What is Ceramics?
Glass, tiles, pottery, porcelain, bricks, cement, diamond, and graphite – you can probably see from this short list that “ceramics” is a very broad term and one of them is that you have a hard time defining it.
From a chemical point of view, we define ceramics in terms of what they are not. So you will find most science textbooks and dictionaries that tell you ceramics are nonmetallic and inorganic substances (not metals or based on carbon compounds); In other words, ceramic is when we remove metals and organic materials (e.g. wood, plastic, rubber, and a thing that was alive).
Some books try to define ceramics as a “refractory” material, which is a technical, literary science term that means it is able to withstand the daily pressures of temperature, salts, and normal wear-tears. It is often easy to define materials in terms of their properties (for example, how bad they are when we heat them, how much electricity goes through them, or soaks them in water). But once you start doing that things can get confusing. For example, graphite is considered a ceramic because it is nonmetallic and inorganic, yet (more than most ceramics) it is softer, more easily worn, and a better conductor of electricity so if you just look at the properties of graphite, you will not consider it ceramic at all. Diamond is also ceramic for the same reason; their properties may not be much different than graphite, but they are similar to other ceramics.
Types of Ceramics
People first made pottery, glass and brick are some of the oldest man-made materials thousands of years ago and we are still designing new ceramic materials – catalytic converters for today’s cars and high-temperature superconductors for tomorrow’s computers. General-purpose ceramics, such as brick and glass, and modern engineered ceramics have many differences between ceramics, such as filtering soot from a truck’s dirty diesel engine, or for a specific purpose.
Bricks, pottery, glass, porcelain, tiles, cement, and concrete are our classic, time-tested ceramics. Although their overall use is different, we can still consider them for a general purpose. We can keep them in or out of our homes; Walls, floors, or ceilings, and we can stick the glass in our windows or hang it on the screen of the smartphone – we can even drink champagne from it. Ceramics like these are ancient materials – as our ancestors may have known – gradually found more and more useful as they have been worn for centuries.
Advanced Engineering Ceramics
In contrast, advanced ceramics have been engineered for very specific applications mostly in the early 20th century. For example, silicon nitrides and tungsten carbides are designed to make exceptionally rigid, high-performance devices – although they have other uses. Most modern engineered ceramics are metal oxides, carbides, and nitrides, meaning compounds formed by combining metal atoms with oxygen, carbon, or nitrogen atoms. So, for example, we have tungsten carbide, silicon carbide, and boron nitride, which are rigid, cutting-tooling ceramics; Aluminum oxide (alumina) and silicon dioxide are used to make integrated circuits (“microchips”); and lithium-silicon oxide is used to make heat-protective nose cones on space rockets. High-temperature superconductors are made from crystals of yttrium, barium, copper, and oxygen.
Not all high-tech ceramic materials are simple compounds. There are some composite materials, which form a kind of background material called ceramic matrix, which is reinforced with fibers of another material (often carbon fiber or sometimes completely different ceramic fibers). Materials like these are known as ceramic matrix composites (CMCs). Examples include silicon carbide fibers in the silicon carbide matrix with boron nitride in their interface – a material used in sophisticated gas-turbine jet engines.
Properties of Ceramics
The most important common properties of ceramics are that they are resistant, they are a rough and tangled material that will withstand the right amount of abuse under extremely normal and unusual conditions.
· High melting points (i.e. they are heat resistant).
· Great rigidity and strength.
· Considerable durability (they are long-lasting and tough to wear).
· Low electrical and thermal conductivity (they are good insulators).
· Chemical inertia (they are unpleasant with other chemicals)
Most ceramics are also non-magnetic materials, although ferrites (iron-based ceramics) make excellent magnets (because of their iron content).
These are useful points, but, if you think about traditional ceramics like glass or porcelain, you may also see a big flaw: they can be fragile and brittle and if you leave them they will crack or break (subject to “mechanical shock”) or suddenly Change their temperature (“thermal shock”).