Directives for application ceramics
Ceramics, thanks to its wealth and properties diversity are present in a wide range of activities, replying thus to traditional industries requirements and also to the high-tech industries needs.
Ceramics find their application in mechanic for manufacturing mechanical pieces when the technical requirements asks very high performances
| Ceramics | Material |
|---|---|
| Wear resistance | All but specially Si 4N 3, ZrO 2 |
| High temperature | AL 2O 3--> 1700 °C |
| Flexural strength | AIN |
| Thermal stability | Si 4N 3 |
| Hardness | SiC |
Ceramics are used in electronic field because of their electrical and thermal properties.
| Ceramics | Properties | Materials | Applications |
|---|---|---|---|
| Insulating | High electrical and thermal Resistivity |
Al 2O 3 |
Microelectronics
|
| Dielectric | Dielectric rigidity Permittivity Dielectric constant |
BaTiO 3, SrTiO 3, CaTiO 3, Al 2O 3 Cordierite |
Capacitors Substrates Electrodes |
| Thermistor | Electrical Resistivity decrease in function of temperature | BaTiO 3 | Temperature sensors |
| Varistor | Electrical Resistivity increase in function of temperature | SiC, ZnO | Safety gap |
| Heating elements | High electrical conductivity | SiC, MoSi 2, LaCr 2O 3 | Resistors |
| Chemical sensor | High ionic conductivity | Al 2O 3,, ZrO 2, TiO | Humidity captor, of gas |
Ceramics are used in aeronautic and spatial field for their thermo structural properties:
- refractoriness : resistance to temperatures > 1000°C
- resistance to particular atmosphere
- resistance to mechanical reliability
The ceramic reinforcement thanks to fibres: the C.M.C. (Ceramic-Matrix Composite), allow using, for the manufacturing of various complex parts:
- turbine elements
- combustion chamber
- thermal protection
- thermal shield
Ceramics are used in metallurgy, refractory, for their properties of:
- High temperature mechanical resistance
- Thermal impacts resistance
- Resistance to chemical shocks
There are essentially 3 big refractory ceramics families:
- The acid refractories of the alumina-silica system
- The basic refractories from magnesia-dolomite-chromite
- The special or neutral refractories : carbon, carbide, nitride …
The refractories ceramics find their application in metallurgy for the manufacturing of cores, shell mould …
| Refractories | Properties | Materials | Applications |
|---|---|---|---|
| ACIDS | |||
| Silicate | Low creep Thermal impact resistance >800°C | SiO 2 > 93% | Crown, glassware fusion |
| Clay | High thermal dilatation and conductivity | 20% < Al 2O 3 < 45% | Kilns realization |
| Alumina | High corrosion resistance | Al 2O 3 > 45% | Blast-furnace |
| High refractory Very good resistance to corrosion | MgO Cr 2O 3 |
Non-ferrous metal fusion Electric kilns | |
| NEUTRAL Exp: Carbon |
Low dilatation coefficient Excellent chemical resistance | Carbon | Electrolyse pot packing Cruci |
| Materials | Properties | Shaping Technology | Applications |
|---|---|---|---|
| Yttried Zirconium | Ionic conduction ionic by ions O2 |
|
|
| Composed with perovskite structure |
Mixed-base conduction (ionic and electronic conduction by ions O2) Proton conduction (by H+) |
|
|
The technical ceramics are very important in environment field thanks to:
- Controlled porous structure
- Their high thermal properties.
Ceramics are used for realization of:
-
Gas detection sensor:
- Materials : oxide with rare earth or transition elements
-
Catalyst - catalytic converter
- Materials : cordierite, SiC
-
Filters for agro-foodstuffs and water purification
- Tubular shaping porous materials, multichannel or plan
- Particle filters for diesel engine
- Waste treatment : waste vitrification