combination of creep and oxidation resistance. Additionally, its low thermal conductivity and high wear resistance make it an excellent material that can withstand the toughest of conditions in the most demanding industrial applications. Silicon Nitride is an excellent choice when high-temperature and high-load abilities are needed.
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Available Grades of Silicon Nitride
- Gas Pressure Sintered Silicon Nitride (GPSN)
- Hot Pressed Silicon Nitride (HPSN)
- High Thermal Conductivity Silicon Nitride Substrate (HTCSNS)
Silicon Nitride Ceramic Product Display:
Gas Pressure Sintered Silicon Nitride (GPSN)
This is the most popular method for producing high-strength and complex geometry silicon nitride components. The GPSN method uses a silicon nitride powder that has been mixed with sintering aids to promote liquid phase sintering (typically yttria, magnesium oxide, and/or alumina) as-well-as binders to improve the mechanical strength of green ceramic body. The powder is pressed into the desired form and green-machining can take place. The compacts are then placed into a furnace that has a pressurized nitrogen atmosphere to aid with densification and prevent the evaporation/decomposition of the silicon, nitrogen and additives.
Hot Pressed Silicon Nitride (HPSN)
HPSN is produced by uniaxially pressing silicon nitride powder (with sintering additives) while applying heat at the same time. A special type of press and die is required for this process. It produces a silicon nitride with excellent mechanical properties, however, only simple shapes can be produced. Because it is impossible to green-machine a component that is hot-pressed, diamond grinding is the only way to create complex geometries. Because of the high costs and difficulties associated with diamond grinding and hot-pressing, its use is typically limited to the production of simple components in small quantities.
Why use silicon nitride ceramics?
- Very low density;
- Very high fracture toughness;
- Good bending strength;
- Excellent thermal shock resistance: high thermal stress parameters;
- Extremely high operating temperature.
|Colour||——||Gray or black||Gray or black||Gray or black|
|Modulus of Elasticity||GPa||300||300||300~320|
|Maximum Use Temperature||℃(No load)||1100||1300||1100|
|Thermal Conductivity @ 25°C||W/(m・K)||15~20||20~25||80~100|
|Thermal Expansion a at 40–400°C||1 x 10-6/°C||3||3.1||3|
|Thermal Shock Resistance||℃(Put in water)||550||800||——|
|Volume Resistivity @ 25°C||Ω・cm||＞1014||＞1014||＞1014|
|Volume Resistivity @ 500°C||Ω・cm||＞1010||＞1010||＞1010|
*The values are typical material properties and may vary according to products configuration and manufacturing process. For more details, Please feel free to contact us.
What is the use of silicon nitride ceramics?
- Rotating ball & rollers bearings
- Cutting tools
- Engine components
- valves, rocker arm pads, seal faces
- Induction heating coil supports
- Turbine blades, vanes, buckets
- Welding & brazing jigs
- Heating Element components
- Metal tube forming rolls and dies
- TIG / Plasma welding nozzles
- Weld positioners
- Precision shafts and axles in high wear environments
- Thermocouple sheaths & tubes
- Semiconductor Process Equipment
Silicon Nitride Machining & Grinding
Silicon nitride can be processed in green or fully dense state. In the green state, it can be processed into complex geometry relatively easily.However, the sintering process that is required to fully densify the material causes the silicon nitride body to shrink approximately 20%. This shrinkage means that it is impossible to hold very tight tolerances when machining silicon nitride pre-sintering. In order to achieve very tight tolerances, fully sintered material must be machined/ground with diamond tools. In this process a very precise diamond coated tool/wheel is used to abrade away the material until the desired form is created. Due to the inherit toughness and hardness of the material, this can be a time consuming and costly process.
Buy Custom Silicon Nitride Components
Great Ceramic is your silicon nitride machining specialist for your precision ceramic prototyping & manufacturing needs; we are always happy to use our many years of advanced ceramics experience to provide advice on materials, design, and application. If you would like to buy silicon nitride plates, rods, tubes or custom machined components, please contact us and one of our experts will be happy to assist you.
Compared with other technical ceramics, its low thermal expansion coefficient provides good thermal shock resistance. It is very hard, exceeding the high temperature capability of most metals, and also has excellent oxidation resistance. Therefore, silicon nitride can withstand the harshest conditions in the most demanding high-temperature, high-load applications.
Silicon nitride ceramics have low thermal expansion coefficient and high thermal conductivity, so it has excellent thermal shock resistance. At not too high temperature, silicon nitride has high strength and impact resistance, but it will be damaged with the increase of use time above 1200℃, which will reduce its strength, and fatigue damage will occur more easily above 1450℃. Therefore, the service temperature of silicon nitride generally does not exceed 1300°C.
The molecular weight of silicon nitride is 140.28, the chemical formula is Si3N4, and it dissolves at 1900°C under pressure. After high temperature sintering, the color is usually gray or black.