Silicon Nitride (Si3N4)

2023 11/04

Silicon Nitride has very good synthetical properties, such as extremely high strength, outstanding crack resistance, excellent wear and chemical resistance, good heat conductivity, very low heat expansion, excellent thermal shock capability (ie; cycles from RT to 750°C in 7 seconds and repeated every 30 seconds), not wetted by many metal and alloys, and electrically insulating. Due to these properties and its low weight, silicon nitride is a material for the highest demands. Silicon Nitride is produced in three main types: Reaction Bonded Silicon Nitride (RBSN), Hot Pressed Silicon Nitride (HPSN) and Sintered Silicon Nitride (SSN). RBSN gives a relatively low-density product compared with hot pressed and sintered Silicon Nitride. HPSN and SSN materials offer better physical properties suitable for more demanding applications. Typical Applications include:
* Molten metal handling (including crucible / wear plates)
* Induction heating coil supports
* Welding nozzles, fixtures and weld location pins
* Dental heat treatment supports
* Thermocouple sheaths
* Bearings and rollers
* Glow plugs
* Cutting tools

Properties of Silicon nitride ceramics (Si3N4)
Property	Item	Data	Unit
Mechanical Characteristics	Color	Grey/Black
	Density	3.22	g/cm³
	Bending Strength	750	MPa
	Compressive strength	3,800	MPa
	Elastic Modulus	290	GPa
	Fracture Toughness	7	MPa m^1/2
	Weber Coefficient	15	m
	Vickers Hardness (HV 0.5)	1,700	MPa
Thermal Characteristics	Coefficient of Line Thermal Expansion	2	10^-6K^-1
	Thermal Conductivity	20	W/mK
	Thermal Shock Resistance (Put in Water)	750	∆T °C
	Max Working Temperature	1,300	°C
Electrical Characteristics	Volume Resistance at 20°C	>10¹⁴	Ωcm
	Dielectric Strength	10×10⁶	V/m
	Dielectric Constant	-	ε_r
	Dielectric Loss Angle at 20°C(1MHz)	-	tanδ
Chemical Characteristics	Nitric Acid (60%) 90°C	1	WT Loss mg/cm²/day
	Sulphuric Acid (95%) 95°C	≒0.00
	Caustic Soda (30%) 80°C	0.2

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