The majority of ceramics have a crystalline structure and come in a wide range of compositions and shapes. The bonds between the atoms are mostly ionic and covalent, in some cases. Although both types of bonds exist between atoms in ceramic materials, the ionic bond is the most common. Natural ceramics include silica, silicates and clay minerals, while manufactured ceramics include silicon carbide, silicon nitride, cement, and many more. Ceramics are basically non-metallic inorganic materials which are made up of one or more metals and non-metals like oxygen, carbon or nitrogen. Properties of ceramics are dictated by the types of atoms present, the types of bonding and the way in which atoms are bundled together.
What are ceramics?
A ceramic is a non-metallic inorganic material, composed of metallic or non-metallic compounds that have been formed and then hardened at high temperatures. They are hard, corrosion-resistant and brittle in general. We are all familiar with clay-based home items, art objects and construction materials, but pottery is only one aspect of the ceramic world. Nowadays, the term “ceramic” has a broader definition, encompassing materials such as glass, advanced ceramics and some cement systems.
Bonding in ceramics
Ceramics may have 2 types of bonds: ionic and covalent. The ionic bond is formed when a metal and a nonmetal, or two elements of very different electronegativity, come together. The ability of the nucleus in an atom to attract and maintain all of the electrons inside the atom depends on the number of electrons and the distance between the outer shell electrons and the nucleus. In an ionic bond, one of the atoms (metal) passes electrons to the other atom thus causing the metal to become positively charged and the nonmetal to become negatively charged.
On the other hand, covalent bonding occurs between two nonmetals or atoms of identical electronegativity, which entails the exchange of electron pairs between the two atoms.
Ceramics’ ionic and covalent bonds are responsible for a variety of specific properties, including high hardness, high melting points, low thermal expansion and strong chemical resistance, as well as some undesirable characteristics from which brittleness is the most prominent, which contributes to fractures unless the material is toughened with reinforcing agents.
Properties of Ceramics
The Properties of Ceramics which plays a crucial role in various fields are listed below:
Bond: Ceramics can have both Ionic and Covalent bonds.
Chemical inertness: Ceramics don’t react with other chemicals.
Brittle nature: Ceramics are brittle in nature.
Strength: They have poor impact strength but high hardness and high compressive strength.
Modulus of elasticity: Ceramics have high modulus of elasticity as they have strong bonding than metals.
Electrical properties of ceramics: Ceramics are bad conductors of electricity as they have no free electrons.
Melting point: Ceramics have high melting points.
Durability: They are long lasting as they don’t corrode.
Thermal conductivity of ceramics: Ceramics are not good thermal conductors but they can withstand at high temperatures easily than other materials. They offer poor thermal shock resistance.
Density: Ceramics are less dense than metals.
Stiffness: ceramics show no yielding as they are extremely stiff and rigid.
Piezo-electrical behavior: Some ceramics have ability to exhibit piezo-electric behavior due to which mechanical loading causes potential difference across its surfaces, e.g. quartz.
Corrosiveness: The Ceramics are Anti-Corrosive material to the environment as they are previously in corrosive form. They need high softening temperature.
Recyclability: Ceramics cannot be recycled.
The properties of ceramics are dependent on their micro-structures. They are inorganic, non-metallic and polycrystalline materials. Sometimes diamond and sapphire are speciously included under the term “ceramics”. On the other hand, glass is made of inorganic and non-metallic materials with an amorphous structure. Glass-ceramics are made of small grains and have properties in between those of glass and ceramics.
Applications of Ceramics
- Ceramics have versatile applications from which some are here.
- Ceramics also widely used in the production of lasers.
- Ceramic tiles have covered our roofs and kitchens. They are glazed with various colors and printed according to choice. They are tough and easy to wipe clean once glazed which is perfect for use in the kitchen or bathroom!
- Aluminum oxide and clay-based ceramics are used as high voltage insulators.
- In watchmaking industry, high-tech ceramic is used to make watch cases. Watchmakers prize the material for its light weight, scratch resistance, longevity and smooth feel.
- Ceramic knife’s blades can remain sharp for much longer than a steel knife’s blade, but it will be more brittle and prone to crack.
- Ceramics made water tanks are in your homes, as they are long lasting and will not be affected by environment.
- Silicon carbide (ceramic) is being used as a heating element for electrical furnaces.
- One of the important uses of ceramics is in Structural tiles, drainage pipes, sanitary, pottery and art ware.
- Majority of crockery and pots are made from ceramic materials. Ceramic knives have also become common, they are one of the hardest knives you can buy yet are extremely lightweight!
- Aluminum oxide etc. are used as semiconductors.
- Several ceramics are being used as dielectrics, piezoelectric and ferroelectric materials as well as capacitors and transducers.
- Toughened ceramic is used in hip replacements and is designed to be porous so that it can stimulate natural bone growth around the artificial joint. You will also find ceramic fillings for your teeth where the ceramic is chemically bonded to your tooth making it extremely strong.
- There are several ceramics used as ferri-magnetic materials and they are termed as ferrites.