Pressed Technical Ceramics : Mullite

Pressed technical ceramic mullite

Mullite Pressed Technical Ceramics

Pressed ceramic products complete the range of ceramics supplied by Final Advanced Materials. This range is suitable for applications which are subject to less severe constraints. The requisite properties for these applications are achieved by firing to a temperature in excess of 1,000 °C, i.e. a temperature which is lower than that required for the production of sintered or machinable ceramics.

Parts are produced by shaping in dry presses, by a liquid method, or by extrusion. Treatment is possible in the raw state.

Mullite is a ceramic which is produced artificially, on the grounds of its rarity in the natural state. It is comprised of kaolin or clay, mixed with alumina and silica. These elements are transformed into mullite after firing. Mullite is valued for its refractory properties: low thermal expansion, low thermal conductivity, excellent thermo-mechanical stability and excellent resistant to thermal impacts. It also shows good resistance to deformation – a useful property for components which are exposed to high pressure.

Applications of Mullite Pressed Technical Ceramics

  • Support for heating conductors
  • Spark protection
  • Gas engineering
  • Electric heating systems
  • Components for cartridge heaters
  • Electric heat accumulators
  • Electrical resistors

Benefits of Mullite Pressed Technical Ceramics

  • Hardness
  • High mechanical resistance
  • Dimensional stability, even at high temperatures
  • Resistance to wear and corrosion
  • Electrically insulating
  • High-temperature withstand
  • Chemical resistance
  • Dielectric and ferro-electric properties

Design

Pressed ceramics are materials which are subject to particular design considerations, as they are not ductile and have a very high melting point. Preliminary powdering is necessary, prior to the consolidation of the material form at a high temperature. Various processes are available for this purpose: these include the liquid, plastic, or dry method.

Final Advanced Materials employs the liquid method for the formation of its basic ceramic products. The powdered raw material is dispersed in a solvent, together with a binder. This solid material in suspension forms the ceramic slip. It is then compacted in a tool in order to obtain the desired component. This step is described as extrusion. The extrudate must then be allowed to dry, before being fired at a high temperature. During sintering, the material grains bond together to consolidate the final product.

Technical Data of Mullite Pressed Technical Ceramics

Property

Unit

Mullite

DIN EN 60 672 Identification

C620

Composition

%

3Al2O3•2SiO2

Density

g/cm3

2.8

Bulk Porosity

%

0.3

Colour 

white

Mechanical Characteristics at 20 °C

Hardness on Vickers’ scale HV10 

MPa

750

Compressive Strength 

MPa

551

Flexural Strength 

MPa

180

Elastic Modulus

GPa

150

Thermal Characteristics

Max. Operating Temperature 

°C

1,700

Specific Warmth at 20 °C 

J K−1 kg−1

-

Thermal Conductivity at 100 °C 

W.m-1.K-1

2.2

Expansion Coefficient from 20 to 1,000 °C 

10-6/K-1

5.3

Electrical Characteristics

Electrical Resistivity

at 20 °C

Ω.m

1012

at 600 °C

102



Physical variables included in this documentation are provided by way of indication only and do not, under any circumstances, constitute a contractual undertaking. Please contact our technical service if you require any additional information.

Pressed Technical Ceramics (182.57k)

Data Sheet: Pressed Technical Ceramics