Materials

PROPERTIES AND USES

Non-oxide ceramics

The materials in the group of non-oxide ceramics are based on compounds with Boron (B), Carbon (C), Nitrogen (N) and Silicon (Si). Due to the presence of covalent bonds, the material has high temperature applications. Stiffness, strength and hardness are also high. Conversely, the density is low.

Various grades have excellent non-wetting properties when used with liquid metals, such as zinc and aluminium.

 

Known qualities of non-oxide ceramics are:

  • Aluminium Nitride AlN
  • Boron Carbide B4C
  • Boron Nitride BN
  • Silicon Carbide SiC
  • Silicon Nitride Si3N4
  • Other non-oxide ceramics

Sialon can be found in the category of other non-oxide ceramics. Sialon is a Silicon Aluminium Oxide Nitride, which has properties similar to Silicon Nitride.

Material properties:

Aluminium Nitride (AlN) has an extremely high thermal conductivity (180 W/mK) and is mostly used as ‘heatsink’ material in the electronics industry.

AlN substrates are used in both thin and thick film technology, and have a pattern consisting of layers of gold or silver.

Hardness HVE-modulus 
GPaBending strength
 MPaDensity 
g/cm3Expansion
 10-6K-1Therm. conductivity W/(mK)T max
 = K
AlN
18012003103903.304.61801000

Boron Carbide (B4C) is almost as hard as diamonds. Boron Carbide properties are similar to those of Silicon Carbide, however, its abrasion resistance is higher. Boron Carbide is used in jet nozzles for shot blasting. Due to its low density combined with high rigidity (high E-modulus) and excellent mechanical properties, the material is widely used in ballistic applications. This includes personal protection as well as protection for tanks and helicopters, for example.

Hardness HVE-Modulus GPaBending strength MPaDensity g/cm3Expansion 10-6K-1Therm. conductivity W/(mK)T max = K
B4C30004504002.505.045500

Boron Nitride (BN) is a soft material that can be machined (drilling, milling etc.) with standard tooling (not diamond tools). Boron Nitride is available in different grades like BN and HPBN.

An important feature of Boron Nitride is that it is not wetted by liquid materials such as aluminium, magnesium and zinc.

Gimex also supplies Boron Nitrides as a coating material. These coatings, which can be applied with a brush or roller, are commonly used in the casting industry.

Hardness HVE-modulus GPaBending strength MPaDensity g/cm3Expansion 10-6K-1Therm. conductivity W/(mK)T max = K
BN18020702.102.525800
BN HPBN20030701.802.5401000

Because of its excellent wear and corrosion-resistance, Silicon Carbide (SiC) is widely used in pumps (mechanical seals, bushings, axles, etc.) as well as protective tubes and as furnace parts.

By taking into account your processing environment, Gimex staff are able to advise you on the best uses for SiSiC, SSiC, HP SiC or RSiC.

SiC has excellent thermal resistance and can be used up to temperatures of 1600°C in oxidizing atmospheres. Silicon Carbide is extremely strong and can be supplied to an extremely high dimensional accuracy.

Hardness HVE-modulus GPaBending strength MPaDensity g/cm3Expansion 10-6K-1Therm. conductivity W/(mK)T max = K
SiC SiSiC22004103203.104.01101400
SiC SSiC25004304203.104.11101600
SiC HPSiC25004505903.204.11801600
SiC RSiC2802.74.7351600 (in air)

There are different types of Silicon Nitride, reaction bonded Si3N4, sintered Si3N4 and hot-pressed Si3N4. Nitrides are known for their excellent thermal properties. The material also has high rigidity properties.

The E-modulus of hot-pressed Si3N4, is 50% greater than that of steel.

Silicon Nitride is highly resistant to temperature changes, and is completely unaffected by liquid aluminium or zinc, for example.

A further striking feature of Silicon Nitride is its low friction coefficient, which is why Si3N4 precision balls are being used more frequently in ball bearings. Gimex has customers who use Si3N4 ball bearings with speeds of 20,000 RPM! At lower speeds, lubrication is not necessarily required.

Hardness HVE-modulus GPaBending strength MPaDensity g/cm3Expansion 10-6K-1Therm. conductivity W/(mK)T max = K
Si3N4 RBSN3001202502.503.0101400
Si3N4 SSN15502757503.303.2351100
Si3N4 HPSN16003208503.203.235100

Gimex differentiates between three materials in the group of other non-oxides:

  • Titanium Diboride TiB2
  • Zirconium Diboride ZrB2
  • Sialon

Titanium Diboride TiB2 and Zirconium Diboride ZrB2 are two grades from the Boridian group. Even though both materials are used relatively little, they are interesting materials, as their electrical conductivity is excellent. For this reason, the material is used to make electrical contacts for components that require a high wear-resistance.

Because Titanium Diboride is not wetted by liquid metals, it is also used for crucibles. Titanium Diboride is also used in the production of ceramic vapour trays. These vapour trays, which are used for metal deposition, consist of 2 or 3 components. In addition to Titanium Diboride for electrical conductivity, these are AlN (thermal conductivity) and BN (non-wetting).

Sialon is a silicon aluminium oxinitride. The combination of Si3N4 enriched with Al2O3 will produce a material with a high degree of toughness. Sialon has excellent thermal shock resistance and, similar to Si3N4, it has good non-wetting properties when used with liquid, non-ferrous metals such as aluminium.

If you would like to receive more information about the range of applications for these materials, please contact a Gimex adviser.

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