Chemically, ceramics consist essentially of oxides, carbides and nitrides, thus encompassing infinite possibilities and mixing compositions. They have always been present in the history of mankind, from clay, bricks, pottery and porcelain, to superconducting and refractory tiles used in sophisticated technological applications.
In our homes, ceramic materials make up the tiles of the floors and roofs, the earthenware of the dishes, the glass of the windows, the hardness of the toilets and sinks, even the cement and all the solidified pastes that were used to build the buildings that we inhabit.
Ceramic material properties
As there are so many ceramics, it is difficult to establish properties that can describe them all, as there will always be several exceptions. However, most share the following general properties in common :
The crystalline structures of ceramic materials cannot be molded to elastically counteract the physical forces that seek to break their solids. Therefore, they are brittle, brittle.
The bonds in ceramic materials are very strong, so their atoms are firmly confined in their respective positions. This gives them great hardness, even when they are brittle solids.
Thermal and electrical conductivities
Ceramic materials are generally not good conductors of heat or electricity, so they behave as insulators. However, many ceramics contradict this characteristic, including excellent thermal and electrical conductors, as well as semiconductors.
Ceramic materials are weak to compression, which makes them weak solids.
Ceramics stand out for being considerably inert solid, resisting organic solvents and corrosive substances without losing their quality.
Many ceramics are transparent, although there are also translucent and opaque ones.
One of the main characteristics of ceramic materials is their high thermal resistance, since they melt at very high temperatures. It is for this reason that they are considered refractory solids, made to withstand flames and temperatures above 1,000 ° C.
Ceramic materials are characterized by being very durable. Proof of this we see perfectly in the bricks of old constructions, as well as in the floor tiles, which resist the friction of the furniture when being dragged, the blows of the objects that fall on them, over the years. footsteps, etc.
Types of ceramic materials
As with characteristics, it is not easy to classify ceramic materials in a satisfactory and definitive way. That is why the types in which ceramics are usually classified will be exposed here.
Crystalline ceramics are all those that are obtained from fire and multiple processes, such as sintering, which consists of compacting the powders produced to form a final solid.
Their structures are ordered, whether they are ionic crystals or three-dimensional networks of covalent bonds.
Non-crystalline ceramics are all those with a glassy appearance, which is why they are glass. In general terms, they are obtained by solidifying and cooling the molten solids that are mixed to give rise to the ceramic material. Their structures are messy, amorphous.
Traditional and modern
Ceramic materials can also be classified as traditional or modern.
The traditional ones are all those that have been known for millennia and are made from clay or silica, outlining clays and porcelains together with their variants.
On the other hand, modern ones are those that have been emerging for 100 years due to new technological and industrial demands. Among them we have carbides, semiconductors and composite ceramics.
There are numerous ceramic products for specialized or home use:
- Bricks, pipes, tiles, apartment floors.
- Gas radiators, furnace lining.
- Kitchen utensils: knives, tiles, dishes.
- Technical-advanced ceramics: ballistic protection, vehicle armor, biomedical implants, space shuttle ceramic tiles.
Ceramics, specifically titanium and zirconium oxides, can be used as biomaterials in the supplantation of teeth and bones.
Some ceramic materials are extraordinarily hard, which is why they are used to make drills and cutting tools, with which metals or other solids are machined, cut and molded. Likewise, they are usually abrasive materials, with which various surfaces are polished.
Electric motors are composed of magnets made from ceramic ferrite.
There are ceramic materials that have phosphorescent properties, and therefore are used in electronic devices to produce LED lights.
Being poor conductors of heat or electricity, they are used as insulators, for example in food containers to keep them warm for longer, or in electrical transformers and generators to control high voltages.
Examples of ceramic materials
Finally, several examples of ceramic materials will be listed, most of them being modern:
-Al 2 O 3 , alumina
-Si 3 N 4 , silicon nitride
-TiN, titanium nitride
-SiO 2 , silica
-ITE, tin oxide and indium
-ReO 3 , rhenium trioxide
-GaN, gallium nitride
-SiC, silicon carbide
-ZrO 2 , zirconia or zirconium dioxide
-B 4 C, boron carbide
-MoSi 2 , molybdenum disilicide
-YBCO or YBa 2 Cu 3 O 7 , yttrium, barium and copper oxide
-BaTiO 3 , barium titanate
-BN, boron nitride
-MgB 2 , magnesium diboride
-Sialon, silicon aluminum oxynitride
-UO 2 , uranium oxide
-ZnO, zinc oxide
-SrTiO 3 , strontium titanate
-CdS, cadmium sulfide
-MgNb 2 O 9 Pb 3 , lead magnesium niobate
Oxide-based ceramics can be structurally complex, including non-stoichiometric solids and endless combinations. Likewise, the cited examples may or may not be doped with metal, metalloid or non-metal atoms, which modifies their properties and, therefore, their final applications.