which consist of dispersing ceramic powders in a solvent (water, alcohol, etc.) in order to obtain a suspension with the desired properties (solvents are then eliminated during subsequent thermal cycles). This suspension obtained makes it possible to carry out casting operations in moulds or tape and deposits by dipping.
Example of tape casting: the suspension is laminated and then dried by infrared radiation before being laser-cut and assembled into multiple layers.
which involve mixing technical ceramic powders with organic bonds in order to obtain a fluid (bonds are removed in subsequent thermal cycles). It is then shaped by injection or extrusion.
Example of injection: the “ceramic fluid” is fed into the hopper, then heated, compressed and injec- ted into the mould before being cooled and removed from the mould.
to agglomerate powder particles for mould filling, giving them sufficient plasticity for deformation during pressing.
Example of single-axis pressing: the mould is filled with the ceramic powders which are then pressed and subsequently removed from the mould.
Technical ceramics have a variety of physical properties that offer suitable solutions where metallic materials and polymers may be ineffective.
Among these properties, the most important are the following:
• Mechanical properties: their extreme hardness offers very good resistance to wear, abrasion and compression.
• Thermal properties: resistant to very high temperatures (up to 2,000°C), ceramics are the reference in refractory materials.
• Electrical properties: some ceramics are excellent electrical insulators and others, on the contrary, are (super)conductors.
• Chemical properties: some possess chemical inertness, biocompatibility and vacuum tightness.
• Optical properties: some transparent ceramics have exceptional optical properties (visible, IR or UV ranges).
=> All these properties make technical ceramics remarkable materials with numerous industrial applications:
The electronics field accounts for 70-75% of global turnover for technical ceramics. Their various compositions and properties of use mean electronic ceramics can be used in a variety of applications: electrical insulation (Al2O3, SiO2, MgO, etc.), semiconductors (SiC, Cu2O, TiO2, etc.), electrical conductors (ReO2, MoSi2 LaB6, etc.) and magnetic ceramics (Fe3O4, NiFe2O4, etc.).
The medical field also uses ceramics, commonly known as “bioceramics”. They are used in medical instruments and systems, reconstructive surgery (prostheses, implants, bone substitutes, etc.) and in the dental field (implants, bridges, etc.). Alumina (Al2O3) and zirconium dioxide (ZrO2) are the most commonly-used ceramics due to their density, purity, tribological qualities and mechanical resistance.
Technical ceramics are commonly used as filters or membranes in the energy and environment fields. Particle filters or catalytic converters (some with honeycomb structure) are made using ceramics and allow the filtering and/or degradation of gas pollutants (SiC often used for its thermal conductivity but also Al2O3, CeO2, ZrO2 on which noble metals are deposited in the particular case of catalytic converters). Ceramics are also used as fuels in the nuclear field (UO2, PuO2, etc.).
The use of ceramic components in the telecommunications field now holds sway, in particular due to their resistance to their environment and the stresses to which they are subjected (humidity, vibrations, temperature variations, etc.).
In the aerospace field too, technical ceramics have a multitude of applications (turbine blades, telescope mirrors, sensors, combustion chambers, engines, etc.).
In order to compensate for their fragility, ceramics can be used as components of composite mate- rials. Ceramics generally make up the matrix containing a set of fibres (glass, carbon, silicon carbide, etc.) called “strengthening”. These composites are called “ceramic matrix composites” (CMC).
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