Silicon Nitride (Si₃N₄) and Aluminium Nitride (AlN) ceramic blocks are both advanced structural ceramics that excel in extreme environments such as high temperatures, corrosion, and high loads due to their excellent physical and chemical properties. Silicon nitride is known for its high strength, high hardness and wear-resistant properties, while aluminum nitride stands out for its ultra-high thermal conductivity and insulating properties, both of which are used in complementary applications in aerospace, electronics, energy and other fields.
Comparison of the characteristics of silicon nitride and aluminium nitride ceramic blocks
Mechanical Properties
Silicon nitride ceramic blocks have a high hardness of HV1200-1600 (Vickers hardness), a bending strength of 800-1200 MPa, a compressive strength of over 3000 MPa, and a fracture toughness of 5-6 MPa・m¹/². The β-Si₃N₄ columnar grain boundaries in its microstructure give it excellent resistance to crack extension, making it suitable for high-impact loads, such as cutting tools and bearing balls.
Aluminum nitride ceramic blocks have a lower hardness (HV300-500) and a bending strength of about 300-400 MPa, making them easier to machine and shape. However, the modulus of elasticity reaches 310 GPa, which is close to that of metallic aluminum and is suitable for structural parts requiring precise dimensions.
Thermal properties
Silicon nitride ceramic blocks are highly resistant to high temperatures, with an oxidation onset temperature of 1400°C and a maximum operating temperature of 1600°C (in an inert atmosphere). It has a low coefficient of thermal expansion (3.2×10-⁶/°C), which makes it a good match for metals and suitable for thermal cycling conditions. However, the thermal conductivity is low (25-35 W/m・K), which limits its application in heat dissipation scenarios.
Aluminum nitride ceramic blocks have a high thermal conductivity of 170-230 W/m・K (close to metallic aluminum), which is one of the best thermal conductivity materials among ceramics. The temperature resistance is a little weak, with a long-term use temperature of about 900-1200°C. However, it has excellent thermal shock resistance (thermal shock index R’ reaches 1500 W/m) and can withstand sudden cold and heat shocks.
Chemical and electrical properties
Silicon nitride ceramic block is chemically inert, does not react with strong acids and alkalis except hydrofluoric acid, and is resistant to erosion by metal melts such as aluminum and iron. Dielectric constant 9-10, dielectric loss 10-³ (1 MHz), suitable for high-frequency insulation scenarios.
Aluminum nitride ceramic blocks are slightly less resistant to corrosion than silicon nitride but have excellent stability against molten metals such as aluminum and zinc. With a dielectric constant of 8.5, a dielectric loss of <10-⁴ (1 MHz) and a high thermal conductivity, they are ideal ‘insulating – thermal conductive’ bifunctional materials.
Comparison of Silicon Nitride and Aluminium Nitride Ceramic Blocks Application Scenarios
Aerospace
Silicon Nitride Ceramic Blocks: Used in engine combustion chamber nozzles and turbine blades to replace traditional nickel-based alloys, reduce weight and improve efficiency by utilizing its high-temperature resistance and thermal shock resistance.
Aluminum nitride ceramic blocks: used to make heat dissipation frames for satellite electronic equipment, quickly exporting heat from the chip and meeting the insulation requirements in the space environment.
Electronics Industry
Silicon nitride ceramic blocks: dielectric filters and packaging housings for high-frequency communication equipment, taking advantage of their low dielectric loss and high stability.
Aluminum nitride ceramic blocks occupy more than 90% of the global market for high-power LED heat dissipation substrates, with a thermal conductivity 5 times higher than that of alumina, significantly extending device life.
Energy and Environmental Protection
Silicon nitride ceramic blocks: support structure for fuel cell stacks, resistant to high temperature of 800℃ and strong corrosive gases (e.g., CO₂, H₂O).
Aluminum nitride ceramic blocks: insulating sleeves for nuclear reactor control rods, ensuring safe heat dissipation through its radiation resistance and thermal conductivity.
Precision Manufacturing
Silicon nitride ceramic blocks: Spindle bearings for ultra-precision grinding machines, with an accuracy of 0.1μm class and a life span of 5-8 times that of steel bearings.
Aluminum nitride ceramic blocks: guideway slides for semiconductor wafer cutters, low coefficient of friction (0.002) combined with high rigidity, suitable for nanoscale processing.
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