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Overview: 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.
We supply the following ceramics as standard products:
- Mullite
- Steatite
- Porous steatite
- Cordierite
- Porous cordierite
Applications of 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 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
Comparative Table
|
Property |
Ceramic |
Metal |
Polymer |
|
Hardness |
High |
Low |
Bad |
|
Elastic Modulus |
High |
Good |
Low |
|
Resistance to High Temperature |
High |
Low |
Bad |
|
Thermal Expansion |
Low |
Good |
Good |
|
Malleability |
Low |
Good |
Good |
|
Corrosion Resistance |
Good |
Low |
Low |
|
Erosion Resistance |
Good |
Low |
Low |
|
Electrical Conductivity |
Low |
Good |
Low |
|
Density |
Average |
High |
Low |
|
Thermal Conductivity |
Average |
Good |
Low |
Design
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.
Our range of Pressed Technical Ceramics
Mullite
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.
Synthetic Steatite
Two types of synthetic steatite, by opposition to natural steatite which is used in machinable ceramics, are avalaible:
Non-Porous Steatite
Non-porous steatite is a very delicate mineral, the main component of which is talc. It provides a cost-effective option for insulation and machining, without the necessity for particular tooling. Its electrical resistance remains high, even at high temperatures, and it shows good mechanical resistance.
Porous Steatite
Porous steatite has similar properties to normal steatite. However, it shows a lower mechanical resistance, and is more resistant to thermal impacts, due to its porosity.
Synthetic Cordierite
Two types of synthetic cordierite, by opposition to natural cordierite which is used in machinable ceramics, are avalaible:
Non-Porous Cordierite
Non-porous cordierite is a rock which is equally at home in jewellery as in the refractory industry. It has multiple qualities: low thermal conductivity and a low coefficient of expansion, resistance to heat, low dielectric losses, resistance to corrosion, particularly by molten metals, and excellent high-pressure vacuum withstand. Moreover, its limited thermal expansion is beneficial for components with stringent tolerances.
Porous cordierite
Porous cordierite shares numerous properties with normal cordierite. However, it has a lower mechanical resistance. Its porosity nevertheless permits the more effective accommodation of thermal impacts.
Comparative Table
A comparative table for the available pressed technical ceramics can be downloaded in the data sheet.
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.
FAQs that can help you in this category
Pressed cordierite, with a density of 2.1 g/cm3, has a low thermal expansion coefficient (2–4.5×10-6/K), providing excellent thermal shock resistance and resistance to rapid thermal cycling. Steatite, with a density of 2.7 g/cm3, has a high dielectric strength (~15 kV/mm) but a lower thermal shock resistance. Mullite, with a density of 2.8 g/cm3, stands out for its stability at high temperature (up to 1,700°C) and its chemical resistance. To help you choose the type of pressed ceramic best suited to your requirements, Final Advanced Materials takes into account the application, but also the material’s thermal resistance, mechanical resistance and electrical insulation.
Pressed steatite has the best electrical insulation, with a dielectric strength of 15 kV/mm and a resistivity of over 105 at 600°C. It withstands temperatures as high as 1,000°C and has excellent dimensional stability. Cordierite and mullite have lower dielectric strengths (10 kV/mm) but are less suited to high tensions. Final Advanced Materials recommends steatite for high-voltage electrical components such as supports, insulators and electrical resistor caps.
For thermal applications requiring thermal shock resistance, it is recommended to use porous pressed ceramics. Porous steatite, with a density of approximately 1.8 g/cm3 and a thermal expansion coefficient of approximately 8-9x10-6/K, can resist to temperatures up to 1,000°C. Porous cordierite, with a density of approximately 1.9 g/cm3 and a thermal expansion coefficient of approximately 4-6x10-6/K, can resist to temperatures up to 1,200°C. Porosity slightly improves the resistance to thermal shock, but steatite has a higher thermal expansion coefficient than cordierite. Final Advanced Materials therefore recommends porous cordierite rather than porous steatite for applications requiring thermal shock resistance.
Pressed mullite (3Al2O3.2SiO2), with a density of approximately 2.8 g/cm³ and a flexural strength of 180 MPa, has an excellent chemical and mechanical stability up to 1,700°C, and also offers an excellent thermal shock resistance and low thermal conductivity (2.2 W/(m.K). Its low expansion coefficient (5.3×10-6/K) limits deformation due to temperature. Its corrosion resistance and oxidisation resistance are higher than those of steatite and cordierite. Final Advanced Materials recommends mullite for industrial ovens, burner components and high-temperature chemical applications requiring stability and durability.